I always have this problem at 95 per cent. The light at the end of the proverbial tunnel drains my energy and I cast about in the gloom for an escalator to take me up the final 5 per cent, only to find the staircase getting even steeper. If ever I needed to improve my personal energy efficiency, it's now.
As this is national Energy Saving Week, it's a good moment for all of us to put some extra personal energy into realising our domestic energy-saving ambitions. Seize the day and change those light bulbs! You can check out the Energy Saving Trust's top 10 tips at www.saveyour20percent.co.uk for more ideas.
Ultra-efficient Tree House is designed to use so little energy that we will be able to generate all we need on-site. But beyond our immediate needs for heat, light and power, there are many indirect ways in which we can still guzzle energy.
Under our beautiful super-insulated roof, currently being completed by millimetre-accurate Nick, we will also be saving indirect energy wherever we can.
For starters, lots of energy is consumed purifying and pumping mains water, so we are keeping our demand low by installing taps and showers with aerators that provide a fuller flow for less water (www.hansgrohe.co.uk), ultra-low-flush Ifö ES4 toilets (www.greenbuildingstore.co.uk), water-efficient appliances, and an underground rainwater tank to supply our garden and pond.
Building materials also come with substantial "embodied energy" - the energy expended in extraction, manufacturing and transport. Consequently, although our foundations are full of carbon-intensive concrete, above ground we have prioritised natural, unfired materials such as wood and English stone ( www.kirkstone.com).
Whenever you buy new stuff of any kind, these hidden costs clock up. To avoid them altogether, buy second-hand.
We're using a wide range of reclaimed materials in the build; all our furniture is being sourced through second-hand shops and eBay; there's a great second-hand bookshop in Brixton (Bookmongers); and I often buy good-quality clothes from TRAID (Textile Recycling for Aid).
Even more problematic is the national and international transport of food, given the volume we all consume. We plan to keep our food miles down in Tree House by tending our allotment, growing herbs in the back garden, boycotting supermarkets' centralised distribution networks, and buying local produce whenever possible.
Finally, waste is a waste of energy because whenever you send something to landfill you are also throwing away all the energy that went into making it.
We will be recycling almost everything via compost heaps in our front garden and multiple recycle bins in our kitchen. We also plan to reduce our packaging waste by combining bulk-buying with a glamorous display of large storage jars (www.bodum.co.uk).
Is that enough energy saved to get me through the last 5 per cent? One last burst of solar-powered enthusiasm and I'll be sitting back, admiring the view and wondering what I can possibly build next.
Will Anderson's complete 'Diary Of An Eco-Builder' will be published by Green Books in spring 2006; www.treehouseclapham.org.uk.Reuse content