Two Top Roof Insulation Options and Costs

If your home is located in a colder planting zone and you don’t have the proper roof insulation handy, keeping it warm can be very expensive during the long winter months. Prices for heating oil or natural gas can rise in the winter due to increased demand, putting further strain on your finances. Depending on your home size, you could find yourself burning through a lot of heating oil or natural gas. It is possible to turn the thermostat down and wear warmer clothing inside, but this can get tiring as you should be comfortable in your home. 

If you’ve got an unfinished attic or roof, giving in proper insulation is an easy way to control your heating costs and internal temperatures this season. Installing roof insulation is a project you can DIY in a weekend to get year-round savings. It can shave a decent portion off your heating bill, and it works the opposite in warmer climates. Proper roof insulation will help stabilize your home’s indoor temperatures in warmer temperatures to help keep the home cooler. 

Ideally, you’ll hire an energy auditor that can tell you how much protection you’ll get from adding roof insulation to your home. They can also give you an idea of where air leaks are so you can seal them to ensure your roof insulation works well. If you can’t afford to get an energy auditor to come in or you don’t want to wait for one, this guide is for you. We’ve picked out everything you need to know about costs, prep work, products, and more. You can read on to understand this project’s scope. 

Blown roof insulation is much quicker than batt, but you have to be comfortable using machinery to get it in. Ask a local company which type of insulation they recommend for your roof before you start your project. Roof space insulated by damian entwistle / CC BY-NC 2.0

Understanding Roof Insulation Costs

First up, how much will it cost to add roof insulation to your home? Generally speaking, you’ll pay an average of $1,700 to $2,100 for this project. The main factors that impact your roof insulation costs are square footage of your space, material and type of your insulation choice, and the insulation installer or contractor’s fee if you don’t plan on DIYing. If you have to apply roof insulation around cables or electrical panels, you may have to pull in an electrician for part of the project. 

Pick Out Your Insulation Type and Material

One of the first steps you take is to pick out your insulation type and material. For DIY-style projects, you get the choice of batt (blanket insulation) or loose fill. You can add both of them to uninsulated roofs and attics, or you can layer them over an existing roof insulation. Once you pick out a type, figure out which material prices and options are the best for your roof insulation project. Always check your labels for any specifics before you buy to prevent problems later. 

Insulation Type One – Batts

Batts are flexible roof insulation material that often comes packaged in rolls. The rolls are available in several thicknesses and widths. You can usually pick from 16-inches and 24-inches to fit between your roof’s studs or joists in the framing. Batts come with or without foil or a paper facing that works as a vapor barrier. You can stack one or more layers to get to your insulation level. 

Batts work best for roofs that have standard joist spacing, especially ones where there isn’t any current insulation. Your roof should also have very few penetrations or obstructions to work around, like skylights. You should have sufficient headroom to allow you to move when you install it, and you should be prepared to cut the material to fit around any obstructions. 

Material Option One – Cellulose 

Cellulose has an R-value per inch of 3.7 to 3.8. It’s made from fibers that get recycled from post-consumer paper. The paper gets treated for fire and insect resistance to make it better to use for roof insulation. It won’t irritate your skin or lungs, but cellulose is made by a very limited number of manufacturers. This makes it more difficult to source, and it can add to the price. You’ll usually pay between $1.00 and $1.50 a square foot. 

Material Option Two – Cotton

Cotton material has an r-value of 3.7 to 3.8, and it comes from recycled denim cloth fibers. It’s an excellent choice if you’re trying to block airflow, and it’s also good at blocking noise transmission. However, cotton is a more expensive material for batt roof insulation. You’ll pay up to $1.20 to $1.50 a square foot. 

Material Option Three – Fiberglass

This popular batt material has an r-value of 2.9 to 4.3. It’s made out of recycled sand or glass that gets melted down and spun into fine fibers. It’s very inexpensive and commonly used, but it’s easy for the fibers to irritate your skin or lungs. It’s also less effective when it comes to blocking airflow in your roof insulation. You’ll pay between $0.50 and $0.65 a square foot. 

Material Option Four – Mineral Wool

The final material option for batt insulation is mineral wool. It has an r-value of 3.0 to 3.0. It comes in fiber form that gets made out of recycled slag from blast furnaces or rock. It’s much more expensive than other options because it has naturally fire-resistant properties associated with it. You’ll pay between $1.00 and $1.10 a square foot. 

