The purpose of any insulation is to resist the transfer of heat – That’s what the R-value of insulation is all about: How well does it resist heat moving through it? In summer, it keeps heat out; in winter, it holds it in. As a result, it increases indoor comfort, cuts energy use and lowers energy bills.
Did you know? For years, the annual Home Remodeling Cost to Value survey showed that the addition of quality insulation pays for itself more quickly than most other home improvement projects, and saves energy costs for years. For example, in a recent year, adding fiberglass insulation to the attic produced a return on investment of 116%.
There are many types of insulation, and this guide will briefly explore them all, with relative advantages and disadvantages, costs and applications.
Insulation Types, Materials, R-values and Cost
|Batt & Roll||$.90 – $1.75||3.0 – 4.3||Walls, Attics|
|Loose Fill||$.80 – $2.25||4.0 – 4.3||Walls, Attics|
|Rigid Foam||$1.65 – $2.75||4.0 – 6.5||Walls, Below Grade, Exterior|
|Spray Foam||$2.00 – $6.75||3.5 – 6.5||Attics, Below Grade, Exterior|
|Radiant Barrier||$1.00 – $1.75||Varies||Attics|
For cost, we use 500 square feet for each insulation type to give you an idea of total project costs. Prices include DIY and pro-installation costs.
Batt Insulation and Roll Insulation
Most batt insulation is fiberglass or rock wool / stone wool. Their relative strengths and weakness are listed above. The same materials used in batt insulation are manufactured in rolls too.
R-value: It starts at about 3.0 for fiberglass and rises to 4.3 for rock wool.
Installed Cost: $.90 – $1.75 per square foot or about $450 – $775 for 500 square feet.
Advantages: It is available in standard pre-cut sizes; typically, this means easy installation for wall studs, ceiling joints and attic rafters. Product and installation are relatively affordable, much less expensive than spray foam options. Custom cut batts can insulate limited and irregular spaces. Sound-dampening qualities are decent, not spectacular.
Disadvantages: May require air sealing for maximum performance. In fact, sealing spaces to prevent unwanted airflow is just as important as the insulation used. Spray foam insulation seals and insulates when properly applied. The presence of seams effects performance compared to other types of insulation. Tends to hold moisture and to allow movement of moist air. It can be susceptible to mold.
Loose Fill, Cellulose Fill and Blown-in Insulation
This popular DIY and pro-installation insulation is manufactured primarily from recycled newspaper. It an be applied dry or wet. Dry application stays loose and is suitable for attic installation. Wet application will adhere more tightly to the insulated surface, so it is ideal for wall cavities that will be covered in drywall or similar
R-value: Up to R-4.3 per inch.
Installed Cost: $.80 – $2.25 per square foot, so about $400 – $1,125 for 500 square feet.
Advantages: Performs up to 22% better than batt insulation of the same R-value, due to lack of seams that might allow airflow. Installation is faster and easier than for batt insulation, and it is inexpensive relative to some other types of insulation. Loose fill insulation has fewer health risks compared to fiberglass.
Disadvantages: Product settling may cause loss of thermal protection over the lifetime use of the product; may require “topping up” in post-installation years to improve energy efficiency. Inclined to absorb moisture, so vapor barriers are usually in conjunction with blown-in insulation. Generally requires professional installation.
Rigid Foam, Foam Board or Board-Stock
This commonly used, compact insulation is also called expanded polystyrene Board (EPS) and beadboard. The material is made from foam plastics and is a popular choice to insulate building exteriors and foundations. Can be used inside walls. Sold in rigid sheets of various sizes, it is easy to cut and fit. Foam board can be faced with foil to further improve insulation. This material is suitable for anywhere in your house.
Note: Two types of specialty rigid board insulation are produced: Extruded polystyrene board (XPS or “blueboard”) and Polyisocyanurate Board (“polyiso”). R-values and moisture resistance are higher than EPS but are the least environmentally friendly due to high use of HCFC’s.
R-value: R-4 to R-6.5 per inch depending on the composition of the foam. It offers up to R-7 when faced.
