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I just installed a heater in the ceiling of my bathroom and am trying to decide how to insulate around it. The insulation in my attic is the fluffy, blown insulation (cellulose maybe? not exactly sure what it's called).

It seems like it might be a fire hazard to put it right up against the heater. If it is, how far away does it need to be away? Do I need to get some fiberglass to use here?

  • Since the manual says nothing, I would CALL the manufacturer and verify insulation is not an issue. Not worth the risk to not be certain. – topshot Sep 26 '16 at 13:10
  • What is the heater make and model? – wallyk Nov 27 '16 at 17:38
  • @wallyk It's a Nutone 665RP. Here's a copy of the manual -- All I found was "follow fire codes" and "don't block the vents". – Gary Dec 17 '16 at 23:08
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The manual and device specifications—oddly—do not use any of the words which mean the appliance is zero clearance. Though it is meant to be installed through sheetrock or other fire dampening materials. It is an odd situation.

There have been several fires reported caused by the Nutone 559R:

Presumably, thousands and thousands of these units are in use daily, so the few incidents reported actually seem to indicate a really good safety record. Note that one of the six reports was from a modified unit which bypassed the thermal protection.

Given the possibilities, I would—if reasonably simple:

  • Install with metallic brackets so that no wood touches the box.
  • Keep all flammables away from the box exterior.
  • Don't worry about insulating around it.
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In this case, i would read the manual carefully; usually the housing provides a buffer for heat dissipation, but some heaters may specify no flammable materials within x inches, or nothing on top. And make sure the air intake is unobstructed or the heater may pull insulation fragments in to the housing.

  • It does mention specifically about the air intake, but it says absolutely nothing about insulating. Maybe that implies that I don't need to worry about it? – Gary Sep 25 '16 at 23:31
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    with no guidance from the manufacturer, I would not worry, but if it were me, I wouldn't put anything on top since it would tend to trap heat. – SqlACID Sep 25 '16 at 23:36
  • But that could either way, right? Minimizing heat loss into the attic would put more heat out the bottom. – Gary Sep 25 '16 at 23:53
  • If it's unheated space above I could see that. – SqlACID Sep 26 '16 at 0:30

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