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Stupid Energy-Saving Tips

Martin’s roundup of ill-conceived internet tips

Posted on Dec 27 2013 by Martin Holladay

Just for fun, I recently Googled the phrase “energy-saving tips.” I dove deep — all the way to page 7 of the Google results. My research was profoundly discouraging.

Back in 2011, I wrote two articles about bad energy-savings tips. (See More Energy Myths and A Plague of Bad Energy-Saving Tips.)

Since then, is there any possibility that the quality of online advice improved? Not a chance.

Evidently, there is a secret stupid tips network (or stupid tips underground) that shares bad advice. Every now and then, some utility executive or government employee comes up with a new stupid tip, and (worried that the idea might not get the recognition it deserves) immediately sends out a mass e-mail to every member of the stupid tips network, so that the tip can be published widely.

Virtually every list of energy-saving tips on the Web includes some bad advice. The bad advice is so pervasive that I have decided to catalog these tips by category — to create a taxonomy of stupid tips.

The Top Ten List of stupid energy tips

Here’s my top ten list — common tips that show up repeatedly.

1. Fill your half-empty refrigerator or freezer with plastic bottles filled with water. This stupid tip will never save you enough energy to show up on your electric bill. Nevertheless, the advice is provided by the California Energy Commission, an electric utility called NV Energy, Avista Utilities, Wisconsin Public Service, Georgia Natural Gas, an electric utility called National Grid, Connecticut Light & Power, EnergyRight Solutions, and many others.

2. Clean the dust off your refrigerator’s heat-exchange coils. As I’ve noted before, researchers haven’t been able to measure any energy savings resulting from this measure. But a lack of data hasn’t stopped the following sources from advising homeowners to get out the vacuum cleaner: NV Energy, Connecticut Light & Power, and EnergyRight Solutions.

3. Schedule an annual furnace tune-up. As Michael Blasnik has shown, there is no evidence to support the idea that the cost of an annual furnace tune-up can ever be recouped by energy savings. This tip (often referred to as the “make-work-for-HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building.-techs” tip) is trumpeted by an electric utility called WE Energies, Wisconsin Public Service, a New Mexico electric utility called PNM, EnergyRight Solutions, and a utility named Alliant Energy.

4. Change your furnace filters monthly. Monthly? Really? Yes — according to Wisconsin Public Service and EnergyRight Solutions.

5. To reduce the rate of air leakage in your home, start by caulking around windows. Actually, the big leaks are in your attic and basement, not around your windows. That doesn’t stop many sources from offering the “caulk your windows” advice. Among the guilty are the California Energy Commission, NV Energy, WE Energies, the California Natural Resources Agency, Virginia Energy Sense, and a utility called NSTAR Electric & Gas. (The tip from NSTAR even includes a definition of the word “weatherize.” The site advises, “Weatherize your home by caulking and weather-stripping all doors and windows.”)

6. Install foam gaskets under your electrical outlet covers. There are only two problems with the advice: electrical outlets aren’t a major air leakage point, and gaskets don’t stop air leaks at this location. These two small problems don’t prevent the following sources from providing the tip: the California Energy Commission, a gas utility called PSNC Energy, Alliant Energy, and CNN.

7. Run your ceiling fans backwards during the winter. No researcher has ever been able to show that this practice saves energy. This tip may even make you uncomfortable enough to turn up the thermostat, raising your energy bills. But the advice is provided by Duke Energy, Alabama Power, an electric utility called Xcel Energy, and a Sustainability blog on the University of Illinois at Chicago web site.

8. Run your air conditioner and ceiling fans simultaneously. According to a 1996 paper (“Are Energy Savings Due to Ceiling Fans Just Hot Air?”) by P. James, Jeffrey Sonne, R. Vieira, Danny Parker, and M. Anello, “Data from 386 surveyed Central Florida households suggests that although fans are used an average of 13.4 hours per day, no statistically valid difference can be observed in thermostat settings between households using fans and those without them.” In other words, homeowners who run their ceiling fans and air conditioners simultaneously would be better off if they turned off their ceiling fans. This bad advice is provided by WE Energies and a utility called PSE&G.

9. Locate your air conditioner condenser in the shade to keep it cool. This myth was debunked many years ago by researchers at the Florida Solar Energy Center. Yet it still keeps cropping up, most recently in advice provided by PSNC Energy.

10. During the winter, close your curtains at night to save energy. When this advice is repeated, the authors usually fail to mention that you need a way to stop air from flowing between the curtain and the window — or else convection currents will sabotage your efforts to save energy. This incomplete tip is provided by many sources, including Connecticut Light & Power and the website of the National Association of Certified Home Inspectors.


After you've read the bad advice, you may be ready for some good advice. Here it is.

1. Seal air leaks in your attic and your basement. To learn more, see Air Sealing an Attic and Air-Sealing a Basement.

2. Add insulation to your attic if the insulation is thin.

3. Insulate your walls if they are uninsulated. (If you have a wood-framed house, you probably want to insulate your walls with dense-packed cellulose.)

4. Seal the seams of any ducts located outside the thermal envelope of your home, and add duct insulation if the ducts are poorly insulated.

5. Swap your incandescent bulbs for CFLs or LEDs.

6. If your refrigerator, furnace, or air conditioner is old, swap it for a new, high-efficiency appliance. Make sure your furnace blower isn’t on all the time. (It should be set to “auto,” not “on.”)

7. If your house has single-pane windows and you live in a cold climate, install low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. exterior storm windows.

8. If you live in a cold climate and you heat with fuel oil, consider installing a ductless minisplit heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump. in your living room.

9. If you live somewhere with high electricity rates and decent PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. incentives, install a PV system.

10. Set back the thermostat when you’re not home or when you are asleep.

11. Unplug second refrigerators and freezers.

Tips which may save energy but which cost way too much to implement

A tip fails the cost-effectiveness test if implementing the tip costs more than will ever be saved by lower energy bills. Here are four tips in that category:

Install a backyard wind turbine. This energy-saving tip came from My San Antonio magazine.

Install a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures.. This energy-saving tip came from U.S. News & World Report.

Install a solar water heating system. This energy-saving tip came from Duke Energy.

Install replacement windows. This energy-saving tip came from NV Energy.

Distractions intended to keep you busy rather than save energy

After the Allies defeated Germany and Japan in 1945, the U.S. government admitted that many of the war-time campaigns urging Americans to gather rags and steel cans for recycling were launched to give citizens a psychological boost rather than because of shortages of rags or steel. Many energy-saving tips have this same flavor: they are intended to keep homeowners busy — too busy to read the meter or pay attention to their actual energy bills.

The tips in this category usually focus on cooking. The basic problem with tips that save cooking energy is that cooking represents only 4% of U.S. residential energy use. So even if you can find a way to save 10% of the energy used for cooking, you will only save less than 1/2 of 1% of your residential energy use.

