Outside insulation

A few weeks ago Bruce Morgan of Annapolis, Md., wrote in, suggesting that insulation on the outside of a concrete-block house might be better than installing the insulation on the inside, as recommended by Mr. Holly.

Here is Mr. Holly's response:

Insulation between furring strips on the inside of a block wall is the conventional method. We are unaware of a rigid-sheet insulation which is usable outside and would be economical, aesthetically acceptable, have an adequate R-factor, and be unaffected by the weather.

Wet insulation loses some of its effectiveness.

One residential-construction consultant, employed by a national insulation manufacturer, comments: ''From a thermal-performance standpoint (heat loss/gain) , the coefficient of heat transmissions (U-factor) is the same for the wall section regardless of whether the insulation is applied on the interior or exterior of a concrete-block wall.''