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More Energy Myths

Energy-saving tips that you can safely ignore

Posted on Nov 11 2011 by Martin Holladay

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 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.”

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Image Credits:

  1. Mark Florence

Nov 14, 2011 3:29 PM ET

Response to Darrin Brightman
by Martin Holladay

You have correctly interpreted Michael Blasnik's point, I'm happy to say. Like you, Michael does not advocate letting food spoil. So by all means, eat the contents of your freezer or second refrigerator before you pull the plug.

All too often, as I'm sure you know, one member of the the household decides that it's time for a new refrigerator. Once the new refrigerator is installed, another member of the family decides that the old refrigerator should be dedicated to beer. This second refrigerator is usually unnecessary and always contributes to high energy bills.

Nov 14, 2011 6:43 PM ET

Edited Nov 14, 2011 8:40 PM ET.

Close your curtains on winter nights. (This advice only makes se
by Chris Lockhart Smith

'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).'
Firstly, this qualification should also include sealing the bottom of the curtains, as most curtain fabricators in our locality make 'to the floor' the curtains hang 5mm off the floor. Without the bottom sealed the curtains are like a bucket with a hole in it.
Obviously sealing the perimeter will improve the efficiency of the window, however to say that closing curtains in winter is ineffective, is I believe incorrect. As heavy drapes + pelmets have a resistance to heat of 0.330m2.k/w they have a resistance to heat flow out even if there are some convection currents reducing there potential effectiveness.
Personal experience has shown noticeable reduction in energy use in winter when we installed curtains(without pelmets or sealed perimeter) and a thermal imaging camera clearly shows the effects of a closed curtain both in summer and winter(and yes I know that it is more effective to shade a window externally rather than internally in summer).
To put it another way convection is not the only way to lose or gain heat.

Nov 14, 2011 8:52 PM ET

Response to Chris Lockhart Smith
by Martin Holladay

I agree that the word "perimeter" includes the bottom of the curtain.

Nov 14, 2011 11:10 PM ET

Refrigerator coils: not cleaning them a slight caution
by Calvin Meier

If studies show that cleaning the coils is not necessary that is fine. Cleaning the coils and general area (under the refrigerator) does help to prevent at least one problem. Whne fan is off, if a glob of accumulated lint falls on the fan blade , it can stop the fan from turning/starting when the refrigerator "kicks" in. Sounds odd? It happened to my refrigerator's fan. The quiet running fan is apparently also not overly strong. Clearning also helps remind me to routinely clean the condensate drain tube :}.

Nov 14, 2011 11:27 PM ET

by Jack Coats

There seems to be a lot of hand waving in these threads, and a lot of 'absolutes' being specified. (Like, it replacing windows is not cost effective, etc.) How about specifying how to calculate how to make the cost/benefit analysis rather than just stating doing various items are or are not 'cost effective'.

Yes, this is the old engineer in me showing up... I guess I was a geek before being geek was cool.

... On the cleaning the fridge coils, well it can't hurt. Try putting a kill-a-watt or similar unit on your appliance for a few days before cleaning and after. Check the difference to see if the power savings is what someone might consider 'cost effective'. It would be one data point, and not enough to extrapolate to a generality, but reporting data points (with information about model, age of unit, etc) could allow collecting enough data so it could turn into usable information over time.

Just some thoughts from an old geek.

Nov 14, 2011 11:39 PM ET

comment on lighting efficiency and some other thoughts
by Dave Williams

Had to add a comment on CFL's vs. incandescent bulbs. When you are heating a home, the heat given from a incandescent bulb helps reduce the heating load. Conversely, the very inefficient incandescent bulb puts an additional load on air-conditioning. My understanding is CFL's have traces of mercury and I know they are difficult to recycle. But if I lived in a cool climate with many months of heating - I would not be too worried about improving the lighting efficiency inside my home. Of course, outdoor lighting like street lamps, should utilize the highest efficiency lighting technology like LED. Never-the-less, the electrical loads found in a home - even a personal computer - ultimately convert their electrical energy input into heat and they do that at 100% efficiency. Therefore, I don't see how you can claim ALL of the energy savings when converting to CFL or LED lighting.