Clean the reflectors underneath your stovetop burners. Scrub all you want, but this effort won’t show up in your gas or electric usage. Still, this advice is provided by NV Energy and Duke Energy.

Always make sure that you have a lid on your pot when you’re cooking. This tip comes from an electric utility called Reliant, the city of Tallahassee, Florida, the city of Richland, Washington, and Alliant Energy.

Cook with copper-bottomed pans. This tip causes me to shake my head in wonder. It comes from Duke Energy.

Contradictory advice

If you read enough lists of energy-saving tips, pretty soon you will realize that some tips directly contradict other tips.

Close off heating registers in unused rooms — no, wait: leave them open. According to the city of Tallahassee, “Closing off rooms or registers will not save money and may lead to problems.” But Terry Webster from the Minnesota Office of Energy Security offers this energy-saving tip: “Close registers in unused rooms.”

Use a space heater — no, wait: never use space heaters. According to “Energy-Saving Tips” from TXU Energy, “Use Space Heaters. … There are days when you spend most of your time in one or two rooms. That’s when you should consider lowering your thermostat and using a space heater.” But another list — “101 Ways to Save Energy,” a document on an Alliant Energy web page — advises, “Avoid using space heaters, including electric, kerosene or propane models. Not only are they expensive to operate, they’re also very dangerous.”

Wild exaggerations

How good are utility executives at quantifying the energy savings that homeowners can expect by implementing their recommendations? They are really, really bad.

Window replacement. According to NV Energy, replacing “inefficient single-pane windows with energy efficient multi-pane, thermally-broken, vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate).-framed windows,” will “save you another 25% on your monthly bill.” According to Michael Blasnik, the saving in heating energy use that accrues from window replacement in cold climates is on the order of 1% to 4%. In a cooling-dominated climate like Nevada, electricity savings will vary greatly depending on many factors, including how shaded the windows are; but it is highly unlikely that electricity savings will approach 25%.

Choose the right sized pot when you are cooking. According to Wisconsin Public Service, “Just by using the right size pot on a burner, you can save about $36 a year if you have an electric range, or $18 a year with a gas stove.” Or perhaps 48 cents.

Caulk and weatherstripping your doors and windows. According to Virginia Energy Sense, this simple measure “can cut your energy bill by as much as 30%!” Or maybe 1%.

Annual furnace tune-ups. According to Alliant Energy, “A $50-100 annual tune-up can help reduce your heating costs by up to five percent.” Or maybe 0%.

Locating your air conditioner in the shade. According to PSNC Energy, this simple measure can increase the efficiency of your air conditioner by 10%. Or not.

Dangerous or counterproductive advice

This is a fun category: it consists of advice that can make things worse.

Open the vents on your crawl space during the summer. If you follow this advice, you will allow humid outdoor air to enter your crawl space. The humidity is likely to condense on cold surfaces, which can lead to mold or rot. It’s hard to imagine why this suggestion is on anyone’s list of “energy-saving tips,” but it is. It appears on lists posted by an electric utility called Dominion and Alabama Power.

Use a humidifier. This strange energy-saving tip can get you into trouble very fast, since the use of humidifiers is associated with sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. rot. Humidifiers are promoted as a good way to save energy by Georgia Natural Gas and Black Hills Power.

Add more attic ventilation. Unfortunately, homes that perform well without attic ventilation sometimes develop problems when vents are added. But some electric utilities are under the mistaken impression that adding attic ventilation can lower cooling bills, even though no researcher has ever been able to measure such savings. In spite of the lack of data, this measure is recommended by Reliant, PSNC Energy, and Long Island Power Authority.

Include an interior vapor barrier. In most climate zones, this is bad advice. Even in a very cold climate, this measure won't save you any energy. Nevertheless, you can find this tip on lists published by the state of Nebraska and Black Hills Power.

Install a fireplace. This may be one of the worst energy-saving tips ever devised. It comes from an article called “Remodeling Tips to Save Energy At Home” published by Living Green Magazine.

Tips that don’t belong

Sometimes, a list of energy-saving tips includes a few oddball items that were thrown onto the list by a desperate writer battling a press deadline. When you read the list, you wonder, “Now how is this supposed to save energy?”

“Recycle minor things; e.g., reuse empty soda bottles.” That energy-saving tip comes to you from a list on a site called

“Install countertops made of bamboo.” That tip comes to you from an energy-saving tips list published by My San Antonio magazine.

“Placing a mat at the front and back doors of your home can cut the amount of pesticide residue tracked inside.” That’s one of the “Top Ten Energy-Saving Tips” provided by

Suggestions that are never going to happen

The next tip reminds me of the advice given in the 1950s by parish priests about marital relations: Marital relations happen sometimes, but the act probably shouldn’t involve any pleasure. According to United Power, a Colorado electric utility, it’s possible to save energy if you “set your hot tub heater thermostat to 102º F.” I’m sorry, United Power, but that’s not going to happen.

Another tip in this category is true but totally nuts. According to Duke Energy’s list of “100 Ways to Save Energy at Home,” you should “keep your thermostat close to the outside temperature.”

Yup. That will work.

Bizarre tips

If you read enough of these energy-saving tips lists, you end up with a few that can only be called bizarre.

Here, in its entirety, is an energy-saving tip from PSNC Energy: “Keep your appliances free of dirt and grease (which can reduce operating efficiency).”

So, after spending half a day wiping down my washer and dryer, how much energy will I save?

One useful website has advice for homeowners who want to do a thermal survey of their home, but who can’t afford an infrared thermometerA digital thermometer capable of measuring the temperature of a surface from a distance ranging from a few inches to a few feet. Most hand-held infrared thermometers include a laser to help aim the device; the laser plays no role in temperature measurement. Used as an inexpensive substitute for a thermal imaging camera, an infrared thermometer can detect hot or cold spots on walls, ceilings, and duct systems. or infrared camera. What’s the tip? Use your dogs and kids as sensors!

Here’s the advice from Avista Utilities: “Children and animals love comfort, and they can help us find possible heat loss in and around our homes. If there are areas around single pane windows, doors or vents that your kids avoid, consider checking for heat loss. Conversely, if you find the family dog or other living creatures living on the periphery of your home, it might indicate significant heat-loss coming from your floor into your crawlspace, which can translate to lost energy dollars.”

Finally, here is a tip from an article called “Easy Ways to Save Energy This Winter,” published by The Telegraph. It’s a real head-scratcher: “Curing fish with alcohol: When it’s really cold outside, sometimes cold alcohol-cured fish, accompanied by a strong drink like schnapps, can be a wonderful livener, as the Scandinavians know. Rub two whole fillets of salmon with a mixture of two tablespoons of sea salt, one tablespoon of soft brown sugar, a bunch of chopped fresh dill and a generous glass of vodka or schnapps. Sandwich together and put in the fridge, weighted down by a wooden chopping board and several kitchen weights or other heavy items. You can eat it after three days, and it will be good in a fridge for a week.”

