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BlueBSH 12-06-2010 07:34 PM

Insulating around fireplace flue
 
2 Attachment(s)
Well, I have a open hole around the flue where it goes from the 1st floor up to the roof and cold air is just rushing down into the living room and master bedroom on which share the wall that the flue pipe goes down into, the area the flue goes into is a hallow void that is about 1.5" deep, and 12 ft wide that runs up to the attic and unforinuatly isnt sealed up around it up there... how would you go about weatherizing this? Pics attached where you can see the empty space and the pipe going through it... dispide what looks like paper touching it, its about 9 inches from it, its just the angle the picture was taken at.

Hixheat1 12-06-2010 08:00 PM

Quote:

Originally Posted by BlueBSH
Well, I have a open hole around the flue where it goes from the 1st floor up to the roof and cold air is just rushing down into the living room and master bedroom on which share the wall that the flue pipe goes down into, the area the flue goes into is a hallow void that is about 1.5" deep, and 12 ft wide that runs up to the attic and unforinuatly isnt sealed up around it up there... how would you go about weatherizing this? Pics attached where you can see the empty space and the pipe going through it... dispide what looks like paper touching it, its about 9 inches from it, its just the angle the picture was taken at.

It needs to be fire stopped code requires a 1 inch clearance from combustibles so use sheet metal and high temp caulking around flue cap rest of area with insulation too prevent drafting

BlueBSH 12-06-2010 08:03 PM

Quote:

Originally Posted by Hixheat1 (Post 547021)
It needs to be fire stopped code requires a 1 inch clearance from combustibles so use sheet metal and high temp caulking around flue cap rest of area with insulation too prevent drafting


well I know if needs a firespot around it at the joist level, I assume sheet metal with the firestop caul around all the openings that are left, but what do you mean by cap the rest of the area with insulation? how would I prevent the insulation from touching the flue pipe? thanks

Hixheat1 12-06-2010 08:07 PM

Quote:

Originally Posted by BlueBSH

well I know if needs a firespot around it at the joist level, I assume sheet metal with the firestop caul around all the openings that are left, but what do you mean by cap the rest of the area with insulation? how would I prevent the insulation from touching the flue pipe? thanks

I'm going by Picts once you fire stop with metal and caulk that should prevent drafting u need too keep a one inch clearance from flue.

Hixheat1 12-06-2010 08:16 PM

Quote:

Originally Posted by Hixheat1

I'm going by Picts once you fire stop with metal and caulk that should prevent drafting u need too keep a one inch clearance from flue.

On the vert walls u need to have a vapor barrier we use a foil type barrier or in our industry we sometimes use our r8 insulation or bubble wrap It works well. Along with the insulation that is there. Without the barrier there is no r value and that is why it is cold around the fire place

Hohn 12-06-2010 08:32 PM

Why not something like a Roxul stone wool? It won't burn and is pretty dense to help reduce draftiness..

BlueBSH 12-06-2010 08:39 PM

Quote:

Originally Posted by Hohn (Post 547051)
Why not something like a Roxul stone wool? It won't burn and is pretty dense to help reduce draftiness..

no one carries rock wool around here on the shelf, not sure if I can special order a small amount from anyone, will have to check into that...


I do have a roll of that refletex bubble wrap insulation, but is that really the best thing to put an inch form a flue? should I do a sheet metal cover over the joist first to put something to prevent stuff from moving into the flue somehow on accident?

Hixheat1 12-06-2010 08:42 PM

Quote:

Originally Posted by Hohn
Why not something like a Roxul stone wool? It won't burn and is pretty dense to help reduce draftiness..

Once you fire stop the drafting will stop k wool will help insulate around the flue. The vert walls still need a vapor barrier.

Termite 12-06-2010 09:34 PM

You CANNOT insulate up against that flue. No matter what type of insulation. All chimneys require at least 1" clearance, some require 2" or more. A sheet metal pan/collar around the pipe will seal up the draft when properly sealed with the aforementioned caulking. A sheet metal insulation shield....A cylinder of metal around the pipe sitting on top of the metal pan you need....Will keep any added insulation from contacting the flue and will maintain the necessary air space.

