The most common and DIY-friendly insulation. Made of spun glass fibers. Comes in pre-cut batts or long rolls. Best for standard stud spacing in walls, floors, and unfinished attics.
Expands and hardens to form a rigid, highly efficient air and moisture barrier. Excellent for tight spaces, crawlspaces, and exterior walls. Usually requires professional installation.
Made primarily from recycled paper products treated with fire retardants. Usually blown into attics or existing wall cavities. Great for filling irregularly shaped areas.
Made from molten rock or steel slag. Extremely dense, offering superior fire resistance and soundproofing. Does not absorb moisture and holds its shape well in wall cavities.
Expands significantly more than closed-cell, remaining relatively soft and flexible. Provides an air barrier but allows vapor permeance. Good for interior walls and unvented attics.
Sturdy panels of polystyrene (EPS/XPS) or polyisocyanurate. Ideal for continuous exterior insulation, basement walls, and foundations. High R-value per inch with minimal thickness.
The US Department of Energy divides the country into 8 climate zones. Generally:
| Zone | Uninsulated Attic | Existing Attic | Floors | Wood Frame Walls |
|---|---|---|---|---|
| 12 | R-30 to R-49 | R-25 to R-30 | R-13 | R-13 to R-15 |
| 3 | R-30 to R-60 | R-25 to R-38 | R-19 to R-25 | R-20 or R-13+5 |
| 4 | R-38 to R-60 | R-38 | R-25 to R-30 | R-20 or R-13+5 |
| 56 | R-49 to R-60 | R-38 to R-49 | R-25 to R-30 | R-20+5 or R-13+10 |
| 78 | R-49 to R-60 | R-38 to R-49 | R-25 to R-30 | R-20+5 or R-13+10 |
Proper home insulation is one of the most cost-effective ways to improve your home's energy efficiency, comfort, and acoustics. Insulation creates a barrier that slows the transfer of heat. In the winter, it keeps the warmth generated by your heating system inside. In the summer, it prevents the hot exterior air from penetrating your living spaces, reducing the load on your air conditioning system.
Beyond energy savings, good insulation also acts as a sound dampener, reducing noise transfer between rooms and blocking outside noise like traffic. It can also help control moisture accumulation by moving the dew point within wall cavities, preventing condensation and mold growth when paired with proper vapor retarders.
The performance of insulation is measured by its R-value, which stands for resistance to heat flow. The higher the R-value, the greater the insulating power. The total R-value of a wall or ceiling is determined by the type of insulation, its thickness, and its density.
It's important to note that compressing insulation (like cramming R-19 fiberglass meant for a 2x6 wall into a 2x4 cavity) actually decreases its R-value. Furthermore, gaps or voids in insulation can severely degrade performance. Continuous insulation, such as rigid foam board applied to the exterior of the studs, helps prevent "thermal bridging" where heat bypasses the cavity insulation through the wood framing itself.
Selecting the best insulation for your project depends on several factors:
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