Matthew Brennan, National Director of Sales for Thermocell and Greenfiber Canada, breaks down why cellulose is the pragmatic choice for Atlantic Canada's retrofit and net-zero build surge — fire performance, moisture tolerance, and the one installation metric that separates a professional job from a dispute.
In 2015, walking into a builder meeting and leading with the sustainability angle of your product was a fast path to a short conversation. Contractors didn't care. The value proposition had to stand on thermal performance, price, and ease of installation — everything else got waved off. Matthew Brennan remembers those rooms. He'd been in the insulation business long enough to know that the green story was real, but the audience wasn't ready.
That changed. By the time he sat down with host Daniel Arsenault on Episode 40 of the Atlantic Construction Podcast, the shift was already behind them. A North American consumer study found that 83% of respondents preferred environmentally conscious products — and that number was moving product on shelves. Brennan called it "a complete sea change right like we would I remember going into meetings even in 2015 and talking about this and people say they just don't care" The point isn't that consumers became idealists. It's that the business case for green insulation finally converged with a building code reality — net-zero requirements — that made the spec unavoidable.
Brennan is the National Director of Sales for Thermocell and Greenfiber Canada, the Canadian arm of Greenfiber (Applegate Greenfiber Holdings LLC), North America's largest manufacturer of cellulose blown-in insulation. The Debert, Nova Scotia plant has been running since 1987. During Atlantic Canada's construction boom, it was running seven days a week.
What cellulose actually is — and why it didn't need a rebrand to earn its fire rating
Cellulose insulation is recycled paper fibre treated with borate. That's the whole story. The borate does two things most people don't connect: it gives the product its Class 1A fire rating, and it repels pests. Brennan notes that in agricultural applications — chicken barns, potato storage facilities in the Annapolis Valley and northern New Brunswick — farmers were reporting measurable productivity improvements, because "animals and pests really don't like it and from an agriculture environment that really matters"
On the fire side, the numbers are concrete. In a controlled full-house burn test comparing insulated assemblies, the cellulose-filled structure held 45 minutes longer than the comparison. The borate treatment doesn't make the material non-combustible, but it slows the spread in a way that gives occupants and crews a meaningful window. Class 1A is the top residential fire rating.
The density comparison with other insulation types is where the installer conversation gets practical. Fiberglass sits at the light end of the density spectrum; spray foam at the heavy end; cellulose falls in between, closer to spray foam on density while manufactured off-site in a controlled plant environment. That last point matters when you start listing the ways spray foam can fail — substrate temperature, product age, machine calibration. As Brennan puts it, "there's a lot of ways to mess it up when we're talking about spray foam" Cellulose doesn't have those on-site variables. It comes off the truck already made.
For sound performance, the product clocks STC-54 for between-floor applications — a number that moves commercial and multi-residential clients who care about acoustic separation without adding assembly complexity.
The retrofit case: moisture tolerance as the deciding variable
Atlantic Canada has a lot of old housing stock. Pre-1990 construction in the Maritimes means variable vapour barriers, unknown moisture history, and framing that doesn't always square with current code expectations. When a contractor goes into a retrofit job and opens up a wall cavity, they're working with whatever conditions exist — not whatever the building plans say.
This is where cellulose earns its retrofit reputation. The material is hygroscopic: it can absorb and release moisture without structural damage to the assembly, within limits. Spray foam in the same wall, over an unknown moisture condition, can trap problems. Fiberglass can slump and lose performance when it gets wet. Brennan is direct about the stakes: "the big thing with any retrofit job is the unknown right yeah so new construction we have the luxury" — and in retrofit, that luxury doesn't exist. The hygroscopic properties don't solve a moisture problem, but they tolerate a condition that would cause other products to fail.
Thermocell was already putting this to work with Habitat for Humanity Halifax, and was involved with the ReCover Initiative — a Dartmouth-based deep-retrofit accelerator developing modular exterior-cladding panels for multi-unit residential buildings aimed at achieving net-zero without displacing tenants. The application is exactly the kind of complex, inhabited-retrofit scenario where cellulose's moisture tolerance is an operational advantage.
