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Can I put insulation under my roof?

Author

David Richardson

Updated on March 03, 2026

Can I put insulation under my roof?

Yes. If you're laying insulation between the joists, the roof space will become extremely cold in winter. However, if you insulate between the rafters rather than the joists of your attic, the space will be warm and your pipes should be fine.

Likewise, should you insulate the underside of your roof?

If it does not need to be heated, it is best to keep it outside of the protected volume. You can do this by insulating the attic floor. But the best solution is actually to insulate both the attic floor and the underside of the roof.

Beside above, is it better to insulate ceiling or roof? Ceiling insulation can also be significantly cheaper than roof insulation, and can be more easily achieved without professional help. It can be difficult to access the roof space where insulation is needed, so loose-fill insulation installed by a professional is commonly used in this case.

Besides, can you insulate roof rafters?

Insulating between rafters will do no good, because the attic should be ventilated, and the rafter insulation would be between two unheated spaces. You can add insulation to the floor; the more the merrier. Also, make sure the attic is well ventilated. Cold roofs prevent ice dams.

Should I remove old insulation from my attic?

According to ENERGY STAR®, you can put new insulation over old insulation, “unless it is wet. “Faced” insulation should not be placed on top of existing insulation in the attic. Any new roll or batt insulation installed over existing insulation in the attic needs to be without a vapor retarder (face).

How much heat is lost through the attic?

A poorly insulated attic can result in 25% heat loss in fall and winter—that's 25 percent of your average heating costs going toward energy that won't even heat your home. Don't think you're safe just because you saw the insulation in your attic the last time you peeked.

Does roof insulation make a difference?

Types of insulation
If your ceiling or roof has no insulation, you can lose around 40% of your cooling and heating energy. Insulating your veranda roof in hot climates reduces heat, which affects the area below it. Insulation may benefit you if you are cooling and heating your veranda or garage.

Should you insulate attic roof rafters?

In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below. If the air distribution is in the attic space, then consider insulating the rafters to move the distribution into the conditioned space.

What is the best insulation for roofs?

Batts or blanket insulation are the best choice for ceiling insulation if you have a flat ceiling and pitched metal or tile roof. The range of batts and blankets that may be suitable for ceiling insulation include; polyester, natural wool, glass wool and rockwool.

How do you insulate an unvented roof?

Unvented roof assemblies should be insulated either with air-impermeable insulation (rigid foam or spray polyurethane foam) or with a combination of foam and air-permeable insulation. If you don't want to use SIPs or nailbase, there are four basic approaches.

Is roof insulation necessary?

It is important that the roof cavity be totally air sealed from the conditioned space below to prevent moisture intrusion and roof degradation. Foil-faced batt insulation is often used in cathedral ceilings because it provides the permeability rating often required for use in ceilings without attics.

How do you insulate heat from a roof?

Aluminium thermal insulation works on the radiant barrier principal – it reflects sun rays back to the atmosphere and works in both hot and cold weather. During summers, the roof transmits heat inside the house. With the installation of aluminium foil, the heat is reflected instead of being absorbed by the ceiling.

Will insulating my attic make my house cooler?

The first way insulating material cools a home is by not letting it get too hot in the first place. However, insulating the attic also prevents cool air from escaping because it reduces the movement of air, also called convection. Overall, the average home can save 10 percent on cooling by insulating the attic.

How do you insulate a roof from the inside?

2. Warm loft. An alternative way to insulate your loft is to fit the insulation between and over the rafters – these are the sloping timbers that make up the roof itself. You can use rigid insulation board, carefully cut to size, or you can have foam insulation sprayed between the rafters.

What type of insulation is best for attic?

Cellulose is the most effective material and has an R-value of 2.2 to 3.8 per inch, but if exposed to moisture it can get moldy. This type of insulation can be purchased online or at Home Depot and spread manually, or you can rent an easy-to-use machine that blows it in place, which will cost about $100 per day.

What material is used for roof insulation?

The most common types of materials used for loose-fill insulation include cellulose, fiberglass, and mineral (rock or slag) wool. All of these materials are produced using recycled waste materials. Cellulose is primarily made from recycled newsprint. Most fiberglass products contain 40% to 60% recycled glass.

Can you lay insulation over electrical wires in attic?

If there is not anyinsulation in your attic, fit the insulation between the joists. Don't compress the insulation to fit behind pipes or wires. Instead cut to the middle of the batt's thickness so you have a flap under the wire and one over the wire.

How much does it cost to insulate a 1500 sq ft house?

Cost: Blown-in insulation is perfect for the weekend warrior looking to get the job done cheaply. There is little learning curve involved with the application, and a DIY job will cost you about $500. Calling in the pros, on the other hand, will run you about $1,500 to $2,000 for an average 1500 square foot home.

Can you have too much insulation in your attic?

There's really no such thing as "too much insulation." It is more likely that your attic is not ventilating properly, resulting in warmer air on the 2nd floor and an overheated attic. If you live in a newer property, the answer is realistically, you can install as much insulation as you like.

Can attic insulation touch the roof?

The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams, and the material will block that flow. For the same reason, insulation shouldn't touch the roof's underside. Staple plastic or foam baffles to the roof sheathing, near the eaves, to keep the material away.

How do you insulate open ceiling rafters?

If your structure does not need to be well insulated, you can simply sandwich a layer of aluminum foil insulation or rigid foam between your finish ceiling and a layer of sheathing. Place the sheathing layer on top of the insulation and secure it with nails that pass through the insulation into the rafters.

How thick should rafter insulation be?

Common rafter depths range from 100 mm to 200 mm. This means that, all measurements considered, the maximum thickness of the insulation would be limited to a thickness of between 50 and 175 mm.

How do you expose rafters and still provide insulation?

If your structure does not need to be well insulated, you can simply sandwich a layer of aluminum foil insulation or rigid foam between your finish ceiling and a layer of sheathing. Place the sheathing layer on top of the insulation and secure it with nails that pass through the insulation into the rafters.

What is the correct amount of insulation for an attic?

The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

Is ceiling insulation important?

Since heat rises you will lose the majority of heat from your home through the attic if you do not have it properly insulated. Your attic should be cold in winter because the insulation that you have on the floor prevents the heat from penetrating through the ceiling.