Building materials profile: ROCKWOOL
We’ve been using ROCKWOOL (formally Roxul) since Greening Homes’ early days. Headquartered – in North America – in Milton, Ontario, Rockwool offers a variety of stone-wool insulation products.
We were one of the first companies to use ROCKWOOL as a sub-slab insulation replacement for extruded polystyrene spray foam, which has a high-embodied carbon footprint and a very high Global Warming Potential (GWP).
ROCKWOOL, in addition to cellulose, is now our go-to insulator, as we have tried to substitute using polystyrene altogether.
As its name suggests, ROCKWOOL is made out of rock, the world’s most abundant material, and upcycled material. As a result it is fire and water resistant. Unlike cellulose, Rockwool does not reach a saturation point when wet. It dries out well and does not degrade with moisture although its insulative capacity is reduced temporarily while wet. It is also pest resistant. With an insulation value of R4 per inch, Rockwell is on par with other batt insulation products, but slightly higher performing given its durability over time.
In addition to subfloors, we use Rockwool products in wall and roof assemblies, as well as for continuous insulation. ROCKWOOL SAFE’n’SOUND® offers our clients a sound barrier between party walls, floors and bathroom cavities.
In theory, Rockwool is recyclable, and in the U.K., the company offers a recycling program of uncontaminated old batt and scraps. Unfortunately, the company does not yet offer this service in its other markets, including Canada. According to a company spokesperson, a “global sustainability goal of ROCKWOOL is to develop these [recycling] programs.” We hope this service is offered sooner rather than later to help us – and the building sector – reduce landfill waste.
While we use ROCKWOOL as a substitute for polystyrene spray foam, its products are not toxic free. They contain six percent formaldehyde. ROCKWOOL products also require energy in their creation. Its toxicity and high carbon content are not nearly as high as spray foam, but they are certainly higher than cellulose, which is toxin free, carbon sequestering, and contains low embodied energy because it is made of recycled newspaper.
Bottom line: ROCKWOOL is made from a natural and abundant material and upcycled content, easy to access and use, locally-made, and fire and water resistant. While not the “greenest” product on the market, it is still, relatively, greener than most and an outstanding means to improve a home’s energy performance and comfort.