Homes can lose up to 25% of their heat through a poorly insulated roof, and up to 35% through poorly insulated walls and windows. A well-insulated home can provide year-round comfort, help increase energy efficiency and save a lot of money on your annual energy bills by keeping heat loss to a minimum. 

This guide is designed to help you to work out what insulation your home needs, give an overview of the different materials and types, and look at how much money you could look to save on your heating bills. 

What is home insulation?

Home insulation involves installing materials in the loft and walls of your home to reduce heat loss. It works by creating a barrier between the inside of the home and the outside air to help you to maintain the desired temperature within your home.

Home insulation is essential for keeping you warm in the winter. Without adequate insulation the home can lose a lot of heat, with heat mainly escaping through the roof and walls. If your home is poorly insulated, it will cost much more to keep warm, as your heating system will be constantly working to compensate for heat loss.

Heat can escape the home in several different ways:

  • Conduction: The transfer of heat through a solid material. Most commonly this happens through the windows, external walls, floor and roof. 
  • Convection: The process in which heat is lost by either warm air leaking to the outside, when doors or windows are open, or by cold air coming into the home through poor insulation, or cracks or openings in walls, windows and doors. 
  • Radiation: The transfer of heat from warmer to colder objects. For example, if a radiator is running next to a poorly insulated external wall, heat loss will occur and escape through that wall.  
  • Air: Draughts are another key part of heat loss in the home. Cold air can come into the home through gaps in windows and doors, so ensuring good draught exclusion is key.  

What are the benefits of home insulation? 

Installing good insulation in the home can have many benefits, financial as well as environmental ones. These include:

  • Greater comfort: Good insulation will provide a higher level of comfort in your home, all year round. It reduces heat loss in the winter, and also protects against excessive heat gain in the summer, helping keep your home cool.  
  • Lower bills: Good insulation will help you to save significant amounts on your energy bills, For example, installing solid wall insulation in the home could save you up to £930 every year, and loft insulation up to £590 a year (these figures are based on detatched houses going from no insulation to fully insulated). Insulation can pay for itself through savings in your bills in around 2-5 years depending on the type.
  • Soundproofing: Insulation acts as a sound absorber and reduces the amount of noise that travels within the home, from room to room. Insulation can also reduce noise from outside, particularly if you live near a flight path, or a busy road. 
  • Lower carbon footprint: Insulation is an important step you can take to combat climate and reduce your carbon footprint. A well-insulated home means your heating system doesn’t have to work as hard, or run for as long, reducing the amount of fossil fuels burned to heat the home.
  • A stepping stone to sustainable heating: Good insulation in the home also opens the opportunity to install a sustainable heating system, such as an air source heat pump.

How do I choose the right type of insulation for my needs?

With every home built a little differently, it’s important to make an informed decision about insulation and ensure the best results for maximum energy efficiency. Here are some of the things to consider when deciding what type of insulation to go for. 

Loft insulation 

A quarter of your home’s heat can be lost through an uninsulated loft. Loft insulation has a typical lifespan of 40 years, and could save you up to £590 per year on your energy bills. Provided you have no underlying damp problems and you are using your loft for light storage only, then this could be a job you do yourself.

The material you are most likely to use for this job is matting. It is sold in rolls and usually made from glass fibre, rock fibre or sheep wool, and it comes in different thicknesses and flexibilities. You can also use loose fill, which is sold in bags and then poured out for use. Made from cellulose fibre, mineral wool, cork granules or vermiculite, it can be perfect for those harder to reach areas and corners of the loft.  

All insulation comes complete with a Lamba or ‘K value’ that measures the thermal conductivity. The lower the value, the less heat loss you will experience with the material. It’s worth noting that the thickness of the material isn’t always key. Thinner materials can have a lower Lamba value, and are therefore more efficient, so always double check if you are planning to install insulation yourself. 

If you use your loft as a living space, then insulation will need to be installed in the rafters. This is a job that you will typically need to get a professional to do.

Cavity wall insulation 

A typical home will have either a solid wall, or cavity wall. With cavity wall there is a small gap between the outer wall, and inner wall of the home, known as the cavity. Insulation is pumped into the gap, resulting in greater insulation and less heat loss. Cavity wall insulation needs to be done by a professional using specialist equipment, so this type isn’t suitable for a DIY job. 

Solid wall insulation 

Much older properties may use a solid wall construction, and they can experience much greater heat loss as they have no cavity or gaps, with only one layer between the inside and outside air. Solid walls can be insulated both internally and externally. Internal wall insulation uses solid boards which are attached to the internal walls, or an additional stud wall installed to place matting based material such as sheep’s wool. This is the cheaper option for wall insulation.  

External insulation on solid walls involves applying boards, which are held in place by reinforcing mesh and render. A cladding is then sometimes placed over the original brickwork. This is the more expensive route for wall insulation and does sometimes require planning permission if it changes the outside appearance of a property. 

Floor insulation 

This involves installing insulating material beneath the floorboards on the ground floor of the home. It stops draughts coming into the home through the floor and comes with expected energy bill savings of up to £75 per year. Floor insulation can also involve sealing gaps between the skirting boards and floors. 

Draught proofing

Draught proofing is another option that can be used to prevent heat loss in the home. Simply put, draught proofing involves blocking up any non-essential & unwanted gaps that let cold air escape. A example of draught proofing is installing a letterbox flap, but draught proofing can also be installed in places such as windows, and floorboards. This is often something that can be done yourself.

How much does home insulation cost and how quickly will it pay for itself through savings in my bills? 

Prices for insulation will vary depending on the size of your home, the materials used, and the area being insulated. Here is a rough idea of what to expect:

Loft insulation 

Insulating the loft can be very cost effective, and you will typically be able to carry out the work yourself from around £100, depending on the size of your home. While it is relatively easy, if you prefer to hire a professional this will push your costs up to anything from £590 for a mid-terraced house to £890 for a detached house, when factoring in labour fees. 

With all house types, loft insulation will pay for itself through savings in your energy bills in less than two yearssaving a mid terrace home around £330 a year and a detatched home around £590 a year.

Cavity wall insulation 

Because cavity wall insulation needs to be installed by a professional, you can expect slightly higher costs than loft insulation. A small flat will cost around £395 to insulate, whereas a detached home could cost up to £1800.

This insulation will pay for itself through savings in your bills in around three years – saving a small flat around £180 a year and a large detached home £690 a year.

Cavity wall insulation

Solid wall insulation 

Solid wall insulation can be quite expensive to install, therefore homeowners often combine the installation with other home improvement works to save on labour costs and call-out fees. Typical prices for a semi-detached house will be around £12,000 for external wall, and £8,500 for internal wall insulation based on a semi detached house.   

You could expect savings of around £540 a year through your bills for a semi-detatched house – which would see a payback period of around 15 years.

Are Government grants available to help with the cost? 

There are a few means-tested Government grants to help the lowest income households with the cost of insulation.

The Energy Company Obligation (ECO) is a requirement for certain energy suppliers to help households reduce the costs of their home heating by fitting energy-saving measures. You will need to check directly with your energy supplier to see if you are eligible.

The Sustainable Warmth Competition will provide energy efficiency measures and low carbon heating to low income households living in energy inefficient homes in England, and is delivered via your local council. You can see here to see if your council has been allocated funding, and also check if you are eligible. There are two means tested schemes focusing on the following:

  • Local Authority Delivery Phase 3 scheme for low-income homes heated by mains gas
  • Home Upgrade Grant Phase 1 and Home Upgrade Grant Phase 2 scheme for low-income households off the gas grid.