Can I add insulation to existing walls without removing drywall in NB? | Insulation IQ?

Yes — in most cases you can add insulation to existing walls in New Brunswick without touching the drywall, and this is actually the most practical approach for the majority of retrofit projects across the province. The technique is called dense-pack injection (or blown-in wall insulation), and it has become the standard method for upgrading wall cavities in older Moncton, Fredericton, and Saint John homes without gut-level renovation.

Here is how the process works. A contractor locates each stud bay by probing or using a stud finder, then drills a series of holes — typically 2 to 3 inches in diameter — spaced every 12 to 18 inches vertically in each bay. These holes are made either through the exterior cladding (siding, trim, or sheathing is removed in strips, holes drilled, then everything reinstalled) or through the interior drywall if the exterior approach is not practical. A dense-pack hose is inserted to the bottom of the cavity, insulation is injected under pressure as the hose is gradually withdrawn, and the result is a tightly packed cavity with no voids. Holes are then plugged and the surface is patched.

The exterior approach is generally preferred in New Brunswick when the home is getting re-sided anyway, or when the siding is vinyl that can be temporarily removed in sections without damage. Drilling from outside means no interior patching, painting, or disruption to lived-in spaces. It also gives the contractor visual access to the cavity, allowing them to check for and remove any old, degraded insulation or debris before injecting fresh material.

The interior approach works well when the exterior cladding is brick, stone, or stucco — materials that cannot be easily re-drilled and patched. Interior holes are smaller and can be finished with drywall plugs and a coat of paint, leaving minimal evidence of the work.

Dense-pack cellulose is the most common material used for this application in NB. It is made from recycled paper fibre, treated with borate for fire and pest resistance, and achieves approximately R-3.7 per inch when packed at the correct density (typically 3.5 lbs/ft³ or higher). A standard 2x4 stud bay filled with dense-pack cellulose reaches roughly R-13. For 2x6 walls, the result is approximately R-20 — close to what the NB Building Code requires for climate zone 6 effective wall performance in new construction.

Dense-pack fibreglass (such as Spider or similar products) is an alternative that some contractors use. It is slightly less dense than cellulose by nature but achieves similar R-values and has a slightly lower moisture absorption rate, which can be a consideration in older New Brunswick wall assemblies with variable vapour control.

There are some limitations to the drill-and-fill approach. Walls with internal fire blocking (horizontal blocking between the studs, common in older NB homes) require holes drilled in multiple zones — above and below each block — to ensure the full cavity is filled. Cathedral walls or walls with unusual framing may also require more holes. An experienced contractor will probe each bay before injecting to map out any obstructions.

Walls that are already partially filled with old fibreglass batts that have shifted or settled may need the old material removed before dense-packing. Trying to inject over settled batts leaves voids, reducing the effectiveness of the upgrade.

Air sealing is an important companion to any wall insulation retrofit. Even well-filled cavities have gaps at electrical boxes, pipe penetrations, and top and bottom plates. Some contractors use a brief spray of two-component foam at these locations before dense-packing. In a New Brunswick home, wall air leakage is responsible for a significant share of total heating energy loss — sealing as you go makes the insulation dollar go further.

For rebate eligibility, above-grade wall insulation improvements qualify under the Canada Greener Homes Grant (up to $1,000) and NB Power's efficiency programs, provided you have a registered energy advisor perform pre- and post-upgrade EnerGuide audits.

For homes in heritage neighbourhoods in Saint John's uptown or Fredericton's old residential streets, the non-invasive nature of dense-pack injection is particularly valuable — you preserve the original interior and exterior character while dramatically improving thermal performance.

To find contractors who specialize in drill-and-fill wall insulation across New Brunswick, browse the listings at New Brunswick Insulation or the New Brunswick Construction Network.

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Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• Gionetterenovations
• Arctic Fox Construction Inc.
• moose luxury painting
• 3Tone Construction Ltd
• Brunswick insulation & roofing