Page 16 - GB Building Science Ebook 2019

02 SIX CHANGES

NEW INSULATION

AND THERMAL

BRIDGING TOOLS

Stricter codes and market expectations are pushing all wall

systems toward net-zero energy. The question is simply which

combination suits your budget and labor force.

E KNOW A lot more about how air sealing innovative approaches to improving envelope performance--ranging
affects building performance than we did from spray-on weather barriers to expanding spray foam to airborne,
20 years ago. For example, we know that pressure driven particles that fill the many tiny air leaks in a typical
moisture in wall cavities reduces insulation structure.
performance, and air movement can make
Winsulation 40 percent less effective. GOAL ZERO
We also know more about how insulation performs under various One of the background forces driving innovation in wall systems is
conditions. And this new knowledge has resulted in many new, fast-approaching age of zero-net energy homes. It’s not as distant a

Invisible Gains. If you look at code requirements for attic insulation in cold climates, you may wonder, if the R-value of
insulation shows diminishing returns past about R-19 thickness, why keep going? The answer—to break the thermal
heat transfer between attic space and ceiling through the wood ceiling joists.

*Recommended Dept. of Energy attic insulation for commonaly used fiberglass, mineral wool, and cellulose insulation assuming about R-3 per inch.
** Standard joists are sold as 2’x8’ but actually meausre closer to 1.5’x7’.

16 BUILDING SCIENCE SPECIAL REPORT: SIX WAYS CONSTRUCTION IS CHANGING