R value

[Cyngbaeld]

I'm trying to find the R value of tek foil insulation. Specifically, the foil/bubble/bubble/foil one. Looking at the farm tek catalog and it says high r value, but doesn't give it. Planning to use it to insulate under the mobile home. All my insulation was ruined in the flood and has been removed. I like the idea of something that mice and snakes won't find attractive for nesting.

[Up North Louie]

It looks a lot like Reflectix, which is sold where I work. For a crawlspace application it is rated by the manufacturer at R16.8.

I like the stuff. We used a lot of it in many applications when we re-habbed our old house for my brother.

Here's a link to it.

http://www.reflectixinc.com/script/p...duct.asp?ID=97

Don

[huisjen]

It's hard to say because R value is specifically about heat conduction. Bubble wrap/ foil barriers mostly work to prevent heat escaping by radiation. You can make claims, but it's an apples to oranges comparison.

[SolarGary]

Hi,
If you use the R values published at the Reflectex site, read all the fine print carefully.

These materials have little insulating value in the traditional sense -- they get their R value by having layers of air and reflective foil layers. How well this works depends a lot on how its installed --its more effective as an under floor insulator (with heat flow down) than as a vertical surface insulator. Its worthless if you don't maintain the air spaces that they call for.

If it were me, I'd stick with conventional insulation. Maybe a rigid foam board insulation would be more resistant to critters?

Gary

[farminghandyman]

my guess is it is actually less than 2 R there is not enough thickness to do more.

http://www.reflectixinc.com/script/u...cal%20Info.pdf

in there technical paper they do not post a R value,

and on there R page http://www.reflectixinc.com/technology/rvalue.asp they do not post it either,

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http://rvalue.net/ says that Extruded polystyrene is 5.00 per inch, so lest jsut say it its the same per inch, (which is one of the highest R values of Nealy any insulation, the foil is only, 5/16 of an inch, and if it was the same, it would only be, about 1.5625 R, and my guess it is not as good as the polystyrene, as most insulation works by trapping air and being a material that does not transmit thermal energy ea sly, yes plastic is not a good transmitter but the air space is must to small to be very effective,

yes the foil will reflect infrared energies back into the living space, like a space blanket, but very little thermoresistance.

But foils have been used in fiberglass and on foam sheets for years, but the foil it shelf has nearly "0" thermoresistance, or no or very little R value, check out a sheet of aluminum foil.
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there are ways of increasing R value in the way it is installed by putting air spaces, on or near walls and and on some other bubble wrap sites I see their have a elevated R values, if you leave air spaces and do this or that, with it, the air space has it own R value ratings , one could do the same with layers of plastic sheet, and have two 1" air spaces and you would have a fair R value in jsut that, if the air can not convect, as trapped air is the basis of most insulation in the first place, that is how fiberglass works it it traps air and slows or stops it movement, depending on it density, there is also infiltration issues and if you can stop infiltration you have a lot of the heating game won.

and most all the claim is made with the reflective values of the bubble wraps, with there foil.

yes IF I do the test with a infrared heat lamp I will probly show good or equal results as with a comparable insulation with a R14 or so, but if it is jsut a heated box my guess is the true R values are down to less than 2,

look at this report ,

What about the R-Value?
Some of our products do have an R-Value. For example, Single Bubble Foil has an R-Value of 14.3, Double Bubble Foil is R-14.8. However, No-Tear has no real R-Value. http://www.we-intl.com/rfoil_faq.html#rvalue

note:
the company doubles the foil to a double bubble type and the rated (by them) value only goes up .5 R, and if you read the rest of the site, you will see the term reflectivity and reflection not resistance.

Where should the air gap be?
The best way to think of this is: 1) The best way, 2) The second best way, and 3) The third best way.

The best way: There are two air gaps of at least 1" on both sides of the foil.

The second best way: There is a 1" air gap between the foil and the other building material (drywall, sheathing, roof, etc.). The placement of the gap will depend on where you live. If you live in a warm climate like California or Florida, the air gap should be toward the outside (i.e. between the wall insulation and the foil.

There is not a major difference in performance between the first and second methods.

The third best way: There is a 1" air gap on the opposite side of #2. For example, you live in Florida, but you put No-Tear directly against your roof sheathing, rather than underneath your rafters.

note they are promoting the air gap method of installation and one would come to the conclusion that that is how there R test was made as well.

Personally I think there is a lot of smoke and mirrors, in there presentation,

From the journal of light construction

Q. Are Bubble-Wrap R-Value Claims Accurate?
Am I the only one confused by the claims of manufacturers of foil-covered bubble wrap and foil-covered flexible thin plastic foam? Apparently, if one is to believe the advertising, a 3/8-inch-thick roll of foil-faced bubble wrap can give you the same thermal performance as 2 inches of rigid foam insulation. How is this possible?

A. Martin Holladay, editor of Energy Design Update, responds: The R-value of 3/8-inch-thick foil-faced bubble wrap is about 1.3. The R-value of 3/8-inch-thick foil-faced expanded polystyrene foam is about 1.6. ...

