THERMAL CONTROL MEMBRANE (TCM) -- any good?

Has anyone any experience with THERMAL CONTROL MEMBRANE (TCM)?

It’s described at savenrgvi.com/tcm.htm

It’s a foil blanket of five layers – three foil layers separated by two fiber scrim layers.

It looks “cool” as described on the web, but that doesn’t mean much. I can’t find any mention of it whatsoever outside of web pages and posted comments directly connected with the vendor selling it, which is not very reassuring.

In the particular application I have in mind, I’d put the following layers, top down, on my roof: 1) standing seam metal in some “cool” color, 2) this TCM stuff, 3) existing cheap asphalt shingles, almost new, 4) unknown cheap underlayment, 5) 5/16" OSB decking. That’s it. No built up roof, no purlins or battens, no rip-off, …

See my post yesterday for other specifics, at roofing.com/forum/viewtopic. … 5837#55837

(Well, to be precise, I’d be using a newly introduced variant of TCM in which the top foil layer is replaced with a white polyester film, but that’s unlikely to matter much to this discussion.)

[quote=“pj”]Has anyone any experience with THERMAL CONTROL MEMBRANE (TCM)?

It’s described at savenrgvi.com/tcm.htm
[/quote]

Well, to answer my own question, in case someone passes by here.

I went ahead and ordered a little sample of this TCM stuff to see just what it was. It’s not what I need.

The savenrgvi web site doesn’t do a very good job of describing it (strike one.)

It is essentially two layers of aluminum foil glued together with a coarse fiber net (about 1/2" holes) between. The fiber would have no affect whatsoever that I can see on the thermal properties. No air gap or any such thing. Thermally it’s just a thick layer of foil. The only use the fiber would have that I can see is to improve the mechanical tear resistance of the material. In short, unlike the air bubble or similar layered foil and filler products, which have their own built in air gap, this has none. It’s inherent R-value would be about zero (strike two.)

It ain’t cheap either; not price competitive from what I (a roofing newbie home owner) can tell (strike three.)

It’s time to consider a “real” synthetic underlayment with a cool white, grey or reflective surface, overlayed with battens to provide the air gap. A more conventional way of putting on a standing seam roof.

The science behind Thermal Control Membrane is similar to Low e glass, it performs by providing not one but several low e surfaces. It’s a common misnomer to attach “air spaces” to a low e surface since that’s what gives insulation the R factor: trapped air spaces.
Further, the distance between reflective surfaces is not critical to performance as is insulation products that do not have low e surfaces.
Your comment about “trapped air spaces” in the foil covered bubble wrap (brand name “Reflectix”), starts out with four reflective surfaces but loses 50% of the performance due to being laminated to the plastic bubble wrap which immediately allows heat to transfer through conduction.
The Thermal Control Membrane product is actually one of the best thermal inhibiting products available and the web site that sells it has 3rd party validation from a university showing a .02 emissivity which is the lowest I’ve seen from any reflective insulation product. savenrg.com is the web site I saw it on.
You are confusing “air space” with insulation and not taking in to account how a low e surface works. This method is used in spacecraft which is where I first became aware of multi-layered thermal products in my aircraft business.
In fact, for a metal standing seam metal roof, or any metal roof for that matter, this TCM stuff would be the ultimate roofing membrane since it’s not bitumen based, would never dry out over time from infrared heat (like all shingles and tar paper underlayment does), and since it’s multiple layers, would never be affected by dust.

[quote=“ayev8tor”]The science behind Thermal Control Membrane is similar to Low e glass, it performs by providing not one but several low e surfaces. It’s a common misnomer to attach “air spaces” to a low e surface since that’s what gives insulation the R factor: trapped air spaces.
Further, the distance between reflective surfaces is not critical to performance as is insulation products that do not have low e surfaces.
Your comment about “trapped air spaces” in the foil covered bubble wrap (brand name “Reflectix”), starts out with four reflective surfaces but loses 50% of the performance due to being laminated to the plastic bubble wrap which immediately allows heat to transfer through conduction.
The Thermal Control Membrane product is actually one of the best thermal inhibiting products available and the web site that sells it has 3rd party validation from a university showing a .02 emissivity which is the lowest I’ve seen from any reflective insulation product. savenrg.com is the web site I saw it on.
You are confusing “air space” with insulation and not taking in to account how a low e surface works. This method is used in spacecraft which is where I first became aware of multi-layered thermal products in my aircraft business.
In fact, for a metal standing seam metal roof, or any metal roof for that matter, this TCM stuff would be the ultimate roofing membrane since it’s not bitumen based, would never dry out over time from infrared heat (like all shingles and tar paper underlayment does), and since it’s multiple layers, would never be affected by dust.[/quote]

Thanks for responding. However I can’t say as the response makes much sense to me.

There are three ways to move heat: convection, conduction, and radiation. Moving air currents move heat by convection. Solid materials conduct heat through the material (copper conducts quite well, for example.) Concentrated mass (plasma, hot gas, liquid or solid) will radiate heat into the open space (vacuum or air gap) next to them.

Low emissivity materials coated on the inside of a window pane will keep that pane from radiating heat into the interior. The glass may still be hot from the sun shining on it, but only the air currents, via convection, will pick up that heat by direct contact. Adding a second pane of glass keeps nearly still air trapped in the space between the two panes, reducing the convection heat coming off the outer, low-e, pane even more. However even still air conducts heat (the third way) a little, so a little heat will move from the outer pane to the inner one.

