Low-Tech Building Techniques for Energy-Efficient Housing the house temperature will drop slowly if there is an interruption in the supply of heat. If the house is exposed to solar gain and reaches 72 degrees Fahrenheit after a typical sunny winter day, the temperature of the house still will be in the 60s the following morning if the overnight temper- ature drops to 10 degrees. This is a particu- larly nice feature for people who heat with wood, as they need not light an evening or overnight fire. Active-solar systems, sunspaces, green- houses, and even added mass for passive- solar heating are not cost-effective ways to reduce heating costs in climates such as that of northern New