Replies

1. 
   BigBill | Nov 09, 2009 06:40am | #1

   No foam.  Use grout.

2. 
   mikeroop | Nov 09, 2009 03:12pm | #2

   they make a fireproof foam so i don't see why not. it's red and the can clearly states fireproof. our local hardware sells it.

1. 
   BigBill | Nov 09, 2009 04:43pm | #4

   What is the brand name of the 'fireproof' foam?

1. 
   wjq | Nov 10, 2009 03:22am | #5

   I wrote to Simpson and they say:
   "As long as the wall thimble seals off the outer wall to be weather proof then you are done. If the gaps do not allow the wall thimble to seal to the wall then rebuild the wall so it will. We do not want insulation around our wall thimble."That's not too helpful since I have cedar shingle siding so it isn't going to be easy to make the wall flush.I checked out the "fireblock" foam, which is from the same company as the rest of the expanding foams, and it doesn't have a higher temperature rating than the standard foam.I think I'll put some more fiberglass around the thimble and try to seal the outside with silicone.Thanks for all the tips.Bill

1. 
   dovetail97128 | Nov 10, 2009 03:34am | #6

   Might try wrapping the thimble with stove door gasketing material and then using a flexible refractory material to pack any small voids.
   Life is Good

2. 
   klhoush | Nov 10, 2009 07:29am | #10

   Cut in a square piece of 3/4" redwood or cedar with a Z flashing on top. Really not a big job.

   OB

3. 
   [email protected] | Feb 09, 2011 11:16am | #23

   Pull off some shingles

   Not sure I see the problem.  You just do it like a roof with an infinite pitch. 

   Remove some shingles from around the hole. 

   Cut a tight clearance hole in a piece of flat cedar that is long enough to bridge the studs. Chamfer the long grain edges, to make a drain slope on the top, and a drip edge on the bottom, these go in the long grain, the end grain goes to the sides.  Put some of whatever you seal your shingles with on it, double coating the end grain.

   Install the new flat cedar peice, flashing it in just like a roof flashing. 

   Screw the flange from the vent to the flat piece. 

   Replace/repair the shingles just like it was a roof. 

2. 
   mikeroop | Nov 10, 2009 04:20am | #7

   http://www.albanycountyfasteners.com/SearchResults.asp?Cat=240 

   this is just one name brand of many.

   it's pricey stuff!

3. 
   1hotwire | Nov 09, 2009 04:39pm | #3

   How about using high temp silicone?

4. 
   renosteinke | Nov 10, 2009 05:18am | #8

   No way. Not even the red stuff, or silicone.

   Instead, they sell specific fireplace gasket material and sealers. Use those.

5. 
   mikeroop | Nov 10, 2009 05:47am | #9

   rock wool insulation will work too. I own a wood stove and fireplace store as well as I'm a contractor so you do have options if you wish but as someone stated earlier we usually don't put anything between the thimble.

6. 
   Piffin | Nov 10, 2009 02:14pm | #11

   Is this a co-axial flue?

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

7. 
   gusfhb | Nov 27, 2009 04:33pm | #12

   I used a bunch of that red foam and got curios, took a match to it. It burned pretty good. Funny I thought. put a match to the regular stuff and it self extuinguished, same with blue foam.

   I won't be buying any red foam.

   You could consider firestop caulking.

1. 
   DanH | Nov 27, 2009 04:55pm | #13

   Did you try it after it had cured?
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

8. 
   gusfhb | Nov 30, 2009 04:11pm | #14

   absolutely

1. 
   Snort | Nov 30, 2009 04:34pm | #15

   A fireplace store should have fireproof rope.http://www.tvwsolar.com

   We'll have a kid

   Or maybe we'll rent one

   He's got to be straight

   We don't want a bent one

   He'll drink his baby brew

   From a big brass cup

   Someday he may be president

   If things loosen up

9. 
   rdesigns | Nov 30, 2009 06:24pm | #16

   I wonder if Simpson understood your application.

   If I understand your Q, it seems that you have a thimble that provides the needed clearance from combustibles around the flue--2 inches. And that you want to fill and seal around the outside of the thimble, not between it and the flue--right?

   If so, then it seems that any combustible material would be ok on the OUTSIDE of the thimble, so long as the 2" clearance is maintained between the inside of the thimble and the flue.

