# Water Heater Insulation??



## Bob Mariani (Dec 1, 2008)

it is advisable to use this. BUT.... use it only on an electric water heater. not gas or oil fired ones.


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## stuart45 (Jun 20, 2009)

I put one on my old hot water cylinder and it did make a difference. Well worth it. All the new copper cylinders here have got factory applied insulation.


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## chrisn (Dec 23, 2007)

Begin by checking the owner's manual for your water heater. Some newer models specifically recommend that you do NOT use a heater blanket.If your water heater is warm to the touch your could probably use a blanket


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## Michael Thomas (Jan 27, 2008)

This is a somewhat controversial topic in the Home Inspection industry, especially as some local energy codes may require a blanket. A few things to keep in mind:

1) The listing of the appliance requires that the various labels be visible, people rarely bother to cut the blanket to expose them. 

2) If not properly installed the blanket may interfere with air flow to the draft hood, if it slips down it may obstruct movement of combustion air to the burners, it may also interfere with the operation and inspection of control and safety devices.

3) According to the manufacturers anyway, modern water heaters are don’t need a blanket:

http://www.hotwater.com/bulletin/tcb1.html

4) So a retro-fitted the blanket may actually decrease efficiency, see for example:

http://www.inspectorsjournal.com/forum/topic.asp?TOPIC_ID=3143

So if you do install a blanket, you want make sure it’s installed in compliance with the manufacturer's instructions, and inspect it regularly for slippage or damage.


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## Thurman (Feb 9, 2009)

Now, with all of that said- I agree that a blanket should not be used on a gas water heater. I agree that is may be controversial as far as covering up any pertinent labels/tags on the water heater. But, in my case: I bought/ installed a new Whirlpool Energy Smart electric water heater back in '04. This unit was supposed to be insulated with "new" insulation material and I installed it with no wrap. My water heater is in a dedicated closet in the hall of my house, very small. After installing the water heater I noticed that the closet was just as very warm as the old unit-before installing a water heater wrap. So, I installed a water heater wrap to prevent heat loss from making the closet too warm, and this worked. I should say the closet also has two small vents in the top to let excess warm air out, but it was just getting too hot for me to tolerate. So, water heater wraps do have some advantage depending on what you are trying to accomplish with them. David


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## mopowers (Jul 20, 2009)

Thanks guys. The water heater is brand new, and it is gas, so I won't be needed or using one.


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## toeey1 (Feb 10, 2010)

I thought about putting one of those on a few years ago but decided against it. I figured if the water heater wasnt warm anywhere on the outside, then heat loss was extrememly minimal


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## piste (Oct 7, 2009)

Bob Mariani said:


> it is advisable to use this. BUT.... use it only on an electric water heater. not gas or oil fired ones.


I've heard/read that a lot..dont' use on a gas heater..but NEVER heard/read any reason for that....so wrap my gas water heater I did!! I don't see any reason why not to if installed properly. What am I missing?


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## ferris13 (Sep 25, 2009)

piste said:


> I've heard/read that a lot..dont' use on a gas heater..but NEVER heard/read any reason for that....so wrap my gas water heater I did!! I don't see any reason why not to if installed properly. What am I missing?


 
I was interested in a response to Piste question also. I installed a blanket over my gas unit as well. Sounds like this is just an opinion.


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## beenthere (Oct 11, 2008)

Insulating gas or oil fired water haters can be a fire hazard. if the heater malfunctions.

Next, is on gas fired water heaters. Many people were putting the insulation over the burners air inlet, and causing either flame failure, or high CO and soot in the combusted gas.


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## piste (Oct 7, 2009)

beenthere said:


> Insulating gas or oil fired water haters can be a fire hazard. if the heater malfunctions.
> 
> Next, is on gas fired water heaters. Many people were putting the insulation over the burners air inlet, and causing either flame failure, or high CO and soot in the combusted gas.


Could you explain...that in the event of a heater malfunction...there is greater risk of fire hazard with oil/gas water heaters vs. electric water heaters??

Also, anything done incorrectly can cause a problem. If the issue is being sure not to put insulation over the burners air inlet...wouldn't the solution be to advise people to be sure not to do that...as opposed to the more drastic measure of not using the blanket at all.

Unless and until someone posts some clear and specific reason not to insulate a gas water heater...and despite the cautions against it on the blanket packaging itself....I'm gonna say there's no harm in doing so. Like anything in life...done incorrectly and it could be a problem...but I don't think it's that hard to install an insulating blanket on a gas water heater correctly.


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## beenthere (Oct 11, 2008)

piste said:


> Unless and until someone posts some clear and specific reason not to insulate a gas water heater...and despite the cautions against it on the blanket packaging itself....I'm gonna say there's no harm in doing so.



That is the kind of reasoning that gets people injured and or killed.
Because you don't understand why something shouldn't be done. It must be ok to do it.

Electric water heaters don't have a flame that can come back out a combustion air intake during a downdraft. 

Foil and vinyl wraps will burn, and produce toxic fumes.


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## piste (Oct 7, 2009)

beenthere said:


> That is the kind of reasoning that gets people injured and or killed.
> Because you don't understand why something shouldn't be done. It must be ok to do it.
> 
> Electric water heaters don't have a flame that can come back out a combustion air intake during a downdraft.
> ...