Insulation Type Two – Loose

Loose fill features insulation fibers that get packed into bags and blown in place to the desired density and depth using a specialized machine. You can typically rent one from a local hardware center. It is possible to pour loose insulation and spread it manually. However, this is a much more labor-intensive project and you’re more apt to get uneven results. 

Loose fill works best for roofs that have nonstandard or irregular joist spacing. You can fill it in around roofs with a lot of penetrations or obstructions without a problem, and it works well for roofs that have existing insulation since it fills in gaps very well. If you have limited headroom for moving around during insulation, this is a faster route. Finally, loose fill works for DIYers who want to complete the job quickly and aren’t afraid to use power equipment. 

Material Option One – Cellulose 

For loose insulation, cellulose has an r-value of 3.2 to 3.8. Just like the batt material, it utilizes post-consumer paper that has been recycled and treated to be fire and insect-resistant. It’s the most common type of blown-in material for your roof insulation, but it can easily mold or rot if it has moisture exposure. You’ll pay between $0.60 and $2.30 a square foot. 

Material Option Two – Fiberglass

The r-value of fiberglass blown-in roof insulation falls between 2.2 and 2.7. It features recycled sand or glass that gets melted down and spun into fibers. It’s lighter weight than both mineral wool and cellulose, but it will eventually settle more than other roof insulation types. You’ll have to put in a much thicker layer, and you’ll pay between $0.50 and $1.10 a square foot. 

Material Option Three – Mineral Wool

The final material option for blown-in insulation is mineral wool, and the usual r-value falls between 3.0 and 3.3. It uses fibers made from rock or blast furnace recycled slag. It gives you a natural fire resistance for your roof insulation, but it’ll cost between $1.40 and $2.10 a square foot. 

Once you decide on a type of roof insulation, you’ll have to pick out the material. Your budget will play a role here because some materials are much more expensive than others. Roof insulation by David Wulff / CC BY-NC-ND 2.0

Look at Current Insulation and Take Out Moldy Pieces

If you have existing insulation, you’ll want to find out the r-value so you know how much insulation you have to add to your roof insulation. Get a flashlight and a tape measure and see what type of insulation you have installed. Check and see how deep it is, and use the following to estimate the r-value: 

• Batts (Fiberglass) – 3.2 per inch 
• Loose Fill (Cellulose) – 3.7 per inch
• Loose Fill (Fiberglass) – 2.5 per inch
• Loose Fill (Mineral Wool) – 2.8 per inch

Pull up any moldy or decade material. If it’s water stained or compressed, it’s not useful for your roof insulation. If your home was built before 1990, look for lightweight, loose-looking, grainy insulation that contains shiny flecks. If you see it, this could be vermiculite that comes from a mine with asbestos deposits. You want to get it tested before calling a professional to come in, remove it, and dispose of it. 

Figure Out How Much Roof Insulation You Need 

Measure the square footage of your area. For loose fill roof insulation, you’ll need to read the labels to figure out how much insulation you need. Each bag has a required depth listed for the range of r-values you want to reach. They’ll also list how many bags you need to cover 1,000 square feet at the recommended depth. For rolls or batts, you can find out how much roof insulation you need by figuring out the length and width of the product you want to use. Make sure you get an extra roll or bag so you don’t run out near the end of your project. 

Take Steps to Protect Yourself

You don’t want to be uncomfortable when you’re putting in your roof insulation, and there are a few things you can do to protect yourself. They include: 

• Avoid Standing on Joists – If you lose your balance, you could injure yourself in the fall. Get a piece of plywood to stand on or a couple of wide, sturdy boards to use as a stable standing surface. Move them as you work, and you want them to span three joists for extra stability. 

• Light up Dark Corners – Get a clip-on workshop light or a portable battery-operated lantern and have them with you when you apply your roof insulation to make sure you hit all of your roof. 

• Wear Protective Gear – Make sure you wear protective gear like goggles, dusk masks, work gloves, a long-sleeved shirt, and long pants. This will help to protect your skin, eyes, and lungs from roof insulation fibers. 

