ROXUL insulation OK to use?

[VJ Dickens]

We were planning on using vermiculite/portland mix for insulation over dome. It was advised to me to put down one or more layers of foil on top of fire brick so the insulation concrete does no form a bond allowing the dome to expand and contract and not allowing the insulation layer and/or the hard outside layer to crack. Does this sound right? Also, I found a local dealer who has a product call Roxul RHT 80. The specs sound as if it would be a good alternative to a ceramic blanket. Has anyone used this or have any input to pros or cons about it?

[boerwarrior]

Re: ROXUL insulation OK to use?

I see your post has gone unanswered for a day so I will weigh in - but many others have more experience so hopefully you will get some more responses!

The question of using foil as a barrier has come up several times in this forum. The general consensus is "no", it is not good to use foil. The main reason is that foil is a moisture barrier - which is good for preventing outside moisture from getting in, but bad for letting inside moisture get out.

If you use foil between the firebrick and the insulation it is going to be very hard for you to properly dry out your oven. You mentioned ceramic fiber insulation or equivalent. (Sorry, I can't comment on "Roxul"). If you use ceramic fiber blanket followed by a hard concrete layer you should be fine.

One final thing... you will almost certainly get some cracks! One joke goes: there are two kinds of people in this forums, those who have cracks and those who lie about having cracks! Cracks are not terrible unless they are really big. Good luck!

[stonecutter]

Re: ROXUL insulation OK to use?

We were planning on using vermiculite/portland mix for insulation over dome. It was advised to me to put down one or more layers of foil on top of fire brick so the insulation concrete does no form a bond allowing the dome to expand and contract and not allowing the insulation layer and/or the hard outside layer to crack. Does this sound right? Also, I found a local dealer who has a product call Roxul RHT 80. The specs sound as if it would be a good alternative to a ceramic blanket. Has anyone used this or have any input to pros or cons about it?

I missed this...funny we were just discussing this on my thread.

Roxul is mineral wool...it's what I have used on all my builds (in tandem with loose vermiculite or perlite) except one. I don't use board insulation under the floor ( perl/vermcrete) but I use the batt insulation around the dome, then cover that with loose fill.

I pulled the spec pdf because I was unfamiliar with RHT80...looks like that is board insulation...not what you want for the dome. Get some batt insulation, and Roxul has that too.

Forget the foil. No layers will bond to the brick after a couple heat cycles, and as mentioned, it traps moisture in.

[stonecutter]

Re: ROXUL insulation OK to use?

Roxul Safe N Sound

[SCChris]

Re: ROXUL insulation OK to use?

VJ, I used stonewool rather than ceramic fiber blanket without issue other than to mention that "tailoring" the fit of the stonewool boards, Roxul, appears to be tougher than the blanket.. The material that I used was 3.5 inches thick and does wrap but did required a bit of ripping, to make the curves, and stuffing, to fill the gaps. I have a house around the dome and used attic fiberglass to fill the corners and filled the remaining space with vermiculite. Below the dome and floor I used 2 inch rigid insulation and created a small heat break between the cooking floor and the entry to great benefit..

http://www.fornobravo.com/forum/f8/s...uild-7035.html

If you have access to the bat material, use it! And I would also say that I had hoped to find the loose, blow-in, fill material to fill the house structure and this would have avoided the tailored wrapping of the dome completely.. I'm very happy with the end results.


Chris

[VJ Dickens]

Re: ROXUL insulation OK to use?

Thank you everyone for your responses. One thing I should mention is that our oven is a small barrel vault shape. I can use the more stiff boards for the sides and if I go ahead and use it for the dome I was planning on scoring about ever four inches or so to help make the bend. Then wire mesh and stucco over that. Or should I put a few inches of insulating concrete as well? The dealer has 2 and 3 inches to choose from. I used 5-1 vermiculite/Portland 4 inches on the bottom will that be okay?

[stonecutter]

Re: ROXUL insulation OK to use?

You want more than a couple inches of insulation. Double up on the board or add 4" of vcrete at least.

5:1 is ok for the floor, especially if you have med-high duty bricks.

[VJ Dickens]

Re: ROXUL insulation OK to use?

Stonecutter, Thank you. Where in SC. are you? We are in Easley(Greenville-Clemson area).

[stonecutter]

Re: ROXUL insulation OK to use?

We are in Summerton, on Lake Marion. I'll be in Greenville sometime next month...we considered moving up there this past spring, it is still a possibility.

[VJ Dickens]

Re: ROXUL insulation OK to use?

Thanks for all of your help. Greenville is nice and growing with plenty of opportunities. However, close to the lake would be nice. I will post so pics when we get a littler further along.