Calling all wallies, Radiant Insulation

Scott Gregg

HR gave a great example in another thread on dusting of reflective insulation. I like the real world example better. It looks like hypothesis + guess = BS! At least to some extent. I too would love to know to what degree a dusting would effect the reflective properties.

I have a seen study or two showing how having a reflective barrier helps in reaction time and even keeping out solar gains used as roof insulation. I'll have to try to find them again.

In re-thinking this I came up with more questions than answers. (This should make a certain someone mad :-)

Q. I wonder how long it would take for dusting to build up to a point where it was as non-reflective as kraft paper? (Seems like it would always be better)

Q. I wonder if there is relationship between subfloor construction and dusting?

Q. If you are using OSB T & G glued to joists/TGI's will there be less convective currents and less dusting?

Q. If you use a reflective barrier insulation against the tubing (5/8" air space instead of 2" airspace) will there be less dusting? (Just saw a study on that one but for reaction not dusting. It was VERY interesting reading.)

I am convinced that reflective foam insulation is a better mousetrap than fiberglass, but these questions do deserve answers.

HR et all, I'm all ears...er...eyes. What do you think?

hr

Which system

are you talking about specficaly when you mention the need for reflective insulation?

Is this a staple up application, tube stapled directly to the subfloor?

hot rod

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Scott Gregg

Yes,

both with or without plates. from what I have read, both would benefit with faster warm up times.

rb_8

FTC on Insulation

Some past info of interest:

Press Release:RIMA Works To Address False Claims

"In 2004, the Federal Trade Commission distributed letters to several companies in the reflective insulation and radiant barrier industries alerting them that they are reviewing marketing materials on the industry to see whether they comply with the requirements of the FTC's Rule for Labeling and Advertising of Home Insulation R-value Rule (16 D.F.R. Part 460) and alerting them to the penalties for violations of the rule. In a press release, the Reflective Insulation Manufacturers Association says it was in full support of this action taken by the FTC and began in its own efforts to address the problem.

RIMA says it distributed letters to all association members informing them of the penalties and regulations. Other non-member companies that were in clear violation were contacted as well. RIMA wants to make sure every effort is being made to ensure consumers and businesses utilizing these materials are aware of the true value and benefits of these products.

The FTC welcomed RIMA's efforts and a copy of their letter to RIMA is availabel for viewing on the RIMA Web site (www.rima.net). For more information, contact RIMA at (800) 279-4123 or rima@rima.net."
____________________________________________________

see comments on reflective foil from this document:

Part III
Federal Trade
Commission
16 CFR Part 460
Labeling and Advertising of Home
Insulation: Trade Regulation Rule;
Proposed Rule

FTC, Labeling and Advertising of Home Insulation

The dust in the attached photo below...make note of tube...is after one year. (by the way this is someones idea of a radiant floor installation...another story for another time...)


From the ASHRAE Files:

3786 -- A Model of the Effect of Dust on the Emissivity of Radiant Barriers

A model of the radiant heat transfer in attics containing dusty radiant barriers was developed. The geometrical model was a triangular enclosure in which the temperatures of the enclosing surfaces were known. The dust particles were simulated as areas of equal diameter with an emissivity of 0.85. Several shape factors were calculated using shape factor algebra, including a procedure to find the shape factor between a small rectangle and a triangular surface perpendicular to the rectangular plane. The thermal model was developed using the net radiation method where the net heat exchange between the surfaces surrounding the enclosure was found by solving a system of equations that had as many equations as the number of surfaces. A large system of equations had to be solved to account for the dust particles in a representative sample. The solution of the system of equations provided the heat flux for each element of the enclosure. Finally, replacing the radiant barrier and the dust particles for an equivalent surface corresponding to the dusty radiant barrier provided the means to estimate the emissivity of a dusty radiant barrier. The theoretical model was tested to asses its validity. Experimentation was carried out using a reflection emissometer to measure the increase of the emissivity of an aluminium radiant barrier when known quantities of dust were artificially applied to it. The experimental results showed good agreement with the theoretical model. The effective emissivity exhibited a linear relationship with dust coverage. This simple relationship was consistent with previous findings and can be used in determining effective emissivity with more sophisticated models to simulate the random location of random-size dust particles over the radiant barrier.
KEYWORDS: aluminium, foils, dust, particles, emissivity, calculating, heat flow, temperature, performance, experiment

