Yes, it certainly is; but only when approached holistically. Unless you think about your home as a

complete system, changing one element with a view to retrofitting it, may affect other areas and cause

unexpected problems. Before embarking on an energy efficiency project for your old property, you need

to come up with a complete retrofit renovation plan to avoid unwanted and unintended consequences.

Doing one thing on its own can often have unintended consequences which can give you additional

risks. These include interstitial condensation (condensation inside the construction) because of poorly

designed additional insulation, and could damage the building and encourage mould growth out of

sight; thermal bridges, which can lead to cold spots and provide surfaces for potential condensation and

unhealthy mould growth; and reduced air quality due to the lack of a carefully designed ventilation

system.

The risks also vary based on the type of building you have. They’re far greater when it comes to a solid

wall construction than a cavity wall home, as the existing walls are dealing with external moisture as

well as moisture from internal humidity from occupation.

Phase your plan

By following a phased plan, you can mitigate your risks and minimise any negative impacts on your

home. Working towards an end goal and deciding what you can afford to do within a framework is very

important. You should decide what your retrofit renovation aims are; comfort, energy saving or carbon

reduction? Different measures will have different impacts. Airtightness works, ventilation and triple

glazed windows give the best improved comfort; whereas replacing your gas boiler with a heat pump

will see a big carbon reduction – but may not deliver a return on investment as quickly.

Good is better than perfect

We always recommend starting with the fabric of the home first; and do this to the best standard you

can afford. Let’s say you insulate the roof of your home, but not to a very high standard. You’re unlikely

to ever go through the upheaval to revisit the insulation so that performance is locked in. You can

always add solar panels to the same roof at a later date. Good, rather than perfect, is probably the way

to go for most people. Find the right balance between cost and benefit and don’t let not beong perfect

put you off doing the work.

Use natural insulation, like wood fibre, when you can. They’re breathable and cope with internal

moisture well. If you add plastic insulations, especially internally, they can trap moisture in the

construction, whereas natural fibres will absorb atmospheric moisture when it’s high relative humidity

but then will dry out again when it’s low relative humidity, keeping this risk low.

Better air quality

Air quality is hugely important for your and your home’s health. In most houses we only open the

windows and doors in the summer months, with all the other air coming through the cracks in the

construction, lowering the quality of the air you breathe. Making the building more airtight and adding a

mechanical ventilation system with heat recovery, while not cheap, is a good way of gaining excellent air

quality and not losing any heat in the winter.

The cost of sustainability

A typical retrofit will cost between £800-1,000 per m 2 , while an EnerPHit project (the Passivhaus retrofit

standard) reaches £1,300-£1,400 per m 2 . Compare that to a baseline of £1,650 m 2 for a new build and it’s

not the most attractive option cost-wise. While it does depend on where you live, it’s unlikely your

house will be worth what you’ve spent on it. The payback in bills is not short term either. You also need

to bear in mind the disruption. If you’re doing some light touch work, you can stay in the house, while if

you’re ripping everything out, you should take into account the temporary moving costs.

Reducing embodied carbon

Retrofitting your property is better than demolishing and rebuilding, as far as embodied carbon is

concerned. This term refers to the energy emitted during the construction of a house, generated

through production, transport, use and disposal of the materials used. The benefit of working with an

existing building, rather than a new build, is that a lot of the embodied carbon that was used in building

that structure in the first place isn’t thrown away; it’s kept and you’re only adding a small amount

compared to a new build.

There are many reasons why people decide to retrofit houses which fall short in terms of space, lifestyle

and performance, and saving energy and money can be among them. When done correctly, retrofitting

can provide you with low energy living, comfort and health, without the pain of moving.

For more information and guidance on retrofitting homes, why not visit the London Homebuilding and

Renovating Show, 30 September – 2 October 2022 at ExCeL, London.

- Paul Testa is director HEM architects and a retrofitting expert for the London Homebuilding and Renovating Show.

Is retrofitting the solution for old homes facing rising energy costs? - Paul Testa