Happily the modelled savings show a 77.6% reductions.

This is slightly differently from what I estimated – 83%.  Looking at the results in a bit more detail shows that the main variances are in the lights and appliance and hot water use.  Our modelling using the Home Energy Masterplan has lower figures in the initial case based on our proposed use for these. The software used for the Superhomes applies standard use.

The Superhomes process also estimates that for our ‘after’ position, 50% of our CO2 emissions or 2.4 tonnes a year will be due to electrical lights and appliances.  This around to around 4400kWh a year (before PV contributions taken into account).  We’re hoping to be around 2,400kWh based on our actual use.

Finally, the PV contribution is a little conservative at -0.95 tonnes, when we actually achieved just over -1.1 tonnes.

To be honest that’s all a little nit picking and as the Superhome software is actually designed to exclude how we are actually going to use the house, i.e. its for benchmarking, it definitely  isn’t a criticism of the software.

Remember my rough estimate of the additional eco elements of our renovation (i.e. taking out those bits that would be needed in a normal renovation) came in around £22,500. I think 77 to 83% CO2 reduction for that is something to be pretty proud of.  Perhaps I’ll enter us for some awards in 2013…

Of course we could have gone further and aimed for 90% (and may not have got it) , tried to achieve Passivhaus Standard in a retrofit or similar and spent an additional £XX,XXX in the process.  We didn’t want to do that though because:
a) Why spend £100,000 to get 85% when you can spend £25,000 to get 80% reduction
b) The embodied energy of the additional kit to get that little bit more might not justify the potential extra 5%
c) We wanted to demonstrate something that is achievable by most people as they do up a house

So how should most people go about it?  We’d recommend you start with a Home Energy Masterplan.