OPEN CELL FOAM
This type of insulation has a sponge like appearance and it is commonly used on indoor jobs, offers a great resistance to heat flow. It does not shrink, sag or settle over time.
Open cell polyurethane spray foams are much less common because they were originally manufactured by only one company, and their R-values are much fewer than those of closed cell sprays. However, as their strengths were discovered, other companies began using them. Installation is similar to that of closed cells, but the effects are different. Open cell foam sprays expand once applied, allowing them to be installed in hard to reach, out of the way nooks and crannies. This includes wall and ceiling cavities that can be difficult to seal with closed cell foams. The expansion feature will hermetically seal the area and provide proper insulation. However, the R-value of open cell polyurethanespray foam is lower, in the 3.8 per inch range. This means its heat resistance level is lower, which can cause insulation failures in extreme temperatures. Because open cell foam is still very dense, it provides good insulation. Open cell spray foam does not have water resistance, though, and its lower strength provides less support to walls. It is also more permeable to vapor and air, and lower noise frequency ranges.
Another positive attribute of open cell polyurethane foam is its cost. Because of its disadvantages compared to closed cell foam spray, it is more affordable. This can be a great boon when an application does not require airtight seals and hermetic moisture prevention. Caution needs to be taken, though, that the less expensive alternative does not lead to more expensive repairs in the future. Establishing the needs of a given application are important before choosing which foam spray to use.