Insulating your roof or attic space is going to be a necessary task in almost any climate. Doing so with high-grade insulation materials is a great way to reduce energy costs and keep your living space at a pleasant temperature year-round. Here, we’ve outlined the different types of insulation to make your choice of material easier, the positives and drawbacks of each insulation type, how much insulation costs, and how to choose the best insulation for your roof and attic.
Roof Insulation Costs and Benefits By Type of Material
Once your roof assembly has been completed, you’ll have plenty of insulation options to place under the roof decking in your attic. When combined with your roofing system, these insulation options should provide varying degrees of protection from the elements. Each insulation type here has varying costs and R-values — or resistance to heat flow.
When examining your recommended R-value, you’ll have to take your local weather patterns into account, along with the existing architecture of your home. Colder climates and older construction typically require more added resistance to heat loss.
Follow this link for a full explanation of recommended R-values by region. For reference, commonly-recommended roof R-values are 30, 38, and 49, depending on the region.
Spray Foam Insulation
Spray foam insulation is one of the most commonly used roof and attic insulation types. Unfortunately for DIYers, this insulation type requires professional installation.
This video from Inside Lighthouse is a great beginner’s guide that should help you tell the differences between the two types of spray foam:
Spray foam insulation comes in two basic types. They are:
- Open-cell: Open-cell foam is the less dense of the two options, at about half a pound per cubic foot. It is typically used for insulation in southern areas and warmer climates due to its lower R-value.
- Closed-cell: Closed-cell foam is the sturdier of the two and has a much more high-density structure, with some rigidity and a higher R-value.
Both spray foam insulation forms will cost between $1,500 and $1,800 before labor. These averages reflect a cost of between $0.50 and $1.50 per board-foot — that is, one square foot of roof decking covered with an inch of material.
Labor costs range between $1.50 and $5 per board foot. Assuming a roof with 1,500 square feet of space, you’ll be on the hook for $2,250 to $7,500 for labor alone.
Their different densities give open and closed cell insulation different R-values. Open-cell foam is better for warmer climates, while closed-cell is highly recommended for cold weather.
- Open-cell: Open-cell foam has an R-value of 3.8 per inch.
- Closed-cell: Closed-cell or rigid foam insulation has an R-value of 7 per inch.
Generally speaking, spray foam insulation is one of the best options for both warm and cold climates. The application techniques used by contractors mean that this insulation fully adheres to every corner of your substrate and joists, which can eliminate the need for any kind of vapor barrier. This provides maximum efficacy when shielding your home from temperature changes.
Batts and Rolls Insulation
Both roll and batt insulation come in varying thicknesses. Other common materials for this kind of blanket insulation are mineral wool, plastic fibers, and more natural fibers. The main attraction for clients is that these insulation materials are usually flame resistant and are easy to install without the benefit of a contractor.
Though made of the same material, this type of insulation comes in different cuts with varying thicknesses between 3.5 and 12 inches. Batts come in varying square or rectangular cuts, which make DIY installation easier.
Rolls come in the same range of thicknesses but are better suited for applying insulation to larger areas.
- Batts: $0.15 to $0.60 per square foot
- Rolls: $0.80 to $1.00 per square foot
The standard R-value range for batt and roll insulation is between 2.9 and 3.8 per inch. Certain high-density fiberglass can reach R-values of 4.3 per inch, making the thickest varieties sufficient for most climates.
Fiberglass insulation is a prime candidate for many budget-conscious or DIY clients. Along with this, it offers the following benefits:
- Increased energy efficiency throughout the home
- Reduces outside noise
- High R-value with thicker layers
Foam Board Insulation
Foam board insulation is made of either polyurethane, polystyrene, or polyisocyanurate and offers a fairly high R-value for its thickness relative to other insulation types. In order to meet building codes, this type of insulation has to be coated in a half inch of gypsum sheathing or other similar fire-resistant material.
Foam board insulation is fairly reasonable but can run a little high for some clients’ tastes. It is most commonly sold in four by eight-foot boards and comes in at $0.25 to $1.50 per square foot. As a DIY option, it’s fairly easy to install due to its rigidity and the ease with which you can cut it to fit any space.
Depending on the manufacturing technique, the R-value for foam board insulation ranges between 3.6 and 5.8 per inch.
