What is the difference between roof insulation and attic insulation?

Author: Lindsay Prohaska  |  Last update: Sunday, December 21, 2025

Attic insulation goes in the floor of the attic to keep the rooms below warm and cool (during the summer and winter respectively), while roof insulation goes on top of the roof deck and keeps the attic cool while preventing excess heat loss.

Is roof insulation the same as attic insulation?

Roof insulation provides whole-home temperature control and is ideal for homes with converted attics or complex roof structures. Attic insulation, on the other hand, offers a cost-effective solution, focusing warmth and energy efficiency on the main living spaces below.

Is roof insulation the same as ceiling insulation?

Ceiling insulation usually refers to insulation that is installed between the ceiling rafters. Roof insulation means insulation that is installed under the roof materials.

Is room in roof insulation the same as loft insulation?

This type of insulation replaces the loft insulation normally seen in an unconverted space. Installing adequate insulation helps keep your roof space warm and liveable, reducing the amount of money that needs to be spent on energy bills.

Can I insulate the roof in my attic?

Should you insulate your attic roof? Insulation is a wise choice to increase the energy efficiency of your home. Quality insulation will make it more cost-effective to heat and cool your home, The Department of Energy's estimates range from a 10% to 50% savings, depending on several factors.

The Best Home Insulation Diy

Can you put too much insulation in an attic?

While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.

Is roof insulation worth it?

Benefits. A quarter of heat is lost through the roof in an uninsulated home. Insulating your loft, attic or flat roof is an effective way to reduce heat loss and reduce your heating bills. Installed correctly, loft insulation should pay for itself many times over in its 40-year lifetime.

Where not to put loft insulation?

One important thing to remember is that insulation should never be pushed right into the eaves because it will interfere with airflow. If you're going for a warm loft then you'll need much more insulation to be able to cover the underside of the roof along with the gable and party walls.

How thick is room in roof insulation?

As stated in Approved Document L, loft insulation should be at least 270mm thick, which is the requirement for newly built properties. If you're looking to refresh the insulation in your loft space, you may find you have as little as 25mm, which was the recommended amount in the 1980s.

Is it better to insulate attic floor or roof?

roof insulation is no-contest. The floor wins every time. Insulating the floor is standard practice for an unfinished attic space. The exception to this rule takes place when families opt to convert an unfinished attic space into something usable or livable.

What is the best insulation for an attic ceiling?

Fiberglass batt is considered to be the best insulation for attics. Compared to other insulation materials, it is the cheapest and easiest to install.

Is it better to insulate the rafters or the ceiling?

Since insulation is not water-resistant, insulating your ceiling will give you better protection for your money. The insulation in your ceiling is less likely to suffer damage from unidentified leaks. When a roof leak develops, you'll find it more easily, which means you can have it repaired sooner.

What are the three main types of ceiling insulation?

What Types of Ceiling Insulation are there?
  • Fibreglass Batts: Fibreglass, also known as “glass fibre” or “glass wool” is one of the more common types of insulation used in homes. ...
  • Rock Wool Batts: ...
  • Spray Foam: ...
  • Blown-In insulation: ...
  • Polyester Batts:

How many inches of insulation should be in my attic?

The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

How much heat is lost through the roof?

Typically, 30-35% of the heat will be lost through uninsulated walls, 20-25% through the roof, around 15% through windows, 15% through leaky ventilation, 10% through the floor and 5% through doors.

Should I insulate the underside of my roof?

Do you have any plans for furnishing/fitting out your attic in the future? Then you could simply insulate the pitched roof. But the best solution is actually to insulate both the attic floor and the underside of the roof.

How thick is r30 roof insulation?

The owner's requirement for, say, R-30 insulation means 5.2” of polyiso, but that definitely does not mean a 5.2” thick board. At minimum, you want to provide two layers of 2.6” iso, with the top layer's joints offset at least 6” from the underlying layer.

How is room in roof insulation done?

Installing room in roof insulation involves insulation boarding being fitted in between the rafters underneath the existing plasterboard walls. Room in roof insulation works by trapping heat within your home to create a blanket effect.

Should there be space between insulation and roof?

Should you leave a gap between the insulation and the roof? Yes, you should leave an air gap between the insulation and the roof to allow proper ventilation and prevent moisture buildup.

Should I remove old loft insulation before laying new?

Should I remove old loft insulation before laying new? Older insulation material will typically need to be removed before adding new insulation. However, in some cases the material may be in good condition, meaning you can simply top up the existing insulation material for a fraction of the cost of a full replacement.

Where not to insulate?

Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.

What is the best insulation for roof rafters?

Our Conclusion. We recommend spray foam insulation because of its relatively simple installation process, high R-value, and applicability to different climate regions. While there are other effective insulators, contractors consistently choose spray foam for these reasons.

Which type of roof insulation is best?

Firm boards of either synthetic or natural materials are the best solution for insulating the underside of your roof. The boards provide highly effective insulation for your loft space and can also be decorated over. The downside is that sheet insulation tends to be the most expensive type.

Can you put too much insulation in a roof?

Too much insulation will leave humidity and moisture to accumulate in your attic space. This can lead to mold growth on your walls and insulation. There might also be water damage to the support beams in your home's roof.

Does roof insulation need vapor barrier?

(Source: NRCA.) In the event you are erecting a “cold building” (such as a refrigeration building) that stays at 32 F (0 C) degrees or less inside, you will need a vapour barrier on the outside of the insultation to prevent warm exterior air from entering and potentially damaging the roof's insulation. (Source: NRCA.)

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