What is the R-value for my roof insulation?
R-value of insulation is a measure of how well an object resists or material resists the conductive flow of heat also known as thermal resistance. It determines how well insulation reduces the flow of cold and heat into and out of your house. The higher the thickness per inch, greater the R-value, greater the resistance to heat transfer and so the more significant the energy and money savings. To determine the R-value for your roof insulation, you need to know the type of insulation and their thickness in your home.
Type of roof insulation:
For roof insulation, various materials are used such as Natural Wool, nitrogen-based urea-formaldehyde (UF) Foam, Fiberglass, Cementitious foam, Rock wool, Polyurethane Foam, Natural Wool, Straw Panels, and Plastic Fiber. These materials can be installed in numerous ways and are also available in different types.
Here is the R-values per inch of the most common types of insulation:
- Blown-in/loose-fill: they are small fibers or granules that can be used to fill spaces even in small spaces. Materials like cellulose, vermiculite, fiberglass, cork granules, and mineral wool are used for this purpose. R-value ranges from:
- Fiberglass (blown): 2 – 2.9,
- mineral wool (loose): 2.2 – 3.3,
- cellulose (blown): 3.1 – 3.8
- Foam (sprayed): they are available as liquid foam. Cementitious, polyurethane and polyisocyanurate foam are commonly used materials. The R-value ranges from 3.6 – 8.2
- Blankets (Rolls and Batts): they are flexible batts and rolls made of plastic, natural, or mineral fibers. They are easily fitted in joists, beams, and studs. R-value ranges from 2.9 – 3.8
- Rigid Fiber Boards: they are made from mineral wool or fiberglass. It can withstand higher temperatures, and it mostly used for roof insulation. It has greater R-value - 4.0
To select best products for your home, local climate and budget must always consider. Budget determines the quality of product you can choose best for your roof insulation. Meanwhile, evaluation of Local atmosphere is the primary factor. The weather variations widely vary the product selection since areas with greater sunlight tends to install stronger and high-quality roof insulations. However, higher altitude areas do not always require roof insulation unless they are prone to sunlight exposure.
Recommended Insulation by Climate Zones:
Zone 1: High humidity summer, warm winter – ceiling R-value: R-30
Zone 2: Warm, humid summer, mild winter - roof R-value: R-38
Zone 3: Hot dry summer, warm winter - ceiling R-value: R-38
Zone 4: Hot dry summer, cold winter - ceiling R-value: R-49
Zone 5: Warm temperate - ceiling R-value: R-49
Zone 6: Mild temperate - ceiling R-value: R-49
Zone 7: Cool temperate - ceiling R-value: R-49
Zone 8: Alpine - ceiling R-value: R-49
To find an average R-value for your roof, you only have to divide the recommended R-value of your region by the R-value of your particular insulation type. Moreover, to find the R-value of the installed roof insulation, multiply the R-value of your specific insulation type to the number of insulation inches.
Warm Climates (R-30 to R-49):
- Cellulose (blown): 11” – 13”
- Fiberglass (blown): 14” – 18”
- Mineral Wool (loose): 12” – 18”
- Foam (sprayed): 5” – 11”
- Blankets (Rolls and Batts): 11” – 14”
Moderate Climates (R-38 to R-60):
- Cellulose (blown): 13” – 16”
- Fiberglass (blown): 14” – 18”
- Mineral Wool (loose): 15” – 22”
- Foam (sprayed): 6” – 14”
- Blankets (Rolls and Batts): 13” – 17”
Cold Climates (R-49 to R-60):
- Cellulose(blown): 14” – 18”
- Fiberglass(blown): 19” – 25”
- Mineral Wool(loose): 17” – 25”
- Foam (sprayed): 7” – 15”
- Blankets (Rolls and Batts): 14” – 19”
There is no standardized insulation required for a particular area. Various factors evaluate the need and requirement of insulation, such as sun exposure, climatic zones, and geographical locations. Determining R-value for the insulation of your building is an essential factor as it helps in installing right type of insulation for the roof of your house. The material used in the kind of insulation varies with temperature variants. This information will surely help in getting the perfect insulation for your roof that withstands heat, cold, or moist.