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re: priority for reducing heating costs
31 jul 2005
duncan mcniven wrote:
>hchickpea@hotmail.com wrote:
>
>>a blower is sealed to the doorway and powered on to find out how much
>>the house "leaks" air through cracks and crevases.
>
>is that usually done room by room, or for the whole house at once?
usually the whole house, but you might do it room-by-room, with a window fan.
seal up the first room containing the fan and the pressure gauge, then
open the door and go airseal the next room.
>i imagine it would need a huge fan to deal with the whole house.
depends on the house.
the blower door as we know and love it today springs from technology
first used in sweden in 1977, where it was actually a blower window.
the idea migrated to the united states with ake blomsterberg, who came
to princeton university to do research in 1979...
the princeton researchers decided to mount the fan in a door because door
sizes are more uniform than windows... with the help of the blower door,
the researchers found that hidden leaks accounted for a greater proportion
of air leakage in a home than the more obvious culprits, such as windows,
doors, and electrical outlets--a giant leap forward in our understanding
of how a house operates...
a monster blower door is being used to test large residential and
commercial buildings in canada. the super sucker is a whopping 55,000 cfm
fan [like 55 window box fans] that is 40 ft long and 5 ft in diameter.
it is transported to the site on a flatbed trailer, and it takes a team
of five people [with safety belts?] to hook it up to a pair of double
doors and perform the test.
from: http://hem.dis.anl.gov/eehem/95/951109.html
>i'm trying to imagine this from a practical point of view. i seal a
>room and pump air into it.
or out, or both.
>i then need a pressure gauge to see if the pressure changes...
magnehelic makes one... 0 to 0.25 "h20 (62 pascals), about $50.
>and if not then there is a leak in that room that i need to fix.
>is that right? what sort of pressure gain would be the target?
you might shoot for 4 air changes per hour at 50 pascals,
eg 4x2400ft^2x8/60 = 1280 cfm for a 2400 ft^2 x 8' house.
that's 1280 linear feet per minute (lfm) through 1 ft^2.
>what sort of gauge do i need?
you might use a $150 digital testo velocity stick with a bit of tape over
the slot at the end to reduce airflow and dampen its fluctuations over time.
put the stick in a small open slot in one window, and put a fan in another.
if the room is fairly airtight, the stick will read a high air velocity
through the window. if not, it will read a low velocity, down to 1 lfm.
nick
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