On Saturday I attended The Old House Eco Handbook Course in Coventry which covers the principles in the book of the same name. It was run by the Society for Protection of Ancient Buildings (SPAB) and some really interesting research and findings from actual case studies were discussed and shared. It was presented by the authors Marianne Suhr and Roger Hunt. Cathie Clarke from Heritage Skills Hub was also there tweeting about the course throughout the day. The following points are some of my notes from the course:
- A Natural Building Technologies study showed that a wall insulated with 100mm internal insulation had the same u value as a wall insulated with 80mm of insulation but which included 20mm in the window reveals – so often this is left out and it is so important for saving energy.
- Using lime mortar allows bricks to be re-used – cement mortar does not
- Single glazed windows with secondary glazing and shutters (glazed shutters can look lovely) have as good a u value as modern high performance windows (1.8 W/m2K)
- A good website for conservation glazed shutters.
- You should always use breathable insulation and breathable lime or clay plaster when renovating old buildings as this allows water vapour to pass freely from one side to the other (this is something I always do on refurbishment projects).
- It is very hard to have a vapour control layer that will truly stay vapour impermeable in walls. This is due to picture nails, electrics, shelves and anything else that may cause a punctuation in the wall. This is why breathable insulation is so important as it eliminates the need for a VCL.
- There are many ‘quick wins’ to draughtproof your home before you resort to expensive alterations.
- If a front facade has beautiful details and is mostly windows, internal wall insulation is not going to make the most difference, but upgrading windows should be first priority, while maintaining the original character.
- u values are not the only way to measure efficiency in walls. Decrement Delay is the time lag from heat passing from one side to the other. Obviously this is longer (and more efficient) the wider the wall is.
- There is up to 40% heat loss through the roof, so definitely worth insulating the loft! However with too much insulation (over 300mm) the weight of the insulation itself will reduce the air pockets within the material and it will not be so insulating.
- For the same reason, don’t tamp down hemcrete in a shuttered wall as it will also lose the air pockets that make it so insulating.
- Good rule of thumb – the more you insulate, the more you ventilate.
Jonathan Garlick from SPAB concluded with 3 things he learned when he first joined SPAB:
- Live in the house for a year before doing anything
- Work on the garden and look back at the house, working out what to do
- If you are poor you will likely be a better custodian of an old building as you will not throw a lot of money at a project, potentially making poor decisions