Seal it Tight and Ventilate it Right
Understanding air sealing and ventilation requirements in SIP structures
Structural Insulated Panels (SIPS) can help create a tight, energy-efficient building envelope for commercial and residential structures. By incorporating continuous insulation and ensuring tight joint lines, SIP buildings minimize the potential for air leaks, and as a result, are 15 times more airtight than stick framing with fiberglass batt insulation.
While minimizing air leaks is crucial for energy-efficiency, in ultra-tight SIP buildings, proper mechanical ventilation is required to create a safe, comfortable, and healthy environment for building occupants. Understanding the proper sealing and ventilation requirements for SIP structures is imperative to create a highly efficient and comfortable building.
Seal it with a SIP
Traditional stick construction with studs, joists and numerous other framing members is notoriously difficult to seal. Alternatively, SIPs come in large units comprised of oriented strandboard (OSB) and expanded polystyrene (EPS) foam, so result in far fewer gaps to seal. The Building Science Corporation explains, “Both OSB and EPS foam are air impermeable so there is no air leakage through the center of the SIP panels.”
SIPs are built-to-order, delivered to jobsites as whole panels, and installed in puzzle piece fashion. When assembled properly, there are far fewer gaps than traditional stick construction and a lower potential for air leakage. In order to maximize energy efficiency, project plans should incorporate effective SIP sealing practice. While builders should consult local codes and manufacturers for the most accurate requirements, some common SIP sealing methods include:
- Sealant – Sealing foam-to-foam, wood-to-foam, and wood-to wood interfaces
- Expanding Foam: High expanding foam for use in junctions and hollows at the edges of structural elements and gaps (also known as voids)
- SIP Tape: Wide tape sealer for use over panel joints and corners
A Breath of Fresh Air
In the case of traditional structures, an HVAC system may be overworking to keep up with the energy loss due to air leaking out of the building. Alternatively, the higher-performance SIP structure allows for smaller-size HVAC systems while still providing sufficient fresh air to building occupants.
Identifying a properly-sized HVAC system for SIP is necessary for maximizing energy efficiency. The Structural Insulated Panel Association (SIPA) explains, “…an oversized HVAC system will fail to reach the steady operating rate the equipment was designed for. Short cycling HVAC equipment will be less energy efficient and require more maintenance than properly sized HVAC equipment.”
Ventilation systems commonly found in SIP structures include:
- Heat Recovery Ventilators (HRVs)
- Energy Recovery Insulators (ERVs)
- Ventilating windows
- Exhaust Only Systems
SIP structure ventilation systems and techniques are not unlike those required with other wall and roof systems, the sizing and output requirements may vary but the concepts remain unchanged. Proper ventilation and attention to building comfort are still paramount.
For more information on sealing and ventilating SIPs as well as controlling moisture within the structure, read our article in The Construction Specifier.