Can’t remember when I last did a shower blog which focussed on numbers (Well I can’t remember when you didn’t. But I know what you mean cos I lost the will to live halfway through this one. Ed). Yeah, yeah whatever boss. Anyway, where was I? Ah yes. This blog was going to be a musing on why we find it so hard to give up things like showers and smoking (or even showering while smoking). But then I did a back of a fag packet calculation (how apt) for a recent conference I was talking at and I realised the numbers need addressing right now. And where better to do that than in ‘the best showering blog in the world’?

Outside of the world of showers (yes there is such a world into which I venture occasionally), there is a concerted campaign to retrofit existing properties to a standard that will provide good thermal comfort, whilst at the same time addressing fuel poverty and meeting the UK Government target of reducing CO2 emissions. Whilst a lot of this is being done without any hard figures at which to aim (you could blame the BRE and SAP for that and you would be broadly correct), there are two standards that do look at the numbers. They are known as EnerPHit and the AECB Silver Standard, and they both use a piece of software called PHPP to design new buildings or to retrofit existing ones, and calculate the energy use of those same buildings. To meet the EnerPHit standard a dwelling must be designed to use less than 25kWh/m2 a year for space heating; to meet the AECB Silver Standard the figure is less than 40kWh/m2.

This is not easy, dear reader, to keep your attention whilst at the same time dragging you into a totally different world. But fear not. The word shower is just about to reappear! And here it comes… 2,989kWh of energy is required a year to heat the water of our standard adolescent showerer. I have gone here for an adolescent who spends 30 minutes in a shower, once a day, with a flow rate of 7 litres/minute, (though we could divide that up into two showers a day of 15 minutes each, if we so wished). Of course we know that not all adolescents take that long, but we also know that there are plenty who do. (See last month’s blog for some examples). In a survey of 160 pupils at an inner London secondary school that ech2o carried out recently, the average shower was 23 minutes, once a day, with 32% of all those responding spending 30 minutes or longer in the shower.

So, dragging ourselves reluctantly away from showers again, a 100m2 home (think three bed semi) will use 2,500kWh (EnerPHit) or 4,000kWh (AECB Silver Standard) a year to keep the occupants warm and toasty at 21OC. So our one adolescent requires more energy and is producing more CO2 emissions than the space heating in a deep retrofit.

What also happens out in that world is something called Post Occupancy Evaluation (or POE). A lot of money is poured into such research and yet time and time again hot water use is not monitored separately nor the occupants asked about their showering, bathing and dishwashing habits, all of which are heated by the boiler and so will impact on the overall gas consumption of the dwelling. If POE studies do not take into account the current (I live in hope…) real life habits of the UK’s adolescents, and calculate their hot water use based on a 5 minute shower, then no wonder the numbers are flawed.

Back to pictures of unfeasibly cute polar bears next column!

April 2015 – Back to the numbers…