- EPS: Expanded Polystyrene Insulation, or EPS, is made from 98% trapped air. This makes it an efficient insulation board type and gives it an R-value of 3.6 to 5 per inch.
- GPS: Graphite Polystyrene Insulation is another closed-cell insulating product with a distinctive gray color. R-values tend to be locked in between 4.7 and 4.9 per inch.
- XPS: Extruded Polystyrene Insulation is a type of closed-cell insulation product. The trapped gas used to aid in insulation can weaken the R-value over time, but this still has a minimum insulation factor of 4.7 per inch.
- Polyiso Board: Polyisocyanurate is the kind of rigid foam insulation most commonly used in roofing applications due to its high R-value of 5.8 per inch.
Foam board types comprise one of the more versatile insulation systems available. Benefits include the following:
- Both DIY and professional installation are available: While you’ll have to look into building codes in your area, DIY installation is a perfectly viable option with foam board insulation.
- Prevents moisture accumulation: While foam boards aren’t necessarily water resistant, they help to maintain a warm enough temperature in the interior of your attic space to prevent condensation buildup.
- Shields against airflow: This is far more true with professional installation, but foam board can work to prevent airflow and air leaks into your home. Since it can be cut to fit nearly any space, it will act as a secondary barrier in the event of structural gaps in your roofing substrate.
Loose-Fill or Blown-In Insulation
Loose-fill insulation is sold in bags of loose fibers which can be made to fit nearly any gap in walls or ceilings. Though the technique for a proper application requires professional assistance — especially for more difficult-to-reach areas — it is an excellent choice for filling in space between ceiling or roof joists and wall studs to further insulate your home.
Loose-fill insulation comes in three main types. They are as follows:
- Fiberglass: Made from spun-glass fibers, this blown-in insulation provides a cheap but low R-value.
- Cellulose: Cellulose is made from processed recycled materials such as cardboard and shredded paper. It’s also treated to be resistant to both fire and mold.
- Rock wool: This is a byproduct of the iron smelting process and is the most high-end option for blown-in insulation.
This insulation is sold in large bags. Each bag can cover varying areas of space in a blanket six to seven inches thick.
- Fiberglass: This is the most affordable option and checks in at $40 to $50 per bag. Assuming a layer around six inches thick, a single bag can cover around 100 square feet.
- Cellulose: Cellulose insulation typically costs between $14 and $17 per bag, which can cover around 30 to 40 square feet.
- Rock wool: This is the most expensive option available, with bags costing between $70 and $75 for 60 square feet of coverage.
- Fiberglass: 5 per inch
- Cellulose: 7 per inch
- Rock wool: 3 per inch
Blown-in insulation has a number of applications and can decrease utility costs and heating bills long-term. Aside from being a relatively easy insulation type to install on your own, it can provide a natural noise barrier, an efficient guard against condensation, and flame-resistant shielding for your roof.
Reflective insulation is a thin tin-foil-like layer that is most widely used in hotter climates. It works by reflecting radiant heat outward — or inward on colder days. This is one of the most pliable insulation forms, making it fairly easy for DIY clients to work with.
Reflective insulation is sold in large rolls at either 24 or 48 inches in width, with total square footage ranging greatly. When purchasing 200-square-foot rolls, you’ll usually pay around $0.40 to $0.50 per foot. Buying in greater bulk can get you even lower rates.
With foil insulation usually coming in at 3/8 per inch, you’ll see an R-value of around 1.0 for most brands. Many homeowners elect to use it as a supplemental layer on hard foam insulation rather than a standalone solution for their insulation needs.
Reflective insulation is one of the easiest materials for DIYers to work with. It is effectively waterproof and totally non-toxic, which makes it a great choice.
Structural Insulated Panels
Rather than a separate insulation technique or material, Structural Insulated Panels, or SIPs, are a fully-insulated construction material used largely for private residences. They are padded with oriented strand boards on either side of rigid foam insulation.
Costs for this form of insulation can vary greatly. Given its sturdiness and integral nature to the structure of some new-construction homes, you should expect to pay a premium regardless. The cost per square foot will depend on panel thickness, which can range between four and 13 inches.
Exact costs typically run between $10.50 and $15 per square foot, with panels sold in sizes ranging from 4’x8’ to 8’x24’.
