Space-Age R-Value: Closed-Cell Polyiso

In a very different arena, carbon emissions have been a target for advanced building enclosure designs, including the continuous insulation (CI) detailing that cuts thermal losses, reduces condensation and eliminates thermal bridges, among other benefits. One of the unexpected materials to attain great prominence in this trend has been rigid polyisocyanurate foam sheathing with a foil facer, a technology adopted in the aerospace industry in the 1960s that became a staple of roof systems and premade ductwork just a decade or two later. The reasons were similar to those that made polyiso perfect for spacecraft: the highest R-value per inch of any common construction material, good fire performance, and a long service life.

“For sustainable design, polyiso is shown in life-cycle studies to be among the least burdensome on future generations in terms of energy savings or carbon emissions reductions, as a recent study by McKinsey showed,” says Jared Blum, president of the polyiso manufacturer group, PIMA – Polyisocyanurate Insulation Manufacturers Association. “For each one unit of energy to produce insulation, the return is 32 to 33 units of energy saved.” This story of durability and return on investment is a lasting dividend of the Space Race, now applied without interruption across the opaque portions of entire building facades.

Photo courtesy of Simontons Windows & Doors

This historic bed and breakfast was retrofitted with airtight, double-glazed replacement windows with an Argon gas fill, low-emissivity (low-E) coatings, and vinyl frame construction that reduces thermal bridging and other through-wall energy loss.

Bridge-Free Frames: Lasting Vinyl for Windows

In a related development, a technique for improving envelope performance with materials that last virtually forever is the use of integrated and exposed vinyl fenestration systems. These include the so-called fusion-welded frames and sashes that create windows with a strong, precision-engineered interlock to the envelope. Several benefits are making vinyl a preferred green spec for fenestration, even as it may raise eyebrows as a choice for other building materials: First, its maintenance needs are negligible, and second, the resulting window and door assemblies have very good thermal properties.

“The airtight seal of many vinyl windows also ensures the occupied spaces are sealed from drafts that increase the need for heating and cooling costs,” says Megan Mazur, a marketing director at Simonton Windows & Doors. “Combined with laminated glass, they offer excellent noise reduction of up to 50 percent—a key feature as acoustics play a greater role in healthy, sustainable design, and new project certifications like the WELL Building Standard.”