Could retrofitting insulation be the answer to a warmer home but lower heating bills? This is what the pros told me

It's that time of year again when we all start looking for ways to keep warm at home without necessarily sending our energy bills soaring by blasting the central heating all day long, only for it to escape outside through walls, roofs and draughty gaps around windows and doors.

Whether you live in an old house or something more modern, finding ways to heat your home without turning on the central heating will help so much when it comes to saving money on your household bills – and ensuring your home is properly insulated is one of the best methods around.

That said, retrofitting insulation is not always as straightforward as it might sound and in some cases, the financial benefits are not as substantial as you might think. If this is a job you are considering, check out what the experts had to say on the topic first – it might just save you a lot of disruption.

Is it worth retrofitting insulation in an old house?

If you are looking at ways of keeping an old house warm without central heating, adding insulation might well be something you are thinking about – but is it a job worth doing?

Becky Lane, CEO of Furbnow, explains that while it is definitely worth considering, there are few factors to assess first if you don't want to cause other issues, such as damp, by carrying out the job.

'With an old house you really need to understand what you’re dealing with before you start,' she says. 'Traditional and older buildings, particularly those built before the 1930s, were designed to manage moisture by allowing it to pass through the walls. You can’t just put any insulation material on any wall. You have to determine what the construction of the wall is before you do anything – make your home more airtight without adequate home ventilation and you’ll trap moisture inside.'

Martyn Fowler, founder of Elite Renewables, agrees that you need to do your research about how to insulate your home and that care needs to be taken before rushing ahead and installing any old insulation. 'Older houses are often where insulation can make the biggest difference because so many of them were built with very little insulation to begin with.

'However, I wouldn't rush into insulating everything without understanding how the house was built. A Victorian solid-wall house behaves very differently from a 1930s cavity-wall property, and what works well in one could cause problems in the other. The biggest thing I'd look at is how the building manages moisture. Older solid walls often need to be able to dry out, so choosing the wrong insulation system or installing it badly can lead to damp problems later on.'

Becky Lane

Becky Lane is the co-founder and CEO of Furbnow. She is also a board member at the Sustainable Housing Action Partnership – a not-for-profit organisation promoting best practice on the environmental, social and economic aspects of sustainable housing.

Martyn Fowler

Founder of Elite Renewables, Martyn Fowler is one of the UK's leading renewable technology experts, working with heat pumps for the last 2 decades. His passion for decarbonisation matched with a deep technical experience of the technology make him one of the industry's go-to experts for all things renewable.

How disruptive is it to retrofit insulation?

One of the things that puts many people off retrofitting insulation is the amount of mess and disruption it can cause – so what should you expect if you are mulling over going ahead with the job?

'It completely depends on the type of insulation,' picks up Becky Lane. 'Loft insulation is relatively straightforward and cavity wall insulation is a same-day, minimally disruptive process – typically completed in two to four hours with no internal disruption and the property can be occupied throughout.'

'With cavity wall insulation, installers drill small holes in the external walls, inject the insulation and then make good the holes afterwards,' adds Martyn Fowler. 'Internal wall insulation is a much bigger job. You're working inside the rooms, so radiators, sockets, skirting boards and sometimes kitchens may need moving. The walls then need finishing and redecorating, so you should expect some disruption.'

'The disruption can be managed with clear planning and communication,' advises Becky Lane. 'Rooms need to be cleared out. Dust finds a way into everything, so valuables and anything precious should be removed from the working area. The upside is that you can do it in phases – room by room over a period of time – which helps if your budget does not stretch to doing the entire house at once.'

'External wall insulation keeps most of the work outside,' adds Martyn Fowler. 'But you'll usually need scaffolding, and things like downpipes, window reveals and external fittings may need adjusting.'

Are some types of insulation easier to retrofit than others?

It is worth bearing in mind that certain types of insulation are going to prove less disruptive or complicated to install than others, as Martyn Fowler explains. 'Loft insulation is usually the easiest place to start. Cavity wall insulation can also be fairly simple, provided the property is suitable. You need to check the condition of the walls, exposure to driving rain and whether the cavity is clear before filling it.

'Solid-wall insulation is more involved because you're adding insulation either inside or outside the existing walls – internal insulation affects the room itself, while external wall insulation changes the appearance of the outside of the building.

'Floor insulation is another one where access makes a huge difference,' adds Martyn. 'If you've got suspended timber floors and can get underneath them, it can be relatively straightforward. If you're dealing with a solid concrete floor, you may be looking at lifting and rebuilding the floor, which is a much bigger project.'

Where are the best places to retrofit insulation?

