Attic Insulation In Saint John, New Brunswick

Cold Roof Or Warm Roof

The vented approach keeps the attic cold. Openings through the ceiling below are closed off one by one, and the insulation then sits on top of a sealed plane. Uncomplicated roofs with an empty attic above them usually want this, and it is the cheaper of the two.

The unvented approach moves the boundary up to the roof itself. Foam is applied against the sheathing, carried up the gables, and the vents are closed permanently.

Choose unvented when mechanical equipment or ductwork lives up there, when dormers and valleys break the attic into compartments nobody can crawl between, when a finished room has dead space behind its knee walls, or when the same length of eave ices up winter after winter.

That call gets made from inside the attic, not from the driveway.

Why Attics Here Grow Frost

Warm indoor air carries moisture. When it leaks up through the ceiling into a cold vented attic it cools, and the moisture comes out of it onto the first cold surface available, which is the underside of the roof sheathing.

On a coastal site the outside air is not doing you any favours either. It arrives already close to saturated for much of the year, so the attic has less capacity to dry than it would inland.

Frost on the sheathing, damp staining on the nail points, or a musty smell when the hatch comes off are all the same story: air is getting up there that should not be.

Sealing the ceiling plane fixes it. Insulation depth on its own does not.

Ice At The Eaves Is A Heat Problem

People blame the gutters. The actual sequence is that heat leaking into the attic thaws snow partway up the slope, the meltwater travels down to the overhang, which has no heat under it, and refreezes. The dam thickens, and eventually water finds its way back up beneath the shingle courses.

Depth alone will not reliably stop it, because what drives it is leaking air rather than heat conducted through the ceiling. Take the heat away, either by sealing the plane below or by relocating the insulation to the sheathing, and the cycle has nothing to feed on.

Ice forming at the same spot in consecutive winters is a symptom, not bad luck.

Depth, R-Value And Rebate Thresholds

You get around R-6 to R-7 an inch out of closed cell, drifting down toward R-6.5 over the years. Open cell delivers around R-3.5 to R-3.8.

Zone 6 targets are not lenient. Between the number you have to reach and the depth the space physically allows, the specification writes itself; it does not start from a thickness somebody picked in advance.

Attic work is also the best paid line in the provincial rebate schedule, running from around $0.40 a square foot at R-15 added up to around $0.85 at R-60. That threshold is worth knowing before you settle on a depth, because a small change can move which band you land in. Book the energy evaluation before we start.

We will not quote an assembly R-value without telling you the depth it assumes.