Typically oil-based, high density (1.25-2 pounds per cubic foot) hard foam. It is a fairly mature product that has been out for 30+ years. Made of 2 parts, it catalyzes when mixed and cures quickly. Air bubbles inside (cells) do not burst, hence the ‘closed cell’ designation.
- Good air seal.
- Will stick to dirty surfaces.
- Low shrinkage, so it won’t pull away from edges if installed correctly.
- High R-value/inch. Reduces moisture transfer.
- Strong chemicals involved. In small quantities it isn’t a big deal, but doing whole new houses all humans are recommended to stay away for several days.
- It is oil based, so it is not very “green”.
- More expensive than all other common insulation types.
- When it cures it exerts a lot of pressure and will break drywall and bend window and door frames so they won’t shut.
- All forms are somewhat combustible.
- Occupants need to leave the home for 24 hours while product off gasses.
- Does not prevent radiant heat transfer – the primary source of heat-flow in and out of buildings.