Home Insulation Types and What Each One Does

What Insulation Actually Does

Insulation slows the movement of heat through your home's walls, ceilings, and floors. In winter, it keeps warmth inside. In summer, it blocks outdoor heat from entering. That single function — thermal resistance — is the basis for every material on this list.

Insulation is measured in R-value, which quantifies how well a material resists heat flow. A higher R-value means greater resistance. The appropriate R-value for any given space depends on climate zone, location in the home (attic insulation typically needs a higher R-value than walls), and local building codes. Because insulation works directly with how your home controls temperature, it's closely tied to how your heating and cooling equipment performs — see how your HVAC system actually works for that connection explained plainly.

Common Insulation Types and Where They're Used

Each insulation material has a different form, installation method, and ideal application. Understanding these basics helps you ask the right questions when planning a project.

Fiberglass Batts and Rolls

Fiberglass is the most widely recognized insulation form — those pink or yellow blankets pre-cut to fit standard stud and joist spacing. Batts are used in walls, attics, and floors. They're relatively straightforward to install in open cavities but perform best when fitted carefully without gaps or compression, both of which reduce effective R-value.

Blown-In (Loose-Fill) Insulation

Loose-fill insulation — made from fiberglass, cellulose, or mineral wool — is blown into place using specialized equipment. It's well suited to attic floors and irregularly shaped spaces where batts can't conform easily. Cellulose is made from recycled paper and treated for fire resistance. It can settle over time, which may reduce effective coverage.

Spray Foam Insulation

Spray polyurethane foam expands on contact to fill gaps, cracks, and irregular cavities. It comes in two main types: open-cell foam (softer, lower R-value per inch, vapor-permeable) and closed-cell foam (denser, higher R-value per inch, acts as a vapor barrier). Spray foam is often used in rim joists, cathedral ceilings, and areas where air sealing is as important as thermal resistance. Professional installation is standard — improper mixing or application can result in off-gassing or inadequate curing.

Rigid Foam Board

Rigid panels made from polystyrene (EPS or XPS) or polyisocyanurate provide continuous insulation with no framing interruptions. They're commonly applied to exterior walls, under roofing assemblies, and in basement walls. Rigid board adds R-value without taking up interior space, making it practical in retrofit situations. Most rigid foam requires a fire-rated covering (such as drywall) when used in living spaces — local codes vary, so verify requirements with a licensed contractor.

Mineral Wool (Rock Wool / Slag Wool)

Made from volcanic rock or industrial slag, mineral wool batts offer thermal performance similar to fiberglass but with notable fire resistance and some sound-dampening properties. It holds its shape well and is less prone to moisture absorption than fiberglass. Mineral wool is used in walls, attics, and around mechanical systems where fire resistance is a priority.

For a side-by-side performance breakdown of these materials, see insulation types compared. And if you're thinking about how insulation fits within your home's broader systems, a homeowner's map of core house systems provides useful context.