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Handling Heat Gain in Your Home, From Top to Bottom

The sun's warmth that radiates into your home through windows, skylights or glass doors is called solar heat gain, and in Chicagoland's winter months, can feel warm and cozy. In mid-summer, however, the heat gain from these sources, as well as outside heat entering your home through air leaks and poorly insulated walls, ceilings and attics, can make your air conditioner work overtime to maintain your home's comfort level. That means more wear and tear on the system and more maintenance and repair costs, not to mention, increased utility bills. You can control energy costs and make your home more comfortable by knowing the areas where heat comes in and taking steps to minimize its effect.

Sources of Heat Gain

  • Inefficient windows account for about half of the heat transfer into your home, and the obvious quick fix for that is to have all your windows, glass doors and skylights replaced with energy efficient ones that are triple-paned, thermal insulated and promise to block UV rays. It's a great home investment, but let's face it, many homeowners would have a difficult time working that expense into their household budgets. There are other ways to lower heat gain through windows until replacement becomes a feasible option.
  • The attic, if not well insulated or ventilated, is another way heat can seep in. Temperatures can build up to well over 100 degrees, and if there is little insulation to trap it, the heat will permeate right through your ceilings.
  • Poorly insulated exterior walls, including the wall into the garage, allow heat transfer into your living space. On a hot day, put your hand on an exterior wall in your house, and if you can feel warmth, then it stands to reason that you are paying to cool the air that is subsequently being heated back up from outside.
  • Air leaks in and around pipes, vents and through small holes in floors, walls and ceilings, can push hot, outside air in, mixing with your conditioned air. 
  • Minor sources of heat gain that may not be easily controlled are humidity, the number of people in a space and the heat generated by appliances.

Economical Solutions to Reduce Heat Gain

There are a number of ways to reduce heat transfer, many of them taking only a small amount of your time and money. Your HVAC contractor can conduct a home energy audit to help you identify, among other things, areas where heat gain is a problem. Then take on one or more of the following projects in a weekend and begin to see immediate energy savings.

Treating window surfaces - Not only do unprotected windows radiate heat into a room, but damaging UV rays can fade window coverings and furniture fabrics. The following ideas can be used to lower the amount of heat coming in to your home. The benefit of most of these solutions is that you can still allow natural lighting, also called daylighting, into your living space for a free lighting source as well as more aesthetic appeal.

  • There are various products at your home improvement store that can be applied to windows that will improve the heat resistant qualities. Some glazing or reflective films work well and provide privacy, but at the cost of less light coming in. There is newer, spectrally selective glazing on the market that will block infrared wavelengths but still let in visible light.
  • High quality blinds or indoor (and outdoor) shutters and awnings are other options for blocking UV rays. They are versatile, offer a variety of textures, grains or fabrics, and can be opened once direct sunlight is no longer a factor. Some models are programmable to open and close based on the time of day.
  • A well-placed shrub, tree or other landscaping outside a window that receives direct sunlight can diffuse the harmful rays with the added perk of enhancing your view.

Sealing air leaks - Repairing air leaks in your home is an excellent way to improve its energy efficiency, not only by reducing heat gain from hot outside air, but in all aspects of home comfort. You can save as much as 10 to 20 percent of heating, cooling and related costs by sealing areas where either conditioned air is escaping or outside air is seeping in. Armed with acrylic latex caulk, expanding spray foam, mastic sealant and/or metal tape, go through your house and inspect the following areas for potential air leaks:

  • The attic, by its very design, is a major contributor to air leakage. It may be unfinished and can include dropped ceilings and open stud cavities where the roof meets the walls. Vent, exhaust and fan mountings or shafts for pipes could be leaking outside air. Look under the existing insulation. If it is dirty, it is likely that outside air is getting through. It is also good to note that an attic that is not well-ventilated and insulated will overheat, causing more problems than just heat gain through your home's ceilings. There is also the possibility of moisture buildup, damaged roof shingles and ice dams forming during the winter.
  • Unfinished basement areas, especially around the foundation and rim joists, may not be airtight. A spray foam in these cavities will stop outside leakage much better than traditional rolled insulation.
  • Inspect any pipes or vents coming into the house from outside, caulking gaps or holes. The space around outside faucets is another spot to check.
  • Framing around windows and doors should be caulked. If your floors are above a slab or uninsulated garage or crawl space, sealing around baseboards, switch plates and electrical outlets can be helpful too.
  • All exposed ductwork should be sealed, especially if it is located in unconditioned space such as the attic or crawl space. Looks for gaps or leakage around supply and return registers as well.  

Adding Insulation - Once you have sealed up any holes and leaks, go back through your house and assess your insulation needs. Your attic floor's insulation should be between 12 and 15 inches thick to effectively decrease heat gain. You can add to the existing insulation in your attic and basement or crawl space areas without removing the old insulation.

Putting additional insulating material into the exterior walls of your house is time consuming, but if heat is coming in that way, it is well worth your time and effort to take on this project (or have it done). The least invasive methods are to spray in either foam or loose-fill insulation. Besides curbing heat transfer through the walls, a benefit to a well-insulated home is the reduction of noise pollution from outside.

Reducing heat gain will make a noticeable difference in your home comfort. Additionally, your air conditioner will run more efficiently and your energy costs will go down. That's not a bad return on your investment of time. And a footnote on that warm and cozy feeling you get by the window on a sunny winter's day? When the sun isn't shining, warm air is escaping out that same, poorly insulated glass (and other problem areas mentioned). Heat loss in the winter is just as costly a problem as heat gain in the summer.

If you would like more information on minimizing your home's heat gain or other ways to reduce energy costs, contact the professionals at We are your neighborhood heating and cooling experts.

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