Frequently Asked Questions

How much does a SIP weigh?

A 4 x 8 x 4½” SIP weighs about 100 lbs.

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Are the panels structural?

Yes. And tests indicate Thermapan SIPs are significantly stronger than conventional 2×4 or 2×6 walls.In fact, houses built with Thermapan SIPs have withstood the force of Class 6 hurricanes, such as Andrew, Hugo and Mitch.

What is the R-Value of a SIP?

The real-time R-Value of a SIP depends on its thickness and environmental factors.

Isn’t there still thermal bridging at point load columns in a SIP wall?

Point loads constructed from lumber are not a true thermal bridge. Wood is a decent insulator, albeit not nearly as good as the insulation used in SIPs.  As a whole, SIP walls far exceed building code effective R-Value requirements, even after accounting for point loads.

Building code packages that call for a layer of continuous insulation on the exterior of traditional stud & batt framing are designed in order to reduce the possibility of a dew point (condensation) forming inside the wall cavity – which can lead to mould growth.   This won’t happen with SIP systems, because there is no wall cavity and the layer of EPS insulation is closed-cell, i.e. rigid.

Consider that R-19 + “5 ci” nominal code standard (OBC Package A-2) translates to an effective R-20.32.  4.5” SIPs deliver an effective R-22.7, as a single component, with much enhanced air-tightness among many other benefits.

Do SIPs come pre-framed with windows and doors?

No. Thermapan SIPs use a standard system that makes them easy to assemble and extremely cost effective. One of the key benefits of the Thermapan system is its design flexibility. SIPs can work with any number of window and door combinations. Thermapan’s reference manual also makes the installation of windows and doors straightforward and simple. View the Door & Window Openings segment of our Installation Video and see how easy it really is.

What tools do I need to install SIPs?

You will need regular carpentry tools plus a hot knife and expanding foam. A hot knife is a tool for holing out grooves in the EPS, and is needed whenever SIPs must be cut to size. Hot knives are easy to use and can be purchased or rented from Thermapan. Expanding foam is used to seal all connections between individual SIPs and top and bottom plates thus ensuring the structural integrity of the system. For a full list of SIP tools that Thermapan can supply, visit our Accessories page.

How do you install electrical?

Thermapan SIPs are both simple and easy for electricians to wire. Visit our Installation Photos page for some detailed shots of electrical installation and to watch our Electrical Installation Movie.

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What is the fire rating of a SIP?

With 1/2″ gypsum board, SIPs have a 15-minute fire rating which meet residential fire code regulations. Thermapan SIPs also meet the National Building Code of Canada. As with any fire resistance issue, however, requirements vary by region, occupancy and building classification. You should contact your local building or fire departments to determine the necessary requirements and ensure compliance with local fire codes.

Do SIPs contain formaldehyde?

The answer to this question is while technically yes, effectively they do not. This is because the amount of formaldehyde emitted by the oriented strand board (OSB) used in SIPs is less than 0.1 PPM (parts per million). This is well below accepted levels established by the U.S. Department of Housing and Urban Development (HUD). Additional details and test results can be found in this Technical Document.

The additions to my parent's place is all post and beam and SIPs. They've been holding up well for over a decade. I don't know the R values, but the roof panels are 8" thick, wall panels are 6" thick, and floor panels (where they used them) are 4" thick. My folks turned a ~2200 Sq Ft '50s cinder block house into a ~8000 Sq Ft house by building above and to 3 sides of the existing house. All of the additions are SIPs and pine beams.

My folks bought 20 acres of 30 year old pine and partnered with a small, local, wood mill to fall the trees mill the beams and some of the finish lumber. Dad used a place in northeast AR to laser all the 1/4" steel brackets for putting the giant erector set together. Most of the work was done by dad, family, and me, dad hired plumbers, electricians, stone layers, etc. but the structure was all us and a few hired laborers.

Most of it was handled with farm equipment we already had, dad's got a Swinger front end loader, but he did lease a giant New Holand telehandler for about a month, and the tall stuff required a crane.

SIPs went together simple enough, the foam is the same thickness as standard lumber, i.e. 4" foam is the same thickness as a 2x4 is wide. Dad had some electric "branding irons" similar to electric charcoal starters, one for each thickness of panel he was using. The branding irons had guards on them that could be set at various depths, so you set the depth, then "cut" the foam from the edge forming a groove that allows you to fit lumber in. Sandwiching lumber back to back allowed you to fit panels edge to edge, kind of like giant tongue and groove panels. There were a lot of really long screws used too.

The roof SIPs panels were felted with tar paper, and corrugated steel roofing was attached directly to them.

That's most of what I remember, if you have any more specific questions, I can try to answer, or at least ask dad. I know I have some finished pictures, but I might have some during construction pictures too, if you're interested I can see what I can dig up.