Insulation Efficiency

[brickie in oz]

Re: Insulation Efficiency

Ahh... I see, it involves drilling a continuous series of holes in the masonry and filling them with a silicone fluid,

No, it involves putting a barrier in place as you lay the blocks.
Like this.

[vtsteve]

Re: Insulation Efficiency

Ahh... I see, it involves drilling a continuous series of holes in the masonry and filling them with a silicone fluid, which permeates the masonry and forms a water barrier. It seems to be a UK/Oz technique.

[brickie in oz]

Re: Insulation Efficiency

It sounds like a *good thing* for those of us in wetter climates. .

Not only for the wetter climates but for anywhere, even dry climates need a dampcourse, DPC.
Damp or moisture will climb and masonry structure so an impervious barrier need to be incorporated in to the masonry.

The rule of thumb is taken that rain will hit a hard surface and bounce about 100mm high, so the DPC needs to be set more than 100mm from the hard surface to stop moisture penetration up into the structure.

If the DPC is set too low it will be ineffective.

[vtsteve]

Re: Insulation Efficiency

Any dampcourse should be well above ground level to stop this from happening..

I don't see any mentions of "dampcourse" here within the past year or two. It sounds like a *good thing* for those of us in wetter climates. Would you care to elaborate for us amateur masons? Maybe it merits a mention in the 3.0 plans... My slab rests on three feet of 3/4" stone, but my base still gets damp when the snow melts (not my dome, though).

[brickie in oz]

Re: Insulation Efficiency

at least like this

The way you have it there is no adhesion between the blocks and the concrete due to the rubber matting, plus when it rains the water will sit on the rubber matting and travel up the blockwork into the oven.
I can see in the pic that moisture is already travelling up the blockwork.

Any dampcourse should be well above ground level to stop this from happening..

[Johnny the oven man]

Re: Insulation Efficiency

I was going to use a locally-sourced 1" cal-sil board to spread the load, on top of 3" Foamglas for both more insulation and to prevent water wicking up from the base. The Foamglas is an absolute barrier to ground water, but it's really friable, even though it's rated for 90 psi. compressive load. Without the cal-sil, I think a brick dropped during construction would go halfway through to the hearth slab! I ended up with 3" cal-sil and 3" Foamglas (gross overkill, but I *really* wanted the Foamglas underneath).

A lot of people worry about water and cal.Sil. I know that you can soak cal.Sil in a bucket for a week and it still wont degrade, just drys out and is as rigid as ever.

[alex.g]

Re: Insulation Efficiency

at least like this

[brickie in oz]

Re: Insulation Efficiency

to prevent water wicking up from the base.

Thats an issue that you should address before you continue with your build.
You dont want water near the oven.

[vtsteve]

Re: Insulation Efficiency

I was going to use a locally-sourced 1" cal-sil board to spread the load, on top of 3" Foamglas for both more insulation and to prevent water wicking up from the base. The Foamglas is an absolute barrier to ground water, but it's really friable, even though it's rated for 90 psi. compressive load. Without the cal-sil, I think a brick dropped during construction would go halfway through to the hearth slab! I ended up with 3" cal-sil and 3" Foamglas (gross overkill, but I *really* wanted the Foamglas underneath).

[alex.g]

Re: Insulation Efficiency

Guys what is this? R=m2.K/W Resistance(s) to heat flow ?
But main question.. do you know what numbers should be for good hearth insulation?

I'm building this - http://www.fornobravo.com/forum/f8/4...guy-16753.html
and using alternative materials.

Thanks

[Ken524]

Re: Insulation Efficiency

You should be fine with CalSil. The stuff I used was a different animal (I wish I had used CalSil ).

[Gulf]

Re: Insulation Efficiency

You will have one of the best insulated oven floors on the forum! Your plan is as close to perfect as you get. The CalSil board is about the best insulator you can get for directly under the floor bricks. You won't regret it.

WOW!, thanks very much for the vote of confidence.

I went back and read your thread again. I will definately take every precaution to keep the CalSil as dry as possible.

[Ken524]

Re: Insulation Efficiency

Installing under fire brick for sure. I have seen references to FB board, ceramic fiber board, etc. I just wasn't sure if calcium silicate was appropriate for insulating the floor. I'm glad to find out that it is. I'll proceed and install it on top of the vermicrete.

You will have one of the best insulated oven floors on the forum! Your plan is as close to perfect as you get. The CalSil board is about the best insulator you can get for directly under the floor bricks. You won't regret it.

[Gulf]

Re: Insulation Efficiency

Installing under fire brick for sure. I have seen references to FB board, ceramic fiber board, etc. I just wasn't sure if calcium silicate was appropriate for insulating the floor. I'm glad to find out that it is. I'll proceed and install it on top of the vermicrete.

Thanks tinaloven and david s

[david s]

Re: Insulation Efficiency

I have poured a 4" (5 to1 ) vemiculite and portland insulation layer on my hearth. Since then, I have been given enough 2" calcium silicate board to cover the oven floor area. Is this material (which seems to be every bit as substantial as the vermicrete and has a rating of 1280 degrees) suitable for the floor of a WFO?

No, it is not suitable for the floor of a WFO, but it is suitable to use under the floor. If you got it free why not place a 2" layer of it over the vermicrete then use your firebricks over the top. Then you will have an extremely well insulated floor. 2" of Cal. Sil. Board is approx. twice as good an insulator as the 4" 5:1 vermicrete. But you will end up with the floor 2" higher than you had planned.