Evidently the energy savings come from the fact that you don’t need to use the stove. Another side benefit: after you’ve had some schnapps, you can turn down the thermostat.

Martin Holladay’s previous blog: “Casey Makes a Bet.”

Click here to follow Martin Holladay on Twitter.

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Dec 27, 2013 12:29 PM ET

#1 Filling Frig with water bottles
by But Why?

may not save energy but it will certainly extend the life of your persihable items in the event of a power loss such as has been going on across this country in the wake of last Friday/Saturdays ice storm. Adiitionally, homemade ice is cheaper for summer needs and more ecological than ice made in a central plant, trucked to a store and bought by someone who drove to a store to buy it.

Dec 27, 2013 12:40 PM ET

#3 Schedule an annual furnace tune up
by But Why?

may not save you energy but it may save your life.....if that matters at all to anyone. and it also exposes problems that are, by Murphy's Law, bound to happen when least convenient.

Dec 27, 2013 12:58 PM ET

Response to B.W.
by Martin Holladay

You wrote, "Filling your fridge with water bottles may not save energy..." and "scheduling a annual furnace tuneup may not save you energy..."

So we agree. The first tip doesn't belong on a list of energy-saving tips; it belongs on a list of things you can do to prepare for a power outage.

And the second tip belongs on a list of things you can do to minimize the chance of carbon-monoxide poisoning.

Dec 27, 2013 2:24 PM ET

Follow up
by Sandra Heiser

Good post! Will there be a 'profoundly ENcouraging' post of Brilliant Energy Saving Tips? Please? :)

Dec 27, 2013 2:39 PM ET

Edited Dec 27, 2013 2:41 PM ET.

Response to Sandra Heiser
by Martin Holladay

My list of "Real Energy-Saving Tips" is included on this page. It is a sidebar on the left-hand side of the article. My list includes 11 tips.

The GBA website has lots more information on the 11 topics I mention in my tips list. If you use the "search" box on our site, you'll find enough information to keep you reading for hours.

Dec 27, 2013 2:46 PM ET

Money saving tips
by Kevin Dickson, MSME

From my experience in owning lots of rental units, I need to comment.
I can't quibble with your lists, but here's my related list of money saving tips:

1. Change the furnace filter at least yearly. A neglected furnace filter increases the odds that lint and pet hair will accumulate on the furnace motor. That will cause the motor to overheat, causing short cycling (which reduces furnace efficiency) and eventual motor failure. Motor replacement is $200-$600.

2. The summertime use of ceiling fans in some climates may eliminate the need to spend money on installing or using air conditioning.

3. Really dirty refrigerator coils can cause premature failure of the refrigerator, or inadequate cooling of the food inside. Lint can also cover the compressor, insulating it, causing it to short cycle.

4. Storm windows may be more cost effective than new windows energy-wise, but keep in mind that they won't make a crappy old window operate better, or add any resale value to the house. New windows do both, and therefore can be a better investment in some situations.

Dec 27, 2013 2:51 PM ET

Martin; Thank you, missed
by Sandra Heiser

Thank you, missed seeing that the first go-round. This might not be the place to say it, but I'd like to voice my appreciation for this site and the obvious dedication and effort you put into it. We reference it often in our practice. THANK YOU!

Dec 27, 2013 6:47 PM ET

by But Why?

Changing furnace filters more than yearly is advisable. I have seen them clogged to the point that the whole filter gets sucked into the blower locking it up which, without a belt to slip/burn/break in todays direct drive blowers, means a burnt up motor in short order. While you can debate the savings of energy versus the cost of the filters, there shouldn't be any debate that a dirty filter does use more energy and does pose a risk to the air handling system in a number of ways.

Dec 27, 2013 7:02 PM ET

Another response to B.W.
by Martin Holladay

It should go without saying, but it seems that every time I write an article debunking energy-saving myths, I have to repeat the following statement: it's perfectly OK to engage in many of the activities listed on this page.

It's OK to clean your refrigerator coils. It's OK to change your furnace filter frequently. It's OK to clean the reflectors under your stove burners. It's OK to cook with lids on your pots.

Just don't expect any of these actions to save a significant amount of energy.

Dec 27, 2013 7:59 PM ET

Ultimate energy saving tip that will get me flamed!
by Robert Connor

One tip that will never happen in this country is: Do not have children. When a couple has one child they increase their carbon score by a factor of 6. Since most of the guys here have kids, I don't think anyone would say this idea.

Dec 28, 2013 10:11 AM ET

Furnace filters and ECM blowers
by Aaron Birkland

From Stuff [Michael Chandler] Learned at Joe Lstiburek's House, Part 2:

The difference of the pressure curves of clean versus dirty filters is pretty shocking as well. In one example, an ECM system with a clean filter running at 0.2 inH20 at 1,100 CFM drawing 225 watts ran with a dirty filter at 0.5 inH20 at 1,100 cfm drawing 320 watts. If it had been a PSC motor on that air handler, the flow would have been reduced on the order of 40-50%."

So while it may be unlikely that the filter will get that dirty in a month, and it's certainly unlikely that a yearly service tech visit is the most cost effective way to replace a filter, changing the filters on equipment with an ECM blower when they get noticeably dirty looks like it could save some energy

Dec 28, 2013 10:29 AM ET

Response to Aaron Birkland
by Martin Holladay

It makes sense to change furnace filters when they get dirty. Homes that are dusty will need more frequent filter changes than homes that are less dusty. Most homes will do just fine if the filter is changed once or twice a year -- but if you want to do it more often, that's fine too.

Changing filters once a month won't save you any energy, and tips like this are a distraction from the important measures that can really reduce your annual energy bill.

Dec 28, 2013 1:05 PM ET

Humorous typo
by Dick Russell

Martin, under "Suggestions that are never going to happen" you wrote:

"The next tip reminds me of the advice given in the 1950s by parish priests about martial relations:"

What's "martial relations?" Intimate karate? (I couldn't help that one)

Dec 28, 2013 3:56 PM ET

#9: A/C condensor
by Brent Eubanks

You said that this one has been debunked, but I'd like to get more detail on that. We know that a refrigeration cycle performs more efficiently when rejecting heat to a lower temperature (all other things being equal), so it's hard for me to see how this tip could be wrong, thermodynamically speaking.

I can see how this might be in the category of "real, but too small to matter". But even there, I'm skeptical. the temperature difference between a metal box in the sun vs in the shade (in a place where it matters, like Florida or Phoenix) can be 50+ degrees (which means you may nearly double your overall system delta-T). How can that NOT impact heat rejection efficiency?

