Latest Discussions : Tools & Workshop


02:47PM | 09/14/03
Member Since: 09/12/03
4 lifetime posts
As a Professional Engineer I was interested in testing all the claims for Radiant Barriers and Paintable Radiant Barriers, before I installed one in my own home. I tested the following 4 products, 3 paintable radiant barriers and 1 foil barrier over the course of about a year. The foil worked well for the equivalent of the first 2 years on an accelerated testing program. This involved adding dust over the course of 3 months. Effectiveness dropped to 46% for a 5 year period.
The next test was a paintable radiant barrier "Radiance," according to the product MSDS sheet the formulation contains "Formaldehyde" the product tested well but I would not subject my family or employees to this chemical. I also found some of the graphs and charts on their website useless and full of discrepancies.
Next product test was "Heatshield" the website is full of a tremendous amount of misinformation. According to their MSDS the product has a 300 psi crush strength but claim it can be sprayed. We tested using a Graco 795 airless sprayer, with an average operating pressure of 2,571 psi at the tip. A density test was performed, it showed 58% of the glass bubbles were crushed at this pressure. The product worked well when applied by roller, but rated very low when sprayed.
The last product tested was Radiosity 3000, the website is a true presentation of the product (no unsubstantiated space age claims). According to the MSDS the product has a crush strength of 3,000 as the name implies. Same testing was performed as above, using the same Graco airless at an average operating pressure of 2,579 psi at the tip. Doing the same density test 3.2% of the bubbles were crushed. I had a contractor apply Radiosity in my attic this past spring. My summer A/C bills have been 31% lower than the same 4 months last year.
My interior and exterior will be painted next year, after seeing the results I've seen with this product I will have it mixed in with both interior and exterior paint.

William Bonnell Ph.D. PE


12:27PM | 09/17/03
Member Since: 09/11/03
11 lifetime posts
Thanks for the scientific review. I have tried Insuladd,, which is a ceramic based dust. I put it on my walls and ceiling. I think my house is warmer in the winter, but I don't have any data to support that. I was contemplating spraying it on the outside.
My attic has the plywood with a radient barrier on one side. I have added 2 electic exhuast fans, but it still seems very hot up there. I live in San Antonio. I guess this product could be sprayed on to the radiant barrier.
Have you looked into solar exhuast fans?



05:36AM | 09/19/03
Member Since: 09/12/03
4 lifetime posts
Have you done your attic? With any radiant barrier the best application is the attic. This will lower the temperature of the attic, reducing thermal heat gain of the ceiling drywall. I used Radiosity radiant barrier in my attic to achieve my 31% savings. I will obtain more product next year when my painting contractor paints both my interior and exterior.
Painting your exterior with Radiosity is wise, but also doing your attic is very wise. The beauty of this product is, you mix it in with any kind of paint, just visit the website.
William Bonnell Ph.D. PE


07:14AM | 06/15/09
Member Since: 06/14/09
1 lifetime posts
Why go through all the efforts of installing a radiant barrier on the roof deck? This has no effect on the energy use or consumption during the winter. A multi-layered radiant barrier like RBS Chips or Thermal Control Membrane works everyday, winter and summer. It's also impervious to performance degradation from dust accumulation over time and has the lowest measured emissivity: .02

This is why the homeowner in San Antonio is not seeing results. Radiant barrier installed up under the roof deck will actually increase the attic temperature. There is testing of this all over the 'net. Google "radiant barrier testing". He most likely is also using home store attic fans that don't move enough air. Solar fans are even worse which claim "up to" 1250CFM but in reality, at noon, pointed South, best case scenario, actually only move 310CFM. Many anrgy people in Hawaii who have purchased these at a steep price and have seen no benefit.
5058 radiant barrier test

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