Reuben's Home Inspection Blog

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Insulation Blankets For Water Heaters

New water heaters don't need insulation blankets. Many generations of water heaters ago, insulation blankets helped to retain some of the heat that water heaters would lose through poorly insulated tanks, but today's water heaters are insulated well enough to not need extra insulation. The US Department of Energy recommends installing an insulation blanket if the insulation value of your water heater is less than R-24, but they also say that if you don't know the R-Value, touch the outside of your water heater. If it's hot, you should insulate it.

I did some research on my own water heater, which is a 2005 GE 50 gallon (manufactured by Rheem). From everything I've read, this water heater has an insulating value of somewhere between R-8 and R-16. I have the temperature set so the water comes out at 120 degrees, which is as hot as you should have your water heater set to prevent scalding. As you can see from the photo below, the outside temperature of the tank is at about 68 degrees, and the temperature in the room is about 66 degrees. According to my test, and according to the manufacturers recommendations (Rheem, AO Smith), an insulation blanket is not necessary. 

Dsc03783

If you have an old water heater that actually does get warm to the touch at the exterior, get a new one!  No, but seriously, be very careful installing insulation. Most water heaters are gas fired, and there are many areas that need to be left uncovered; the warning labels, the top of the water heater, the pressure relief valve, the control and access panel, and any bottom air inlets. Out of all the water heaters that I've seen that have been insulated, not one has followed these instructions; the warning labels are always covered, the pressure relief valves are almost always covered, and the tops of the water heaters are frequently covered.

The bottom line is that insulation blankets for water heaters are mostly a thing of the past, are difficult to install properly, and are generally not recommended.

Reuben Saltzman, Structure Tech Home Inspections - Email - Minneapolis Home Inspections

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 36 commentsReuben Saltzman • March 19 2009 06:25AM

Comments

Reuben, really good post, I have an experiment for you to try----take a piece of insulation board about 12" square and 1" thick (score it every couple of inches to allow it to bend easier) and tape it to the tank where you are pointing your lazer.  Go back a couple of hours later and stick your hand between the insulation and the water heater.  I think you will see that the tank is still loosing tremendous amounts of heat to the room.  I personally think that the manufacturers should be required to insulate the tanks to a minimum of 4" of foam---R-38 or higher.  Another thing that I would add about older water heaters is that if the tank feels "really" warm it can mean that the insulation is wet.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Thanks for the idea, I'll try it.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Hey Reuben, good information, I need to pass this on to my dad to prove the point.

Posted by Tad Petersen / Home Inspector, Mpls (Safeguard Home Inspections, Inc.) over 9 years ago

When insulation blankets first came on the market (I'm old so I remember this) they came with a caveat to only be used on electric water heaters.  They actually had warnings to not use them on gas.  Somehow all this got lost and we now see them on gas water heaters, complete with scorch marks and yellow flam due to combustion air being blocked.

Posted by David Helm, Bellingham, Wa. Licensed Home Insp (Helm Home Inspections) over 9 years ago

Reuben, Insulation blankets on gas water heaters were discovered to cause condensation problems and rot out the units. Is that your water heater in the picture with the copper tubing connection?

Charlie, I have put my hand between the insulation and tank and found it to be quite warm. I'm not sure what that proves. There is no doubt the tank is going to lose heat. More insulation means slower heat loss, but not no heat loss. More is better.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 9 years ago

James - yes, that's my water heater.  She's a beaut, huh? 

I've heard the same story about insulation blankets causing condensation problems, but it's folklore.  Think of the science behind it - how could condensation occur? 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Reuben, Folklore? Care to explain why it's folklore and give us the facts. I'm curious.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 9 years ago

James all I am saying is that there is never enough factory installed insulation on the tank to slow the loss down enough.  Gas water heaters are another whole issue as there is a flue up the center of the tank that will continually have air wiping heat off the surface and carrying it up the chimney regardless of how well the tank is insulated on the outside.  Couple that with risks of plugging air intakes and it is just plain not a good idea to even try to add insulation to those. Any time you have multiple vapor barriers around something that can leak you run risk of trapping moisture inside the envelope somewhere.  The problem though is the leaking---not the vapor barriers.  This brings me to perhaps the biggest issue I have with commercially available type tank blankets----Inspection and monitoring are not possible.  Installation of additional insulation should only be done in such a way that full inspection and monitoring of leaks is possible.  Not going to happen.  This gets back to requiring the manufacturer to install an actually useful amount of insulation around the tank to begin with.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Charlie, I agree, there is not enough insulation. I was stating that yes it is warm and that the tank insulation will not completely stop thermal loss of the tank. More insulation is better but as you said from the factory. Not by someone wrapping a blanket around the the thing because of the issues you just stated. Blankets are for the bed:)

