Anyone here working on any interesting building projects?

[Lucas Durand]

I'm into "green" building - energy efficient design and construction and I thought I'd open a thread for people to share information on the subject.

[Lucas Durand]

Are there any forum members here with Passivhaus experience?
In particular I am very interested in design and building technique used in Europe (as it differs greatly from here in North America).

Though I don't buy into the hassle of official certification, I do believe the Passivhaus folks have the right angle - conservation first, "gee-wizardry" second.

I have been working on my own project, partly inspired by the PH standard, which I have been detailing here:
http://ourhouseuponmoosehill.blogspot.ca/

[Neven]

Hi, Lucas. Yes, I'm planning on building a Passivhaus (non-certified). According to my calculations we - my wife, daughter and I - will need about 4000 to 4500 kWh a year to cover all our residential energy needs. I'm still in doubt about a couple of things, having multiple options for things like heating and hot water, and also planning our PV solar array. I have some ideas for ventilation with heat recovery, combined with a glasshouse, etc, etc.

I'm a bit busy right now, but I'll try and post some of my ideas, and some images of our design in the next day or two. I read your blog from back to front a while ago and found it very inspiring.

[Lucas Durand]

Hi Neven.
It's always good to hear that someone has gotten something useful from my blog.
I've been taking a break from posting new material to it lately, but I hope to get back to it again soon.

Certainly there is plenty to think about when planning for a new house...
Particularly true if you are contemplating incorporating the types of systems you mention.
When I was still in the planning/design phase, I found it helpful to define certain themes that I wanted to stick to.
The main theme I stuck to was resilience.

I look forward to seeing what your plans are, but don't worry about making a priority out of it.
I know what it's like to have to constantly juggle responsibilities with a wide array of personal interests.

[gfwellman]

Lucas, I went to your (web) site yesterday and I'm wowed - congratulations on such an amazing project.  I have two questions so far.
1.  Can you elaborate a bit on how the inner and outer stud walls are joined?  Do the floor and ceiling joists cross both?  What are the plywood gussets and are they vertical or horizontal?
2.  It sounds like you put insulation in the "between" space as well as in each stud wall.  Did I understand that correctly?
Thanks!

[Lucas Durand]

Hi gfwellman,
Thanks, it's been a long time in the planning and the making.

To answer your questions:
The inner and outer walls are joined together by the gussets and by a 3/4" plywood sill plate at the bottom.
The gussets themselves were cut from 3/4" plywood.
The "between" space was made 3 1/2" deep so that "off-the-shelf" 2x4 insulation could be fit in there (in addition to the insulation that goes between the inner and outer studs).
Total thermal resistance for the assembly is ~R42.

[Neven]

Okay, I'm going to try and write a couple of comments that explain my plans for the house we're going to build this summer. This is basically how the house will look from the outside:



And from the inside:



Hauptgebäude stands for 'main building', and Zubau is the extension. The main building has an area of 85-90 square metres (900 square feet) and will be insulated to the Passivhaus-standard, the extension and the attic will be insulated as well, but not as good as the main building.

The outer wall of the main building will be approximately 40 cm thick (16 inches). From outside to inside: 2-3 cm lime plaster, 2.4 cm rough wooden planks, 30 cm insulation (probably cellulose) between wooden beams or T-joists, 1.5-2 cm Oriented Strand Board, 2-3 cm loam plaster.

The insulation value of elements is called U-Wert in German and it says something about the thermal transmission of an element. The Passivhaus standard requires an U-Wert of 0.15 W/(m²·K) or lower. The outer walls of our house have an U-Wert of 0.11-0.12 W/(m²·K).

In the US they use the R-value, right? In that case our walls have an R-Value of around 8-9.

The windows will of course be triple-glazed.

In order to save on the amount of concrete used (very energy-intensive), the house will be built on a strip foundation. Basically a 40 cm wooden and insulated slab, if that's the right word, on top of the strips.

In the next comments I will go into how we plan to heat our home and water, the heat recovery ventilation system, and other measures such as solar panels.

[ghoti]

Imperial units are never as straight forward as SI units. Though R is 1/conductance the imperial units are of course more arcane. In North America R units are  h·ft²·°F/Btu. Thus your planned wall insulation is a much more impressive R of 45 to 51!

That about what I upgraded my attic insulation to a few years ago so it is really impressive for walls.

Another suggestion that immediately came to mind relates to skylights. In my personal experience the quality of life in my homes has been massively improved by having skylights in the south facing roof. So unless you feel to absolutely must cover every square meter of southern roof with PV panels consider some skylighting. If 100% is taken up by PV then consider skylights on some of the north facing roof. The natural lighting provides a wonderful boost to a person's mental attitude.

[Bob Wallace]

I've got to agree re: skylights.  The make a massive difference to the livability of rooms under the roof.

You can add movable insulating covers for heat trapping on cold nights.

--

Have you considered papercrete?  A designer/builder friend of mine has built a couple of structures and it seems to work wonderfully as an insulating structure.

[Lynn Shwadchuck]

Outdoor earth oven

A way to make life without air conditioning more comfortable while cooking from scratch from low-footprint basic supplies (e.g. bread). I understand that the wood is used very efficiently for maximum heat retention. I bought the book, Build Your Own Earth Oven, and we plan to make one this summer.

Lots of inspiring photos here.

http://inspirationgreen.com/outdoor-earth-ovens.html

[Lucas Durand]

Neven,
Looks like you've been spending some time on Google Sketchup...
Sketchup is a great modeling tool.
Once you have a basic model of your house, you can turn on "shadows" to tweak your window layout and roof overhangs for best passive solar performance.
I used sketchup to model my own roof overhangs this way and they turned out great.

Looks like you have a small living space in the attic, so you will need construction details that create a continuous air barrier between the main floor and the attic living space.
Have you considered what kind of air sealing strategy you'll be using?


Good idea to minimize your use of concrete - energy inensive, CO2 intensive and expensive.

[Neven]

Very nice, Lynn! I tinkered a bit with the shadows function in Sketchup, but somehow prefer doing it on paper with my protractor and set square. :-)

Wrt skylights: They're very nice, we have them in our current rental apartment. Downside is that glass in a roof means increased loss of thermal energy, but this might not be a problem upstairs as it isn't part of the main, well-insulated space downstairs. We will probably make one big space upstairs, with just a small bathroom and a small room for the PV inverter and battery system. This means that there is also light coming through the side walls.

I'm thinking about making a so-called dormer window, unless it creates shadows that could bother the solar panels. In that case I'd make a recess in the roof.

Basically three possibilities (in order of current preference):

1. Dormer window.
2. Recess.
3. Skylights.

[Neven]

Have you considered what kind of air sealing strategy you'll be using?

Forgot to answer this question. Sorry, Lynn.

We'll be using OSB on the inside of the house to make the house airtight, together with special duct tape to seal off any openings. I believe Lucas has done something similar with his house. In fact, I saw that duct tape first on his blog. I believed gluing the OSB boards together, would be enough, but it isn't.

Speaking of air: In a house that is so well insulated and airtight as a Passivhaus you don't have any drafts that let fresh air in. If you do it by opening your windows, you let all the warm air out, which destroys the idea of Passivhaus (hardly any active heating, mostly passive by catching sunlight). If you keep your windows closed, you choke.

And so an integral part of the Passivhaus concept is the heat recovery ventilation system. These machines take fresh outside air and before getting blowing into your house, this air receives up to 95% of the heat (and humidity) of the air that is ventilated out of the house. See the Wiki entry for more details.

You basically have two HRV systems, either centralized or decentralized. The first is more common, but has some serious downsides IMO. This next part is something I've written on a different forum a couple of months ago:

A central ventilation system transports air to all rooms via ducts. I'm not a fan of central ventilation systems, because they're expensive and noisy. After installing them there are extra costs for maintenance (electronics) and the bi-yearly exchange of expensive filters. Installing ducts throughout the entire house is also a lot of extra work, and has to be done perfectly or you get problems with noise and/or bacteria.

And so I prefer a decentral solution, this one to be precise: Ökolüfter. The Ökolüfter (translates as 'Ecovent') is a German decentral heat recovery ventilation system, meaning there are no ducts. What I like about the Ökolüfter is its simplicity. It can deliver plenty of air (80-200 m3/hr), but uses very little energy (4-31 W), is relatively quiet (22-42 dBA), recovers moisture as well (very important in winter), has no filters or electronics, just two high-quality Papst fans. It's small, simple and 3-4 cheaper and easier to install than central ventilation systems. To me this is the picoPSU of ventilation systems (watch this video to see how it works, it's pretty nifty).