R-value will also have a relatively wide range, which will once again be dependent on thickness. With boards of 7/16” on each side of panels, R-value can range from 13.9 at 4.5” of total thickness to 41.8 at 12.5” thick.
Structural panels have to be built into a structure to be a cost-effective and viable option for insulation. They’re fairly common in newer construction, and once in place, they can last up to 60 years. Many who have their choice of insulation types choose these for the following reasons:
- Improved home air quality
Concrete Block Insulation
Concrete block insulation refers to the process of either filling in gaps in an existing concrete wall or covering the exterior or interior surface with insulation. Using cover board on either wall is definitely the superior method between the two. Since concrete is a fairly heat-conductive material, rigid foam insulation is a far more efficient insulation technique.
Eight-inch concrete walls have a typical R-value of 2 – 2.5, which makes unfinished blocks more than suitable for basements without insulation.
Assuming foam board insulation, you’ll pay between $0.25 and $1.50 per square foot for materials alone. That said, a DIY installation is a viable option for this kind of insulation.
R-values for rigid foam insulation are listed above. When secured with foam-safe glue to concrete blocks, they form an efficient barrier for any purpose.
Spray foam insulation will have varied R-values, depending on the kind of foam used. Open-cell has an R-value of 3.7, while closed-cell foam has an R-value of 7 per inch. The benefit of this type of insulation for concrete blocks is somewhat negated by the fact that you’ll only be able to fill the cores of the blocks in question, which leaves some potential for heat conduction from exterior to interior.
Concrete block insulation is commonly seen in finished basements but is necessary for any main living space in a concrete-construction home. Concrete makes for a poor insulator on its own and will likely require a rigid foam board on the exterior or interior wall in order to make for a more energy-efficient home.
Brick is a fairly poor insulator on its own, with R-values ranging between 0.1 and 0.2 per inch. Thusly, bare brick construction will require insulation of some kind if there is no additional buffer between the interior and exterior of your home.
The most commonly used types of insulation for brick walls are the above-mentioned XPS and polyiso rigid foam materials. For actual living spaces, these insulation types will provide ample coverage.
Rigid foam will cost between $0.25 and $1.50 per square foot of material, depending on thickness and R-value.
Costs for spray foam materials alone will range between $0.50 and $1.50 per board-foot (one square foot covered by an inch of material). Additional coverage and professional application are recommended, which could cost up to $5 per square foot, depending on coverage level.
While open-cell and closed-cell spray foam insulation have varied R-values between 3.7 and 7 per inch, application ability to brick walls or within hollow bricks is fairly limited. You’ll likely have to go with rigid foam insulation, which will have R-values between 3.6 and 5.8 per inch.
Given the poor insulation qualities brick exhibits on its own, the application of extra layers will be a must to ensure proper energy conservation in your home.
What is the best insulation for an attic?
To our thinking, spray foam insulation is the best option for your attic. The application process will maximize the air sealing capabilities that most insulation types promise while providing comprehensive coverage for all corners and odd spaces. You may need to hire a contractor or roofing or insulation professional to help with the application process, but the added cost and versatility of this insulation type are well worth it.
Should You DIY or Hire a Contractor for Roof Insulation?
This depends entirely on the type of insulation you use. Blown-in or spray foam insulation should definitely be done by a licensed professional. They have the necessary tools to get the job done properly, as well as protection from hazardous particles which could spread through the air in the workspace. All necessary tools are easy to purchase or rent from most major hardware stores, but if you’re on the inexperienced side, you would be well-served to at least get a quote from a pro.
Frequently Asked Questions
What is the best loose-fill or blown-in insulation?
Your best choice for loose-fill insulation is cellulose. With an R-value of 3.7 per inch, it will provide you with the most protection of any blown-in insulation type.
What is an air gap for roof insulation?
Between insulation layers and your roof decking, air gaps of 1/2” to 3/4” are recommended. When outside temperatures greatly diverge from indoor temperatures, condensation can form between the insulation and outside-facing materials. Over time, this can cause water damage or mold buildup. A large enough air gap will allow for this to dry before it causes any damage.
How long can I expect most roof insulation to last?
The typical effective lifespan of any roof insulation is 15 to 20 years. Structural panel insulation has a far longer shelf life, but separately applied insulation types are likely to degrade far quicker. You should inspect your roof insulation every 10 to 15 years to be sure of its efficacy.