21st Nov 2022 -

Wall insulation is essential to prevent heat loss within a building, saving you a significant amount of money on heating bills whilst keeping your building warm. When it comes to insulating walls, the only walls within your home or larger building that will require thermal insulation are the outer walls, while internal walls can benefit from acoustic insulation. In this guide from Building Materials Nationwide, we’ll look through the three methods to insulate your walls, cavity wall insulation, internal wall insulation, and external wall insulation. We’ll also take a look at acoustic wall insulation within the walls of your building. 

The Benefits of Wall Insulation

Approximately 35% of heat loss in a house is through walls, more than any other area of a home. Thoroughly insulating your walls can save up to £350 per year in energy bills. Not only will wall insulation save you money and keep you warmer, but it will also benefit the environment, reducing the amount of fossil fuels needed to heat a building. 

A construction worker wearing a full white PPC overall with gloves and a black mask installing spray foam insulation within the interior of a wooden wall frame structure.

Cavity Wall Insulation

Cavity walls are outer walls that are built from two layers of bricks, with an air gap, or cavity, between them. Most houses built after the 1920s are likely to have cavity walls. While insulation boards can be used within a cavity wall during the building process, if looking to insulate your built cavity walls you will need to opt for blown-in cavity wall insulation. This method involves drilling small holes within the outside of your cavity walls and blowing one of several insulation substances into it.

Your options for insulation materials will be mineral wool, polystyrene beads or polyurethane foam. Blown mineral wool offers long-lasting thermal insulation, but can have issues in unusually shaped walls or stone walls. Expanded polystyrene beads are coated with an adhesive, holding them in place within your cavity wall. They perform better in stone walls or thinner cavity walls than mineral wool insulation. Finally, polyurethane-injected foam insulation is a premium choice, giving excellent full-fill insulation in all cavity walls, and even bonding your walls together.

For more information about the costs of cavity wall insulation, read our guide.

Are Your Cavity Walls Suitable For Insulation?

While they offer an excellent level of insulation within a building, insulated cavity walls can cause issues in certain properties. Before embarking on a cavity wall insulation project, it’s important to ensure that your walls are suitable. Risks could arise if your house is in an area with high levels of wind-driven rain, which would include much of the west coast of England and almost all of Wales. Another risk is if your outer walls are cracked or damaged. Both of these problems could lead to moisture getting into your home when cavity wall insulation is installed. Regardless of where you live, you should get an independent survey of your cavity walls before insulating them.

Cavity wall insulation requires specialist equipment and must be undertaken by a trained professional. We have a guide to the risks of cavity wall insulation on our website.

Cavity Wall Insulation Grants

Government grants for cavity wall insulation are available for some people within England, Scotland, and Wales, with energy suppliers potentially covering the entire cost of surveying and installation. To find out more about the energy company obligations scheme and whether you qualify, we have an explainer available on our website.

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Internal and External Wall Insulation

In buildings with no cavity walls, or cavity walls that are unsuitable for insulation, you will have the option to install insulation on either the internal or external facing of your outer walls.

Internal Wall Insulation

Internal wall insulation involves attaching insulation to the internal facing of your outer walls, either directly attaching it to the wall, or building a batten wall, and installing insulation within it. Before installing insulation on your internal wall, you should ensure that any issues with dampness have been dealt with beforehand, as ventilation and vapour permeability will be vital to ensure the long-term stability of your insulation.

To install insulation directly to a solid wall you can use dry lining insulation boards, which include both an insulation board and a facing of dry lining. They can be attached to a flat wall using either plaster or adhesive and will then be firmly secured using fixings. You’ll need to seal the joints between boards with scrim tape or jointing tape, at which point you’ll be able to decorate your wall as you see fit.

Alternatively, a batten wall can be built against your wall from a timber stud or metal stud frame. This can be insulated with a variety of traditional insulation supplies, like boardsslabs, and insulation rolls. The stud wall can be topped by plasterboards or insulated plasterboards can be used to further increase the levels of thermal wall insulation in your property. Unlike direct installation, batten walls can be installed against an uneven wall surface, building a flat surface to insulate and plaster. 

Internal wall insulation will cost you floor space, expanding the wall into your home. But it gives you a range of options and can be installed on a room-by-room basis for those working on a budget. To learn more, we have a comprehensive internal wall insulation guide. Unlike cavity wall insulation and external wall insulation, insulating internal walls can be completed as a DIY project, though experience is recommended.

External Wall Insulation

External wall insulation is also an option for insulating the outer walls of your properties. Specialised external insulation boards will be attached to the outer wall of your property. To install them, your walls must first be coated in render, before attaching the boards with both adhesive mortar and fixings. After this, your panels will be covered in another layer of mortar and an insulating mesh. This will be sanded down and covered in primer. You’ll then have the option to either coat your wall in render, or to cover your wall with textured paint, tiles, or brick slips. Brick slips will give your building the look of a traditional brick wall.

You must use insulation boards specifically designated for external use. Installing external wall insulation is a specialist job, that will likely require the services of a professional. Issues with external wall insulation can include the changes it brings to the walls of your building. You may need to apply for planning permission when looking to install it and may be disallowed by building regulations if you live in a protected building or area. External wall insulation is the most effective option for houses with solid walls, and it can also offer acoustic insulation for houses in noisy areas. To find out more about external wall insulation, read our guide on the subject.

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Acoustic Insulation for Stud Walls

Installing thermal wall insulation within the internal walls of your house is largely unnecessary, with heat escaping through the thermal envelope that surrounds a building. However, using acoustic insulation within internal stud walls can bring a variety of benefits. In environments with a lot of noise, like shared houses or blocks of flats, acoustic insulation can greatly reduce the bleed-through of noise, giving people privacy and comfort. The best acoustic insulation for an internal stud wall would likely be from mineral wool products, which are both effective and affordable. In offices or larger buildings, you can also use acoustic panels, which hang over a wall, absorbing sound within a room.

Our Range of Wall Insulation

Building Materials Nationwide offers a huge selection of wall insulation products, from industry-leading brands. We stock cavity wall insulation products, suitable for use in new build properties. We also have a wide range of external wall thermal insulation, perfect for a refurbishment to add additional wall insulation within a property.

For readers working in the industry, we offer trade accounts through our website. Our trade account holders gain access to our full range of products, our express delivery options, and the services of a dedicated account manager. Sign up for a trade account through our website today.

Building Materials Nationwide is here for all of your thermal and acoustic insulation needs. Shop from our range today.


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