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My name is Rob Veck, and I am a qualified project manager by profession. At the beginning of 2008, I had finished a major project at my company, and more of the same was on the horizon. A number of key personal events impact our lives and I asked the question “What is the compelling reason to give another year of my life at work?” The pension fund was still in good shape, and at that time I finished Richard Heinberg’s book “The Party’s Over” (a scary book relating energy to human population growth – what goes up…). It was time for a change, so I took early retirement after turning down a pay rise and promotion to stay on for another year. I decided to undertake a new challenge to reduce the carbon emissions and energy footprint of our house as close to zero as possible, and document the whole experience (which is still ongoing). Additionally, I joined the village Greening Campaign and Winchester Action on Climate Change. Hopefully, we have succeeded in significantly reducing our CO2 footprint and energy consumption of the house – the journey continues!
Our goal was to reduce our CO2 and Energy consumption by 80% and our motivation comes from the following:
The Kyoto agreement is to reduce emissions by 80% in 2050.
Heating accounts for 47% of the UK’s CO2 emissions and 60% of average domestic energy bills
The Heat and Energy Saving Strategy consultation document proposed the following goals :-
2015 – all lofts and cavity walls insulated
2020 – seven million homes to take up a “whole house” package going beyond simple insulation.
2030 – all buildings to have received such a package
I purchased this 1979 modern 4 bed house in 1984.
• Loft Extension 1989.
• Refurbished kitchen 2000.
• Refurbished toilets and bathrooms + condensing boiler 2006.
• Ground floor extension 2009.
• New drive with rain water harvesting tank 2013.
• Kitchen upgraded to include under floor insulation 2013.
Heating is provided by wood burning stove and is sufficient to fully heat the whole house.
Only requires 1 delivery of wood per year (£150).
Central heating was on for 1 day in 2012/13 winter.
Low energy costs (surplus income when taking into account feed in tariff.)
Approx 5% ROI index link.
Carbon footprint significantly reduce (80%+) and even lower with renewable energy supplier (all energy produced is at 0g per kWhr).
Wood burning stove.
Extension that opens onto the back garden.
Rob’s Building & Environmental Consultant, Ken Neal, answers this question thus.
Interstitial condensation occurs where the dew point falls within the construction thickness. This will almost always be the case in cold weather. Where this occurs and in what material is where the problem can lie. With a badly insulated structure the dew point will form close to or at the inside face of the construction causing damp and this then causes harmful mould growth. With a well insulated structure the dew point is well into the construction depth and so there is less of a problem with dampness and mould growth at the inner surface.
This can cause a different problem, though. If the outer surface is a soft porous material such as old brick and the weather is freezing the interstitial condensation occurring in the outer layer of brick can freeze and spall off the face of the brick. This can happen with cavity insulated structures or with internally insulated structures.
With the external insulation system that I specified for Rob’s improvements the dew point falls well within the outer layer of insulation. Because of the make up of the insulation material the moisture vapour cannot move through the insulation to the dew point so it stays warm and in the form of vapour. Where the vapour moves through the joints between the boards there can be condensation but it is harmless and drains away eventually. Any other excess vapour is removed from the house by the ventilation system accompanied by the low level of heating required by the highly insulated structure.
Internal insulation systems commonly used in older and listed properties have to be very carefully specified and detailed to prevent the occurrence of cold bridging and moisture movement through the insulation. This is to prevent the build up of moisture in the outer layers of the construction and possible freezing damage. These insulation systems, while being possible to construct on a DIY basis, need to be properly designed and detailed by an “experienced” professional to avoid the many pitfalls that can occur in a badly designed and detailed job. A DIYer has as much experience as many builders in this type of construction and are more likely to follow the plans and get it right than many builders who will do it the way that they have always done it and get it horrendously wrong. There needs to be a huge educational push in the building industry to show most builders how to work with modern insulation materials.
I have not read the ‘Breaking the Mould’ report and if it cautions against U-values of less than 0.5 I am not going to bother. U-values of around 0.1 are commonly used on the continent and occasionally used here, as was the case with Rob’s house, without any problems. Where problems can arise are when systems are not properly designed, detailed and built. That is not a problem with high levels of insulation but with bad building. We need to address bad building not the required high levels of insulation.
A house with a best insulation value of 0.5 is more likely to suffer damp problems than one with a better U value because the cost of heating such a structure will mean that it is often colder than it should be, inviting surface condensation and mould growth. It will often be kept more airtight to avoid cold draughts and hence build up a higher level of water vapour within the structure. Such a property would commonly have double glazed windows which will prevent condensation on the glass. This will, however, throw more water vapour onto the cooler walls exacerbating the mould problems.