Achieving balance between energy efficiency, comfort and ventilation
Steve Hodgson, Chief Executive of The Property Care Association argues that buildings, irrespective of when they were built and with what, need to find the right balance between energy efficiency, comfort and ventilation…
The UK has a rich and diverse range of buildings that make up the housing stock. We have found ways to adapt very old buildings to styles of modern living and have adopted ideas and technologies developed for cutting edge architecture into historic structures.
On the whole this melding of old buildings with the needs of modern occupation has worked remarkably well. After all, these buildings are still standing and are more desirable than ever. It is true however that in a significant number of cases things can and do go wrong. We would also assert that the number and severity of some of these conflicted dwellings may be growing.
It is accepted that all occupied buildings must deal with the moisture created by occupation. In older buildings they dealt with that water very well because they were very leaky! Doors were fitted roughly into frames, timber windows let in draughts, there were open chimneys in most of the occupied rooms, a kitchen stove was fuelled with wood or coal for heating and cooking, ceilings and roofs lacked insulation and promoted very rapid air exchange. On the downside these buildings were colder and took large quantities of fuel, especially if you wanted to get them to a state that we in the 21st century would consider warm. They were also usually affected by damp. The replacement of lime plaster with other products and the presence of historic infestations of wood destroying insects in old wood are, in part, testament to that.
On the upside, the natural condition of these structures meant that atmospheric moisture did not build to a point where problems could occur. The moisture was simply flushed out through the holes. We are deluded if we think the moisture was able to escape through the fabric of the buildings. The walls were not designed to “breathe”. The building was just not capable of retaining heat or moist air.
Moving on to modern living and the situation we exist in today, and we are forced by both regulation and our wallets as well as our understandable desire to live as comfortably as possible to eliminate the loss of energy through the building, to stay warm and burn less fuel. This has for the most part been achieved through the adoption of modern technology. The doors now fit, the windows now close tightly (even refurbished timber box sashes can be completely draft free), bedroom chimneys have been eliminated or bunged-up, there is insulation in almost every roof space and the solid fuel cooking stove has been replaced by an electric oven. Our buildings, no matter how old, no longer leak like they used to.
The way we occupy a building has changed too. We no longer bathe once a week in a tin bath in front of the fire. People now expect to be able to shower in hot water at least once a day. We spend longer indoors, and when at home we expect to be able to wander from room to room in a t-shirt and remain comfortably warm.
In essence, we have reduced the ventilation while massively increasing the moisture loading of the air. So, in this situation, it is no great wonder that the vapour pressures now being seen in occupied buildings are resulting in more problems associated with atmospheric moisture finding itself deposited in, or on the surface of walls, within roofs and on floors.
We must retain a huge respect for the skills and knowledge of craftsmen and builders that came before us, but I am also utterly convinced that they did not select building materials because of their vapour permeability. They didn’t build houses to “breathe.” They built houses that leaked.
The problems associated with moisture moving through otherwise solid structures in poorly ventilated older buildings has been hijacked in recent years. It seems that evangelical exponents of the breathing house must be seen to place the blame for the growing number of damp related problems that we see in older buildings at the feet of the preservation industry or modern unsympathetic building practices. If only things were this simple.
In a perfect world, a house would be built without defect, it would be occupied by people who maintained and cared for it as it was built. It would not be abused, altered or changed. It would not be overcrowded, extended, damaged or modernised. In an ideal world it would be preserved in aspic and time would stand still.
In reality, occupants across the generations change expectations. Materials, performance, technology and economic imperatives change. Buildings get altered, things break, fires and floods happen, alterations, updates and remodelling have always been aspirational and will always be led by fashion, need, and cost rather than the technical characteristics of the component products.
The adoption of high performance man-made building materials in predominantly traditionally built homes has been good and bad. Their adoption has meant we live more comfortably in houses that are warmer and use less energy, they are less affected by rot and the plaster doesn’t need lime washing every three years to mask the damp stains. On the downside, we are finding new problems that are more to do with the elimination of air exchange in otherwise dry buildings than they are to do with the air permeability of individual construction products.
Needless to say, the use of impervious finishing on the exteriors of masonry buildings regardless of age or architectural merit is abhorrent. The reason for our disgust is not some woolly-minded notion that it will prevent gas escape, but rather the fact that they will not be perfect. Renders, paint, coating and claddings will fail. They can never be expected to be perfectly monolithic and they will crack, suffer weather impact damage or be perforated at some point. They will fail and when they do water will get in behind them and will not find it easy to get out. The results can be severe deterioration to the fabric of the building both internally and externally. To my mind, cavity wall insulation is a practice that has the potential to encourage the deposition of atmospheric water within the wall over a long period of time. It is my belief that the issues we may face in the future as a result of external solid wall insulation (that changes the temperature profile in the original wall) are as yet unknown.
The Property Care Association has taken a great deal of time and care to understand the processes involved in the way a building becomes wet, and its members have been dealing with problems successfully for many years. That said, times are changing. The rate of change, driven by the need to use less heating energy and changing styles of occupation mean we must continue to learn and adapt our diagnostic processes as well as the solutions that we deliver.
To that end we are using industry money to fund research and hope that by the middle of this year we will have embarked on a three-year Knowledge Transfer Partnership with University College London.
In Conclusion:
Buildings that can’t release the water that has been generated within them develop problems. Buildings, irrespective of when they were built and with what, need to find the right balance between energy efficiency, comfort and ventilation.
Impervious materials should never be applied over porous external finishes. This will almost always cause problems in time. We also know that rising damp has been observed and independently studied, on every continent of the globe other than Antarctica. That is fact. There are still those who for their own ends very vocally continue to refute its existence. This I think says more about their commercial interests, lack of research and experience than it does about the legitimacy of those who recognise and help manage the problem in affected properties.
We know that the practitioners who consider themselves the protectors of historic buildings and refer to people like me as “damp proofing Noddies” will come to recognise that we all want healthy buildings, dry homes and happy clients.
While some may take a “preserve buildings as they were approach”, we must also acknowledge that most occupants of even important historic structures, want to live in warm, dry, well-appointed homes. It is my view that this balance must be found between modernisation, heritage and performance and that this can best be achieved if we all work in partnership rather than in a state of perpetual conflict.
Published in Planning & Building Control Today on 11th April 2016 – page 124
Also: published in Planning & Building Control Today on 29.01.16 (on-line edition)
Published in Planning & Building Control Today on 11th April 2016 – printed edition April 2016 page 124