Controlling Radiant Heat Gain
written on 3/10/06
Of the three types of heat transfer, radiant heat is the single largest type of heat gained by the average home. Studies have shown that up to 90% of the heat gained by a house is in the form of radiant heat. The sun produces radiant heat which travels through the vacuum of space and heats everything on earth.
So why do we build our homes with a large solar collector on top? Why do we attach an oven to the top of our house? The sun can easily heat an asphalt or shingled roof to over 190 F. A large portion of this heat is then reradiated down into the space below creating an oven out of the attic. Conventional insulation does little to stop radiant heat which penetrates though it to heat the ceiling. The insulation also absorbs the heat from the attic space which travels by conduction through the ceiling.
So what can we do about it? Ideally, we would build our homes in the shade of a large tree, but this is not typically possible. One solution is to install a heat reflecting aluminum foil called radiant barrier in your attic space. This highly reflective foil intercepts the radiant heat and reflects it back toward the source. When installed in the attic, the radiant barrier will block/reflect the heat before it is absorbed by the insulation and ceiling. When installed properly, the radiant barrier will dramatically cut down on the radiant heat gained by your home on a warm sunny day. Radiant Barrier stapled up to the roof joists can even reduce attic temperatures up to 30 F. In fact radiant barrier is so effective at controlling heat gain that it is required by building codes in both California and Florida.
Radiant Barrier can help cure a number of comfort issues as well. It greatly reduces the heat you feel radiating down from the ceiling. Your house won't heat up nearly as fast in the summer. This reduces demand for mechanical cooling and saves money on costly utility bills. Upstairs rooms and those "bonus" attic space rooms will be much more comfortable. If building a new house, you can often get by with a smaller AC unit saving upfront cost.
Installing radiant barrier is a bit of a project, but it is very affordable and typically pays back in only several years. In fact many of our customers have realized payback periods of less then one year. Radiant barrier is the single most affordable and effective retrofit option to control the radiant heat gain of your home. Learn more...
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