Roughly half of the energy used in your home or business goes to heating, ventilating, and cooling, known as your HVAC system. You can reduce energy consumption and out-of-pocket expenses by adopting a few easy, low-cost tips; by acquiring energy-efficient appliances; and by properly operating and maintaining them. Below is information assembled from various sources, tailored for Johnson County heating and cooling conditions.
Fans
Fans don’t actually cool the air but, by getting the air moving, they will make you feel cooler. They will also circulate and mix warm, stagnant air with cooler air.
- Furnace fans. Turn your thermostat to “fan only” (when the heat or cool system is turned off) to circulate cool basement air throughout the house.
- Box fans can be used both as exhaust fans to blow hot air out through your windows or, when outside air is cool, to blow the cool air in. Box and other fans can be set beside cool air vents or air conditioners to speed up the cooling process.
- Ceiling fans create a breeze to cool your skin. They should be set in a counter-clockwise rotation in the summer to pull warm air up and in a clock-wise motion in winter to blow warm air down.
Whole-house fans can ventilate and cool a house with a fraction of the energy and far less cost ($200-300 versus $2000-4000) than air conditioners. These fans are set into the ceiling of the top floor, where they pull cooler outside air inside through open windows, push hot air into the attic and out through the vents. As stated above, fans do not cool or dehumidify the air, so operating them on a hot and humid day will not provide much relief. Tips on evaluating your home for a whole-house fan can be found here.
Air Conditioning
Window Units
If you plan to air-condition a relatively small place, window or wall units might be a good choice. They are readily available at competitive prices, can cool spaces from 100 SF to 650 SF efficiently and relatively quietly. Air conditioners work by absorbing hot air inside your house, cooling it, and then transferring the heat outside and circulating the cooled air back into the house. Some disadvantages of window units are (1) you lose a window and gain a security risk; (2) installation can be tricky without external support; (3) water drips outside can be a problem.
Central Air
Unlike single-room units, central AC systems cool air in a central location and circulate it though supply and return ducts throughout the house. Some AC system are split into two components (one outside and one inside); others are packaged units that sit outside and are often combined with an electric or natural gas furnace. Central AC dehumidifies and filters the air, improving indoor air quality. It is quiet, out-of-the-way, and convenient to operate but it is also much more expensive to install ($2000-4000) and operate. According to US DOE, the average central AC system consumes more than 2000 kW hours of electricity per year, causing power plants to emit about 3,500 pounds of carbon dioxide.
Mini-Splits
Mini-splits could be considered half-way between a window unit and central air conditioning. They are small, duct-less air conditioners that are split between an outdoor compressor and one or more indoor condensers/air handlers, either mounted or free-standing. Multiple condensers, each with its own thermostat, allow you to target cooling different zones of your house. Mini-splits are quieter and less intrusive than window units and, although more costly than a single-room window- or wall-mounted AC, they’re much less expensive than central air-conditioning. Mini-splits are easier to install and are more energy efficient because they do not require ductwork.
Best of all, mini-splits provide both cooling and heating. Essentially, they are heat pumps, which operate more efficiently than either conventional air conditioners or furnaces. Excellent information about mini-splits and heat pumps, including how to size them for our area, can be found at HomeTips.com
Cooling Tips
There are many no-cost ways to prevent heat buildup in your house.
Adopt these common-sense habits to keep your house cooler and reduce air-conditioning bills for most of the summer.
- Avoid heating up the house by turning off lights – incandescent lightbulbs are hot! – and electronics when not in use.
- Avoid using the stove during hottest part of day. Use exhaust fan to draw heat out when cooking.
- Close window blinds and curtains during day, particularly when sun is beating on them.
- The old “farmhouse” method of keeping a house cool is by opening and closing windows to pull in cool air and keep out hot air. Open windows at night-time and then close both windows and doors by mid-morning to prevent hot air from entering. You can also cool your house by increasing cross-ventilation -- open windows on opposite sides of the house or room. Stagnant air warms up, moving the air around will significantly cool it.
- Another trick is to close all windows except a north-facing window in the basement and a south-facing window on highest floor. Place a box fan (facing outward) in the south-facing window. The fan will function as an “exhaust”, sucking air hot air from the house and pulling cooled basement in to replace it. A ceiling fan (rotating counter-clockwise) near the basement door speeds this up.
- If you have skylights or transom windows, open them to let out super-heated air and create cross currents.
- Use weather-stripping, caulking, and insulation to prevent hot air from seeping in and cool air from seeping out through cracks and crevices.
- Cold air return in basement – is this a good idea to cool house and prevent musty smell in basement? ASK Martha and GT.
- Plant trees for summer shade and winter buffers.
- Contrary to belief, it is more efficient to raise or lower the thermostat when you’re gone rather than maintain a steady temperature in the house. If you are gone during the day, install a programmable thermostat so that the house will start cooling an hour before you return. Leaving the AC run all day is a very inefficient way to keep cool and is very costly.
- Use fans with AC. Instead of cranking up the air-conditioner to cool down a room, place fans near a window unit or air vent to speed up and maximize an air-conditioner’s cooling effect (and at less cost).
Websites We Love
Looking for more in-depth information? Here's a curated list of websites we love to help you answer all your home heating and cooling questions:
Home Cooling with Energy Savers - US Department of Energy
For Everything Central Air - Energy Savers, US Department of Energy
Mini-Splits - HomeTips.com
Use Your Fans Effectively - Energy Savers, US Department of Energy
The Most Efficient Central Air on the Market - Energy Star