¦ HI-PIRform Roof System comprises BCI Joists and PIR insulation.
¦ The system does not require counter battens.
¦ The first pilot project will be carried out this year.
¦ A U-value of 0.1W/m²K can be achieved.
¦ Components are connected from within the roofscape on site.

Boise Cascade’s new structural roof panel system, HI-PIRform, combines the high flexural strength of BCI Joists with the high compressibility resistance characteristics of PIR foam insulation.

Using a high-strength adhesive, the insulation slabs are bonded to the I-joist’s slender OSB web to create a panel of alternating layers of insulation and supporting timber.

The BCI Joist flanges stand clear of the insulation which means they do not require counter battens and the roof can be felted and tiled in the traditional way. Similarly, on the inside of the roof, the contractor simply fixes plasterboard lining direct to the inner flanges, leaving a space for the electrician to route the wiring.

The whole system is supported by a unique and specially-designed ridge detail – Versa-Ridge – engineered from Boise’s Versa-Lam LVL. This provides the structural backbone of the system. As all components are modular, assembly is quick and easy.

Full-scale trial

After two years in development, the HI-PIRform System has recently undergone extensive tests, including a full-scale trial assembly. Final adjustments to the design (such as modifying tolerances to accommodate minor inaccuracies in the building geometry) have resulted in a fully engineered system which is due for its first on-site pilot project later this summer.

Boise says the cost of the HI-PIRform system is competitive. The complete insulated structural kit, including spandrel wall panels, floors, ceiling and roof cassettes, is designed to remain cost-effective with traditional build costs. The resulting roof, while outwardly traditional, is billed as very technically advanced.

On larger buildings, more adventurous roofs are possible. With BCI Joists available in lengths up to 12m, very wide spans can be achieved, especially when used in conjunction with the company’s Versa-Lam LVL beams.

The system also scores well on thermal performance. U-values as low as 0.1W/m²K are achievable using BCI Joists of 302mm in depth with a layer of PIR foam just 220mm thick; to achieve the same level of thermal performance using traditional methods would require a 380mm-thick layer of mineral wool between rafters more than 450mm deep, says Boise.

With mechanical handling equipment lifting the cassettes into place, the HI-PIRform system is designed for site staff to connect the components together from within the roof, reducing health and safety risks on site.