Daily Archives: March 10, 2010

Passive Houses and other tight houses — When the power fails

OK, so we know that passivhaus homes are superinsulated and built tight. That’s good right? Less heat (or coolth) flying out the cracks and thru the walls. But one needs fresh air! I think it’s a valid concern people have. I mean, day to day things are hunky dory… the HRV or ERV (heat recovery ventilation system) in a PH is bringing in fresh air at a rate that is quite excellent… by design, instead of just hoping that it leaks in. But… what about when there’s a power failure / power cut that lasts a while?

Open 2 windows a little.

The total “effective leakage” area of the house will still be minuscule compared to most homes. In fact, this is the same idea as the approach that some think is superior to an HRV/ERV for day to day living — usually called “exhaust only / passive inlet” ventilation I believe. So instead of 2 windows cracked, you have a super efficient and quiet bathroom fan (Panasonic WhisperGreen one used to be called?) that runs on a timer and you poke a hole with a damper in another spot in the house. Instant ventilation. But harder to direct to individual rooms and no heat-exchange. Some still think this is a better way. The K. I. S. S. approach.

Anyway, back to window opening. This again might be seen by some as a disadvantage. With most houses, one could maybe claim that the owner/user doesn’t to know a single thing except to pay the bills. (Passive House folks say that their is evidence to the contrary… that many of our buildings are inadequately ventilated. Interesting.)

But back to passivehouses and power failures. Such an house might be lacking in fresh air during this time. But it doesn’t seem like it’s asking too much to open windows. Especially since this is a rare occurrence in most places, and meanwhile, for 95% of the rest of the time, their air quality is probably better with active ventilation. I am open to hearing otherwise, but my guess is the case.

People are used to having to make sure that they have oil or propane (or wood!) delivered in many parts of the world to avoid freezing in the winter. And to make sure their AC is working if they’re in a warm place. So is opening the windows asking too much?

I suppose a parallel analogy is seat belts vs air-bags. I believe as early as 1959 Ralph Nader thought air-bags were important in cars because one could never expect that people would use seat-belts. And remember those automatic seat belts on tracks? Gone! We now understand that good old normal 3-point seat-belts are WAY effective AND people will use them. Airbags are an excellent addition, but they can’t replace belts. OK, so I am trying to equate the active participation in home-operation with the active step of putting on a seat belt. Seems reasonable. People can be expected to know to open their windows if need be. One can install CO2 monitors for that matter…



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