Dispelling myths about home energy consumption
February 17, 2008
I have heard that I can overinsulate my house because it needs fresh air to "breathe." Is this true?
This is one of those urban myths we occasionally run into. The term "overinsulate" sounds more like an excuse for not spending time or money on insulation.
Homes cannot be overinsulated, but they can be underventilated. It's true that newer homes that are built to be more energy-efficient can require mechanical ventilation to keep indoor air fresh. But most insulation doesn't block air infiltration. It primarily reduces radiant and convective heat loss. Unless you use the newer spray or foam types of insulation, you should not be at risk of making your home too tight.
Homes typically have air leaks around windows, doors, pipes and cables. We recommend plugging these leaks when adding insulation. The amount of insulation in your attic or ceiling is limited, of course, by the home's structure and design. Wall insulation is difficult to retrofit, and the amount also is limited by the home's existing wall depth.
Here are some other myths we hear from customers:
Myth No. 1: Water heaters must be set at 140 degrees for a dishwasher to clean properly.
Most modern dishwashers have internal heaters to warm the water to a safe temperature. Setting your water heater at 120 degrees is hot enough for a typical family's use. Another energy-saving tip is to only run full loads in the dishwasher and use the air-dry feature. If you only have a few items, hand wash them in the sink.
Myth No. 2: Buying a new heating system will automatically reduce my energy bill.
The heating portion of your energy bill should be reduced if you buy a higher-efficiency model. However, proper sizing and installation has a lot to do with getting the manufacturer's promised savings. An oversized furnace will end up wasting energy. That's why it is so important to deal with a reputable heating and ventilation contractor when purchasing a new system. New heating systems cost enough, so don't spend more money by wasting energy each month. Changing from a zonal heating system, such as wall heaters or ceiling cable heat, can actually increase your energy costs depending on how you use the new system. If you start heating the entire house instead of just some rooms, you may be more comfortable, but that can use more energy.
Myth No. 3: Leaving my computer on uses less energy than turning it on and off.
Not true. The burst of power at start up is negligible. We (along with the U.S. Environmental Protection Agency) recommend turning computers and monitors off at night or when not being used for several hours. That being said, newer computers offer a "hibernate" or "sleep" mode that can be almost as effective in reducing energy use. The "hibernate" feature "powers down your monitor to about 5 watts of energy and your PC to 2.3 watts," according to Microsoft's Web site. Either way you choose to do it, you will be saving energy. In fact, the EPA estimates that 11 billion kilowatt-hours of electricity could be saved just through computer monitor power management. The agency says the savings would have the environmental benefit of reducing carbon dioxide emissions equal to removing 1.5 million cars from the road or planting 2.5 million acres of trees.
Myth No. 4: Leaving my heat running when I'm at work uses less energy than having to warm up a cold house when I get home.
It does not require more energy to bring a room to the desired temperature than to maintain a temperature, so why would you heat an empty house while you're away? We don't recommend constantly turning the thermostat up and down, but it makes sense to turn it down when sleeping or when you'll be away for several hours or more. Our rule of thumb is for every degree you set your thermostat back for an eight-hour period, you save between 1 percent and 2 percent on your heating bill.
