James Stevenson, Energy Educator
After one of the warmest winters on record, making for some wonderful weather here in Central Florida, we are now moving into the expensive cooling season. In our area, Heating Ventilation and Air Conditioning (HVAC) accounts for 40-50% of our utility bill. If a system is not working efficiently, that could be considerably more. How can you reduce the pressure on your AC system, and how do you address your AC’s efficiency level? The University of Florida has answers for residents in our region.
Let’s begin by reminding ourselves that our homes are a combination of structures (the physical building), systems (Heating, Cooling, Plumbing, Electric) and finishes (paint, carpet, furnishings, etc.). These components all affect each other in various ways. Appliances, lights, entertainment systems all add heat to the interior of our home. The combined effect is an increased “cooling load” or burden on the AC to keep things cool. In addition, windows allow the sun’s rays to enter the house and increase the temperature of all the objects they strike. This is similar to what happens when you park your car in the sun. The rays enter and increase the surface temperature of your car’s interior—making it much hotter inside than out.
How can we minimize the pressure on an AC system? Using the two examples above, simple steps would be to switch from hot, incandescent lighting to a cooler compact fluorescent light (CFL) or an even cooler light emitting diode (LED.) An incandescent bulb can heat up to between 200ºF-400ºF (source: Kirk’s Fire Investigation, 4th Edition, 2001.) The average home has 45 of these bulbs; you can see how that could impact the indoor temperature significantly.
Keep the sun’s rays out by drawing the blinds during the day, especially the east and west-facing windows. When it is time to replace your windows, choose windows that help keep the heating rays out and insulate against heat loss in the winter.
Another source of heat in the home is heat that gets in from outside. The obvious way that heat can enter is through open doors and windows. But the home’s envelope can be riddled with tiny holes and cracks. The sum of these tiny openings to the outside is the same as constantly opening a window! Examples of places to look for openings include: electrical penetrations through the wall, the dryer’s exhaust, recessed lights, gaps around windows and doors, plumbing vent stack, etc. Seal these cracks and gaps with weather-stripping, caulk and expanding foam, depending on the situation. According to a study done at UF, a Saturday Morning Makover, sealing gaps and cracks as described resulted in an 11% reduction in leaks. That is $30 invested and 4 hours of labor.(Source: John Linhoss, University of Florida.)
Attic insulation is a major barrier to heat gain from that hot place. Do you know your insulation’s R-Value? R-Value is the insulation’s Resistance to the flow of heat. The greater the R-Value the better it insulates against heat gain. UF recommends an R-Value of at least 38 for our area, (source: Insulation for Your Home; Florida Energy Systems Consortium, 2010.)
Next week we will explore ways to keep the HVAC system itself running as efficiently as possible.
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