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 9 years ago

James - my pleasure.  Condensation occurs when warm, moist air comes in contact with a cold surface.  Insulating a water heater won't lower the temperature of the water heater, it will only prevent some heat loss at the water heater.  Condensation can't possibly occur. 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

James, for sure.  I know of no commercially available blanket that isn't a waste of natural resources.  Fiberglass batt type insulation is a terrible way to stop heat loss on something that has temperatures as high as a water heater----and that is what they are all made of----usually R-5 or so----just plain a waste of money and someones time:)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Here is a picture of the 2" foam blanket I made for my heater.  The temperature reading is the surface of the tank where the plug that provides access to the thermostat and element had been removed.  Adding this much insulation cut my electrical usage by the heater by 50 percent----so I paid for the sheet of foam the first month.

Heater blanket

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Ok Charles, now you have me really curious!  My suspicion is that you're getting such a high reading because you're testing right above the heating element... but if it really lowered your water heater electric bill by 50%, that's substantial!  I have a sheet of that fancy reflective foil insulation taped to my water heater right now, and I'll get back to you with my findings. 

Do you get a similarly high reading when you test areas that are further away from the heating element?

ps - i love this stuff

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Charlie, What type of foam, EPS or polyisocyanurate. I would assume EPS, its more flexible.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 9 years ago

Reuben---doesn't matter where you shoot the temperature.

James it is polyisocyanurate.  It "bends" because the two inch strips are cut with a 2 degree bevel on each side of the strip allowing it to "bend" around the tank when installed---without leaving any voids.  The foil backing lends itself well to being taped with foil duct tape.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Here is another picture of what the "spaceship" looks like:)

Charlie's space ship----off to another planet

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Charles - my results are posted below.  It's not quite the difference in temperature that I was hoping for, but it's not a complete test either.  I didn't use the same type of insulation that you have, I didn't have it taped at the edges, and I didn't have it completely covering the water heater.  Maybe if I did all those things I would see a bigger difference.

InsulationTemperature of tank without insulationTemperature of tank immediately after insulation was removed

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Yes, Reuben, it is unlikely that the amount of insulation you used would make any more difference than what you show.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Plus you have about a 10% difference by adding what, R-1 or 2?

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Charles - tough to say what the R-value is.  This is a radiant heat insulator, so it really works best when it's not in contact with the water heater.  This is just what I had laying around in my basement.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

That stuff has some of the most "misleading" information as to R-value that I have ever seen.  It claims R-4 if you are stopping heat from going up---BUT---that value includes any dead air space on both sides of a closed test structure----very unrealistic in my opinion.  Corrugated cardboard would do the same thing.  Try your little test using a 1/4 inch (two layers) of cardboard.  I would be surprised if it doesn't show even more of a temperature difference.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Yeah, the numbers they come up with are goofy, I agree.  I used it under the floor of my kitchen where I installed electric heat pads.  It actually cut my energy use on the floor in half.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

The foil stuff, isn't it that duct insulation that looks like bubble wrap?

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 9 years ago

Yes, it does look like bubble wrap.  It actually works great under in-floor radiant heat - I don't think I would use it for anything else.  http://www.radiantguard.com/radiant-barrier-uses.aspx

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

The plumbers here, though, get about $250 for installing insulation blankets. I've heard -- but no proof -- that some water heater manufacturers will void the warranty if there is a problem and they can prove that the manufacturer's information and safety papers on the tank were covered and obscured from view.

Posted by Russel Ray, San Diego Business & Marketing Consultant & Photographer (Russel Ray) over 9 years ago

I was watching The Weather Channel last year when 'Homeowner tips' came on.

 

He showed how to save energy by installing an insulation blanket on the water heater. Of course, the water heater was located in a garage and not elevated.

Rheem's installation instructions more or less states their warranty is void if a blanket is installed (unless it's their blanket required by local code).

 

 

Posted by Darren Miller (About The House) over 9 years ago

I bet they installed it wrong on the news too, right?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

And what is the "actual" value of a water heater warranty?

