Air Tighten with Care

A misunderstanding has apparently occurred over one of my statements in Moisture and Mobile Home Weatherization (HE July/Aug '95, p. 29). I mentioned that many weatherization measures will make the house more airtight, and that could cause moisture problems. I gave as an example the use of dense-pack cellulose wall insulation; however I did not mean to imply that it should not be installed. I am strongly in favor of the use of dense-pack cellulose in walls because it does a good job of insulation and also reduces unwanted air leakage. It is because it typically does such an exceptional job of reducing air leakage that it must be used with care. Whenever any air sealing measures are installed, a procedure should be followed to assure health and safety, including: (1) a SunPower or COAD-type combustion safety testing protocol, (2) source control strategies for excess moisture and other pollutants, (3) installed mechanical ventilation capacity whenever the measured cfm50 is near or below the building tightness limit or there are high levels of contaminants. In no case should any weatherization involving direct or indirect air tightening be undertaken in those few older mobile homes with an exterior vapor retarder until remedial actions are taken.

George Tsongas
Portland, OR

Closet Reasons to Install CFLs

I discovered an unexpected justification for use of compact fluorescent lights, which turns conventional wisdom about where CFLs are and are not justified on its head. Recently we sought to install a light fixture in a closet. The electrician informed us that the building code (National Electric Code) forbids the installation of an incandescant light fixture less than 18 inches from a shelf, which was the situation in our closet (and probably in most other closets). To meet code, we would have had to reset the fixture into the plaster ceiling at great cost. However, a compact fluorescent light is acceptable because its heat production is within the safe limits. Here is a case where energy efficiency reduces first costs, even when overall energy savings are small.

David Goldstein
San Francisco, CA