Page 94 - Designing for Zero Carbon-Volume 2_Case Studies of All-Electric Multifamily Residential Buildings

CASE STUDY NO. 4 THE PALO ALTO APARTMENTS
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Isometric of SIPS panel construction for the apartment building. (Courtesy of Premier SIPS)
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Typical SIPS panel detail at outside corner (90°) where panel cladding meets the stucco finish. (Courtesy of RDH Building Science)
Building Envelope – Insulation and Windows
One of the non-traditional building systems used in this project, at least in speculative residential design in California, was the SIPS. This insulated panel system is one type of manufactured building system employed instead of conventional stick-framed structures. It uses manufactured modular panels rather than prefabricated walls to construct the building envelope of large resi- dential structures and therefore were particularly well-suited to the design of this project.
The SIPS approach was seen by the developer as a means of obtaining high insulation values and greater structural shear resistance to earthquake forces, while potentially reducing con- struction time on the site. Because closed-cell foam insulation is used, there is a much higher insulation value per inch compared to conventional fiberglass insulation. Reduced construction time would also result in a lower initial project cost. This turned out to be an ideal solution for the particular size and massing of this project.
The use of the SIPS required coordination among several companies for the proper design, assembly and integration of the building envelope components. Sageleaf Forest actually pro- duced the shop drawings for the SIPS panels, as mentioned above, which were then produced by the SIPS manufacturer.2 The weather-proofing design for the integration of the other building envelope components with the SIPS panels was developed separately by the building science consultant3. This primarily involved the details of the window and door openings, the attachment details of the exterior siding materials and the details at the deck connections.
Building Envelope – Airtightness
A SIPS structure is naturally airtight because of the large integral panels with airtight connec- tions and the extra attention given to wall penetrations. The gaps between the large panels are sealed with a manufacturer-provided sealant. Silicone liquid-applied membrane was used as the weather-resistant barrier to seal the entire construction rather than a conventional building wrap. This type of air and moisture barrier is generally superior for increasing the airtightness of the completed structure because of its lower permeability.
The developer relied on the superior characteristics of these building components and did not perform a blower-door test to determine for each apartment unit the actual number of air chang- es per hour at 50 pascals of pressure (ACH50)4.
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Designing for Zero Carbon: Volume 2
2 Premier SIPS, Puyallup, WA
3 RDH Building Science, Seattle, WA
4 See the table for benchmarks of airtightness in Zero Net Energy Case Study Homes, Vol. 1, (2018), p. 12.