Well it's a Monday afternoon on week 9 of my 15 months Low Carbon Cottages project and it's been a whistle stop tour of traditional building knowledge, retrofit, carbon footprinting, frameworks and conferences. I am still standing and keen as a bean! However
It's all about breathability. Most new builds (say post 1920) have cavity walls, and by that I mean they have an outer and inner shell of brick that allows air or better still insulation to decrease the ability of heat to be transferred through the walls and escape. This means that if less heat escapes, the less heat that needs to be created (through your energy bills) to keep the house at an acceptable level. It is also routine to ensure the bricks used in making these walls do not allow moisture in through non permeable membranes and damp courses etc., as wet walls are technically more thermally inefficient, if you have every worn a wet woolly jumper in the wind you'll know what I am on about.
Most traditional buildings, i.e. built pre 1919 have solid walls with no cavity, but usually are very thick to overcome this, rough rule of thumb the thicker the wall (of the same material) the less heat can escape through it. However there is moisture in the air, earth and obviously rain and with solid walls they were built in a time where water resistant materials weren't invented, so traditional solid walls absorb water from this moisture. Conversely, they can also lose moisture back out in to the external environment when it isn't as damp and also through the wall into the internal environment, which if well heated isn't an issue at all. So basically the wall breathes! Moisture in and moisture out and is all linked to the internal and external environment, and most of the time this creates a warm and healthy environment.
As we are all aware energy prices are going up, Climate change is being accepted by the majority and we have to meet Governments carbon reduction targets. So knowing this it makes sense to try and make buildings as energy efficient as possible and through retrofitting this can be achieved, but it's a bit more straight forward with new builds because they have either been built under regulations to improve the basic standard of thermal efficiency and also you can fill your cavity with insulation or use external wall insulation. Whereas Solid walls need a bit more consideration and care.
Unfortunately, there have been lot of examples where people have tried to retrofit their traditional buildings applying modern ideas of water permeability and this creates a huge problem; Interstitial condensation. When you have a solid wall that allows the flow of moisture and add modern insulating materials that have a non-permeable membrane (you have seen huge sheets of yellow insulation will a shiny foil on one side, that's what I am on about, amongst other modern insulation types too) this traps in water. If your wall is used to breathing and you cover it up one side it's like losing a lung, it gets a bit hard to breathe and this causes a build-up of moisture between the wall and the insulation. Water = rot and decay = bad news, which can be very costly to repair and also replace all the good work you were trying to do.
People need to know that traditional buildings have different needs, they need to breathe, you can still improve the thermal efficiency of traditional buildings in many different ways, using breathable materials such as sheep wool, lime/hemp, flax and other permeable systems in the loft or roof and also on walls, but you must always get a professional to assess the risk of interstitial condensation.
And without sounding too wishy-washy why on earth would you want to covered up the beautiful building styles we have in Cumbria, imagine losing the detailed yet individual grey stone work outside your house, or early Victorian detailing on terraced red brick houses, or Tudor style black timbre frames with their white infill or the lovely rough undulating features on the internal wall of some of Cumbria's most stunning cottages, these heritage and cultural values need to be embraced, protected and managed not accidently put at risk. More often than not these features are why people want to live in these types of homes, or stay in these types of building, we all love a bit of character and you don't want to lose that value. Responsible retrofit is possible in traditional buildings and that's what the Low Carbon Cottages programme is aiming to fully understand, provide guidance on how to be sensitive to this issue and still have an energy efficient holiday cottage.
From a recent governmental report, in the North West you can improve the value of your property by up to 27% by improving its Energy Performance Certificate (EPC) rating, so why not have the best of both worlds! Decrease cost, decrease emissions, increase property value and increase customer satisfaction.
PS we'll keep you updated with any advances in the project and when and how you can get involved! Thanks for listening to my semi-educational rant!