I’d never heard of “Passive House” or “Passivhaus” (as the Germans or fancy pants folks like to call it, myself included) when we started the process of starting to design our house.
I had heard of “Solar Passive House” though. As far as the history goes as I understand it, in 1973 the OAPEC (Syria, Tunisia, and Egypt) issued an oil embargo on the USA – due to some silly war on a foreign nation that Americans had gotten themselves into, again (weird). The oil embargo caused a pretty major scare to oil loving North Americans. With this sudden rise in oil prices ($12/barrel!) and potential for oil shortage, people became very worried about what a world without oil could be like… “How else can we heat our houses?!” and “How will we drive our cars?!”
Strangely enough this led to some novel and creative ideas, like “Why not insulate our houses better?” and “Maybe I could use my legs for transportation or drive with my friends and colleagues to work” and “Why don’t we use that big flaming ball of fire in the sky to magically give us free heat and energy?”
These earth shattering and brain melting ideas led to some interesting developments, one of which was the “Passive Solar House.” Some of these were better than others. But the basic concept was quite simple: Face the house to the sun, put a bunch of big windows in front of the sun, use concrete or rock on the floor or walls (thermal mass), and then insulate the walls better to retain this heat. Ta-Da! Less oil and gas to heat our crappy leaky houses!
Unfortunately for the world and future generations, only a handful of these houses were built as the oil embargo was lifted and cheap oil flowed again allowing people to forget about solar energy and other sustainable/renewable resources. People went back to the way they’d always built homes and functioned as they always had in their day to day lives. It’s sad and a bit amazing to think of where we would be as a world now if we’d have taken those sustainable ideas of renewable energy sources and continued to apply and develop them to an even greater degree. We seem to be at a similar point in history now as they were 40 years ago…
Anyways, Darcie and I actually looked at a Passive Solar House in Saskatoon when we were house hunting 5 years ago. Admittedly, most of these homes had a number of issues (although I still believe that had the oil embargo lasted longer a lot of these issues would have been easily addressed on a large scale) including: poor ventilation (they were stuffy due to lack of airflow), too hot (they felt like a greenhouse and so were often later retrofitted with air conditioning), still leaked heat and cold (not airtight), there was no passive shading outside (again overheating in summer or not adequately heating in the winter), and too humid (again poor ventilation).
What is really awesome though is that there were a very small number of houses that totally nailed it! One of those houses, considered to be the first “Passive House” was built in Regina, SK by the Saskatchewan Research Council in 1977.
It’s pretty amazing that the first (unofficial) Passive House, using only two water heater for heat sources, was built in Saskatchewan. The Tyee has a great little write-up on it here: “Step Inside the Real House of the Future”
This house was built by some very forward-thinking people at the Saskatchewan Research Council, including Rob Dumont from Saskatoon (more on him later). They recognized some of the earlier problems with the Passive Solar House including air leakage and poor air flow/quality. They were able to develop a means of extreme airtightness and significantly reduce the leaking that happens in most houses. They also developed one of the first mechanical ventilation units that brought in fresh air from the outside, pre-heating it with stale interior air and circulating it through the home. Pretty neat!
A ton of people (upwards of 30,000) came and looked at this house in the late 1970s and 1980s. Two of those were a couple of German professor dudes named Wolfgang Feist and Bo Adamson. They studied that SK house and two others in the US that had also proven themselves to be extremely energy efficient. They returned to Germany and over the next several years studied and refined what they had seen abroad with the goal to apply it to the building of new German homes. Eventually this led them to founding the “Passivhaus Institut” and developing two basic requirements that all true Passive Houses must meet:
1. Every building must pass a blower-door test demonstrating exceptional airtightness. The Passivhaus airtightness standard (0.6 AC/H @ 50 Pascals) makes the Canadian R-2000 standard (1.5 AC/H @ 50 Pa) look lax by comparison.
2. Every building must consume no more than 15 kilowatt-hours of energy for heating/cooling per square meter of floor area and 120 kilowatt-hours per square meter for total energy consumption. While R-2000 and most other green building standards govern only energy used for heating and cooling, the Passivhaus standard applies to all energy — including lights, appliances, entertainment and hot water heating.
Ok, yea so what do those numbers mean?
The first one applies to air tightness of the building’s envelope (the walls, roof, windows, doors, and floor). Most houses are terribly leaky. I know ours is. It’s 102 years old. Even though the windows have been replaced we can feel a draft near most of them and there are cold spots throughout the house. That’s why we run our furnace, like most households, all the time. Passive House air tightness looks to eliminate air leaks and drafts to extremely minute levels. This is tested with a blower door test, which is just like it sounds: seal the doors, run a fan at the door, create negative pressure and measure air leakage. For comparison sake, most conventional houses leak at a rate of 15.0 air changes per hour (AC/H). To be certified as a Passive House, air leakage can be no more that 0.6 air changes per hour!! It doesn’t take a lot of thought to realize what a massive effect that would have on your need to heat (or cool in hot climates) your house, once it’s heated, it stays heated and you need a lot less heat to make it comfortable.