The downside of decentral ventilation systems is that there aren't any ducts to transport the air to other rooms. However, we need fresh air in our bedrooms at night, but can't open any windows. I want to compensate that by building a so-called Ringlüftung, which roughly translates to 'air circuit' or 'ventilation circuit'. Air is transported from room to room by using computer fans and short ducts. In our case it would look something like this:



The air enters the house via the Ökolüfter in the lower right or southeast corner of the building (where the kitchen is). Passing three ducts and fans it gets transported all around the house in a clockwise direction. Three important aspects:

1) Ventilation

There are several numbers out there describing how much CFM or m3/hr there needs to be to prevent air in a home from going stale. For instance 22-36 m3/hr per person is recommended. We're a family of three, so 80-120 m3/h should be enough. Another way to look at it is by calculating air changes per hour, in other words: how many times per hour does the air in a home need to be changed? According to the German Passivhaus Institute 30-40% of the air needs to be changed every hour. Our house will be 85-90 square metres, with a 2.5 metre high ceiling, so the volume will be approximately 200-225 m3 -> 40% of 225 m3 every hour amounts to 90 m3/hr.

Put simply, the three computer fans that circulate the air through the house must be able to deliver around 100 m3/hr (or 59 CFM). Perhaps even less, as the two bedrooms have a total volume of 50 m3, and 40% of 50 m3 every hour is just 20 m3/hr (or 12 CFM). But I'm not sure about this.

2) Noise

Of course, the fans need to be quiet! According to experts noise in bedrooms must not exceed 23 dBA. Of course, the fans will be high up, in the corner of the room, at least 3-4 metres away, but I'm very sensitive to noises. The fans will also be hooked up to the Scythe Kaze Server fan controller, for power, rpm readings and fan control.

More on fans after 3).

3) Acoustics

There will be air ducts between rooms (two will be approximately 1.5 metres long, the last one twice that), and I'm not sure if sounds get carried from one room to the next. It's possible to install duct silencers/mufflers to dampen the sounds, if that would help (have no idea). I could build them myself, but they're not very expensive.

---

So that's the idea basically. I went to present my idea on the Silent PC Review Forums because there are a lot of silent fan and duct experts there. You can read the rest of the discussion there. It didn't lead to anything conclusive.

The way I see it now, there are two options:

1) Use the (muffled) ducts to get the fresh air circulating around the house, or
2) Make a lot of smaller holes in walls, with a sound insulating board 2-3 cm (1 inch) in front of it.

A third option would be to just leave the bedroom doors open. According to the company that sells the Ökolüfter the air will get circulated all over the house because of temperature differences. Although this is true, I'm not sure if that would do the trick. And I really want fresh air around me. It's amazing how fast CO2 can build up in a room or house, and make you less concentrated and get tired faster.

Now this idea of a Ringlüftung hasn't been done often and you can't find much info on the Internet, but I'm reasonably certain it could work noiselessly. I have some experience with building low power and completely silent computers in wooden casings (I tried setting up a small company a few years ago building the damn things), and houses and computers are pretty similar in a couple of ways.

But I have an even more risky/crazy idea that I will try to explain in the following comment. It involves the ventilation system and CO2.

[Neven]

BTW I hope you don't mind these long-winding posts, and feel free to shoot holes.

----

Because we plan on doing a lot of gardening, we somehow want to incorporate a greenhouse into our design. Although it isn't too difficult to add one later, we prefer to do it now. Attaching a greenhouse to a house has a couple of advantages. The greenhouse can function as an extra insulation layer when placed on the south side of the house, and the outer wall of the house in return insulates the greenhouse on the north and functions as a thermal energy storage element.

In the first image I posted we have the greenhouse on the eastern side of the house, but are now seriously considering to put it on the south side, to cut down costs for instance.

The second version of the house looks something like this:



The glass of the greenhouse would be at an angle of 45°, same as the roof. 50 to 60° is best for catching sunlight during winter, but 45° would be easier for me to build and aesthetically more appealing I believe. The greenhouse will be a wooden construction with an area of around 20 square metres (200 square feet) which should be plenty for a start. We're planning on using plexiglass, because it's lightweight, pretty eco-friendly, long-lasting (doesn't turn yellow) and it lets a lot of sunshine and UV through, which is beneficial to plant growth.

What is also beneficial to plants, as our fake skeptic friends keep telling us, is CO2. This is where my other crazy/risky idea comes in: I want to combine the Ökolüfter and the greenhouse in such a way that used air from the building ends up in the greenhouse, thus increasing the CO2 concentration.

Here is a profile sketch of how the greenhouse looks with the duct of the Ökolüfter's intake running through the greenhouse, but the exhaust connecting straight to the greenhouse:



I have to go now, but I'll continue tomorrow with some numbers and advantages and problems I'm seeing but can't judge properly.

[TerryM]

Neven

Why the aversion to filtration?

Static electric filters remove particles that otherwise end up in your lungs. They can be cleaned as opposed to being replaced, permit good air flow & have some small effect on reducing sound transmission.  If you ever have the misfortune to have to clean an evaporator coil or even a fan squirrel cage in a system that has been run for even a short period without filtration you'd need no convincing. 

Convection currents, particularly under closed doors, pick up large mounts of nasty stuff that you really want to filter out of the air, particularly in a very air tight home.

The greenhouse on the south facing wall can pump large amounts of heated air through the house simply by venting it in near the peak & allowing return air feeds at floor level. I'd probably want shutters on the vents to keep the home livable on sunny days. I've seen designs that allowed the greenhouse to vent outside during the summer while drawing cool air through the house from a basement feature. I realize you're not building a basement, but if you consider the greenhouse as a heater that requires no fans for air circulation it may help with your design.

Terry

[gfwellman]

I think that's a great idea Neven.  Also what Terry said - using the greenhouse as solar heater in winter and convective draw in summer.

I've been looking into ways to improve the sealing of my existing, conventional North American home.  However, if I were to get the sealing good enough, I too would want an HRV (aka ERV).  In my case there is already central HVAC as well as dedicated "out" ventilation fans in the obvious places (bathrooms, over the range, etc).  Given limitations of what I can access, my plan would be to add an HRV that draws from 2 or 3 of the accessible vents on the top floor while feeding the fresh air into the top of the central HVAC return system.  Other vents (like the one over the range) would be left alone (almost never used anyway).

One significant problem?  This is North America.  I went to Home Depot hoping to get some information on HRVs.  Nobody had ever heard of them.  Yeah, I can find them on the net, but I was hoping for some on-the-ground knowledge of which ones work out well, noise levels, efficiency, etc.  Anyway, it's not a super high priority right now, but eventually I'll get around to it.

[ghoti]

Seems a bit surprising that Home depot didn't have any HRVs. HRVs are now a code requirement for new residential buildings here in Ontario. If you are building a tightly sealed home you definitely require active ventilation and if you want to control heating/cooling requirements then HRV makes sense.

Greenhouses require massive ventilation for the portion of the year where there are plenty of hours of sun. I don't know the details of your location but I'd expect venting will be required at least 6 months of the year.

[Lucas Durand]

Neven,
Seems like you may have confused Lynn and I ;-)

Looks like you've been putting a lot of thought into your plans - good for you!
The planning stage isn't something that should be rushed.

If you don't mind, I have a couple of comments:
1. ***
If you are planning to use taped OSB as an air barrier, be careful to make sure that the tape will stick properly to it.
Maybe the OSB you have over there is a little different, but here OSB has a "rough" side and a "smooth" side and tape will only stick to the "smooth" side.
The tapes that are made for this purpose have a very aggressive adhesive, but the adhesive grabs the fine particles in the "rough" side of OSB, which seperate easily from the panel.

Edit to say: A primer may also help the tape to stick if the substrate is difficult.

There are some high quality tapes that may be available in your area from Siga and Pro Clima.

2. ***
Cool fan unit!
You don't see a lot of products like the Okolufter over here unless they're imported.
Does it have built in heat recovery?

If not, you might consider something like this unit from Lunos.
It uses a single fan that reverses direction periodically and a ceramic core for heat recovery.

[ivica]

Neven,
I like, specialy, your idea to have a greenhouse. :thumbs-up:
Something to share, "Greenhouse growing" board:
http://citrus.forumup.org/viewforum.php?f=15&mforum=citrus

A potted lemon tree could be nice addition there :-)

[Neven]

Neven

Why the aversion to filtration?

Terry, I'm definitely not averse to filtration, quite the contrary. What I don't like is that most central ventilation systems I have looked at, require a filter change twice a year. That's two times two filters a year. I don't find that sustainable, and it costs around $100. The Ökolüfter also has a filtration system - albeit not as good as special filters - that can be detached and washed easily.

About 90% of energy and humidity are recovered by the Ökolüfter.

Neven,
Seems like you may have confused Lynn and I ;-)

Indeed, I did. Apologies. And no need for you to look at your own blog to see the details. 

Looks like you've been putting a lot of thought into your plans - good for you!
The planning stage isn't something that should be rushed.

