Before I heard about this thing called Passive House, I knew it was important to insulate well, that windows on the South side could be designed to let in heat in the winter and that good windows make a difference. I knew that if you slapped a bunch of solar panels on the roof you could reduce your monthly electric bill. I knew that trees kept a home cooler in the summer and that energy efficient lighting and appliances were important. I was interested in the benefits of ‘green’ materials. I knew the standard stuff, just like my architect friends. Then I heard about Passive House and my world changed. The moment I read about it in 2009, I thought BINGO! Through all my blundering attempts to be green, I had never met a system that put it together like Passive House does. I was so excited, because I recognized that the Passive House system was the big enchilada, the way buildings should be built.
You may be wondering what is a Passive House – exactly. A passive house is kind of like a big igloo cooler. The cooler works because it is well insulated and doesn’t have any air leakage, a Passive House is just the same. I know that no one wants to live in a big red box, but the great thing about a cooler is that it is able to keep things warm or cold and a house designed like a cooler will do the same.
When people hear me say Passive House, they often think I am referring to Passive Solar. There is passive solar in a passive house, but there isn’t passive house in passive solar. Make sense? Passive Solar is about getting heat through your windows and storing that heat in some kind of mass like a big brick wall. Passive House utilizes passive solar strategies to gain free heat in the winter and keep the heat out in the summer; but Passive House is really focused on keeping that heat in or out, via a a well insulated, leak free building shell. Think big red cooler.
The are a lot of benefits to building a Passive House, I came up with 10 benefits though I’m sure there are more.
First, Passive Houses are comfortable. Leak free construction combined with insulation levels that are on steroids make for a very comfortable home. Comfortable in the thermal sense, not the luxury sense, though I think comfort is a luxury.
Second, you can expect low energy bills. I qualify this, because it’s not a magic bullet. Just like any house there are strategies that will result in lower energy bills. More than anything, energy use depends on the user, but a Passive House can certainly help the user do a better job. Passive Houses can reduce the heating and cooling loads, which are the biggest slice of the energy pie in most houses, by up to 90%. Yes, you read that correctly.
Third, Passive Houses are good for the planet. Since buildings are the biggest energy sucking sector in the US, building more energy efficient buildings is a good idea. More efficient buildings will help to reduce the C02 emissions that lead to climate change. For more on that check out my post on the 2030 challenge.
Fourth, Passive Houses are durable. Because they are airtight, they can potentially have problems in the form of indoor air quality. Think mold. I know, it’s gross. Nobody wants that and as a result Passive Houses are solidly grounded in building science which is all about preventing rot, mold or other building problems from occurring. I have to tell you I had never heard of building science until I took the course to become a Passive House consultant. It’s not part of architectural education, but with buildings getting tighter, anyone designing a high performance building better know something about building science. Because Passive houses are building science based, they go to great lengths to keep water out of roof, wall and floor assemblies. Water is the big enemy of building materials and the cause of most building deterioration issues. Dryer buildings = longer lasting buildings.
I think all buildings should be net-zero energy, which is a building that makes as much energy as it uses over the course of a year. Unless you like sending money to the utility company, why wouldn’t you want no utility bills?* There are two ways to get to net-zero. The first is a little awkward because it means slapping a bunch of renewables on your house and most homes have such high energy demands, that it means a whole lot of solar panels…probably more than your roof can hold. It used to also be prohibitively expensive to do this, but that is changing, which is great! The other, and in my opinion best way to get to net-zero energy use is to reduce the energy load before slapping on the solar panels. The energy load is forever reduced and the added solar panels can be very minimal to get to net-zero energy. That was number five.
Number six is that Passive Houses have great indoor air quality. Because they are airtight, they need to get fresh air from somewhere, right? Instead of relying on all the leaks and mystery pathways for air to enter the house, which is what most houses do, Passive Houses rely on something called an energy recovery ventilator (ERV) or a heat recovery ventilator (HRV) to bring fresh filtered air into the home. It’s a way to bring in fresh, filtered air using an energy-efficient heat exchange process. The result is fresh air, fresher than most of us are used to.
Seventh, there is a unique architecture to a Passive House. You won’t find big expanses of glass, concrete or steel in a Passive House. That’s because those materials aren’t well insulated. In fact, concrete and steel are particularly good at transferring heat from inside your building to outside, meaning you lose a lot of energy quickly. Passive houses tend to have thick walls, easily a foot thick, and strategically placed windows to get the most solar gain in the winter. They tend not to be very large or complicated with innies and outies because that makes it more difficult to properly seal and insulate. Smaller footprints waste fewer resources as a general rule and passive houses can be any size, but are generally kept on the smaller side.
Eighth, Passive Houses Cost more. You’re wondering why that’s a benefit, right? It’s a benefit because no matter what, you will end up paying for the cost of energy to run your home. It’s a pay now or pay later kind of thing. By paying up front, you actually save money. There is typically a very short payback for the additional money spent, average 7-10 years and from then on out your utility expenses will be lower than your neighbors by a very significant amount. Effectively saving you money over the life of the home.
Ninth, You can open the windows in a Passive House. I should have mentioned this earlier, but just because the house is airtight does not mean you can’t open the windows. When it’s nice out, turn off the ERV and throw those windows wide open and enjoy the day.
Tenth, getting to the finish line here… and I know I’m stretching it a bit. Passive Houses are cool, in a nerdy kind of way. Imagine inviting some friends over on the coldest night of the year for a lovely dinner and the heat isn’t on. Thanks to your friends, the heat they generate, plus the heat from the oven used to cook your lovely dinner are keeping the house warm. I suspect your friends might think you have the best house on the block. That’s kind of cool, isn’t it?
Here’s a bonus item, passive houses are quiet. With well insulated walls, doors, windows, floors and roofs it’s pretty quiet. You won’t hear the traffic outside and you won’t hear that low roar of the city. You might hear your ERV if you really pay attention, but overall a passive house is pin drop quiet. That’s a peaceful thing and adds to the sense of comfort.
There are thousands of Passive Houses in Europe, and not so many in the U.S. That is changing quickly as more american architects and builders are trained to become Passive House consultants. I have a board on Pinterest devoted to Passive House and you can see the big range of Passive Houses that have been built. It’s hard to pick my favorite, since I only pin ones that I like.
Is Passive House for everyone? Even though I think it’s the best way to build, I don’t think that going full Passive House is the right solution for everyone. Passive Houses do cost a bit more, but not enough to make you not do it, see number eight above. It’s more about the skill and commitment level to do it. It takes a little extra to get there. First, you need to have the building modeled by someone like me using a computer program to verify that it meets passive house standards. Then, you need a team that has the skill and commitment to pull it off, because without that you are sunk. Finally, to get your passive house certified you need someone to review and verify that it will perform as designed. If you have all of those, by all means do it! If not, I think that building according to passive house principles and building a high performance home is a very good solution for a lot of people. Both will get you to net-zero, which is what I think is most important. Passive House will get you there with fewer solar panels, but frankly it’s not that much less. The big difference is probably in the comfort level, Passive Houses will be more comfortable and of all the reasons that people go Passive House, that is one of the biggest.
*If you are grid connected, you will pay your utility company a small fee every month for the privilege of being connected…and turning your lights on at night.