Low emissivity materials such as attic radiant barriers and aluminum sheeting products on the interior of unfinished metal roofs on sheds and barns are working into large air space (the attic or building interior.) Like the low-e glass, they help by not radiating heat inward, though they still can feel quite hot to the touch, and some heat, quite a bit less, will still move by the convection of circulating interior air touching the hot surface and then moving to occupied portions of the interior.

Spacecraft are working in a far larger vacuum, and for them low-e surface materials, --because-- such materials are always at the same time low absorbers of radiated energy, are an essential cooling mechanism. The heat bounces off back into space before heating anything.

The TCM material didn’t have a gap. It was mostly zero gap. The two or three foil layers are directly touching each other more often than not, except where the sparse shim (fiber netting with 1/2" holes) slightly separates the foil layers. If such material is sandwiched between other solid roofing materials, such as when used in place of the usual tar paper underlayment, then this is little better than sticking a few layers of tin foil between the roof coating (metal, say) and the roof deck. Heat directly --conducts-- between the various layers that are in direct contact. It doesn’t matter if the material is some perfect zero emissivity product. It’s not the --radiation-- of heat into an open space that matters when there is almost no open space and instead much direct contact. And where there is not direct contact between the foil layers of TCM, due to the shim netting, there is a very thin layer of air, which will conduct heat fairly well. Most any material short of an absolute vacuum will conduct heat to some degree, depending on how thin the material layer is.

Putting tin foil (or expensive equivalents) between my roof layers sounds like a waste of money to me. Low-e surfaces work when there is a gap into which they don’t radiate.

You are correct, there is 3 types of heat and radiation is the most misunderstood. Hence you not being able to grasp the effects (and benefits),of multiple low e surfaces facing each other.
You are also correct in that when compressed, TCM will not be of much benefit, nothing can touch a low e surface or will simply conduct heat. If used under a metal roof (as can be seen on photos at www.savenrgvi.com), you will see the TCM being separated by wood battens which allows for the infrared heat to be rejected by the TCM. That’s where I first saw TCM being used and pulled off the road to see what they were using.
I’ve used TCM on my own applications (in my shed, above the headliner in my black station wagon, around my camping cooler, around my freezer in the garage), the effects are amazing.
I ordered a sample from the manufacturer online who suggested I take the sample and lay it in my hand. I did and I felt my body heat within two seconds. I’ve tried this with the bubblepack (Reflectix), product and other foil radiant barriers and so some degree I can feel the same thing but not as quickly or as effectively as TCM. Not scientific, but proof enough for me to order a 500 square foot roll and play with it. Impressive stuff, I only wish I had an attic and not a flat roof to use it to lower my bill in my house.

In such an application, the heat transferred across the air gap bordering the TCM would be what could occur by convection or conduction. If that air gap is vigorously vented, then the air flowing through will be at outside temperature, minimizing either of these ways of moving heat across the barrier. Such venting is difficult to achieve and maintain. Ordinarily, one will end up closer to having an air gap holding rather still air, in which case one then needs to inquire as to the thermal resistance of that air.

I chose to put down three inches of polyiso instead of the TCM and air gap. From what I can tell looking at the Polyisocyanurate and “List of thermal conductivities” articles on Wikipedia, both polyiso and air have similar thermal conductivity (inverse of thermal resistance) of about .023 W/mK. Air is slightly more conductive (poorer insulation) than new polyiso, but polyiso may lose half its resistance with outgassing, depending on how well encapsulated it is.

So this discussion seems to boil down to an issue of the construction and maintenance costs of the two alternatives.

The choice of metal or roofing that you use above the gap or foam affects this as well. If it runs hot (black asphalt) and if one can get a well vented gap, then the ambient temperature air blowing threw the gap will be much cooler than the hot roofing above it, improving matters. If one uses a light, “cool” coated metal, then the metal is already much closer to ambient temperature and the choice of air gap versus polyiso becomes a matter of construction and maintenance costs, as per above.

This type of wonder material, multiple layers of foil in one configuration or another, has been around for years and years. One name used was Roifoil. In a lab it sounds great, but it is questionable whether it really contributes much to keep a building cool. As you mentioned, add insulation and you will be mostly sure of what you have.

Kind of like the line…if it seems too good to be true, it probably isn’t.

Someday I am sure the industry will come up with a miracle insulation products that works in the everyday home or business.

i agree w/ donl. this is crazy! just up the inches in poly iso board for r factors. then to keep the roofing costs down insulate the inside of the roof as well w/ owings corning pink panther or something.

[size=16][/size]
“thicker is better” is what has been driving building professionals and codes since codes began. I agree, when I’m cold I put a sweater on. If that’s not enough, a jacket over that. However, I doubt I would be doing this in August in Arizona.
There are two choices: resist the flow of heat (R Factor) or change direction radiant barrier. I live in the desert, not trying to keep heat in. I put TCM in my work van and the effect was immediate and nothing short of amazing. An identical van with rigid foam board is an oven in the summer.

I’m considering wrapping my block home in it and re-stuccoing the exterior. There is some incredible information on the horizon site about a block home that was built without insulation, only a radiant barrier. I’m convinced. This stuff is the future.

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