The dense-pack wall: one number, one argument
The installation conversation around cellulose walls tends to get derailed by a misconception about settling. A newly blown attic or wall will show a two-inch depth reduction after install. Brennan has watched this cause unnecessary job-site disputes. The drop is designed in — it's not lost material, it's the product finding its settled density. "I put 20 inches in and I have 18 inches I must have lost 10 right and they didn't lose anything" is the conversation he's spent years correcting.
For dense-pack wall systems, the target density is 3.5 lbs per cubic foot. That's the number that produces a self-supporting assembly that won't settle further. The field method for hitting it doesn't require on-site testing equipment: count bags per section. "take a 10 foot sectional wall mark on the wall we should have six bags done and blown at this point" — if you're tracking bag count against section length, you're tracking density. That's the whole quality control system, and any trained installer can run it.
The CCMC-approved dense-pack assembly for Canadian residential construction is the EnviroShield system, installed behind mesh or poly vapour barrier by manufacturer-certified installers. CCMC approval matters for builders who need a code-defensible spec — it's not a marketing credential, it's the document a building official will ask for.
For new product categories that need code-path approval, Brennan is clear about the strategy: "it's all three for that one yeah so that's the biggest undertaking right now in terms of involvement" Architects, building code officials, and contractors have to be reached simultaneously. Hitting one group and waiting for it to cascade doesn't work.
Net-zero codes changed what builders will listen to
The Sanctuary brand relaunch — a consumer-facing product line built around the concept of a healthier, quieter, more efficient home — was runner-up for sustainable product of the year at Home Depot in the US. The brand positions cellulose walls and attic together as a whole-home assembly: thermal, acoustic, and indoor-air benefits in a single specification.
The builder programs that came with it are practical. The Sanctuary Builder program donates product to show homes: "if you are building a show home we'll donate product for that show home to basically have cellulose in your walls and your attic" A show home is a working demonstration that bypasses the architect specification path — the end buyer sees the product in context, the builder gets a free spec, and Greenfiber gets a case study. The Sanctuary Trusted Contractor program creates a trained installer network with certified designation.
The two-hour fire wall product — a new assembly for multi-residential townhouses that replaces traditional shaftliner — had already launched in US markets including Atlanta, Phoenix, and Washington DC by the time of this recording, with a Canadian launch being planned. Getting it into Canadian multi-res is the code-path challenge Brennan described: architects, code officials, and contractors all at once.
Where Atlantic Canada stands — and the workforce problem nobody's solved yet
The Debert plant running seven days a week is one data point. The bigger picture is that Atlantic Canada's construction boom was running into the same wall as every other regional market: not enough people. Long-tenured plant staff — including at least one employee from the facility's 1987 opening — are irreplaceable assets, and the path to replacing them when they retire isn't obvious.
The ABSDA conference on immigration as a workforce strategy opened a door Brennan hadn't fully considered before attending. The Ukrainian worker integration story he heard — from a Home Hardware in the region — landed as a proof of concept. "going to that conference definitely opened our eyes to maybe that as a possibility yeah especially for skilled qualified workers" The broader point is that manufacturing-sector construction jobs are undersold as career paths. The pay is real, the benefits are real, the people are real. "good paying jobs good benefits good people yeah" is the pitch, and it needs to reach NSCC graduates who might not be thinking about a plant floor as a career trajectory.
The Atlantic Construction Podcast itself, in Brennan's framing, is part of the infrastructure for solving that. A platform that shows young people what the construction industry actually looks like — the companies, the people, the work — is a recruitment tool. Not metaphorically. Literally.
Greenfiber (greenfiber.com) manufactures and markets cellulose blown-in and spray-applied insulation across North America. The Canadian operation — formerly Thermo-Cell Industries — runs from Debert, Nova Scotia and covers thermal, acoustical, and specialty fibre applications including hydroseeding mulch. The EnviroShield dense-pack wall system manual is available at greenfiber.com. Also featured: ReCover Initiative, a Dartmouth-based deep-retrofit accelerator.
Guest: Matthew Brennan, National Director of Sales, Thermocell / Greenfiber Canada. Episode 40 of the Atlantic Construction Podcast. Watch the full episode. Dense-pack cellulose density spec (3.5 lbs/ft³) verified via Building America Solution Center.