Removing old attic insulation or adding over it

When can you leave old insulation in place?

Insulation does not wear out the way a furnace does. Dry fibreglass or cellulose that has settled a little can keep working for decades. If it is clean, free of mould and still covers the joists evenly, the cheaper route is to air seal and blow or lay more material over the top. That approach is the one set out in attic insulation in Canada. Compressed or matted layers lose some performance, but extra depth on top usually makes up for it. Do not cover wet insulation, because new material over a damp layer traps the problem.

What problems justify removal?

• Water damage or mould. Fix the leak or moisture source first, then remove the affected material.
• Rodent or bird contamination. Droppings, urine and nesting material make the layer unhygienic and often need professional cleaning.
• Fire or smoke damage. Charred or smoke-soaked material should come out.
• Vermiculite. It may contain asbestos. Do not disturb it, and do not remove it yourself. Have it tested and use an accredited abatement contractor if needed.
• Contamination by dust and debris from renovations. Heavy contamination can be vacuumed.

Also reconsider the layer if you are rewiring, replacing the roof deck or fixing a leaking duct, since the work disturbs it anyway.

How is old attic insulation removed?

Professionals usually use a large vacuum with a hose run from a truck, which sucks loose-fill insulation out and leaves the attic floor clean. Batts are lifted out by hand and bagged. Workers wear respirators, protective suits and goggles, and the attic is sealed at the hatch to keep dust out of the house. Material must go to a waste facility that accepts it, so ask how disposal is handled. After removal comes the best moment for air sealing, covered in air sealing a house, because the ceiling plane is fully exposed.

What goes back in?

Choose the new material for the space and the budget. Blown cellulose or fibreglass fits most open attics, and cellulose versus fibreglass sets out the differences. Foam may suit unusual shapes, see spray foam insulation. Install baffles at the eaves so that ventilation stays clear, insulate the hatch and keep material away from flues and unrated light fixtures. The target depth depends on your climate zone and code, as discussed in R-values by region. A well-insulated, ventilated attic also helps limit ice at the eaves, a problem covered in ice dam prevention.

What will it cost and who should do it?

Removal adds labour and disposal on top of the cost of new material, and the total depends on attic size, access, the amount of material, region and season. Quotes decide. Ask for removal, cleaning, air sealing, new insulation, baffles and disposal as separate lines, with the target R-value and warranty in writing. Where mould, rodents or asbestos are in question, hire a firm with the right training and insurance. Check the Government of Canada energy-efficiency pages, your province and your utility for any current incentives, and keep before-and-after photos and invoices.

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