Spray Foam Insulation Guides
Straight answers on spray foam insulation — open vs closed cell, cost, R-value and hiring a contractor — from the FoamMatch directory.
Open Cell vs Closed Cell Spray Foam: Which One Do You Need?
Closed cell is denser, insulates about 75% more per inch, holds up to water, and costs about two and a half times as much per inch. Open cell is the budget choice where there is room for thickness, like an attic roofline. Pick closed cell anywhere the foam could get wet or space is tight.
Updated September 11, 2026
Spray Foam Attic Insulation: Roof Deck or Attic Floor?
Put spray foam under the roof deck when your ducts or HVAC unit sit in the attic — it brings them inside the insulated part of the house. With no ducts up there, sealing and insulating the attic floor usually costs less. Either way, compare quotes by the R-value they reach, not by inches.
Updated September 10, 2026