Image Credit: Federal Trade Commission
More Musings of an Energy Nerd
Although I usually only publish one blog a week, I can’t resist posting a rare Saturday blog to rail against bad advice to homeowners from the Federal government and a national green building organization.
On December 8, I received an e-newsletter, “Energy Newsbriefs,” a usually reliable weekly publication from the Washington State University Extension Energy Program Library. The newsletter advised me to check out “Heating and Cooling Your Home,” described as “four-page 2009 fact sheet for consumers from the Federal Trade Commission [that] assists the homeowner in making decisions about home heating and cooling systems which may need replacement.” So I did.
Published by the FTC’s Bureau of Consumer Protection, the document includes an unusually high number of energy-saving tips that won’t save any energy. Included in the brochure’s “Tips for Lowering Your Monthly Energy Bill” are the following gems:
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35 Comments
It's no wonder
.... then add in all the local, self-proclaimed experts .... inspectors, contractors, and "green certified" realtors ... who may occasionally actually be right.
then garnish with the fact that for some options, and in some cases, there really is no simple, clear, single right answer (at the present level of understanding) ... and that there is debate on the options even among those with knowledge, good intentions, and nothing to sell ...
it's no wonder consumers hesitate to invest hard-earned bucks just because ******* says it's a good idea. And why would banks, and appraisers, and mortgagers want to hang their hats on something that may not work, or may be flavor of the month, or even a scam?
HVAC Tuneups
There is some value in checking the furnace periodically for heat exchanger leaks, on top of that, CO detectors should be in place. This is not an energy saving exercise but a safety and peace of mind one. I have a customer who is replacing a 15 year old furnace due to a hole in the heat exchanger, this is a direct vent appliance.
Flame sensors need to be cleaned every several years on certain furnace models, if dirty, the furnace will lock out and not restart. The new high efficiency furnaces are very touchy and I believe will need more regular maintenance than the old gas guzzling units they replaced.
Change the filter annually to save money
I manage a lot of furnaces (in houses) and whenever a blower motor fails, we find it's usually due to fuzz on the motor. The fuzz insulates it, which causes it to overheat and fail.
references
These tips are coming from what appear to be reliable sources. This serves as a cautionary tale to be careful of believing everything you read, even if from a normally reliable source. It is much better when a claim is backed up with solid references of scientific analysis. A good explanation of the reason why a recommendation is made may have to substitute if that is not available. That holds true, maybe even more so, when making counter claims against commonly held beliefs. With that in mind, are there good references for why you believe the claims you mention are not true?
I suspect you are right in most cases, but if we were to take that on faith, we would be guilty of doing exactly what others should not be doing. Namely, taking the word of an authority rather than relying on proof.
I would be particularly interested in a reference in the first item you mention regarding shades. I have long been skeptical of the claims made by many shade companies. However, I believe that a shade that is installed properly with side tracks and that seals at the top and bottom of the window would prevent convection and would reduce heat loss. If that were indeed the case, the claim made by the FTC would be correct under certain circumstances as might your counter claim under different circumstances.
Response to Daniel Beideck
Daniel,
Your skepticism and request for references to studies are both admirable.
First of all, the link at the bottom of the article sends you to a PowerPoint presentation by Michael Blasnik with more information and some of the references you seek. I'll repeat the link again here:
10 Simple Things That Really Don't Do Much.
You're exactly right about drapes and shades: they are only effective if they include air seals on all four sides. These seals can be found on Window Quilts, for example, that include plastic tracks on the sides, a tight valance at the top, and a Velcro closure at the bottom.
Absent the air-seal at the perimeter, the curtains just create a little tunnel allowing for a convection loop to develop. Such a convection loop can result in greater heat loss than if the curtains are left open.
Note that the brochure that distressed me said none of this. It did not advise homeowners to go out and buy a Window Quilt with a perimeter air seal. Instead, it provided this advice: “Use drapes and shades to help prevent … heat loss on chilly winter nights.” That's irresponsible.
