Daily Archives: April 27, 2011

Summer with a WORKING hrv – latent vs sensible loads

Last summer our HRV was mostly busted/confused. It was confused by controller wiring and was running in recirc mode where no fresh-air is pulled in. I figured it out using this CO2 meter after being annoyed that CO2 levels (monitored by a Telaire 7001) were not dropping in the house, even when the HRV was running on high/5.

Anyway, the point is, it will be interesting to see if we need to do something like the link below describes this summer. Namely using our standalone dehumidifier to dry the house off since we will probably not often actually need much AC (when it was 100F last summer, we would turn it on just a little at around 5pm). Or maybe the hot-water heat pump will dehumidify things enough even with the HRV bringing in some moist outside air (it’s pretty ridiculously humid at times in the summer here in MA).

Actually, I think the minisplits have a dehumidify mode, but I bet there is a catch.

LINK (see the section “Reduced Heat Gain” and the photo “Photograph 6: Hotel Room Fix”)


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Filed under erik-green, HVAC, passive house, superinsulation, zero energy home

Go small or go home?

Here’s how I see it…. if you are building/renovating a house and you are trying to:

a) build net-zero (primary energy) instead of the typical approach (climate-independent) of keeping utility bills to less than a few thousand dollars (meaning less insulation in warmer climates)


b) not trying to go (too) broke


c) you have good sun

then you have a few options:

1. passivhaus with PV
2. more typical superinsulated with PV
3. passive solar with woodstove and PV
4. active solar (perhaps not with even a woodstove) and PV. Done right, I suspect this active solar can be done on the cheap — the Yahoo Groups SolarHeat and SimplySolar and Gary’s builditsolar.com website have some smart people with some ideas. (One needs to be able to get through 5 days of clouds to have 97.5% solar fraction)

In the first two cases, there is some advantage to building a small house. In the latter two, less so, because if the solar thermal (heating & hot water) is sized appropriately, then who cares how big the house is! The sun is free!

From what I can tell so far (our 1-year experience), here are the problems with small/ish houses:
1. It might mean you are building/buying something a little weird or not typical. So if you are unsure how long you will be there, resale could be an issue untill we get to the point that people are generally drooling over superinsulated homes.
2. If you have little kids (and especially if you are in a cold climate and/or don’t live in cohousing with a big shared common house) you might go a little bonkers if you don’t have room to let them run around in circles.
3. Stuff. Junk. Accumulation. (And see #2 if you buy your kids too many useless toys)
4. A smaller sun-facing wall/roof means less room for solar panels.

So, if you are going to build small and have kids, there is some advantage (I think) to building on as few stories as possible. Ignore the “a cube has the least surface area” business. It’s not worth worrying about (too much) if you have kids. Don’t waste room with hallways. But try somehow to have a loop! Keep lots of rooms. Just make them smaller. Don’t be afraid to use point-source heating. We wimped out a bit and have 4-heads to our minisplit system (one per floor). But it would have worked fine with just 2 certainly. I still like a basement. Nice way to get the mechanicals out of above ground places with views. And room for a solar heated water tank.

That’s the view from here.

Do you have kids and live in a small/superinsulated house? Let me know how it’s going? Right now we have 8 people (4 kids under 6, 4 adults) living in what PHPP calls 1741 sqft TFA (treated floor area). And it’s fine. Beat that! Actually, I bet you could. As we built “up”. Do as I say, not as I do! 😉

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Filed under erik-green, heating with wood, passive house, solar, superinsulation, zero energy home