Dec 28, 2013 4:33 PM ET

Response to Brent Eubanks
by Martin Holladay

The temperature of the metal box is irrelevant. The relevant material (fluid) for heat transfer is outdoor air. Outdoor air is at the same temperature on the sunny side of your house as it is on the shady side of your house.

Once the outside fan comes on, a tremendous volume of outdoor air flows across the outdoor heat exchange coils.

While it's true that a thin film of air near siding that has been warmed by the sun, or a thin film of air near a metal box that has been warmed by the sun, is at a somewhat higher temperature than the outdoor air, the volume of air in that film is insignificant compared to the large volumes of air pulled through the condenser.

Dec 29, 2013 10:20 AM ET

Edited Dec 29, 2013 10:51 AM ET.

The outside air is not the same
by Nick T - 6A (MN)

Outside air is the same everywhere? what?

The south side of my last house landscaped with dark grey rock and tucked behind garage... was not the same air temperature as the north side of my house.

And a 2ton condenser fan doesn't have enough umf to clear all that air and radiant heat off the rocks/house. If you put a temperature probe in the shade of the condenser it will be significantly warmer then the north side of the house.

Yes if a house has a dirty filter it will increase the speed of the fan and also could reduce the efficiency of the cooling system due to lower airflows (if not variable fan speed) - however in both cases it would have to be a freakishly dirty filter! For 2-4$.... get a new filter regularly.

The argument that stuff is hardly measurable so therefore a myth... Why isn't the passivehaus myth over PGH listed? lol

But yes! It is funny how so many utilities and energy savings groups push these old out dated ideas. Yes i suppose if everyone cleaned their air intake of their fridge (older fridges maybe more important? with serious heat to reject) it would make an impact on the utility side of things (10000 customers....times a few watts....) lol.

Dec 29, 2013 11:09 AM ET

Think I'm going to go suggest
by Aaron Vander Meulen

Think I'm going to go suggest to the wife we set the thermostat to the outdoor temperature...Its 36* so its not THAT cold...

Dec 29, 2013 3:49 PM ET

Extremely Unhelpful
by John Richards

I signed up just to make this one post.

I found this blog entry supremely frustrating. The reason is because it is just a rant. You provide links to the so-called bad tips - but no regular home-owner cares where the bad tips came from. We care WHY they are bad tips, but your explanations are profoundly lacking. At best you make off-hand comments and mention uncited studies but most of the time you just write as if the problems with the tips are self-evident. They are not! If we had the expertise to understand what is wrong with the tips then we would not need to read the blog post in the first place because we would already know that the tips are poor ones.

I will give examples:

Caulking around windows "The big leaks are in your attic and basement" - OK, but that doesn't address how useful it is to do the windows if the big leaks are taken care of.

AC Condenser in the shade: "debunked many years ago by researches at the FSEC" - where is the report?

Close off heating registers: So the advice is contradictory - how about an explanation from an HVAC expert about what is the right advice?

Water in the fridge / freezer: No explanation as to why they make the tip nor why it is wrong - if you have the space for a big block of ice in your freezer what is the downside?

Install a fireplace: What is wrong with that? Is it because of air leakage? Is it because burning wood is not a cost-effective way to heat a room? What about a fireplace with a lot of thermal mass like a stone hearth?

If your goal is to rant, mission accomplished. If your goal is to educate, you need to start over from the beginning and provide much better explanations of just why each tip is unhelpful or at least link to a comprehensive explanation. Otherwise you aren't helping anyone to better understand the issues.

Dec 29, 2013 3:52 PM ET

Response to Nick T
by Martin Holladay

Q. "Outside air is the same [temperature] everywhere? what?"

A. I stand by my answer. It is. This can easily be verified by the use of a thermometer. (Of course, the bulb of a traditional glass thermometer should not be in the sun, or the sunlight will cause the fluid in the thermometer to give a false reading of the air temperature; the thermometer must be shaded.)

The reason that you feel warmer on the south side of your house is because of radiation from the sun striking your skin and clothing -- not because the air temperature is different.

The volume of the thin film of air adjacent to sun-warmed surfaces is quite tiny. It represents a tiny percentage of the air that is forced by the fan through the condenser coils.

Dec 29, 2013 4:25 PM ET

Edited Dec 29, 2013 5:32 PM ET.

Response to John Richards
by Martin Holladay

Your criticisms are fair, and I'll do my best to answer your questions.

Q. "Caulking around windows ... The big leaks are in your attic and basement. OK, but that doesn't address how useful it is to do the windows if the big leaks are taken care of."

A. There are many articles on this website that discuss blower-door-directed air sealing. Here are a few of them:

Questions and Answers About Air Barriers

Blower Door Basics

Getting the Biggest Bang for Your Air-Sealing Buck

Navigating Energy Star’s Thermal Bypass Checklist

Air Sealing an Attic

A Home-Energy Audit

By now, weatherization contractors who are trying to reduce the air infiltration number shown on a blower door have learned where to look for leaks, and which leaks to address first. In most homes, the leaks that matter are in the attic and basement. Windows tend to be located near the home's neutral pressure plane, and are therefore much less affected by the stack effect.

To reduce air leaks near a window, you might need to perform some of the following work: (a) Add weatherstripping or replace the existing weatherstripping; (b) carefully remove the casing and seal the gap between the window rough opening and the window frame with low-expanding canned spray foam, and then replace the casing. Although this work is unlikely to make a significant difference if you are trying to reduce the rate of air leakage in your home, it's perfectly sensible to do it, and it can often improve occupant comfort. But remember: the first places to begin your air sealing efforts are your attic, basement, and crawl space.

Q. "AC Condenser in the shade was debunked many years ago by researchers at the FSEC. Where is the report?"

A. One of the best articles on this topic, "The Nonbenefit of Shading Air Conditioners," was published in the July 1995 issue of Energy Design Update. While it is not available on the web, you may be able to find it in a good academic library.

You might also look at "Air Conditioner Shading Shows Minimal Savings," in the Sept/Oct 1995 issue of Home Energy.

Q. "Close off heating registers: So the advice is contradictory - how about an explanation from an HVAC expert about what is the right advice?"

A. Don't close off your heat or air conditioner registers in unused rooms. Studies show that this practice increases leaks through leaky ductwork, wasting energy.

In a previous article (More Energy Myths), I provided more information on this topic. In that article, I wrote, "[Michael] 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.' ”

Q. "Water in the fridge / freezer: No explanation as to why they make the tip nor why it is wrong - if you have the space for a big block of ice in your freezer what is the downside?"

A. I'm not sure why this tip is offered -- the logic behind bad advice is often lost in the mists of time. I would guess that someone was trying to reduce the volume of air that spills out of a refrigerator every time the door is opened. The energy savings resulting from making this volume of air smaller would be insignificant. There is no downside to keeping a big block of ice in your freezer, so go right ahead and do that if you want to.