When measuring efficiency - I've always felt that it is important WHERE you establish the system boundary .

Nov 15, 2011 1:27 AM ET

Opening WIndows in Winter
by Chris Richter

As an American now spending time in Austria I find that one area the Austrians have me baffled is energy conservation, specifically the following direction given - that is "open the windows 2-3 times daily in the winter for 15 minutes". Supposedly this improves their energy usage. Nothing in my learning helps me understand this and I've found no proof of this....anyone care to shed light on this seemingly strange idea?

Nov 15, 2011 5:05 AM ET

Edited Nov 16, 2011 11:51 AM ET.

Response to Jack Coats
by Martin Holladay

You wrote, "How about specifying how to calculate how to make the cost/benefit analysis rather than just stating doing various items are or are not 'cost effective'?"

Good suggestion -- an excellent idea for a future blog. A full explanation would be beyond the scope of the current discussion, but your suggestion has merit.

Briefly, any good energy modeling program can be used to calculate the energy necessary to heat and cool a building. By performing two iterations -- one with the existing windows, and one with the proposed replacement windows -- it's fairly simple to determine the difference in energy use between the two cases.

For homeowners interested in getting a general idea of the effect of different window choices on energy use, I suggest a visit to the Efficient Windows Collaborate website. The site includes an online calculator displaying the heating and cooling costs of a "typical" American house with a variety of window options.

Once one knows the annual energy savings attributable to the proposed window replacement, it's necessary to determine two other factors: the existing energy costs and the presumed rate of energy cost inflation. The latter number can be contentious.

Finally, an economic analysis can be done many ways. It's possible to do a simple payback analysis, a cash flow analysis, or an analysis that considers the net present value of the investment. For more information on these different methods of analysis, see:

Nov 15, 2011 5:10 AM ET

Response to Dave Williams
by Martin Holladay

Your point about incandescents versus CFLs is well taken. Of course, many CFL proponents exaggerate the savings attributable to swapping bulbs, because they make the elementary error that you mention. Fortunately, Michael Blasnik is aware of the difference in heat output between the two types of bulbs and has taken that difference into account.

If we were to take an extreme case, consider a homeowner who heats with electric resistance heat and who doesn't have an air conditioner. Such a homeowner is a poor candidate for swapping bulbs. But this description represents a tiny minority of Americans.

If we consider a more typical example -- a homeowner who heats with natural gas and who uses an air conditioner during the summer -- then swapping bulbs makes economic sense, in any climate.

Nov 15, 2011 5:13 AM ET

Response to Chris Richter
by Martin Holladay

You wrote that you are puzzled about the following advice given to Austrians: "Open the windows 2-3 times daily in the winter for 15 minutes."

My guess is that the reason this is done is to provide adequate ventilation. Most existing homes in the U.S. are quite leaky; due to the stack effect, they experience a lot of infiltration during cold weather. But if a house is relatively tight, and if the house lacks a mechanical ventilation system, then the advice makes sense.

Nov 15, 2011 11:55 AM ET

With windows it's more about the comfort than the energy
by Dana Dorsett

It's easy to point to a lot of measures as having a less favorable net present value on the energy savings but with windows going from U0.5 (or more) to under U0.3 there is a noticeable increase in comfort at the outdoor temperature extremes, particularly during the heating season. With better windows convective drafts go down, and the radiant loss of human skin while standing in front of the window is cut in half. The whole point of a house and it's HVAC systems art to keep the inhabitants comfortable- you can't calculate an NPV on comfort .

Similarly, while having a 3x oversized single-stage hot air furnace isn't a big energy hit the high noise, higher air flow, short-cycling & overshoots etc are a significant cut in comfort. (And as I previously posted, oversizing non-modulating boilers by 2x or more IS an energy hit, particularly on systems with low mass heat emitters such fin-tube baseboard. At 8-10x oversizing even a condensing hot air furnace takes a big hit in operating efficiency, and they're out there!) In the hot air furnace case, right-sizing it is usually getting more comfort for a lower cost system, and by not short-cycling it the equipment lasts longer- it's a triple-win.