More data on drapes
Daniel,
Here's a link to an fact sheet on window quilts:
http://learningstore.uwex.edu/assets/pdfs/B3064.pdf
The fact sheet includes a table showing that loose drapes can save between 1% and 4% of the energy leaving through the window -- such a small percentage that the typical homeowner wouldn't notice the savings. Other researchers have shown that some curtains actually increase heat loss, but I haven't found a link to the reference yet.
More information on curtains
Daniel,
Here's a report from the CCHRC that explains why ordinary curtains may cause damage due to condensation, while providing few energy benefits:
http://cchrc.org/docs/reports/window_insulation_final.pdf
More on curtains
Daniel,
Below is an illustration from "Insulated Window Treatments and Coverings," published by the University of Maine Extension Program.
The caption reads, "Without a cornice (left), draperies allow air to convect across the window, losing heat. A closed cornice (right) deflects circulating air to the interior."
Thanks
Thanks for pointing out that presentation (again). It looks like it would have been a very interesting talk. However, like most powerpoints, it’s a bit of a difficult read separated from the talk itself.
It seems to me that energy efficiency discussions often rely too much on word of mouth, rules of thumb, gut feelings and other anatomical references. We need more measurements, calculations, analysis and hard references. Claims of energy savings need to come with a calculation that shows the math!
curtains
I see the "curtain myth" come up repeatedly, followed by inevitable discussions of convection currents, etc.
What's missing from all these discussions is any mention of the other heat transfer mechanism: radiation.
A person's experience of temperature is a function of both the room air temperature and the mean radiant temperature. A window, particularly a single pane window, is going to have a lower interior surface (and thus radiant) temperature than will the wall, so covering the window (and eliminating this cold surface) can raise the subjective experience of occupant temperature for a given air temperature. There's a potential energy savings here, since the same effect could be achieved by burning additional fuel to raise the air temperature to compensate for the low radiant temperature.
Of course, the effect is not going to be large enough to show up distinctly in your energy bill. But it can still make a real, perceivable difference to thermal comfort.
curtains
I have to agree with Brent - I made a similar point on a recent Q&A thead:
https://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/22636/insulating-window-treatments
Good to remember though that, like a ceiling fan for summer cooling, it only makes sense if there's a warm body nearby to reap the benefits.
Response to Brent
Brent,
You are right about the advantages in comfort to a person sitting near a window. However, the brochure in question did not address that issue. The brochure referred to reducing heat loss.
My other pet peeve - "unplug everything"
It's a sad convergence of public awareness of vampire power and manufacturers figuring it out as well - now we have people diligently unplugging their iPhone chargers which, really draw almost nothing. There's more to be gained by actually prioritizing your unplugs by measuring with something like a Kill-A-Watt first.
Oh, and I sometimes hear of people diligently unpluging things like table lamps which have an actual hard off switch! So again, I wish it could be communicated as "measure, then unplug."
Response to comment #11
Yes, a ceiling fan is only useful for cooling when there is a person near enough to benefit from convestive and evaporative cooling. However, this analogy fails for the radiation-blocking effects of drapes. All surfaces in a house that have a line-of-sight to an uncovered window will radiate towards the cooler surfaces of the outdoors and to the sky. The cooled indoor surfaces will take heat form the indoor air.
Response to J. Wing
J.,
You're right. But first of all, an empty chair will be at 72°F, while a person's skin might be at 95°F, so the amount of radiation from a person is more than the amount of radiation from an empty chair.
Moreover, I don't think that any advantage gained by preventing radiation from an empty chair to a cold window overrides the losses that occur from convection through the tunnel created by drawing the curtains closed.
curtains and shades for solar heat gain
I had installed double cellular shades without side seals and found everything I see here about the heat loss to be true. Didn't save nearly as much with heating as expected and have condensation problems. Where they seem to make the more dramatic difference was solar heat gain in the summer. We installed translucent ones that don't darken the rooms so they can be left closed all the time during the day without feeling like you are in a cave. After reading all this I feel like I was led astray about heat savings, but are there any studies to measure curtains and shades effect on solar heat gain to back up my assessment that they accomplish a lot there?
