Passivhaus Detailing and Design
architizer.com
architizer.com
In Hanoi, many houses have a small greenhouse-like glass structure on the roof. The greenhouse has a chimney. When the sun is shining, it gets hot in the greenhouse and the hot air escapes through the chimney. A hatch through the roof into the greenhouse draws new air from below, essentially creating a passive, sun-powere air-flow through the whole house, bottom-to-top. Usually some windows on ground level are left open to let air in.
As a result, such houses are very well ventilated when it is cold outside. Mould is not a problem. The potential problem is instead excess dryness in places where it gets very cold.
You just need to cook more pasta: large pots of boiling water. :)
More seriously: a very airtight house, which is generally desirable, does need a properly balance HVAC system. In some climate zones this means perhaps having a humidifier and in other zones a dehumidifier.
Most people only think about furnaces and air conditioners when considering HVAC, but those mostly deal with temperature. Humidity has to be considered separately, often by different equipment.
My point, if any, is that it's not "Passivhaus or nothing."
Few(???) architects and zero builders seem to understand light/wind/circulation like people apparently intuitively did 200 years ago. You might be better off with the average curious engineer designing a house after reading a couple books than the average architect. Everyone is astonishingly lazy, even mansions around here have terrible light/circulation problems. But if you care, you can totally design a good one yourself that has very low operating costs (our electric bills are 50-80 a month in a 2200sqft house. We use maybe 3 cords of wood a year, but that's very approximate).
It does not take a lot of work to design a house, especially if you want to build an efficient Colonial style. My goals were simple: Build something that appears traditional, maximizes light and airflow and wood burning heat. Think about ventilation passageways as the windows and doors, and think of the wind as coming and going. Since heating is easier than cooling (we built in no AC system and zero ducting), make your ceilings taller.
A little wood stove (Vermont Castings Encore) heats the whole thing. Spray foam insulation in the walls (plus fiberglass), tall ceilings, and modern windows (lots of them) is all you need.
Some pics of what I built, with design sketches: https://twitter.com/simonsarris/status/1183143604925190144
Any book recommendations, especially around wind/circulation?
I realized that the cupola on my 1840's house growing up, this was it's function. Wind pulls air through, which pulls air up into the attic, which cools the first and second floors.
Then read The Timeless Way of Building and perhaps A Pattern Language
Then Get Your House Right, or a condensed (...in a way) version is Drawing for Architecture by Krier.
Hmm there are probably others I cannot recall right now, but those are a great start.
Unfortunately I have no choice. Unlike in Germany I don't get to buy the land and pick the builder. The two come bundled in the UK. And will do until we get political change that breaks up the building oligopoly.
Developers simply have the money/the better leverage by buying in bulk. Then there are developers that simply sell you the (tiny) lot for a premium, and let you choose between something they arrange, or building yourself. And the good lots are always gone long before the project is announced anyway.
> Airtight design resulting in draught free construction
That airtight design leads to problems with mold if you have any cold spots. These spots can occur due to construction faults, material faults, or any kind of acquired damage. For instance, you might not even notice that your windows do not shut exactly as they were supposed to after a few years.
In the end, the repair of such a complicated design is again very complicated (especially after a decade or two have passed and technology has again advanced), expensive, and error-prone.
So for me, I'd rather prefer to take an existing, robust and dry building, insulate it somewhat (especially roof and windows) and put in a regenerative heat source (wood, electric) but not to focus too much on the actual energy needed.
But the filter is on the ingoing side and not on the outgoing side, so no moisture from the inside can aggregate there. Only the humidity from the outside but we've never had problems with that.
Okay. I guess I have been wrong.
A point. All the energy savings disappear the moment you open a window.
Ideally you would want your insulation outside of vapour barrier:
* https://www.buildingscience.com/documents/insights/bsi-001-t...
And the ventilation system takes care of the rest of humidity, especially after taking a shower or when cooking.
The price is right too.
Remember it's the energy TCO (total cost of ownership over project lifetime) that captures the full environmental impact of the house, as every MJ of energy - regardless if embodied or operating - translates into a known quantity of GHG emmissions, particle pollution, and so on.
In a pleasant surprise, spending energy later (in energy costs, rather than embodied) is better than spending it today for the environment! Energy produced in the future will surely emmit less GHG and pollution than today (better techniques!), and the GHG will dwell less time in the athmosphere, so less compounding effects on the total temperature rise that we'll have at the end of this century.
If you care about the environment, you have to consider the energy TCO.
https://ec.europa.eu/energy/en/topics/energy-efficiency/ener...
