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Insulation: Buyer’s Guide

Buyer’s Guide

Protect & Save: Buying Insulation

The insulation you select will depend on where it will be installed, whether your home is existing or under construction, your budget, and environmental concerns. All insulation’s resistance to heat conduction is measured by its “R-value.” The higher the R-value, the more insulating the material—knowing which R-value to buy is a good first step in insulation shopping.

Which R-Value Do You Need?

The California Energy Commission recommends the following R-values for different parts of your home, though you can get a more personalized recommendation using the DOE’s ZIP-Code Insulation Program. Get more accurate recommendations for your home by hiring a professional to perform an energy audit on your home:

Recommended R-Values
Location R-Value





Raised Floors


R-value recommendations and code requirements depend upon the amount of heat that typically enters and exits different parts of the home. For example, a California Energy Commission study found that a roof can reach 178°F on a typical summer afternoon. Higher R-value insulation in your roof can help prevent this heat from reaching the living spaces below.

What’s Your Type? Varieties of Insulation

No matter where you insulate, you have several options when it comes to materials. The type and the installation location determine whether you should hire a contractor or do it yourself. Insulation can be tricky to work with, and it will only yield energy-efficiency benefits if installed properly. Consider consulting a knowledgeable contractor about where and what type of insulation to install.

When choosing insulation, you now have access to environmentally sensitive options that are either recycled or have less harmful extraction methods—you may want to also consider green insulation for its health benefits. Natural fibers, like cotton batting and sheep wool batting may be less harmful than some fiberglass and mineral-wool insulations, which may be carcinogenic. The table below shows properties of the most common types of insulation.

Insulation Types: Which is Right for You?
Type Materials R-value/inch Installation method Where applicable Characteristics Green Options
Loose-Fill cellulose 3.1–3.7 Blown into place by machine. Finished walls. Unfinished attic floors and hard to reach places. Enclosed cavities. Generally installed by a contractor. Skilled do-it-yourselfer can rent a machine to blow in loose cellulose. Easy to use for irregularly shaped areas and around obstructions. fiberglass (40+% recycled), rock wool (10- 15% recycled blast furnace slag), slag wool (70% recycled blast furnace slag), cellulose (recycled newsprint)
fiberglass 2.5-4.0
mineral wood 2.4-4.0*
Blankets or Batts fiberglass 3.1–3.4 Fitted between studs, joists, and beams. Some may be formed in place. All unfinished walls, floors, and ceilings. May be suitable for a skilled do-it-yourself. Suited for standard stud and joist spacing that is relatively free from obstruction. Comes with or without vapor retarder facing. If used with facing, vapor retarder must be on the side toward the inside of the house. fiberglass (40+% recycled), rock wool (10-15% recycled blast furnace slag), slag wool (70% recycled blast furnace slag), natural fibers, cotton and recycled denim, sheep wool
mineral wood 3.1–3.4 or 4.0**
Rigid Board expanded polystyrene(beadboard) 3.5–5 Rigid board insulations are typically cut to fit and glued, caulked, or mechanically fastened into place. Polystyrene must be covered with 1/2-inch Sheetrock for fire protection. All used on exterior sheathing or basement interior walls. May be used below grade (the exterior or interior of foundation walls). Also used on flat roof and cathedral ceiling.    
extruded polystyrene (colored styrene) 5
polyisocyannu- rate (foil faced) 5.4–7.5
rigid fiberglass 4.2
Spray-In Insulation and High-Density Blown-In Products cellulose 3.2–3.7 Spray applied to surfaces. Spray applied behind a net facing. Also can be blown into cavities. Walls 40° or above for 72 hours after application. Specifically formulated polyurethane may be applied at temps below 40°F. fiberglass, soy-based
fiberglass 3.2–4.1 Ceilings
mineral wool 3.4 Other enclosed cavities such as flat roofs
polyurethane 5.4–7
Reflective aluminum foil (single sheet and multiple sheet) Varies depending on heat flow direction. Staple to studs or joists. Floors and walls. Works best when heat flow is downward (i.e., in floors). Air space between foil and adjacent surface is essential for performance.  
Others perlite   Approximately 4 or more, depending on product. Pour into place. Pour-in products are not as readily available as other insulation systems. They also allow for considerable air movement, thus reducing their performance. Urea formaldehyde is not recommended for residential applications. Perlite, vermiculite, and polystyrene beads are expensive and have lower R-value than other types of insulation. Vermiculite should not be used as the materials contains asbestos.  
Vermiculite polystyrene beads urea formaldehyde
air entrained cement Contractor-installed
other foam plastics  

* Note: at extreme winter temperatures, R-values of fiberglass and mineral wool loose-fill insulation may be reduced. ** For high density fiberglass and mineral wool. Based on:
1. Minnesota Department of Commerce Home Insulation fact sheet, as published in Rocky Mountain Institute’s Home Energy Briefs #1 Building Envelope
2. Green insulation options taken from North American Insulation Manufacturer’s Association, “Sustainability, Insulation, and the Environment” and Cellulose Insulation Manufacturers Association, “What Types of Insulation are Available?”

Use & Care

Properly installing and maintaining your home’s insulation will maximize efficiency measures. Learn more about Insulation Use & Care , where to start, and how to insulate your home from high energy costs.


If you’re thinking about making efficiency improvements, the Insulation Overview is a great place to get acquainted with the basics and your options, before you buy or install. Return to Building and Materials.

This program is funded by California utility customers and administered by Southern California Edison under the auspices of the California Public Utilities Commission.

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