Response to Jayne Masternak
Jayne,
Unfortunately, I don't know of any studies that can provide the data you are looking for. Perhaps another GBA reader will chime in with more information.
In the meantime, here is some more information from the GBA website on interior shades:
Window Shades, Blinds, and Awnings
Do Window Shades Save Energy?
Great catches
Nice job catching those questionable suggestions. Although there is certainly varying opinions/information about how effective some of the FTC's recommendations are, it's still worth pointing them out so that consumers can understand the pros and cons to each - rather than just take the suggestion for granted at face value.
energy savings myths
The cost of the filters and checkup are likely to be more than any possible energy savings.
It seems like the author has confused "energy savings" (reduction in the use and consumption of fossil fuels - or your own generated electricity) with "economic" savings. Isn't the goal of sustainable building and energy conservation practices to actually reduce energy consumption? It is just too easy to confuse the two, which could result in giving more misinformation.
Response to Stephen Stuart
Stephen,
You raise an important point, and I'd be happy to address it.
Here's my take on the issue: any energy-saving tip addressed to homeowners needs to take cost into consideration. To take an extreme example, a guy in New Jersey tried to build a zero-energy house a few years ago by investing over a million dollars in a huge PV array that separated water (using electolysis) into oxygen and hydrogen. He then stored the hydrogen in huge tanks and burned the hydrogen during the winter to heat his house and generate electricity.
It's possible to argue that he saved energy (after all, he stopped buying electricity and natural gas -- I think), but at such a ridiculous cost that his experiment is irrelevant (even stupid).
So, if you are a government agency providing advice to homeowners, you need to start with the low-hanging fruit. That means you need to tell people which energy retrofit measures will save the most energy for the least cost. Until the list includes all the items with a payback of 7 years or less -- and this FTC list did not -- there is no possible justification for including advice on ways to spend $200 in order to save $50. (Very few Americans want advice on how to spend $200 in order to save $50.)
Attic Floor Pits
In the matter of lugging air leaks, I object to the statement: It’s a job for a home-performance contractor equipped with a blower door.
Please read this post:
http://energyconservationhowto.blogspot.com/2009/09/sealing-attic-floor-pits.html
and this tab at my web page:
https://sites.google.com/site/phillipnormanatticaccess/Home/floor-sealing
I will always find savings opportunities in sealing an attic floor that are detectable only by down-and-dirty exploration. Sealing motivated only by reducing infiltration as measured by a blower door, will miss most savings opportunities. Tying sealing to blower door testing excludes most weatherization from sponsor incentives for floor sealing, and gives a wrong message to home owners.
Response to Phillip Norman
Phillip,
The issue you raise boils down to this: if you want to seal the air leaks in an old, leaky, house, is this a job for the homeowner or a home-performance contractor with a blower door?
You're quite right that my two sentences -- “Finding and plugging the real leaks is not 'a simple task for anyone.' It’s a job for a home-performance contractor equipped with a blower door” -- don't tell the whole story. It's more complicated than that.
A smart, educated homeowner who is capable with tools and has studied air leakage issues can tackle air leaks in basements and attics, even if they don't have a blower door. However, such homeowners aren't typical.
I have devoted much of my professional career to educating homeowners and builders on these issues, and I continue to dedicate myself to homeowner education here at GBA. So I have no problem educating homeowners and empowering them. If, after learning about these issues at GBA (or your website), a homeowner wants to tackle an attic air-sealing job, that's great. I hope they won't miss the tricky bypasses and the kitchen soffits covered by dusty batts.