Still not finished planning wrt ventilation, heating and hot water. We're going to get some offers from a couple of companies before the end of the month, so I hope to be done by then.

Thanks for the OSB tip. There's a cool OSB product in Europe called OSB AIRSTOPFINISH ECO with a special cellulose-based foil that improves airtightness even more, but I have a feeling it's going to be very expensive.

I knew about the concept with the ceramic core, where the air gets blown out for a couple of minutes, heating the ceramic core, and then blown in again. The problem for me is that they can only deliver 38 m3/h at the most (and are said to be loud) which means I would need at least three. But this might become an option nonetheless if for some reason or other it's not working out with the Ökolüfter.

Greenhouses require massive ventilation for the portion of the year where there are plenty of hours of sun. I don't know the details of your location but I'd expect venting will be required at least 6 months of the year.

It can get pretty hot and sunny here in summer, southeast of the Alps, so proper ventilation and shutters are very important.

I'll post more details when I have it all worked out. I like the model from the Passive Solar Greenhouse Project a lot. This website has lots of info and numbers. I plan on building that greenhouse, but instead of free standing it will be attached to the house. Greenhouses are a fascinating subject. You have to make sure you use the right (plexi)glass, get the ventilation right, create enough thermal energy storage. If you do all of that right, you can grow stuff in there almost all year round. We also plan on building root cellar next year or the year after that. Another fascinating subject.

[Neven]

Now for those pros and cons of combining the home ventilation system with the greenhouse. First the pros:

- CO₂ is plant food! According to the German Hortipendium wiki plants do better in an atmosphere (in a greenhouse of course) that contains 600 to 1600 ppm, depending on the plants. Vegetables like more.

So here's what I have calculated on the back of an envelope: On average people breathe out 16 litres of CO₂ every hour. We are a family of three, our daughter is 8 years old, so we make that 40 litres per hour. The greenhouse has a volume of around 80.000 litres of air, which means that every hour 0.0002% of CO₂ is added to the greenhouse. 0.0002% is 200 ppm. So in theory the CO₂ concentration in the greenhouse should be elevated considerably over the standard 300-400 ppm.
- The Ökolüfter requires a hole of about 38 cm (15 inches) in the wall, and this in essence is a thermal bridge. But less so with a greenhouse in front of the wall.
- At very low temperatures (-20 °C) condensate could get frozen and the ventilation system would then need to be shut off. The greenhouse could prevent that, although I have to say this situation would occur very rarely in this part of Austria.
- Perhaps the greenhouse pre-heats some of the air that enters the house through the 2-2.5 metre (6-8 feet) long duct.

And now the cons that could be a deal breaker:

- With the exhaust blowing air into the greenhouse, could pressure differences between greenhouse and home cause problems?
- Will the intake fan function properly when the air goes through that duct?
- 90% of the air that exits is recovered, which means that if it's 0 °C outside, and 20°C in the house, the exiting air has a temp of 2 °C. Maybe not all that great for the greenhouse.

I think basically that I need to have the possibility to either have the exhaust blow CO₂ rich air into the greenhouse, or when the cons outweigh that pro, have it blow directly outside. This could work in fall and spring, but not in winter. Hmmm....

---

More on heating and hot water tomorrow. Please shoot holes. The inventor of the ventilation system is going to advise me, but is extremely busy atm.

[ghoti]

I spent my PhD measuring photosynthesis in plants and I'd say don't focus your house/greenhouse ventilation plans on CO₂ management. There are plenty of CO₂ sources within the greenhouse to more than suffice. For example humus rich soil with live bacteria will dump plenty of CO₂ into the air.

Instead focus on your family's comfort and well being when you design the ventilation. The plants will be just fine. Remember that the current 400ppm is already double what they evolved to live with.

[TerryM]

Neven

Sorry about the misunderstanding of your position on filtration. Electrostatic filters are washable with a >10 year life. They filter to just below hepa standards without interfering too much with air flow. I've used them in everything from my home to large commercial installations & for anything other than hospitals they're more than adequate. Don't buy anything that requires filter replacements.

The air pressure differences you mention between the greenhouse and the home can be used in place of fans to keep the air moving, Static stratified air has to be avoided & convection currents can be your friend - if designed for. Nothing is quieter than airflow that isn't induced by a fan.

Do you have wet bulb/ dry bulb figures for your area? Sometimes humidity is more important than raw temperature when it comes to livability.

Your root cellar might prove a good source of cool air for most of the year using convective currents from the greenhouse to draw this air up. Air vented into the house from the top of the greenhouse will necessitate dissipating the heat most of the year & heavy stone structures in the greenhouse can store the heat through cold nights.

Most of my work was in coastal southern California and the Mojave Desert in Nevada many years ago so cooling was usually a bigger concern than heating. My work all involved retrofits and was mainly concerned with large commercial structures. A friend had a huge passive home in Utah that heated and cooled using a greenhouse very similar to yours so I know it's possible to design a system without fans.

I think Ghoti is right about CO2 in the greenhouse. You have a large source of thermal energy there that can be used for heating the house & hopefully the make up air won't be much different than ambient.

Lucas's emphasis on planning bears repeating. Nothing is worse than trying to adjust things part way through the building phase, unless it's having to change things after they're already built.

I'll be following your project with interest & hope you don't mind if I pop in with comments from time to time.

Terry

[Neven]

I spent my PhD measuring photosynthesis in plants and I'd say don't focus your house/greenhouse ventilation plans on CO₂ management. There are plenty of CO₂ sources within the greenhouse to more than suffice. For example humus rich soil with live bacteria will dump plenty of CO₂ into the air.

Instead focus on your family's comfort and well being when you design the ventilation. The plants will be just fine. Remember that the current 400ppm is already double what they evolved to live with.

Thanks, Ghoti. After writing down all the cons I realized that I tend more towards a greenhouse without the complicated combination of ventilation system and greenhouse.

If I want the plants to have more CO₂ I guess I'll have to go and sleep in the greenhouse. During the day, of course, when it's sunny, because that's when they need it most. 

But I'll still wait and see what the inventor of the ventilation system says, although I think he'll advise me not to do it.

The air pressure differences you mention between the greenhouse and the home can be used in place of fans to keep the air moving, Static stratified air has to be avoided & convection currents can be your friend - if designed for. Nothing is quieter than airflow that isn't induced by a fan.

I totally agree, except that this wouldn't work for a Passivhaus as the greenhouse would have to be made airtight as well.

Do you have wet bulb/ dry bulb figures for your area? Sometimes humidity is more important than raw temperature when it comes to livability.

I don't believe I have. Basically summers can be pretty hot around here, winters can be cold, but not as cold as most other parts of Austria (Alps). It can be humid in fall and spring with lots of fog in the morning and at night.

Your root cellar might prove a good source of cool air for most of the year using convective currents from the greenhouse to draw this air up. Air vented into the house from the top of the greenhouse will necessitate dissipating the heat most of the year & heavy stone structures in the greenhouse can store the heat through cold nights.

The root cellar won't be under the house. We thought about having one built together with the foundation, but to save money we're going to leave that one for later, and probably build one ourselves not too far from the house.

I think Ghoti is right about CO2 in the greenhouse. You have a large source of thermal energy there that can be used for heating the house & hopefully the make up air won't be much different than ambient.

Yes, another reason not to combine the ventilation system with the greenhouse, as you couldn't open the door between home and greenhouse, because of the shortcircuiting of air. If they are not combined, you can open the door to either let warm air caught in the greenhouse into your home, or let warm air from your home into the greenhouse to save the salads from freezing.

I know there is only a small chance the combination works AND makes sense, but want to think it through anyway, while I still can. When the house is built, you switch from planning to living with your mistakes. 

I'll be following your project with interest & hope you don't mind if I pop in with comments from time to time.

Gladly, Terry! Tomorrow I will try and explain how I want to heat air and water. I have a simple plan and a complex one. And then after that it's time for the solar panel array, where the planning is also far from done.

[TerryM]

I'll be taking a group through North House within the next few months. It's an 800 sq ft solar home that produces more energy than it uses & incorporates lots of new technologies.  After touring the US it's permanent home is only  few kilometers from where I live, so it will be interesting to see how it holds up over the years.

What expertise I have was in designing for very hot very dry climates, so seeing what technical solutions the students have come up with to build for more northern climes should be interesting. They are combining both passive and active solar systems & apparently produce enough energy to power a nearby hundred year old farmhouse!

I haven't been able to locate any technical specs yet, but hopefully after the tour I'll be able to post about what I've learned.

http://www.oaa.on.ca/professional+resources/sustainable+design/the+north+house

Terry

[Lucas Durand]

Terry,
I would be interested to hear what you have to say after you visit.
These houses usually have some pretty innovative stuff going on...
I'd like to know more about what the project house cost - the website you linked to seemed to hint at a project budget somewhere north of $2.1 million (for an 800 sq ft house!).

