floor insulation

[mozo]

ey up,

I have been researching my build for a while now. I see that some people use fireboards as insulation for the floor, however some choose to build a vermiculite layer into the hearth.

Could someone please explain to me the pros and cons of each, and which one makes better financial sense.

appreciate any response,


BW

Mozo

[edinburghman]

Been thinking the same thing, what strikes me is that board seems very pricey, a consequence of the cost of driving something so bulky but light around the country (and it's cost of manufacture too) whereas vermiculite is relatively inexpensive but more time-consuming and labour intensive to mix.

[cobblerdave]

G'day
As a rough rule of thumb 50 mm of either ceramic board under the hearth and 50 mm of ceramic blanket over the dome is the standard . It never hurts to exceed this.
To obtain the same level of insulation with either pearlite/ cement or vermiculite / cement you'll require 100 mm double the thickness.
You got to remember that 1/3 of the volume of the mix is water trapped in the tiny pours. You have to wait to allow it dry naturally in good conditions a week an inch, so up to 4 weeks uncovered.
So what you save in money you lose in time.
Sodium silicate board and pearlite silicate board is also available. It most be protected from any moisture however as the silicate is water soluble.
Aerated cement block is used sometimes as base insulation . My own oven has this as the hearth insulation and has operated without any problems for. 4 yrs now . But there are questions weather its heat proof enough in the long term, I always encourage anyone using it to protect it with at least a 25 mm layer of say pearlite cement just in case.
Hope something here helps
Regards Dave

[edinburghman]

Aug 13, 2014 9:42:34 GMT cobblerdave said:

G'day
As a rough rule of thumb 50 mm of either ceramic board under the hearth and 50 mm of ceramic blanket over the dome is the standard . It never hurts to exceed this.
To obtain the same level of insulation with either pearlite/ cement or vermiculite / cement you'll require 100 mm double the thickness.
You got to remember that 1/3 of the volume of the mix is water trapped in the tiny pours. You have to wait to allow it dry naturally in good conditions a week an inch, so up to 4 weeks uncovered.
So what you save in money you lose in time.
Sodium silicate board and pearlite silicate board is also available. It most be protected from any moisture however as the silicate is water soluble.
Aerated cement block is used sometimes as base insulation . My own oven has this as the hearth insulation and has operated without any problems for. 4 yrs now . But there are questions weather its heat proof enough in the long term, I always encourage anyone using it to protect it with at least a 25 mm layer of say pearlite cement just in case.
Hope something here helps
Regards Dave

Thanks Dave

Yes, very informative.  You're right it's a balance of time v money... as ever.

[wolvisfamily]

We've got the ceramic fibre board cut, and as far as I can tell it just sits there without needing any adhesive or mortar, or indeed protection. It's just so fibrous and easily damaged, I wonder that there isn't something I can coat it with to stabilise it?

[james9]

Jul 20, 2017 16:32:04 GMT wolvisfamily said:

We've got the ceramic fibre board cut, and as far as I can tell it just sits there without needing any adhesive or mortar, or indeed protection. It's just so fibrous and easily damaged, I wonder that there isn't something I can coat it with to stabilise it?

The general recommendation is to wrap entirely in high grade silver foil to keep moisture out because trapped water will reduce the efficiency of your insulation. Also mortar will instantly sink into the uncovered board so it won't stick. It also depends if the build is undercover or exposed and how long you intend to take. Some people have their boards exposed to the weather for months. 

The oxford build has some good photos on this subject.

ukwoodfiredovenforum.proboards.com/thread/2148/oxford-build