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Posted by JT on February 12th, 1998 08:44 PM
In reply to Old house wall insulation by Bobby on February 10th, 1998 02:03 PM [Go to top of thread]

Bob & Bill, I believe that densly packed cellulose
(3 - 3.5 lb/cu ft) is the best you can get unless
you are willing to open the walls so that foam can
be sprayed that way. The problem with trying to pump
foam throught holes is that it is very hard to insure
converage. Not that it can't be done, but the reality
is that usually it isn't done right. This lack of
coverage shows up dramaticly on an infrared video
camera. Dense packing celulose isn't the most fun
you'll ever have but it is doable. DP cellulose will
form and air barrier thus perventing air from carring
moisture into the walls. If there is high ambient
moisture some will of course enter by diffusion, and
a forced air furnace that pressurizes the house can
also force moisture in to the walls.
Any moisture entering, whether from the outside or inside
will be held by the celluose (wicking it away from
framing and sheathing) and released as the wall
drys to the inside and or outside. At first, you
might think this retention of moisture is not a
good thing. But since the moisture is entering,
it must go someplace, the alterantive is for it to
condense on the sheating and run down to the sole
plate with the obvious consequences. BTW walls
with fiber glass follow the latter path since FG
is incapable of wicking moisture. Of course if there
is so much moisture entering that the wall cannot
dry (or if the wall has no place to dry to because
of finishing material choices) the celulose will
be reach it's limit, but that will only happen when there
is some serious moisture or pressurization problem
that should have been corrected before insulating.
For more info. see For the
experience of a first timer see,
"Weatherization" thread, message "adventures in
denspack" (Feb 11).

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