It’s important to recognize the age and construction of the building you are renovating. There are significant differences between how some older buildings and modern buildings will respond to insulation and airtightness.
Older buildings in Spain with thick solid walls may have been built with permeable fabric (stone, earth and brick) that both absorbs and desorbs moisture – a breathing building. This is in contrast with many modern buildings that are constructed with impermeable materials designed to exclude moisture. The introduction of impermeable materials and barriers such as cement plasters and vapour checks to an old solid wall building will change the performance of the building and may introduce new problems.
The real dangers of introducing inappropriate materials to solid wall buildings have not yet been fully appreciated by those advocating the external insulation of solid walled buildings with systems that use cement based renders. Introducing insulation and increasing airtightness levels to this kind of building, in particular to the levels required to make the energy savings claimed, has not yet been proven over time. We do not yet know the long term implications of introducing insulation to buildings that were constructed and designed without insulation and airtightness in mind. The use of cement based renders will impair the ability of solid walls to breathe and increase the levels of damp within the wall and put timbers in contact with the wall at risk of decay.
There are similar issues with the introduction of internal insulation which needs considerable care and attention to detail if it is to be effective and does not create new threats to the condition of the buildings.
Author: John Wolfendale
Bio: John is a founder of Eco Vida and is passionate about bringing modern design and construction practices to Spain. He believes a home which is warm in winter and cool in summer is largely a matter of design and selective use of materials. He is British and a Chartered Surveyor with 18 years experience living and working in Spain.