Spray foam is used enthusiastically by many builders hoping to improve energy performance of their projects. But the hidden climate impact of conventional 2-pound, closed- cell foam is actually a huge step backward. A new generation of low global warming potential spray foam corrects this fatal flaw.

Most builders agree that the most affordable wall system is a variation of something they already build. The standard wood-framed wall assembly must evolve to a higher R-value. But how high? What’s the simplest way to get there? 

Zero energy homes need thick layers of insulation, but some materials have serious climate impacts. Identify the key factors that affect the carbon footprint of insulation materials and some good choices for future projects.