Water heater blanket

JetMech · May 2008

Are there any better insulation blankets available besides the ones at Home Depot? I thought I read in one of the HP magazines something about a reflective blanket. Also something about a type that didn't get taped together. Any ideas?

BB. · May 2008

Re: Water heater blanket

One time I used a roll of regular foil backed R15 (or whatever) wall insulation and a bunch of metal duct tape (this stuff sticks--regular duck tape fails after a few months no matter what or where or how it is stuck).

Many (all?) water heaters have big warnings to either not insulate them, or avoid covering controls, air inlets and exhaust (if gas fired).

I just replaced a 50 gallon water heater... the existing one (was a good brand/quality) about 15 years old and I replaced with another 12 year self cleaning model. The new one used about 25% less gas than the old one (according to the yellow tag--and assuming the testing method has not changed in 15 years).

The new one probably had thicker insulation (about 1" thicker?) and also included two 24" black foam insulators for the in/out pipes, and another foam piece that goes over the TP safety valve.

Lastly, it also included a "sealed" burner area (to prevent gasoline fume flash-overs?)...

From checking around on the web... New water heaters need to have R12 minimum insulation and some now have as high as R35 insulation... Adding a bat of 4" thick R15 insulation may not help much (let alone the 1"-2" thick insulation I typically see at the home improvement stores)--and may be dangerous to use on one like the model I just installed with the "sealed" burner.

The combustion air vents for some of these new style water heaters are on the lower sides of the unit instead of at the bottom. If your insulation slips down and covers the vent holes (tape fails, kids play with), etc., it could cause real problems (carbon monoxide, snuff out the flame and cause natural gas build up, etc.)...

If you have a good quality modern hot water heater, just using the foam pipe covers and insulating anything hot (like the TP valve) is about all you would need to do.

-Bill

JetMech · May 2008

Re: Water heater blanket

Mine is electric and also says not to add insulation but EVERY place you read about energy savings says to add insulation, especially since it's next to a concrete wall. Since it IS electric and not gas, what harm would adding insulation do? I already have foam insulation on every accessible hot-water pipe I can get to.

BB. · May 2008

Re: Water heater blanket

In theory, it probably violates UL/NRTL testing of the water heater... The thermostats and wiring will run much hotter now, if there is a short/overheated wiring--it can smolder under the insulation, etc...

In reality, cover the thing up with insulation and forget about it... The government says that it will save about 4% to 9% of your electrical costs...

You might also call up your utility and see if they have any Time Of Use plans, or interruptible service options--If you put your heavy power users on it--you might even save more money.

-Bill

JetMech · May 2008

Re: Water heater blanket

Yep, I don't see much of a problem myself. Hopefully it will become a SHW storage tank later this year anyway and only need to heat up on occasion.

System2 · May 2008

Re: Water heater blanket

Both myself and my parents have used extra insulation around our electric heaters for well over 20 years. We used a foot or more of fiberglass. The only problem we encountered was a reduction in income for Nova Scotia Power Corp, which caused them to raise their rates to cover their losses. Haha
Another interesting thing, I worked away all week, so would shut off my 20 gal heater Sunday morning and when I got back home Friday evening, the water was still hot enough for a shower. With all the extra insulation, it makes no sense to purchase a timer to turn it off at night. Why shut it off when it won't run anyway

Wayne

Telco · May 2008

Re: Water heater blanket

Have you thought about heavily insulating the walls of the heater closet rather than insulating the heater itself? Wonder what 4 inches of spray-in foam inside the closet walls would do for it? Hmm, going to add that to the house plans.

mike95490 · May 2008

Re: Water heater blanket

Telco wrote: »

Have you thought about heavily insulating the walls of the heater closet rather than insulating the heater itself? Wonder what 4 inches of spray-in foam inside the closet walls would do for it? Hmm, going to add that to the house plans.

What's the fire hazard of the spray foam ? I'd be tempted to use 2x6 studs, and fill with fiberglass, and then drywall, stay within the fire codes.

<edit> I guess if you have a Gas Burner heater, there is some sort of min inlet combustion air vent required.

JetMech · May 2008

Re: Water heater blanket

There's an idea...I do plan on finishing the basement...one day. But for now, it's in an open area, the entire basement. But still only a few inches from a wall.

Telco · May 2008

Re: Water heater blanket

Fire hazard shouldn't be any worse than anything else within a few inches of it. The hot water heater in my house has enough room around it to allow a 3 inch coat of foam on the wall and still have a little room between the foam and heater. If this is a concern, then a little less foam, and fire rated sheetrock would fit the bill. Suggesting the foam over fiberglass due to R value per inch, foam's more insulating. The advantage to foam over a wrap would be the ability to ventilate the heating closet without having to worry about tape giving way and causing the insulation to block the vent holes, and no worries about any moisture getting between a fiberglass blanket with plastic lining and the heater. Course, this does depend on having the room to put the foam in to begin with, a tight closet won't allow any insulation at all. The disadvantage: The water heater will be heating the air between the heater and insulation too.

System2 · May 2008

Re: Water heater blanket

Telco wrote: »

Fire hazard shouldn't be any worse than anything else within a few inches of it.

With 20 some years experience in the fire service here, I can say that almost all foam insulations are extremely easy to ignite and within seconds of ignition, will be burning like gasoline, with the exception that the foam releases huge amounts of lethal chemicals and extremely dense smoke while burning. Far more so than gasoline alone.
If however it's covered on both sides with fire rated sheetrock, the chances of it being accidentally ignited are hugely reduced, plus, air needed for combustion, if it were to occur, would also be greatly restricted.
If you can find a fireproof foam, great, but other than that, keep it covered.
Wayne

Telco · May 2008

Re: Water heater blanket

Wayne from NS Cana wrote: »

With 20 some years experience in the fire service here, I can say that almost all foam insulations are extremely easy to ignite and within seconds of ignition, will be burning like gasoline, with the exception that the foam releases huge amounts of lethal chemicals and extremely dense smoke while burning. Far more so than gasoline alone.
If however it's covered on both sides with fire rated sheetrock, the chances of it being accidentally ignited are hugely reduced, plus, air needed for combustion, if it were to occur, would also be greatly restricted.
If you can find a fireproof foam, great, but other than that, keep it covered.
Wayne

Wow, I was not aware of this. Forums like this are great! Note to self, no exposed foam anywhere, look for alternatives, and mention fire risk when suggesting it. 8)

Water heater blanket

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