Addressing Issues of Sustainability and Carbon Footprint when Working in Listed Buildings
Historic buildings can be difficult to find ways to improve the energy efficiency, since the fabric of the building is what gives the building its value. For example, it is not possible to insulate a solid stone wall without directly affecting its appearance. It’s therefore required to look for improvement opportunities that can be hidden away and do not impact the character of the building and its setting.
Millar + Howard Workshop have recently completed the refurbishment of a Grade 1 listed manor house in the Cotswolds, in which we had the opportunity to find ways to improve the buildings sustainability and carbon footprint. Some parts of the original building date back to the fourteenth century, retaining centuries of historical interest. The building was historically known for being cold and damp due its shaded, west facing location. Our clients’ primary aim for the project was to make the building warmer and more inviting, whilst preserving the historic feel and character of the property.
Following extensive surveys and modelling of the building a heating strategy was developed with the specialist mechanical and electrical engineers. The analysis found that there were only enough radiators to emit approximately a quarter of the heat output being produced by the existing oil boilers serving the property. A plan was therefore developed to provide better heat output throughout the building. This was achieved throughout the property with the replacement and an increased number of new more efficient cast iron radiators, which were sized and positioned sensitively throughout the house. However, the ground floor offered the added advantage of the potential for underfloor heating. The existing floor finishes included a mixture of timber floor boards and stone flags. By carefully dismantling the floor, the existing finishes were recorded, lifted, stored and protected. The floors were then dug out to reduce levels to provide space for a new floor construction. Archaeologists were on site during this process, recording the existing floor make up and any features discovered during the excavation works, which were all carried out by hand.
The new floor construction was then installed, comprising a 150mm limecrete slab with embedded underfloor heating pipes, over an insulating 300mm layer of Glaspor, which is a recycled foamed glass gravel. This system offered the additional benefit of a breathable construction, with its non-capillary active closed cell structure providing the moisture protection, whilst remaining vapour open. It is important to maintain a moisture balance within the floor slab, since historic buildings will typically have no damp protection. If a modern concrete slab had been installed, the rising moisture would have been forced up through the fabric of the walls, likely resulting in the failure of internal plaster finishes. We also took the precautionary measure of installing a french drain along the rear of the building, to reduce the amount of moisture passing under the building.
With the support of the clients, we were able to replace the old inefficient oil boilers with a ground source heat pump, which was sized to feed the new underfloor heating system, hot water supply and low temperature supply to the radiators during the milder times of the year. A smaller modern oil boiler system was then installed to provide a heating boost during the winter months. The ground source system involved the installation of 15no. boreholes that went down 140m each into the ground. Harnessing natural heat from underground by pumping water through it in pipes, the heat pump then increases the temperature, and the heat is used to provide the heating or hot water.
The roof was also targeted where possible for thermal improvements. We were able to install 300mm of loft insulation to the roof voids to help hold on to the additional heat now being provided to the building. This would appear to be a simple exercise, but by creating a greater temperature differential between the heated rooms and the cold roof space, condensation is more likely to occur within the loft space. Fortunately we were also refurbishing the roof as part of the project, so we were able to install discrete ventilation at the eaves, allowing air to pass through the loft and remove excess moisture. It is also worth noting that the roof contained 16no. bat roosts which had to be protected, following receipt of a licence from Natural England.
The manor incorporates a large medieval hall, which is open to the roof structure above. There was no opportunity to insulate internally, but we were able to install a 35mm thick board of wood fibre insulation over the roof without affecting the external aesthetic of the building. The wood fibre board is also naturally breathable and so compliments the historic natural materials of the roof. The amount of insulation may have been fairly thin, but the benefits will be felt in the hall below, with the temperature being a few degrees higher. The effectiveness of the measures put in place, continue to be monitored in order for us to gain further understanding of them and so we can make any appropriate recommendations to other clients with ancient or listed buildings.
We believe that by gaining a detailed understanding of a building, we can make the right decisions to improve the fabric of the building and preserve the building for future generations. Historic England have produced a series of detailed guidance notes relating to improving energy efficiency in historic buildings and the issues to consider. These can be found on the Historic England website.
We enjoyed working with Greengauge for heating design, Hutton + Rostron for building forensics. It was also a pleasure to work alongside the skilled craftsmen of Ellis & Co.