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

A water heater warranty gives you a new water heater if the tank leaks.  It doesn't cover labor.  Water heaters come with 6, 9, or 12 year warranties.   I recently helped a friend replace a 3 year old water heater that started leaking, so it was worth about $400.  This was definitely an exception though. 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Reuben, I was being a little tongue in cheek:)  Someone would need to give me a specific reason why adding insulation would cause premature failure of the tank before I would think that insulating the tank would not outweight the value of the warranty---especially if pro-rating is involved.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 9 years ago

Good stuff Reuben. I always love learning something new when I come to read your blogs. I will have to do that test on my water heater for sure. Thanks for posting

Posted by Winston Westbrook (Westbrook National Real Estate Co) over 9 years ago

There are many other factors not being considered here on weather you should add insulation to a water heater, such as ambient temperature.  I am an energy manager for a consulting firm.  We have contracts with many utility company's around the country, and many of them pay to wrap customers water heaters. Utility companys have to justify the cost of doing this with the state regulatory boards, and in almost all cases, they are cost effective, especially in cold climates.

The idea that a tank can rust out prematurely because of a wrap is just plain false.  Condensaton happens when warm, moist air comes in contact with a cold surface ( below the dew point ) If the tank has extra insulation added to the outside, it acts exactly the same as the original insulation.  The surface of the tank is never below the dew point, becuse the extra insulation keeps the sureface warm.

Also, gas tanks can and should be inuslated as well.  Just don't cover the plate in the center in the bottom, and don't cover the top.  We have wrapped over 50,000 tanks over the past 17 years, and have never had a problem.

Posted by Ryan Wilkinson over 9 years ago

Ryan - care to expound on these other factors?  Do you have any numbers to back up your stance?  Since you make money insulating water heaters, I can understand how you would disagree with this blog, but you're also biased.

By the way, you copied my comment about condensation word for word. 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Reuben - I think you misunderstand my comments.  I make money implementing cost and energy saving measures deemed to be cost effective by utilitys and public power boards - not just inusulating water heaters.  I insulatate water heaters along with many other energy saving measures like hot water line insulation, low flow water fixtures, weatherstripping, foam gaskets, window plastic, ect. The only bias I have is towards conserving energy. So in other words, I do what the utility instructs me to do based on thier research of what is cost effective.

About the "other factors"

It appears that the water heater you are testing is in a basement?  I assume the temperature stays pretty moderate ( between 50 and 60 most of the year? That leaves a temperature difference of about 60-70 degrees between the ambient temp and the hot water in the tank.  In the northwest, many people have a water heater in a vented crawl space, or a garage, where the temperature could get as low as 30-40 degrees, leaving a temperature difference of 80-90 degrees. Also, many homes throughout california have the water heaters located outdoors where nightime temps dip into the upper 40's. Additional insulation is an obvious choice here.

How much are you paying for the blanket?  $250?  you will never recoup your investment and that would be a waste of $250. $25 - You will probably save enough in the first 1-2 years in most cases depending on the type of fuel and the cost per therm. The average life of a water heater is said to be between 10-15 years. If you only save 5$ per year in standby losses, you would pay for the blanket 4 times over. The numbers you are asking for are specific to the type and cost of fuel you are firing your water heater with. I am saying that in most cases, the cost of a $25 insulation blanket is justified by the energy savings.

Are you someone who uses a lot of hot water, or does your tank sit idle for most of the day?  Blankets only save on standby losses, so if your water heater is firing all day long for showers, dishwashing, laundry, ect you won't save a whole lot - because your water heater is firing all of the time anyway.  If you are someone who showers in the morning only, and doesn't do any laundry in hot during the day, you will save more, because your water heater is sitting idle all day, and not firing.

By the way, yes, I did echo your comments on condensation, but the comments are hardly word for word.  There are only so many ways to explain dew point and relative humidty.  Don't break your arm patting yourself on the back....

Posted by Ryan Wilkinson over 9 years ago

Ryan - thanks for the explanation.  Very helpful.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 9 years ago

Help i have a water heater (Gas) county inspecting moboile home park, live in Napa County they say we need a blanket so befor i buy one i remeber i was told when bought new wter heater didn't need blanket it is 30 gallon but still confused by your emails & answers. Thanks

Posted by Martha about 6 years ago

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