Rigid Insulation: Extruded Polystyrene Foam

Continuous Insulation

In an attempt to make homes and buildings more energy efficient and curb heat loss, many contractors and Passive House and Net Zero designers are turning to super-insulating construction techniques. To achieve high effective R-value per inch, a layer of rigid continuous insulation is typically incorporated. Wall strapping, also known as furring is a technique used to connect 2″ rigid insulation, or 4″ rigid insulation, to walls, ceilings, roofs and top side floors. Strapping can be wood strips, metal hat channels and z-bars. Furring materials are installed vertically in line or perpendicular to framing members. To achieve structural integrity, furring strips are fastened through sheathing materials directly to framing members – such as studs, roof rafters, joists, etc. In-turn cladding or other flat-stock materials are attached to the strapping.

However, unless you require the air space created between the rigid foam insulation and sheathing or cladding, strapping is a waste of time, space and money. Consider this seemingly inconsequential detail. Strapping such as 1×3 spruce requires a pilot hole to stop the wood from splitting. Doesn’t seem like a big deal but multiply a few seconds by thousands of pilot holes. Its not just a few seconds or minutes its a few wasted hours.

Rigid Foam Insulation

What if there was a system where 3/4” plywood strapping or steel U Channels were built into the rigid foam insulation panel? There is; its called Quik-Therm T&G Connect – A exterior rigid extruded polystyrene foam insulation product. T&G Connect consists of 3/4” x 2.5” machined plywood furring strips located at 16 inch or 24 inch centers. Connect can also be manufactured with customized steel U Channels.

Let’s compare a typical application that requires 1×4 spruce wood strapping over exterior rigid foam vs. Quik-Therm Connect. Both will be installed 16″ O.C. For standard wood furring applications there are always twisted, cracked or warped boards that are unusable. Then you have to bend down, pick up and measure each piece of strapping. Then you have to cut each individual piece – one by one. This happens hundreds, potentially thousands of times. How much time does that take? And, how much does all that wasted material and labour cost in real dollars.

This is the typical process for conventional furring techniques. For the first 4×8 sheet of rigid foam, the basic application goes more or less like this. Locate the studs and mark locations. Fasten the continuous rigid foam to the wall as necessary to hold it in place. Measure and mark strapping locations on the foam insulation. Measure and cut three 1×4’s to length. One by one, align and fasten the 1×4’s through the rigid foam, directly to the studs. This is what it takes to install Quik-Therm T&G Connect. First of all, there is no warped or twisted strapping or discard. The strapping is machined 3/4″ plywood, built right into the rigid foam insulation. Measure and mark the complete panel once. Cut the furring and insulation in one pass. All in one operation, install the furring and rigid foam insulation board.

For the first sheet of 4×8 Connect, the installation happens like this: Locate first stud in from the corner. Square the Connect panel, aligning the firs plywood furring strip over the first stud in from the corner. The other two furring strips will self align over the neighboring studs. Fasten the panel through the plywood battens directly to all studs.

Working around openings is just as easy. Measure and cut once or twice and install. Installing Quik-Therm Connect at corners is simple and easy, however the thickness of the panel determines the best practice.

Quik-Therm T&G Connect is continuous rigid insulation with a rainscreen and is perfect for screw down and Standing Seam metal roofs. Multiple layers can be stacked and mechanically fastened together; batten to batten either parallel or perpendicular. Just about any configuration can work.

So, how much time and money can be saved by using T&G Connect vs the standard method of attaching strapping? We can’t say for sure; its difficult to come up with dollar amount but a 50% saving in labour is not out of the question. Connect is simpler and easier to handle and transport – the framing and insulation is all together in one package. Measure, cut and install once vs. numerous steps. And there is far less waste. Lastly, Connect has been tested and achieves code compliance as an air, vapour and radon barrier? How many dollars in labour and material could that save? What about the benefits in scheduling and time on site. The list goes on.

Is rigid insulation board waterproof?

Closed-cell spray foam/rigid insulation is 100% completely waterproof!

Is rigid insulation a vapor barrier?

Rigid foam board insulation is generally considered a vapour barrier. Yet, an installation between any studs may present a problem. To ensure a proper seal you will want to foam-seal or tape all the sides where the foam panels meets the wood. It’s these gaps that will facilitate vapour flow.

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