How much ceramic fibre blanket

[Rinrat86]

Hi,
We have started our build... Okay the cement pad has been poured. I am trying to get the planning and aquisition ahead of DH's desire to build.

We are planning a dome with inner diameter of 36". The FB instructions say I need 150 square feet of 1" blanket to cver the dome with 3". This doesnt match with my calculations... 36" inner dimension comes out to 45" on the exterior. Area of a sphere is 4(pi)r squared, so full sphere comes out to 44.2 sq ft, dome should then be about 22. So then why does fb suggest 3 layers of 50 sq ft.

Man resurrecting my math skills is painful!

Rose

[david s]

Re: How much ceramic fibre blanket

You need considerably more because your area of dome would be for the first layer. The second and third layers will use more because the dome is then bigger. You also need to add the area of the dome on the exterior, below the floor level which also needs to be insulated. (your calculation is based on a hemisphere). Also there is considerably more required because you have to cut the blanket to get it to conform to the compound curve. This creates lots of wastage. You can use the cut off bits to fit in gaps here and there.

My calculations (with around 30% wastage) tell me you'll need 100sq ft. For 3 layers.
If you do a cladding layer it will increase your exterior diameter too.

[DavidApp]

Re: How much ceramic fibre blanket

Hello Rose

I used 2 boxes of blanket. 1" x 24" x 25'. I did 3 layers of blanket on a 36" oven

David