Metal Fireplace Mantel; Distance & Depth
This is my first posting. I apologize in advance for itÂs length. We will soon be having a flush mounted, wood burning fireplace insert installed. Our house is a 1950's contemporary and we want a simple look. After the insert is installed we will put up a mantel shelf (no surround, just a shelf). Our ceilings are not incredibly high, and at some point in the future we want to put a big screen TV above the fireplace. To conserve space (height) we'd like to be able to mount the mantel shelf lower than the limits dictated for flammable materials. So, as we see it, we have two shelf choices, stone or metal. We have toyed with the idea of a manufactured stone shelf, perhaps fabricated as a floating shelf, with no supports visible. But that could get expensive (like, more than the cost of a TV). Another option is a metal (aluminum) shelf. They can be had at the right length (about 5 feet) for less than $150 and are an easy DIY install. The aluminum shelf has a slight upward lip at the front edge so decorative items like stones/fossils or pottery can be displayed with no fear of them falling off.
So, to my question. I'm aware of the NFPA Minimum Mantel Vertical Clearance data. But these apply only to flammable mantels and do not consider the most efficient movement of heat away from the upper fireplace wall. What I'd like to know is; is there data available for the best depth of shelf and height of placement (relative to insert and TV) for a stone or metal shelf. Clearly the deeper the shelf, the more air it will deflect. But at the same time I'd like my shelf to be as shallow as possible. The fireplace will be "flush", the future TV will be "flat". The last thing I want is a two foot deep shelf! Also, my assumption would be that the lower I mount the shelf, the more heat it will deflect from a TV. But perhaps itÂs the exact opposite! Doubtless the aerodynamics of convection and the physics of radiation are far more complicated than I have considered.
If anyone knows of some proven rules of thumb or actual researched data it would be very helpful. Any informed opinion about the use of a metal shelf (I know metal is a good conductor) would be much appreciated. I will of course be doing temperature checks on the upper fireplace wall, once the new insert is installed. The metal shelf I prefer is 4 inches deep, though there is another I could use which is 5.5 inches deep. And nobody needs to lecture me on either the aesthetics of a TV-over-fireplace installation or on the potential body mechanic consequences. Our current TV is mounted high on a shelf next to the fireplace and it all works very nicely. I am also keenly aware of the potential harm heat and smoke can cause to delicate electronics. But thats why IÂm asking this question. IÂve read lots of good information on this forum and am hoping thereÂs a smart member out there who can help me get this right.
I thank you most kindly for your time. And in advance for your assistance.