I was brought up while rationing was an active memory and have always been concerned to reduce waste and to save energy. My career as a plumber and then a building company owner (since 1980) consolidated my interest in older buildings and led to a substantial and life changing contract to restore a 100 room medieval manor house Wytham Abbey on the West of Oxford. 

Towards the end of the Wytham contract I registered and was fortunate to complete the part time, 3 year Diploma in Conservation and Restoration Course at Bristol University that covered a variety of aspects of working on old and Listed Buildings in the UK plus the legislation that applies. My dissertation “A Practical Guide for Builders and Householders working on Listed Buildings” is available on my company website www.redlandbuilders.com on the Advice page.

To distil my 12,000 word dissertation into two words, they are Breathability and Lime. Old buildings are usually single wall construction i.e. the composition of the walls are a range of materials, stone, earth, mortar etc formed at various widths adequate to support floor joists, internal walls, ceiling and roofs. The moisture content of these walls varies ,on surrounding soils, heights of ground, internally in relation to external ground, water surrounding the buildings e.g. rain, ground water, humidity etc. and coverings e.g. cement render that prevents the passage of water (unbreathable) Lime render that allows the passage of water (breathable) and impervious materials e.g. slate covering to walls in Cornwall, slate or plastic damp proof courses to arrest rising damp. N.B. I do not include injected silicone DPC which in rubble walls is completely ineffective despite being often specified by mortgage lenders. 

Modern buildings, post 1910 are often formed of two leaves of blockwork/stonework/timber construction walls with a gap between the two. The gap prevents water passing between the two layers unless compromised by incorrect cavity fill installation or inadequate or incorrectly fitted damp proof courses, wall ties etc. Cement renders enhance the external water prevention, however internally applied, they can increase water condensation in cold spots.

To summarise, all conditions, building fabric etc must be assessed and  considered before applying materials in order to achieve the desired breathability and finished surface.  

We moved to Little Clampitt in 2018 and started the retrofit project to convert a perpetually cold, damp cottage into a warm family home that after alteration, does not cost the earth in financial and carbon terms. 

The cottage is Grade II listed and is in Dartmoor National Park with all of the nature and environmental considerations. Planning and Listed Building approval took over a year to prepare before submitting the over 50 page application which took several months to approve. 

The cottage is built into the hillside with all of the inherent water issues. The new section at the rear is of modern construction techniques and includes underpinning, drainage and land drainage with damp proof membranes as required.

The flat roofed extension built in 1960, re-roofed in 1980 and 11 years past its use by date, which we wanted to change to a gabled roof at the rear to reflect the cottage gabled roof and to hide the eight PV panels in the centre. The old cottage roof was structurally unsound, now supported with cranked steel beams internally fitted in the West section of the roof. The roof and wall insulation exceed the current building regulation by at least 20% and we have been very careful to achieve air tightness around timbers, windows etc. by taping all these.

The old cob/stone walls had been rendered with cement, this was removed and lime rendered internally. The old floors were concrete on soil now 200mm of Geocell beading with 100mm of limecrete containing underfloor heating coils and covered with unsealed clay tiles to allow breathability in the old cottage.     

The cottage had been heated with an oil combination boiler that we have now changed to an 18kW air source heat pump.  The work is not yet complete but the house is already warm, light and comfortable. I plan to gather data to show the impact.