Should You Insulate Exterior Walls? Options and Costs
🇩🇪 Diesen Artikel auf Deutsch lesenIf your home was built before the 1970s and the walls are uninsulated, dense-pack blown-in insulation is usually the most practical upgrade: installers drill small holes, fill the cavities and patch them. It can noticeably improve comfort and lower heating and cooling bills. If you're replacing siding anyway, adding rigid foam outside is another option.
Attic insulation usually comes first because it's cheaper and easier. But in older homes with empty walls, wall insulation can be the next big step in comfort and savings.
How to check your walls
- Turn off power, remove an outlet cover on an exterior wall and look into the gap beside the box with a flashlight.
- Check during renovations or in an unfinished basement where wall framing is visible.
- An energy auditor's infrared camera shows uninsulated areas clearly.
Main options
| Method | When it fits | Disruption |
|---|---|---|
| Dense-pack cellulose or fiberglass (blown in) | Existing homes with empty cavities | Low: small holes inside or outside |
| Injection foam | Existing cavities, higher R per inch | Low to medium |
| Rigid foam under new siding | When replacing siding | Part of the siding project |
| Open walls (batts or spray foam) | Gut renovations | High |
What it saves
Savings depend on climate and how leaky the home is. In cold climates, insulating empty walls can significantly cut heat loss through the walls and make rooms feel less drafty. Estimate your current heating cost first:
Home Heating Cost CalculatorEstimate your yearly and monthly heating billTry the calculator →Things to watch
- Fix moisture problems and roof or gutter leaks before insulating.
- Old knob-and-tube wiring should not be covered with insulation; have an electrician check first.
- Ask about air sealing at the same time — it often adds as much benefit as the insulation.
Frequently asked questions
Will blown-in insulation settle?
Properly dense-packed insulation is installed at high density to minimize settling. Loose-fill in walls settles more and is not recommended.
Can I insulate walls myself?
Dense-packing requires a powerful blower and experience. Most homeowners hire a contractor for wall insulation.