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Oliver Style: Airtightness and Moisture Control for Retrofits

Oliver Style holds many titles: director of Praxis Resilient Buildings, a Passive House consultant, and a component certifier. Oliver dove into moisture control and airtightness challenges in the EnerPHit of Monestir, a historic multifamily building in Barcelona, originally constructed with solid brick walls and an artificial stone façade. This project posed serious challenges ensuring airtightness and moisture control to meet Passive House standards, especially given that traditional Spanish buildings are often more than ten times as leaky as needed to meet Passive House requirements. In Oliver’s words meeting Passive House airtightness requirements is “key, a big challenge… but achievable”. 

The necessary approach became clear quickly. With the solid brick and artificial stone walls, adding insulation to the exterior would not be easy, so the building would need to be insulated internally. Of course, retrofitting from the interior posed its own problems, as standard vapor barrier and insulation methods run the risk of condensation and mold growth buildup because the brick exterior can act like a sponge when it rains. To combat this, the outside faces of the brick walls were treated with a brick cream, a water repellant. A capillary active vapor strategy was used along with the brick cream to control water absorption. For airtightness, the floors were coated with a liquid membrane, while the walls were sprayed with cellulose insulation. With Passive House-quality windows, the project was ultimately a strong success. The blower door test results on the first three floors were well below the stringent Passive House requirements, while the building’s energy consumption dropped by 37% because of the work, saving approximately €9,255 each year. Watch the video to learn about the details and catch up on the informative Q&A session.

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