Installed Cost: Starts at about $1.65 per square foot for open-cell rigid foam board and averages $2.75 for closed-cell material. That’s $825 – $1,375 for 500 square feet.
Advantages: High R-values compared to loose fill. It is waterproof, so foam board can be buried to insulate foundation exteriors. EPS is environmentally friendly because hydrochlorofluorocarbons (HCFC) are not used widely. Rigid foam is often the greenest option. The tough material needs very little maintenance, repair, or replacement since they are rigid and won’t deteriorate.
Disadvantages: It’s more difficult to stop air infiltration with rigid insulation. Joints must be taped for the purpose. This and other challenges can make installation more expensive. The plastic construction material may break down from the UV rays in sunlight, which must be considered during storage and installation.
Spray Foam, Spray In Foam or SPF
SPF is usually manufactured of polyurethane. It is waterproof and available in open cell and closed cell options.
R-value: About 3.5 for open-cell spray foam and up to 7.0 for closed-cell foam per inch of thickness.
Installed Cost: It begins at around $2.00 per square foot for open cell SPF. Closed cell spray foam ranges from $4.00 to $6.75. That comes to between $1,000 and more than $3,300 based on the type used and installation challenges.
Advantages: Highest R-value per inch. Expands to achieve air sealing upon application, creating air and insulation barriers at the same time. Fills gaps, crevices, cavities. Water-repelling nature reduces occurrence of mold. Installs well in hard-to-reach areas. Provides excellent sound absorption.
Disadvantages: Installation is more complicated and expensive than fiberglass batts. Large scale installation requires professional handling in most cases. Improper installation requires very expensive repairs and replacement. Premium price.
Radiant Barrier, Reflective, Foil
Usually manufactured of aluminum foil or aluminized polyester, radiant barrier insulation has no R-value because it does not provide a barrier to conductive heat. It is commonly used in unventilated cavity walls, and in pitched or angled roofs. Works best with a layer of still air at least 1” between the barrier and the outside wall material.
Installed Cost: $1.00 – $1.75 per square foot, or $500 – $875 for 500 square feet.
Advantages: Effective and useful in warm climates; does not degrade due to moisture, disintegration, or compacting. Thin, lightweight, and less bulky than other insulations, reflective insulation is easy to fit and is effective as a vapor barrier. Non-toxic and non-carcinogenic radiant insulation is safer to install, and installers need less safety equipment.
Disadvantages: More expensive because it is metal based; In cold climates, in needs to be combined with other forms of insulation due to convection. Can become an electrical hazard because of metal construction. Relies on being kept clean and free of debris, which may require more maintenance for maximum efficiency.
Pro Tip: To keep a room warm, put the shiny side on the inside; reverse it to cool a room.
Acoustic, Noise Reducing or Soundproofing Insulation
This is a specialty insulation designed to reduce high volume and high frequency noise. Traditional insulation materials are often used, but Gypsum and Acoustic panels can be made from foam egg-crate materials or even compressed straw.
R-values and costs are determined by materials used and where it is applied or installed.
Home Insulation Costs by Location
This section covers locations commonly insulated, the costs and the best materials for each area.
|Walls||Batts, Rolls, Loose Fill||$.90 – $1.75|
|Attic Floors||Batts, Rolls, Loose Fill||$1.45 – $3.35|
|Attic Walls||Spray Foam – SPF||$3.90 – $6.50|
|Basement/Crawl||Batts, SPF, Rigid Foam||$0.90 – $6.50|
|Ductwork||SPF, Faced Batts||$2.25 – $4.95 / Linear Foot|
Insulation in Walls
Fiberglass batt insulation is most common and the most affordable. Blown-in cellulose is a good choice too. Rigid insulation adds thermal resistance to the foundation and exterior walls, but isn’t generally used above grade except when an old home is poorly insulated. In those cases, the foam board is attached to the exterior of the home, and siding is installed over it.
Cost: $.90 to $1.75 per square foot
Attic Floor Insulation
In most applications, cellulose insulation is “blown-in” to the depth required by local code. Rolls and batts between the joists also remain popular. We do however, cover the main types of attic insulation in our attic insulation guide.