[TerryM]

Terry,
I would be interested to hear what you have to say after you visit.
These houses usually have some pretty innovative stuff going on...
I'd like to know more about what the project house cost - the website you linked to seemed to hint at a project budget somewhere north of $2.1 million (for an 800 sq ft house!).

I think the quoted figure included things not applicable for a home that would actually be lived in such as transportation, set up & tear down.

This link may have more information, particularly after clicking on"our design". I'll get some up to date figures for what it would cost to replicate when I visit. I doubt if anyone would want to duplicate all the features, but there may be some things that could be incorporated into new or retrofitted homes.

http://www.team-north.com/index.php

I think one of the new buildings at the Balsillie School of International Affairs is using some of the technology that North House developed & I'll try to find out more when I'm there within the next few weeks.

Your project is interesting. I'm passingly familiar with the area you're in & may be out that way next year. Yours is a much larger home than anything that the wife and I would require & in fact we've found ourselves quite content in a condo where someone else mows the grass and shovels the snow. Will you be needing AC in the summer or are ambient temperatures such that it won't be required?

At some point green apartment buildings will be on the market. There was one attempted in Las Vegas about 25 years ago but it was a disaster that I was peripherally involved with when the systems began to fail. One of their problems was running radiant heating/cooling through the units without a means to isolate one unit without shutting down a whole building. They'd actually neglected to put shut offs on each building so the whole complex had to be shut down to repair a small leak. Another thing they missed was taking into account how sensitive PVC and ABS are to thermal expansion. A pipe may only change diameter by a small amount but the length can change significantly. Solar is still new enough that building standards haven't been written yet in many locations & the architect has to remember to plan for repairs when systems fail.

Cheers
Terry

[Lucas Durand]

I doubt if anyone would want to duplicate all the features, but there may be some things that could be incorporated into new or retrofitted homes.

Terry,
Yeah, I sometimes get a bit of a chuckle out of some of the features in these houses.
It's good to try things out, but I have a hard time believing that we'll ever see the day when adding salt hydrates as a thermal mass will be standard practice.

I'm passingly familiar with the area you're in & may be out that way next year. Yours is a much larger home than anything that the wife and I would require & in fact we've found ourselves quite content in a condo where someone else mows the grass and shovels the snow. Will you be needing AC in the summer or are ambient temperatures such that it won't be required?

If you do end up passing through, feel free to drop by and have a look.
This house I'm building is larger than what I wanted as well, but as it turns out, it may work out well in the end as we will now have room for my in-laws.

I won't be putting in any A/C...
Most new construction in the area gets A/C, but I'm not sure it's really required.
One of my design goals with this house has been to keep the amount of active systems to the bare minimum.

[Neven]

That North House is pretty cool, Terry! There are tons of similar projects. Here in Austria they built a big strawbale passive house with loads of info and data on experiments they ran with ecological building materials, but somehow I never got around to go and visit it.

By the way, if someone says we can't discuss passive houses on an Arctic Sea Ice Forum, then here's something I read just 1 minute ago to dispute it:

The first fully functioning Passive House was actually a polar ship and not a house: the Fram of Fridtjof Nansen (1883).

He writes: ”… The sides of the ship were lined with tarred felt, then came a space with cork padding, next a deal panelling, then a thick layer of felt, next air-tight linoleum, and last of all an inner panelling. The ceiling of the saloon and cabins . . . gave a total thickness of about 15 inches. …The skylight which was most exposed to the cold was protected by three panes of glass one within the other, and in various other ways. … The Fram is a comfortable abode. Whether the thermometer stands at 22° above zero or at 22° below it, we have no fire in the stove. The ventilation is excellent, especially since we rigged up the air sail, which sends a whole winter‘s cold in through the ventilator; yet in spite of this we sit here warm and comfortable, with only a lamp burning. I am thinking of having the stove removed altogether; it is only in the way.“
(from Nansen: “Farthest North”, Brockhaus, 1897))

Is that Nansen the coolest guy who ever lived or what?!

---

Okay, so I want to explain a bit about how I want to heat the building and water. I find it extremely difficult to get all the criteria (sustainability, ecology, costs, proper dimensions, personal wishes) aligned, so maybe you could help me a bit. I'm also active on some German forums, but no one has been able to give me the advice I need. Not that I want a particular piece of advice because I already have my mind up (I keep changing it anyway). I seem to want to do everything the unconventional way, and so general knowledge is low.

Basically there are two options.

The first one is that I heat my air with 700-1000 Watts of infrared heating (like for instance this one), and my water with a simple 80-100 litre, 1-2 kW electric boiler. I'm planning on installing 4-5 kWp of solar panels on my roof, probably combined with 4-5 kWh of battery storage to increase the self-use of PV power from 30% to 70% (more on that later).

The other option is that I heat my air AND water with a loam or clay wood oven, that has a water heat exchanger built into it, looking something like this:



It basically works the same as with a solar hot water system. The water that is heated, is pumped via a circuit through a 300 litre hot water storage tank where it preheats the water used later on in the electric boiler.

I have written down all the pros and cons of both options:

Pros option 1 (infra red heating and electric boiler):

• Relatively cheap and simple
• Doesn't take up a lot of space
• Easy to adjust

Cons option 1:

• High electricity consumption and costs during winter (because less PV power)
• Electricity costs are sure to rise in years to come
• Winter electricity is mostly produced with fossil fuels (even here in Austria where they have a lot of hydro)

Pros option 2 (loam/clay stove with water heat exchanger, hot water storage tank)

• Up to 90% energy independent with a minimum of wood used
• Lower running costs
• Cozy fireplace that my Austrian friends will love (they're nuts about burning wood)
• Which means the resale price goes up (if ever needed)

Cons option 2:

• A couple of thousand euros more expensive than option 1, pays off only after 20-25 years (with current electricity prices)
• Takes up more space
• More difficult to control, could lead overheating of house
• Chimney is a thermal bridge
• Produces particulate matter (I'm not a fan of burning things in general)

So there you have it. I'd like to go for option 2, but only if I'm reasonably sure it'll work. Luckily there's a good loam oven builder living nearby who is going to put on all the loam plaster on our inner walls, but he's on a holiday for another week or so. I will discuss it with him as soon as he's back. He knows quite a bit about unconvential building stuff.

I would like it to work like this: You put in 2-3 kg of wood twice a winter day. Wood carries an energy of around 4 kWh (depending on what kind of wood). This means 4-6 kg is worth 16-24 kWh, but because the oven has an energy conversion efficiency of 80% you get around 13-19 kWh of power. If 30% of that heat goes into heating the living room, you get around 4-6 kWh that is slowly emitted in about 20 hours (2 x 10 hours) because of the high thermal mass of the loam, so we're talking a power rating of 200-300 W. A passive house isn't 'allowed' to have a heating power rating of more than 10 W/m², so I'm well inside that envelope. With the infra red heating I calculated about 4 hours a day of 750 W = 3 kWh.

70% of the thermal energy, 9-13 kWh is used to heat the 300 litres of water in the tank. It takes 0.00116 kWh to increase the temperature of 1 litre of water by 1 °C. So throwing 9-13 kWh into 300 litres of water, will raise the water temperature by 25-37 °C. As we will only use 80-100 litres of that water a day (some of it will get radiated out of the tank) the water should be warm enough within 1-2 days. If not an electric water heater in the tank and/or electric boiler will further heat the water. You can do that too if outside temperatures are not low enough to use the oven, as this will probably mean the solar panels are producing some more energy than on cold and cloudy days.

This would basically mean we 're 90% or more energy independent. That's why in theory option 2 really appeals to me. In theory. Lots of pitfalls, I expect. I'll see what the loam oven builder thinks about it, but if any of you guys have experience with this or ideas, I'd love to hear them. In the next couple of days I'll give you my thoughts on PV arrays and especially battery storage systems (not that I know much about them) because there's a lot going on in that sector.

Hope I don't bore you too much with my ramblings! 

[OldLeatherneck]

Passive Solar Water Heating





Neven,

I don't know if you've looked at solar water heating yet, however, I just did a Google search and found hundreds of images (I randomly selected two of them).  Since I'm not a construction engineer, I have no idea which designs might be applicable for your situation or the costs involved.

I just remember how hot water, in the garden hose, gets during the heat of the day, in the Arizona desert.

[TerryM]

Neven

Just a paragraph or 2 at the moment.

The first style of solar water preheater in OldL's is the form I'm most familiar with. I'd recommend it because it doesn't require a circulating pump which adds an unnecessary complication to an otherwise simple system. Even if all you did was to run a hundred feet or so of incoming water pipe through the highest peak of your greenhouse you'd be preheating the water going into your electric heater considerably.

