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Spray Foam Insulation Guide

Author: Jack Lloyd
Updated: Dec 19, 2023
12 minutes read

Your home’s loft is a vital part of your home that not only increases your property’s storage space but frees up the rest of the house and creates a more comfortable environment.

So whether you are only using your loft as a storage space or have converted it into an extra bedroom, it’s important to insulate the room properly.

Without it being properly insulated, your loft can let the heat from your home escape and significantly decrease your home’s efficiency and result in your bills to potentially skyrocket.

This article will inform you on everything you need to know about spray foam insulation, why you should insulate your loft and the benefits, along with the best type of spray foam insulation.

Installer spraying foam insulation in loft

Why Should You Insulate Your Loft?

For many homeowners, loft insulation isn’t a priority because some find it to be unnecessary and without insulation you can have a little more storage space.

In the long term though, insulation is important because it balances your home’s temperature and humidity.

Particularly as heat rises and if your loft is without or not properly insulated, it won’t take it long to escape.

Insulating your loft will solve all this and there are several types of insulation available on the market. You can choose one that best fits your needs and budget and ultimately protects your home.

With insulation you can delay or prevent heat loss from the loft, it also reduces bills and makes your home much more environmentally friendly.

Insulation might sound like an unnecessary spend at first but this investment can last for over 40 years. So, it will eventually pay for itself within just a few years and increase the overall market value of your property.

The Best Loft Insulation: Which One Should You Pick?

There are several kinds of insulations on the market that are tailored to fit every homeowner’s needs and budget perfectly.

When considering the best type of insulation for your loft, you should pay attention to the following factors:

  • Does your loft have humidity or condensation issues?

  • How accessible is your loft?

  • How much space are you hoping to save?

  • What is the climate in your area?

  • Depending on how thick you need your insulation to be an dhow resistant to moisture, you can choose a few different types, such as:

If you’re looking for a more traditional way to insulate a loft, then fibreglass and mineral wool are the most commonly considered. These methods are simply layered between the lofts' joists to achieve the desired depth.

However, spray foam insulation is a more efficient way to not only protect your loft, but enjoy your investment for longer and balance your home’s internal temperature.

The Best Type of Loft Insulation: Spray Foam

For homes with lofts in the UK, spray foam is arguably the best way to insulate your home.

Spray foam loft insulation is a great alternative to fibreglass or mineral wool and will enable you to completely seal your room, preventing any heat loss.

Unlike fibreglass or cellulose, which need to be layered to achieve the maximum depth, spray foam doesn't require much space.

When applied between the joists, it will expand by 100x and fill any gap or corner, completely sealing the room and creating an airtight layer.

By creating an airtight seal, spray foam can lower your bills by up to 50%, as well as prevent heat loss and keep your home cool in summer.

Compared to other forms of insulation, few seem to match spray foam's efficiency. Plus, it comes with a 25-year manufacturer’s warranty.

You can see how different kinds of insulation compare based on their R-value in the graph below.

What Is Spray Foam Loft Insulation?

Here we have explained spray foam insulation and how it works.

Spray foam is a liquid foam that a specialist will spray between the room’s joists and over the planks. When applied, the foam will then expand and begin to fill any gap, tight corner, or unevenness on the joists.

While this kind of insulation isn’t new, in fact it’s been on the market for around 30 years, it has only started to see momentum over the past few years. This is due to homeowners looking for more efficient ways to insulate their homes.

There are two main types of spray foam insulation: open and closed cell foam insulation.

Open Cell

Open cell is a type of spray foam used for surfaces which need breathing such as wooden roofs and lofts.

It’s less dense than closed cell and stays soft after setting and for homes with wooden timbers, it provides better insulation.

Airflow is also reduced so it can be efficiently used as a soundproofing layer. It is also not as susceptible to condensation as closed cell foam.

Closed Cell

Closed cell insulation is used on surfaces which do not need to breathe such as metal surfaces. Plus when it’s rigid, it can strengthen the loft's structure.

When this spray is set it has a myriad of gas pockets in its structure, which helps prevent heat from escaping.

One of the main disadvantages of closed cell spray foam is that it is a vapour barrier and won’t let the air out. Meaning that to prevent condensation, you will need to regulate the humidity levels in your room.

Benefits of Spray Foam Insulation

Spray foam insulation has several benefits that have helped make it the number one choice for many homeowners.

With fluctuating house prices, some families will settle on smaller properties, meaning that every inch of space is vital.

In fact this is partially why many homeowners skip insulation altogether as it takes up space.

But with spray foam insulation, it can achieve the same effect as fibreglass or mineral wool at a fraction of the space.

Aside from saving on space, spray foam is considered a more efficient insulator than other traditional options. It creates an airtight seal around the loft's perimeter and stops heat from escaping.

Here are the most important benefits of spray foam insulation:

  • Requires less space to be as efficient as traditional insulation

  • It will help you save up to 50% on your energy bills

  • It can also help with soundproofing

  • It can also be breathable and waterproof

  • Great for cracks, cavities and corners.

For information on how much does roof insulation cost, see our guide!

How to Insulate a Loft With Spray Foam

In order to be as efficient as possible, mixing spray foam must be done with great care, otherwise it is ineffective.

Therefore, it is important not to attempt to install spray foam loft insulation yourself.

Although you may be able to make short-term savings when you attempt spray foam insulation installation yourself, there’s a big chance something may go wrong during the process. If your installation isn’t of sufficient quality, you could damage the plasterboard inside your home, and you may face big problems with mould. It may cost you a great deal of money to put things right if you don’t carry out the installation properly. Unless you have a great deal of experience in this area, it’s much better to leave things to the professionals. Installing spray foam insulation can require a great deal of skill and expertise.

It’s best to hire a professional to ensure the most efficient spray foam insulation installation. When done correctly, spray foam insulation can really create a better living environment for everyone. It will also reduce your energy bills.


This spray foam insulation guide should have now given you a detailed insight why you should insulate your loft, the best spray foam insulation to choose from and the various benefits of using spray foam insulation.

Spray foam loft insulation is an efficient and extremely convenient way to insulate your loft that's not only long lasting but will make your home more energy efficient.

It will save you a considerable about on your energy bills, saves on space, helps with soundproofing and helps to create a better living environment for everyone.

If you would like to know more about spray foam insulation, all you need to do is enter a few details and one of our experts will be in touch shortly to help advise you on the best spray foam insulation for your home.