The Effect of Wall and Roof Insulation on Energy Consumption for Environmental Control in a Small, 225-Square Foot Outside Plant Building

In small unattended outside plant telephone equipment buildings, considerable energy may be expended to operate the air conditioner and/or heater that prevents indoor temperature and relative humidity from exceeding specified limits. An important factor in determining how much energy is used is the amount of insulation in the walls and roof. At high internal heat loads (≫20 W/ft2), which are fairly common in such buildings, theoretical models have indicated that the use of any insulation could actually increase annual energy consumption. This is because the heat cannot easily escape by conduction through the surface during the many hours of moderate outdoor temperature and low solar radiation. The insulation is only beneficial during periods of extreme outdoor temperature and solar radiation. To check the effect of insulation on energy usage in a real building, a series of tests was conducted during 1985 and 1986 on a small, 225-ft2 steel frame building located at Chester, NJ. Initial tests were conducted with no insulation in the walls or roof. Test runs were conducted at several internal heat levels (0, 8, 22, and 33 W/ft2), and six combinations of indoor temperature (68, 80, and 85°F cooling, 50 and 65°F heating). Each test lasted one week with two scans per hour to ensure a good range of outdoor temperature and solar radiation. Later, normal insulation (i.e., 2-inch thick polyurethane, R-16) was added and the test series repeated.