block off plate.... durarock???? cement board??
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Still don't understand the reason for a blockoff plate if using a full liner and the chimney cap is sealed. Our installer used fiberglass insulation around that area; he stated that it simply is to keep from loosing heat up the now enclosed chimney. I would understand the need if you were just venting into an open chimney.
You are losing heat to the bricks thru transfer. I fought the notion until I insulated my liner and thought why not just slam some tin with rockwool above it... WOW did it make a difference. Like 20-25 percent or more. I am a believer. Do you need it...I did not think so... Is it better (remember you spent a lot of money to heat with it) of course!
heatit said:
I hope it wasn't fiberglass (pink) - it should be mineral wool insulation - Kaowool?
That's part of my point...metal has no insulating qualities whereas fiberglass, rockwool, etc do and would be a better material to use; unfaced fiberglass will not burn, but will melt, but you may have bigger problems on your hands if the temp gets high enough to do that!
heatit said:
Air will move through fiberglass - I would bet that if you opened a window and put either unfaced rockwool or sheet metal in its place, you would get less heat loss with the metal.
That said, I will be using both....
A piece of sheet metal does the job just as well and is a hell of a lot easier to cut to shape and hold up in the fireplace.
hockeypuck said:
Metal supplier or local metal fabrication shop. Here in Detroit there all over the place.
I used 16 gauge hot rolled steel for mine.
Here are a couple places that Ive used before!
http://www.metalsupermarkets.com
http://www.onlinemetals.com
hockeypuck said:
At a local sheet metal shop, hvac and furnace installer. Ask around, there is bound to be one somewhere nearby. If not, find the nearest big box Lowes or HDepot.
Once you put a sheet metal one in you'll wonder how you ever thought you could do it with anything else. Sheet metal is easy because it bends. A lot of time you've got to bend it around and warp it to get it in place. I've got ceramic blanket insulation stuff on top of my blockoff plate. It's about 1 1/2" thick if I remember right. I didn't run it without it so don't know if it works or not. But I get good heat. It's a really easy job if you've got ANY sort of mechanical skills. Just run to home depot and get a sheet of 28 gauge or so. Go ahead and buy a good set of left hand tin snips (they make a great one that's offset now) and get hand break pliers. You'll spend around $50 and then you'll have the tools to do HVAC duct work or other kids projects.
CarbonNeutral said:
Regular unfaced fiberglass. Trust me, I argued with the installer once I had found that out and he swears by it and has been doing installs for 20 years. There is about 12" of it in there between the liner and the brick. If it was a fire hazard then wouldn't it be foolish to have it in all our homes with electrical wiring running on top/below, etc? That's quite a bit more heat than any fire could produce if it was to short out on it.
one batt of fiberglass 2x6 r15 insy stuffs a fp damper opening to at least 12" thick. works well, but does shrink from exposure to heat.. we still use this method in some applications, but we make sure the area it touches is wrapped with mineral wool chimney liner wrap before stuffing it all in (to prevent said shrinking.)
Thank you Summit. This is the first time anyone has confirmed the use of fiberglass in an install from what I have found on the forum. Yes, it's probably something that will shrink and should be checked. I wish I had gone with the insulated liner to keep the thing nice and warm and help with the draft since our chimney is on the north side of the house.
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