Insulate with foam carefully
Poor installation of thermal materials causes its own woes
If you’re thinking about building a new house and doing some research, you may be hearing about SIPs and ICFs, two new building systems that have been gaining popularity. But like everything else, they have their pros and cons.
First, what are they? SIP stands for Structural Insulated Panels and ICFs are Insulated Concrete Forms.
Both are types of panels that have foam insulation. They’re usually used for exterior and foundation walls, sometimes floors and roofs. In fact, I’m building my new garage using an original ICF made from cement and inert wood chips.
But SIPs and ICFs are different.
SIPs have one layer of foam insulation — usually closedcell spray foam — sandwiched between two layers of building material. There are many different types of SIPs out there. Some have corrugated metal, others have galvanized sheet metal. But the most popular kinds have OSB (oriented strand board) or plywood sheathing on both sides of the foam insulation.
ICFs are constructed differently. Instead, they have a layer of concrete sandwiched between two layers of foam insulation, usually EPS (expanded polystyrene). These two panels are connected to each other with plastic connectors or steel ties that hold the foam layers in place. The space in the middle is filled with concrete, making them look like concrete-filled Lego. When pouring the concrete it’s important there aren’t any air pockets. Gaps in the concrete will compromise the structural strength of the entire wall or structure you’re building.
The foam insulation in SIPs and ICFs gives them a high R-value without the need for vapour barrier, depending on local code. It gives us that thermal break we’re always looking for by keeping warm from meeting cold.
Both SIPs and ICFs get integral structural strength without the need for studs.
This eliminates thermal bridging, which happens when you have anything in your wall that conducts cold more than your insulation, like wood or metal studs. That’s why you have cold spots in the winter on your exterior walls.
People love SIPs and ICFs because of their high R-value and high-energy efficiency levels (some are even Energy Star rated).
However, the main selling point of these panels is that they provide all the layers in a wall that should be there without having to build them. This saves time and costs related to labour.
The building process is quick and requires less equipment. When you’re building in harsh climates outdoors you want building materials that can go up fast. That’s why they’re popular for First Nations housing.
But this can also be a doubleedged sword.
People think the installation is so easy you don’t need highly skilled labour to do it. In my thirty years experience, any time you have unskilled labour doing anything there will be mistakes.
Also, because SIPs and ICFs are somewhat new to the industry, not many tradespeople know how to work with them properly.
Education is crucial any time you have a specialized product. Tradespeople need to learn how to work with the product — no matter what it is — and what they can and can’t do. SIPs and ICFs are fairly new to the market. Not everyone is going to know how to work with them the right way.
For example, you can’t leave SIPs exposed to the elements for long, especially if they’re made from OSB or plywood. If moisture gets in them the entire structure can be compromised. Once the panels are up and in place house wrap should go up quickly to prevent moisture from getting in.
Another problem is that unskilled tradespeople forget that these are structure materials. You can’t carve into them. If you do it’s like cutting into joists – you compromise the strength of the entire structure you’re building. They are only as strong as the weakest link.
That means you can’t go changing things like adding windows or doors. You need to stick to your construction plans.
Also, every SIP and ICF panel is manufactured according to specific engineered construction plans; you can’t go to the store and buy SIPs and ICFs. That’s why it’s cheaper for production builders to use them when building large volumes of a single model home. But that also means that every panel has a designated place it must be installed. Just because all the panels look the same doesn’t mean they are the same.
SIPs and ICFs are moving residential housing in the right direction. They’re popular because you get a lot of results for not a lot of work. You also have low labour costs because installation is easy. But like I said, you need to know what you’re doing. When it comes to SIPs and ICFs many things can go wrong.
I like sticking to what I know. And I know that a cinder block home studded and spray foamed is 100-per-cent thermal broken.
To me, proper construction is always foolproof. And that’s something I can stand behind.