I hear what you are saying and take it to heart. On the other hand...a healthy scepticism goes along way toward seeking information, education, and understanding and not just doing (or not doing) something cuz someone(s) sez so. 

The vast majority of the surface area of a tank is...well ..just that...the closed surface area of the tank itself. One can very easily wrap the vast majority of that surface area without coming even close to blocking, impeding, or otherwise putting the material in a position where it would catch fire in the event of a "downdraft". Which...by the way...shouldn't or couldn't the gas flue have a backdraft prevention "valve" in the duct? And lastly...can you (or anyone) provide any documented examples of this risk actually coming to fruition?? ie. these so called fire breathing gas water heaters...

I suspect this recommendation not to wrap gas heaters at all is meant to protect many people against themselves....for those who need that.

In the end...if there is any risk...I can dig the recommendation not to wrap it given the relatively minor yet not insubstantial cost savings. Just trying to engage some intellectual discourse here...so I hope folks these comments in the spirit intended.


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## beenthere (Oct 11, 2008)

A backdraft can send a temp exceeding 800°F up the side of the tank. So even wrapping just the top 2' is a hazard.
The insulation can smolder for a long time before anyone notices a problem. If they even notice before the house is on fire.


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## Fraser20 (Feb 23, 2010)

nope cant say I have used that.


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## piste (Oct 7, 2009)

beenthere said:


> A backdraft can send a temp exceeding 800°F up the side of the tank. So even wrapping just the top 2' is a hazard.
> The insulation can smolder for a long time before anyone notices a problem. If they even notice before the house is on fire.


Is that before or after the molten lava comes spilling out?? 

Sorry but I find comments like this extremely difficult to believe..thus my inherent sceptism of anything I hear/read. Would you care to explain? Maybe I misunderstand but it sounds like you are saying that it is possible for the exterior of a water heater to realize temps exceeding 800 degrees??


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## Michael Thomas (Jan 27, 2008)

I believe the poster referring to "flame rollout":











which can indeed ignite the plastic jackets of water heater insulation blankets.


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## piste (Oct 7, 2009)

Michael Thomas said:


> I believe the poster referring to "flame rollout":
> 
> 
> 
> ...


Thanks. That looks scary. Couldn't or shouldn't flues have backdraft prevention mechanisms? I would think that'd be pretty easy to implement?

I'm also interested in any info on the extent of frequency of this sort of thing happening.


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## beenthere (Oct 11, 2008)

piste said:


> Is that before or after the molten lava comes spilling out??
> 
> Sorry but I find comments like this extremely difficult to believe..
> 
> ...


The above was not meant to be insulting. Only a suggestion that you stop being a skeptic on other things also. That relate to safety.

Yes it is possible to exceed 800°F, since the flame is much hotter then that.

800°F, would be a very cool gas flame.

The flue pipe of a gas fired water heater is 350 to 500°F depending on draft in the chimney.

The roll out damage during ignition or back draft conditions as Thomas posted isn't even an example of the worse damage that occurs.

Back draft protection would require the appliance to shut off.

Its best to correct the condition or cause of the back draft. Instead of just band aiding the symptom.

Unfortunately. You can't stop/correct all causes of back drafts, or roll outs.

So, you are not allowed to insulate gas or oil fired water heaters, to prevent fires.

Often, the temp of a backdrafting gas flame, is hotter then it the normal temp of the gas when its burning in the combustion chamber.


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## Michael Thomas (Jan 27, 2008)

There is no automatic protection against the common causes of flame rollout on residential water heaters (or other gas appliances such as furnaces and boilers, either).

Flame rollout is a pretty common event, I probably see it every 30 or 40 gas appliances I inspect to some extent, either as an active event when the appliance starts, or as evidenced by sooting or other damage to the appliance casing.

If it's a really dramatic event the flaming gas can shoot several feet out of the appliance, I've learned not to stick my nose in there when the burners ignite. It's also the case that if the access panels to the appliance are in place you can have substantial rollout inside the appliance which is not visible to exterior until the panel is removed and the burners ignite. Unfortunately, I've never been able to take a really good picture of a dramatic flame rollout situation even if I can easily repeat the problem, it just doesn't seem to photograph very well.

There can be many reasons for flame rollout situation, these include obstructed vents, positive pressurization of a common vent (you sometimes see this when a water heater is sharing a common and incorrect or defective vent with a higher BTU appliance such as a power induced draft furnace or boiler), insufficient combustion air, and/or negative pressurization of the environment surrounding the appliance (I've seen flaming gas continuously pulled out of water heater by a "small" commercial range hood installed in a custom kitchen on the floor above).

Bottom line is this is not an uncommon event, and though I've not personally seen a fire resulting from this cause, I can easily imagine how it could happen.


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## piste (Oct 7, 2009)

Thanks for the explanations guys. The insul blanket I got just says not to use on gas water heaters. The manufacturer could have been much more helpful to include a reference to the risk of backdraft, flame rollout etc. to help educate folks. They also should be making these insul blankets of flame retardant and non toxic materials. 

I'm gonna keep mine insulated...but just for kicks I think I might cut a section out roughly 12 inches around the air intake...then I'll take that removed section of insulation blanket and take a butane torch to it....might be interesting experiment.


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