How To Insulate Concrete Walls: A Complete Guide

insulating a concrete wall

Homes built with concrete walls promise to stand the test of time, but, unfortunately, they offer little by way of insulation from the frigid weather. As a result, it won’t be surprising when you receive high heating bills in the winter months thanks to the rapid loss of heat through the walls.

For that reason, your best bet for more energy efficiency is to learn how to insulate concrete walls.

Below, we offer a detailed understanding of why you should insulate concrete walls and the factors to consider before starting this project. We also go through step-by-step instructions and answer several questions you may have about concrete wall insulation.

Why You Need Proper Insulation for Concrete Walls

Did you know that a 24 cm concrete wall has almost the same U-value (the rate of transfer of heat) as a particle board around 2 cm thick? In other words, concrete block walls’ insulating properties are similar to the much thinner particle boards!

Keeping that comparison in mind, it’s always the right decision to insulate concrete walls because it:

  • Saves energy bills by up to 20%
  • Makes your home or office more fire-resistant and soundproof (depends on insulation material type)
  • Reduces moisture buildup, which improves the air quality in the interior space
  • Limits the existence and spread of mould or mildew
  • Offers more warmth and comfort in cold weather since it prevents temperature fluctuations 
  • Helps keep out dust and allergens—beneficial for people with asthma and other respiratory diseases

Things to Think About Before Insulating Concrete Walls

Before hiring a contractor or insulating your walls yourself, here are some factors to determine first for a mistake-free project.

1. How Much Insulation Your Concrete Walls Need

Of course, no two houses or buildings require the exact same insulation. So, you’ll need to factor in several points, including:

  • Insulation type
  • U-value of the insulating material
  • Weather conditions where you live

You’ll have to find a good balance of all three, which can be a bit challenging if this is your first time taking such a project on your own. 

For a hassle-free experience, you can contact a reputable insulation expert to assess your property and calculate how much insulation it requires.

2. Insulation Type

For concrete walls, you may choose from many different insulation material types, but we’ll go over the three more popular ones. 

Each has its strengths and weaknesses, so consider those carefully before making up your mind.

1. Rigid Foam Insulation

This type of internal wall insulation is done by fixing insulated plasterboard to the inside of your walls. Usually, each board comes in a thickness of 60mm or 100mm, depending on your needs.

The greatest thing about rigid foam is that it’s simple to install, so you may do it yourself without professional help. It’s also water-resistant, and you can easily fit it into your concrete walls without leaving any gaps.

2. Spray Foam Insulation (Open-cell and Closed-cell)

Next up, many homeowners favour spray foam as a reliable insulation material. The reason for this liking is that it’s applied as a liquid to your concrete walls, expanding through all the crevices for an airtight seal.

Other benefits of this insulation type include:

  • Great soundproofing and prevention of draughts in interior environments
  • A suitable choice for basements and unfinished walls
  • An eco-friendly option

However, bear in mind that spray foam is significantly more expensive than other concrete wall insulation types. Plus, you’re best leaving its installation to the experts since it’s hard to work with.

3. Fibreglass Batt Insulation

The final popular concrete wall insulation method is the one that uses fibreglass batts. As the name implies, you apply batts or rolls of fibreglass to concrete walls to keep the heat contained within the rooms of your building.

While this is by far the easiest and most affordable insulation type, it has a few downsides to consider.

First, it’s prone to mould growth since it absorbs moisture. So, you’ll have to replace it more often. Second, fibreglass has a higher U-value than the previous two options, but this only makes sense as it comes at a more budget-friendly cost.

3. Existence of Moisture in Your Building

The third factor that can affect your decision regarding concrete wall insulation is the amount of moisture inside your home, office, or other interior spaces. See, the higher the moisture is, the less effective the insulation will be.

Since all insulation materials absorb moisture — at different rates, of course — you’ll end up changing your insulation rapidly. For that reason, inspect your home and see if it needs moisture control before insulation.

4. Air Sealing

Lastly, remember that having areas inside your home where air can find its way out is counterproductive. You don’t want the cost and effort that goes into insulation to be washed away when the heat still escapes through crevices in the walls!

To prevent this scenario, you may use sealants or caulks to air-seal your rooms. Even better, you could choose spray foam as an insulator to benefit from its fantastic sealing qualities.

Insulating Concrete Walls: Explaining the Top 3 Methods

Whether you’re determined to tackle this project yourself or hire a professional, you’ll need to learn the right steps to insulate concrete walls.