The actual implementation is left up to individual countries. In my country, Lithuania, it means from 2021 all new houses require insulation to be at the same level as Passivhaus, and buildings to obtain the majority of their energy from renewable sources (so most new houses will have PV installed). It gets cold here in the winter (-20c isn't uncommon), so if it can work here, it can work pretty much anywhere in Europe.
As can be expected this will push the price of new builds up, but the benefits are a more comfortable and healthy environment (I grew up in drafty & moldy houses in the UK) and lower energy costs (grid-tied PV installations, without a battery, usually pay back in 7 to 10 years, after which they provide free energy for the life of the system).
Edit: I should mention the prices will not rise in a significant way. Materials for the structure/building envelope are usually a small part of construction costs, and those required for Passivehaus are not expensive or hard to obtain. Of course propery developers will complain, as the extra cost will come out of their profit margin :-)
I have a friend who is a building a house by himself. I think that's really cool. If you set standards too high that wont be possible.
Finally bureaucracy sucks. Even an "obvious" regulation that all houses follows like "your house has to have a roof" has the potential to become seriously annoying if you have to get an inspector who is only available in a month and only on Mondays 9-10, to take a look and write a statement that your house indeed does have a roof.
Apparently "14% of UK greenhouse gases come from our homes, a similar level to emissions from cars. In major cities gas boilers are also a main source of nitrogen dioxide emissions."[1]
The standard is still storage headers and other wall mounted electrical heaters. I remember those from childhood, and how happy we were to switch to gas-fired central heating.
There are electric boilers which can power a hot-water based heating system; they are substantially more expensive to operate than current gas boilers (due to the UK price differential between gas and electricity).
My most favoured approach is an air source heat pump, and larger radiators/underfloor heating to make use of the lower temperature heat source. More expensive to install and run than a gas fired central heating system.
Perhaps in the house after next, this will be standard - or I might even be able to buy a Passivhaus.
Underfloor electrical heating is apparently a lot more efficient than radiators, e.g. because you only need to run them at a much lower temperature. If you combine with things like ground source heat pumps and solar panels, the electric heating proposition looks a lot more appealing.
That said, the conclusion I came to is that for an old place that doesn't otherwise need major work, it just isn't worth the expense of making the switch. It might be that if I were to move somewhere that needed a complete refurbishment anyway, then I would. Even then, with most homes, at least in cities like London, being flats rather than houses, then things like solar panels and heat pumps become much more difficult if not impossible to arrange.
[0] https://www.designingbuildings.co.uk/wiki/English_housing_st...
[1] https://en.wikipedia.org/wiki/Prefabs_in_the_United_Kingdom
[2] https://www.theguardian.com/society/2009/mar/17/historic-pre...
https://ww2.energy.ca.gov/title24/2019standards/documents/20...
https://www.vox.com/energy-and-environment/2019/5/31/1864690...
Like applying the Toyota Production System to A/E/C.
Better improvement at a faster rate, without the inevitable recurring food fights (lawsuits).
> Why is it still legal to rely on fossil fuels for heating for example?
Because there are few alternatives. You can use wood, but that comes with its own problems.
These nowadays come typically with moisture recovery (which arguably not always works well enough, depends on how much you still need to heat).
Theoretically that could work with a reliable air conditioner. In practice, I know quite a few passive houses that have problems with mold.
And seriously, no air conditioner is superior to opening windows, don't kid yourself.
A "normal" house with a good insulation (don't overdo it) would be my preference.
And if you're in warmer climes, air cooling rather than air heating.
But yes, the windows do open.
If at any point in the building's lifecycle the thick glass wool insulation is wetted (such as through a building/materials fault, an accident or some very slow process), a hidden mold problem will start developing within the walls. By the time you notice it (strange smell, irritation in lungs or eyes), it will be too late and the most economical solution will be to demolish the whole house and building a new one.
People who live in cold and wet climates know this all too well. OTOH, thick insulation is not required in warmer climates.
You also need to ensure you choose the correct building materials, so they can ventilate themselves. Modern building science says there should be a continuous airtight wrap around a house with insulation either side. The interior insulation ventilates to the inside, and the exterior ventilates to the outside. What you don't want is multiple airtight layers as that could cause it to become moldy inside the layers.
Passivhaus houses will almost always have a heat-recovery ventilation system. These will bring in fresh air and take out stale air - like a bathroom fan. But they also exchange heat from the outgoing to income air in the process. Typically 80%+ of the heat is recovered (you can get systems that are 95% efficient). They run at a low speed so consume minimal electricity (typically under 100W for small houses) and don't provide a noticeable draft like air conditioning or forced-air heating. They have filters to prevent pollen and other contaminants from entering your house, so for allergy suffers they are a big plus.
