green diary

Ideas to reduce electricty consumption at home

Just some quick thoughts on how to reduce electricity consumption at home. These figures are very rough-and-ready (but do come from 9 day's of monitoring with IAMs... but usage was a little unusual over the Christmas period):

  • 10 x 12V 50W halogen kitchen down-lights on TRIAC dimmer (currently 1kWh/day = £50/yr). These are the biggest single power draw in our house. I'm currently researching LED or CFL alternatives.
  • Central heating and hot water pumps (combined currently 0.6 kWh/day = £27 / year). Replace with energy efficient pumps (these cost about £100 IRC, so payback for 2 pumps would be ~9 years).
  • washing machine (currently 0.5 kWh/day = £22/yr) fit hot water feed with mixer. Heating water with a local gas boiler is more carbon efficient than using resistive heating.
  • dishwasher (currently 0.6kWh/day = £27 / year) fit hot water feed and disable hot air dryer somehow?
  • 34" CRT TV (currently 0.5 kWh/day = £22 / year) upgrade to LED LCD TV (32" LCD TVs use about 40W) (notes)
  • Dual-core Athlon HTPC circa 2006 (currently 0.6kWh/day = £27/year). Upgrade to 22nm Atom when it's available.

Raw consumption data from 9 days of usage after the break...

Insulating our bedrooms


Back in February, we insulated the two bedrooms in our end-of-terrace Victorian solid-walled house. This blog post attempts to document the process, including lots of photos. The detailed plans for this project (including some CO2 calculations and a complete shopping list) are described in a previous blog post. A quick re-cap of the plans:

  • Our upstairs walls are not damp so we can just attach the insulation directly to the plastered wall, we didn't bother with wooden battens.
  • Use Fermacell instead of plasterboard. Fermacell is much stronger than plasterboard, so it should be possible to hang shelves directly from the Fermacell.
  • 65mm insulation + 12.5mm Fermacell
  • Use 160mm "frame-fixing" screws to mechanically secure the Fermacell to the brick. These come with their own wall plugs. To use, just drill straight through the Fermacell + insulation + brick, then hammer the wall plugs into place and screw in the long screws (i.e. you don't need to pre-drill the wall and then try to align holes in the insulation with holes in the wall).

In total it took about three weekends to install the insulation for both our bedrooms, MUCH less time than it took to insulate our living room. (This time does not include the time taken to plaster and decorate, which we had done by some excellent local decorators - I just installed the insulation & Fermacell.)

On to the details...

Summary of "green" features we've added to our house

Our house is a solid-walled house built around 1905.  Being end-of-terrace, it used to be very cold in winter.  We've gradually insulated over the past three years.  In terms of thermal performance, the house should now perform roughly on a par with a new build.  The majority of the work has been insulating the walls.  I did the bedrooms, living room and dining room and we used builders to do the bathroom.  In total, the energy-saving measures now installed include:

  • 65-80mm of rigid-foam insulation on all external walls (mostly DIY; some done by builders during other work)
  • at least 270mm of glass-wool insulation in the loft (DIY)
  • insulated the suspended timber floors in the living room and dining room (DIY)
  • we worked with a local sash window maker to put high performance double glazing units into wooden frames for the front of the house
  • lots of draught proofing and a focus on airtightness during the DIY refurbishment
  • mechanical ventilation with heat recovery in the bathroom (it works very well)
  • fitted wet underfloor heating in the living room (DIY).  UFH is wonderful!
  • solar thermal (evacuated tube) fitted professionally (would have done it DIY if it weren't for the new regs)
  • light pipes to bring natural light into the kitchen and corridor (installed by builders)
  • home-made 450 litre rain water tank in back garden, with piping running under living room floor to bring rain water to front garden
  • thermostatic radiator valves on all radiators; new condensing boiler with walk-about thermostat (which is great)... plan to install room-by-room digital radiator controls

Overall it has been a lot of work and at times it's felt overwhelming.  But we're pretty much finished with the insulation and there's absolutely no question that the house is considerably easier to heat and more comfortable than it was.

Gas consumption 2007-2011

I've finally gotten round to plotting our gas consumption on a graph. I'm not expecting a measurable drop in our consumption yet. We finished insulating our living room in July 2011 and I'm only just getting round to insulating our bedrooms (Feb 2012). We installed a new condensing gas boiler and solar thermal in July 2011. But we also had a baby in August 2011 so we've had the heating on far more than normal for the last quarter of 2011!

Temperature data from the Heathrow MetOffice weather station

What does this data tell us? And why did it take a fair amount of effort to plot our gas consumption?

Dimmable LED down lights

Our kitchen is currently lit with 10 × 50 watt tungsten lamps. Yes: that's a total of 500 watts. Which is utterly obscene and I feel distinctly uncomfortable just thinking about it. We want to replace these tungstens with LEDs, hence reducing the power required to light the kitchen by a factor of 10 or so. We have several requirements:

  • Must be dimmable down to 5% or 1% (some LEDs only dim to 60%)
  • Must produce enough light to fill the kitchen
  • Must produce a warm, cosy light
  • Must produce a light with a high enough colour rendering index to mean that skin looks like skin and not like pale plastic

This post is basically a collection of notes recording my research into dimmable LEDs.

Planning to insulate bedrooms this weekend

This weekend my wife and 5-month old daughter are going up North so I'm going to take the opportunity to insulate our two bedrooms. In this post I describe in detail my plans for insulating the walls of our bedrooms and also attempt to calculate how much carbon and cash the insulation will save us.

Existing central heating control systems

A little while ago I wrote some notes describing my "ideal" central heating control system, which I was planning to build myself.  Time is short so it looks like this system won't be built for a while so I need something which I can buy off-the-shelf which will satisfy as many of my requirements as possible and also leave the door open to DIY tinkering in the future.  This blog post is a collection of notes about off-the-shelf central heating control systems.

Insulating our Victorian living room part 2

We live in an end-of-terrace Victorian house, built around 1905.  I've spent the last few years insulating our living room.  This blog post is the second in a two-part story.  By the end of the first part of the story, our living room looked like this:

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I'm pleased to say that our living room now looks like this:

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One big design change since my last blog is that we decided to install wet underfloor heating ourselves.

So, let's start the story...

Solar-powered rainwater pump

I plan to build (or buy) a solar-powered pump to take water from our main rainwater tank uphill to the top of the garden.  This second tank would then be able to gravity-feed a hose pipe for watering the garden, instead of having to use watering cans (I'm lazy).

Links for solar-powered rainwater pumps:

Solar Thermal notes

Notes whilst gearing up to install a solar thermal system in Summer 2011:

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