Cost: $1.45 – $3.35 per square foot
Attic Walls and Ceiling Insulation
There’s a move today to completely seal attics – no airflow whatsoever. The trend follows the “tight house” mentality many contractors have. This 2-minute video discusses open vs. sealed attics. If you choose to seal the attic, SPF/spray foam is the only option here.
Cost: $3.90 – $6.50 per square foot.
Basement or Crawl Space Insulation
Fiberglass batts are ideal for ceilings in basements when they are insulated, which isn’t often. Spray foam insulation is popular because it prevents drafts from entering your home from the basement and resists moisture. Rigid foam board is a useful choice too.
Cost for fiberglass: $.90 – $2.00 per sq
Cost for SPF: $3.75 – $6.50 per square foot.
If your ductwork is in exposes space, such as in the attic, garage or unheated basement, it should be insulated.
Spray foam insulation can be applied to the outside of the duct, or you can wrap the duct in a foil-faced blanket made of insulating material (many products are available.) Most effective is a product known as “fiberglass duct board,” which is a stiff, foil-wrapped fiberglass insulation typically one to two inches thick attached directly to the ductwork.
Cost: $2.25 – $4.95 per linear foot.
Glossary of Insulation Terms
This glossary clarifies terms when discussing insulation types. Perhaps it will assist you as you discuss your insulation needs with a contractor.
Batt Insulation: One of the most popular types of insulation, pre-cut insulation panels, usually made of fiberglass or rock and slag wool, are used to insulate floors, walls, and ceilings. Natural cotton varieties are also available, mostly for use in acoustic insulation.
Open Cell and Closed Cell Foam Insulation: Foam insulation contains air bubbles, or “cells.” Open cells are more susceptible to moisture. Expect an R-6 value for Closed Cell spray foam insulation, and about an R-3.5 value for Open Cell.
Conductive Heat: Heat (or cold) can be transferred from one object to another by direct contact. An uninsulated interior wall will conduct inside heat to an outer wall, where it will discharge into the environment. Some types of insulation stop the transmission of heat better than others – They have a higher R-value or resistance value.
Radiant Heat: For the purpose of this home insulation discussion, consider radiant heat to be the warm air in your home, whether the heat is generated by forced-air, hydronic radiators, electric baseboards, or wood stoves; proper insulation will encourage or restrict heat transfer out of your home as desired.
Reflective Insulation: A thin aluminum layer which diminishes or prevents thermal penetration; usually used in combination with other types of insulation.
Rock (or Slag) Wool Insulation: Material woven from minerals or rocks instead of glass; see the discussion below.
Roll Insulation: Roll insulation is manufactured from the same material as batt insulation (see above), but in longer rolls. It is very useful for lining long attic floors and similar applications, and it can be cut to length as needed.
R-Value: “R” is for “resistance.” A numerical value for how well the particular material resists the transfer of conductive heat. To keep heat in the house in the winter, and heat out in the summer, material with higher R Values offers better performance. Expressed “per inch,” as in the example of foam insulation above. Closed cell foam has a value of R-6 for every inch applied.
The Difference Between Fiberglass Insulation and Rock Wool Insulation
Since these are two of the most common insulation types and there is confusion about how they differ, here is a brief explanation.
Both are made from fine strands of woven material, formed into blankets or rolls, and designed to fit into wall cavities, thermally protect ceilings, or cover attic floors. The materials require protective gear and clothing during installation to prevent unhealthy inhalation of particles.
Composition: Fiberglass strands are woven from glass; rock wool is woven from heated rock or minerals. It is sometimes called stone wool. Fiberglass contains approximately 25% recycled content, while rock wool contains up to 75% recycled content or more.
Heat Resistance: Fiberglass R-value is 2.2 to 2.7, rock wool offers 3.0 to 3.3.
Pros & Cons: Rock wool is denser than fiberglass and melts at higher temperatures, so is generally better at reducing noise and being resistant to fire. It naturally resists moisture and provides insulation even when wet (unlike fiberglass.)
Cost: Rock wool insulation costs approximately 20% more than a comparable quantity of fiberglass insulation. Details below.