The notion that CFLs don't ultimately save a lot of money due to the heating factor is ridiculous in most markets. Only if you're heating with ~$3.50 oil in an 85% burner in an an area with ~10 cent electricity would it be a wash on heating energy costs. In a more typical buck-a-therm gas & 15-cent electricity land the heat you get out of the incandescent bulb costs more than 2x than making up that heat with an 80% gas furnace. (And if you're heating with oil or propane and off the gas grid, adding some supplemental heating via a ductless mini-split heat pump has a very favorable NPV.)

Nov 15, 2011 12:06 PM ET

Response to Dana Dorsett
by Martin Holladay

Once again, I'll repeat: I never said there weren't important reasons to consider window replacement. Improved comfort is one of them.

There is no argument here. If you want a granite countertop and new windows, there are plenty of reasons to install them. Just don't expect an energy payback from either investment.

Nov 15, 2011 2:27 PM ET

Trivial Savings?
by Mark Wilson

While some energy saving measures might offer only "trivial" savings in an individual home, multiply those savings by 114,000,000 (2010 census estimate of US households) and we're talking about real savings—savings that can please people with wide ranging interests: energy independence, climate change, economics (utilities save money by not building new generating plants).

For example; the 3% savings from caulking... Let's lowball a guess that on average a household spends $1000 a year on heating. 3% is $30 a year, times 114,000,000 households gives a national savings of 3.42 billion dollars. Perhaps some energy nerds can figure how much coal and gas that might save per year. Add in two more "trivial" savings of 1% each and we're getting close to $6 billion dollars per year.

Now let’s add businesses and schools and churches to the equation…

Nov 15, 2011 4:01 PM ET

The bigger picture
by Bill Nemick

I enjoy reading about ways to save money, energy, and how to be greener, and I agree with Mr. Blasnik when it comes to the cost efficiency of the retrofits and actions he discusses. The only issue I have with these types of articles is that they usually only focus on the cost reduction of the utility bill. While this is obviously very important, it does not take into consideration of the benefits of the energy savings for our Country and Planet as a whole.
What we need to understand is that the less energy we use today, the more that will be available tomorrow (I'm primarily referring to fossil fuels). By being more efficient with our energy use, we will not only have more energy to use later, but it will also decrease the amount of oil that we have to import from other Countries that use this revenue for unsavory things like funding terrorism. We all know that combating terrorism is extremely expensive, not only in dollars but human lives. While it is extremely difficult to determine how much we would save in dollars and lives by becoming more energy efficient, we should be aware that in all likelihood, it would be substantial. There are many other factors involved when calculating the true savings from energy efficiency that I haven't touched on, such as the reduced financial costs and negative health effects of producing less pollution, not to mention Global Warming.
I'm not an extremest nor am I advocating extreme energy efficiency measures, but rather I'm trying to enlighten people to the fact that there is much more to the equation in calculating true savings from becoming more energy efficient than to only determine how much money the individual will save on their utility bill alone. As Mr. Blasnik suggests, we should concentrate on the major energy hogs first and then we should work on improving our energy efficiency in areas that would pay off in the complicated "Big Picture" even if the savings isn't obvious in our utility bills.

Nov 15, 2011 4:11 PM ET

Response to Bill Nemick
by Martin Holladay

OK, if your goal is to reduce energy use -- you still want to do it efficiently, in a way that doesn't waste money. Why advocate spending $10,000 on new windows at one house (for example), a measure with not much of a return, instead of spending $2,000 each at 5 different houses to reduce air leakage?

We all want to reduce energy use. But we might as well be smart about it. The means concentrating on measures with a reasonable return on our investment.

Nov 16, 2011 11:06 AM ET

Edited Nov 16, 2011 11:23 AM ET.

cost efficiency
by j chesnut

I would like to expand on Philipp's comments on this topic.
Cost efficiency is easy to argue for some but difficult for others.
Having experts agree on its basis of being established will be impossible.
Let's recognize that the PH standard is predicated on a cost efficiency analysis for the German market (see attached graph) for homes in which a heating unit can be omitted.
I do worry about the Building America Program's strong insistence on cost efficient measures because I feel it allows somewhat conservative experts to buttress their opinions and not promote more innovative energy efficiency developments in the industry.
In principle the middle path is the best way forward.

