Keep the heat in with solid wall insulation
What kind of walls do you have?
To clarify whether you have a solid or cavity wall, take a look at the brickwork. In a solid wall, the brickwork will be laid in an alternating pattern - some lengthwise and some crosswise - while a cavity wall will have all the bricks laid lengthwise. Another trick is to measure the width of the wall. Solid brick walls are usually around 22cm thick, while a solid stone wall can measure up to 50cm.
If your home is a steel-frame or timber-framed building, or made from prefab concrete, consult a professional to help you figure out what kind of walls you have.
How much can you save with solid wall insulation?
According to the Energy Saving Trust, the typical cost for insulating a solid external wall is around £12,000, compared to £7,500 for an internal wall. For this price, a company will come in, perform the entire insulation process, and then fix everything back up the way it was.
In terms of savings, you’d be able to recoup £660 a year on your energy bill if you have a detached house, £380 a year if you have a semi-detached house, and £180 in a mid-floor flat.
There are also ways of mitigating the cost of solid wall insulation. If you’re already having building or decorating work done - for instance, if you’re getting a new kitchen - installing internal wall insulation at the same time can shave a lot off the price.
Similarly, if you’re installing solar panels or getting a new roof put in, you can kill two birds with one stone by opting to get your external wall insulation done too, as having the scaffolding up already will cut costs. Or, if your walls are in need of repair, it’s worth looking into an installer who can handle this plus the insulation at the same time for a better deal.
Installing internal wall insulation
Insulating your walls from the inside is the cheapest of the two options, but be aware that it will make your rooms slightly smaller, as it involves padding out the walls with around 100mm of insulation.
Your installer will either fit rigid insulation boards to the wall or build a stud wall, and fill the gaps with an insulation material like mineral wool. The doors and skirting boards, as well as fittings like radiators or sockets, will need to be temporarily removed. You won’t be able to use the room where insulation is being added - but it can be installed in one room at a time to minimise the hassle.
Installing external wall insulation
Because it’s installed outside the building, external wall insulation is a far less disruptive option. It can also bring other benefits, like improving the appearance of your home and making it more weather resistant, reducing noise, and preventing damp. However, this type of insulation comes with a higher price tag than applying it to an internal wall.
You might need planning permission for external wall insulation if you live in a national park, conservation area, or world heritage site, as it may change the way the building looks - although you can always choose to replicate its original appearance.
Avoiding poor ventilation
Uninsulated solid walls allow for good ventilation because vapour can easily pass through them. So, while it’ll keep your home warmer, insulation can cut off this flow and increase the risk of condensation, damp, and mould.
First off, it’s crucial you make sure there’s no issues with damp in your walls before you start insulating, as this will lead to serious problems down the line. You should also seek out breathable insulation materials and finishes - speak to your installer about the best plan of action for your home.
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