How to insulate a cold wall from the inside, and why the type of wall you have matters

With autumn temperatures setting in and the days drawing shorter, it's no wonder our attention is turning towards making sure our homes are set up to keep us warm. If you've noticed you have a cold wall, then you might need to take a look at how it's insulated, but can you insulate a cold wall from the inside and how do you do it?

Knowing how to insulate your home is essential if you want it to remain comfortable throughout the colder months, as is being able to spot the signs your insulation needs replacing.

But once you've seen (or felt) those warning signs, what do you do about it? I asked the experts for their tips on how you can tackle the issue from the inside, and what you need to be wary of to ensure it's done properly.

How can you insulate a cold wall from the inside?

The steps you'll need to follow to insulate a cold wall from the inside will depend on a few different factors including what type of wall you have, what's causing the problem and what your budget is.

'The first thing to work out is whether the existing external walls are solid or if they have a cavity,' explains Níall Hedderman from Real Life Architecture, 'because the type of insulation that can be applied will vary depending on how that wall was built.'

George Edwards, Managing Director of Timberwise, continues saying: 'Cold walls are a common problem that can indicate an issue with the construction of the property, such as cavity wall insulation problems.' As cold walls can create the ideal environment for damp, he suggests that you should check for signs of damp before you even think about tackling the insulation side of things.

'It is essential to treat this first, if there is a problem or the potential for one. You might think about booking an appointment for an inspection by an expert who can advise if any action is required.'

Once you have identified the type of wall you have and ruled out any damp issues, you can look at the insulation options. Remember that adding any kind of internal wall insulation will affect the dimensions of the room it's installed in.

But there are a couple of options that are worth considering.

1. Add insulation boards. 'For a more professional and overall effective approach, you should think about insulation boards,' says Paul Kerr at Beatsons Building Supplies. 'This can be a DIY project in small rooms, but for large spaces and longevity in the job, a professional should be brought on. Attaching a rigid foam or mineral wool board to the wall and covering it with plasterboard will provide adequate insulation. You can also use a spray foam under a plasterboard for a similar effect, though this is normally a task for a professional, to avoid gaps/mistakes that shorten the product's longevity.'
2. Try insulating wall coverings. 'For those operating on a shoestring budget or who would like to approach the job in a more DIY way, you can think about insulating wall covers,' says Paul. 'This isn't as effective as installing boards/foam under plasterboards, but can be a short-term technique.' You could also try applying a thermal lining paper to your walls to help reduce heat loss.
3. Apply thermal paint. While not as effective as improving the insulation of the wall itself, using thermal paint could be an inexpensive short-term solution. Don't worry if you can't find your ideal colour, in many cases you can paint over the top of thermal paint with your chosen colour and finish.

What's the best method for homeowners to use?

The best method for insulating a cold wall from the inside will depend on your specific property, so it's always worthwhile getting advice from a qualified specialist.

If you can, opt for a long-term solution, which may cost more upfront, but will be the most effective. This will vary depending on the age and construction of your home, but could involve replacing existing insulation that may be starting to fail, or adding insulation where there is none.

Shorter term solutions, like wall hangings or thermal paint, may be less expensive upfront, but won't be as impactful on the overall temperature of your room as an option that gets to the root of the problem and solves it. As such, you could see yourself spending more on these more affordable solutions over all.

Pitfalls to watch out for when insulating a cold wall

Incorrectly installing insulation could cause more problems than it solves, so it's crucial it's done properly.

If you have cavity walls, then the best course of action may be to add (or replace) the insulation in the cavity itself as opposed to on the internal wall. With solid walls, you will need to ensure you don't inadvertently trap moisture between the insulation and the wall, which could lead to damp and mould.

If you do decide on internal wall insulation (IWI) then you'll also need to be fully aware of the challenges that come along with this. 'IWI will reduce useable floor space, require the removal and refitting of internal services, such as skirting, plug sockets, switches, and radiators, etc),' explains Chris Knights, Business Manager - Building Performance Evaluation, at BSRIA. 'In addition, continuity of insulation may be difficult to achieve in areas such as the void between floors. It is, therefore, imperative that condensation risk is adequately managed, poor detailing can lead to moisture within the structure and in turn mould.'

Depending on the scope of your work, there may also be building regulations requirements that you need to meet, where expert advice will be invaluable, as Chris says: 'You should always seek specialist advice to ensure that you will achieve a thermally efficient and safe outcome. Independent experts can measure the performance before and after improvements, helping to guide design choices and make sure changes really work, without causing problems in other parts of your home.'

FAQs

Why is my wall cold?

There could be many reasons your wall is cold, so you might need to do some investigating with the help of a professional to identify the cause in your specific circumstances.

But it's likely to be one of these three main causes:

• Your existing wall insulation has failed, or it is non-existent
• You have an issue with damp and condensation, which could be caused my moisture penetration or ineffective ventilation
• There are air leaks around windows, doors, vents or electrical outlets, causing draughts.

Remember to prevent condensation and get rid of damp before you tackle the insulation so that you don't inadvertently cause further problems.