Introduction: Anderson Sustainable Architecture Blog
In Passive House construction, typical construction materials and components are used with the location, quantity of material and quality of installation being the larger construction changes.
• Insulation thicknesses are provided based on the climate. You wear a parka in cold winters when you wouldn't want a light spring jacket. Insulation properties vary and it is critical put the right material in the right place. Insulation can be one of the least expensive, highest financial returning and least CO2 producing energy saving investment you can make.
• A great Air, Vapor and Weather Barrier improvement has been placing barrier membranes where they are not penetrated by building trades. Where membranes absolutely have to be penetrated, such as at building electric and water service, the joints are taped and sealed. Six quarts of water can enter building cavities through a one square inch opening, and thats not a big opening when you consider the area of walls and roofs and the number of outlets, etc... that typically get poked through barriers. Keeping vapor membranes warm to avoid condensation has been another great building durabilty advancement. If a vapor barrier is below dewpoint any water vapor will condense on it before it permeates it. This condensation can lead to mold and construction damage.
• Passive House quality windows and doors are typically triple-pane with warm edge glass spacers and high-performance insulating frames. Based on area, a lot more energy is lost through windows and doors than walls. Glazed windows and doors make up for this by allowing light and heat energy to enter the house and then keeping the heat in. In summer, they keep the house cooler than traditional units. You can stand next to a Passive House window when it is 20 below outside and be comfortable. This adds usable comfortable space to your building. Passive House quality windows and doors are an investment, but the rewards are energy savings and building comfort. You really appreciate the quality of these advanced units when you open and close them. They have a smooth, solid feel that hasn't been experienced in America until now. Passive House quality windows and doors have been made and used in Europe for decades, but American and Canadian manufacturers are making inroads into the market.
• Energy-efficient energy recovery ventilators, appliances, lighting and building controls decrease building electric loads and their waste heat and moisture. Heat Recovery Ventilators were invented in the 50's, have minimal working parts and have provided steady service. Energy Recovery Ventilators are similar to Heat Recovery Ventilators, but they also repurpose moisture in the air, which is important in hot-humid climates like Midwestern summers. Equipment advancements are continuing to increase savings.
• The design of foundations is very important in Passive House quality buildings. Concrete foundations are a source of heat loss and water vapor intrusion in buildings. Concrete materials naturally wick heat and moisture. The earth around building foundations is typically 50-55 degrees and 98% humidity year round, except for the top 3-5 feet frozen in winter. Buildings maintain interior air temperatures of 68-72 degrees and humidity levels of 20-50%. Given that heat and moisture move from high to low concentrations, there is a constant wicking of heat and moisture through concrete footings and foundations and heat through slabs with only a vapor retarder separating them from soils. This is why basements are cool and humid enough for mold growth even with a dehumidifier running 24/7/365. You can't possibly dry out or warm up the mass of the earth to stop or slow transport. Passive House design minimizes the vapor drive by adding a vapor barrier or waterproofing at footings and foundations and keeping the vapor barrier below slabs as seen in standard construction. Taped joints are added to make the slab membrane continuous with the footing and foundation membrane. Passive House designs decrease concrete heat loss by adding load bearing insulation around and below footings, foundations and slabs on grade. The loading bearing insulation installed won't compress because it is selected to withstand the loads of the building. Similar loading bearing insulations have been used below bridge abutments and commercial aircraft runways for a long time where the insualtion is subject to far greater loads and repetitive impact.
Education, advocacy, learning and milestones.
Mark Anderson, AIA, CPHC
For my day job, I'm an architect focused on green design. Not a bad gig! Caring for the planet is a theme throughout my life. This page is where I like to talk about how that love for the earth plays out – in architecture and in my life.
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