The REAL scoop on bubble foil insulation

[heaterman]

This is just a FYI type post brought about by a visit to an installation the owners are having difficulty heating.

Long story short, the owners contacted me last summer regarding a heating bid for a 10,000 sq ft equipment repair shop. I was "way too high" according to them and they went with a low price guy. I had spec'd a Garn WHS 2000, 1 1/2" EPS foam under the floor, 5/8" pex along with appropriately sized piping, circs and variable temp mixing. etc, etc.

The bid they went with from the CB dealer used bubble foil under the slab and the installer assured the owners that the R-value was superior to foam............. Riiiiiiiiiiiiiight.

I heard from an acquaintance that they were having to fire the CB 4-5 times a day, this is the largest unit CB makes, and they were turning over 2 pulp cords a week into ash trying to keep the building above 50*. The building is a brand new pole structure with 8" of cellulose in the walls and 14" above the ceiling. Two large overhead doors, one on each end but other than that no areas of huge heat loss. So I went to have a look..........There is no snow within 3' of the entire exterior of the building as we speak. The grass within 18" of the south side of the building is actually green.

All together now, can we say HEAT LOSS! I wish I would have had my camera along. The CB was belching smoke like a coal fired locomotive.

Anyway, here's a link to a website run by an extremely sharp guy who's been in the hydronic and radiant heat business a long time. Read through it before you install anything insulated with bubble wrap.

(broken link removed)

 

[Nofossil]

Radiant barriers are poorly understood, and that leaves the door open for the snake oil salesmen.

I spent a lot of time studying the physics and the math involved in the performance of radiant barriers, and finally decided that controlled experiments were the only way to answer the questions that I had about how and where to use them effectively. Unfortunately, I was still early in my learning curve on sensor technology, and sensor failures wiped out the data I had hoped to gather.

It is certain beyond doubt that there are places where a radiant insulation system outperforms traditional fiberglass / mineral wool. However, there are tradeoffs where there is no reasonable way to determine the best approach. For instance, radiant barriers need an air gap in order to work. The ideal gap size is impossible to determine. Too small and the system is less effective at preventing radiation loss. Too large and convection cells start up and increase convective loss. The ideal gap is different for horizontal versus vertical installations. It varies with both the temperature and the temperature differential. Horizontal baffles can decrease convective loss, but increase conductive loss.

If you have 6" to work with, what's the ideal combination of insulating techniques? Is it worth dedicating 3/4" of your precious space to an air gap? How about 1 1/2" so that you can have two air gaps? If you have a radiant gap, should it be closer to the hot side?

I found no resource that could help me design a hybrid insulation system. Not surprising that these systems are disappointing in practice, even without the added problem of unscrupulous salespeople.

I think it's safe to say that installing a radiant barrier only makes sense if it has an air gap, will stay clean and dry, and has a relatively large temperature differential to work with.

I did make extensive use of sealed radiant barrier systems as well as conventional insulation in the construction of my storage tank.

 

[heaterman]

The air gap is the thing and the thing with air gaps is that very very few are air tight. In a situation where a structure is being insulated, a product that inhibits air flow will prove to be far superior for that reason. This is illustrated easily on heat loss programs that can compare fiberglass to dense pack cellulose.

Since the bubble foil only works with an air gap, it's easy to see why it is totally ineffective under a slab. Might as well use nothing at all if your contemplating bubble wrap for that purpose. Same goes for using it to insulate underground tubing. Where's the air gap there?

Moral of the story..........even in this high tech age there are still many companies that use Barnamesque sales techniques. makes me recall an ad for one of those Amish made electric heaters you see people blathering about all over these days. What do the Amish know about electric heaters???

 

[Eric Johnson]

"It's new! It's improved! It's old-fashioned! It's the only product you will ever need!" --Tom Waits

 

[leaddog]

Doesn't the bubble air in the bubble wrap give an air gap????????????? Or isn't that enough?????????? With the foil on both sides of the air bubbles it seems like it getting dirty isn't posible????????? Should you or should you not use it to wrap a tank?????????? Questions questions questions.
leaddog

 

[atlarge54]

Is EPS expanded polystyrene, the blue or pink stuff like used on basements? Will this poor guy who's heating the earth have problems with floor cracking as the bubbles degrade leaving no support for the concrete?

 

[slowzuki]

The short of it is no. There have been piles of testing on it up here in Canada and due to the test results, you can't get a mortgage approved if you want to use the stuff as your main insulation. I think they allow R 1.2 or something for it due to the air gap. There is another product with the same type of problem called P2000 which is eps with a foil face on one side. Advertising ridiculous R values and charging a retarded price for basically bead board.

Doesn't the bubble air in the bubble wrap give an air gap????????????? Or isn't that enough?????????? With the foil on both sides of the air bubbles it seems like it getting dirty isn't posible????????? Should you or should you not use it to wrap a tank?????????? Questions questions questions.
leaddog

 

[SE Iowa]

I no nothing about physics, but I did put a reflective barrier under a vapor barrier that was under the foam that was under the slab. It would seem that the foam, which is 2" of tiny air pockets would be the airspace inbetween. It should stop the convective and conductive heat flow. I then assumed that the radiation would be reflected with the foil. I assumed that their wouldn't be an issue of dust etc and it should stay in tact since I placed a vapor barrier b/w the foil and the concrete. Now I feel like I wasted my time and $. Oh well, I guess it is impossible to tell if it really is doing anything. I'll just live in denial and assume I'm saving hundreds of dollars per year like the sales info said. Ignorance is bliss!

 

[slowzuki]

It is a great vapor barrier and it still like R1.2 or something so don't feel too bad.

 

[88rxn/a]

hmmmm, i didnt know radiant heat was so touchy?? or is this just slab?
i bought some of that reflective bubble wrap at a nearby hardware store to use between my floor joist's to make the air gap and reflect the heat upwards (installing it under the floor of the 1ST floor in my house, access throught the basement). it was a roll said to be used for heat or cold reflection.
should i return it and get my money back??

 

[Buck1200]

Without the air gap you simply conduct heat right through the foil face. And due to long term (it actually doesn't take very long at all) accumulation of dust, what true reflective quality an underfloor application is providing will disappear and leave you with nothing more than the R value of the bubble wrap, which Slozuki mentioned is about 1.2. Use foam board or lots of batt insulation instead.

The only place I have seen it used appropriately within a house is on the underside of roof rafters where dust cannot collect. Here however, the low emissivity of the aluminum foil prevents radiative transfer of energy from the hot summertime roof to the interior. Reduces AC loads.

 

[loggie]

I have staple up radiant pex under my first floor and I have done some rooms with R13 fiberglass one with R19 foil faced with the foil up and a couple of rooms with the foil/foam radiant barrier and the foil/foam is the best performing but the air space needs to be 2 or 3 inches it is too costly in my opinion and I will try ripping foam board and pushing that up for the last room but I doubt it will outperform the foil/foam.I have read that the unisulated slab edges are the biggest heat losers and probably even more so on a pole build.

 

[Redox]

That 'ol Earth makes a great heat sink. Can I put my ground source HP loop under his next install??