When cooling a house, it is helpful to first understand the science of heating and cooling. Here are some variables that affect the heating and cooling of our homes during the summer months:
Air Movement: Air moving into the house can bring in warmer air. Keep doors and windows closed if the outside temperature is higher than the inside temperature. This varies by direction as the north side of a house often has air temperatures 10+ degrees cooler than the south and west sides on sunny days. Moving air, even if it’s warm air, can also give a sensation of cooling as it passes over the skin. Therefore, do not be fooled and remember to keep the windows closed.
Radiation: Light waves (sun rays) carry energy that can heat objects. Block the sun by closing windows and shades during daytime hours. Lightly colored and reflectively coated shades and drapes can block far more of this energy and related heat. Roofing materials and exterior siding can stay cooler if reflective colors and coatings are selected. Shade trees especially at the south and west side of a home can provide huge relief from radiant heat. In addition, shade trees are actually a bit like primitive air conditioning units as they also transpire. This means that moisture is released from the tree leaves through evaporation, thus cooling the leaf surface and therefore the air around the tree. Some trees grow as fast as 6-8 feet per year, so plant them now!
Exterior Mass Materials: Heavier and denser materials can generally store more heat, which is then released as the air temperature becomes cooler than the material. If, for example, you have a driveway or sidewalk near the south or west side of the house, this will absorb a lot of heat during the day and can reach temperatures that exceed the air temperature. When night comes and the air cools, the concrete then releases its heat for hours into the night and potentially until you wake up. Windows located above these mass materials often draw in much warmer air than other windows around the house. Darkly colored mass materials, such as asphalt drives and walks or even a lower-level porch roof with asphalt shingles, retain heat even more. Other items with heavier mass can include stucco or brick wall claddings, concrete foundations, vehicles, and landscaping stones. Shade these items from the sun or make them more reflective.
Humidity: Humidity is the amount of water vapor in the air. The higher the humidity, the more uncomfortable it feels. Higher humidity slows the rate of perspiration and the natural cooling of your skin. If the cooling methods above still leave you feeling miserable, it’s likely due to humidity and there is not much else you can do other than sparingly use your air conditioning. A dehumidifier will likely not help much as it too can give off heat while removing moisture from the air. Minimal use of air conditioning can be accomplished by running it only sparinglyâ€”just after work and while sleeping. Try to keep your air conditioner turned off during the day while also keeping the windows closed in order to keep the cool air inside. Note that oversized central air conditioning units are often installed and have a very hard time removing humidity. Thus they can be ineffective and even more inefficient.
Living Habits: Cooking can be a big contributor to heating a home. On hot days, switch to foods that do not need cooking or use an outdoor grill. Always use a kitchen exhaust fan for any indoor cooking even if it’s just running the toaster. Utilize the exhaust fan for 30â€“60 minutes after cooking as most ovens, stoves, and toasters continue to emit heat well after they are turned off. When showering, run the exhaust fan for up to 60 minutes to help prevent the humidity and heat from increasing.
Attic Temperature: The sun heats your attic significantly and in doing so contributes to the excessive heat of your home’s upper-level ceilings. Insulation may help prevent some of the increased stored heat, but proper attic ventilation should be added as well. Some building scientists have found that the reflectivity of your roof is an even bigger factor in reducing the high temperatures in your attic. There is even an option of installing attic fans that may be activated by a thermostat. However, there are some risks with these fans. They are located on top of your roof and may add another place where water can leak. In winter, a malfunctioning thermostat could make the fan run excessively even though it’s cold outside and this could potentially pull valuable heat from your home.