Prep for Your Roof Insulation Project

In order to have a successful roof insulation project, you have to do some prep work before you start applying it. This can help keep your costs down, and it can ensure that your insulation does a good job at helping control your energy bills by regulating your indoor temperatures. 

Any gaps between your attic and roof will allow for cooled or heated air to escape out into the indoors. This makes any roof insulation you add virtually useless. You want to do the following to make your space as airtight as possible: 

• Get minimally-expanding, canned spray foam to put around any window casings in your attic. For around the jambs and sashes, use foam weatherstripping to seal any stray leaks. 
• If you have gaps around exhaust fans, wires, ducts, or pipes that are ¼-inch or less, you can seal them up with a fire-blocking caulk. Any gaps up to ½-inch should get sealed using fire-blocking spray foam. Allow it to dry. 
• Get metal flashing sealed with a high temperature caulk to seal around flues and chimneys. You can also buy a half-gallon of furnace cement to apply at just over $20. 
• Fix any roof leaks you have before you insulate. Water is the enemy of insulation because it can create a breeding ground for mildew and mold. This will ruin any air-trapping pockets that can block heat flow. Look for moldy or damp spots on your attic joists or existing insulation and water stains on your roof’s sheathing. This will clue you in to potential leaks. 
• You want to keep your attic door or hatch clear because this is direct access to your roof. Get rigid foam insulation and attach it to the attic side of the door or hatch. Add a layer of weatherstripping around the perimeter too because this can help create a seal. 
• It’s important that you box out your light fixtures. Unless you have fixtures that are rated safe to have direct contact with insulation or you’re using mineral-wool insulation, you want to box out your light fixtures. If the material covers or touches the recessed lights or cans it creates a fire hazard. Use metal flashing, hardware cloth, or scrap plywood to create a 3-inch no insulation zone around any and all light fixtures. 
• Get a utility knife or chef’s knife to cut your batts if this is the roof insulation you go with. Use a piece of plywood for your cutting surface, and stand on a scrap while you cut to get an exact edge. 
• You can get an insulated, zipped tend to keep your pull-down stairs or ladder free from drafts for just over $100 from Amazon. 
• Try to preserve your attic’s airflow when you install roof insulation. Don’t cover up the soffit vents with batts or loose fill if you stuff the insulation in among the eaves. These soffits help to keep your roof cool and prevent ice dams, so they have to stay open. Insulation shouldn’t touch your roof’s underside either. Staple sheets of plastic or foam baffles to your roof sheathing by the eaves. 

The prep work for your insulation project is essential. If you don’t prep, you could end up with crushed air pockets or moisture slipping between the layers to mold and cause problems down the line. Insulation by Bryn Pinzqauer / CC BY 2.0

Put the Vapor Barrier in the Right Place if You’re Starting from Scratch

Some batts come with a foil or paper facing that can work as a vapor barrier in your roof insulation. You can also use 6-mm polyethylene sheeting and fit it between the joists. You’ll seal the seams using foil tape to stop moisture from getting into the insulation. 

No matter if you want loose fill or batts for your roofing insulation, a vapor barrier should go closest to the warm side of your insulation. This can prevent moist, hot air from leaking in. It should face the home’s interior in cold climates and the attic’s interior in hot climates. Some areas won’t need a vapor barrier. 

Roof Insulation Tips and Tricks

When you start with this insulation project, work from the perimeter toward the hatch or door so that you don’t walk over the roof insulation you just put in. Make sure you always cover the tops of the ceiling joists because this ensures that your insulation is deep enough to reach your targeted r-value. This can also prevent thermal bridging or heat loss due to wooden framing. Once you finish, shower thoroughly to remove any left behind fibers from your skin. Wash your work clothes by themselves after you wear them once. 

Batt Roof Insulation Tips

Always get unfaced batts, including when you’re insulating your roof for the first time to prevent moisture from getting trapped between the old and new insulation layers. You can remove the foil or paper backing or buy them unfaced. You should also put a new layer of unfaced batts perpendicular to your old insulation layer. This will help cover up any gaps left in the lower layer. You should butt any adjoining batts together snugly, but make sure you don’t compress them. 