The second applies to how much total energy the house consumes. This applies to all components of a home that make it function. A high level of insulation, proper solar orientation, passive shading in the summer, solar gain in the winter, and a simple layout of the home will each have fairly significant effect on how much energy the house will require. Still, comparison helps here. Consider this:
- The average Canadian home consume 59% of total energy in heating
– 43,506 Btu/ft2 per year
– (137.2 kWh/m2 per year)
- Homes built to today’s Passive House Standard, consumes 6.4% of total energy in heating
– 4755 Btu/ft2 per year
– (15.0 kWh/m2 per year)
Ok so basically a Passive House is 30x more airtight than a standard house and consumes 53% less energy for heat. That makes for a seriously energy efficient house. (http://design-build-energy.com/passive-house/)
Essentially this shifts the conversation of house building away from “How am I going to heat my house?” to “How am I going to keep the heat in my house?” Consider a coffee mug versus a thermos. A mug of coffee will be cool in a matter of a few minutes while a well-insulated, air-tight thermos can keep it hot for hours.
I had never thought of these common sense concepts before when considering building a house until we told our house designer and friend, Crystal Bueckert at BLDG Studio, that we wanted a “Net Zero” house. She said “Nah, you need a Passive House.”
You see, a Net Zero house can get to net zero how ever it wants as long as you balance the energy you use by what you can replace. So theoretically you could have a regular old leaky house but as long as you replace all your consumed energy with solar panels, a windmill, geothermal, etc, etc. then you could still be “net zero.”
Passive House makes reaching net zero relatively easy. You consume way less energy, so throw a few solar panels on the roof and, boom, you’re net zero. In fact, most Passive Houses with PV panels are Net Positive houses in that they feed back onto the grid as they are netting more energy then their super-insulated and airtight house needs.
Now that’s sustainable living.
8 thoughts on “What is Passivhaus?”
Nice to discover your blog here.
Possible worth clarifying that although the passivhaus standard has a requirement to be under 15.0 kWh/m2 per year this is specifically for space heating (& cooling). The requirement for total energy consumption (including lighting, appliances etc) is to be under 120.0 kWh/m2 per year primary energy. By “primary energy” this means the amount of energy generated at source, so taking account of inefficiency at the power source and inefficiency in the distribution grid, the actual consumption requirement will be slightly less. For example in the UK if I use 1kW/hr of electricity the power station actually has to generate about 1.2kW/hr.
I look forward to reading future blogs & following along your journey!
Hi Elrond, thanks for the clarification. I’d actually pulled that stat off of Canadian Design Build Energy website (link is in the article). I meant to double check that with a Passive House book I have, but I’ve lent it out to our builder. It’s a fun journey thus far and we will certainly be writing lots about it. I’ll be certain to visit your site. Best wishes!
By the way, my passivhaus blog is at elrondburrell.com which you may find interesting.
Best wishes, Elrond
Kent, Have you done any analysis on the effectiveness of your windows and concrete floors? I was told that this idea doesn’t work well in northern climates since the angle of the sun is so low that you end up heating the back wall and not the floor. Also, the science behind using a thermal mass seems to indicate that it only works well in climates with large daily temperature variations (ie hot days and cold nights). I’d also love to hear your thoughts regarding the in-floor radiant heating system you used as I’ve heard that such systems never really seem warm on the feet and can take a long time to effect the ambient air temperature.
The duxton windows have recently been passive house certified. So we’ve been very happy with them. I think your point about the effectiveness of he thermal mass concrete floors is over rated. We like the concrete floors for the aesthetics too so kind off a moot point for us. We keep the in floor heat at about 68F so it’s always a little warm. The sunlight during the day does tend to heat the house up to mid 70s during the day. But by 10pm or so it usually has cooled back down to 68/69. The in floor heat does not respond well to rising and dropping your temperature during the day for example, turning it down to 65 at night and 72 during the day- it just takes too long. It’s best left at one temperature
I love the look of the floors as well but I’ve also read that combining radiant in-floor heating and passive solar makes no sense since any potential solar gain is wasted if you already heated the floor mechanically. If you had it all to do again, would you bother heating the floors or just let the sun do it? I plan on building a house about the same size as yours and I’m considering just installing electric baseboards with either a natural gas fireplace or wood stove as backup.
I’d read that too but we decided to do it anyway. That’s why we keep the in floor temperature lower – still maintaining some baseline heat in the floors – but then the sun can do the rest or our wood stove if we want to take the edge off on chillier mornings. If you didn’t want to heat the concrete floors then I wouldn’t recommend installing concrete floors without it. We have a cellar in the basement that we didn’t put in floor heat in and it’s a lot cooler on the feet. If you’re planning on baseboard heaters and the like then concrete floors wouldn’t be a great option I think