I can't find a reference for a loam wood burning stove anywhere, but it sounds interesting.

I'm sure your loam wood burner guy is aware of all this but fire places aren't generally great for heating an enclosed space. Makeup air is required to keep the fire burning & unless provision is made to bring outside air for the fire you end up taking warmed air from the room to feed the fire - then blow it out through the chimney. A stove bringing in ambient air from outside will work & the built in water heater should radiate plenty of heat. - good in the winter but perhaps not during the rest of the year.

I've never seen a radiant heater similar to the one you linked to. In California it's actually illegal to burn electricity for space heating because it's so inefficient.(I think small portable units are exempt. ) A small, <1 ton heat pump with strip heat kicking in when ambient temperatures are below about 8c might prove adequate particularly if the outside coil was drawing heat from the greenhouse. In summer if AC should be required the condenser can be fed and exhausted through movable vents leading outside the greenhouse. Units similar to this are available here for <$200 and if the strip heaters don't kick automatically the modification can be built by anyone with basic electrical skills.

Final thought for the night. Have you considered heat pipes to utilize your greenhouse heat. Not sure of availability in Europe but I'd think a commercial HVAC supplier might have a stock. No moving parts and totally silent!

Terry

[Neven]

For me solar water heating was a sine qua non, also because it is heavily subsidized here. In fact, if you want a general home subsidy you will only get it if you install a solar water heating system! But when I looked into it, I saw there were some downsides to it as well. The biggest downside, as with all solar stuff, is that there's little of it during winter and during summer there's too much of it. After having looked deeper into it, I figured that putting 1 kWp of PV extra on my roof to feed an electric boiler would be cheaper and much less of a hassle that solar water heating. No plumbing, no pumps, no big panels on the roof, all of which can fail.

OK, now I'm proposing basically the same system with a wood stove, but that's to get me through winter! 

I'm sure your loam wood burner guy is aware of all this but fire places aren't generally great for heating an enclosed space. Makeup air is required to keep the fire burning & unless provision is made to bring outside air for the fire you end up taking warmed air from the room to feed the fire - then blow it out through the chimney.

That's definitely a big no-no in passive houses, also because it causes pressure differences that confuses the ventilation system. The fire place gets a separate air intake, possibly built into the chimney.

A stove bringing in ambient air from outside will work & the built in water heater should radiate plenty of heat. - good in the winter but perhaps not during the rest of the year.

It's just for those 50-100 winter days when it's cloudy (no PV) and cold. The rest of the year and on sunny winter days the 5 kWp of PV solar panels produce more than enough electricity to heat the water.

I've never seen a radiant heater similar to the one you linked to. In California it's actually illegal to burn electricity for space heating because it's so inefficient.

It only makes sense in a passive house, that's for sure. What is interesting, is that it emits infra red radiation that heats up objects rather than air. The objects then emit the heat. One effect of this is that the air temperature can be 2 °C lower and you still feel comfortable.

A small, <1 ton heat pump with strip heat kicking in when ambient temperatures are below about 8c might prove adequate particularly if the outside coil was drawing heat from the greenhouse. In summer if AC should be required the condenser can be fed and exhausted through movable vents leading outside the greenhouse. Units similar to this are available here for <$200 and if the strip heaters don't kick automatically the modification can be built by anyone with basic electrical skills.

To tell the truth, I don't have that much faith in the greenhouse's winter temperatures. We have had an incredible winter over here in (this part and other parts of) Europe where we basically had no Sun for over 60 days. There's a website that logs people's PV performance, and coincidentally the data of a solar panel array in my village are freely available as well. I checked how many days there have been in the past four months that the 5.28 kWp array produced less than 7 kWh a day:

Nov. 22
Dec. 20
Jan. 29
Feb. 21

Total 92

In all other months there are almost never more than 2 days of below 7 kWh production. In January there were 17 days of 0 kWh production a day, but that's probably because someone was too lazy to remove the snow from the panels. 

So I don't expect much from the greenhouse during winter itself, perhaps during the transition periods. In fact, I will probably have to blow in heat from my home occasionally to prevent freezing temps in the greenhouse.

Final thought for the night. Have you considered heat pipes to utilize your greenhouse heat. Not sure of availability in Europe but I'd think a commercial HVAC supplier might have a stock. No moving parts and totally silent!

That sounds like a good idea for summer and perhaps spring. What could I utilize it for?

[TerryM]

Neven


You're far further north than anything I've been involved in. I had no idea you'd be facing 2 months basically without sunlight. I've been in homes totally heated and cooled by greenhouses but they were at much lower latitudes than you're at, even though the temperatures may have been colder due to altitude.


Temps have gotten so out of hand here in Southern Ontario they're growing palm trees on the north shore of lake Erie & the grass has been green on the south lawn of my building every month for the last two years. The biggest greenhouses just south of here are growing hydroponic tomatoes year round & although they went under a few years ago, a series of greenhouses in Dundas were supplying Canada with cactus's of all things.


What we used to do to assure ventilation without ducting was to cut 6" by 12" holes (with grills) into the bottom and the top of connecting rooms as far apart from each other as possible. When one room is cooled (or heated) the cold air drops, flows through to the next room and displaces the warm air into the next room (if heated it works the same way in reverse). As long as there is a heat imbalance the flow continues without need of fans & I've never seen a building where heat was perfectly distributed.


It sounds as though you'll be experiencing much more humid conditions than I'm used to. I've always been afraid of mold in those conditions. Any closet space has to have air flow & you probably will want to evacuate bathroom air with it's humidity and odor as directly as possible, (an alliteratively named fart fan should suffice). I don't recall you planning for a stove hood in the kitchen, it's another place where you may want to think of evacuating some humid air (even though the odors may be more tantalizing.

The second floor, where the heat will all want to migrate to might create problems. If you aren't planning to use it as a living space a well fitted door at the top of the stairs might do, otherwise I think a fairly large fan will be needed. Whenever you're blowing air in a direction it doesn't want to go (like warm air down a stairway) it takes an effort.


The heat pipes are useful whenever you want to bring heat (or cold) from one side of a wall to the other without bringing in any air. In hot climates we used them behind refrigerators to dissipate the heat from the coils or to get rid of heat from laundry rooms that otherwise would get sucked into the cooling system. I'd thought they might be useful to bring in heat from the Greenhouse, but it you fear that it may reach freezing temperatures in winter it probably wouldn't help. They use passive phase change and so are extremely efficient one way heaters (or coolers).


Forgive me for rambling, it's been one of those days.
Terry

[Bob Wallace]

I live in an area in which many people are off grid and heat with wood.  Most of us do all the south-facing windows, heavy insulation stuff but we don't attempt to make our houses air-tight.

The wood stove needs to draw air.  The attitude here is to let the house leak a little and use a bit more wood.  That let's one avoid the heat exchanger stuff and create a supply of fresh air for the occupants.

If you're off the grid it's generally easier to cut some extra wood than make electricity to power a ventilation system during the dark hours.

[Lucas Durand]

The wood stove needs to draw air.  The attitude here is to let the house leak a little and use a bit more wood.  That let's one avoid the heat exchanger stuff and create a supply of fresh air for the occupants.

Bob,
That attitude has been changing in recent years.
The attitude is now "build tight and ventilate right".
And in many jurisdictions, a mechanical ventilation strategy is required by building code.

This approach has the following advantages:
- Enclosure durability: Building forensics has identified air leakage (air transport of water vapour) as a major durability issue in houses that use modern impermeable materials like polyethylene, vinyl wallpaper, rigid foam insulation, etc.
- Indoor air quality: Controlled ventilation results in much better IAQ because the source of fresh air is controlled (and not passing through the dead squirrel in the attic, or past mold in the wall).
- Efficiency: If done correctly, "air-tightness" results in measurable efficiency gains.

My own house will be very tight by modern standards and will be heated primarily with an airtight wood stove.
The stove has its own ducted air supply so that it can breathe, but also to avoid backdrafting when the door is opened under (relative) negative pressure conditions.

[TerryM]

Bob


Can I ask what are you live in? I still have a house in Southern California that has no wall insulation, but heavy attic isolation. The idea was to keep the roof heat out in the summer & keep most of the day's heat in on winter nights while allowing large airflow through the place all year round.


It was built in the mid 50s without AC and a tiny unducted heater. Plenty of large trees provide shade in the winter & allow the sun full access after the leaves fall in winter. Over the years I added a 1 ton AC and a small forced air heater, but it was actually comfortable without the changes and I often had to remind myself to turn on the AC every year to keep the refrigerant oil from settling.


Wonder how many decades will pass before similar designs prove viable in balmy Southern Ontario


Terry

[Neven]

My own house will be very tight by modern standards and will be heated primarily with an airtight wood stove.
The stove has its own ducted air supply so that it can breathe, but also to avoid backdrafting when the door is opened under (relative) negative pressure conditions.

