A Guide to Roof and Loft Insulation

A Guide to Roof and Loft Insulation
Posted in: Guides, Insulation

Roof and Loft Insulation Guide


Roof and loft insulation can save you money, keep your house warm and help the environment. However, it can also seem like a very complex subject which many different types of insulation available.

To help you learn about the types of insulation which will be best for your home, we have compiled this guide to roof and loft insulation which are a great place to start when insulating your home. Read on to learn how they work to make your home more energy efficient and the costs involved.


How Does Roof Insulation Work?

A heating system creates hot air which rises and tries to escape through any gaps we have in our roof or loft space. To stop this happening there needs to be a barrier. Insulation materials contain small air pockets which help to create this barrier.

The insulation keeps hold of the heat when it rises and helps prevent it from escaping. Meaning your home stays warmer without having to keep increasing the amount of energy being used by your central heating system.


Types of Loft Insulation 

There are plenty of different options to choose from when looking to install loft insulation. Checking the R-value is an important point, as it measures how well the material is able to resist heat flow. The following are the different types of loft insulation you can consider:

Mineral Wool

Made from yarn that is either spun from glass wool or rock wool, it comes in large rolls otherwise known as “batts”. It is then rolled into the space between loft joists, while the loose yarn can also be added into hollow spaces. 

It is a good option as it is good at conducting heat, and it’s also great for soundproofing. It tends to be cheaper overall than some other types of insulation, while its use usually has a minimal carbon footprint. 

Make sure you wear gloves when handling it, as it can be very irritating on the skin. 

Sheep’s Wool

A natural choice, sheep’s wool is often formed into rolls but can be bought as large tiles as well in some cases. It’s always been a popular choice due to it being safe and easy to use, while also being very good at insulating from sound and at holding heat. It’s 100% recyclable too, and is made out of sustainable material.

Spray Loft Insulation

Only to be done by a professional, spray foam can also be used to create a thick liquid that is sprayed out over the loft with a special applicator. The foam will expand quickly and fill gaps where needed, hardening into a dense blanket. 

This option is immune to mould, mildew, and bacteria, while also having a very long lifespan.  

What Are The Benefits of Loft Insulation?

You can reduce your heating bills by relying a lot less on gas and electric heating to warm your home up, as insulation helps retain the heat during the cold winter months.
It also helps keep the home cool in the summer months, so you’ll not overheat when staying indoors. 
Adding loft and roof insulation can also improve your home’s energy efficiency rating, and essentially pays for itself due to the saving on bills. 
It’ll also contribute to increasing your home’s overall value on the housing market, for if you were ever looking to sell. 


Things To Consider When Installing Loft Insulation 

Before you decide on installing loft and roof insulation into your home, there are a number of aspects to consider.

  • Storage Space: If you need your loft for storage space, you’ll need to lay boards down over the joists.
  • Damp: Make sure that there are no existing problems with damp and condensation, as the insulation will make the loft a lot cooler. Increase ventilation to make sure any problems with damp aren’t made worse.
  • Inaccessible loft spaces: If you can’t access your loft, then installing insulation will be difficult. However, you could hire a professional to have blown insulation installed.
  • Flat Roof: If you have a flat roof, it should probably be installed from above. It is possible to insulate a flat roof from underneath, but issues with condensation can occur if it’s not installed correctly. 

How Much Can I Save By Insulating My Loft?

How much you’re able to save by installing loft insulation will depend on the depth of your insulation and the type of home that you have. As an example, 270mm of loft insulation can save the following per year on energy bills, on average, when compared with an uninsulated home. 

  • Detached House: £380
  • Semi-Detached House: £165
  • Mid-Terrace House: £150
  • Detached Bungalow: £235


Do I Have a Flat or a Pitched Roof?

