Methodology

We do not copy install prices from other sites. We build them from parts you can look up yourself. There are three parts. First, the pay rate for insulation workers in your state, from the Bureau of Labor Statistics (job code SOC 47-2131). We name the survey year. Second, how much attic one bag covers, from a maker's own chart for a named product. Third, what that bag costs at a store, on a date we give.

Two parts are our best guess, not a looked-up number: what a worker costs a company on top of wages, and how many hours a crew needs per thousand square feet. We mark those as estimates every time they show up. You can see the whole model, part by part, on the Insulation Cost Index.

Every number we use is tagged one of four ways. Measured means we got it from a named source. Derived means we did the math on measured numbers, using a rule we state. Estimated means it is our best guess, and we say so on the page. Open means we have not pinned it down yet. An open number never goes on the site.

A few prices sit outside that model. Removal is one. Those come from ranges that contractors publish, and we give the year. When a price works that way, the note at the foot of the page says so. If we cannot show where a range came from, we do not print it.

We trust these sources, roughly in this order:

• U.S. government agencies. The Department of Energy, the Environmental Protection Agency, the Centers for Disease Control and Prevention, and the Occupational Safety and Health Administration
• Building codes and agreed technical standards, such as the International Energy Conservation Code and ASTM standards
• A maker's own technical sheets, when the question is about that product
• Industry groups. We label these, because they are not neutral

Some advice is a judgment call, not a rule. When it is, we say it is our view. And when the rules differ from state to state, we say that too. We do not smooth it over.

• We do not make up writers, job titles, licenses or awards.
• We do not print reviews, star ratings or quotes from happy customers. We have no real ones.
• We do not pass off stock photos as our own work or our own crew.
• We do not claim years in the trade that the company behind this site has not put in.

Every page shows a "last reviewed" date. It is a real date, from a day someone checked the page. It is not a clock that ticks itself forward.

Found a mistake? Tell us: [email protected]. The page gets corrected. And if the correction would change what you decide to do, we write down what changed. We do not edit it quietly and hope nobody noticed.

Insulation prices change from place to place. Our ranges cover the whole country. So a range is wider than the price in your town. We would rather give you a wide range and say why than give you one sharp number that is wrong almost everywhere.