Lucas, how do you plan on heating your water? And will you be installing any PV? I'm sorry, all of this is probably on your blog, but I'd love to hear what tricks you have up your sleeve.

[Lucas Durand]

Neven,
I'm not planning anything too fancy - the simpler the better in my view.

As I mentioned, the primary heating appliance is an airtight woodstove with its own ducted air supply.
Also, the house has been designed to take advantage of passive solar heat gain from the middle of fall to the middle of spring.

For heating domestic hot water, I am using two 4'x8' (~1.2mx2.4m) flat plate solar collectors (similar to those in Old L's photos above) to heat an 80gal (~300l) stainless steel storage tank.
The rest of the solar thermal system is simply a closed loop design that circulates a glycol solution for heat transfer and also to prevent freezing.
A DC pump is wired directly to a small PV panel so that when the sun shines, the pump circulates the glycol solution (no controllers required).
It's actually a very simple system - a fellow up the road from me has been operating a system very similar to this for the last 25 years with the only maintenance being to recycle the glycol solution every few years.
The collectors are angled almost perpendicular to the winter noon sun so that they operate most efficiently in winter and less efficiently in summer.
Solar thermal is generally not as good as PV from a strictly economic perspective, but economics isn't everything and solar thermal has its advantages - particularily in off-grid applications.

I would like to add some PV as budget permits.
Our house will be connected to the grid, but I don't see myself tying my PV system to the grid.
Instead, I will probably have a smaller off-grid PV system dedicated to certain essential household systems - like our well pump.

We also have an attached three season sunroom (like a greenhouse) for seed starting etc.
There is a door directly into the sunroom from the house so I imagine that if there is excess heat in there during the winter, we could just open the door to let some of it in the house.

The overall idea was to give our house the ability to operate in an "off-grid mode".
Presently, a worst case scenario would involve an extended power outage in the winter when the outdoor temperature is down in the vicinity of -20C.
In such circumstances, it can become neccessary to "abandon ship".
However, while operating in "off-grid mode", our house will still provide hot running water and (thanks to all the insulation) will only require a small amount of wood to keep warm (we also live on a large wood lot from which I can sustainably harvest my own wood).

[Lucas Durand]

Neven,
After looking at your "loam oven", I thought you might find these "rocket mass heaters" interesting:
http://www.richsoil.com/rocket-stove-mass-heater.jsp

I want to try to build one when I have some spare time 

Another downside to heating hot water with a stove can be that the thermosyphon can't be shut off if the storage tank reaches maximum temperature/pressure - at which point the tank must be allowed to vent somewhere or else you have (potentially) a large bomb in your house.

[Bob Wallace]

Bob

Can I ask what are you live in?

I'm in Northern California, Humboldt County, and in the mountains.  It's a four season climate with mild summers.  I've no need for AC, just use a fan a small number of days a year. 

I built my house so that the main living space (living room, eating area and kitchen) are protected on the east and north from the coldest and windiest weather by dining room (east) and workshop (north).  I also insulated the ceiling over the living room (under the upstairs bedroom).

The walls are 2x6 for extra insulation, the windows and doors double pane, "low e" with an almost invisible reflective film and argon gas. 

The floor is insulated and "hosed" for radiant heating if I ever decide to add it. 

This gives me a tightly insulated 600 square foot box.  Doubly protected on top by both ceiling and roof insulation.  The rest of the house (bedrooms, shop, dining room) are outside the heated box.

I've closed the bubble reasonably tight but avoided the super tight -  no air can possibly leak in -approach.  I wanted to avoid have an active (requiring electricity) ventilation system.  I'd rather carry in a little extra wood than run my generator on a cold winter night to keep the air fresh.

I've got plenty of south facing windows (and a well-designed overhang).  My house is rarely/never under 50 degrees when I get up in the morning.  It's usually 55 and if the Sun is going to shine I don't bother lighting a fire.  A hot cup of coffee and the sunshine spilling in through the French doors to the dining room are enough to hold me over until the Sun starts warming the living room.

What really works on cold, cloudy mornings is a lot of "small stuff" to get a quick, hot fire going.  I stock up on small limbs and branches from the woods and have a bucket for chill-breaking.

We have a few hot days most summers.  I built a small second story porch on the east side (over the dining room) which is shaded from noon on and will serve as a hot night sleeping porch (when I get the railing built).  I'm hoping to avoid needing AC, but if the climate jumps several degrees I'll add a room unit to the east side dining room for afternoon escapes.

One thing that seems to really help with heat is having a metal roof.  The steel is quite thin so there is little mass to absorb and store heat for later in the day.  Even my storage area which is not insulated cools off quickly once the Sun is off its roof.

[Bob Wallace]

Power comes from 1.2kW of solar panels which are ground mounted.  That makes it easier to remove the snow- which I sometimes do 3-4 times a day.  (Some really sweet sunshine can sneak in between snowy clouds).

12 "golf cart" batteries in a 24 volt configuration.  Probably replacing current set with Trojan T-105 RE this year.  It's new battery time and the REs are a new product for off-grid use.  They have thicker plates and are rated for 4,000 20% discharge cycles.  They should last ten or eleven years.  And by then I expect we'll have much better options.

Backup with a 3500 watt gas generator.  I keep doing the math for a wind turbine but I just can't make the numbers work.  I think I'll probably add another kW or so of panels on the roof in the next couple of years which should greatly cut my fuel usage.

Water comes from a well in the orchard.  I pump to tanks which sit about 80' higher than the house.  That let's me pump when the Sun is shining and avoid running the pump off of batteries.

Sunny days are also laundry days.  Especially since I use a clothesline.  If necessary I finish stuff off overnight in the living room.  I installed some attractive "hooks" I found in Nepal and can string two 30' clotheslines.  The dry heat of the wood stove does a great job.

Regular 18 cu ft refer.  All CFL bulbs but expect to get my first LED this year.  Use a netbook and 20" LCD for computer.  "30 mile wi-fi" pulls only 4 watts.

Sixty acres with more than 50% in forest.  There's no shortage of firewood.  Just using the storm-downed stuff near the road is pretty much enough.

Now I need for someone to make an affordable 150 mile range EV with 4wd and good ground clearance....

[Neven]

For heating domestic hot water, I am using two 4'x8' (~1.2mx2.4m) flat plate solar collectors (similar to those in Old L's photos above) to heat an 80gal (~300l) stainless steel storage tank.
The rest of the solar thermal system is simply a closed loop design that circulates a glycol solution for heat transfer and also to prevent freezing.
A DC pump is wired directly to a small PV panel so that when the sun shines, the pump circulates the glycol solution (no controllers required).
It's actually a very simple system - a fellow up the road from me has been operating a system very similar to this for the last 25 years with the only maintenance being to recycle the glycol solution every few years.
The collectors are angled almost perpendicular to the winter noon sun so that they operate most efficiently in winter and less efficiently in summer.

That sounds good, especially the PV panel and the angle. I know some people who really tried to get the most energy out of their solar thermal and they have problems keeping everything tight because it gets pretty hot here in summer. It's much smarter to go for maximum winter gains. Summer is not a problem anyhow.

Solar thermal is generally not as good as PV from a strictly economic perspective, but economics isn't everything and solar thermal has its advantages - particularily in off-grid applications.

For starters it is much more efficient. PV only converts 15-20% of light to energy, ST has 70-85%. The main reason I've decided against it, is that PV is relatively cheap (for the time being).

Neven,
After looking at your "loam oven", I thought you might find these "rocket mass heaters" interesting:
http://www.richsoil.com/rocket-stove-mass-heater.jsp

I want to try to build one when I have some spare time 

I was very skeptical on first view, but I have now seen enough to know that I have to investigate further.   

I knew of the little rocket stoves they built in third world countries, but I've never seen anything like this. Will report later on my thoughts. Looks pretty cool, although I don't know if I can use it for our home (and I don't think it will be permitted by the municipality), perhaps the greenhouse.

Another downside to heating hot water with a stove can be that the thermosyphon can't be shut off if the storage tank reaches maximum temperature/pressure - at which point the tank must be allowed to vent somewhere or else you have (potentially) a large bomb in your house.

Definitely. But according to my calculations - for a theory of which I don't even know if it works - I'd have to try hard to accomplish that.

Bob Wallace, that sounds like a pretty nifty home you have there. Wow, just 1.2 kWp of solar panels to power everything.