SteelToes 12-07-2010 08:33 AM

Quote:

Originally Posted by thekctermite (Post 547086)
You CANNOT insulate up against that flue. No matter what type of insulation. All chimneys require at least 1" clearance, some require 2" or more. A sheet metal pan/collar around the pipe will seal up the draft when properly sealed with the aforementioned caulking. A sheet metal insulation shield....A cylinder of metal around the pipe sitting on top of the metal pan you need....Will keep any added insulation from contacting the flue and will maintain the necessary air space.

Correct. Here in Chicago you need to have 1"-2" "cold air clearance" (depends on location); also looking at the picture it is hard to tell if this is a single or b-vent but in any case just like thekctermite said no insulation around the flue pipe only fire stop thimble at the floor perimeter.

BlueBSH 12-07-2010 11:33 AM

Quote:

Originally Posted by SteelToes (Post 547254)
Correct. Here in Chicago you need to have 1"-2" "cold air clearance" (depends on location); also looking at the picture it is hard to tell if this is a single or b-vent but in any case just like thekctermite said no insulation around the flue pipe only fire stop thimble at the floor perimeter.

how can you tell if its a B or L vent? I know one here requires 1 inch and the other about 3 inch clearance, not sure how you tell the difference.. Does the fireplace or manual specify what it should be or someway to tell from the cap on the flue or anything?

The fireplace is a Heatilator NA32

Edit: just saw on the tag on the fireplace 2 in min clearance chimney 1/2" firebox... guess that answeres my question, I guess its an L vent?

BlueBSH 12-07-2010 11:50 AM

or is it an L vent?
Quote:

Framing dimensions of enclosures and at joist or rafter levels shall be a minimum of 6" larger than the outside of the vent for L-Vent and 2” larger for B-Vent.
because the framing around it is not 6" on all sides, its more like 3" inches on 2 of the sides

operagost 12-07-2010 12:23 PM

I'm interested in this topic because I have a similar situation in my attic. My flue appears to be double-walled, as I have a mid-efficiency boiler yet the outside of the pipe is just warm to the touch when the boiler is running. I don't know whether this means I also need to add a collar or if I can just box it in with foam board while keeping a few inches of clearance. It's already boxed in where it passes through the second floor bathroom below, but I wouldn't want to add to a possible existing mistake.

SteelToes 12-07-2010 12:45 PM

Quote:

Originally Posted by BlueBSH (Post 547367)
or is it an L vent?


because the framing around it is not 6" on all sides, its more like 3" inches on 2 of the sides

Type A b vent is intended for a low-heat applications
B vents are not for use with fireplaces and oil-fired equipment
Type L-Vent is designed for venting approved oil or gas appliances producing draft hood flue gases not exceeding a temperature of 570F (299C).
Type B Gas vent is designed for venting approved gas appliances equipped with draft hoods and other Listed gas appliances specified for use with Type B Gas vent which produce flue gases not exceeding 480F (249C).
Minimum clearance between the vent and combustible materials is 3 inches for L-Vent and 1 inch for Type B gas vent. L-Vent or B-Vent that extends through any story above that on which the connected appliance is located is to be provided with enclosures having a fire resistance rating equal to or greater than that of the floor or roof assemblies through which they pass.
Framing dimensions of enclosures and at joist or rafter levels shall be a minimum of 6" larger than the outside of the vent for L-Vent and 2 larger for B-Vent.
Near the vent base, post a notice of the type of appliance for which the DFS installation to combustibles is installed. If installed at 1 airspace, it is limited to B-Vent (gas) only. If it is installed at 3 airspace, it it may be used with oil (as an LVent) or gas (as a B-Vent).

for more info refer to this website :

http://www.inspectapedia.com/chimney...t_Chimneys.htm

kwerk 12-07-2010 02:21 PM

There should be a sheild that goes there and keeps the insulation away from the chimney. I would call the manufacturer and ask them about it, they may be able to send you the piece. There should also be a fireblock at each ceiling.

Scroll down to page 11 on here for an example:

http://www.heatilator.com/downloads/...s/480-1091.pdf


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