However, the main point of my two-sentence opinion was in reaction the the USGBC's glib pronouncement on air sealing. The document in question said, “Plug Air Leaks. ... Common leaks occur around windows, doors, and other wall penetrations. Plugging those leaks with weather stripping and caulk can be a simple task for anyone! Savings: Reduce your energy bill by $100 per year or more!” This is inaccurate. The "common leaks" listed are inconsequential in comparison with the real leaks. Weatherstripping and caulking windows won't address the "attic floor pits" shown in the links you provided, as you clearly understand.
So that's my point -- the USGBC brochure provided bad advice. Homeowners need real information, not glib pronouncements about caulking windows.
Curtains v. Shades
Thanks, Martin for a good post, and for referencing Michael Blasnik.
A couple of things--first, shades are somewhat different than drapes/curtains, even without a sealed perimeter. Most non-roller shades are installed with a interior mount configuration, more closely resembling your curtains+cornice example than the open curtain example. since this is closed at the top, it should impact the convective looping--but I'm not aware of the research on this. Can you point to any?
Second, shades/drapes can have a very big effect on mean-radiant temperature, and thus occupant comfort. Higher mean-radiant temperature when your body "sees" a warmer interior shade can result in greater comfort at a lower air-temperature setting. I've experienced this at a 3-4 degree lower air-temperature, and I suspect in some cases, it could be more. A 3-4 degree lower heat setting, can have a real impact on energy use that wouldn't be possible from an apples-to-apples comfort perspective. This isn't to suggest that your assertion was wrong--just a caution against over simplifying--which I think is in part your point!
And not opening the curtains/shades to take advantage of solar gain during the day can be a big mistake.
The biggest danger in all of this from my perspective is the without a seal between the curtain/shade that is tighter than the window itself, you're setting yourself out for a terrible condensation problem as the warm humid indoor air strikes a window pane that might be even colder than normal--an excellent way to promote mold and rot.
As always, Martin, great stuff!
Thanks,
Mike
Shades and curtains
I disagree with you disagreeing with the "shades and curtains" statements, from my own expierience. For example, in our living room with the couch placed against a wall with two large windows, in cold winter nights you could always feel cold air "breathing down your neck", due to convection. In this and many other windows we installed honeycomb shades that, while not providing an airtight fit, fit with less than a 1/4" gap in any place. The convection currents inside the room are almost completely eliminated. The shades act similar to additional window panes (not so efficient but still noticeable). While I cannot scientifically prove our savings, the fact that less cold (cooled down) air is circulating the room, is self-evident to me that shades do provide energy savings.
Response to Christoph Wienands
Christoph,
Obviously, the smaller the perimeter gaps, the better the performance. I'm glad you found a brand that you are satisfied with.
FANS NOT HELP IN WINTER?
I always thought that having the fans on with a light upflow helped move the warm air around - especially if there are dead spots with little air movement... Based on reading some of the comments, I'm lead to think that this falsehood lies in the convection currents at work here, but I'd love a slightly more long-winded version.
Anyone able to give me a hand here...?
Thanks!
Response to Nathan Clark
Nathan,
You are absolutely right that running a ceiling fan during the winter helps move the air around.
It also wastes electricity. If a person is in the room, "moving the air around" will probably make the person feel a little cooler, since moving air tends to give people a chill. So that person is likely to turn up the thermostat, wasting energy.
The bottom line is that there has never been any evidence showing that turning on a ceiling fan saves energy during the winter.
RESPONSE TO MARTIN HOLLADAY
Thanks for the clarification... Strictly speaking in terms of saving energy I agree. I use wood heat in the winter and the fan helps move that air around so that on spot isn't 90 and another 55 :)
Thankfully, what we use in wood + elec < only Oil!
