Embarking on the restoration and renovation of any home requires great care, extensive planning and a skilled team at the helm. When it’s an historic building though, or one that is listed, any work undertaken can present some rather unique challenges.
There are a number of historic, traditional timber frame properties on the Hadlow Estate which in recent years have been the subject of complex renovations. How to insulate these older homes without damaging their historic fabric has been a major factor, with rising energy bills and the property’s environmental impact also important considerations.
Every rental property in England and Wales must have an energy performance certificate, with an energy efficiency rating of ‘E’ or above. The government is proposing to raise this to a minimum rating of ‘C’ by 2025, as part of its continued drive to reduce carbon emissions. There are exemptions available for listed buildings, but this potential change is one of the many reasons why the Estate has invested in extensive improvements of its properties.
Kate Teacher of the Hadlow Estate, explains: “We want to do what we can to make our properties more energy efficient for our tenants, as well as comfortable and warm. Prior to the renovations and due to their structure, many of the listed homes we have improved were draughty and tricky to heat due to the lack of effective insulation.
“Addressing wall insulation was one of the most important ways for us to be able to improve energy efficiency. However, with listed houses there is a careful balance to be struck between improving thermal performance whilst retaining character, original materials and appearance. They can all be adapted but this depends on how the building was constructed. For example, they do not have cavities, so cavity wall insulation is not always an option.
“We need to ensure that our interventions to improve thermal efficiency don’t cause unintended consequences like internal condensation. That’s why we use breathable insulation, membrane and lime plaster, as well as breathable paint for all of this work.”
The Grade II listed Tanners Farmhouse was one of the properties to be improved. Built in the early to mid-17th century, the three-bedroom home was once a vicarage. As an ex-agricultural tenanted house, it became the subject of extensive restoration when it came back in hand to the Estate after many years.
Surveys revealed repairs were required both internally and externally to the fabric of the building. Some of these would address previous repairs to the external tile hangings and mortar, while damp issues needed to be tackled inside.
Insulating Tanners was key. As is so common with many similar buildings of this age, there was no existing insulation and so problems with draughts, damp and cold were an issue throughout.
From the outset, the Estate’s priority was to ensure all works were handled sensitively and any insulation inserted carefully, to protect the appearance and character of the building. Traditional roofing and Kent peg tile specialist Karl Terry and his team, who’ve worked on a number of the Estate’s properties, were drafted in.
Karl explains: “We used Steico wood fibre board for the insulation and this was inserted on the outside of the house. Firstly, we had to carefully remove all of the hanging Kent peg tiles, some of which featured decorative tiles in unusual patterns. These patterns were photographed and carefully documented so that they could be faithfully reproduced.
“Once we’d removed the lathes and cleared out any debris, we were able to insert the Steico boards between the exposed studwork of the original timber frame. Each piece had to be cut exactly to size as the space between each stud varied, which is common in older buildings. It’s not the easiest material to work with as it’s so dense, but it’s a very effective and breathable form of insulation.
“Breathable membrane was then fitted over the studwork and it was re-battened and the tiles were re-hung to “chalked” lines. Reclaimed tiles from the Estate were used to make up the shortfall and were carefully mixed in. It’s very rewarding to work on a building that is in need of such repair and to bring it up-to-date, so that it will go on for many more years.”
Work continued inside where the walls were re-plastered using lime plaster, which is known to prevent damp and condensation as it is a breathable material which can absorb and release moisture. Breathable paints were used throughout. Some of the farmhouse windows were also removed and repaired, before being reinstalled, to improve insulation and ensure vital heat isn’t lost.
Another of the renovations took place at Lilley Farmhouse, a four-bedroom Grade II listed farmhouse, parts of which are thought to date back to the late 18th or early 19th century. As with Tanners, it was an ex-agricultural tenanted house which had come back in hand to the Estate after almost 80 years.
Kate explains: “Due to the construction of the house and its brickwork, it was not possible to insert insulation from the outside of the property so all the insulation was inserted from within.
“Rotten lathe and plaster was stripped out before breathable insulation was fixed within the timber frame. New chestnut lathes were fitted over the insulation and the rooms were re-plastered using lime plaster and painted with breathable paint, materials which are porous and open textured, helping allow the building to ‘breathe’ and ensure that when moisture forms it can escape, preventing damp and condensation.”
A new boiler was installed along with new radiators throughout the house.
In a guidance note about insulating timber-framed buildings, Historic England explains the challenges they can present: “The walls of a timber-frame building are usually relatively thin compared with masonry and earth-walled structures. Their thermal performance varies considerably depending on construction and on the materials used for infill panels and linings.
“As traditional buildings need to ‘breathe’, the use of vapour barriers and many materials commonly found in modern buildings must be avoided when making improvements to energy efficiency, as these materials can trap and hold moisture and create problems for the building. Persistent dampness diminishes the thermal performance of a wall, and causes deterioration of vulnerable building fabric.”
The four-bedroom Grade II listed Crockhurst Street Farmhouse was also the subject of improvements to its first-floor layout, which involved the removal of stud walls, an upgrade to the bathrooms and new breathable paint throughout.
The Estate took the opportunity to insulate part of the house which was particularly cold, as it had three external single skin brick walls in the study/sitting room. This means the wall is built from a single brick layer – a feature commonly found in Victorian homes. The room was completely insulated, re-plastered using breathable lime plaster and then painted with breathable paint.
Andy Kinnear, Jay Cotton and their five-year-old son Maximilian are the home’s new tenants and they’ve been living there for about eight months.
Jay says: “It’s a great home for us and it’s lovely to live in. We moved in at the tail end of summer and as winter came, we wondered if it was going to be hard to keep it warm, but it hasn’t been a problem at all – when the house is heated up it retains the heat really well.
“We were living in a more modern 1930s semi-detached home before, which was a smaller property, but we’ve not really noticed much difference with our energy costs, if anything we are paying a little bit less.
“What is wonderful is that the house has been restored rather than changed and modernised too much. You can close off rooms you are not using which feels more traditional than newer, open plan homes. We respect that the building has been around for a lot longer than we have and as you walk around it you realise there’s so much history here.”
Not all of the works have focused on timber-framed buildings though. One Tanyard Cottages is a three bedroom end-of-terrace Victorian brick-built cottage that has received a full renovation to improve its thermal performance.
Hadlow Estate Surveyor David O’Rorke explains: “We had to tackle the roof and walls first and Steico was used in this building as well. As it’s breathable, it helps to improve energy efficiency without jeopardising the property in the long term. Loft insulation was also put in as well as a more efficient gas boiler.
“The most important thing with any historic building is that we do not end up with any unintended consequences – it is essential that breathable materials are used throughout so moisture can pass through.
“We have achieved a ‘C’ energy performance rating for the cottage, which is fantastic. It’s a big achievement that by tackling the fabric of the building to get it to a better standard, we are bringing down energy costs, reducing its carbon footprint and future proofing it for many years to come.”
The benefits of the improvements and new insulation have already been felt by those living in the homes. A previous tenant of Upper Postern Farmhouse, a Grade II listed property on the Estate, reported that after the insulation was installed, they were contacted by their energy provider to ask if they were ok and could there be a mistake, as their energy bill had fallen so much.
Kate concludes: “With all of our building and restoration programme works, we always try to balance the history and character of the building with the work necessary to bring it up to a high standard.
“Each of these projects demonstrate our commitment to preserving and conserving the historic properties on the Estate. They also highlight the great variety of talented craftsmen and women who are keeping traditional skills alive here in Kent with the techniques they use to restore and protect these beautiful buildings, so they can be enjoyed by families for many more years to come.”