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Fire wall insulation

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The Moss kit I bought for the engine bay did not include the one for under the floor board. I made my own using the remains of the old one as a pattern. Found my hardibacker at Home Depot. I also used it on the carb shield, as someone mentioned above.

Griz
 
I had a similar experience, Alot of heat coming from under the dash. I put a fog machine in the engine compartment then put a fan in front of the grill. Smoke was pouring in from a gap between the front shroud and the fire wall. Sealant is required from fender bead to fender bead. Hard to do when everything is installed, had to remove the heater duct and a few other fire wall items. What a difference.
 
I read a previous post that said the manufacturer/distributor of Hardibacker said it had no insulation value, a claim questioned here by another poster on this topic. Having lived in a home sided Hardi product material, I find the claim that it has no insulating quality implausible. I used 1/4" Hardibacker to make the insulating panels totally absent on my Series 1 BN7, using the dimensioned drawings on Healeyp6. I, too, provided spacers between the floor and the insulating piece, simply small blocks of the same 1/4" material. I didn't use the Healey6 dimensions over the muffler, instead pretty much making the piece to cover the entire area between the frame members and the rocker panels. My car still gets hot--I now live in Florida--but I think the layer of Hardibacker provides an insulating benefit. Picture yourself with your handy propane torch and something flammable. Would putting a piece of this cement-based product between the torch flame and the flammable material not provide a level of insulation? I accept that bricks and masonry aren't the best insulators for residential insulation, and I've also used the aluminum foil-faced asphaltic material on the inside floor of my car, hedging my bets.
 
The 1/4" air gap is probably the main thing helping you. That's basically a heat barrier by itself. When the manufacturer of Hardibacker claimed it had no insulating value he was referring to conductive heat transfer. I have no reason to not believe him. The air gap you have created eliminates conductive transfer in that area and leaves radiant heat transfer as the only way for heat to pass. The white panels probably do not pass radiant heat very well so you see a reduction of heat on your feet. Any white panel would do the same thing though regardless of its material. Your HardiSiding on your house probably has an air barrier behind it as well which insulates your home slightly.

I also question the aluminum faced "dynamat" products that are marketed as heat insulation. The foil would do a great job of reducing radiant heat UNTIL you cover it with carpet. By eliminating the air gap you have eliminated the radiant barrier. Does the butyl rubber material insulate heat? I doubt it but maybe it does to some degree. I suspect the key temperature reductions people see are when they put some type of foam, bubblewrap, or jute layer in. While they no doubt provide sound deadening I really doubt they do much for heat. That aluminum layer should do almost nothing but make it pretty based on my understandings. Any engineers out there want to disagree? I'd love to know more.
 
Original Insualtion of the AH have a lot of lack -
Here my carpet and insullation Album
https://picasaweb.google.com/112770819864514987162/BN4LongbridgeCARPETSAndINSULATION?noredirect=1
The number ONE was the absence of insulation panel at the corner of the exhaust pies just under the pedals, adding a panel here helped me a lot
note the additional little panel in this photo
https://picasaweb.google.com/112770...dMayJune2013?noredirect=1#5711557515011699346
improvements of insulation under the floor can also help from hot warm seat
https://picasaweb.google.com/112770...dMayJune2013?noredirect=1#5626005150639413282
 
I contacted the manufacturer of hardiboard and asked to speak with a product engineer. He confirmed that hardiboard is not a heat insulator. In fact it had 100% heat transfer. The only insulation would come from any air space between the board and firewall. He would not recommend hardiboard for this application.
 
MikeAH100M said:
I contacted the manufacturer of hardiboard and asked to speak with a product engineer. He confirmed that hardiboard is not a heat insulator. In fact it had 100% heat transfer. The only insulation would come from any air space between the board and firewall. He would not recommend hardiboard for this application.
Click to expand...
AH Spares sells a product that is similar to Hardie Board and I saw "master board" on it someplace. It's a bright white and just maybe it's not like Hardie Board. Maybe you could check with them to see what they say about the product they sell? I saw a Healey fitted with polished stainless steel panels over the factory panels and the owner said it was to help reflect the heat away.
 
I wonder if NASA would make some of this stuff in the dimensions we need
 
before i retired i worked at a company that made automotive carpet for the oem suppliers. our carpeyss had an insulating material on the back and were formed to the floor of the vehicle. we also used an aluminum faced stick on that was placed at or near the catalytic converter of the cars floor pan. i got several sheets and have used it over the past several years. unfortunately i am down to my last irregular pieces. the material is approximately `1/4 inch thick with the heat side aluminum faced. the material adheres very well. i used this on my bj7 and no heats passes through the area covered. i am using the remaining pieces on my bn6 v8 conversion as well. i dont know what the material is but you would be hard pressed to find a better insulator..
 
I had worked in the steel industry so checked with a colleague who is a refractory engineer. He recommended that I look for a ceramic/silica fiber product. He also confirmed that a cement -based product like hardiboard would have no insulation capability at all - 100% heat transfer. I found the following company and purchased the ceramic fiberboard called Duraboard in the 2300F temperature grade. Very low thermal conductivity and was easy to work with. I put a torch to one side before installing and felt almost nothing on the other side. I made sure I added the Duraboard to the small area on the bottom of the footwell aft of the the brake/clutch assembly. Feet are cool.

https://www.thermalproductsco.com/index.html
 
I used 1/4". That was closest to the old asbestos that I removed.
 
Having now had it hammered into my head that Hardibacker isn't giving me any heat relief, I'm interested in Mike's solution. The Thermo Products site doesn't give info on the cost of this product and the dimensions available. Perhaps Mike can share that information with those of us (me) too shy to call the manufacturer?
 
Thanks Michael. I'm also curious if there was a minimum purchase, and how you cut it. Was it easy to work, or a PITA? Thanks. Jim
 
I ordered the Duraboard D500ES .25"x13"x 38.63" which cost $20.72 but the UPS freight was $24.79 for a total of $45.51 (June 2015.) That was enough for what I was replacing so you'll need to figure total area if replacing all the firewall asbestos It was very easy to work with. I cut it with a sharp box cutter/knife. It has the consistency and look of the old asbestos. Phone number for Thermal Products is 770.662.0456. The are located in Norcross GA.
 
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