Q. "Install a fireplace: What is wrong with that? Is it because of air leakage? Is it because burning wood is not a cost-effective way to heat a room? What about a fireplace with a lot of thermal mass like a stone hearth?"

A. You guessed correctly: fireplaces are responsible for huge levels of air leakage, even when they aren't operating. When they are operating, they often remove more heated air from your house than they provide, resulting in a net loss of heat. If you want to use firewood as a fuel to heat your house, install a wood stove. For more information on this topic, see All About Wood Stoves.

GBA has many articles that are written for homeowners who are just beginning to examine energy-related issues; you might be interested in browsing through our encyclopedia (available by clicking on the "Green Basics" tab at the top of every page). We also have a few articles (like this one) geared toward energy geeks. In any case, whether your are a beginner or an energy geek, we welcome your feedback, and we also welcome questions on our Q&A page.

Finally, if you use the "search" box on the GBA website, you can find thousands of articles on many topics.

Dec 29, 2013 9:10 PM ET

Edited Dec 29, 2013 9:10 PM ET.

Save energy by being a hippie
by Jonathan Teller-Elsberg

In particular, I'm thinking of the classic energy saving habit of showering infrequently. It worked wonders for me in my feckless youth until a coworker asked me to shower more often. I decided I liked my coworker more than I liked saving a smidge of energy. But for the misanthropes in the audience, reducing consumption of hot water has got to be a genuine energy saver. (Right?) I compromise by taking short showers and using a low-flow shower head.

Dec 29, 2013 9:45 PM ET

by Lastman Ever

I think your views on curtains, also noted in previous articles, need a little more evidentual backing. While the theory seems sound, I have always found that closing curtains, whether well sealed at the top or not has a significant effect on both comfort and the measureable temperature of the room for a constant heat source. These effects would be less significant with insulated glazing, of course.

Dec 30, 2013 6:35 AM ET

Edited Dec 30, 2013 10:58 AM ET.

Response to Lastman Ever
by Martin Holladay

Like many of the tips discussed on this page, there is nothing wrong with pulling your curtains shut on a cold winter night. This measure will usually improve occupant comfort, by reducing the chilling effect (radiational cooling) that occurs when heat radiates from a person's skin or clothing to a cold window pane.

Pulling curtains shut on cold winter nights isn't stupid. But I called it an "incomplete tip" for three reasons:

1. There isn't any evidence that this measure will lead to significant energy savings.

2. The discussion failed to address the characteristics of an effective window quilt, thereby wasting an opportunity to explain what a good window quilt would look like. (A window quilt differs from curtains in several ways. A window quilt has an airtight assembly at the top that seals the gap between the window quilt and the wall; it also has relatively airtight tracks at the sides; and it seals against the window stool with weatherstripping and Velcro. Without these features, curtains set up convective currents that can actually raise your energy bill slightly.)

3. The discussion failed to address the fact that effective window quilts aren't a cost-effective energy savings measure, because any savings attributable to the use of a window quilt aren't enough to justify the high cost of a window quilt.

By the way, I have a window quilt in my bathroom, and use it regularly during the winter. It is effective, and I'm glad I have it. But I am under no illusions that it will save enough energy to justify its high cost.

Dec 30, 2013 10:25 AM ET

Edited Dec 30, 2013 10:28 AM ET.

Diffuser followup
by Nick T - 6A (MN)


Regarding the studies (in Cal) were these results scewed by the HVAC being located in the attic and or primarily cooling data?

Curious because duct losses (leak or temp) inside a conditioned space (floor, wall, basement) aren't completely lost or wasted. They are essentially the same as heating/cooling an unused room.... but really in the case of leakage in walls/floor space.. it serves to cool/heat a somewhat desired location (keep wood floors warmer, walls of interior space,etc).

When it comes to the cost of conditioning a space; the higher the dT between space and outside the worse the heating/cooling load. So as is often the case you can close a guest bedroom keeping it 15-10°F below thermostat Temp - resulting in ::slightly:: lower costs of that 100-150sqft. In the summer similar conditions can be seen on a very hot sunny day with west facing windows.... as high as 15-20°F (shaded air temp).

And yes the higher impact measure ... don't have wasted spare space... don't have unshaded west facing windows.... insulate more so as to not have a dT or neeed heat/cooling... but that isn't a low cost/no cost energy measure (which most people are looking for unfortunately)

As always thank you for your insight and time! great blog.

Dec 30, 2013 10:48 AM ET

Edited Dec 30, 2013 10:50 AM ET.

Response to Nick T
by Martin Holladay

I think it's safe to assume that (a) most of the homes in the California study had ductwork that was partially outside of the thermal envelope of the house, and (b) most of the homes in the California study had leaky ductwork.

One reason why it's safe to assume these conditions is that they are typical. We'd all love to see builders start putting ducts indoors, and we'd all love to see well-sealed ductwork. But in most areas of the country, it hasn't happened yet.

I recently heard a presentation (at the December 2013 Buildings 12 conference in Florida) by Iain Walker of LBNL on “Building Envelope and Duct Airtightness of New U.S. Dwellings.” According to Walker, "Duct leakage is low in Washington and high in New Mexico and Florida. ... Just over 1/3 of duct leakage in Florida is duct leakage to outside."

In regions of the country with basements, ducts are more likely to be indoors than in regions of the country with slab-on-grade homes.

Homes with forced-air distribution systems are much harder to zone than systems with hydronic distribution systems. Shutting off registers isn't good for the system, because the furnace or air handler needs a minimum air flow over the heat exchanger or over the indoor coil to operate properly. Shutting off registers causes more air to escape from leaks -- and most duct systems have leaks.

Dec 30, 2013 12:16 PM ET

"It's perfectly OK..."
by bob coleman

That reminds of Scott Adams' - Dilbert creator - acronym: (BOCTAOE) But of Course There Are Obvious Exceptions when presenting an argument or issue.

Dec 30, 2013 12:33 PM ET

Measured Impacts of Air Conditioner Condenser Shading
by bob coleman

Reading FSEC one report, it doesn't look like any striking conclusion can be made that it doesn't work, it just doesn't provide miracles, and may not be worth the cost.

If you can take advantage of free site planning and placement, it might be worth the time for the few % point gains. Also important to note that some shading attempts like that in the third experiment can have a negative affect.

Would be nice to see them or someone do a more controlled study; identical units located in the same environment at the same time with controlled output, one shaded, one not.

Dec 30, 2013 12:54 PM ET

Response to Bob Coleman
by Martin Holladay

Anyone choosing to compile an "energy-savings tips" list needs to prioritize. Ideally, these lists would start with tips that either result in significant energy savings, or which fall into the "big bang for your buck" category. Tips that result in only very small levels of energy savings, or which aren't particularly cost-effective, wouldn't make the list.

