Blown-In Attic Insulation in Williston, ND

Both materials do the job when installed to the right depth. Blown fiberglass is light, does not absorb moisture, and holds its loft over time. Cellulose is denser, packs tighter around wiring and framing, and does a better job slowing air movement through the insulation layer itself. Cellulose is made from recycled paper treated with borate for fire and pest resistance; fiberglass is spun glass with no additives to speak of.

In a leaky older attic where we cannot seal every gap, cellulose often wins because its density helps. In a clean, well-sealed attic or one where we are topping up existing fiberglass, blown fiberglass is usually the better match. We also look at the ceiling drywall. Older half-inch drywall on 24-inch centers can sag under a full load of wet-spray cellulose, so we stick to dry-blown material and keep the weight reasonable.

Either way, we are aiming at R-60. That works out to roughly 16 to 20 inches of settled depth depending on the product, and we install to the manufacturer's coverage chart rather than guessing.

The top of every interior wall is a gap. Drywall meets the top plate and leaves a crack along both sides, and every wire or pipe that drops down from the attic leaves a hole. Warm house air finds those gaps all winter. Once insulation is blown over them, they are invisible and nearly impossible to fix without digging.

So we seal first. Top plates get a bead of foam or caulk along both sides. Wire and plumbing penetrations get foamed. The attic hatch gets weatherstripping and a rigid insulated cover. Recessed can lights get a fire-rated cover box sealed to the drywall. Bath fan housings get sealed and the duct gets checked to confirm it actually exits the roof rather than dumping into the attic. Chimney chases and dropped soffits get blocked with sheet metal or rigid foam and foamed at the edges.

This step is where the heat loss actually stops. Blowing R-60 over an unsealed ceiling is like wearing a heavy coat with the zipper open.

An ice dam forms when a warm attic melts the snow on the upper roof. Meltwater runs down to the eave, which sits over the unheated overhang and stays cold, and it refreezes there. The ridge of ice backs water up under the shingles. Williston gets the snow and the cold to make this happen, and the wind helps by drifting snow onto one side of the roof.

The fix is to keep the attic as cold as the outdoors. That means stopping warm air from getting up there (air sealing), slowing heat conduction through the ceiling (R-60), and letting outdoor air move through from the soffits to the ridge (ventilation). Loose-fill insulation blown to full depth will bury the soffit vents unless something holds it back, so we install foam or cardboard baffles in every rafter bay at the eave before we blow. The baffle keeps a channel open from the soffit up past the insulation, and a blocker at the bottom keeps the material from sliding out onto the soffit.

We also check that the attic actually has intake and exhaust. Plenty of Williston houses have a ridge vent and painted-over soffits, or soffit vents and no exhaust at all.

If the existing insulation is dry, clean, and reasonably even, we blow over it. Fiberglass over fiberglass, cellulose over either. There is no need to remove old material just because it is old. We do rake it level first so the new layer is uniform, and we still do the air sealing, which means moving the old insulation aside along the top plates and putting it back.

Before we blow, we staple depth markers to the trusses across the attic. These are simple rulers that show the installed depth from anywhere in the attic, and we leave them in place. They let you, an inspector, or an appraiser confirm the depth years later without a tape measure. The attic hatch gets a card noting the product, the installed depth, and the settled R-value.

If the old material is wet, moldy, smoke-damaged, or contaminated, it comes out first. See our insulation removal page for how that works.

The biggest factor is square footage of attic floor and how much depth we need to add. A top-up from R-30 to R-60 uses far less material than a bare attic. Material choice matters a little, with cellulose and fiberglass priced differently per installed R-value. The amount of air sealing needed is the next factor: a house with a dozen can lights, two bath fans, and a chimney chase takes more prep time than a simple ranch with one hatch.

Access affects the price too. A walk-up attic with a full hatch is faster than a scuttle hole in a closet ceiling. Low-pitch roofs with tight eaves slow down the baffle work. If old insulation has to come out first, that is a separate line item. We break all of this out on the quote so you can see where the number comes from.