SIPs FAQ

HOW DO I PROPERLY SIZE HVAC EQUIPMENT?

The high insulating properties of SIPs allow smaller HVAC equipment to be used. When working with an HVAC contractor, make sure their calculations take into account an accurate estimation of typically low levels of air infiltration in a SIP home. Proper HVAC sizing is crucial because 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.

HOW IMPORTANT IS VENTILATION?

SIP buildings are extremely airtight and require mechanical ventilation. Ventilation systems bring fresh air into the building in controlled amounts and exhaust moisture laden and stale air to the outside. By limiting air exchange to controlled ventilation systems, SIP homes allow for all incoming air to be filtered for allergens and dehumidified, amounting to better indoor air quality. Proper ventilation is important in all homes to preserve indoor air quality.

HOW DO SIPs IMPROVE INDOOR AIR QUALITY?

The tightness of the SIP building envelope prevents air from gaining access to the interior of the home except in controlled amounts. A controlled indoor environment is both healthy and comfortable. Humidity can be controlled more easily in a SIP home resulting in a home that is more comfortable for occupants and less prone to mold growth and dust mites.

HOW DO SIPs REACT TO FIRE?

Residential building code requires that foam insulation be separated from the interior of the building by a material that remains in place for at least 15 minutes of fire exposure. Structural insulated panels faced with 0.5” gypsum drywall meet this requirement.

Commercial builders may need a one hour fire-rated wall or roof, which is achieved by testing and listing a specific wall or roof assembly to ASTM E119 with an accredited certification agency. Individual SIPA member manufacturers should be contacted to confirm listed assemblies they can provide.

WHAT CONSIDERATIONS DO YOU NEED TO TAKE INTO ACCOUNT WITH BUILDING WITH SIPs VS. CONVENTIONAL FRAMING?

The majority of construction with SIPs is very similar to conventional framing. SIPs accept dimensional lumber and are fastened together using staples, nails or screws. Proper sealing is especially crucial in a SIP structure. All joints need to be sealed with specially designed SIP sealing mastic or low expanding foam sealant, and/or SIP tape. Voids between panels and unused electrical chases need to be filled with low expanding foam. In addition to sealing, planning and consideration needs to be applied to material handling. Although smaller 8- by 4-ft. panels can be set by hand, larger 8- by 24-ft. panels require the use of equipment to unload and set.

CAN SIPs BE MODIFIED ON SITE?

On-site modification can easily be done using a few additional SIP specific tools. Panels can be cut using a beam saw or a beam cutting attachment to a circular saw. The foam core can then be recessed for splines or dimensional lumber using a hot wire foam scoop or specialized angle grinder attachment to recess the core.

HOW ARE ELECTRICAL WIRING AND FIXTURES INSTALLED?

Electrical wires are pulled through precut channels inside the core of the panels called “chases.” Manufacturers cut chases during the manufacturing process according to the electrical design of the home. Electricians can then use fish tape to feed wires through panel chases without compressing the insulation or having to drill through studs. Wiring can also be run through baseboard raceways and in the cavity behind the beveled spacer on SIP roof-to-wall connections.

CAN SIPs BE REPLACED OR REPAIRED IF DAMAGED?

If panels are damaged, a structural engineer needs to assess the damage to determine what is cosmetic and what is structural. If the damage is only cosmetic then the source of moisture must be determined and fixed, whether it is from inside or outside. If the damage is structural, then the source of the problem must be identified and a structural solution to the problem must be found. That can be done by either a site modification of the panels or replacement of the panels, depending on the extent of the damage. In the event that panels are damaged, the manufacturer and installer of the panels should be notified. There are SIPA members who can act as a consultant to assess the damage and recommend repair or replacement strategies.

WHAT ABOUT ROOFING? DOES A BUILDING WITH A SIP ROOF NEED TO BE VENTILATED?

The area inside a SIP building envelope is considered conditioned space and will be ventilated by the building’s HVAC system. There is no need to provide a vented attic beneath a SIP roof, and doing so would compromise the conditioned space of the building. Most roofing manufacturers specify how to attach their product to SIPs. Please contact the roofing manufacturer for application instructions.