More Energy Myths
Energy-saving tips that you can safely ignore
Energy myths are persistent, in spite of the fact that energy experts spend a good deal of time performing debunking duty. Many energy experts collect misguided energy-saving tips as a hobby, and pick the myths apart with the dedication of an 18th-century amateur scientist.
In a previous blog, I presented my own list of ten energy myths. My collection included these old chestnuts:
- Walls have to breathe.
- Caulking the exterior of a house reduces air leakage.
- R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. tests only measure conductive heat flow.
- In-floor radiant heating systems save energy.
Two other myth-collecting hobbyists are Rick Diamond and Mithra Moezzi, researchers at Lawrence Berkeley National Laboratory. They presented their list of energy myths in a paper, “Revealing Myths about People, Energy and Buildings.” Here are some myths they shared:
- Cleaning the refrigerator coils improves refrigerator efficiency. According to Diamond and Moezzi, “A review of measured tests with refrigerators showed that there was no or little evidence of improved efficiency from cleaning the coils (Litt, Megowan, and Meier 1993).”
- Installing foam gaskets in electrical outlets will significantly reduce air infiltration. Diamond and Moezzi write, “The probable origin for this myth — an unusual case where an origin can actually be identified — was a study in the late 1970s that showed that 20% of the air leakage in fifty homes was due to wall outlets (Caffey 1979). Later studies showed leakage values for outlets to be under 1%.”
When it comes to energy myth debunking, Michael Blasnik leads the pack
While many writers have assembled similar lists, one myth debunker stands head-and-shoulders above his peers: Michael Blasnik. A researcher and statistician with a steel-trap mind, Blasnik takes nothing on faith. His approach is always the same: “Show me the data.”
A featured speaker at many conferences, Blasnik has presented different versions of his energy-myths collection over the years. Although GBAGreenBuildingAdvisor.com has highlighted Blasnik’s myth list before (see, for example, Rob Moody’s August 2009 blog, “How Not to Save Energy”), the myths that Blasnik mentions keep popping up regularly and therefore bear repeating.
Here's a selection from Blasnik’s myth list:
- Annual furnace tune-ups save energy. To debunk this myth, Blasnik quotes several studies, including one from Oak Ridge National Laboratory: “The approach of tuning up all units as a standard practice … is costly, probably unnecessary, and likely does not produce energy savings in many units.” Blasnik concludes, “Heating systems with savings potential are apparently too rare to make this approach worthwhile as general advice.”
- Annual air-conditioner tune-ups save energy. The problem with “generic” tune-ups, Blasnik notes, is that “most HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. technicians don’t know how to measure air flow or refrigerant charge.” That’s why “researchers have found more problems in regularly serviced units.” Blasnik admits that a “high-quality” tune-up could save you energy; the problem is that high-quality technicians are very rare. “Even quality tune-up programs face the challenge that only a certain fraction of units provide good savings opportunities, while most units are operating close enough to correctly,” says Blasnik.
- Caulking and weatherstripping can save significant amounts of energy. Blasnik says, “Repeat after me: attics, basements, garages, and details are the real air leakage problem areas. Routine weatherstripping and caulking are likely to save less than 3% of your energy bill. … The savings will be unnoticeable in most homes.”
- Window replacement is a cost-effective energy retrofit measure. Blasnik notes, “When it comes to energy used for heating, savings are often overestimated. Reduced solar gain offsets about half the savings. When it comes to energy used for cooling, solar gain can represent half the cooling load, and low-SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. glass can reduce this substantially. But the measure is still not cost-effective.”
- Closing hot-air registers in unused rooms saves energy. To debunk this myth, Blasnik quotes a study performed by Iain Walker, a staff scientist at LBNL: “The results of this study showed that register closing led to increased energy use for a typical California house over a wide combination of climate, duct leakage, and number of closed registers. The reduction in building thermal loads due to conditioning only part of the house was offset by increased duct system losses, mostly due to increased duct leakage.”
- Right-sized furnaces save energy compared to oversized furnaces. Actually, modern high-efficiency furnaces have very low off-cycle losses, and therefore operate efficiently under part-load conditions. Blasnik says, “There is very little data to suggest significant energy savings from ‘right-sizing’ equipment. I'm certainly not in favor of large oversizing, due to issues with noise, duct sizing (undersized ducts are even more undersized when you install a larger capacity unit), equipment size/cost, etc. But I wouldn't worry about going up to the next size.”
- Using ceiling fans in winter saves energy. Blasnik notes simply, “There is no evidence of any benefit.” (For an in-depth discussion of this question and a debunking of the fan-reversal myth, see Using Ceiling Fans To Keep Cool Without AC.)
Blasnik has several other examples of energy-saving recommendations that result in zero or trivial savings. These include:
- Always put a lid on your cooking pot.
- Change your furnace filter monthly.
- Keep the refrigerator full (or add water bottles to a half-full refrigerator).
- Close your curtains on winter nights. (This advice only makes sense if your curtains include a mechanism to seal the perimeter of the curtains, including the top, to prevent convection currents).
These measures make sense
At most of his presentations, Blasnik balances myth-debunking with a list of energy retrofit measures that are actually useful. He recommends:
- Insulate your walls if they are uninsulated.
- Insulate your attic if it is uninsulated or poorly insulated — but only after completing air sealing work on the top side of your ceiling.
- Hire an experienced contractor to perform blower-door-directed air sealing work, ideally with the help of an infrared camera.
- Seal the seams of any ducts located outside the thermal envelope of your home.
- Swap your incandescent bulbs for CFLs “wherever feasible and accepted.”
- Install high-efficiency appliances and HVAC equipment.
Some energy-saving tips are simple actions that don’t require any retrofit work. According to Blasnik, the following actions are well worth considering:
- Lower your thermostat setting.
- Set back the thermostat when you’re not home.
- Unplug second refrigerators and freezers.
- Make sure your furnace blower isn’t on all the time. (It should be set to “auto,” not “on.”)
Do you collect energy myths?
Calling all myth collectors: if you have some myths you'd like to share (and debunk), post them below.
[Author's note to classical scholars: Yes, I know that the word “myth” is not synonymous with the phrase “fictional story” or “common misunderstanding.” Thor and Aphrodite are more than lies; they are archetypal figures that govern our subconscious desires. So there is no need to send me an e-mail pointing out my error. I hereby plead guilty to intentional misuse of the word “myth.” I'm sorry.]
Last week’s blog: “BEopt Software Has Been Released to the Public.”
- Mark Florence
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