Latest Discussions : HVAC


04:10AM | 11/14/02
Member Since: 11/13/02
1 lifetime posts
Can anyone help?
We recently moved into a bungalow with a single brick extension (two additional bedrooms) which was added approx 15 yrs ago.
The previous owners had stuck styrofoam insulation to the inside of the exterior walls but this caused a lot of condensation.
A builder 'friend' told us to remove the styrofoam as this was the likely cause and get a dehumidifier. We did both and still get a lot of condensation.
Is there anything that can be added to the outside of the exterior walls to improve insulation and what can aid removing the condensation (eg air blocks?).

Please help a depressed and damp-feeling Brit.


09:46PM | 01/13/03
Member Since: 12/23/02
18 lifetime posts
Your builder friend is giving you bad advice. Styrofoam doesn't cause condensation. Water vapour does. You can use styrofoam anywhere you like, as long as it is the vapour-impermeable type, and well-sealed at the seams, with a drainage pathway behind it. The previous owners must have not known the proper steps to take.
If the dehumidifier isn't helping, it's likely not an inside source of moisture, so it's possible you've got water vapour coming right through the brick itself, and condensing in the warm indoor air. One way to prevent this is to apply insulating sheathing to the ~exterior~ of the building. Styrofoam is fine, as long as it's the blue stuff that won't permit vapour to pass, and is well sealed at the seams.
Then you could stucco right over it. Or you could do siding, if you go to the trouble of applying strapping first.
Alternately, you could put strapping on your interior wall, providing a channel for the moisture to drain through, and drill holes in the outside of the bricks, at the bottom of the wall. Then put blue styrofoam insulation ~over top~ of the strapping (not in between), another layer of strapping, and drywall over it. Be sure to plug up any seams in the insulation, and any bypasses such as electrical boxes. Use spray foam for that.
That would bring your wall out 3 inches, presuming you'd use standard 1x3 strapping (really only 3/4 of an inch thick) and 1 inch of foam, plus half inch drywall. You could also slide another inch of foam between the boards of the second strapping layer, bringing the R-value up to ten. That would keep you toasty warm. :-)


09:15AM | 01/18/03
Member Since: 11/06/02
1278 lifetime posts
Brick is not waterproof. It is just as likely that rain is penetrating from outside. the wall. How do you know that you have condensation? Your 'friend' was definitely wrong. Foam is one of the best cures for condensation acvailable when installed right.

Your biggest problem is that you have half a wall - the exterior - and not the whole thing.


03:57AM | 02/08/03
Member Since: 02/07/03
13 lifetime posts
I wonder if they used a house wrap or roofing paper (aka tar paper) during construction. You are suppose you use roofing paper (15#) on your exterior of wall sheathing (osb, plywood or rigid foam board).
Brick allows water though. Then the sun hits the brick, warms the brick and drives moisture inward. Roof paper is recommended for brick homes because of this. House wrap (typar, Tyvex) is for vinyl exteriors.
This could be your source of moisture.
They are correct, a run off plain (at least 1/4") between the brick and tar paper is a must.

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