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Talk Nerdy to Me: How to insulate an old house

Efficient heating systems are great, but often the real key is tightening up the building envelope

MAINE, USA — A lot of energy-saving tips in the winter months involve lowering your thermostat and wearing that ratty sweatshirt around the house. But that’s treating the symptom, not the disease. 

In many homes, the real problem is a lack of insulation. And many Maine homes have tons of character, but very little insulation.

Spending some money on insulation will pay off FAST in terms of energy savings and comfort during the winter months. (Summer too but that's less of a concern in New England.)

Let's start in the basement.

Since many basements don’t have wood framing and tend to have moisture issues, spray foam is the product of choice down here.

Spray foam is applied to the sill first and then often brought down a few feet below ground level to maximize the insulative qualities already provided by the earth.

Spray Foam: 

  • Pros: High R-value, great air barrier 
  • Cons: High cost, not eco-friendly

Next up: the walls on the first floor. 

If you have existing drywall/plaster (like everyone), the insulation professional will drill small holes either from the outside sheathing or the inside drywall. From there they will insert a hose and spray in cellulose insulation.

Of course, you’ll have holes in the drywall after this is done. They are easy to patch, but it's super quick work for a drywaller if you want to save yourself the trouble.

Onto the attic, which is often one of the first places to be insulated due to one simple fact: heat rises. Most homes will have SOME form of insulation in the attic, but if it's just one layer of R-11 it might be time to step it up a notch.

You've got options, spray foam or blow-in cellulose.

Spray foaming is super efficient in an attic, but again, it ain't the cheapest.

Cellulose is another popular attic option, although I wouldn’t recommend it if you prefer to use your attic for extensive storage or go up there often.


  • Pros: Cost-effective, recycled material, great for wall retrofits 
  • Cons: No air barrier, critters can access

Alright, let’s get to the dad question…How much will all this cost?

For your average 1,500 square-foot home, here are the rough numbers.

  • Attic foam – $5,000-6,000
  • Attic Cellulose - $2,000-2,500
  • Attic Fiberglas – $1,500-1,750
  • Exterior Walls Cellulose– $3,000-4,000 (only retrofit unless gutted)
  • Exterior Walls Foam - $4,500-5,500 (If gutted)
  • Basement Walls & Sills Foam - $2,500-3,500
  • Basement Ceiling Fiberglass - $1,500-2,000

As always, get multiple quotes, negotiate, and ask if they have a cash price (NEWS CENTER Maine is owned and operated by TEGNA Inc. and in no way condones tax evasion, non-compliant transactions, or any implication of such).

If these numbers seem a little steep, remember there are significant rebates available from Efficiency Maine, up to 3,500 per home. Many contractors will complete the needed paperwork as part of the deal.

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