In any boat, whether we sail in a tropical or arctic climate, insulation is an important expedient to keep the interior cool or warm and dry. In addition to the obvious comfort factor, insulated pipes and ducts also have the potential to reduce maintenance problems and cost by preventing condensation. A well insulated metal boat hull acts as an air and vapour barrier to the interior, keeping moisture from condensing on the steel surface and running down to rust it or rot the wood (see PS Tests: Insulation and Hull Corrosion).
There are a number of ways to insulate a vessel, including using fiberglass sheets or woven roving, but the best method is spray-in-place polurethane foam. Known by different commercial names, including Handi-Foam, this closed cell insulation can be shaped and formed to fit into corners and tight spaces. It bonds directly to the metal or wood shell of a boat, leaving no air gap that can trap moisture that might otherwise erode the underlying steel or rot the wooden core.
Spray foam is easy to apply and does not require a separate adhesive. However, it does require accurate measuring and cutting to size, which can lead to waste and may not do the job as well if done poorly. It is also dangerous to work in enclosed spaces where it contains solvents, so always ventilate and use a respirator when applying contact cement (see Best Respirators for the Boatyard). Spray-in-place insulation does not need to be vapour sealed because it seals directly to the metal or wood shell. However, if the foam is removed periodically for inspection and maintenance it is important to leave a decent gap large enough to allow condensation to run down the plating or through some limber holes into the bilge. agricultural spray foam insulation