In this section, we go through the workflow of insulating concrete walls using rigid foam, spray foam, and fibreglass batts.

Method 1: Rigid Foam Insulation

The first thing you should do regardless of the insulation method is to prepare your concrete walls. Easily enough, start by cleaning them thoroughly to get rid of any dust or debris that could get in the way of a smooth, clean insulation.

Right before you begin the insulation process, your concrete walls must be completely dry to keep mould at bay. Afterwards, you—or your contractor—will have to follow these steps to install rigid foam boards:

  1. Start by wearing safety goggles to keep any particles from getting into your eyes while cutting the boards.
  2. Measure the dimensions of your walls and use a circular saw to cut the boards after sizing them up and marking them on their foil backing.
  3. Use jigsaw cuts for any curves or corners in your concrete walls.
  4. Apply adhesive or plaster to the back of your cut-up boards, then place the boards in their designated spaces on the walls.
  5. Seal the seams with caulk to prevent air leaks.

Method 2: Spray Foam Insulation

As previously mentioned, spray foam insulation is a process that needs expert hands. You can expect your contractor to go through these steps:

  1. Assessing the condition of your concrete wall and checking for gaps, holes, and crevices
  2. Checking the temperature around your home (if it’s beneath 5°C, it might prevent the foam from binding to the masonry)
  3. Wearing eye protection, gloves, and a respiratory mask 
  4. Carefully spraying the foam on the wall until it reaches behind the studs installed in place
  5. An alternative method is to drill small holes in each block and then expertly inject the liquid foam until the entire space is filled.

Method 3: Fibreglass Batt Insulation

After cleaning the concrete walls, you can apply fibreglass batts this way:

  1. Start by ensuring that there are no water sources around the area you’re working in so as not to ruin the fibreglass batts.
  2. Wear protective gear and a mask because exposure to small glass particles could pose several health risks.
  3. Ensure the room you’re working in is well-ventilated to prevent the inhalation of harmful glass fibres.
  4. Measure the areas where you want to install insulation with a measuring tape, then mark the fibreglass rolls accordingly.
  5. Use a sharp utility knife for clean-cut fibreglass insulation pieces.
  6. Press these pieces against your concrete walls, securing them with a staple gun and staples.


How do you maintain concrete wall insulation?

Having your insulation professionally installed is your top priority, but it’ll be useless if you don’t maintain it regularly. Follow these guidelines to boost the longevity of your concrete wall insulation:

  • Always check the insulation at regular intervals for any tears or mould patches and quickly fix these issues if you find them.
  • Avoid resting heavy objects against insulation so as not to jeopardise its integrity.
  • Periodically check for air leaks and address any moisture-related problems to keep the insulation material intact for as long as possible.
  • Don’t add new insulation on old insulation, but replace it if it’s damaged beyond repair.

How much does it cost to insulate concrete walls?

The cost of concrete wall insulation varies depending on the type of insulation, where you live, and other factors. 

Still, here’s an estimate of what each type of insulation can cost you on average:

Insulation typeCost
Rigid foam insulationAround £8,500 (for a 3-bedroom, semi-detached house)
Spray foam insulation£1,200–£4,000
Fibreglass batt insulation£880–£4,000

What is the most affordable material for concrete wall insulation?

Fibreglass batts or rolls are the most budget-friendly option when it comes to concrete wall insulation types. 

They’re also easy to work with, so you can save more money by taking up a DIY insulation project!

How long can you expect concrete wall insulation to last?

The lifespan of your insulation will vary depending on the material type and weather conditions in your area. How often you maintain your insulation will also impact its longevity, so make it a priority to help your insulation last longer.

On average, you’ll likely need to replace your rigid foam insulation after 30 years. On the other hand, spray foam can last up to a roaring 100 years!

Fibreglass insulation may also live for 80 to 100 years, but you should still inspect it every 15 years to repair any tiny tears in it.

How to Insulate Concrete Walls: Final Thoughts

Many UK homes can greatly benefit from insulating concrete walls to ward off the unwelcome winter cold. For a warm and inviting atmosphere at home, you may opt for fibreglass, rigid foam, or spray foam insulation for concrete walls.

Because it can be hard to DIY, especially without much experience in insulation projects, you’ll need the best installers to carry out the job for you. 

Insulation Advisor can be your guide to trusted contractors in your area, helping you hire insulation experts with zero hassle. Contact us and get a quote now!

On This Page
Get Your Insulation Quote