8 Things I Learned About Insulation
I went down the rabbit hole while researching insulation for my home
I recently published an article on ClimateDrift on How to make your home a climate champion, and while working on one section, I went down a rabbit hole researching insulation. R-value of insulation indicates how well the insulation resists heat transfer. Here are 8 things that I learned:
Cellulose is commonly used insulation and is typically blown into walls or attic spaces. It is made of recycled paper, cardboard, plant materials, and cloth, so a good reuse of materials to keep out of the landfills. It has an R-value of 3.1 to 3.8 per inch. Durability of this type of insulation is 20-30 years, but can break down as soon as 15 years. Also, older installations used 15 inches only and current standards are up to 38” so adding can improve the R-value for your home.
Recycled Textile Insulation: Sustainable and eco-friendly alternative to fiberglass and mineral wool is to use old clothing, carpets, and other fabric products. It has a high thermal performance (R-value of 3-4 per inch) as well as the ability to block noise. The link provided gives more detail on the process of reusing this material but it is one way to divert waste from landfills and re-use it to make homes more energy efficient. Denim has become a very specific category of recycled textile insulation, but it can be broader than that. Durability seems dependent on the fibers and how well they are kept from moisture.
Wood fibre insulation offers an R-value of 3.8-4 per inch and is used as part of External Wall Insulation (EWI) render system. It can be used in attics, or stud cavities. If it is made from local waste wood, it can be carbon negative as the wood is ground into a pulp and then mixed with binders. There is a dry or a wet process to create the insulation panels and the process makes them flame retardant, mold and mildew resistant as well as insect repellent. It’s durability is in line with that of the structure it is installed in.
HempWool is another eco-friendly insulation option with an R-value of 3.7 per inch. While hemp is fast growing, creating the “wool” is a complex process. Fibers have to be extracted from the hemp stalks in a process called retting (soaking in water to break down the plant’s natural binding agents) and decortication (removing the woody core from the hemp stalk). The fibers are then processed to create a yarn that is then woven or felted into a fabric. It is comprised of 90% hemp fiber and 8% textile fiber binder. It is stated of have exceptional durability and lifespan of up to 100 years without settling or degrading.
Fiberglass is made by melting recycled glass and spinning it into fibers then binding and baking the fibers together. It is also called glass wool and when it degrades the dust can be a health hazard. It comes in batts or can be blown in the wall or attics. The R-value varies depending on the application; batts range from 3.1-3.4 per inch, while blown in attic ranges from 2.2-4.3 per inch and blown in the wall ranges from 3.7-4.3 per inch. If installed well and protected from moisture, this insulation can last 80-100 years. However, it typically needs to be replaced every 15-20 years.
Wool is a natural fiber that can be used for insulation and has an R-value of 3.5-3.8 per inch. However, it also needs to be chemically treated to made it less appetizing to insects. Its durability can be impacted by moisture or suboptimal conditions similar to fiberglass.
Spray Foam comes in two applications. Open Cell for low density applications has an R-value of 3.5 per inch; it is used for interior walls and hard to reach areas. Closed Cell for high density applications has an R-value of 5.0-7.0 per inch; it is used for basement box sills and areas to prevent moisture. Spray foam is made of two composite materials, polyurethane and isocyanate. When these are combined, the materials chemically react to expand and harden. This chemical reaction releases volatile organic compounds (VOCs), which causes off-gassing, and it is recommended that the home be vacated for at least 24 hours for it to cure. Application on wooden structures has become an issue for mortgage companies because it can create a moisture barrier that ends up damaging wood, so in some cases, can make your home uninsurable, as well as impact resale value. Its application as sealing around chimneys, vents and other penetrations could be the best limited application. Its durability is noted to be 80 to 100 years.
Phase change material (PCM) insulation uses materials that absorb or release heat energy to regulate temperature. These materials change state from solid to liquid or liquid to gas as the temperature changes. This video by Belinda Carr can explain it much better than I can but ultimately you are reducing your energy use because this material is regulating the environment much better.
I have experienced the reduced durability of fiberglass insulation. This summer, I hired a contractor to insulate a wall behind my refrigerator. The last few winters during the freeze spells in Central Texas, the water line of my refrigerator has frozen and the wall radiates cold. When he opened the wall, he found it was insulated but the fiberglass batts had been exposed to moisture and was moldy. He removed that and replaced it with Knauf Ecobatt R-13 Unfaced Fiberglass Insulation batts which is made from recycled glass. The results were dramatic this winter - no freeze of the water line and the kitchen felt much warmer. This is just a 5 ft by 3 ft section of a wall in my house!
I am most excited about PCM insulation type and plan to add it to my attic this year after I assess where areas need to be sealed to prevent thermal transfers and confirm the depth of cellulose insulation in the attic. I am hoping to use less energy this summer because it is only getting hotter.
Let me know if this helped you and what has been your experience with any of these types of insulation.