Insulating Outdoor Water Heater Closet


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Old 02-08-09, 10:25 PM
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Insulating Outdoor Water Heater Closet

My gas water heater is in a closet accessible from a door on the exterior of the house, as shown in the photo here: IMG_9591 on Flickr - Photo Sharing!

My concern is losing heat from the house, as none of the walls inside the closet are insulated. I'm thinking it would be impractical to try to insulate the those walls, as it would give me less space in an already tight closet, requiring me to downgrade from a 40 gal to a 30 gal water heater (if even the 30 gal would fit).

So would it be worthwhile to insulate the inside of the closet door instead? If so, what materials could I use in order to avoid a fire hazard?
 
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Old 02-09-09, 07:53 AM
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Insulating the inside of the closet door would do nothing. Notice that the door has louvers near the top and bottom for ventilation and combustion air requirements. The louvers, which are required, mean that the interior of the closet will always be at or near the outside temperature.

What you may be able to do is insulate the walls from the house interior side. If you have the room I would use something like rigid polyisocyanurate foam board. Two inch has an R factor of about 14. You do need to cover the foam board with drywall.
 
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Old 02-09-09, 08:21 PM
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Shame on me, I already remodeled the kitchen on the other side of the closet, so I can't get to the closet from the inside.

The drywall visible in the original photo is from the back side of the interior walls. Actually, the inside of the closet walls also have drywall up to the T&P valve, as shown in this photo. So could I spray foam in the gap between the closet drywall and the interior drywall? Then in the rest of the wall from the T&P valve upward, use fiberglass insulation and then cover it with drywall?

On another note, there's drywall on the "roof" of the closet, with insulation above it. If I can insulate the closet walls, it seems silly to even have the drywall and insulation on top, would you agree?
 
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Old 02-11-09, 03:30 PM
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biking_brian,

NO -- I don't agree with you about the drywall and insulation.

Everything that is inside that closet has to be there. It's a firewall and code thing. The WH closet is outside of the envelope of the house and the WH is seen as a source of ignition. Therefore there has to be a firewall between that and the interior walls of the house as well as a firewall above the WH closet.

Furd told you true on insulating the door -- it's a waste of time. But other than the door, everything else has to be insulated because that insulation is there to insulate the house, NOT the WH closet. And everything else inside the closet has to be sheetrocked to prevent the spread of fire in case there's ever a fire inside the closet.
 
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Old 02-11-09, 04:54 PM
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I may not have been clear - my plan is to insulate and drywall the interior walls of the closet, as the WH closet would be considered the outside of the envelope of the house.

My only question is about the top of the closet. Since I have a single story house, the current piece of drywall on the top of the closet is just separating the closet from the attic. But isn't the attic considered outside the envelope of the house, and if so, would there be any purpose to having drywall and insulation on the top of the closet?
 
 

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