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" www.heatshieldr20.com 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, www.Radiosity.biz 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 psi 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
DrBillPE@yahoo.com