1. 
   Larrymenkes | Feb 07, 2011 11:53pm | #17

   Foam Insulation for thimbles

   I'm working on this issue because as a nationally certified Sustainable Building Advisor, insulating all aspects of buildings is essential to the energy efficiency of buildings and my work. I don't wish to argue that point because I'm using net-zero standards that leave little if any room for compromise regarding insulation and air leak sealing. A good foam should do both.

   I have a Harmon PC-45 with an outside air kit. I intend to fully foam the air spaces in the thimble, both in the chamber between the flue pipe and the thimble, and around the outer perimeter where there should be fiberglass batting. I wasn't carefully watching the installation so I'm flying blind a bit with what's inside. I'll be doing a more comprehensive IR inspection in the next month and will find out how good it is at that time.

   I'm intending to use Touch 'n Foam Fire Break, an ASTM E-84/E-814, UL1715/94 V-O rated Flame Resistant Sealant. It has other ratings but is cetified to 200˚F. It is a high expansion foam (1:3). Although there are some contradictory instructions on the packaging I think they're there for liability reasons. It comes in 12oz. cans for about $8.50 a can retail.

   My IR temp measurements for exterior flue-pipe temperatures at the exhaust flange doesn't exceed 127˚F and 106˚F at the thimble. I think the 200˚F rating has some safety factor, but I'll be doubling that factor in my use, according to my readings. The temp I measured outside the wall are significantly lower, but, baby, it's been cold outside around here.

   I also plan to do some  heating room thermal insulation/air leak sealing in another building using Tiger Foam which only makes E-84 cetified foam products.

   I'll let you know how it all works out. Would like to hear from anyone with experience in doing this.

    

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1. 
   davidmeiland | Feb 08, 2011 03:12pm | #18

   IR temps

   My IR temp measurements for exterior flue-pipe temperatures at the exhaust flange doesn't exceed 127˚F and 106˚F at the thimble.

   I'm assuming you understand emissivity and that you took the temperature measurements under worst-case conditions (i.e. the stove was over-fired for an extended period), and then double-checked the temperatures with a thermocouple. What brand and type of pipe are you measuring?

   As a building contractor I only put materials like vent systems together in exact accordance with the manufacturer's instructions. If they say you can put that type of foam insulation around their wall thimble, go ahead and do it. If they say no, I don't do it, and they almost always say no to questions like that.

   I don't know what the parts you're using look like, but I doubt that you can gain much insulation value by foaming the thimble. I would worry about that last, after you have done your blower door testing and dealt with every other air leakage site.

1. 
   MarkH | Feb 08, 2011 06:29pm | #19

   You have got that right.  A shiny SS steel part will not read correctly on most if not all IR thermometers.  I would not foam flue pipes at all.  Maybe something else would be ok.

   For everybody else, here is a little info from omega.com about emissivity.

   What is emissivity, and how is it related to infrared temperature measurements?

   Emissivity is defined as the ratio of the energy radiated by an object at a given temperature to the energy emitted by a perfect radiator, or blackbody, at the same temperature. The emissivity of a blackbody is 1.0. All values of emissivity fall between 0.0 and 1.0. Most infrared thermometers have the ability to compensate for different emissivity values, for different materials. In general, the higher the emissivity of an object, the easier it is to obtain an accurate temperature measurement using infrared. Objects with very low emissivities (below 0.2) can be difficult applications. Some polished, shiny metallic surfaces, such as aluminum, are so reflective in the infrared that accurate temperature measurements are not always possible.

1. 
   davidmeiland | Feb 08, 2011 07:30pm | #20

   Here's an image

   of a piece of Metalbestos Ultra-Temp stainless steel flue pipe where it penetrates a cathedral ceiling/roof. The hot rectangle is a piece of Scotch #33 electrician's tape stuck to the pipe. E = about .95 on that, which is what the imager was set to. The stainless itself appears to be about 40 degrees cooler, but it's not.

   
2. 
   MarkH | Feb 08, 2011 08:54pm | #21

   I've had to prove several times to the calibration lab at my employer that my controls are accurate, wheras their reading on an IR thermometer are wrong.  Not a nice situation, but the non contact thermometers are not trustworthy in all situations.

3. 
   davidmeiland | Feb 08, 2011 09:58pm | #22

   Those

   IR thermometers are flying off the shelves like hotcakes. The folks that do training for Fluke told me that they have a 2-hour course that teaches folks how to use them.