Henry Gifford Interview Part II: PassivHaus

Yesterday, Henry Gifford talked about some the flaws in our current green building certification standards.  Today he talks about a new standard for energy efficiency in buildings, PassivHaus, which has been in Europe for some time, but is new to the US.  The PassivHaus standard results in ultra-low energy buildings that require very little energy for heating and cooling.

JW:  You are one of the first graduates of the US PassivHaus class.  Tell us more about PassivHaus and how it will change American building design for the better.

HG:  PassivHaus is catching on slowly here but I think it will be much more popular in the future.

JW:  Just how energy efficient is PassivHaus?

HG:  The houses cannot have a peak heating load exceeding 10 watts per square meter, which if you think of putting a few light bulbs around to heat your house on the coldest night, is a really small amount of energy.  [By this calculation, two 100 watt bulbs would heat a 215 square foot room, such as a bedroom.] 

JW:  Is PassivHaus green in other ways?

HG:  A PassivHaus is also green in that it is very airtight – no more than 0.6 air changes per hour when depressurized to 50 pascals – which prevents mold growth from air leaking through walls, which improves people's health while also making the building more durable.  The airtightening also allows the ventilation system to work as designed, moving air as planned instead of through leaks, while also improving thermal comfort (no drafts) which lets people stay comfortable at a lower temperature.  As a bonus, the airtightening also makes the house very soundproof.

JW:  Is a PassivHaus expensive?

HG:  PassivHaus buildings generally cost more than normal construction, but there can be exceptions, particularly with larger buildings.

JW:  Can an existing building be made into a PassivHaus?

HG:  No, sorry, an existing building cannot be made into a PassivHaus without a complete renovation.  And, as the foundation and basement floor need to be insulated, even saving the foundation is questionable.

JW:  Where can we see a PassivHaus in the US, and where can we learn more about PassivHaus?

HG:  There are now PassivHaus buildings in Urbana, Illinois, Martha's Vineyard, Duluth, Minnesota, and one in California, but in California the climate makes it so easy it's really not that difficult there.  Passive House Institute US (PHIUS) just put out a book about some houses I didn't mention here, and can tell you more.

Photo is of Henry Gifford's "tendem" bicycle, which he and his brother built in the 1970s.