Insulation methods for big windows

The small office building where we sell equipment has floor-to-ceiling windows around its 50-foot display room. In an effort to reduce the air-conditioning load we glued half-inch-thick Styrofoam-brand insulation to the glass and then put Masonite board against it. We've tried several adhesives and none has worked. Do you have a solution? Denison Neale Valdosta, Ga.

First of all, Dow Chemical Company does not make a half-inch Styrofoam- brand panel. The least thickness is three- quarters of an inch. so perhaps you used an expanded polystyrene beadboard or some other brand of insulation.

Dow says it has developed an adhesive called Mastic No. 11 which it recommends for its Styrofoam-brand insulated board. It will not attack the foam , the company says. However, whether it would work on the product you are using , I can't say. Also, it may or may not adhere to glass.

An epoxy adhesive would, however, stick to the glass but it will attack any kind of foam board.

What you could do is coat the glass with an epoxy and allow it to dry until hard. Then you could try to bond the foam insulation to the epoxy on the glass.

An alternative plan, of course, is sand- blasting the glass. In that case, the adhesive would have something to hang onto instead of the hard surface of the glass.