Buying from a food co-op is not cost efficient if the measure is based on a food item per dollar basis. However I find buying from a co-op a very cost efficient manner of maintaining reasonable wage jobs in a good working environment for my neighbors and helping to sustain organic farming measures and all the associated businesses involved with the distribution and marketing. All in all a very positive sub economy.

I am finding driving a fuel efficient hybrid car is also very cost efficient within a car sharing program. I look forward to this sub-economy growing also in metro areas.

Screen shot 2011-11-16 at 9.00.07 AM.png

Nov 16, 2011 11:16 AM ET

Edited Nov 16, 2011 11:29 AM ET.

Response to J Chesnut
by Martin Holladay

I disagree with your characterization of the Passivhaus standard.

While German proponents of the standard claim that the 0.6 ach50 limit and the annual space heating limit of 15 kWh per square meter are based on a cost-effectiveness analysis, I have never seen any calculations backing up that claim. As PV arrays drop in price, my skepticism over the German claim only increases.

Certainly in the U.S., few (if any) Passivhaus buildings show the dramatic cost drop in HVAC equipment predicted by Dr. Feist. This is mainly due to the cost of the HRV, and the tendency of Passivhaus designers to specify very expensive HVAC equipment.

Nov 16, 2011 12:18 PM ET

Edited Nov 16, 2011 2:40 PM ET.

Response to Martin
by j chesnut

Sure, I don't know if PHI did actual analyses. The graph I show is from the CEPHEUS book "Living Comfort Without Heat" published in 2001. As Passivhaus was presented to me this graph shows that a "sweet spot" was discovered when you can optimize the thermal envelope and the solar heat gain to the point where you can omit the heating system and invest that money into the envelope. I'm sure you are aware of this. My point is that it is a cost efficient argument if not analysis.

On the same token other entities often claim to have performed cost analyses but have made little effort to make transparent how they performed them. The release of BEopt+ I hope leads to some productive exchanges of information. (I just wish there was a MAC version of the software.)

To be clear I am trying to emphasis that 'cost effectiveness' is in its essence an argument. 'Cost effectiveness' is not an objective reality that can exist independently of subjective formulations.

I appreciate that you offered an argument about how much to insulate based on the cost of PV though I think it allows too much room to justify not pursuing further thermal performance based on the cost of an offsetting PV system that wouldn't be even required to be included.

Nov 16, 2011 3:22 PM ET

Numbers hold the info
by Buildingwell .org

This is a great, and quite interesting, list of energy myths. Even surprising. While many out there may be somewhat shocked and unsure about some of them, Blasnik's point that the statements need to be backed up by numbers is an important one. Of course, there may be instances of differing results but in the end it's important for any energy specialist to take the building into context along with the potential energy saving methods. Great information.

Nov 16, 2011 6:26 PM ET

New windows do NOT increase your home's value...
by Pam Kueber

Data are Good. Remodeling Magazine's most recent Cost. vs. Value numbers just came out last week. I'm thinking I'm reading that you can expect to only recoup 65-70% of your cost for new windows on resale. That is, you will lose 30% of the money you just spent. So the argument that you "increase your home's value" is not valid either - IF you count the money you had to put in. Link:

Nov 16, 2011 6:34 PM ET

Low hanging fruit
by Pam Kueber

Martin writes:

"OK, if your goal is to reduce energy use -- you still want to do it efficiently, in a way that doesn't waste money. Why advocate spending $10,000 on new windows at one house (for example), a measure with not much of a return, instead of spending $2,000 each at 5 different houses to reduce air leakage?"

I agree this is absolutely positively the right way to look at the issue. If we are going to have government incentives, for example -- focus them exclusively on cleaning up/greening up all the low hanging fruit -- air sealing, insulation, HVAC, storms... And until all of America gets done, no subsidizing fancier fixes. Your pyramid, Martin...

