A cross-laminated timber (CLT) manufacturer based in St. Mary’s, Ont., will build 30 houses for the First Nations in Grand Rapids, Man.
The project is a first for CLT in First Nations housing but the manufacturer suggests there are good reasons to think it won’t be the last.
The assembly can save money on building costs and provide a durable product that is mould-resistant, says Nancy Dewar, vice-president, Guardian Structures, the manufacturer awarded the contract to build the houses.
The design consists of horizontal cross-laminated slab/wall roof panels assembled in a plant with insulation, doors, windows, siding, plumbing, electrical and other building materials, says Dewar.
Construction is expected to start mid-June.
Dewar says last year Guardian was approached by the project’s developer and architect Douglas Cardinal, who couldn’t solve design/budget criteria with conventional CLT.
"Douglas expressed interest in Guardian’s history of using mass timber wrapped with fiberglass composite for bridge applications."
Guardian can encapsulate dimensional lumber, Glulam or CLT with a "see through" fibreglass composite which is impermeable to water and immune to brittle failure while it increases the strength and stiffness of the product, she says.
Guardian’s design for the project includes the manufacture of 2.46-metre-high by 7.73 metre-long walls as one piece with higher racking loads for handling ease and shipping.
Dewar says Guardian’s CLT product has a number of advantages over stick-built construction for the First Nations project. For starters the 105 mm thick CLT is hygroscopic, meaning it expels "large amounts of humidity naturally."
That assembly with the insulation and vapor barrier installed on the outside of the house prevents mould from developing, Dewar points out.
Mould has been a problem in First Nations Housing improperly designed with wood frame and drywall.
Dewar adds that CLT is more durable than drywall.
Furthermore, because the design is done upfront, on site change orders are less likely. "It means faster installation because of technology in people and equipment such as CNC machines that can cut to tolerances with 0.05 mm."
Typically, she says, installation is up to 25 per cent faster than traditional materials.
CLT’s structural walls — usually 105 mm thick — offer an R-5 insulation value. "And more importantly the insulation on the exterior CLT panel encapsulates the building seamlessly, greatly reducing thermal loss."
Dewar says CLT better meets the challenge of rising energy costs than stick frame "which has greater thermal loss every 16 inches."
"The biggest difference from dimensional lumber in Guardian’s opinion is that CLT is the only material to our knowledge that sequesters large amounts of carbon dioxide, she explains. "The time has arrived for companies to justify their worth to society, with greater emphasis being placed on embodied carbon that is sequestered, operational costs, sustainable, environmental, societal impact, rather than straight economics."