Sunday, 1 July 2012

Blowing Hot Air


I’ve had chance this week to assess what the energy use is like in our house. I took the meter readings that I have been collecting each month and plotted the daily use of both electricity and gas over the year. I used 26th June as the starting point because this was when I insulated the loft last year. The graph below shows the daily use in KWH of  gas (in blue) and electricity (in red) throughout the year: 
 Overall, my reaction to the figures was HOW MUCH?!? The worrying thing is that this was after I had made some attempt to improve the insulation and over the year I have made various changes to reduce the overall energy use and/or cost. Some of this was intentional, such as swapping out incandescent and halogen light bulbs for  low energy equivalents. Some has been incidental such as swapping an electric shower for one that runs off the gas heated hot water supply or replacing our broken down CRT television with an energy efficient LED one. In fact looking at the cost is quite a useful analysis both in financial and environmental terms as the price of electricity is a reasonable proxy for its CO2 emmissions compared to gas:

 Now the interesting thing here is that my effort to reduce the amount electricity we use has been quite successful. I suspect that the largest factors are to do with washing and drying: Our tumble drier was “C” rated when it was bought (actually reasonably efficient at the time) but the lousy weather we have been enduring this year has meant it has been used more than we would like. However, the one massive factor is that the energy use is seasonal and the vast majority of usage is simply keeping the house warm. In fact it is so high that if the use in Winter was sustained throughout the year it would place us within the government’s definition of “fuel poverty”.

The question is, what can we do to reduce the energy use? I’ve insulated the loft so that has gone as far as is possible but it was quite interesting to see how the rest of the house held up during the coldest months. The house has essentially three sections. The extension at the back was built 20 years ago and so is built to reasonably modern standards. The only area of improvement I could see here is to replace the patio window (which has a metal frame) with something more insulating: this is a relatively high cost item for only a small benefit. Interestingly, the old stone built Victorian section was relatively cosy throughout the Winter months. This was the section where I installed the loft insulation so I expect it helped. The only place I noticed that was very cold was the marble fireplace which was cool to touch and covered in condensation when it was frozen outside. By far the worst bit in terms of heating is the 1920s extension in the middle. This is built out of solid brick with quite a high ceiling and, I would expect, little or no insulation. The heat in the back bedroom in this section appears to rapidly drain from this room and both the ceiling and window jambs were cold to touch. This is the next area I am planning on tackling. The idea is to insert foam behind the jambs and to install a false floating ceiling with insulation above it.

In terms of cost reductions it will take a very long time to recover the cost of extra insulation but I would take any saving as a bonus to what I would actually want to achieve: a warm house. Our old house was smaller but the heating requirement was about half of what we have now. It was also a 19th Century stone building but in that case the conversion was effectively a modern house built within the walls of an old farm building. Whilst it would be difficult to make an older house emulate the insulation properties of a modern construction it should still be possible to vastly improve the heat retention of our house. Hopefully we can make some improvements before the weather really takes a turn for the worse.

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