So, underneath all of these plans for our superinsulated house, is
really just the desire to reduce our “footprint”/our use of fossil fuels as much as
possible AND to do so while spending the least amount of bucks to do so.
(Eliminate would be nice, but I know this is not completely possible.)
The most promising things to do house-wise on this front seems to be:
1. insulate/seal like crazy, use air-source heat pump for heat
2. solar heating for domestic hot water (showers, laundry, etc)
3. low-mass, thermally isolated sunspaces (or vertical air heaters) for daytime heat, maybe some ceiling mass to extend heat to eves a bit
4. storage in water (since it stores 3 times more per weight than concrete) for purpose of…
– replacing #4 (solar hot water heating)
– heat for cloudy days (5 days would be 97% solar heated if “cloudy days are like coin-flips”)
5. grid-tied solar PVs to offset appliance use (and also try to conserve w/ CFLs, turning stuff off, etc)
6. some passive solar tempering thru south windows
#3 and 4 has many supporters. Norman Saunders, Nick Pine, Gary Reysa, Laren Corie,
and I suppose the list goes on and on. It seems to work — 97% solar heated even in New England!
The only question seems to be when it is most cost effective and best at reducing fossil-fuel use
to do #1 and 2 (Passive House, with electric backup) or #3 and 4 (Active Solar).
My sense is that with retrofits, it is more obvious that #3 and 4 (solar) are going to have an edge, money wise, since “deep energy retrofits” seem to be quite expensive and complicated. And perhaps with new construction, #1 and 2 (passivhaus). I mean, it doesn’t have to be a complete either/or decision. With existing homes, it probably makes most sense to do quite a bit of the easy envelope fixes (sealing up with foam and extra insulation in the walls and attic) but after some point, it’s time to add solar air heating, solar hot water heating, and/or solar PVs for appliance use.
And of course, the house is only one part of the equation…
7. it would be good to not drive a car (or less, or electric/hybrid)
8. it would be good to be vegetarian (i’m not at the moment)
9. it would be good to have a vegetable garden and/or local CSA
10. other lifestyle things… working at home vs commuting, flying in planes, composting food waste, composting toilets, water use, the food we buy, the junk we buy, clothesline, etc, etc, etc.
That first one (#7) in particular is an easy one since it doesn’t require major
lifestyle changes, just a prius. If one already needs a new car, it’s sort of
a no brainer that it should be a prius (at least from the number crunching I’ve
done). BTUs payoff (as with solar PV panels) is quicker than $$ payoff. Basically
this is because we are not paying the full cost to our society for the price of fossil
But back to the top list (#1-6). What if doing a passive house was $20k cheaper than active-solar?
If that meant one could then afford to buy a Prius, or replace one’s current car with a Plug-in
hybrid, then despite the extra fossil-fuel use in the home (to heat with a little bit of electricity)
one would then be saving HUGE BTUs on the car side of things.
Granted, a car will not last as long as passive house (“forever”) or active solar (30 years?) so it’s
less clearly a win vs these two. But this illustrates the basic point that one has to think holistically,
across one’s entire activities. Not just house. Anyway tricky stuff.