Nov 16, 2011 6:36 PM ET

Window Quilts
by Pam Kueber

Last one. Drats. My pinch pleats aren't working? Calling Window Quilts tomorrow...

Nov 17, 2011 1:46 AM ET

sediment in water heaters
by Larry Weingarten

Hello: it is a myth that removing sediment from tank type water heaters saves significant energy. I think this came from a study on boiler scale, (not sediment) done at the National Bureau of Standards, eg; "According to the US National Bureau of standards, ¼” of scale build up on heating units requires up to 55% more energy to attain the same temperature." ... From a more recent (ended 1986) Gas Research Institute study on "The Effect of Water Quality on Residential Water Heater Life-Cycle Efficiency," it was concluded that even with 60 pounds of scale buildup recovery efficiency in gas heaters was reduced about five percentage points.

I'd love to see a study on boiler scale and tankless heater efficiency!

Yours, Larry

Nov 17, 2011 5:54 AM ET

Response to Pam Kueber
by Martin Holladay

Thanks for the link to the Remodeling magazine study that shows that you don't recoup your investment when you install new windows in a house you intend to flip. There goes one more reason to consider window replacement...

Nov 17, 2011 5:55 AM ET

Response to Larry Weingarten
by Martin Holladay

Thanks for contributing to the energy-myth list!

Dec 20, 2011 6:29 PM ET

Insulating outlets

Back in the 1960's I lived in a mobile home at the top of a hill. In winter time when you walked by an outlet that was on a an outer wall you could feel the cold air coming through it especially on windy days. They tell me that modern day mobile homes are built better but I would not know because I have not lived in one for thirty eight years. Anyway.... I'm wondering if what is now myth had it's basis in fact years ago? In retrospect I don't think that insulating the outlets on my old mobile home would have done all that much good considering how thin the walls were and all the other leaks it must have had.

Dec 20, 2011 7:42 PM ET

Response to Carl Belken
by Martin Holladay

The information in this blog refers to houses rather than mobile homes, and air leakage patterns probably differ in the two types of housing.

It's certainly true that air leaks through electrical receptacles are the ones you can feel. Few people spend much time in their attic to feel the (usually much more significant) air leaks up there.

Feb 10, 2012 4:53 PM ET

Energy Myths
by Jonathan Beers

My current collection is attached, several of which I borrowed from Michael Blasnik and others.

I have questions about the myth "Closing hot-air registers in unused rooms saves energy". The study cited was from California, and if memory serves, the homes studied had ductwork outside the heating envelope (so closing registers increased leakage of conditioned air to outdoors).

What about homes with ductwork within the envelope? Would the furnace run less with a register closed (and the door to the room closed)? A related question would be: Would the furnace run less with register closed because the thermostat was getting satisfied faster due to more heat being delivered to the room where the thermostat is located? And yes, I'm aware of potential problems from closing off registers if temperature rise across the heat exchanger (or drop across the AC coil) is close to being outside of manufacturer's specs. (Air flow outside of specs.)

Energy Myths.docx 19.31 KB

Feb 10, 2012 5:30 PM ET

Response to Jonathan Beers
by Martin Holladay

That's a great collection of energy myths. Thanks for sharing your list.

Jan 18, 2013 12:29 PM ET

pocketbook and time efficiency
by Erich Riesenberg

I am starting my house upgrading and appreciate the science based approach.

Found this blog post by trying to figure out how to caulk a window. Will now focus on air sealing the basement and then the attic.

Interesting that a post on how some projects do not provide a good economic return morphs into all sorts of non responsive disagreements.

I think the comment about windows is particularly important, a big expense. The prior owners of my house spent a lot upgrading half the windows to the "best" available when they probably would have done better by doing all the windows to a lower quality or none at all. The old windows are from the 1950s but double paned.

Jul 3, 2013 4:58 PM ET

Edited Jul 3, 2013 5:02 PM ET.

