Our house vs passivhaus / passive house

BTW, as a followup to my last post. Our house misses the passivhaus PHPP standard for Specific Space Heat Demand.

= 4.75*1000*1741/(3412) = 2423 KWh used per year is what the PH Certificate requires as a max for “Specific Space Heat Demand” (for our 1741/sqft TFA)

Give that we *used* an estimated 2300 KWh (2338) for heating, and given we can estimate our (non hyperheat/h2i) heat pumps at 2.25 COP overall (as a 15% adjustment from the “North Carolina” temp zone rating–I think I looked up once for our unit’s seasonal HSPF… 15% adjustment: as they seem to do in Canada since the COP is temp dependent.)

That would be:

5260 KWh of actual heat *delivered* from the 2338 KWh our minisplits *used*.

So we are 1/2 or 1/3 as good as a passive house I guess. Probably 1/3 since it was a mild winter.

So you can see why people think passivhaus might be extreme. We are talking about $350 (our house) vs $120 (a similar-sized passivhaus) in heating given $0.15/KWh electricity. I still think it makes sense, especially since people are getting practiced at doing it panelized/modular. (See Green Mountain Habitat for Humanity in VT for example.)

– roughly 68F max in winter, roughly 78F max in summer
– I should do a per HDD calc

FUDGE FACTORS (+ or -) in my “1/2 or 1/3 as good as a Passivhaus” calc:
– Weather/climate in PHPP is a 30-year avg. This 2011/2012 winter was mild.
– COP of our heat pump is a guess (maybe I guessed way too low?)
– Previously mentioned guess for % (10%) of heat used for hot water heating
– Some inaccuracy of the emonitor device (vs direct submetering)
– Any errors made in the PHPP (our house used a number of non-certified products… windows, HRV so guesses had to be made)
– Related to above… our windows and HRV are also not as efficient as those typically used in a passivhaus.

That said, obviously there are some houses that don’t use Passivhaus” equipment — like this one — that do MUCH better than the PH standard. Occupant behavior matters a lot.


Leave a comment

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

Comments are closed.