Energy efficiency in a Period House may sound like an oxymoron, but with global warming a major issue and minor annoyances such as the ongoing threat of HIPS, finding ways to conserve heat, whilst still allowing the building to breathe is an important issue.

There is now a wide selection of materials available that can insulate walls, floors and roof spaces without compromising the structure of an older property. Some are new; others have sprung from ideas of materials used in the past, brought up to date using the latest technology.

The Clock House, a Grade II listed building in Woodbridge, Suffolk has recently undergone extensive restoration works. Parts of the building date back to the 14th Century, but the majority of it was constructed in the 16th Century.  The entire house, which was gutted and meticulously restored by Rose Builders of Manningtree, now has a piece of 21st Century science of hidden away behind its lath walls.

In a large part of one external wall, Tyvek Supro, a breather membrane and air barrier from DuPont has been installed to ensure the insulation remains dry and therefore able to operate at it optimum thermal performance. The material will quickly release peaks of moisture content, preventing mould and mildew from forming. Tyvek Supro was laid loosely with traditional lath fixed over it.

Vertical timber laths were run over the top of the external frame, overlaid by staggered and overlapped horizontal laths. At the foundations, a lead tray is incorporated with a bell drop to avoid capillary action. Replacement laths were manufactured in the traditional fashion by splitting a chestnut branch and removing the centre section.

The resulting gap left between these laths is filled with a mixture of lime mortar and horsehair which, when plastered on, penetrates any gaps and slips beneath and between the laths. When this mixture dries out, it bonds to the wood strips and holds them in place. More layers are applied on top, finishing with a layer of just lime mortar. The mixture was imported ready-mixed from France, and applied using the same method as would have been done hundreds of years ago.

Although not a new material, the more recent revival of using lime in buildings and not just period properties, but new builds too, means that Limecrete deserves a mention here. An environmentally alternative to concrete, Limecrete is an excellent insulator, whilst still maintaining the vapour permeability of the floor.

Ty-Mwar has been developing its limecrete flooring system since 1998, combining materials that both simplify the installation process and improve the green credentials of the floor. It has been used in both residential buildings and in significant historic building projects such as the Chapter House Floor in Worcester Cathedral and by the National Museum and Galleries of Wales for the 13th Century Church at St Fagan’s.

There is evidence that sheep’s wool was used as an insulation material in the past, but companies such as Second Nature has taken it a step further to provide a highly efficient insulator. In summer as the fleece starts to warm up it releases moisture to have a cooling effect. In the winter, the opposite happens and moisture is absorbed by the wool insulation. According to Second Nature, Thermafleece can increase peak temperatures by up to 4c, and reduce them in summer by up to 7c, when compared to other types of insulation.

There are other natural alternatives to insulation too. Hemp is also very popular, products like Isonat work in a similar way to Thermafleece and can, claims the manufacturer increase insulation efficiency by up to 10%. Both types of insulation are available from Ecomerchant and come in batts that can be easily cut to size and because neither contain pesticides, herbicides etc they are none of the hazards of skin irritations that often come with other insulation materials.

According to Ty-Mwar the construction industry is responsible for contributing some 70 million tonnes of waste to landfill annually in the UK. The beauty of many of the insulation materials that are not only ecologically friendly to manufacture and handle today, once they come to the end of their useful life they can be recycled too.