The Four Kinds of Insulation, Compared Plainly
Almost every insulation decision comes down to four options: fiberglass, reflective, spray foam, and foam board. Each one is great at something and bad at something else. This page tells you which is which — without steering you toward whatever we sell.
How Buying Works — Three Steps
We sell fiberglass. This page will still tell you when to buy something else.
Most insulation sellers earn more by keeping you a little unsure. Push the highest-margin product, downplay the other options, hope you don't have a friend in the trade. That works — until you do the reading and realize the store you trusted was picking your product for their reasons.
This page is the reading. Look at the table, use the picker, and if the honest answer for your build is spray foam or foam board or a foil barrier, we will say so plainly. Fiberglass wins most metal-building, pole-barn, and commercial jobs on its own merits — we don't have to oversell it. When it isn't right, we would rather send you toward the right product than take your money for the wrong one.
Read the one that sounds like your project
Steel frame, purlins overhead, roof goes on soon. You want the ceiling done at the same time.
Pick: Vinyl-faced fiberglass rolls. Almost always the right answer here.
Cathedral roof, cantilever, cold-climate rim joist — anywhere the seal between warm and cold matters more than the price per foot.
Pick: Closed-cell spray foam. Costs more, but worth it here.
You want a continuous sheet of insulation on the outside of the framing — a thermal blanket that covers the studs themselves.
Pick: Rigid foam board. This is the one job it's built for.
Texas, Arizona, Florida. Metal roof cooks in the sun and radiates heat down into the space below.
Pick: Reflective barrier plus fiberglass. Neither alone is enough — they work together.
The Four Kinds, at a Glance
Every number below is the industry-average figure. Wider ranges mean the answer varies with the exact product.
*Sellers sometimes label reflective as “R-15 equivalent” or similar. That number only holds up in a lab, with a specific air gap on the shiny side and specific temperatures. In real buildings, that gap often gets lost. Treat reflective as a helper for fiberglass or foam — not a replacement.
Pick one to read
Each guide covers what the material is, where it wins, and where it’s the wrong tool.
Fiberglass
Rolls, batts, and blown-in. Non-burning, quiet, cheap, lasts a century. The default for metal buildings, pole barns, and most home walls.
Read the fiberglass guide →Reflective
Foil barrier that bounces radiant heat away. Genuinely useful in hot climates, paired with fiberglass. Sold as a stand-alone by some retailers — that’s misleading.
Read the reflective guide →Spray Foam
Sprayed on wet, expands, hardens. Insulates and seals air leaks in one step. Worth it for tricky shapes; overkill in a simple metal building.
Read the spray foam guide →Foam Board
Sheets of hard foam — three kinds (EPS, XPS, polyiso). Best as a continuous layer on the outside of the framing. Not the tool for filling cavities.
Read the foam board guide →Already know fiberglass is right for you?
Get your price in under a minute. Type your square footage, R-value, and delivery state — we show the mill’s rate, freight to you, and a fair-fee range you can pick from.