By Simon Bones, founder of Genous retrofitting 

Making a simple 1950s unconverted bungalow more energy efficient tends to be quite straightforward, provided the customer has enough budget. But listed or otherwise protected buildings can be more difficult, and pre-1900 properties tend to be harder to insulate, while smaller or mid-terrace buildings often have restrictions. The good news, however, is that even these types of properties can often be retrofitted – though mid-floor listed flats remain pretty tricky!

The key challenges Genous customers face tend to be planning permission, sufficient space, and the cost-effectiveness and feasibility of fabric upgrades, but in most cases these can be addressed.

Planning

Planning permission restrictions for heat pumps have recently been relaxed, so in most cases won’t be needed (even in a conservation area) if noise restrictions can be met, but listed building consents are still required, albeit in our experience most heat pump consents are given as long as the design is sensitive. 

Solar can also work well even on older buildings, though street-facing arrays in conservation areas and anything visible on a listed building can be difficult. But even here, low-rise arrays on flat roofs that are invisible under parapets, or shielded ground-mounted arrays, can often be approved.

External wall insulation is often hard to get through planning in sensitive areas, but tends to be a high cost/low return intervention compared to alternatives anyway.

In all cases, having a sensible plan and working to accommodate planning constraints can get many renewables projects through planning.

Sufficient Space

Terraced homes can be challenging for a heat pump, as some lack space for an outdoor unit, but roof-mounting, placing in an enclosure at the front of the property or across a side return can all be possible.  Off-street parking is also a prerequisite for home EV charging. 

However, the good news is that a terraced house has a lower heat-loss than a detached or a semi, so can be more suitable for a heat pump if one can be installed, and insulation can still be carried out on terraced properties without impacting neighbours. 

When it comes to solar panels, these are cheaper on a per panel basis the simpler and bigger the roof is – so a small terraced property with Veluxes and dormers can be problematic here. But even in these cases, solar can often go in, though it’s better if this can be coordinated with other roof or electrical works to reduce the cost of scaffolding or electrical/cabling works. Equally, a large roof on an older building can often be a great place to put panels, and in-roof arrays (where the panels look to be built into the roof rather than being on it) can often work better aesthetically and structurally.

Fabric feasibility

Pre-1930s buildings tend to have solid rather than cavity walls, and these are seldom cost-effective to insulate unless you are completely stripping back the walls. In such cases, look to do what can be done cost effectively (loft top-up, smart air-bricks to reduce lost through a suspended floor) and prioritise renewables. Double-glazing can be hard on listed buildings but tends to have a lower effect on heat loss than people imagine and, if you really want to, even listed buildings can get low heat loss glazing.

For heat pumps, these do work on older, leakier buildings, and as long as the flow temperature can be kept low and/or they can be combined with solar and a battery, they can still save the client money. Solar panels themselves don’t depend on the age of the building, though the roof does need to be strong enough.

Making a retrofit work

Older and/or protected buildings are often less energy efficient than modern buildings, so retrofit is all the more important here. Moreover, such homes are often owned by wealthier homeowners, who can invest in their properties and afford to buy the more expensive equipment that tends to perform best. And larger homes have more space for panels, and room inside for equipment – though if the home needs two or more standard air-source heat pumps to heat it, that can push budget up.

The priority tends to be renewables and electrification rather than building fabric upgrades, but these changes can still have a material benefit on bills and emissions.

For smaller, terraced properties, fabric changes can be helpful – particularly where there are cavity walls or low levels of loft insulation – and a heat pump can often work well as long as it can be placed somewhere.

Key to all these types of retrofit, though, is understanding the options, choosing what is appropriate for the given property,  and getting experts to advise who know how to get things done and can support through planning, design and build (like Genous!).