Bubble Foil Underslab Study

Jason Horner

two jpg images....sorry about the quality...if you zoom them they are much more readable

Glen

cmhc

howsabout a url so we find and print it ourselves???

Dave_14

www.plumbingandhvac.ca

Dave_14

Here is the web address of the article posted. I will check to find the original file of the research.

www.plumbingandhvac.ca

Dave Hughes

Bubble Foil research article.

Unknown

survey says!

Bubble insulation under slabs is crap!

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Rick Kelly_3

Say what?

Rick Kelly_3

Say what?

Is anyone in the USA familiar with the aformentioned Steel Skinned Polyurethane panels? Who makes them? Where are they available?

Unknown

I'm not familiar, but here's a link I found:

http://www.kt-metal.com/prod03.htm

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Ted_9

I'm so glad I only have one floor done with bubble wrap and it is below grade and the radiant heat is awesome in that room.

PATRIOT HEATING & COOLING, INC.

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ken fitzpatrick

steel-skinned polyurethane

Good to see a little numerical evidence to back up the anecdotal we've been hearing for a while.

A little more surprising was the performance and cost-effectiveness results for the steel-skinned polyurethane.

Interesting, thanks!

stevel

insulation

I bought mine from a window and door manufacturer
@ 50 cents a piece

Grumpy_2

Insul-tarp

So where does a product like insul-tarp fit into this equation? Are they suggesting that it is in the same category as the bubble product? Or is that the product they are speaking of?

Jason Horner

They were only looking at the bubble-foil-bubble product.

However I'll speculate that the 'tarp' product will have similar performance issues as there is not enough resistance to conductive heat transfer.

I stand to be corrected.

Unknown

The RFA (reflective foil association or something) and some org in canada both released results from studies recently regarding underslab foil based products. They are all crap under slabs. R1 plus another R1 from elements present in all slabs... far cry from the "R10" their marketing fellows were trying to claim.

One of the more recent RPA newsletters reported on the findings if you want to corroborate.



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ScottMP

Ted

Just think how well it would be working with a better insualtion

This is really interesting.

Scott

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ScottMP

I would think

That the issiue here would not be the foil covering but the insulation value of the air bubbles. Along those lines would'nt the insulatarp work better than the bubble foil ?

Insulatarp has a multi layer of foam as compared to the "bubble wrap" material.

I really wish this study had used insultarp. I would like to see the performance numbers. Any one have any independant studys ?

Scott

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Wayco Wayne_2

Yikes!

I got a job coming where I recommended insultarp. I would like to know if there's a problem. I've got another job where I used it and it's working well. WW

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Floyd_7

Now I'm really twerplexed.........

if this stuff is such crappola......
how the heck am I heating a 10,500 sq. ft. firehall for so little?????? The bill for last Feb. was less than many of the fireman's cost to heat their houses......
Must be the two Ultra's........
Darn I guess I could have made them look much better yet.....

Floyd

cruizer

Theoretically during startup, I can see the foil based bubble insulation working quite well. The radiant heat is reflected from the foil back into the space, therefore heating the room more quickly. But one the space becomes saturated with heat, there is no more reflectivity, and the heat just migrates past the bubble foil insulation. For this reason, I have never been a fan of bubble foil insulation.

But in my opinion, a more thorough study needs to be done. The study needs to include a few types of insulation: different brands of bubble foil, foil backed foam, non foil backed foam, and a non insulated space for control (perhaps some others that I have forgotten). These should be done in below grade and/or slab on grade applications, and incorporate the many styles of installations: perimiter installation (2' 4' and 8' into the interior), and full floor installation; all with a combination of edge and non edge installation. The factors that need to be looked are: water temps leaving the boiler, water temps of the floor, heat saturation into the space, time until t-stat is satisfied, boiler run time, time from t-stat satified to time of call for heat, temps of the space, temps of the floor, temps of the ground under and outside.

But the problem in conducting a test such as this would be quite costly.

ScottMP

Flyod

Did you use Bubble foil or Insultarp ???

Scott

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Unknown

Insultarp is still relying on reflectivity to acheive its R value equivalency claim, I believe.

adding an R1 thermal break under a slab is not useless; it's just not cost effective if you can spend a little more and get a real R10.

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Unknown

You're forgetting a key factor here;

There is practically NO radiant transfer happening under a slab. You're dealing with conduction, not radiation, and as such the reflectivity of the foil is practically useless there. Startup or not, doesn't matter, radiant transfer needs space, more space than a small bubble of air provides, to take over as a primary form of heat transfer.

