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The previous owner installed a base-board heater in the bathroom, but did a really poor job. Below the heater, there is a hole in the drywall where the wiring goes into the wall about the size of silver dollar where cold air is blowing into the bathroom. The hole is well concealed (only visible when I get down on my hands and knees), so I'm not worried about it from a cosmetics point of view, I just want to seal it so to stop the draft.

What material(s) should I use that close to a heater?

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up vote 7 down vote accepted

Use a fire retardant expanding foam:

Great stuff fire retardant

Be sure to turn off the electricity to the heater first, then simply spray it in the gap, wait for it to expand and dry, then cut it flush with the wall and paint over it.

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@Niall, Cool, I had no idea such a product existed. Thanks for the link and the pic too. – Robert Gowland Nov 17 '10 at 16:13
Is this stuff rated to be near heaters? – Tester101 Nov 17 '10 at 17:10
@tester101: AFAIK. Will verify later – Niall C. Nov 17 '10 at 17:42
"FireBlock" may not equal heat resistant. The site says it helps to reduce the spread of fire and smoke, which means it slows fire and smoke better than air. – Tester101 Nov 17 '10 at 17:46
@tester101: Interim update: the Wikipedia article on polyurethane says it starts to break down at 240 °C/464 °F. – Niall C. Nov 17 '10 at 20:45

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