"furnace" filter replacement
by Robert Rinehuls

Four and five inch media filters are pricey and there is a device by General Aire ( ) to help you determine when it's time to replace the filter. It's mounted between the filter and the blower. You zero in the gauge at the time you install a new filter and then the indicator gradually swings towards the "replace" zone as the filter loads and vacuum increases. Although this might be helpful, it seems to me if you used an actual vacuum gauge, say the 0-30 IN-Hg you have laying around from your shade tree mechanic days, you could make a more accurate evaluation. But what Hg reading should you be looking for?


Jan 5, 2014 5:18 AM ET

Cooking pots
by Rose Rodent

You mention that covering cooking pots results in "zero or trivial" energy savings. Is it zero or is it trivial? If it's trivial, of course it would not belong in a list of ways for people to save actual money on their individual fuel bills, but if every worldwide user of non-renewable energy covered their cooking pots, assuming for this purpose that they own lids for each pot and do not have to make vehicle journeys and manufacturing energy to come by lids, will there be a saving of energy over 12 months that is measurably useful?

All the furnace stuff is double Dutch to me as a European, and I'm interested to know whether turning off water-based radiator heating run from a gas-fired central heating boiler will save energy. I always turn off the radiators upstairs when I'm downstairs all day and vice versa, and perhaps I can stop bothering myself! Since most myth debunkers seem to be US based, it's very hard to get information which isn't based on running HVAC systems.

Jan 5, 2014 7:07 AM ET

Response to Rose Rodent
by Martin Holladay

Go ahead and cook with lids on your pots, unless you are doing a sauce reduction or making maple syrup. Just don't expect that the practice will show up on your energy bill, one way or another.

If you live in a house with hydronic heat distribution (with radiators or hot water pipes to distribute space heat), then shutting off a radiator in an unused room will save energy.

Jan 5, 2014 1:30 PM ET

Cooking #2 + human behaviour
by Rose Rodent

Thanks for the response, though I still remain curious as to the actual level of the "insignificant" difference. If, for example, we assume that the entire continential US is currently cooking one meal a day with uncovered pots and that their pots are on for 20 minutes on a gas burning stove, assuming they switch to covering pots, will the difference over 12 months be closer to 5c or $5 or much more? I know it will make no noticeable difference to an individual, but I'm curious whether it makes sense as a global energy saving measure or whether it's just busy-work.

My follow-up thought is about the difference between lab measures and actual human behaviour. A lab test of a room which measures heat loss with all kinds of equipment will likely find little heat loss through a small draught or window gap. The trouble is, people are not monitoring equipment. The person who has set up his/her sofa so that it's directly in that draught will likely respond to this chill wind blowing on their person by cranking up the thermostat a couple of degrees. So although the heat loss is negligible in testing, the *effect* is a 2 degree C increase in thermostat temperature, which is far from negigible - the person is trying to compensate for his terribly cold legs/back/neck by warming the rest of him to a greater degree. He doesn't care about P values (?) or BTUs or Therms, he cares that the draught is hitting him directly and it feels cold. I have a kitchen extractor fan with a no-return valve thing in it, but it was clearly not designed for the gale force winds which rage here all winter. We refer to the kitchen as the "igloo door" as the immediate effect of opening this door is a chill wind hitting everyone in the torso. It doesn't rate much on paper as a source of heat loss, as it takes hours to lose any actual noticeable amount of temperature from the room overall, but it is likely to have a disproportionate effect on our use of home heating compared to its effect on heat loss beause the cold blows directly at us - is human behaviour compensated for in testing?

Jan 6, 2014 11:36 AM ET

Response to Rose Rodent
by Martin Holladay

The short answer to your questions is that researchers have, over the last 4 decades, investigated the best energy retrofit measures from many perspectives, including human behavior. Michael Blasnik's data and recommendations are based on real-world weatherization programs, which compare pre-retrofit with post-retrofit energy use data. This type of data necessarily takes occupant behavior into account.

In other words, the data come from the field, not from the lab.

When prioritizing recommendations for energy retrofit work, it makes sense to list recommendations that will save homeowners money on their energy bills. You are correct that it's possible to make a different list -- a list of measures which save energy, but the amount of energy saved is so small that you will never see a difference on your energy bill. That time of energy-saving measure may make sense to environmentalists, so I am not ridiculing it. But it doesn't belong on a list to help homeowners save money.

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