letter to the Editor

Ref: January 2010 no.208

In response to your article titled “Energy-Smart Walls”, I feel you did a disservice to such an important subject. More importantly, your review of SIPs leaves the reader with three paragraphs that will undoubtedly discourage the use of a proven energy and resource efficient system. I question the author’s knowledge of SIPs and credibility when he encourages the use of foam that is not used by a single SIP manufacturer in North America. Yes there is a difference between polyisocyanurate (PIR) and polyurethane (PUR). More important, the assertion that PIR (or PUR) is more resource efficient is ignoring the recyclability of the most commonly used SIP core (EPS). The claim of reducing waste by blocking out openings is, in fact, not the “typical” way PUR SIPs are manufactured. The urethane SIP industry is dominated (by volume) with manufacturers who produce blank panels and then cut the panels to size. This form of fabrication is no different in terms of resource efficiency than cutting blank panels on site, and far less so if done with a foam that cannot be recycled.

The author’s regurgitation of the HBCD issue is one that, I imagine, stems from writings by Alex Wilson and his comments in the publication; Environmental Building News. (See also; Mr. Wilson’s continued attacks on the styrene industry on pg 26 of the same issue) The author and Fine Homebuilding would be well served to further investigate these allegations. They are likely to find the facts show that both XPS and EPS are a resourceful product that can vastly improve energy efficiency without harm to humans or the environment.

The author further shows his lack of understanding and/or research by detailing a drawing that shows air sealing on both sides of a SIP wall. First, this detail would violate good building science practice of always allowing a wall assembly to dry in one direction or the other. Second, the industry as a whole does not use PUR as an “Air seal on exterior panel seams”.

I was glad to see the author mentioned air leaks and even described the problem as: “A walls worst enemy”. Unfortunately, he failed to highlight the air infiltration properties of any of the six assemblies discussed. I recognize that air tightness is dependent on proper installation. However, the ability to install SIPs in very large sections with minimum joints and thermal bridging results in much faster completion than the other five assemblies, and easily achieve <1ach@50 without “great care”.

In short, I wish the author had titled his piece, “Five Proven Ways to Build Energy-Smart Walls” and left SIPs out completely. His description of SIPs and the SIP industry is inaccurate, incomplete and shows obvious bias against a wonderful system with proven energy performance in a time when energy conservation is critical to achieving energy independence in America.

Al Cobb
Panelwrights LLC