A huge share of Oshawa was built in one long stretch — the decades after the war, when the city grew fast around the auto industry and thousands of modest, practical family homes went up to house the workforce.
They were good, solid houses. They were also built quickly, to the standards of their day — and in the 1950s and 60s, “insulation” in an attic often meant a few inches of something, or in the oldest cases, almost nothing at all.
Seventy years later, most of that original insulation is still up there, settled and thin. If you own one of these homes and the upstairs is cold, the bills are high, or the roof grows icicles every winter, the attic is almost always the reason. Here’s what these houses need.
Why post-war Oshawa homes lose so much heat
Three things stack up in a typical mid-century Oshawa house:
It started with very little. Attic insulation standards in the 1950s and 60s were a fraction of today’s. A house from that era was insulated correctly for then — which is far below where an attic should be now. Some of the oldest wartime homes started with almost nothing.
What’s there has settled. Whatever went in has spent decades compressing under its own weight and dust. The depth you’d measure today is less than what was installed — and it wasn’t much to begin with.
The ceiling was never air sealed. Sealing the little gaps in the ceiling — around wiring, pipes, light fixtures — wasn’t standard practice back then. So warm air leaks straight up through the ceiling, carrying heat and moisture into the attic.
Put together, a lot of these homes are running on an effective insulation value a fraction of what they should have. The upside: that means the improvement from doing it right is dramatic. Post-war homes get some of the biggest comfort-and-savings gains of any housing in Oshawa.
Measure what you’ve actually got — five minutes
Don’t guess from the age of the house. Measure.
- Open the attic hatch, shine a light, step only on joists
- Push a ruler down to the drywall at several spots, including near the eaves
- Convert:
| Material | R per inch | 4 in | 8 in | 12 in |
|---|---|---|---|---|
| Blown cellulose | ~3.4 – 3.8 | ~R-14 | ~R-28 | ~R-42 |
| Blown fibreglass | ~2.7 – 3.0 | ~R-11 | ~R-22 | ~R-34 |
| Old settled batts | ~2.5 – 3.2 | ~R-11 | ~R-22 | — |
Target: R-50 minimum to qualify for the rebate, R-60 as the goal. Many post-war Oshawa attics measure R-20 or less — sometimes far less — which means there’s a lot of easy gain available.
If you find loose grey or silvery pebble-like granules, stop — that may be vermiculite, which can contain asbestos and needs testing before anyone works up there. It shows up in some homes from this era. Don’t disturb it. Attic insulation removal →
What these older homes specifically need
Air sealing first — it matters more here than in a new house
In a home where the ceiling was never sealed, air leakage is doing a lot of the damage. Warm indoor air escapes through dozens of small gaps — around wiring, plumbing stacks, the tops of interior walls, light fixtures, the attic hatch. Sealing those comes before adding insulation. Blow new insulation over an unsealed ceiling and you’ve buried the leaks where nobody can fix them.
This is the step budget jobs skip, and it’s the step that matters most in a post-war home.
Baffles and ventilation
Older Oshawa homes often have limited attic ventilation to begin with, and blown-in insulation will bury what soffit venting exists unless baffles hold it back. Blocked venting plus a cold attic equals moisture, frost, and the ice dams that build along the eaves every winter. Baffles are cheap and go in before the insulation. Baffle installation →
Small hatches and tight access
Post-war homes often have small attic hatches and lower roof pitches, meaning tighter working conditions and shallow space at the eaves — exactly where insulation gets shorted. It’s workable, it just takes a crew that will actually get into the low areas rather than blowing the middle and calling it done.
The walls might be a conversation too
Many post-war Oshawa homes have little or no wall insulation, and you usually can’t open the walls without a renovation. If your walls are a major source of cold, drill and fill can insulate them through small holes without opening them up — separate from attic work, but often worth doing together. Drill and fill →
If you’re in a newer north-Oshawa home instead
Not all of Oshawa is post-war. The newer subdivisions north of the 401 corridor and up toward the top of the city are a different story — engineered trusses, better access, higher starting insulation. But they have their own recurring gaps:
- Insulated to the minimum of their (more recent) build year, and starting to settle
- Baffles missing or crushed
- The attic hatch left bare
- The ceiling never air sealed — including any pot lights added later
- The cold room over the garage (a garage-ceiling problem, not an attic one). Garage ceiling insulation →
Newer or older, the fix rests on the same three things: seal the ceiling, ventilate properly, insulate to full depth to the eaves.
What a proper job looks like
- Assess — measure existing depth, identify the material, check for vermiculite, check venting and penetrations
- Test or stop for vermiculite where present
- Remove only if contaminated by mould, water, rodents or smoke
- Air seal the ceiling plane — the highest-value step in an old home
- Install baffles, confirm soffit intake
- Insulate and weatherstrip the hatch
- Blow to depth, out to the eaves — R-50 minimum, R-60 target
- Mark depths so the result is verifiable
On material: cellulose gets more R-value into less depth and is denser (good for the leaky, awkward attics of older homes); fibreglass is lighter and often cheaper for the same value. Both are rebate-eligible.
Cellulose blown-in → · Fibreglass blown-in →
Frequently asked questions
My house is from the 1960s. How bad is the attic likely to be? Often well under R-25, sometimes much less — which means a big, cost-effective improvement is available. Measure to be sure.
Do I have to remove the old insulation? Only if it’s contaminated by mould, water, rodents or smoke, or if it’s vermiculite needing testing. Otherwise new goes over old and the R-values add together.
What’s vermiculite and should I worry? Loose, pebble-like greyish granules found in some mid-century attics. It can contain asbestos, so don’t disturb it — have it tested before any work.
Why do I get ice dams / icicles every winter? Heat and air leaking into the attic plus poor ventilation. The fix is air sealing, full-depth insulation to the eaves, and proper airflow — not just more insulation.
Do I have to leave home during the work? No.
How long does it take? A straightforward top-up is usually a single day. Vermiculite removal or ventilation fixes extend it.
Get an older home assessed properly
Post-war Oshawa homes reward doing the attic right — the starting point is so low that the improvement is large. But they need air sealing, ventilation and a crew that gets into the tight spots, not just a quick blow-in. The only way to know what yours needs is a proper look.
Pro Insulation Contracting has insulated Ontario homes for over 10 years and serves Oshawa and Durham Region. Free on-site assessment, written scope, fixed price before any work starts — and an honest word if we find vermiculite or anything that needs handling first.
