Most ‘Houses That Breathe’ Aren’t Very Comfortable
Instead of expecting fresh air to come through your leaky walls, give your house a set of lungs
Recently I heard another comment from a builder who wants to build a house that breathes. I started to reply in an e-mail, and then decided to write a blog instead.
What we are doing nowadays in the world of high-performance homes is based on studying hundreds of thousands of houses built in the last half century that have failed — including the majority of superinsulated and passive solar homes built in the 1970s and 1980s in the Northeast — and applying those lessons to building a durable house.
Houses from before that time period that failed for one reason or another are mostly gone, and many of those that remain are piggy banks for big oil. We put our money in and the oil companies take it out. Simple. (Usually, I like simple, but not in this case.)
For the past few decades, most builders in the Northeast have been living in a vacuum, while builders in northern European and Canada paid much more attention to how houses fail, learning from them and adapting. Now the conversation is opening up again, and we are taking a seat at the table.
A house has to breathe? Really?
I have lived in houses that breathe my whole life. It sucks.
Aside from the part where you have to give your money to someone else just to prevent freezing to death in the winter, there is the comfort aspect of things. Houses I have lived in have never been all that comfortable, whether in terms of temperature or moisture levels or even wiping mildew off the window sills.
Now, with two children, I worry about the air quality and mold issues inherent in my “house that breathes.” I would rather be able to seal up the house in the winter and be confident that I was breathing fresh Vermont air all the time than have to step outside for a breath of fresh air or open up the doors and windows if I screw up on getting the wood stove going.
Six months out of the year, I would still have the choice to open the windows and turn off the HRV.
We do seem to have more summer moisture and humidity problems than we used to, but we also have access to more durable and proven materials and building methods. Some builders and architects are taking advantage of this, but most are building the same way they did 20 years ago, despite all the failures.
A house that breathes and has little or no insulation is a barn. And If you want to heat it, that means coming to terms with giving your money away. Jesse Thompson says, “People breathe air through their lungs, not their skin. Why should houses be any different?” If you want your house to breathe, give it a set of lungs — in other words, provide it with a mechanical ventilation system.
There are a range of options for doing this, from exhaust-only bathroom fans and range hoods (simple and cheap, but where does the makeup air come from in a very tight house?) to a full-on heat-recovery ventilation(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. (HRV) system. These are also fairly simple and effective, although significantly more expensive. But they have the added advantages of recovering much of the heat from the outgoing air as well as providing fresh incoming air exactly where you want it. For more information, just type “HRV” or “house ventilation” into the search box on Green Building Advisor, and start reading.
Robert Swinburne is a part-time architect and full-time homemaker living on 49 acres with his wife and two young children in Halifax, Vermont. He was a carpenter for several years after architecture school and is now a licensed architect and passive houseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. designer with over 100 completed projects in the Northeast. Bob maintains a blog (primarily for therapeutic reasons) under the moniker “Vermont Architect.”
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