Comparing Insulation R- Values
Insulation R-values in comparison to each other will tell you some what how they compare but when you throw in cost, application methods, safety and the materials themselves, you get a different picture. There will be places in a home where one type of insulation is better than others. There is also a grading system for insulation in which 1 is best and 3 is worst. For all examples we will use 2×6 walls unless otherwise noted.
Fiberglass batts are the oldest insulation used now and is arguably the worst. Fiberglass in a batt varies in R-value depending on what you buy, but can be up to 3.8/” (per inch). The problem is it is very hard to install them and get a 1 rating on the job because cavities are often other sizes than what batts are and when you throw in pipes and wires into that cavity it is hard to fit them around things. Energy Star homes are not done with batts. Installers vary greatly in the time in which it takes them to install them because some are more careful than others. Fiberglass batts are generally the cheapest insulation to install.
The Blow In Blanket System (BIBS) is fiberglass blown in to a certain density, tested in the field on every job, and is R-4.23/”. This is the only field tested insulation system, and it is tested to insure the R-value. When blown in it is excellent in filling the cavity around pipes and wires and is a grade 1 insulation system. It cannot settle and does not absorb water. The Passive House Institute calls blown in fiberglass the most cost effective insulation system. Passive Houses are super insulated homes that do not need a furnace to keep them warm even in our climate. This is the biggest bang for the buck in insulation. It also works well in existing homes.
Cellulose installed in walls can be sprayed in wet or installed behind mesh like BIBS. It is about R-3.5/”. When sprayed in it is wet using water and /or adhesive. Then it is supposed to be dried before installing vapor barrier and wall covering. Settling can be an issue. Dry cellulose is blown in behind mesh but has to be dense enough to prevent settling and it is then hard to install sheetrock over it. If not done correctly settling can be an issue. It has to be a minimum of 3.5# cubic foot or it will settle according to the industry standards.
Closed cell foam is the highest R-value per inch and also the costliest. R-value can be up to 6.8/” but varies from maker to maker. It also loses R-value after initial installation depending on the manufacturer, so check what cured R-value is. This is a chemical process so no one should be around when blowing the foam and for a time afterword as breathing the chemicals is not good. It is great for sealing rimjoists and other spaces where it is hard to put an air barrier up. People are getting whole homes blown with closed cell foam but for the same cost we can put together a wall with 50% more R-value.
Open cell foam is about R-3.6/”. It costs almost as much as closed cell foam in our market but still requires a vapor retarder. It is roughly the same R-value as cellulose but is way more expensive. For the cost to the benefit, personally, there is no reason to use it in our climate.