I'll quote from the July 1995 article from Energy Design Update, "The Nonbenefit of Shading Air Conditioners":

"The results of two-year field study by the Florida Solar Energy Center (FSEC) show that energy savings [resulting from shading air conditioners] are minuscule at best. ... The problem is that a typical 3-ton unit moves about 2,800 cubic feet of air per minute or 170,000 cubic feet per hour. In order for a shading device to be effective, it would have to shade the entire area in which that air is contained. ... Shading just the air conditioner does almost nothing, says [researcher Danny] Parker. Even at peak sunlight (1,000 watts per square meter), shading two-thirds of the sunlight form a 3-ton air conditioner would theoretically reduce the cooling air temperature by only 0.3 degrees F and thereby increase the air conditioner efficiency by less than half a percent. ...

"The results [of the study] show that the house with a trellis saved only 3% in energy and the house with plantings actually showed an increase of 18% in energy use after the shading was installed. Parker hypothesizes that the reason for the increased energy consumption was that the plantings caused some of the exhaust air to recirculate back into the air conditioner."

Dec 30, 2013 1:55 PM ET

You would never see the AMA or the CDC
by But Why?

write an article telling you washing your hands won't prevent cancer WITHOUT them also telling you that washing your hands will prevent many other diseases and should be done DESPITE not preventing cancer.

You would never see mechanics write an article telling you that changing your oil won't save you significantly at the pump without telling you that you still need to change your oil to prevent costly damage to you car.

Dec 30, 2013 2:02 PM ET

Edited Dec 30, 2013 2:14 PM ET.

Response to B.W.
by Martin Holladay

The focus of my article was to warn readers about energy-saving tips that are unsupported by data, so that readers who are interested in saving energy aren't waylaid by bad advice. The article was certainly too long; at 2,600 words, it violates all of the rules of blogging.

In spite of the article's length, many readers wish it were longer. I have tried to fill in the gaps in the Comments section by providing more documentation to support the statements made in the article.

You suggest that I should have included a section in my article explaining some of the useful characteristics and benefits of the measures that don't save energy.

Objection noted. In my defense, I assume that readers have common sense.

I will once again repeat what I wrote before: It's perfectly OK to engage in many of the activities listed on this page. It's OK to clean your refrigerator coils. It's OK to change your furnace filter frequently. It's OK to clean the reflectors under your stove burners. It's OK to cook with lids on your pots. Just don't expect any of these actions to save a significant amount of energy.

Dec 30, 2013 10:13 PM ET

Edited Dec 30, 2013 10:14 PM ET.

But why has no one taken my
by Robert Connor

But why has no one taken my advice about thinking about and limiting family size? That would help most of all. Or do you guys all have large families? Oh, let me guess, Jim Bob Duggar is a member of the GBA.

Dec 31, 2013 1:10 AM ET

hot water heaters
by David Goldman

Missing from the list is the advice I see alot from utilities: save fuel by lowering setting of the hot water heater. As far as I understand, heating the water to 140 deg can prevent Legionnaire's disease and when you use a fairly inexpensive mixing valve --which is required to prevent scalding--which mixes the outgoing house hot water temp down to 120 deg or less, then you increase the supply of hot water/output of the tank.

Dec 31, 2013 5:43 PM ET

Warmth through Alcoholic Fish
by Douglas Horgan

Great job as usual Martin! (Guess I'm in the intended demographic for your post.)
I'm definitely trying that fish tip!

Jan 1, 2014 11:58 AM ET

Edited Jan 1, 2014 12:46 PM ET.

HVAC Air Filters / Reliant Energy advice
by Mark Johnson

I can hardly believe I am defending Reliant Energy, but their advice to cook with a lid might be relevant to humidity in the house. As it is in hot-humid South Texas (mainly Houston), outdoor dewpoint may be 72F much of the summer and indoor humidity is often poorly controlled too. Something which reduces indoor humidity would indeed reduce the felt need for AC a bit, and there might actually be some energy savings. I bet too small to measure though.

I have something to say about HVAC filters too, the advice to change every 30 days reminds me of oil-change businesses' advice to change your car's motor oil every 3000 miles. As I write this it is New Years Day and some social and family matters call right now. I will post in 24-48 hours on the subject of filters.

Best wishes -- M. Johnson

Jan 1, 2014 12:05 PM ET

Edited Jan 1, 2014 12:24 PM ET.

Response to Mark Johnson
by Martin Holladay

After I deleted your second post, you deleted your first. That was unfortunate. Any chance you can recreate your excellent comments? I hope you can.

[The gist of Mark Johnson's accidentally deleted comments, which I hope he will soon recreate, was that he used a manometer to measure whether accumulating dust on his furnace filter would cause a reduction in airflow across the filter. After 5 years of continuous measurements, the original filter had still not caused a reduction in airflow, even though the filter was fuzzy and gray.]

Jan 1, 2014 2:07 PM ET

Furnace filters..
by Zolton Cohen


Geez, no good deed goes unpunished, eh? I LIKED the article and understood it. As far as I could discern, it wasn't designed to be a complete treatment or explanation of why those recommended practices aren't helpful in saving energy. Just a list...

On the subject of furnace filters though, I have a modest money-saving (though not necessarily energy-saving) tip. I virtually never change my filter. The one in my forced air gas system is probably 7-8 years old. But every month or so I remove it briefly and vacuum it off.

That takes just a few minutes and the filter works perfectly after the cleaning. If there are energy savings to be calculated, it could be that doing so removes from the equation driving to a store and buying a new filter. Or reducing the amount of trucking and packaging used to transport and protect a new filter.

It's a small thing. But we of the frugal persuasion take some pride in being, well, frugal.

Zolton Cohen

Jan 1, 2014 2:53 PM ET

saving energy in the aggregate
by Edward Krause

I agree some of these practices are stupid by any means of measurement, but others save energy in the aggregate even if they may not save significant money; simple little tasks or habits can have a significant impact on the overall energy usage when done by millions. The utilities may be implying individual households will see it on their monthly bill, when the utility is more concerned with the capacity of power plants, and, I would hope, the size of a carbon footprint over years. They may only save a household a few dimes. I agree there may be smarter ways -- more bang for the buck, or watts for the work -- to save both energy and money.

Jan 1, 2014 3:49 PM ET

Edited Jan 1, 2014 3:55 PM ET.

Shading , wall plugs, and light bulbs.
by Roger Williams

I have a problem with saying that sealing wall plugs does not save significant energy. It cost us ten dollars to buy the sealing foam kits to do the outside plugs. We noticed that the cold air was coming in the sockets. We took the foam removed from the kits and put them on the back of baby safety plugs from the dollar store. Reduced drafts were a great benefit. Maybe it only saved $5 a year, but that is a 50% ROI.

Shading a heat pump with deciduous trees cools the summer heat by a minimum of 10F and lets the sun shine into the area in winter. I see this as an advantage.

