re: erv selection criteria
16 may 2002
donna d. walker wrote:
>we are doing an extensive remodel (back to the studs) of a home
>originally designed as passive solar. we are strongly considering
>adding an energy recovery ventilator but are at a loss as to how to pick
>the "right" one...
it seems to me that most homes don't need ervs, because the natural air
leakage is already sufficient. ashrae's standard is 15 cfm per occupant.
air leakage is measured in house volumes per hour (ach), and it is rarely
less than 0.5... 0.5x32x32x16 = 8192 ft^3/h or 136 cfm for a 32'x32'x16'
house. the humidity in a perfectly airtight house would build to 100% over
time as each occupant evaporates about 4 pounds of water vapor per day
by breathing, washing, cooking, cleaning, and so on. you might use a
ventilation fan controlled by a humidistat set at 60% rh instead of
an hrv, and find that it very rarely turns on...
you might do this even in a perfectly airtight solar house, and add the
energy needed for ventilation to the solar heating budget. ervs seem
complicated and expensive by comparison.
for more information, you might look at the superinsulated home book
by nisson and dutt or superinsulated houses and air-to-air heat
exchangers by william shurcliff.