AUTHORS: Noboa, H., O'Neal, D., Turner, W.D.
CITATION: ASHRAE Trans. 1994, Vol.100, Part 2, Paper number 3786, 23-30, 9 figs., refs.
PUBLISH DATE: 1994

3410 -- Measured Effects of Dust on the Performance of Radiant Barriers Installed on Top of Attic Insulation

The effect of dust accumulation on horizontal radiant barriers (HRB) was studied by a national laboratory in three research houses near Oak Ridge, Tennessee. Tests on dusted HRBs showed that a lighter loading (0.34 cm/cm^2) increased total house cooling load compared to a clean HRB by 2.3% and a heavier dusting loading (0.74 mg/cm^2) increased house cooling load by 8.4% compared to a clean HRB. However, horizontal radiant barriers with these dust loadings still decreased house cooling loads by 7% compared to the same house with no radiant barrier.
Key words: building envelope, insulation, residential building.


AUTHORS: Levins, W. R., Hall, J. A.
CITATION: ASHRAE Trans. 1990, vol. 96, part 2, paper number 3410, 253-260, 10 figs, 10 tabs, refs.
PUBLISH DATE: 1990

You can order these and others directly from ASHRAE for $15.

Cheers,

RB

hr

Dust, heat transfer, yellow paint, what it all means

I'm not sure I can answer the dust questions. Some dust comes with the product, some comes with shipping, some comes when a sheet of subfloor is cut and installed.

I believe most comes from the basic act of construction and related clean up. As I mentioned the dust I wiped off sure looked like dust from sheetrock installation and clean up.

I did a little demo to see exactly the contact patch of EPDM stapled against 3/4 plywood. I painted the tube yellow with thick paint

Stapled it per the manufactures direction and waited. Several hours later I checked out the demo. Out of 21" of tube 7" never touched the subfloor. I suspect with water added and heated to 140 or so, more gap would appear.

So I really not buying the "dramatically improved thermal transfer the article below alluded to. I never could get the tube to flatten against the floor, even when hammered till the tube egged out??

In fact this confirms my infared comparison between the various methods. Really suspended tube showed a similar transfer to EPDM staple up. With the exception of the heat transfer staples Yes it did have a clean aluminum, unprinted surface below it!

Now compare the aluminum transfer plate application running all the same flow, temperature, etc.

It's pretty clear which method provides the best transfer.

Do any of the pex or PAP manufactures actually approve of stapling their tube tightly to the bottom of a subfloor? Seems thermal movement would wear at the staples, or at least be a noise generator. Pex moves a lot. I would say Onix is the only product built with that installation method in mind. If direct staple up is you choice, use that product.

The key to heating the space is getting the floor surface temperature warmer than the room.

There are plenty of methods and products that will accomplish this goal.

How fast, how even, at what supply temperatures, at what cost, are all the choices you and the customer have to work out.

Why not leave dust, or the unkown of it out of the picture altogether? Then you don't have to "wonder if"

Every manufacture I know offers some sort of transfer plate, for below floor installation system in their catalog. Now you have a wide range of insulation options at your disposal.

hot rod

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[Deleted User]

Conductivity is the KING of heat transfer...

why mess around with a lesser method? (Speaking of heat, I feel the flames licking at me now...)

Seriously, I know there are a lot of people on this forum that do nothing BUT staple up or suspended, and so be it. As long as it works for you, and your customers, then let 'er rip.

But for me, and my customers, I prefer to give them THE best method of heat transfer that I can, that being conductivity, not convection.

And when dealing with stricly conduction, i.e. extruded heat transmission plates, it makes aboslutely NO sense to allow convection into the picture. It dilutes the thermal soup.

Personally, I have been to other peoples jobs where staple up had been done and would not cut the mustard. Upon further investigation, I found that no aluminm faced insulation had been used, just kraft paper. More importantly, there was NO air gap between the Entran 2 and the sub floor. I had my guys go into the crawl space and pull the insulation back to give an air gap and WHAM, heat started SCREAMING from the floor. Actually had to turn it down....

Still not convinced are you...

To each is own.

ME