I replaced my light bulbs with CFL bulbs and got complaints from my wife on the quality of the light. I saw no difference in my power bill. In the summer we have 15 hours of daylight and in the winter the heat replaced some of the baseboard load. We now have LED bulbs and they are far superior light sources. We now heat with a heat pump and we may see a small difference in power consumption. 7.5% ROI, for the power to the lights is way better than the bank.

I know that if I had access to seal the attic the ROI would be great, but access would involve major holes in gables.

Jan 1, 2014 5:07 PM ET

Ducts in conditioned space with Recycle duct
by john walls

Martin, as a followup to Nick T's post and your response:
If you assume that all HVAC ducts in a forced-air system are in the conditioned space, then your concern was that the air handling system might not provide enough flow across the indoor coil for proper operation if you closed off a few rooms.
My question---If you have a GSHP (with all ducts in conditioned space) with a recycle duct/damper at the AHU to address low-flow zones, is that an energy hog, or is it efficient?

Jan 1, 2014 6:00 PM ET

Curtains and air conditioners.
by R Hunt

Happy holidays, great list. Funny stuff.
How about this one,, I don't think its been printed on any list, but I've certainly heard it often. "After using your oven in the winter, leave the door open to help heat the room" Or "keep the oven door closed to keep the heat in during the summer"
On the curtains, NOT Quilts. I suppose the possible small increase in energy consumption due to the minor convection currents that a curtain could set up is due to the very thin film of air on the colder surface of the window being drawn into the room at a faster rate than if the curtains were left open and there was no air movement across the window.. That statement kinda makes the case of keeping your AC condenser in the shade?? At least until the fan comes on and instantly removes all the slightly cooler air.... In that case, would wind chill have an effect on the condenser? Technically not, if its -10 out, and you measure the surface temp of a rock on the windy side of your house, it will be the same temp as a rock on the protected side. Of course, however, the condensation that forms on the fins of the condenser evaporate quicker when assisted with air movement, thereby increasing the evaporative cooling effect, or wind chill.
What about using curtains during the cooling season?
Well,, argument for the sake of arguing I guess. Like I said, Funny stuff...

Best wishes...

Jan 1, 2014 9:54 PM ET

Some random thoughts
by Curt Kinder

1) adding thermal mass (water jugs) to unused volume in fridge or freezer might help by lengthening compressor cycle times - more time in steady state operation. Likely savings, a few pennies, not worth navigating round the jugs while using the fridge.

2) Furnace filters - HVAC systems, to work efficiently, need plenty of the third letter "A", as in air flow. Reduced air flow reduces efficiency. Greatly reduced air flow endangers system compressor whose failure has little to do with energy but improves my (as an HVAC contractor) bottom line. That's not in my clients' best interests, though, so we do our best to always install systems with big, low pressure drop filters requiring less frequent changes.

Fouled air filters allow dust to foul evaporator coils and blower wheels. Say what you want, but when those components are fouled, system efficiency drops.

3) Curtains and blinds on windows in summer somewhat reduce solar gain. In winter they reduce radiated heat loss and increase occupant comfort. In both cases, relaxed thermostat settings provide similar comfort at some energy savings.

4) We very often close off air flow to some rooms via an interesting automatic process called zoning. It allows use of smaller systems and often keeps those smaller systems operating at lower capacities providing increased comfort and significant energy savings.

5) It is intuitive that a dirty refrigerator condenser coil will impede airflow and heat transfer. Just because researchers, whoever they may or may not be, have failed to construct a study or test apparatus in support of the relevant physics doesn't change them.

Jan 1, 2014 10:38 PM ET

air filters
by charles CAMPBELL

Kevin Dickson, MSME wrote, "A neglected furnace filter increases the odds that lint and pet hair will accumulate on the furnace motor. That will cause the motor to overheat, causing short cycling (which reduces furnace efficiency) and eventual motor failure."

Curt Kinder wrote, "Fouled air filters allow dust to foul evaporator coils and blower wheels."

It seems to me that the more clogged a filter is, the better it filters, because the larger pores become smaller and smaller. Therefore it seems more likely to me that the motor overheating is due to reduced airflow, not dust, lint and pet hair. However, as the filter clogs, the negative pressure in the return plenum rises, possibly causing the junk on the filter to be sucked into the plenum.

I guess I'm just asking whether we really know what contributes most to equipment failure, dust or lack of airflow?

Jan 2, 2014 7:10 AM ET

Response to Roger Williams (Comment #38)
by Martin Holladay

I'm glad that you were pleased at the performance of the foam gaskets that you installed behind the electrical cover plates on your outlets. I doubt that this measure saved you $5 a year, however. In any case, here is a better way to seal electrical outlets:

(a) Turn off the circuit breaker.

(b) Remove the cover plate.

(c) Carefully remove the screws holding the receptacle or switch in the box, and pull the receptacle or switch out into the room as much as possible.

(d) Seal the holes at the back of the box where the cables enter the box with caulk. Don't fill the box with canned spray foam.

(e) Caulk the gap between the drywall and the electrical box.

(f) Put everything back together.

This method will be more effective than using a foam gasket.

The outdoor air temperature is not reduced by shade, but hot people feel more comfortable in the shade than they do in the sun, because of the reduction in radiation.

I'm glad you like your LED lamps. You wrote that switching from incandescents to CFLs didn't lower your energy bill. This really isn't a matter of your impression; I'm not sure what happened in your house. The reduction in energy use is easy to measure in a lab (and in your home, if you have a meter). Swapping incandescents for CFLs is the single most cost-effective energy saving measure you can take.

Jan 2, 2014 7:12 AM ET

Edited Jan 2, 2014 7:14 AM ET.

Response to John Walls (Comment #39)
by Martin Holladay

Q. "If you have a GSHP (with all ducts in conditioned space) with a recycle duct/damper at the AHU to address low-flow zones, is that an energy hog, or is it efficient?"

A. I'm not sure, because I don't know what a "recycle duct/damper" is. Perhaps a GBA reader who is familiar with this type of system can respond.

Jan 2, 2014 7:17 AM ET

Edited Jan 2, 2014 8:47 AM ET.

Response to R. Hunt (Comment #40)
by Martin Holladay

R. Hunt,
Q. "What about using curtains during the cooling season?"

A. Closing your curtains can reduce solar heat gain during the summer, but the measure isn't anywhere near as effective as exterior shading. When you pull your curtains shut, the sun enters the home and heats up the curtains. On the other hand, if you have an exterior awning, the solar heat will never enter your house in the first place.

Jan 2, 2014 7:23 AM ET

Response to Charles Campbell (Comment #42)
by Martin Holladay

Q. "I'm just asking whether we really know what contributes most to equipment failure, dust or lack of airflow?"

A. I imagine that either phenomenon could cause equipment failure. To clarify:

(a) I recommend that duct systems be well designed. Oversized ducts are always preferable to undersized ducts. High static pressure makes your air handler fan work harder and raises your energy bills. Big ducts and big filters are good.