[Neven]

I have looked some further into the rocket stove and although it's a very cool DIY project, it's not applicable to my situation, if only for the fact that it sucks in air from the room and that's a big no-no for my ventilation system. They also make it sound as if you can have the chimney exit into your house (only CO2 and steam!), but I don't think they're doing that. When it comes to creosote and stuff like that, I just don't know enough about the whole subject yet to judge that (have downloaded the Ianto Evans book though). Either way, I don't see how the rocket stove is radically different from the concept of the Grundofen (like a loam stove):



But a small one could be interesting for our greenhouse (heat and CO2). To quote Lucas: "I want to try to build one when I have some spare time". 

---

OK, now it's time to explain the PV concept I have in mind. I've done a lot of research in the past couple of weeks, and it's a very interesting subject, especially nowadays, because storage is getting more and more attention. As you all know, in the past years Germany has very aggressively stimulated the deployment of PV by offering high feed-in tariffs. This has proven to be so successful that solar energy is lowering prices during summer months (of course, consumers don't share the advantage in a culture that revolves around growth/profit). At one point last summer I believe that PV arrays were collectively feeding 40% of demand during peak hours into the grid.

On the one hand fossil fuel companies are going nuts over this, as they are losing money big time because they can't shut off their power plants when PV is outcompeting them, and so their lobbying firms (including German media versions of The Sun and the Wall Street Journal) are working overtime to influence politicians and population. On the other hand it is becoming increasingly difficult for the grid (which could use an update) to take up the power that Wind and PV are offering.

The result of all this is that the German Parliament has decided to reduce the feed-in tariff faster than anticipated. Now all the PV companies are going nuts, of course. On top of that the feed-in tariff only applies to a maximum of 70% of produced energy. This is pushing (home) owners of PV arrays towards options where some of the surplus energy that is produced by their PV array gets stored for later use, to increase total self-use as feeding into the grid is no longer lucrative. The Germans are now designing a storage subsidy to stimulate this trend.

Even though I'm no longer living in Germany, but in neighbouring Austria, I find the while concept of PV combined with storage very interesting. I try to find a balance between what is good for me and what is good for society. By incorporating storage into my PV concept I can increase my self-use from 20-30% to at least 60-70%, which is much more efficient than consuming power from far away (especially if it's from fossil fuels).  At the same time I'm relieving the grid somewhat during peak hours. That all sounds great, but getting there is not so simple.

More and more all-in-one solutions are offered that consist of batteries and the required hardware and controllers that make sure produced PV power first goes to appliances, then fills the battery and when the battery is full, feeds the grid, or when there isn't enough PV+battery power, grid power is used. This is of course more complicated that just a PV array and an inverter that feeds the grid.

The problem with all-in-one solutions is that they are quite expensive. Battery storage hasn't yet reached the point where it makes sense economically. I'm obviously doing it for other reasons as well, but not at any price. There is one relatively cheap solution from the Netherlands called PowerRouter, which is pretty cool, but there's one big downside for me:



All the functions of the PowerRouter are wrapped up together, just like a laptop. Laptops are great, but when one component breaks down, you can throw away the whole machine most of the time. Making a system of several components is probably a tad more expensive because you need more stuff, see for instance the PowerRouter compared to a set-up with components from SMA:



The SMA Smart Home system would basically work like this:



I have looked into this and discussed it a bit on a German PV forum, but the main problem of a system consisting of several components, is the central controller that makes sure everything works well and in an orderly fashion. One other option is that you dispense with feeding into the grid, you're basically running an off-grid operation that uses the grid as a back-up when PV+battery can't cover needs. For instance another Dutch company called Victron (that produces a lot of off-grid stuff for boats etc) has this system:



The advantages are that your system is simpler and you don't need an additional feed-in meter, which also saves on paperwork. What I dislike, is that your surplus power goes to waste, which really is a waste. That power - even if it's just 500-1500 kWh a year - could be used to replace fossil fuels. So this isn't an option for me ATM.

Other than the simple semi-off-grid systems there are very little solutions on offer, in the sense that you can go to an online shop where you just pick out all the components (like you do when building your own PC), which is why I'm forced to look into an all-in-one solution.

More on what I want in the following comment...

[Neven]

Basically what I want, is a 4-5 kWp PV array, combined with a 4-5 kWh battery system to enable me and my family to use 70% of the power that is produced by the solar panels. Here's a calculation to show the economics of the added battery storage system. Let's say I have a PV array that produces 4000 kWh a year, exactly the amount of electricity I consume each year. In the first example I have no battery system and use 30% of produced PV power directly. The rest of the power I use (from the grid), costs € 0,20 per kWh, which is offset by the € 0,06 I get as a feed-in tariff here in Austria. In the second example the battery storage system increases self-use to 70%.

1) Self-use 30%: 1200 kWh = € 0
Consumption - Feed-in = 2800 kWh x € 0,14 = € 392

2) Self-Use 70%: 2800 kWh = € 0
Consumption - Feed-in = 1200 kWh x € 0,14 = € 168

Difference: € 224 a year.

According to my calculations for what a battery system will approximately cost me (€ 4000-5000) it will take 20 years to pay off the investment. I can accept that. Energy prices are going to go up, feed-in tariffs will probably disappear altogether or get very low, energy spikes need to be dampened through storage, and the most compelling argument for me: decentralized energy (and food) production - even if less efficient - is good for democracy. Oh yeah, and I find it cool to use energy that was produced by my own home.

So what about those batteries? Maybe I haven't looked into it enough, but there are basically three options for me: Lead-acid batteries (LA), Nickel-iron batteries (NiFe) or Lithium-iron-Phosphate batteries (LiFePO4).

---

Oops, I'm running out of time. I will edit this comment later tonight.

[TerryM]

Neven

Definitely share your distrust of bundled systems where individual components can't be upgraded or repaired without tossing everything. Old gas heating systems, at least in North America, had all the safety cutouts as individual components that could be replaced when they failed at a wholesale cost of <$15 per component. The new improved systems wrap all the safeties and control components together on a solid state board. When any one component fails the whole thing is replaced for >$175.

It makes diagnosing problems slightly easier - "Something is wrong with the beast & we'll put in a new one' as opposed to " Your flame sensor is defective & we'll put in a new sensor" - but the costs to the customer are outrageous, and the bundled component is only available if the company producing it is still in business (the individual parts are generic).

Is there any way to set up a neighborhood power sharing system where any individual that had
surplus power could share it with a few like minded others? I realize that if the sun isn't shining at your house it probably isn't shining at your neighbors, but I was thinking of situations where someone might be on vacation or possibly where someone had a small wind installation and could borrow power from another that was using PV, only to pay it back at night.

Terry

[Neven]

Sorry about the time delay. I spent all my time off in the past two days reading stuff about PV, and then again, and again, and again. Slowly, very slowly I'm starting to get the gist. There are not many options yet, except for either expensive all-in-one solutions (where they charge big time for just one small controlling unit that makes sure everything works well) or the PowerRouter I presented earlier that is relatively cheap, but looks like a laptop. The company is also fairly new in this arena, so no one knows how long the PowerRouter will last.

I expect more companies to offer solutions with their own components soon, like the SMA Smart Home system I alluded to in my previous comment. This is the only component-based system that I have found so far that enables you to feed into the grid and take power from the grid when PV and battery can't supply enough. You basically need an inverter that transforms the DC from the solar panel array to AC for your appliances, an off-grid inverter converts that back to 48V DC to charge the batteries and feeds surplus energy into the grid, with the help of an energy manager and one or two meters that tell the off-grid inverter when to do so or when to convert the battery DC power back to AC (this is the part that makes the 'DC Coupling' slightly less efficient, but 'AC Coupling' has other downsides, like being less efficient when it comes to direct use).

I didn't look into the SMA system properly because I thought it would be very expensive. Turns out it is only € 500 more expensive than the PowerRouter, but with much better quality components (SMA is one of the top producers of solar stuff) that can be replaced. So I have at least one other option now besides the PowerRouter, and hopefully other companies (like Steca-Studer) will soon follow.

So now for the batteries. One of the most important criteria for me is the environmental aspect of batteries. They cost a lot of energy to produce, and it's only because they allow me to use more of my own PV produced power instead of inefficient grid power that they are an option for me, aside from the increased independence-argument. But the impact on the environment has to be as small as possible, which of course is difficult to achieve. I've tried and read several scientific papers on the subject, but there is no conclusive info on the matter. It leads me to conclude that there is no good solution out there at the moment, only less bad ones. Which one is the least bad?

Lead-acid batteries aren't an option for me, unless it's used golf cart batteries or something like that. Yes, they are the cheapest solution, also because they have been around the longest and there's a whole infrastructure behind them (a bit like with fossil fuels), but they don't last long most of the time and they're toxic. Sure, in the US and EU most lead-acid batteries are recycled more or less properly (even though in the US 3% ends up in landfills), but by buying lead-acid batteries, you're giving your money to companies that can then offer their cheap lead-acid batteries in third world countries where the lack of a national grid increases the demand for PV+battery solutions. But they don't have any recycling facilities there either, so where do you think most of those batteries end up?

