May 2020 Focus Section
By Beverly Smirnis
It can’t be an afterthought. Every component of a structure’s envelope must be designed and engineered to fit together like puzzle pieces with special attention paid to properly seal penetrations and provide thermal protection. And it’s not just air that you’re fighting to keep out. Just like air, water will also find any way it can to get into a home. Once inside, air and water infiltration consume energy, compromise air quality and personal comfort and threaten the entire structural integrity of the home.
Our industry’s knowledge and understanding of building science combined with powerful energy modeling software and the continuous introduction of innovations arm us with better problem-solving solutions than ever before, yet the U.S. Department of Energy (DOE) still says the average U.S. home still has a half mile of gaps and cracks! One major culprit is the fact that in a typical code-built home, insulation is only placed between the studs — meaning one-quarter of the wall is left uninsulated.
Continuous exterior insulation can reduce energy loss through the walls by providing a solid layer of insulation that covers the entire wall, including the wood framing. In hot, humid climates (including most of North, Central and South Texas) where moisture flows from outside to inside most of the year, energy analysts contend that the mild, short winters generally do not cause enough moisture flow in the opposite direction to cause problems. LSU’s AgCenter says the ideal assembly of a frame wall in a hot humid environment should keep the interior side fully permeable and implement both an air barrier and water vapor retarder on the exterior side to minimize the entry of outside water vapor. The recommended wall assembly is a continuous barrier with unfaced insulation in the wall cavity backed by sealed foam sheathing or sealed low-perm housewrap between it and the wood sheathing.
In attics, proper ridge soffit ventilation ushers moisture out and reduces ceiling temperatures. Adding a radiant barrier like LP® TechShield® Radiant Barrier Sheathing will dramatically reduce radiant heat transfer from the underside of the roof to the attic. Patented VaporVents™ technology with post-lamination incising allows the TechShield panels to dry quickly from moisture that may accumulate during construction and allows for continued moisture evaporation after installation. But some energy experts argue that it’s better to seal and insulate our attics in the hot, humid climate, making attics part of the conditioned space. The IRC code now allows unvented roof assemblies if there’s no vapor retarder between the attic and the home’s living space and air-impermeable insulation is installed between the rafters.
So what are the right puzzle pieces you ask? Well, for the unfaced insulation recommended by LSU, you might consider that today’s fiberglass can achieve R-values ranging from R-11 to R-38, and many products are now completely formaldehyde-free. Cellulose can achieve similar R-values and is a very environmentally friendly material made from recycled paper. Blown-in fiberglass or cellulose can answer to the “gap” issue and be used like low-density open-cell spray applied polyurethane foam insulation (SPF) to effectively fill hard-to-reach cavities and corners. The ability to expand so much after it is applied makes open cell foam an excellent gap-filler and the foam works as its own air barrier, qualifying it for use in unvented attics; but open cell foam is ineffective against penetration by water vapor, so it would still need to be paired with a vapor retarder. Medium-density closed-cell foam acts as an air barrier and also functions as its own Class II vapor retarder, making it an all-in-one choice.
Rather than try to piece together the best solution themselves, most builders rely on the industry giants to provide the comprehensive insulating solutions. DuPont Performance Building Solutions (PBS) has announced a new 10-year product and labor warranty for the combined use of its products: Use DuPont™ Styrofoam™ Brand XPS rigid foam insulation or WEATHERMATE™ Housewrap installed over sheathing, with WEATHERMATE™ Construction Tape used to seal the seams of the blue board for added protection against air infiltration and moisture intrusion. Implement WEATHERMATE™ Flashing and WEATHERMATE™ Sill Pans to mitigate water intrusion around window and door openings.
The ZIP System® is comprised of a structural sheathing panel made of engineered wood, creating a rigid air barrier. It also has a built-in vapor permeable, water-resistive barrier. Assembly at the job site is as easy as installing the panels and taping the seams with ZIP System™ flashing tape with a specially engineered, high performance acrylic adhesive specifically made to bond with ZIP System® panels for a permanent protective seal.
Even when using the latest and best products, oversight remains a requisite to achieving superior performance. Building enclosure components are trending towards modular construction with high performance insulation panels applied in a factory setting to the back of OSB, concrete and other cladding systems. Entekra™ offers a Fully-Integrated Off-Site Solution™ – or (FIOSS™). Wall panels, floor panels, roof trusses and all relevant materials are manufactured under factory-controlled conditions. Structural elements are then off-loaded and assembled by framers with crane assistance for efficiency and safety. The structural shell can be assembled and made weather-tight in an average of three to four days. Ecocor® panels are factory built to the Passive House standard using 100 percent mineral borate treated, fiberized cellulose insulation and air-sealed with advanced, zero-VOC membranes, tapes and adhesives from Europe.
Current construction processes allow the best of intentions to potentially be negated by a number factors. We work in an environment where fewer skilled tradesmen and tighter build schedules often lead to overlooked quality checks, not to mention that job sites are subject to weather conditions. Could this mean that field-installations may soon be the rarity with factory-built wall and roof assemblies becoming the norm? Aristotle said, “The whole is greater than the sum of its parts.” Specialty companies that produces a complete product under factory-controlled conditions are proving to provide a better product, built to a higher quality. Considering time savings and risk mitigation, we may soon say that they come at a lower cost, too.
Beverly Smirnis is the co-founder of Building SAVVY magazine and publishes its flagship Dallas/Fort Worth edition. She and her business partner and husband, Steve Smirnis, have served as judges for the International Builders’ Show Best of IBS Awards, the Greater Houston Builders Association PRISM Awards, the Greater Orlando Builders Association Parade of Homes, and the Building Industry Association of Okaloosa-Walton Counties’ Parade of Homes.