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Passivhaus total energy usage standard

One of the Passivhaus standards is that total energy usage including appliances cannot exceed 11.1 kwh per sq. ft. per year. If I have a 2800 square foot house, then if my total kwh usage is under 31,080 (11.1 x 2800) that is pretty good right?

Seems like that's a pretty low bar. Or am I misinterpreting?

Thanks,
JImmy

Asked by Jimmy Nguyen
Posted May 11, 2017 8:18 AM ET

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7 Answers

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1.

Jimmy,
The Passivhaus target you cite is a primary energy (source energy) target.

The usual factor for converting site energy (electricity) into source energy is 3.34. (In other words, 1 kwh of site energy = 3.34 kWh of source energy.)

In your case, 30,080 kWh of site energy = 100,467 kWh of source energy.

For more information on the difference between site energy and source energy, see Understanding Energy Units.

Answered by Martin Holladay
Posted May 11, 2017 8:55 AM ET
Edited May 11, 2017 8:56 AM ET.

2.

Yikes. So I need to get it down to 9305 kwh/year to reach Passivhaus standard. Now I see why that's so tough.

Answered by Jimmy Nguyen
Posted May 11, 2017 11:28 AM ET

3.

The Passive House energy modeling program, the PHPP, uses a primary energy factor of 2.6 for grid-derived electricity, and a factor of 1.1 for fossil fuels, likely reflecting the more efficient distribution systems in Europe, compared to North America. The PHPP also measures square footage differently than we typically do in the US. Between the two, you may not be as far off as you think, but it is definitely a difficult (but often worthwhile) target to reach.

Answered by Michael Maines
Posted May 11, 2017 1:46 PM ET

4.

Thanks Martin and Michael.

How do people usually factor in an unfinished basement? I have a 1800 square foot unfinished basement that can still be conditioned via two ductless minisplits. I am predicting that after everything is done, I will have a total primary energy usage (all grid electricity) of 18,840 kwh.

If you only count my current living area (2800 sq. ft.) then I would be very short of Passivhaus standards. (2800 sq ft. x 11.1 / 2.6) = 11954 kwh.

However, if you add in the quasi-living area that is my basement then I would have reached the target. (4600 sq ft. x 11.1 / 2.6) = 19639 kwh.

Answered by Jimmy Nguyen
Posted May 15, 2017 8:21 AM ET

5.

Jimmy,
For purposes of calculating the treated floor area (a PHPP input), use 60% of the basement floor area rather than 100% of the basement floor area.

For more information, see In Defense of the Passive House Standard.

Answered by Martin Holladay
Posted May 15, 2017 10:51 AM ET

6.

Jimmy, to calculate the TFA, in addition to Martin's advice, you also don't count stairways with more than three treads, and you measure to the interior surface of all walls, interior and exterior--sometimes called the "carpeted area." Utility areas other than basements can be reduced in some cases as well, if they're not used much.

Answered by Michael Maines
Posted May 15, 2017 7:28 PM ET

7.

Thanks Michael Maines. Does the standard account for the number of people living in the home?

Answered by Jimmy Nguyen
Posted Sep 12, 2017 12:48 PM ET

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