The United States has approximately 125 million occupied housing units, many of which are old and lack adequate insulation. These buildings often leak air through wall cavities and rely on outdated mechanical systems that struggle to maintain a comfortable temperature.
According to Jonathan Smegal, an engineer with RDH Building Science, there’s a massive market for deep energy efficient practices, which involve adding insulation and making buildings more energy efficient.
Smegal has spent years studying how to improve the performance of existing buildings. He recommends wrapping continuous insulation around the outside of a building, which eliminates thermal bridging and reduces condensation risk.
This approach also provides an opportunity to upgrade the system when cladding needs to be replaced, rather than just patching it up. The incremental cost of adding exterior insulation is lower when the cladding is already being replaced.
Smegal’s mentor, Dr. John Straube, notes that in Canada, people wear their parkas on the outside, not on the inside, highlighting the benefits of exterior insulation.
One of the underappreciated benefits of exterior insulation retrofits is the improvement in airtightness. When the cladding is removed, a clean surface is exposed, allowing for the application of a continuous air and water barrier membrane.
The Kestrel Court units, which were part of a study on exterior insulation retrofits, showed a 70% reduction in air leakage after the retrofit.
The study tested five different insulation systems, including those from Owens Corning, Dryvit, and Rockwool. The results showed that all five systems met the target airtightness levels and net-zero-ready energy targets.
Smegal notes that the key to a successful retrofit is to minimize the number of passes around the building and keep each layer’s function clear and singular.
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They prefer a system with the least number of layers possible, such as board foam insulation with strapping and an air and water barrier.
The EIFS system used by Dryvit is an example of a system that perfectly fixes the problem at hand. It applies foam directly over the existing brick, eliminating the need to knock down the masonry and reducing waste.
Regulatory pressure to adopt energy-efficient practices is building, with cities imposing carbon fines on non-compliant buildings starting in 2024.
Building professionals are compelled to give homeowners good advice, and the Kestrel Court study demonstrates that exterior insulation retrofits are achievable at scale with available products and installation crews.
They recognize that the technology is not the barrier; the barrier is recognizing the right moment to move, such as when the cladding fails or the heating equipment needs replacing.
According to the report, the variation in system designs and the uniformity of performance show that there are many ways to achieve a desired outcome.
The study examined various exterior insulation details specified by five insulation manufacturers, including BASF, which used spray foam, and Plastifab, which used a rigid foam board with an exterior OSB skin.
Smegal and his team provide valuable insights for building professionals and homeowners looking to improve the energy efficiency of their buildings.
