These manufactured components simplify the process of making a home more energy efficient.
- Many contractors upgrade existing homes by adding rigid foam and OSB sheathing to the outside. Insulated panels allow the work to be done in one step.
- Air sealing is an essential part of a successful outcome. It will minimize condensation problems later on.
- Retrofit panels are simple to install, once the siding and roofing have been stripped. The work usually requires just two people.
Most people associate Structural Insulated Panels (SIPs) with new construction, but these offsite-manufactured components also come in retrofit versions. Retrofit panels only have OSB sheathing on one side of the foam and are, in fact, non-structural. They’re often referred to as nail-base panels.
How does one get the most from these panels? And what advantages do they offer homeowners and contractors?
The main reason to retrofit a home with panels is to improve energy performance. “Panels create a consistent envelope,” says Damian Pataluna, President of panel manufacturer Fischer SIPs in Louisville, Kentucky. Panels eliminate most of the thermal bridging that happens in framed exterior walls and roofs.
Credit: SIPA
On the Roof
Ted Clifton, Founder and Owner of Clifton View Homes, a general contractor in Coupeville, Washington, has used panels to winterize homes with uninsulated roofs.
“Lots of chalets [in this area] were built as vacation homes,” with little to no roof insulation, he says. Most of those roofs were framed with 4 by beams on 4 ft. centers, topped with 1½-in. thick tongue and groove decking. They’re easy to retrofit because panels can be screwed to the decking.
In addition, many conventionally framed homes are insulated at the ceiling level with ductwork running through an uninsulated attic. “The ducts are exposed to extreme attic temperatures, so energy is wasted,” Clifton says. Adding panels to the roof will minimize the loss of heated or cooled air by keeping the ductwork at room temperature. Panels are screwed into the top chords of the trusses, through the sheathing.
Wall Retrofits
Wall panels are also fastened to the exterior of the home. Although it’s possible to put them on the interior, Pataluna has never seen it done. “That would create a lot of upheaval [in the living spaces], and the home would lose some square footage,” he says. “On the exterior you just have to remove siding. It’s not as invasive.”
There are circumstances where a homeowner might opt for interior panels. Pataluna says that might include “an historic home where you want to preserve the exterior.”
Of course, this work can be, and often is, done without panels by installing exterior insulation board followed by OSB or plywood sheathing. This is less time efficient because the carpenters have to go around the house twice. “With panels you’re installing insulation and [sheathing] in one step,” says Pataluna.
There usually ends up being a half-inch wide gap at the top of each wall panel, under the roof. This needs to be sealed with expanding foam.
There will also be exposed foam at the bottom of the panel. A guidebook published by the Structural Insulated Panel Association (SIPA), called Retrofit with RIP Insulated Wall & Roof Panels, specifies that flashing be installed in this location and that the bottoms of panels be “at least 8 inches above grade, as with any wood product.”
Credit: SIPA
Windows and Doors
Panels make existing walls thicker. Pataluna says that on most of these jobs, the homeowners also opt for new, more energy-efficient windows. Typically, new windows are installed on the exterior, mounted flush with the OSB surface of the panel. This creates deep window wells that need to be trimmed. “Some people use them as a plant shelves,” Pataluna adds.
Sometimes the existing windows are good enough to be retained. In that case, according to the SIPA guidebook, the windows are usually removed and remounted at the exterior of the panel. If they can’t be easily removed and reinstalled, they can be left in place and jamb extensions are installed on the exterior.
Credit: SIPA
Cutting Panels
When a new home is built with SIPs, the exact wall and roof dimensions are in the plans. So, it makes sense to accurately pre-cut panels on CNC machines in the factory.
With a retrofit, however, the reality is different. Clifton says, “Older homes tend not to be straight and square, because the ground has settled a bit.” The home may also have been altered during its life. “So, we typically buy stock sizes of panels and cut them on-site.”
Retrofit panels are easy to cut, according to Pataluna. “A circular saw is all you need.”
How to Fasten
Obviously, screws must be long enough to go through each panel and into the underlying structure. “I’ve seen installations where the studs have been missed half the time,” says Pataluna. “That means the panels aren’t attached as securely as they should be.”
Fastener patterns vary between 12 in. and 24 in. It depends on the weight of the cladding that will be installed — vinyl, wood, or fiber cement, for example.
Clifton says, “You probably won’t find the right screws at The Home Depot, but there are brands — such as TruFast — that you can order directly from the company or find at local distributors.” Fasteners also might be supplied with the panel package.
Credit: Ted Clifton
Plugging Seams
An insulated panel system “is designed to be super airtight,” says Pataluna. Where panels meet, everything needs to be caulked and taped, sealed up tight.” A commonly used product, according to the SIPA guidebook, is low-expansion, closed cell, spray polyurethane foam.
If sealing isn’t done properly, air can move between the panels. Clifton explains that moisture in this air could “condense on the outside of the OSB, which can freeze in winter and blow the product apart.”
Where caulk is needed, it’s important to use the right the type. Common solvent-based construction adhesives shouldn’t be used. “It’s best to use the caulk from the SIP manufacturer,” Clifton advises, “because it’s already been vetted. The wrong caulk can melt a panel’s foam insulation.”
Credit: Ted Clifton
Crew Size
Pataluna says panels aren’t heavy. “A 4×8 ft. panel might weigh 80 pounds, which two workers can easily handle.” He gives the example of a simple, 2,000 sq. ft. box-shaped house. “It shouldn’t take two guys more than 1 1/2 or two days to get all the panels installed and wrapped [with the weather resistant barrier].”
Clifton estimates it would take five days total (including one day for tear off) to retrofit a straightforward, truss gable roof, with typical pitch and height for a two-story, 2000 sq. ft. house. “In addition to a four-person crew, I would need a boom truck for a couple of hours to get the panels lifted up to the roof level and stocked at the ridge,” he says.
Other Advice
Clifton advises that, “On your first panel retrofit, bring on someone with experience for the first day or two to help you.”
Neither Clifton nor Pataluna thought there were many circumstances in which panels wouldn’t be a good choice for a retrofit, compared to conventional methods of upgrading insulation.
Pataluna says, “If a wall has a lot of turns, it will involve more work — more cutting and sealing.” But he points out that replacing insulation and adding sheathing in separate steps would require even more work.
Similarly, Clifton says, “If a roof is very complex, it’s not any easier to do a retrofit with conventional materials.”
The only situation in which panels might not be a good choice for a retrofit is when “the substrate isn’t acceptable for holding the panels in a given environment,” Clifton says. “An example is a building out on the prairies with possible tornadoes, and a sheet metal roof on purlins placed four feet apart.” In such cases, improving the roof is problematic no matter what method is used, Clifton says.
How Much?
It can cost anywhere from $50,000 to $100,000 to retrofit panels to the walls and roof, depending on the home, Clifton says. Homeowners usually can’t get a loan for this work because “better energy efficiency isn’t on appraisers’ radar as something that adds value.”
But for homeowners who can afford the cost, panel retrofits are attractive because they improve energy performance and can be installed quickly. For a builder, they reduce the time and labor needed to complete a job. “If a builder is already doing siding and window replacements or roof replacements, it’s foolish not to also do retrofits with panels,” Clifton says. “It’s a no-brainer.”
Zena Ryder writes about construction and robotics for businesses, magazines, and websites. Find her at zenafreelancewriter.com.