Never put heavier batts over lighter ones, like cotton over fiberglass. This will result in accidentally compressing the lower layer, and this can reduce your roof insulation’s effectiveness. Cut batts to fit around any obstructions or penetrations in your roof. Cramming or stuffing the insulation around the piping or ducts will compress any air-trapping pockets in the materials, and this reduces how effective it is. 

Don’t leave any gaps between your insulation batts and obstructions, joists, or abutting batts. Even very narrow or small gaps can help air escape. You can cut a thin strip of insulation to fit in any small gaps to seal them up. 

Loose Fill Roof Insulation Tips

Fasten your blocking around the door or hatch to let the material get installed around this area without any drafts escaping. Keep your insulation’s depth consistent across your roof. To make this process easier, try to eyeball how level your material is as you blow it in. 

To find the r-value from your chosen product, use the number of bags you calculated out that you need to insulate your space. Never use fewer. If you’ve hit your target depth with your loose fill roof insulation but you still have some bags sitting there, you want to keep adding the material to an even depth throughout the space until all of your bags are empty. To help get the correct density, hold your blower hose parallel to the joists. Blow the fill over and between the joists rather than across them. 

Check for Rebates

There are several federal tax credits for weatherizing your home, but a lot of them did exposure in 2011 regarding boosting your home’s energy efficiency. However, your state’s local utility or energy office can offer discounts, rebates, or a few other financial incentives for adding roof insulation. You can look here to get a start on this program. 

Roof Insulation Benefits

Adding roof insulation to your home is very common. No matter if you have a tile roof or a traditional shingle one, insulation can do a lot while giving you several benefits, including: 

Heat Prevention

Adding roof insulation can help to keep excess heat from getting into your home during the summer months. In turn, you can keep your house cooler and save money at the same time. This is especially true if you live in a region that has much higher and more humid temperatures during the summer months. 

Heat Retention 

Some areas in the country see significantly lower temperatures during the winter months, and keeping your home comfortable and warm is a huge battle. A lot of people utilize heaters or fireplaces to keep their homes at a comfortable temperature. Without having proper roof insulation, your heat will go up and escape through the roof and cost you money. Insulation in your roof will stop the heat from escaping, and it’ll help trap the warm air in at the same time. 

Added Protection

Insulating your roof adds another protective layer to your home. Depending on the type of roof insulation you choose, it can help shield your home from the toll being exposed to natural elements takes over the years. Repairing or replacing your roof can be a time-consuming and expensive process. So, being able to extend the life of your roof any way you can is a great benefit. 

Energy Savings

Insulation is critical for keeping the home at a moderate temperature. It means you won’t rely as heavily on central air or air conditioners or heaters throughout the year as you would have to otherwise. Your energy savings can add up all year round, and the savings can be significant. 

Where to Find Roof Insulators Near You

If you’d like to add roof insulation to your home but you don’t think you can tackle this project on your own, you want to contact local companies to get quotes. You can start your search here: 

• Batt Insulation Contractors
• Insulation Installers
• Blown-In Insulation Contractors

Frequently Asked Questions 

Before you start contacting local companies to insulate your roof, get a few key questions to ask them. Asking each company you contact will allow you to get accurate pricing and project estimates. Insulation by Jeena Paradies / CC BY 2.0

1. How thick should your roof insulation be?

By effectively insulating your roof or loft, you can cut your energy bills by a significant percent. For glass wool, it should be at least 270-millimeters thick. Rock wool should be 250-millimeters thick, and cellulose should be 220-millimeters thick. 

2. What is the healthiest type of insulation?

Ideally, you’ll use formaldehyde-free, natural materials that are eco-friendly for your roof material to help create a healthy and green home. Cotton or wool are safe to handle while causing no irritation to your respiratory tract or skin, unlike fiberglass. You will pay  more for cotton or wool though. 

3. Is it possible to add too much insulation?

Yes, you can over-insulate your roof so much that it’s impossible for it to breathe. Home insulation should seal the home’s interior without sealing it too tightly with too many insulation layers. If you do, it’s easy for moisture to get trapped between the layers and mold or mildew to form. 

Bottom Line

Roof insulation should be a priority if your home doesn’t have any or if it’s old. You can take on this project yourself, but you should also consider bringing in professional help if you’re not sure what you’re doing. You will pay more, but you’ll get professional-grade results that can help it last for years.