Having insultarp or other products like it under the slab is better than nothing. Jumping from an R1 to an R2 is a really big deal from a heat loss standpoint and far better than not having any insulation at all. However, R10 is definitely better, and as this study points out, the cost benefit ratio really isn't in the foil products' favor.

Perhaps in walls it can be made effective, or ceilings to reflect downward, or under roofs to reflect heat out from the sun. As an underfloor or underslab insulation though, foil is crap. Better than nothing, but not worth the money, IMHO.

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ScottMP

Insultarp

Claims - R 9 ?

My insultarp has No Reflective barrier. It is black on one side and white on the other. I agree that except for a wall space I see no benifit from a reflective coating.

Scott

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Unknown

scott, unless I'm smoking crack (which I gave up long ago!) insultarp has a reflective layer included in its construction and is marketed as a 'radiant barrier'. at least that's what it says here http://www.insulationsolutions.com/

and here http://www.insulationsolutions.com/products/InsulTarp they claim 93% of downward heat loss in a heated slab is radiant in nature.

I'm sorry; that's just wrong, unless they are saying the ground radiating the heat to the air is the radiant part of it.

They don't claim an 'r10', or r-anything on their website. However their marketing people have been spouting r10 as an approximation of their product's performance for years. This is **** as well, as the slew of recent studies have proven.

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ScottMP

Pass the pipe

Bob, I would love to see those reports. Do you have any links ?

Let me go look at the roll out my shop.

Scott

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Constantin

Actually, the Canadians did a test like that..

... which showed that radiant barriers under slabs do nothing much. The test houses were identical in construction, save for the under-floor stuff, which allowed for a fairly even-handed test of temperatures inside and outside the building envelope.

Among other things, the test measured the temperature of the earth under the house. The smaller the ΔT between the slab temp and the exterior ground temp, the less effective the thermal barrier is. One conclusion that I seem to recall was that Insultarp, et. al. is, at best, a thermal break underground. Better than nothing, but definitely not cost effective when compared to XPS and other "real" insulation materials.

Is it going to have a huge effect on your gas bill whether you use one material or the other? The answer, most likely, is no.

The ΔT between the earth and the foundation/slab is relatively low, at least compared to the exterior temps in most areas (55°F vs. -15°F). Furthermore, many soil conditions make for excellent thermal resistance, such as the sand, gravel, etc. usually found under slabs these days. Lastly, even if the soil is pretty good at conducting heat, you get some side benefits, such as flowers that bloom a lot sooner around the house, as Dan described his childhood experience in Levitton (sp?)

Meanwhile, an uninsulated underground basement will benefit from the thermal mass storage effect the heating and cooling of the earth around it has. This is the main reason that Building Sciences Corp advocates the usage of exterior insulation on foundations, where possible. When foundations are insulated this way, you get the benefit of the thermal mass while minimizing heat loss/gain. Plus, there are some moisture-related benefits as well.

Floyd_7

foil, bubble, bubble,white poly......

I was going with the bubble stuff because it seemed to be too difficult for the constructon guys to get it through their thick skulls that I needed an extra 1" for the blue board.....when the would grade for the concrete. With the buble stuff I could let them do as always and I could just roll it out and everyone was happy. Funny thing too is.... I think that when I figured piping and spacing requirements I figured at least something for r value under the concrete... I'l have to go back and double check my numbers. The Firehouse job I even know that I screwed up and insulated the piping where it all ran back through a kitchen area so as to not over heat the kitchen, was really sweating that when I thought of what I had done......but, there has been no problem and the system has worked wonderfully......
maybe it could have worked better yet......

Gotta run.... starting up another Ultra, to replace and old CI monster in a small bank tonight.....packing up the laptop for a LOOOONG night...:-)

Floyd

Unknown

I'm having a hard time finding a link for that study but constantin is correct as far as it being done and finding that subslab reflective insulations aren't worth a lot. You get an R1 thermal break, which effectively doubles the standard downward resistance, which is far better than nothing. However it is only an R1.

Also the October 2004 radiant panel report is reporting on RIMA's study on its own product that way as well, with pretty much the same results. That result being, under slabs reflective insulation is about an R1.

so it's better than nothing, but for the difference in cost between it and foam board you get a lot more insulative value with the foam.

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ROJOHO

Do you mean

that you are satisfied with it's performance?

hr

I've done some backyard Insultarp testing

And my info shows it preforms as well as 1" of foamboard.