It is important to understand which locations around the house will make the most difference in terms of saving energy in your home when adding in insulation if you want maximum benefits and to avoid wasting money.

'I'd normally start by looking at the loft and the external walls, because those can account for a substantial amount of heat loss in an uninsulated house,' says Martyn Fowler. 'If the loft has barely any insulation, that's often one of the most cost-effective improvements you can make. Warm air rises, and you don't want all that heat escaping through the roof. I'd look at the smaller details as well. Loft hatches, gaps around pipes and poorly sealed windows can all let warm air escape. There's not much point spending thousands on insulation while leaving obvious draughts untreated.'

'Floors are often forgotten,' adds Becky Lane. 'It might sound counterintuitive, as heat rises, but you can typically save 10–15% with proper floor insulation, and cold floors have a big impact on how comfortable a room feels. The important thing is doing the big things in the right order. Insulation, ventilation, then heating. That’s how you avoid ending up with a warm but mouldy home.'

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Will retrofitting insulation make a house feel warmer?

One of the driving factors in why people decide to upgrade their insulation is increased comfort levels – but how much warmer will it actually make a house?

'A lot! Particularly if the house has very little insulation at the moment,' says Martyn Fowler. 'It makes it easier for the space to hold the temperature and the internal surfaces become warmer. That makes the room feel much more comfortable, even at the same air temperature.

'I wouldn't promise that insulation will raise the temperature by a certain number of degrees, because that depends on the type of heating and the weather,' adds Martyn. 'The real benefit is that the house becomes easier to heat and stays comfortable for longer.'

'An uninsulated home can lose a third of its heat through the walls and another quarter through the roof,' points out Becky Lane. 'Rooms that previously needed constant heating hold their temperature far more effectively. Beyond the bill savings, you get a home that’s actually comfortable. No cold spots, fewer draughts and more even temperatures.'

How much does it cost to retrofit insulation?

Obviously you need to look into insulation costs and how much upgrading is going to set you back before you can weigh up whether it is a job worth doing.

'Cost varies hugely depending on the house and what you’re insulating,' picks up Becky Lane. 'The quickest wins are things like topping up loft insulation, which might cost around £300 to £1,000, or insulating suspended floors, which can run into a few thousand pounds. Solid wall insulation is a much bigger job. Internal wall insulation is typically around £200 per square metre and for a whole property you can easily be looking at £20,000 or more.'

'As a rough guide, loft insulation costs around £500 to £1,000, cavity wall insulation could be around £1,000 to £3,000, and solid-wall insulation can easily cost £8,000 to £20,000 or more depending on the size of the property,' adds Martyn Fowler.

How much could you save on heating bills?

If you are paying for extra insulation, as well as expecting your home to feel more comfortable to spend time in, you are likely to want to see lower heating bills. But what kind of savings should you anticipate?

'The savings depend on the house, but we typically see around £500 a year from adding internal wall insulation,' reveals Becky Lane. 'The payback period for solid wall insulation is long though. The main benefit is often not financial, it’s that the house actually feels warm and holds its heat instead of losing it through the walls.'

Simon Bones, founder and CEO of Genous, explains that solid wall and floor insulation tends to have the highest payback period. 'Solid wall insulation normally has a 50+ year payback (it costs £15,000 upwards for most buildings) unless you’re stripping back to the skin of the wall, or by insulating this you can get other benefits (like a smaller heat pump). Solid walls also need specialist materials to ensure the fabric works the way it’s supposed to.

'Solid floor insulation also has a very slow payback, unless you’re taking up the floor anyway and putting in underfloor heating,' adds Simon.

Simon Bones

Simon Bones is the founder and CEO of Genous, the UK’s premium home retrofit company. Simon has combined his expertise in climate change science and energy and infrastructure services with his personal experience of delivering multiple home retrofits to help shift the public’s mindset and bring us closer to a more energy efficient and greener future.

FAQs

How long does it take to retrofit insulation?

If you are still on the fence about whether or not retrofitting insulation is going to be worth it, understanding how long it will all take may help you decide.

'Loft insulation is generally fairly straightforward. It can usually be completed within a day, and most of the work happens in the loft rather than your living space,' says Martyn Fowler, although it is important to check how much loft insulation you need before carrying out the job.

'If you have suitable cavity walls, filling an empty cavity is relatively straightforward too,' says Becky Lane. 'A typical house can be done in a few hours.'

Retrofitting internal and external wall insulation is likely to take longer – around three to five days for internal and up to three weeks for external.

If you are going to the trouble and expense of retrofitting insulation you need to make sure that you address other areas of heat loss around the house too – pay particular attention to draught-proofing your home, otherwise the whole task will be less effective.