On a typical 1950s North York semi, expect $4,000 to $12,000 for the exterior walls.
That is a wide range for a reason, and the reason is not the size of your house. It is what the outside of your house is made of. Go and look at it now, because that single fact moves the number more than anything else on the quote.
If the walls are clad in aluminium or vinyl siding, you are at the lower end. If they are brick veneer, you are at the upper end, or the job has to happen from inside. Everything else in this article explains why, and what else shifts the figure.
The work itself is the same either way: drill, fill and patch. Holes into each stud cavity, insulation blown in under pressure, holes sealed. No walls come down.
Why the Outside of Your House Sets the Price
Same wall area, same interior layout, two houses on the same street. The one with siding costs noticeably less to insulate than the one with brick.
Roughly 30% to 50% less, in fact.
With siding, a section of panel comes off, the holes go into the sheathing behind it, and the panel goes back on. When it is finished there is nothing to see, because the evidence is hidden behind cladding that was designed to be removed.
With brick veneer, every hole is drilled through masonry and every hole has to be patched afterwards with mortar that matches. That is slower, it takes more skill, and it is the patching rather than the drilling that costs the money. A brick house also usually needs more drill points, because the cavity behind brick veneer is less forgiving about where insulation can reach.
Before you spend either figure, it is worth settling whether the walls are actually your problem. A cold room has several possible causes and walls are only one of them.
When the Job Has to Move Inside
Sometimes brick veneer does not get drilled at all, and the whole job relocates to the interior.
That happens when the masonry is in poor condition, when the mortar cannot be matched acceptably, when there is a drainage cavity behind the brick that must not be filled, or when the homeowner simply will not accept visible patching on a front elevation.
Working from inside means the holes go through interior drywall instead. Cheaper to drill, far more disruptive to live with, and the patching and repainting is now inside your rooms rather than outside your house. It is a different kind of cost rather than straightforwardly a higher one, and which way it lands depends on how much of the interior has to be made good afterwards.
The important thing is that a quote should tell you which approach it is pricing. Two quotes for the same house, one from outside and one from inside, are not comparable numbers.
The Four Things That Move the Quote
Beyond the exterior finish, four variables set the final figure.
Material choice. What goes into the cavity. The options are not interchangeable and they do not cost the same.
Accessibility. How easy it is to reach every wall. A detached house with clear ground on all four sides is straightforward. A semi with a narrow side passage, a fenced neighbour, a conservatory in the way or scaffolding required at the gable end is not.
Wall preparation. What has to happen before anything is blown in. Matching mortar, removing and reinstating cladding, dealing with a cavity that is partly filled already, or making good around window and door reveals.
Total surface area. This sets the baseline, and it is the only one most cost pages mention. It is genuinely the least interesting of the four, because it is the one you can work out yourself.
Size gives you a starting figure. Labour complexity and the structure of the building decide what it actually becomes.
Walls Alone, or the Whole House
Walls are rarely the only thing worth doing, and doing several surfaces at once changes the arithmetic.
A whole-home thermal upgrade, meaning the exterior walls plus the attic side of the job plus the rim joists and basement walls, typically lands between $8,000 and $22,000 before tax and rebates on a house of this type.
That is more money, obviously. It is also usually better value per dollar, because the crew is already on site, the assessment covers the whole building envelope at once, and you are not paying twice for mobilisation. If you intend to do all of it eventually, doing it together costs less than doing it in three separate years.
The counter-argument is real too: three separate jobs spread the cost, and if money is the constraint then the order matters enormously. More on that below.
What the Rebate Does to the Figure
Ontario's Home Renovation Savings programme covers more than attics, and wall insulation is among the measures it can apply to.
This matters more on a wall job than an attic one, simply because the numbers are larger. A rebate is a bigger deal against a $9,000 quote than against a $3,000 one.
Two things worth doing before you rely on it. Check which measures the programme covers and at what level, because the amount is not the same for every measure. And ask any contractor you speak to whether they are a registered participating contractor, because the rebate route generally runs through the contractor rather than through you. Ask who submits the paperwork and when the money actually arrives.
Programme rules and end dates change. Confirm the current position rather than relying on a figure you read somewhere, including here.
Why the Cheapest Wall Quote Is Cheap
Wall insulation is easy to underprice, because almost everything that separates a good job from a poor one is invisible once the cladding goes back on or the mortar cures.
Drill fewer holes and you save time, and you also leave voids in cavities nobody will ever inspect. Patch the brick quickly with mortar that does not match and it is cheaper today and visible for the next thirty years. Do not bother checking whether the cavity is already partly filled and you may be blowing insulation into a space that cannot take it. Skip the reveals around windows and doors and the thermal bridges stay exactly where they were.
Every one of those makes the number smaller and the job worse.
There is a legitimate cheaper quote, and it sounds different. It says: your house has siding rather than brick, access is clear on all sides, the cavities are empty and consistent, so the scope is smaller. That is a reason. A lower number with no explanation attached is not a reason.
Should the Walls Even Be First
Honest answer: often not.
If your attic is underinsulated, that is almost always the better first spend. Heat rises, attic work is cheaper per unit of benefit, and what an attic costs on its own is a fraction of a wall job. A house with a poor attic and decent walls should do the attic first, and any contractor who tells you otherwise is selling rather than advising.
Walls come first in a narrower set of cases. When the attic has already been done. When specific rooms are cold and the attic above them is fine. When the wall cavities turn out to be completely empty, which is common in pre-1960 stock and represents a large, straightforward gain. And when the exterior is being worked on anyway, because if the siding is coming off for other reasons, the marginal cost of insulating while it is off is much lower.