Solid Wall Insulation

a solid wall

If your walls could talk, they’d say that about a third of heat meant for the house passes them by every year. That’s energy and money that goes to waste. Get a handle on solid wall insulation and how you can shore up your home and benefit from a warmer home this winter.

Types of solid wall insulation

There are two types of solid wall insulation, interior solid wall insulation (inside wall insulation) and exterior solid wall insulation (outside wall insulation). 

If your home was built before the 1920s, you probably have solid walls. For properties built later than that, you will need to look at cavity wall insulation. Solid wall insulation can be a tricky and expensive bit of home improvement, so it’s best to hire a professional. But how do you tell what type of walls you have?

A quick way to know is to check the length of the bricks in the wall. Solid walls usually have bricks of unequal lengths while cavity walls have bricks that look more or less the same. Solid walls also tend to be less than 260mm in thickness.

Cost of solid wall insulation

According to the Energy Saving Trust, external wall insulation for a semi-detached house would cost around £13,000. For an internal wall, the costs are a lot less, coming in at about £7,000.

Can I get free solid wall insulation?

Yes. If you receive certain benefits, you might be able to get a government grant for insulation to help with some, or all, of the cost of insulating your solid walls. 

Difference between interior and exterior solid wall insulation

While cost could be one of the deciding factors on which type of insulation you choose, our table below will help you understand the key differences between internal and external solid wall insulation.

Type of solid wall insulationProfessional required?Planning permission?Appearance of the houseDuration of workLoss of internal space
InteriorNot alwaysYes, for listed buildingsWon’t change4-5 daysYes
ExteriorYesNo, unless the building is in a Conservation AreaWill change4-5 weeksNone

What are the benefits of solid wall insulation?

Solid wall insulation could save you about £320 on your annual energy bills. Using the Energy Saving Trust’s cost estimates, insulating an external wall would take roughly 40 years to pay for itself. 

While this may feel like an age away, there are some additional benefits to consider. You could quickly improve your home’s Energy Performance Certificate rating, its resale value and, have a much warmer property each winter.

Solid wall insulation also provides a layer of protection against noise from the outside and rooms within the property.  

How to insulate a solid exterior wall

Although external wall insulation requires the skill of a professional, here’s a breakdown of what’s involved:

  • Your wall will need to be checked for signs of damp. If any is found, the work will have to be delayed until the problem is fixed.
  • First, a layer of insulating material will be attached to your wall. Then, the material will be covered by either render (plasterwork) or cladding.  
  • After that, you’ll need a finish applied to the walls to make them visually appealing. Depending on your taste, this could be stone, glass, tiles or wood finish. Not only does it give your walls a more beautiful look, but the finish also adds an extra layer for heat retention.

How to insulate a solid interior wall

To insulate the internal solid walls at home, your installer will:

  • Fit rigid insulation boards to the wall, or add a stud wall and fill in the gaps with fibre insulation, natural or mineral wool or your chosen insulation material. 
  • If you’re using rigid walls, they’ll be fixed to the wall with plastic or adhesive. Then, the installer will add extra fillings to hold the boards in place and seal the joints between the boards. 
  • For stud walls, you’ll be given the choice of either metal or wooden frames, which will then be attached to walls. The insulation material will then be inserted into the gap between the frame and the wall.

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