Northeast Nebraska and Candelaria Philippines | Eddie, You have to understand how the foam is "completely adhered" to the metal. The bond is so strong, it's like they become one. The foam will seal every fastener. It sprays on as a liquid and expands to a solid. It will incase every fastener so no water will be able to get in even if a fastener becomes loose.
Jake, You are 100% right, spray foam will be double to triple the cost of fiberglass. It sounds like you did good sealing everything up, however most homes built 40 years ago were insulated with fiberglass too. I bet most 40 year old homes with fiberglass are losing lots of heat. Did you put the plastic between the metal and insulation? Are you sure there isn't condensation between there? Also R value does only measure heat loss by conduction. You can get convection currents within the insulation batt and that is not measured. You could have R100 and it wouldn't mean diddly if any air is leaking.
Often times, it comes down to eye appeal. If you are wanting to line your walls with metal, it would cost the same as spraying foam and coating it. However, some people do not like the look of foam so they want it covered. This is where the expense adds up.
One other important factor is called "racking load" This is a measure of strength of a wall. Most buildings are designed to resist wind uplift in the 300-400 lbs per square foot. When coating the building with 2 inches of 2 lb closed cell foam, the wind load can be more then doubled. |
Closed Cell Spray Foam Insulation
