Can I insulate a cold fireplace?


  #1  
Old 11-26-01, 09:36 PM
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Question Can I insulate a cold fireplace?

I have a metal zero clarance fireplace in my house that is a source of cold drafts in the winter when we're not using it. The "chimney" is framed out of 2X4 lumber and covered with wood siding, with the metal flue pipe in the center of it. There is about 12" of clearance between the outside of the fireplace and the wood "chimney". The "chimney" extends from the ground up past the roofline (one story house).

The flue doesn't seem to be the problem as much as the fact that the whole surface of the fireplace is just very cold. The flue damper seems to close fairly tightly, and the fireplace has glass doors that should help to stop air from flowing out the flue.

What are my options for reducing the heat loss through the fireplace? Since it is a zero clearance fireplace, can I place unfaced fiberglass insulation on the outside of the fireplace? Is this safe, or will it cause a fire? It is not practical to try to insulate the inside of the entire chimney.

I have thought about using a piece of styrofoam to cover up the fireplace opening when I'm not using it, but I don't think this will be very attractive. What other options do I have?

Thanks,
David
 
  #2  
Old 12-01-01, 04:33 AM
Insulman
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This is a common problem in many homes with the zero clearance fire places.. The problem starts when the chase is not properly insulated prior to the installation of the fireplace..

I would assume that the chase is supported by your floor joists. These usually protrude out over the foundation and are accessable from the basement or crawl space..

In new construction here is what I would do prior to installing the fire place itself.. Perhaps you can address some of these area's still. Make sure the underside of the floor of the fireplace is well insulated.. foam seal along the entire underside along each side of the floor joists where they meet the subfloor an at the inside perimeter, this will stop air infiltration.. On the inside of the chase foam seal or caulk between all doublers, and at corners and along the bottom of the plate, seal around the vent that exhausts out the side if yours is built that way.

In the wall studs of the chase you can use unfaced R-13 fiberglass
and hold them in place with tiger teeth. You only need to insulate about 8 feet up.

The underside of the chase floor should be insulated with the highest R-value you can fit into the opening.

They do make high temperature insulation products for insulating ovens and such, however I don't think that you could use this type of insulation on a zero clearance fireplace.

It may be possible to still address insulating your chase by removing a section of drywall above the opening.. Usually you can take out about 4 ft up and have enough access to accomplish this work... It isnt easy cause everything is tight and hard to access...but it has been done...

Good Luck

Jim
 
  #3  
Old 12-06-01, 09:33 AM
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The fireplace is on an outside wall, and the chimney chase sits on an extension of the house's foundation, not the floor joists. The cimney chase extends from the ground to the top of the roof (single story house).

You are correct that there is no insulation in the chimney chase. The only thing between my fireplace and the outside world is a thin layer of wood siding (no foam cladding, insulation, etc). I can see into the interior of the chase by removing the fresh air vent for the fireplace, and have confirmed that there is no insulation.

The reason for my question, is that I thouht I could insulate the fireplace itself by removing a small section of the siding from the outside. To insulate the whole chase, I would have to remove a lot more of the siding than I want too. It sounds like that is my only option.

Thanks for the info,

-David
 
  #4  
Old 12-07-01, 11:20 PM
Insulman
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You possibly can insulate the chase only 8 ft high....

Check with the fireplace manufacture and see if you can close off the chase on the interior at 8'.. I have seen many applications where at approx 8 ft a false ceiling is put in around the flue and then insualted from the underside...

remember only unfaced insualtion can be used...

and caulking and foam sealing around all areas where air can penetrate is a huge factor in stopping cold air..


Good Luck

Jim
 
 

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