An uninsulated home is costly to heat because it loses 30-40% of its heat through the walls, 25% through the roof, 15-20% through windows and doors and 10% through the floor. 

According to the Energy Saving Trust, insulation can help save the following amounts per year (based on a gas-heated home and fuel prices in November 2021):

Insulation type	Detached house	Semi-detached house	Mid-terrace house	Detached bungalow
Loft	£380	£165	£150	£235
Cavity wall	£310	£185	£120	£125
Solid wall	£425	£225	£160	£170
Floor	£85	£50	£35	£75

This section shows you how to improve a home's insulation by covering all the areas where insulation can be installed. 

Loft Insulation

Loft insulation creates a barrier between the top floor of a house and the roof space, stopping heat from escaping.

There are two ways to insulate a loft:

Insulate the floor by laying insulation between the joists.

• This creates a cold loft space 
• Use any type of loft insulation material such as rolls of mineral wool or fibreglass loft insulation
• The recommended insulation thickness is 270mm
• Existing insulation that’s thinner than 270mm can be topped up rather than starting from scratch. 

Insulate the ceiling by laying loft insulation between rafters. 

• This creates a warm loft space 
• Use spray foam, rigid foam insulation or double reflective foil insulation

Watch our video to see how easy it is to install YBS double reflective foil insulation.

https://www.youtube.com/watch?v=yGNkec9Gzto 

Loft Insulation Dos & Don’ts

Do:

• Always insulate the loft floor
• Insulate the loft ceiling if the space will be used as living space or to store temperature-sensitive items
• Lay the floor insulation to the maximum recommended thickness.

Don’t:

• Squash insulation if you place floorboards on top (this will reduce its effectiveness). You also need a 50mm clearance between the insulation and loft board to prevent condensation
• Cover any ventilation holes in the roof.

 

Roof Insulation

As explained in the loft insulation section, a roof can be insulated from the inside to create a warm roof. However, it can also be insulated from the outside. 

Insulating a pitched roof from the outside: 

• Lay insulation between rafters, underneath the roofing felt, bitumen and roof tiles 
• Roof insulation types include rigid foam boards or double reflective foil insulation 
• This method involves removing the roof tiles, etc., so it’s best done as part of a new roofing project. 

Insulating a flat roof: 

• A flat roof should be insulated from above 
• Use rigid foam board or double reflective foil insulation 

• The insulation is added on top of the roof’s weatherproof layer on top of the timber roof surface with a new weatherproof layer on top 

Best done when the roof needs replacing anyway. 

 

Floor Insulation

Floor insulation is designed to insulate floors at ground level. Upper floors don’t need to be insulated unless the room is underneath an unheated space such as a garage. 

Floor insulation is required in older homes with suspended timber floors or solid concrete floors. 

Suspended timber floors: 

• Install insulation from underneath if possible (i.e., via a cellar or basement) 
• Add insulation between floor joists 
• Use rigid insulation boards or rolls of insulation made from any material 

• If installing from underneath, secure the insulation with netting or staple it to the floor. 

Solid concrete floors: 

• Lay insulation on top of the floor 

• Use rigid insulation boards of any material or double reflective foil insulation 
• Cover the insulation with chipboard and the desired floor covering. 

Other ways to insulate a floor: 

• Lay underlay beneath carpets 
• Apply sealant around skirting boards 
• Add rugs 

When considering floor insulation, weigh up the cost and potential savings versus the disruption. Floor insulation can save around £35-85 per year on energy bills. But it can be an expensive and disruptive job. The existing floor will need to be removed, and a raised floor will mean skirting boards and doors will need to be trimmed. So, it may be a job best combined with a complete room renovation. 

Floor Insulation Grants

Homeowners with suspended timber floors may be able to get help with the cost of insulation through their energy supplier thanks to the government’s Energy Company Obligation Scheme (ECO). Check with your energy supplier to see if you’re eligible. 

 

Wall Insulation 

Wall insulation works by creating a barrier around the walls of a home to stop heat from escaping. The type of insulation needed will depend on the wall type. 

Cavity Wall Insulation

• A cavity wall has a gap between the outside wall and the inside wall 
• Applies to most homes built since 1920 
• Use spray foam insulation to fill the cavity 

• It’s a job for a professional installer 
• It’s not suitable for homes with damp problems or walls exposed to driving rain. 

Solid Wall Insulation

• Applies to most homes built before 1920 
• Insulation can be installed on the inside or outside of the wall 
• External insulation needs to be 50-100mm thick 
• Internal insulation includes building a stud wall to which the insulation can be added 
• Use rigid foam boards, fibreglass or mineral wool insulation, double reflective heat insulation or spray foam insulation 

• Insulation will need to be covered with a final decorative layer 
• Internal wall insulation is very disruptive as switches, skirting boards, architrave, and radiators need to be removed and replaced. It also decreases the floor space. 

 

Other Ways to Insulate The Home

Replacing single glazed windows with double-glazing will also significantly impact a home's warmth and energy efficiency. But there are also plenty of more minor, inexpensive fixes that will help, such as: 

• Hot water cylinder insulation jacket 
• Cold water tank insulation 
• Pipe insulation 
• Insulated loft hatch (can insulate yourself or buy pre-insulated) 

• Draught excluder around doors and windows 
• Door brush strip 
• Keyhole covers 
• Letterbox plates 
• Chimney pot caps (for disused chimneys)

 It’s also worth considering insulating other areas in the home, such as a garage, shed or conservatory. 

 

The cost of home insulation will vary depending on the size of a home, the type of insulation used and whether it’s installed professionally or completed as a DIY job.

But as a guide, here’s what you can expect to pay:

Type of insulation	Typical costs
Loft (all new insulation)	£285 - £395
Loft (top up from 120mm to 270mm)	£230 - £290
Cavity wall	£390 - £610
Internal solid wall	£10,000
External solid wall	£8200
Floor	£520 - £1300

 

Some energy suppliers offer free home insulation as part of the government's Energy Company Obligation Scheme. The scheme is open to homeowners or people living in privately rented properties who receive state benefits.

Suppliers choose which insulation they offer, but it can include loft insulation, cavity and solid wall insulation and timber floor insulation.

To check whether you’re eligible, contact your energy supplier.