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Old 01-08-13, 10:35 AM   #7
AC_Hacker
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Quote:
Originally Posted by MarkM66 View Post
It may not insulate as well, but will there be that much of a difference to justify buying new?
...my two cents worth...

> dry rot, termites, black mold...

MarkM66, you have a serious moisture problem that needs to be resolved. If you don't address that, it will come back again, like Nosferatu rising from his coffin, to haunt you and your mother.


I would guess that the walls have many air leaks and the humid indoor air is traveling through the walls and cooling, which causes the moisture in the air to condense in the insulation and provide a warm, dark, wet paradise for dry rot, termites and black mold. Really, MarkM66, your mother deserves better than this.

There are a few approaches to this and you shouldn't limit yourself to just one:

VAPOR BARRIER - After you're done with the insulation, use a good vapor barrier to prevent air from moving through the wall. In the past, plastic sheeting has been used, and that helps.

THERMAL GRADIENT - Either wrap the outside of the house with foam or spray the stud space with about 1" to 2" of foam. Then use a good insulation of your choice in the remaining space. The idea here is that the moist air hits the foam at a temperature above the dew point, and will not drop moisture.

HEAT RECOVERY VENTILATION - This will get the moist air out of the house and save most of the out-going heat to the incoming air, which will be much lower in relative humidity when it is warmed.

* * *

But back to your ventilation quandary...

If you should continue with your plan (attic insulation to walls). You will eliminate the expense and hassle of disposing the old insulation you want to remove. There is also an environmental benefit to re-using the insulation and not being part of the chain of events that would cause new insulation to be made.

There would be some decline in insulation (compared to an 8" wall) but probably not as much as you might think. Packing in the extra insulation would increase the immobilization of the air in that cavity... that's a good thing.

Everything that has been previously said about making air-tight cavities is very important, no matter what you decide.

* * *

But when you get done, you're still going to have to insulate the attic right?

So why not leave the old attic insulation where it is and lay more over the top, and get more 6" insulation for the walls?

(I may have gone beyond the two cents worth limit here...)

Best,

-AC
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