I have half my drive done with 1" Dowboard and 1/2 done with Insultarp. What I don't have YET is a data logger to watch the difference and record it over a longer period.

I hope santa doesn't pass me by with my data logger

I have also tried Insultarp and 1" foam on a local skating rink at about 10° F surface temperature. Again I have permission to use the rink for an overnight period, but the data logger again woyuld be better than sitting on the ice all night

The are other good benefits from the Insultarp which does have reflective surfaces inside the blanket, and bubble and closed cell foam layers. It performs very well as a vapor barrier which foam can and does not.

It does not break apart when walked over like 1" foamboard does. This must compromise the R-value.

Most important, in my area, is it is resistant to termite damage. I know for a fact foamboard isn't Dow and other manufactures admit that and have done so at various RPA panel discussions.

I have no problem calling it an R-1. And if I can prove over a 24 hour period or longer in an actual application with sensors located under the slab, foam, and 12" deep in the subgrade... Then to my way of thinking I can tell customers it performs as well as the 1" foam commonly used in this climate.

Much smarter folks than me have tried to model downward loss from a slab. The variable is always the type of soil or fill UNDER the slab! Every attempt I have seen to model this becomes mired down with the endless varriables of subgrade AND the moisture content.

Around here the base rock used as slab prep material is very porus and I suspect a very poor conductor. Pea gravel is another common backfil. Fairly good compaction rating, poor consolidation factors. Again lots of trapped air space= poor heat conductor. Not unlike foam or glass insulation which depends on trapped air for it's insulative qualities.

If you build on solid granite, that's a completely different story. If you, foolishly, build on clay or wet subsoils then again you have a very high conductive subsoil to factor in.

It's the edge and perimeter insulation that pays big dividends. I'm not convinced the mid slab with well insulated perimeter and edge is as critical of a detail.

Then again show me the ASHRAE test results

hot rod

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Unknown

you're right on regarding the variables, and not all slabs need any mid area insulation, depending on those variables and slab heating usage requirements.

and, again, adding an R1 is twice as good as not adding it, so a slab with insultarp will in fact peform better than a slab without it.

but cost/benefit speaks for itself. If you're going to insulate, the few extra bucks for foam and vapor barrier make a difference. at the *very least*, it makes a difference for the edge and perimeter.

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hr

It's not always just a few bucks!

I'm bidding a 16,000 foot truck repair facility currently. Pencil that out and see what the difference is $$ wise between just edge and 4' perimeter compared to the entire slab.

Plenty to make some owner decide to go with unit heater, with their low efficiency numbers and layer of 90° air at the ceiling!

Be interesting to pencil out my condensing boilers compared to the unit heaters operating cost over the long haul.

I guarantee the unit heater bid doesn't include edge and perimeter insulation.

Not to mention safety and employee benefits from working on a warm slab compared to a slippery cold one

hot rod

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Unknown

I don't get what you are saying; if you're saying sometimes you need to make do with perimeter and edge insulation, I agree, I am simply saying for that insulation I would not compromise on 2" of foam board.

under the middle of course there is far more leeway in many cases.

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Ron Schroeder_3

Hi hot rod,

I would suspect that your ice rink test would show the bubble foil to be R4 to R7 better than if it was under concrete since it has one low emissivity surface facing air rather than touching a solid. It is also probably gaining R1 or R2 from not being perfectly flat and touching the ice over the entire bottom surface.

The Insultarp is also gaining some R value for the same reasons but probably not quite as much due to the non shiny covering but it looks like there are several air layers that wouldn't be there in an under slab instalation.

Ron

hr

It is under a chunk of concrete, Ron

that is a 4" thick 16" square of concrete on top of the Insultarp and 1" foam. The sensor os located between the concrete slab and the top of the insulation.

trying to duplicate a slab over frozen ground.

I will build a 4" thick foam box around the top and sides of the concrete chunk, onn the next set of tests, to minimise the surrounding air temperature effect.

What do you think?

hot rod

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hr

It is under a chunk of concrete, Ron

that is a 4" thick 16" square of concrete on top of the Insultarp and 1" foam. The sensor is located between the concrete piece and the top of the insulation.

Trying to duplicate a slab over frozen ground.

I will build a 4" thick foam box around the top and sides of the concrete chunk, on the next set of tests, to minimize the surrounding air temperature effect.

What do you think?

hot rod

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Ron Schroeder_2

That setup sounds good except that you should just make the boxes around the edges of the foam and leave the top exposed. Make sure that your temperature sensors are very thin to not create any air gap.

Ron