Thoughtful Living: how to improve the energy efficiency of your historic home

The fact that typing ‘energy efficiency historic homes’ into Google generates 532 million results is, well… A little daunting, to put it mildly. So where are historic homeowners meant to start when it comes to making good, useful and economically viable changes to the places they live? We know people are interested – a recent survey by BMG Research revealed that 90 per cent of people living in conservation areas have tackling climate change and energy use at the forefront of their minds – which makes the need to demystify things all the more pressing.

Enter Inigo’s new Thoughtful Living series. Inspired by our recent B Corp certification and our commitment to making a positive impact on the world, we want to bring you helpful and digestible guides that will empower you to make informed decisions when it comes to renovating, retrofitting and decorating. To help us, we’ll be mining our community’s wealth of knowledge, asking heritage specialists, architects, interior designers, craftsmen and suppliers to give us their expert advice on the things that really can make a difference, from draught-proofing to limewashing and more.

Historic homes, with all their creaks and quirks, require gumption in good measure. But it’s even more important, says Matthew Slocombe, director of the Society for the Protection of Ancient Buildings (SPAB) and author of our Expert Witness guides, to have an understanding that “building conservation and sustainability should go hand-in-hand.” It’s an idea supported by Historic England too, whose climate change programme director, Catherine Dewar, says: “Heritage is part of the solution in the global fight to limit climate change and its impact on people and places.” A key factor, the organisation believes, is the reuse of historic buildings, seen as one of the most effective ways to reduce carbon emissions. As we all know, second-hand is generally more sustainable across the board.

All sorts of things affect the energy efficiency of a building, from its location and orientation to the materials it’s constructed from. There’s no such thing as a one-size-fits-all approach (though one good maxim for everyone, Matthew reminds us, is: “the best way to reduce carbon emissions is to reduce energy use in our daily lives”). Working out what to do is a big task, but we’re here to help, kicking things off with some big ideas to match. It may not be sexy, but it sure is important – as is our final titbit: whatever you decide, listed status (if your home has it) may limit you; seeking comprehensive expert advice is always advisable.

Windows

Windows and what to do with them are “a real challenge”, says architect Richard Parr of RPA, who recently worked on the sustainable renovation of this house in the Cotswolds. “The issue is that thin old glass is irregular and attractive – and also lightweight. Any change to this requires a loss of character and a need for more structural frames.” His team always tries to preserve old glass, focusing instead on non-leaky frames and good shutters.

Slimline double glazing (which works thanks to an insulating gas barrier between the panes) could be an option, depending on listing restrictions. In the experience of architectural consultants Alistair and Milla Reid of Pick Our Brains, who sold through us in 2022, local authorities require applicants from listed structures to submit “detailed drawings to ensure the quality of the windows is sympathetic to the existing building.” Richard Parr’s team is also trialling vacuum-insulated glazing, which offers the thermal performance of triple glazing but without the thickness and multiple panes.

In contrast, Matthew Slocombe propounds the benefits of secondary glazing (the installation of additional windows) – his preferred approach. Not only does secondary glazing allow a building’s historic fabric to remain in situ, it also has an unlimited lifespan and can often be removed in warmer months.

Wall, floor and roof insulation

This is a complex area, Matthew tells us, “where increased condensation can undermine the beneficial effects of the insulation.” SPAB’s research shows that traditionally constructed solid walls often have a greater insulation value than modern software models assume. “Roof and wall insulation is possible in old buildings,” its director explains, “but location, detailing and choice of insulation is crucial.”

Richard Parr advises us to look up: “Whether at ceiling or roof level, there are many options for insulation materials that still allow the building to breathe in a traditional manner. For example, we’re currently refurbishing a house that uses wood-fibre insulation to achieve current building regulations for heat loss.” Aerogel quilt is another ultra-insulating and breathable product, particularly suited to areas where the roof thickness cannot increase, such as dormer windows.

When it comes to what’s below our feet, the architect thinks breathable limecrete screeds laid over a recycled foamglass insulation layer are a good choice in historic buildings that have in the past been fitted with concrete screeds, which drive moisture into the walls.

“A damp wall is an energy-inefficient wall,” Matthew tells us. But thermal improvements are not impossible in historic homes. Richard says it’s important to treat the root cause – look out for rising damp and broken gutters – and then to think about what render you’re using; modern renders can keep moisture trapped inside, whereas insulating lime plaster – as seen in this recently sold Regency cottage in Stockwell – allows walls to breathe when used both inside and out. Alistair, who also practices as an architect at AAVA Architects, and Milla often install multifoil insulation, which prevents condensation, providing a barrier to water vapour.

Other natural materials are also worth exploring, not least because of their low levels of embodied carbon. Matthew advises considering internal wood fibre or cork if you’ve no historic finishes or cornicing, or if space allows, while Alistair and Milla mention sheep’s wool too, something they’re often recommended by the “fantastic” Natural Build Co, who specify the best materials for their projects.

Solar power and microgeneration

The technology in this area is moving forward rapidly, “but the environmental cost of production and the expected lifespan need to be factored in” to decision-making, says Matthew. Solar panels – like those at Alderton Cottage, which we sold in 2022 – work best on a south-facing roof, “but it may be more sympathetic to locate them in the garden.” He warns that “listed building consent will be needed for panels on a listed building – though some councils are considering a ‘class consent’ to approve them automatically under certain circumstances.” Watch this space. And, in the meantime, think about the potential payback; 7.14KWp of panels installed at this Regency house in Wandsworth, currently for sale, halve energy bills over the course of a year.

Air-source heat pumps are fast becoming the ecological and economical standard, Richard tells us, but ground- and water-source heat pumps can be more robust in cold weather. “They feature more and more in our projects and are perfectly suited to historic buildings,” such as Sutton Hall, an ecologically updated Georgian country house near the north Norfolk coast that we sold last year.

Draught-proofing

“This is often the easiest and cheapest gain when making thermal improvements,” Richard tells us, citing brush seals for windows and doors. (He also recommends sealing any gaps.) Don’t forget that draughts can come from below too. An airtight membrane is ideal for timber floorboards – but don’t underestimate the power of a good rug either.

Matthew is keen to stress that ventilation needs to be part of the draught conversation, otherwise you’ll end up with moisture problems. With airflow, balance is key, not least when it comes to chimneys, which “should not be blocked up entirely without ventilation”. He also says a fan-pressure test, which should cost around £500, can be helpful. It tells you where air leakage is greatest so you know which areas to spend on.

Maintenance

None of the above is worth a penny if the buildings we live in aren’t looked after properly. There is a wealth of worthwhile resources available, among them SPAB’s technical advice line, which you can call for free about any old building, and the organisation’s Old House Eco Handbook. We’d also highly recommend Historic England, whose website is a treasure trove of tips, tricks and expertise. Its publications are all free to download; you can find the most popular ones here.