The difference between a flat roof and a pitched roof is simply the slope of the roof. Although called a flat roof it may still have a slope to aid drainage. This type of roof is also referred to as a low slope as well as a flat roof. A flat or low slope roof rises from 1 inch to 3 inches per 12 inches. A pitched roof is any roof that rises 4 inches or more per 12 inches.

Can I Insulate Both Flat and Pitched Roofs?

Yes, both types of roof can be insulated. It depends on what level of pitch you have as to the type of insulation you use. A flat roof has three types to choose from and they are; warm deck, cold deck or inverted roof. With pitched roof insulation, you have two choices; warm or cold loft insulation.


What is the Difference Between Insulating a Roof or a Loft?

You will normally insulate the roof if you are using it as living space, that is if you have converted your loft space into a room. In this case, you will have to insulate between the rafters and you can use a variety of materials.

Insulating only your loft means that you don’t intend to use it as a living space, so you can apply any insulation material in between and over the joists. This is the cheapest method of insulating your home.

How Deep Does the Insulation Need to be?

If you are using glass wool, sheep’s wool or loose fill, then the depth should be 300mm. Rock wool should be 250 millimetres. Spray foam increases in volume, so you don’t have to use as much to get the same effect as other materials. Cellulose should have a depth of 220 millimetres.


Will My Old Loft Insulation be Enough?

This depends. If your loft was insulated in the 60s, then no because the recommended value was only 25mm. If you had your insulation fitted after 2013 then you might be okay because it was at this time the government stated that if a loft insulation was 125mm in thickness, then it would be considered insulated. However, by installing more insulation to bring you up to the government’s recommendation of 300mm you will make your house more energy efficient and therefore lower your heating bills.


Options for Insulating a Flat Roof

Flat roofs lose a lot of heat and it is a good idea to insulate them if you can. The normal method is to use warm deck insulation, and this can be achieved by insulating below or above the waterproof membrane. A number of materials can be used including; wood fibre batts, mineral wool slabs, PIR or PUR boards and extruded polystyrene.


How Much Does Loft Insulation Cost?

The cost of loft insulation will depend on the type of property you own. You might also be eligible for free insulation or for a grant which will help towards the costs. If you already use your roof space as an extra room or you are planning to do this, then the costs will be higher because it is better to use insulating boards rather than blanket insulation and it is more expensive.

Don’t forget, you may be eligible for a grant for roof insulation, have a look here at the government grants website for further information.


How Long Does Loft Insulation Last?

As long as the material doesn’t get damaged, then there’s no reason why it shouldn’t last your lifetime. Most materials last between 80 and 100 years.


What is Warm Loft Insulation?

Warm loft insulation is used on pitched roofs where you are using the loft space as a room or for storage. The insulation is installed under the roof, in the slope. You should leave the space under the roof tiles free from insulation to give adequate ventilation so that you don’t get condensation or water coming through the tiles.

You can use batts, polystyrene slabs, expanded polystyrene or spray foam to insulate your roof or loft space. Spray foam is usually a job undertaken by professionals. Although there are DIY options available in the marketplace.

One of the advantages of warm loft insulation is that it is ideal for a flat roof. This is because there are problems with condensation. It is more thermal-efficient than a cold roof, therefore lowering energy costs and it protects the roof structure from very hot or very cold temperatures.

The disadvantage to warm loft insulation is that the costs are higher than cold loft insulation.


What is Cold Loft Insulation?

Cold loft insulation is the most popular method used for roofs and lofts because it is the cheapest option. You install the insulation above the ceiling on the top floor of your home. The material is placed over the top of and between all the wooden joists. If you want to install loft insulation using this method, you can apply for a government grant.

The advantages of cold roof insulation are that it is cheaper to install, it can keep your house cooler in the heat of the summer and it is suitable for outbuildings or places that you don’t live in continually.

The disadvantage is that it isn’t as effective if you have a flat roof. The insulation can move, forming gaps which allow condensation to gather and dust and dirt to get through any voids in the ventilation system.

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