If 1/4-inch plasterboard is installed over an insulated wall, then how long does it take the sunspace to get the plasterboard up to the sunspace’s operating temperature? How much does the extra mass detract from the performance?
Quarter-inch plasterboard weighs 1.2 pounds per square foot and has a specific heat of 0.26 Btu/lbs.•°F. It takes 20 Btu per square foot to warm the plasterboard from its overnight temperature of 40°F to its solar-operating temperature of 100°F [(1.2 lbs./ft.2)(0.26 Btu/lbs.•°F)(100°F – 40°F)]. If the sun is shining on the plasterboard at more than 200 Btu per square foot per hour, theoretically it will only take about six minutes to get the plasterboard to 100°F. (In real-world situations, it takes a little longer because there is more total wall/back roof area than there is glazed area.) You would probably not lose more than half an hour of collection time in the morning if thin plasterboard was used in the sunspace.