Response to Christoph Wienands
I don't disagree that curtains and shades give the perception that you are saving energy. After installing expensive blinds throughout our house (much like you describe, not sealed but very tight fitting) we thought the same thing, because sitting next to the window was more comfortable & you could feel the cold if you raised the blind. No other changes to the house or heating habits and the first winter we were lucky if we saved 50 gals of propane. Had the boiler serviced and the 2nd winter wasn't any better. After reading this blog, I have to accept defeat. Luckily I like their look as window treatments (I like the clean look and hate curtains), so I don't feel so bad about the money spent, because they definitely aren't saving much energy$. I suspect they have done better in the cooling season with solar gain, but can't tell for sure dollar wise because we had too many varying factors that affect the electric bill. This winter is starting out better, but this spring I sealed penetrations in the attic including the kitchen soffit with recessed fixtures. Yeah I know Martin, I should have done that first. If my back holds out, I hope to continue by insulating and sealing the rafter bays and adding more blown in cellulose insulation to the attic. It will be dollars better spent as far as saving energy. Keep pointing us in the right direction Martin.
Energy Saving Information
The DOE just completed a major upgrade to its energy savers booklet. Date on the new guide is December 2011. URL is http://www.energysavers.gov/pdfs/energy_savers.pdf.
Since this is possibly the gold standard for energy information from the government, it would be useful to get Martin's comments as well as Michael.
As far as getting good information from a "national green building organization", it should be understood that USGBC is not that interested in saving energy. I hope readers know about the lawsuit that Henry Gifford filed that challenged the LEED energy statistics. This has been covered in a small book I wrote entitled The Green Tragedy - LEED's Lost Decade at http://www.communitysolution.org/greentragbk.html. It can be downloaded at no charge.
Green Marketing may do us all in.
Another embarrassing list of tips
Pat Murphy just e-mailed me a link to a Green America document that includes several tips that are off base:
10 Easiest Ways to Cut Your Energy Use in Half
Among the tips:
"Install Energy Star ceiling fans in the rooms you use most often. ... In the winter, switch them to turn clockwise to circulate the warm air rising up to the ceiling back down into the room."
"Clean the coils on your fridge every six months to keep it running efficiently, and take up unused space with jugs of water, which will hold in the cold better."
Help me with this one, now... it will "hold in the cold better"? Now that's a technical explanation if I ever heard one...
Boiler Cleaning
Martin,
Very good post and interesting topic. I am curious about your statement that an annual or bi-annual cleaning of a boiler won't improve efficiency. I suppose I can see that for NG or propane but we are in Maine were 80% of homes heat with fuel oil.
If you go look at an oil boiler which hasn't been cleaned in 3 or 4 years the heat exchanger is often caked with soot and the flue passages nearly completely occluded. Is it really possible that a boiler cleaning in this case won't improve the efficiency of the boiler? I'd be interested to see the data if you have some.
Thanks
~Fortunat
Response to Fortunat Mueller
Fortunat,
Thanks for your comment. I'll repeat something I have written in response to other comments: performing many of these "bad tips" may make sense. I'm not saying you shouldn't do them. Just don't expect them to save energy.
There are lots of reasons to clean a furnace or boiler. Certainly, any oil-fired boiler with a history of being regularly caked with soot is a prime candidate for regular cleaning. So, by all means, schedule the cleaning.
The studies I have seen have looked at hundreds of homes -- some with furnaces, some with boilers; some burning natural gas, some burning fuel oil. On average, the cost of annual cleaning cannot be justified by anticipated average energy savings.
(By the way, gas-fired furnaces are likely to burn cleaner than oil-fired boilers.)
Window Treatments
My house being built on Cape Cod has triple pane, Argon filled, casement, awning or fixed windows. A three foot overhanging roof protects concrete slab from summer sun. Any curtains will be for visual privacy. A solar heat expert told me to install cheap windows and window quilts. Obviously I paid him no heed. FYI - R-30 slab, R-45 walls, R-100 deiling, mini-spli heating, HRV ventalation.
Response to Don Mallinson
Don,
Sounds like a nice house.
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