Introduction

Home Energy: Is 'Going Green' a Good Investment & Worth the Effort?

 

We have lived in an English 1970's 4 bed detached house for over 25 years. We have made a few improvements to energy efficiency, but more with a view to making the house more comfortable to live in...

...roll on 2021 and 2022 and energy prices take off. It seemed like a good time to take stock:

 

Which investments are worthwhile and which ones are not worth doing?

 

This question actually turned out to be much harder to answer than I had expected - various websites had useful indicators but mostly lacking hard data that I could apply. Hence this blog where I plan to show the impact of various 'green'/money saving measures in a real house lived in by real people.

 

Here was my 'audit' as of Autumn 2021. We have:

• uPVC double glazing
• Cavity wall insulation
• About 100mm of insulation in the attic
• Condensing system boiler (ie with hot water tank) running at about 75degC flow temperature (more on flow temperature in a future post - in 2021 I didn't know what flow temperature was!)
• Smart temperature controls fitted (more in a future post)
• Most occupied rooms set at 20degC during the day and off at night
• Log effect open gas fire (it looks nice, but is not the most efficient)
• LED bulbs through the house

 

What we could do:

• More insulation in the attic (eg 300mm seems the norm now)
• Insulate central heating pipes in the garage
• Heat pump to replace boiler
• Reduce flow temperature to 65degC
• Reduce central heating set point to 19degC
• Add solar panels

 

There are various websites that help you work out the return on investment:

 

https://energysavingtrust.org.uk/energy-at-home/reducing-home-heat-loss/

https://www.snugg.com/

 

 

but it seems too many variables to really get a good grasp of the return that you might get in real life (eg no one covered my uninsulated pipes in the garage - perhaps just too obvious!). One aspect that I could not find good coverage for is the effect of life style patterns. As of 2021 my wife was retired and I was working in an office. How would this change when I retired?

 

I did my best to gather up some historic data on our energy usage:

 

 Fig 1.1: Energy usage over subsequent 12 months and key events

Graph Notes:

• Each column shows the cost 12 months energy usage normalised to  Aug 2023 rates (including standing charge)
• Data capture was inconsistent - rarely an exact 12 month period - here I have normalised to 365days (this will introduce a small error depending on if the discrepancy/adjustment is summer or winter - worst case was 26days)
• The 2009 bar is a 7 year average to 2016; otherwise I have made no attempt to average out 1off factors like weather or a winter holiday.
• House size: 186m2, on two floors with integral single garage (see https://calculator.bcis.co.uk/measuring_your_house/measuring.aspx on how this was calculated)

What does the history tell us?

• Not much change in  the  period  2010 to 2017 (last remaining child still at home)
• 2017 to 2019 empty nesters, both out at work ~5days per week.
• Condensing boiler looks to make ~15% drop in energy use (but the installation also added to the uninsulated hot water pipes in the garage)
• While there was a slight nudge up in usage when my wife retired, it really went up when I was working at home in the pandemic!
• Smart heating controls made no obvious immediate impact (they did make the house more comfortable and perhaps enabled later savings - see future post)
• My return to the office and insulating the central heating pipes in the garage look to have had an impact

 

The obvious things to try:

• Reducing flow temperature to 65degC - just turn the knob on the boiler (see future 'Weather Compensation post I have planned)
• Turning the room temperature down by 1degC - let's give it a go and see how we get on; will it be too cold?
• Insulating the attic sounds like a good ROI (eg https://energysavingtrust.org.uk/advice/roof-and-loft-insulation/ shows £1200 cost  & £475/year saving, but that is going from 0mm to 270mm, we already have an average of about 100mm).  There are also lots of pictures of it being just 'rolled out' - reality is different (see planned future post on insulating our attic - real life!)

 

Watch this space - I plan to write future entries on real life installation and the effect on a real house with real people living in it. Eg, what will happen with my retirement? (other than I have time to write a blog on heating a house)

 

My hope is that this adds to the somewhat abstract information that is widely available online.