Insulation

Why should I insulate my home?

Insulating your home can save you money on your fuel bills, and make your home a warmer and more comfortable place to be. This section describes the different types of insulation available and the savings that can be made.

What are the different ways I can insulate my house?

Cavity wall insulation

This involves filling the cavity within the walls of a house with insulating material. Cavity walls are normally found in houses built in the 1930s or later.

Cavity wall insulation is one of the most effective forms of energy saving measure as it reduces the heat loss through the walls by up to 40% so giving significant savings in heating costs. The reduction in heat loss also leads to more comfortable living conditions and means it's warmer in winter and cooler in summer.

See the table below for the approximate cost of cavity wall insulation and yearly savings. Please note there are currently grants available for cavity wall insulation. Visit our grants and offers page for more details.

Previously there had been some association between installing cavity wall insulation and increasing damp problems. However, since the 80s, methods and materials have improved to such an extent that this is no longer the case. Nowadays all cavity wall insulation that is installed by a registered installer is guaranteed for 25 years with the Cavity Insulation Guarantee Agency (CIGA) against damp problems.

Solid wall insulation

This can be applied to either the inside or outside walls of your home. Most houses built before 1930 were built with solid walls. This means there is no cavity within the wall.

External wall insulation is worth considering when repairing the external walls. There are two methods: either an insulated cladding or insulating render is applied to external walls of the house. 

This form of insulation will change the external appearance of the property and so can require planning permission, it can also be expensive, see the cost table below for details.

Internal wall insulation is installed either by placing insulating material behind a layer of plasterboard (dry-lining) or using an insulating wallpaper, such as Sempatap. 

Dry-lining will slightly reduce the floor area of the rooms and is best considered as part of a major renovation of the property.

Both forms of internal insulation have the advantage that they can be applied to individual rooms if required, rather than the whole property, therefore saving on cost.

View our Solid Wall Insulation Factsheet

Download information on discounted Thermal Sempatap ("Warmer Walls" leaflet)

Prices and payback time for wall insulation

Wall Insulation	Cavity*	Internal*	External*
Cost of fitting by installer	£250	From £1,200 - £3,000	From £2,000 - £5,500 (if walls are being repaired anyway)
Annual saving on fuel bills	£120	£360	£380
Cost recovered	2-4 years	5-6 years	9-11 years

Loft insulation

This can save you up to 25% of your heating costs. The recommended thickness of loft insulation is currently 250mm (10"). Loft insulation can be either installed by you or by a professional installer.

Dont forget that it is important to leave a gap around the eaves. The loft needs to be ventilated to stop condensation forming. Also, remember to draught-proof the loft hatch to stop draughts entering your home. 

See the table below for approximate costs of loft insulation and yearly savings. Please note there are currently grants available for loft insulation. Visit our grants and offers page for more details.

Price and payback time for loft insulation

Cost	Adding 200mm to existing 50mm of loft insulation	250mm loft insulation where none at present
Cost of fitting	£275 (installer) From £150(DIY)	£275 (installer) From £180 (DIY)
Annual saving on fuel bills	£45	£155
Cost recovered	6-8 years (installer) 3-4 years (DIY)	2 years (installer) 1-2 years (DIY)

 

Hot water tank and pipe insulation

This can help to keep your hot water hot longer and prevents pipes freezing in cold weather. Hot water cylinder jackets can be fitted to your hot water tank and pipe insulation to your pipes. Both are easy to fit yourself and can be bought from any good DIY store. New hot water tanks will come fitted with foam insulation.

Fitting a thick hot water tank jacket can cut heat loss by up to 75% from your hot water tank. If you already have a jacket which is less than 75mm thick then you can fit another one around it or replace it completely. You will save even more money.

Prices and payback time for water tank/pipe insulation

Cost	Fitting jacket to your hot water tank*	Insulating hot water pipes*
Cost of fitting (DIY)	From £10	From £10
Annual saving on fuel bills	£30	Up to £10
Cost recovered	Up to 1 year	1 year

 

Draught-proofing

This is a cheap way of preventing cold draughts entering your home. Draught-proofing materials are available from any good DIY store and can be placed on doors, letterboxes, keyholes and windows. 

Draughty doors and windows are a major source of heat loss and fitting draught excluders can greatly increase your comfort and reduce fuel costs.

Prices and payback time for draught proofing

Cost	Draught proofing*
Cost of fitting	£90 (installer) From £40 (DIY)
Annual savings on fuel bills	£25
Costs recovered	8 years (installer) 4 years (DIY)

 

Floor insulation

This can prevent draughts and heat leaks from under your floor. You can apply a regular tube sealant to the gap like the type you use around your bath.

If you have access under the floor or you need to take the floorboards up, it's worth insulating underneath on the ground floor. Remember not to block any underfloor airbricks in your outside walls, as the floor space needs adequate ventilation.

Prices and payback time for floor insulation

Cost	Under floor*	Filling gaps between skirting board and floor*
Cost (DIY)	From £90	Around £10
Annual Saving on fuel bills	£40	£10
Cost recovered	2-3 years	1 year

 

What should I remember when insulating my home?

When insulating your home ventilation is important to keep your house healthy.

If a house is not adequately ventilated, it may suffer problems with damp and condensation. This can lead to health problems for the occupants and the property may suffer structural problems in serious cases.

Where can I get financial help installing insulation?

Our Grants and Offers page has more detailed information about who can help with the cost of installing insulation in your home.

Page last reviewed 12 Sep 2008

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