CEMENT BOARD HARDIE BACKER AS A HEAT SHIELD

I was thinking on useing tile backer board around my coal stoker on the cealing and coal bin wall studs as a heat shield. The company said the hardie backer board is paintable and will not catch fire, but would not block it. I would want it to block some heat.I figure it would be better than nothing. What if I insulate with duct board under the cement board. ANY IDEAS, THANKS

I don't know why it won't block radiant heat - I have some mounted-up with 1" pieces of emt conduit as stand-offs between the board and the studs behind it. leave a foot or so at the top and bottom so that air can naturally flow upwards behind the board. has worked really well for me in the past. Key is to not screw it directly to the studs or wall - if you do, it'll just transfer the heat it absorbs into your wall - doesn't shield this way, only slows-down the rate of heating of the wall you're trying to protect....

Your using the wrong product. You want millboard not cement board. See my post in another thread.

How to cut down on stove clearance space?

I found some heat-shield backer board product at Lowe's in the wood-stove aisle last February that I used on my basement ceiling above the stove and chimney pipe that runs about 12" below the joists. It looks like some kind of fire-retardent 1/2" compressed paper board (homasote?) with sheet of metal painted black on one side and wrapped around the edges. Per instructions found here on nepacrossroads, I used 2" pieces of conduit and 3.5" screws to mount it to the joists. I probably didn't need it, but I figured it doesn't hurt to be overly cautious about fire safety with the stove. My magnetic mount thermometer only showed 125-150* last winter. But, as 95% of my house wiring runs above it (my breaker box is 18" to the right of the stove), I'm confident I won't be cooking my wires! :>)

Millboard is what you want. No spacers needed. Here's one manufacture's description:

"InterSource offers a premium-grade, thin, dense ceramic fiber millboard product, which has excellent insulating properties and compressive strengths throughout its temperature use range. Our ceramic fiber millboard is produced in a unique, continuous board - manufacturing process from a blend of ceramic fibers, clay, insert fillers, and a small amount of organic/inorganic binders for increased handling strengths.

TaoFibre® ceramic fiber millboard maintains its strength and thermal stability throughout a wide temperature range up to 2300 ºF."

See: http://www.intersourceusa.com/millboard.htm

In my experience cement board makes a good heat shield and in at least one jusisdiction with strong codes and enforcement--Fairfax County, VA--it is accepted as a heat shield material when properly installed.

The manufacturer of one brand of cement board says it is suitable for heat shielding (go to the FAQ):
http://www.usg.com/navigate.do?resource=/USG_Marketing_Content/usg.com/web_files/products/prod_details/DUROCK_Brand_Cement_Board.htm