RICS Surveyor in France. Go ‘green’ with period property and ventilate, ventilate, ventilate!!!

As a RICS Chartered Surveyor in France, I see that one of the largest causes of damage and degradation to houses is caused by the presence of damp. This in turn creates the perfect environment for wood rot and wood boring insects that can cause a huge amount of damage to timber structures. Damp in masonry may cause spalling and degradation of stonework and ‘blowing’ of render, in addition to corrosion of steel reinforcing rods within concrete structures. As the steel rusts it expands and the concrete surrounding the steel becomes detached. This compromises the structural capability and ultimately leads to failure.

All to often I see examples of damp being introduced to buildings as a result of modern building materials and repairs being inappropriately applied to houses of traditional construction.

However, there is an enormous and ever increasing promotion of so called ‘energy saving measures’ that seek to reduce energy consumption and CO2 emissions from houses. Despite the degradation caused by damp, ironically these initiatives often promote the eradication of drafts with the installation of modern windows that seal without any air gap, the introduction of draft seals and huge amounts of insulation to lofts.  Whilst such advice is well intentioned, sadly the logic is flawed and counter productive when applied to traditionally constructed properties. The reason is that older properties often have solid stone walls and floors, without damp proof course or cavity. The design on construction was to allow the damp to escape from the house via gaps in windows and beneath doors and through vapour permeable materials. This allows the house to ‘breathe’ and remain dry. This in turn allows the house to remain free from wood rot and insect attack etc.  

Even ignoring damp ingress through leaks etc, the production of water vapour can be huge from every day living including breathing, showers, cooking etc. From these every day activities, 4 occupants within a house will typically produce approximately 5 litres of water per day. So 150 litres of water carried within a much larger volume of air needs to be ventilated out of the house every month, otherwise water will be absorbed into the plaster of walls and timber joists etc. In addition of course the natural dampness from the ground, and building fabric needs to be extracted from the house.

Ironically the result of the ‘energy saving measures’ results in reduced ventilation that in turn can result in degradation of the building fabric. This may then require extensive timber and other repairs to be needed. These repairs including the replacement materials are likely to result in the consumption of much more energy and production of more CO2 emissions than the ‘energy saving measures’ could ever have achieved. Furthermore, the financial cost of the repair works is likely to be significantly more than any perceived energy cost saving.

When undertaking a Survey in France, I take account of the construction method adopted in the house that will influence my corresponding approach and advice as to ventilation. When undertaking RICS Surveys I also provide forward looking recommendations and care plans that will help keep the structure dry and thus naturally resilient to wood rot and insect attack, and also preserve the masonry. Accordingly the house will also be more environmentally sustainable. These principals will be valid at the date of the Survey Report and equally valid for generations to come.