Like with most construction materials, there are a number of options to choose from. At TimberHomes, we believe that cellulose and mineral wool are the best options for most applications. In arriving to this conclusion, we considered the balance of a number of factors including R Value, embodied energy, health, and fire hazard.
R-Value is a determination of a material’s thermal resistance. In other words, it is the rating of how well a product can stop the transfer of heat. Measured by the inch of insulation, the higher the number, the better it performs in terms of R-Value. A quick web search will reveal that foams generally have the best performance, with Polyisocyanurate (foil faced) leading the pack with R-Values as high as 8.
Despite the superior R-Value, foam has a number of drawbacks. Important to us is its level of embodied energy, or the energy needed to produce it. Foam contains little to no recycled materials and require large amounts of energy to create. By most estimates, foams are off the charts in comparison to cellulose (75-85% recycled paper) or mineral wool (up to 85% recycled material).
Health is another issue to consider when trying to decide which insulation to use. Foams consist of a number of chemicals whose side effects are being called into question. With today’s emphasis on well air sealed, “tight” homes, one should stop to consider why would you surround your living space with hazardous toxins? While both cellulose and mineral wool are similarly treated with fire retardants and pest control substances, it is recognized that they are a healthier options to foam.
The petrochemical composition of foam is large question mark in terms of flammability. The recent fire at the Grenfell Tower in London is a stark reminder of what can happen even with foam that has been treated with fire retardants. Cellulose and mineral wool again fare much better.
Finally, cost is an important consideration when choosing the right material. While installation costs can vary with installation techniques, cellulose and mineral wool seem to outperform foam in most cases.
While we at TimberHomes continue to be suspicious of pretty much all building products and the materials used to make them, it seems to us that in terms of insulation, cellulose and mineral wool are the best options that are readily available in today’s marketplace.