SIPs, or structural insulated panels, have emerged as one of the most intelligent building systems of the past few decades.
The construction technology isn't exactly new -- First Lady Eleanor Roosevelt dedicated a SIPs building in 1937 -- but a new interest in green building and energy savings has piqued the interest of builders, homeowners and government officials alike.
The Basics of SIPs Building
A SIPs panel is generally 2 to 4 feet wide and about 8 feet long; the thickness ranges from 4 to 12 inches. An inner core of foam -- either polystyrene or polyurethane -- is sandwiched between two outer panels of harder material. Oriented strand board (OSB) is commonly used as an outer panel, though some SIP panels are made of plywood, sheet metal or other material.
SIPs can be used for walls, floors and roofs, making them very versatile and easy for construction crews to work with. Because SIPs are thick and rigid, they're very strong and make the entire construction process faster and simpler than typical wood-frame, stud-and-insulation construction. Roofs, for example, can be constructed without trusses, eliminating the time and expense associated with the typical roof.
There are a few drawbacks to SIP construction. Because of the size and weight of larger SIPs panels, a crane may be needed to lower the panels into place. And the OSB used in SIPs panels shouldn't ever get wet -- if it does, it tends to hold water longer than plywood, giving mold and mildew an ideal environment to grow.
Many people have expressed concerns about the formaldehyde used in OSB, and for good reason -- formaldehyde is widely acknowledged to cause cancer. But there's a difference between urea-formaldehyde (commonly used in particleboard cabinets, shelving and other items) and the phenol-formaldehyde used in OSB and plywood. Urea-formaldehyde contains more toxins and off-gasses more readily than the safer phenol-formaldehyde -- most regulatory agencies have accepted OSB and other phenol-formaldehyde products as safe.
Green Building with SIPs
Engineered products like SIPs are gaining ground with construction crews for a number of reasons, including those noted above: They often arrive pre-cut, making the construction process much faster. SIPs readily accommodate plumbing, electrical and other conduits. And they're usually straight and true -- unlike lumber studs -- making it easier to form an airtight seal in a building envelope.
From a green-building perspective, SIPs have many advantages, including waste reduction. When SIPs are pre-cut and delivered ready to install, they can significantly reduce jobsite waste. According to manufacturer Premier SIPs: "...SIPs panels reduces the amount of jobsite material waste by 60 percent when compared to buildings constructed with regular dimensional lumber and framing materials. Less waste is obviously better for our environment."
Perhaps the most obvious green benefit from using SIPs panels is their superior insulation value, or R-value. A 4-inch SIP panel has an R-value of about 15; a 6-inch panel has an R-value closer to 23. And because SIPs panels have no internal studs, there's none of the thermal bridging that depletes the insulation value of stud-and-insulation walls. Over the lifetime of a building, these enhanced R-values will result in energy savings between 40 and 50 percent -- an immense savings in energy and energy costs.
Another attraction to green building owners is the range of tax rebates and other incentives available when using SIPs or other energy-saving technologies. These vary from state to state and city to city: A comprehensive listing is available from the Department of Energy.
The Cost Benefits of SIPs
Like many newer technologies (including ICF or insulated concrete form construction), SIPs panels have a slightly higher up-front cost. Depending on the area, SIPs panels can cost 5 to 20 percent more than traditional stud framing. What this cost increase ignores, however, are the lower costs immediately realized through SIPs construction.
With SIPs, there's no need to buy and install insulation -- they're already insulated. Pre-cut SIPs eliminate the need for much of the framing labor involved in stud construction. Jobsite waste removal costs are reduced, and smaller, less-expensive HVAC units can be purchased. And most SIPs manufacturers offer a warranty, unlike lumber companies.
When all these factors are combined with SIPs' long-term energy savings, it's clear that structural insulated panels offer dozens of smart, cost-conscious, green advantages over typical wood-frame construction. For more information on SIPs, visit the website of the Structural Insulated Panel Association.