Choosing SIPs
We engineer energy savings, with significantly lower lifetime heating and cooling costs over traditional construction methods. You will also automatically reduce greenhouse gas emissions and other pollutants while increasing energy performance or comfort. Our SIPs enable faster construction of your insulated weather-tight project enclosure by as much as 55% leading to quicker construction and lower labor costs.
Choosing SIPs
SIPs are an acronym for Structural Insulated Panels and they are what make up the walls and roof that surround your timber frame and create the insulated shell. Although relatively unfamiliar to many, SIPs were actually first developed, tested, and used in the 1930s and have been used successfully in hundreds of thousands of residential and commercial projects since. Physically, a SIP is comprised of two exterior layers (usually some form of plywood) with some form of insulation in between. When properly manufactured and installed, they can form the most energy-efficient structures available in today’s construction world.
Production methods, and subsequent quality levels vary but Woodhouse uses SIPs produced only by the best manufacturers in the United States and ones that we have vetted over many years and work closely with to ensure quality levels and cost competitiveness are maintained.
As you explore the choices available in the world of SIPs, the primary decision you will make is to surround your timber frame with polyurethane panels (PUR) or expanded polystyrene panels (EPS). Both are comprised of an interior and exterior skin formed from oriented-strand board (OSB). Their difference lies in the insulating medium between.
EPS
EPS panels make up the vast majority of SIP installations in the world and are the ones most familiar to architects and contractors. The insulating medium is the white, compressed bead, open-cell type many people know as Styrofoam and it has an insulating value of R3.8 per inch. The manufacturing process is a relatively simple one where the EPS foam core is glued to the interior and exterior skins and then cured within a pneumatic press. Primary quality concerns are the type and control of the gluing process. They come in 6 thicknesses:
4 5/8 inches R15
6 ½ inches R23
8 ¼ inches R29
10 ¼ inches R37
12 ¼ inches R45
15 inches R55
EPS panels are supplied up to 8-feet wide by up to 24-feet long. They are always pre-cut to your design (wall lengths, window and door openings, roof sections and angles, etc.) on precision CNC machinery. Advantages to using EPS panels include a lower cost per square foot of panel, a lighter panel, recyclability (for in-factory scrap), and larger size availability.
PUR
PUR panels are much less common than EPS panels and there are far fewer manufacturers available but they comprise the vast majority of Woodhouse installations due to their inherent and easily recognized advantages (for instance, in 2022, they comprised 100% of Woodhouse installations and in 2021 they comprised 93%). The insulating medium is a dense, rigid, strong, yellow, closed-celled polyurethane similar to the polyisocyanurate boards available at big box stores with an insulation value of R7.0 per inch. The manufacturing process is more complex than that of EPS and involves spraying two chemicals together at high pressure to create an expanding foam that fills a jig with the OSB skins attached on either side and is then cured within a hydraulic press to withstand the forces resulting from high pressure on a relatively large area. Primary quality concerns are the potential for voids within the panel. This is accommodated for and controlled by manufacturing processes that can be explained by your Woodhouse RPM. They come in 3 thicknesses:
4 5/8 inches R27
5 5/8 inches R34
6 5/8 inches R41
PUR panels are supplied in sizes up to 4-feet wide and 24-feet long. They are always pre-cut to your design (wall lengths, window and door openings, roof sections and angles, etc.) on precision CNC machinery. Advantages include higher R-value per inch which allows for smaller roof fascia and extension jambs as well as the strong probability of shipping cost reduction. Their tongue-and-groove design as well as the ability to form mechanical fasteners within the foam reduces installation time by about 33% vs. EPS panels. In general, the result is a superior insulated envelope at the same or less cost than EPS