I live in a cold climate in an apartment built in 2015, which is well insulated and has this system. Even though it has been below freezing (currently 8c) outside, we haven't yet needed to turn on our heating because of how well the building is insulated. We do actually have a typical vented bathroom fan, but everything else (kitchen hood and dryer) are unvented, so we keep all that heat inside.
My random web-crawling has certainly been moderately productive, but it's slow and I can't help but feel that I'm not being adequately exposed to a reasonable breadth of topics.
Do searches on "building science":
* https://en.wikipedia.org/wiki/Building_science
A consulting company specifically started around the concept because the founder, Joe Lstiburek, got tired of seeing the same problems over and over:
* https://www.buildingscience.com
* https://en.wikipedia.org/wiki/Joseph_Lstiburek
This contractor based in Austin, TX, has a lot of good content:
However, those buildings are not as amazing as they might look. The "better" the standard, the greater the effort. What people didn't really took into account was the energy needed to actually build the house is becoming very large. At this point it takes the same amount of energy (embodied energy, called grey energy in Germany) to erect a Passivhaus as it will need operating over the next 50 years.
I was also under the impression that many passivhaus implementations made heavy use of wood, and thus end up sequestering carbon for the lifetime of the building, but I don't know if that's mandated by the standard or just a preference of some builders.
That doesn't mean much since it takes less and less energy to 'operate' the house. For energy-positive housing it by definition takes more energy to build the house than to run it for a single day since the house is a net energy producer. Leave that fact out and use it as a headline and you can guess the reactions.
What is important is the trade-off between effort spent in creating energy-efficient infrastructure - whether it be housing or industry or roads or whatever - versus the expected returns, the projected lifetime, the means to distribute energy and more. Having an energy-positive suburb won't gain much if there are no means to transport the energy to the city centre or industry where it is needed. Insulating against -20° winter temperatures does not make sense on the Canary islands (and no, insulation is not the same as thermal buffering which can be used to lower inside temperatures during hot days, viz. adobe constructions).
Is that because the build energy is so high or because the energy usage is so low? I mean, by definition the energy used by a zero-energy house is zero. Shouldn’t you compare the build cost to a conventional house’s energy usage?
Simply building a house in Germany at the moment results in a passivhaus. We also added the ventilation system which wouldn't be necessary, but I like the system, needing not to open the windows in winter that often or at all.
Why is it becoming larger? I would have assumed that we would use less energy rather than more to build buildings nowadays given the advances in technology.
That said, I live in a passive house and we turn on the heating only when one of us is sick or when it gets really cold.
For many houses the better heat insulation is mineral wool and or styrofoam. Transporting either of these must be significantly more energy efficient than brick. If I look at how some old buildings are built here I have to assume that was not energy efficient during construction just from how much more material was used.
Do you have a source that better insulation requires more energy? Especially the extra windows must be more energy efficient during production as well if you look at how they are manufactured. They only extra material is a third glass pane but for that you save on a lot of extra fittings compared to old windows.
I would really like a source on why you think there is more energy used for building the house. It's very counter intuitive.
I'm a real estate developer. This is elaborated on, ad nauseum, in 1000's of studies, for the last, oh, 40 years. Don't be That Guy(TM).
The focus of a passive house is on energy efficiency while Zero/Plus energy buildings try to have a positive net value.
While it certainly helps, energy efficiency is not required for a zero/plus energy building: You just have to produce more energy than you consume.
Regarding the building cost: As far as I know, the building cost is not greater compared to that of a normal building.
One problem with complex buildings is the limited average skill of the builders and variable quality control in the business. Building technology should take that into account.
Probably one reason is the volatile nature of the business - you have to hire anyone you can get because everyone else is building too at the same time.
So I guess if one were to "disrupt" construction, one would have to start from the financing...
I'm sure there's lots of this already going on. New houses built recently near me have all the walls delivered on a truck preassembled, but the skill and quality of the assembly teams from house to house has been interesting to watch from afar.
An alternative is to make sure that all materials are breathable and dryable. But even things like glues can be problematic.
I have seen houses that have been almost completely made out of pure timber (no glue!), nails, wool, clay and chalk. Some steel joiners. No glue. They don't even have regular paint in the rooms, it's clay with a hemp mesh inside and then chalk on top, or some such. I don't know how the bathroom was handled.
Building with stone and materials for insulation that allow no diffusion are a problem too.
Builders need to conform to rules and norms of course.
> Some estimates suggest there are well over 50,000 Passivhaus buildings around the world. They have been successfully built in European climates, the US and Canada along with warm Asian climates where there is a requirement for cooling.