Saturday 23 February 2013: Thimble of Thought
Today's blip is a thimble. It's sometimes a useful device when you are sewing. It's also used metaphorically when describing small things, a thimble full of drink for example.
This week someone in the village was asking about installing PV panels on their south facing roof. The government will only allow the full feed in tariff if you have already fully insulated your house - it is obviously pointless generating electricity if your house leaks heat like a sieve.
I checked the EPC chart for our house that came with the HIP when we bought the house. It's quite pathetic, it reports loft insulation of 250 mm when in fact there was only 100 mm when we moved in. It does note the old boiler with primitive controller and lack of efficient light bulbs. It then gives some bland advice and ranks the house at grade "E" with a SAP score of 48. The best the house could be is apparently grade "D" with a SAP score of 55. That corresponds to a energy use of 314 wKh/m2 falling to 275 kWh/m2.
This is all rubbish. We changed all the old bulbs to mostly CFL, plus some LED and some halogen the day we moved in. Last autumn we put in a modern boiler and controller and started to insulated under the floors. We added 200 mm of loft insulation taking it up to a minimum of 300 mm over the whole loft with the spare in the centre to 400 mm. We have yet to replace the windows and doors, and complete the under-floor insulation.
For the first full year we were in the house we used 115.25 kWh/m2 (a cold year too), which is better than half the potential minimum energy use and last year we used only 85.44 kWh/m2 (mild year plus new boiler for 2 cold months).
What scares me is that these figures are so far from reality that I do wonder if the people who prepared them have a thimble of brain?