Quote from larger answer, but this how I would see its R value, http://www.jlconline.com/cgi-bin/jlc...c07df1&p=1&q=1

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R values of normal insulations, from state of Colorado, good site, worth the look,

http://www.coloradoenergy.org/procor...f/r-values.htm

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note: jsut a 1/2 inch air space is a 3.23 R, so if they added that to the foil bubble wrap, your up to a 6.46 with out the bubble wrap,

[Nevada]

Originally Posted by huisjen

It's hard to say because R value is specifically about heat conduction. Bubble wrap/ foil barriers mostly work to prevent heat escaping by radiation. You can make claims, but it's an apples to oranges comparison.

While the foil portion of the insulation described in the original post prevents heat leak through radiation, there's no question that the dead air spaces in bubble wrap prevent heat conduction. Bubble wrap, therefore, has to have an R value.

From the reference below, one layer of bubble wrap typically has an R value of about R-1, so the double bubble wrap described in the original post probably has an R value of about R-2. However, it may actually be a little higher than that due to the additional dead air spaces located between the two layers of bubble wrap.

******
The bubble wrap has a short payback in cold climates. About 2 months for single glazed windows, and half a heating season for double glazed widows. Details on payback:

For an 7000 deg-day climate (northern US), and single glazed windows, the bubble wrap increases the R value from about R1 to about R2. This cuts the heat loss from the window in half.

Heat losses with and without bubble wrap for 1 sqft of window are:

Heat loss w/o wrap = (7000 deg-day)(1 ft^2) (24 hr/day) / (1 ft^2-F/BTU) = 168K BTU per season

Heat loss with wrap = (7000 deg-day)(1 ft^2) (24 hr/day) / (2 ft^2-F/BTU) = 88K BTU per season

If you are heating with natural gas at $1.50 per therm (100 CF) in an 80% efficient furnace, then the saving for 1 sqft of wrap for the season is:

Saving per sqft = ($1.50)(168K - 88K)/(100K*0.8) = $1.65 per season per sqft of window
http://www.builditsolar.com/Projects...bubblewrap.htm

[Cyngbaeld]

Thanks. I appreciate the help. I can't really get foam sheets under there and I do not want batts again. I found snake skins in what I pulled out! I think I can manage the 1 inch gap under the floor.

It doesn't get very cold here. Even so, the electric heaters weren't getting the house warm when the temps dropped into the 20s and 30s for a few days. Keeping the house cool is a bigger problem.

[LamiPub]

I don't know much about this stuff so just throwing this out there....if you had to use the batt insulation again...could you just attach some kind of tightly woven hardware cloth over it to keep out the critters?

[DrippingSprings]

Originally Posted by LamiPub

I don't know much about this stuff so just throwing this out there....if you had to use the batt insulation again...could you just attach some kind of tightly woven hardware cloth over it to keep out the critters?

I know someone who had a problem with critters and used regular insulation and covered the whole bottom of the mobile home with chicken wire. Worked like a charm

[huisjen]

I'd feel more secure if I used somthing more solid, like 1/4" chipboard, under the insulation. I noticed in Nevada's house pictures that that's what he's got (or somthing very similar) supporting and protecting his floor insulation.

Just to throw out a few numbers here from Pocket Ref:

Material                          Thickness                            R value  
non reflective air space            3/4"                               1.01
reflective                               3/4"                               3.48
foil, 2 reflective surfaces          1"                                  1.39

hollow conc. block                   8"                                  1.11

concrete wall                          8"                                  0.64

gypsum drywall                      1/2"                                0.45

fiberglass batt                        1"                                   3.30

cellulose, blown in                  1"                                   3.25

softwood                               1"                                   1.25

polyisocyanurate, 
smooth skin                           1"                                   7.20

polystyrnene
bead board                            1"                                   3.85
smooth skin extruded              1"                                   5.00

If you don't own Pocket Ref, get one.

[Nevada]

Originally Posted by huisjen

I'd feel more secure if I used somthing more solid, like 1/4" chipboard, under the insulation. I noticed in Nevada's house pictures that that's what he's got (or somthing very similar) supporting and protecting his floor insulation.

True. I used 1/2" OSB under my floor insulation, but in all fairness I had 2x6s to attach it to. To do something similar to what I did Cyngbaeld will need to build a frame (a 2x4 frame for R-13), which would be quite an undertaking. There should be an easier way to winterize a mobile home.

[billco]

I actually used this product on my renovation of my 2nd floor. My walls had what I am assuming was less then r 9 prior to renovation. I combined it with R12 unfaced insulation in the walls and R30 in the attic. This is a cape house, and it was VERY susceptible to swings in temperature. The contractor who I worked with (he was going for the certified Green status in CT), and I sat down. Based on all product material, the R12 + FBBF is the equivalent of R20 standard insulation.

1 tip though!!! if you use this- make sure to put furring strips on top of the tekfoil. This gets you the seperation you need to avoid the thermal transfer and makes it easier to detect the "points to secure" sheet rock too.