Ask the Architect

The problems water causes


Q. Our attic air conditioning leaked into our ceiling. The ceiling is so wet we need to replace it. We now understand we’ll need to have the pipe that drains water out of our A.C. drain pan blown out every spring, and now have a service contract for that. The insulation is also wet. We were told to let it dry out and it will be fine. Is this true? Also, the ceiling joists over our 12-foot-wide master bedroom are only 2 x 6, which might cause the ceiling to sag and isn’t enough for the insulation, we’re told, which we understand has to be 10 inches thick. When we asked our contractor about this, he told us we can push the insulation down and then replace the plywood floor in our attic. What do you think?

A. When it rains, it pours. The leaking was a wakeup call that A.C. unit condensation occurs every summer season, and even though you have a drain pan, if it doesn’t have a working sensor to shut off before the drain pan overflows and you never clean the drain pan pipe to the outdoors, the water overflows. You should, by law (code), have a floor in the attic around the unit, also, which can dry out, since it remains structural, and will be minimally affected by the water.
The insulation and the sheetrock are another story. If the sheetrock hasn’t loosened and isn’t sagging, then it can just be left to dry out. Make certain, even using a moisture meter, that the sheetrock is completely dry before repainting to avoid potential mildew and discoloration. The insulation, if it is either fiberglass or closed-cell foam, can be dried out also, but only if it can be exposed. This means removing the plywood flooring above so that air can get to the insulation.
In addition, the insulation should be inspected to see that it isn’t compressed by the saturation weight of the water, since compressing insulation, contrary to what you were told, actually takes away the ability for it to work properly. The principle behind insulation technology isn’t just the use of thermally resistant material but, most critically, the insulation forms tiny air pockets within the material that form the resistance to air passing through. Each trapped air bubble slows the transfer of cold or heat by first conducting or resisting the temperature change within the air molecules.
Heat moves by one of three mechanical principles, convection, conduction and radiation. If the air bubbles or pockets in the insulation are pressed closer together and the material made denser by this, the conduction or transfer of temperature is easier, so the insulation has less likelihood of resisting, and resisting is what you want insulation to do. It would be great to rebuild the floor with deeper joists or have closed-cell foam sprayed in, since it also resists water saturation to solve the problem. Good luck!

© 2022 Monte Leeper. Readers are encouraged to send questions to, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.