Just a few weeks ago I translated a programme that was about the toxic legacy of Swiss landfills and industrial zones. Switzerland, one of the most civilized, richest and smartest countries in the world, has thousands of places that are incredibly toxic and leak the most horrible stuff into the groundwater tables, streams, rivers and lakes. This will cost tens of billions, hundreds even, to clean up. And they're not cleaning it up properly because it's just too expensive.

So the choice (for me ATM) is between Nickel-Iron batteries (NiFe) and Lithium iron phosphate batteries (LiFeYPO4). Now, at first I was very impressed by NiFe batteries. They're a bit like lead-acid batteries, big and slow, but without the nasty toxic stuff and much longer lasting. The NiFe battery was invented and further developed by Thomas Edison. Some of the batteries that were produced by the Edison company are still around today and functioning after 40-60 years. The Edison company was bought by a large lead-acid battery manufacturer in the 70's that basically shut the whole operation down after a few years (too expensive, or because NiFe batteries were much too good, killing the lead-acid battery market, as the conspiracy theory goes). Since then NiFe batteries are only produced by one Chinese and a Russian company.

When you search for NiFe batteries on the Internet, you quickly bump into websites that present it as the best thing since sliced bread that was suppressed for a long time, but now making a come-back. The NiFe battery is presented as an environmentally sound technology that is basically indestructible. Unfortunately it sounds a bit too good to be true. Although NiFe is definitely a big improvement over lead-acid (except for the price), there are some downsides to it too. Most of them are discussed in this long, but interesting PV forum thread, which starts with a lot of advertising by a NiFe seller, but then gets more realistic.

The batteries have an electrolyte of potassium hydroxide, which is relatively okay environmentally speaking (I believe you can also make soap and shampoo with that stuff) and depending on how you treat your batteries (how much you charge and discharge) you have to replace it every 5-10 years. When getting charged the batteries gas hydrogen, which means that every few weeks you have to top them up again with distilled water. So there's a bit of maintenance involved with the batteries, which is a bit of a turn off for me. Basically it's best not to charge them over 80% capacity (otherwise they gas more), and not discharge them under 50% (or the electrolyte gets spent quicker), which means you can only use 30% of their capacity if you want to get the most out of them longevity-wise.

The Edison NiFe batteries are very long-lasting. There are folks over in the US who buy old ones, repair them, put in new electrolyte, and they're ready for use again, sometimes with the same capacity as before. But I'm not so sure the Chinese and Russian versions are just as good. All of the marketing stuff that is done by US re-sellers is dispelled in the Chinese product documents. You can't charge or discharge them however which way you like, it's best to use only 30% of the capacity, and even then it's not sure how much longer than 20 years they will last. Yes, the metals used for the battery (nickel and iron) are relatively abundant and not difficult to recycle, but the Chinese and Russians add lithium hydroxide to their batteries to improve certain characteristics, and that's not nearly as harmless as potassium hydroxide someone told me.

So after all my research I've switched from this old technology to the newest of technologies. On the market, that is, as every month or so we hear something new about a revolutionary technology involving nano-graphite or superhyperultracapacitators. I believe right now lithium iron yttrium phosphate is the way to go for my PV battery storage system. More on that below.

[Neven]

There's plenty of lithium for the foreseeable future, but like all metals it has to be dug out and refined and what not. Unfortunately a lot of it is used to make batteries for electronic gadgets, but that's what you get in a consumer culture. The famous lithium-ion batteries have a fantastic energy density that makes them very useful for electric vehicles, but there have been some cons as well. For instance, there's a danger they blow up when overcharged, and the main reason they're not environmentally friendly is because of some of the metals used, notably toxic cobalt.

But this goes for the lithium cobalt dioxide LiCoO2 batteries which are now slowly, but surely being replaced by improved lithium iron phosphate, or LiFePO4, batteries. Like it says on Wikipedia: "LiFePO4 batteries have somewhat lower energy density than the more common LiCoO2 design found in consumer electronics, but offers longer lifetimes, better power density (the rate that energy can be drawn from them) and are inherently safer." Doping the material with Yttrium enhances these characteristics.

Even if LiFeYPO4 is more energy-intensive and less environmentally friendly than NiFe on a per kg basis, my battery system would need much less of it (84 kg versus 640 kg). Also when it comes to longevity, I think the LiFeYPO4 batteries won't last much less longer than the NiFe batteries. According to manufacturers LiFeYPO4 batteries have 2000 cycles with a DOD (depth of discharge) of 80%, and 3000 cycles with a DOD of 70%. To compensate for the PR of these numbers I'm planning on taking a tad more batteries to be able to limit the batteries to a DOD of 60% or even 50%. With 300 full cycles a year - probably not even that - the batteries should in principle be able to last over 15 years, after which they would still have 80% of their capacity left. Last but not least, the LiFeYPO4 batteries cost 30% less than the NiFe batteries, and I can get the latter ones relatively cheap through an Austrian gentleman who wants to sell them by collecting orders and then order large batches in Russia.

However, there is one thing that makes the LiFeYPO4 batteries more expensive than just the price for the batteries, and that's the necessary battery management system, which adds around 20% to the total cost. This is something I'm looking into right now.

---

So now I've basically told you all my ideas for the house we're hopefully going to build in a couple of months from now. None of these ideas are set in stone, although time is slowly running out for any drastic changes. First off my loam stove builder is coming back from holiday at the end of the week, and so I can finally discuss my idea of a stove that can also heat water. This will affect all of the decisions wrt energy production and consumption. We will also start getting offers from the 5-6 building companies, and pray every evening they're within our budget (they just need to build the frame, with insulation and windows in, and we will do the rest ourselves).

I will keep you up-to-date on the theory and then the reality.

[Lucas Durand]

We will also start getting offers from the 5-6 building companies, and pray every evening they're within our budget (they just need to build the frame, with insulation and windows in, and we will do the rest ourselves).

I will keep you up-to-date on the theory and then the reality.

Neven, please do - I'd like to hear how it all comes together.

I'm not sure how much experience you have "shopping" for a builder/contractor...
Or if the bidding process is the same where you are as it is here...

Be wary of taking the lowest bids - "customer service" counts for a lot in a project like this.
Be sure to clearly define what the builder's responsibilities will be and that any sub-trades they bring in will be clearly informed about what your expectations are (this is where good planning on your part will really pay off).
I'm guessing that in Austria there are many more builders familiar with a holistic approach to building (ie, the concept of a house as a system) - over here, finding a builder with this perspective can be problematic.

[Neven]

I'm not sure how much experience you have "shopping" for a builder/contractor...
Or if the bidding process is the same where you are as it is here...

I don't have much experience with it, except for when let a house in the Netherlands get renovated by the father of a friend of ours (no bidding) and all of it turned our more expensive than initially projected.

We basically sent several contractors our plans and then went over for a chat, explaining what we wanted basically, and they informed us how they build most of the time (all of them bar one advised us to use cellulose as an insulator). We told all of them more or less the same, and also that we wanted their bid to be divided into several categories, not just one price for everything. I know what materials approximately cost, and I can guess how much work it is for professionals, so we'll see how much they're throwing on top of that.

Be wary of taking the lowest bids - "customer service" counts for a lot in a project like this.
Be sure to clearly define what the builder's responsibilities will be and that any sub-trades they bring in will be clearly informed about what your expectations are (this is where good planning on your part will really pay off).

Definitely. Hopefully the contractor that appealed most to us has a price that falls within our budget.

I'm guessing that in Austria there are many more builders familiar with a holistic approach to building (ie, the concept of a house as a system) - over here, finding a builder with this perspective can be problematic.

Well, I'd say they have a tradition of building with wood, and most of them didn't give me funny looks when I explained what our aim was (an ecological passive blah blah house). Ecological materials and low-energy homes have become mainstream a while ago, although most houses on offer are still too big and filled with too much high-tech and unnecessary stuff to my taste. But again, blame consumer culture for that.

That's funny, I inadvertently made a typo: consumer vulture. 

[Lucas Durand]

That's funny, I inadvertently made a typo: consumer vulture. 

Neven,
Typo or "Freudian slip"? 

You've put down some interesting ideas for your project and I find I'm still digesting most of it.

In the meantime, I thought you might find the following presentation interesting.
It was given by Alaskan builder Thorsten Chlupp at a PH conference a few years ago.
http://passivehouse.us/passiveHouse/2010_Passive_House_Conference_Presentations,_November_6_files/2010%20Conference-Passiv%20Haus%20Alaska-Thorsten%20Chlupp.pdf

Herr Chlupp was kind enough to respond to many of my queries about his approach in this thread:
http://www.greenbuildingadvisor.com/community/forum/general-questions/19942/sunrise-home