(b) I don't recommend that anyone run their equipment with a dirty filter. By all means, when your filter is dirty, change it.

(c) It's true that a dirty filter makes a more effective filter than a clean filter. But it also makes your fan motor work harder, so it is undesirable.

Jan 2, 2014 8:36 AM ET

Edited Jan 2, 2014 8:37 AM ET.

A comment from Steve Easley
by Martin Holladay

I just received an e-mail from Steve Easley. The subject line of his e-mail read, "What happens when you close your blinds to save energy..."

Steve wrote, "Per Item 10 on your 'Stupid Tips to Save Energy.' I took this photo in an Indiana home a few years back. The folks closed their blinds to save energy and could not figure why their windows were growing mold. I think it speaks for itself…."


Damp window behind blinds - Steve Easley.jpg

Jan 2, 2014 11:56 AM ET

Edited Jan 2, 2014 12:04 PM ET.

HVAC Air Filters
by Mark Johnson

I would like to question the thinking behind the HVAC advice "change your filter every 30 days". My theory this comes from two sources: 1) the desire to assume conditions rather than measure them, and 2) selling more filters with a short estimate of lifetime.

Directly this matter would be expected to save little energy, but energy is wasted whenever you consume more stuff than you actually need. Usually the issue with HVAC filters is whether it would tip a forced air system into one which actually malfunctions.

Over 5 years ago, I heard about a Carrier high end control system which I understood to measure air flow and tell the homeowner to change the filter when the back pressure (called External Static Pressure, or ESP) rose by a measured amount. Some Dwyer liquid manometers were being sold cheaply, so I bought one and attached it to my HVAC system in order to mimic this. Although I watched the system ESP frequently, decided to wait until I saw some measurable ESP rise before I changed the filter. And waited, and waited, until 5+ years had passed and I finally decided there must be other reasons to change the filters.

Dust had accumulated on the filter face until extremely dirty, they looked like grey felt, yet there was no measurable rise in ESP and therefore no meaningful drop in airflow. Probably a factor in this is very generous filter area, with the 3.5 ton system 1400 cfm system I have and TWO 20*30 filters, this is perhaps twice the average. For that reason I would never advise another person to repeat this experiment unless they could closely monitor its progress, if a filter significantly reduces air flow then it can cause malfunctions and possible costly repairs, as well as people discomfort in the house.

You often hear HVAC technicians admonishing one not to buy 3M Filtrete brand filters, on the assumption that they are "too restrictive". A variation on this advice I have heard is, 3M Filtretes are okay at first but load up quicker than other filters and are then more restrictive. When dust loads up on the filter, it actually improves its ability to screen out particles, but also it is said to increase back pressure. I am sure the stories about a filter being bowed in its frame due to air pressure, are not made up. But I submit the theory that problems actually stem from a poor design with a very small filter area compared to the air flow needed. Again, let me remind you my experiment was with a very large filter area.

When professionals measure filter performance, they take into account the air speed at the filter face. This is an inverse number vs. filter area. One tester I saw, used air speeds of 300, 400, and 500 fpm (feet per minute) when testing 20 different filters. This is consistent with the rule of thumb "one sqft per ton of AC" -- 400 cfm through 1 square foot = 400 fpm. This rule of thumb is much spoken about , sometimes violated for convenience, so there are many houses putting more stress on their filters. On my own system, I calculated filter face speed and it is well under 200 fpm which might explain much of my observations.

The advice to change filters once/month is often said and I understand people rarely honor it. Rather than monthly filter changes, I believe most people would be better off to add return capacity (and filter) area until they are above average -- I have been consistently advised by professionals there is no real downside to this, so go big if you can. The energy savings will be not in your electric bill, but in the reduced manufacturing where you can forego buying a $20 filter every month.

Jan 2, 2014 12:18 PM ET

Response to Mark Johnson
by Martin Holladay

Thanks for your comments, and your account of an interesting experiment.

Jan 2, 2014 12:45 PM ET

Proper Window Coverings Do Save Energy -
by Gordon Clements

We have focussed our Vermont based window coverings business on the practical side of comfort and energy savings for the last 28 years - including weighted thermal lined drapes, Warm Window, Window Quilt etc. About 10 years ago we concluded the most attractive, durable, easy to install, cost effective product to be insulating double cell honeycomb shades made from bonded polyester fabric. About 10 years ago we added side tracks and fuzz bar to reduce air circulation and branded them EcoSmart Insulating Shades. They have been tested by your own organization (GBA-Peter Yost), Harvard Properties, Carb (Winters, Aldrich), EnergyBalance (Andy Shapiro) and found effective. Doing thousands of homes a year, and surveying every one, I can also say anecdotally and emphatically that customers agree - and return to make repeated purchases. (Our repeat customer base 65%.) In essence there is less draft or radiant heat loss so less impulse to turn up the thermostat. We also encourage their use to take advantage of solar heat gain when available with the shades open, then close them to block heat loss. And the reverse in summer - I also find personally that using our ceiling fans, and following this regime allows us to get away without A/C in summer - and it does get hot in VT in summer! Some of our customer comments are sometimes almost too dramatic to believe, but may be attributable to the fact they have a tool that works to make them warmer and more comfortable - along with many other benefits. I believe that compared to alternatives insulating cellular shades with 4-sided seals, are cost effective and therefore warrant an "Energy Saving Tip".

Re Steve Early's picture - I hear about mold issues from building professionals all the time - but not from hundred's of thousands of customers who actually live with the shades. Two points to the comment:
1. The Harvard study found that mini blinds, as shown in this picture, actually increased energy consumption with the average inside/outside temperature differential 26 degrees with minis, 33 degrees bare glass, and 37 degrees with EcoSmart shades. Gas consumption on average was 48 therms with EcoSmart Shades verses 68 therms with minis. Unfortunately this is the largest selling window covering in the US.

As for mold, insulating a window between exterior cold air and warm, moist indoor air will make it colder and therefore condense out some of that moisture. There are ways to reduce this - by reducing the humidity, which may be a good idea for any number of reasons, and/or reduce the glass temperature difference. The latter, by definition, will also reduce the shade's effectiveness. Bottom line, if we get 2 or 3 complaints about condensation a year it is a lot - and as a % fewer complaints from any other product for any other reason. Those customers who do have a condensation problem feel it is worth it to wipe up the moisture in the morning because the shade is working. That there are many other things they do to save energy and stay warm that take a lot more effort.
In conclusion I wish GBA would say more emphatically that homes in cold climate with conventional single or double pane windows, which represent the majority in the US, would benefit from insulating cellular shades that provide a 4 sided seal if they are used appropriately - which your own study shows they would be. That homes would be more comfortable and would consume a lot less energy. After all, conservation is the best route to our energy problem.

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