WHAT IS R VALUE?
THERMAL RESISTANCE RATING
In building and construction, R-value is the capacity of an insulating material to resists the flow of heat. The greater the R-value, the greater the resistance, and so the better the thermal insulating properties of the material or product. R-values are used for describing effectiveness of insulation and for analyzing heat flow across assemblies (such as walls, roofs, and windows) under steady-state conditions.
WHY DOES R-VALUE MATTER?
The standardized R-Value measurement helps ensure your residence or business reaches the desired energy and temperature efficiency. Additionally, the FTC (Federal Trade Commission) enforces the R-value Rule, which ensures that you get accurate, honest information about the R-value of your insulation before you buy it, have it installed, or buy a new home.
Manufacturers must label their packages of insulation. Installers and retailers must provide fact sheets at the point of sale and some ads. New home sellers must include this information in their sales contracts.
The amount of insulation you need depends on your climate, type of heating & cooling system, and more. Ask your insulation pro for guidance or call us.
Insulation Product Types:
Although we specialize in spray foam insulation, other types of insulation do exist. Each comes in various forms and/or with options for thickness, density, and coverage -- all affecting R-value.
Blankets are flexible products made from mineral fibers such as fiberglass or rock wool. Blankets are available in widths suited to standard spacing of attic assemblies and between floor joists and wall studs. They must be hand-cut and trimmed to fit wherever the joist spacing is such as near windows, doors, or corners. They are available in vapor and fire retardant facings.
Blown-in loose-fill insulation includes cellulose, fiberglass, or rock wool that are blown using pneumatic equipment, usually by professional installers. This form of insulation can be used in wall cavities. It is also appropriate for unfinished attic floors, for irregularly shaped areas, and for filling in around obstructions.
Spray foam insulation can be applied by a professional using special equipment to spray the foam into place. Polyisocyanurate and polyurethane foam insulation can be produced in two forms: open-cell and closed-cell. In general, open-celled foam allows water vapor to move through the material more easily than closed-cell foam. However, open-celled foams usually have a lower R-value for a given thickness compared to closed-cell foams. So, closed-cell foams are able to provide a greater R-value where space is limited. Part of the reason spray foam provides the highest R-value of any insulation option is that it forms a complete seal, stopping the flow of air -- and heat -- completely.
Radiant barriers are reflective insulation installed inside buildings to prevent summer heat gain and winter heat loss. Radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic by reflecting the heat away from the living space. To be effective, it must face an air space. Radiant barriers are more effective in hot climates, especially when cooling air ducts are located in the attic.
Rigid insulation is made from fibrous materials or plastic foams produced in board-like forms and molded pipe coverings. These provide full coverage with few heat loss paths and are often able to provide a greater R-value where space is limited. Used to insulate almost any part of your home, from the roof down to the foundation. Such boards may be faced with a reflective foil that reduces heat flow when next to an air space.
Which Insulation Has the Highest R-Value?
Honestly, it depends. Which insulation has the highest R-value depends largely on:
- Thickness and density of the material
- Age of the material (some insulation does not age well)
- If it is used appropriately
- If it is installed in a way that seals air leakage (not possible with all insulation)
- What is being insulated
For your money, we truly believe the highest lifetime R-value and best overall efficiency you will achieve is with spray foam insulation. The reasons are simple:
- High efficiency relative to required thickness; various densities offered
- Spray foam ages well
- We provide training and other resources to our contractors and partners to ensure proper installations
- Spray foam is the only insulation that creates a completely airtight seal and even fills voids between joists and wall cavities
- Spray foam can be used to effectively insulate any part of a home or business (even commercial roofs and metal buildings)
Here's an excerpt from energy.gov's information about R-Value and insulation types.
The R-value depends on the type of insulation, its thickness, and its density. The R-value of some insulations also depends on temperature, aging, and moisture accumulation. When calculating the R-value of a multilayered installation, add the R-values of the individual layers.
Installing more insulation in your home increases the R-value and the resistance to heat flow. In general, increased insulation thickness will proportionally increase the R-value. However, as the installed thickness increases for loose-fill insulation, the settled density of the product increases due to compression of the insulation under its own weight. Because of this compression, loose-fill insulation R-value does not change proportionately with thickness. To determine how much insulation you need for your climate, consult a local insulation contractor.
The effectiveness of an insulation material’s resistance to heat flow also depends on how and where the insulation is installed. For example, insulation that is compressed will not provide its full rated R-value. The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because heat flows more readily through studs, joists, and other building materials, in a phenomenon known as thermal bridging. In addition, insulation that fills building cavities densely enough to reduce airflow can also reduce convective heat loss.
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