Roxul ComfortBoard IS in place of FB Board

[frenchy_forno]

Hello all!

First time poster, long time lurker! I started my oven build a few months ago sourcing materials locally. One of the items that I wanted to have shipped to Manitoba from the FB Store is the FB Board and FB Blanket. Shipping is $350

So, I'm looking for alternatives. I found this stuff called Roxul ComfortBoard IS that I'm thinking I may use to insulate between my firebrick floor and the hearth. Any thoughts on if this would be suitable or not? I don't want to leave this space uninsulated as I've read much about heat loss in the concrete but I also can't bear spending over $600 on getting this stuff shipped here.

Here are some links:
http://www.roxul.com/files/RX-NA_EN/...Board%20IS.pdf

Roxul | Roxul R6 ComfortBoard IS Insulated Sheathing Board for Basement and Exterior Wall Applications | Home Depot Canada

[frenchy_forno]

Re: Roxul ComfortBoard IS in place of FB Board

Well I bought a bale of this stuff. It's R6 value and it's basically like a compressed insulation bat. It is very rigid and I cut it with a serrated bread knife. Worked awesome. My plan is to use only one layer under my fire brick floor. I'm semi-concerned about the possibility of a smell from it, so I think I might do a skim coat of fire clay mortar to seal it somewhat and then lay my floor on top of that. Anyone see any issues with that? My blog link is in my signature and has pics of the insulation etc.

[Rotterdam]

Re: Roxul ComfortBoard IS in place of FB Board

Post a pic please...

How thick will you insulation be between the hearth and the concrete slab?

[frenchy_forno]

Re: Roxul ComfortBoard IS in place of FB Board

Isn't the slab the hearth? Here's a pic. The plan was to have the insulation board (3") between the fire brick floor and the hearth. This is one layer which is 1.5" thick.

[Rotterdam]

Re: Roxul ComfortBoard IS in place of FB Board

Thanks for the pic. I'm not familiar with that product at all, if it will hold the weight of the brick over time and your comfortable with the r rating then go for it. The vermicrete is always a reasonable priced alternating. You might stack 5 bricks on it to see if there is any compression. I hope it works great!
Rotterdam

[frenchy_forno]

Re: Roxul ComfortBoard IS in place of FB Board

I'm actually going to build the soldier course around the floor rather than on the edge, so weight on the floor will only ever be the weight of the floor itself and then wood, dishes and delicious pizza!

Thanks for the advice Rotterdam!

[boerwarrior]

Re: Roxul ComfortBoard IS in place of FB Board

it is Ok to build the soldier course around (outside) the floor, but it does need insulation under it - otherwise you will lose a lot of heat through the walls and down into the hearth. You should think of your entire dome as 'floating' within a cocoon of insulation.

[frenchy_forno]

Re: Roxul ComfortBoard IS in place of FB Board

Wow i never thought of that at all.... I think I have enough of that Roxul board left to make sure it's insulated under the soldier course. Thanks boerwarrior. Much appreciated.

[frenchy_forno]

Re: Roxul ComfortBoard IS in place of FB Board

Just in case anyone is wondering... My oven is cured and in use. The Roxul ComfortBoard is working great! I've had the floor at 680F and have had little heat loss. I also used Roxul ComfortBatt for the dome insulation. I had the dome at 1022F and I checked the top of the dome on the outside on the insulation and it was 106F. This is without the stucco finish. I think I can safely call that a success.

[NCMan]

Re: Roxul ComfortBoard IS in place of FB Board

Just in case anyone is wondering... My oven is cured and in use. The Roxul ComfortBoard is working great! I've had the floor at 680F and have had little heat loss. I also used Roxul ComfortBatt for the dome insulation. I had the dome at 1022F and I checked the top of the dome on the outside on the insulation and it was 106F. This is without the stucco finish. I think I can safely call that a success.

I didn't use the board, but did use 8" of the batt version over my dome, then finished filling the rest of the wall cavity w/loose perlite. I haven't done any testing yet, as I am still building, but do expect good results.

[thebigt]

Re: Roxul ComfortBoard IS in place of FB Board

Just in case anyone is wondering... My oven is cured and in use. The Roxul ComfortBoard is working great! I've had the floor at 680F and have had little heat loss. I also used Roxul ComfortBatt for the dome insulation. I had the dome at 1022F and I checked the top of the dome on the outside on the insulation and it was 106F. This is without the stucco finish. I think I can safely call that a success.

Wish I'd have known this would work. Roxul products much easier to locate and cheaper than the INSBlok19 that I used. I used 2" CFB on the outside of the dome and next year will use some roxul before I stucco.