What Does Insulation Actually Cost?

This site does not publish a price per square foot, and you should be a little suspicious of anyone who does. Here is what actually determines the number on an estimate, so you can read a quote properly and compare two of them fairly.

What drives the price

Which measure you need

Attic loose fill is the least expensive insulation upgrade per unit of R-value gained. Injection foam in walls costs more, because it involves access, materials and restoration. Spray foam costs the most per square foot, and it is also the only thing that works in some assemblies. The right comparison is not price per square foot, it is cost against what the measure actually solves.

How much area

Obvious, but worth saying: an 1,100 square foot ranch and a 3,400 square foot two-story are different jobs. Note that attic area, not living area, is what drives attic pricing, so a single-story home has a bigger attic than a two-story of the same size and costs more to insulate up top.

Access

A walk-up attic with a floor and good headroom is a straightforward job. A scuttle hatch in a closet ceiling opening into an attic with 30 inches of clearance and a maze of bracing is the same material and considerably more labour. For wall work, a five-foot side yard between two houses changes how the access points get staged.

What is already there

Adding to sound existing insulation is cheap. Removing wet, contaminated or rodent-damaged material first is not, because it is a separate operation with disposal attached. This is the single most common reason two estimates differ by a lot, and it is worth asking any contractor directly whether removal is in their number.

Preparation work

Air sealing, baffles at the eaves to keep soffit ventilation clear, a hatch cover, and correct fire-rated detailing around flues and chimney chases are all real line items. They are also the items a cheap estimate leaves out, which is exactly why it is cheap.

How to compare two estimates

Put them side by side and check these five things:

• Is the R-value stated? Not the inches, the installed R-value. Inches without a material specification tells you nothing.
• Is air sealing included, and itemised? If one estimate includes it and the other does not, they are not the same job.
• Is removal and disposal addressed? Either it is in the price, or the estimate should say it is not required and why.
• Are baffles and ventilation mentioned? Insulation stuffed into the eaves blocks soffit vents, and blocked soffit vents cause moisture problems in the roof deck.
• Is it in writing before work starts? A verbal number that firms up on the day is not an estimate.

What reduces the number

Rebates and efficiency programs frequently cover part of an insulation project. State and utility programs change their terms year to year, so what is current is checked at the time of the assessment. See offers and programs for what runs in each service area, and financing for how people typically pay the balance.

Why the assessment is free

Because a real number needs an on-site look, and because a fair number of homes do not need much work. The honest outcome is sometimes that the house does not need the work.