Day job: designing solar thermal for retrofit in occupied properties. One morning installation and economic vs gas without subsidy are are the targets, but more on that as we're closer to a finished concept.

Sounds interesting!

It's tricky, that's for sure. Detail as to what/how when we're closer to the finished solution. (and I've checked what it's ok to say on the GBF with regards advertising etc)


Garage is more an experiment in me learning how to build/supervise trades rather than pushing the technology.

Passive slab, timber framing or possibly timber/steel framing, EWI and render/cladding/brick slips, and a2a heat pump/airconditioner units. A little home automation/keyless entry too. (http://www.indiegogo.com/projects/the-xnt-implantable-nfc-chip)

Try it all out on the garage; use what works in a 2/3 storey extension to the house including roof replacement and EWI on the remaining walls.

It won't be passive as the site is all wrong (heavily shaded thanks to flats next door for starters) but I'd expect AEBC Silver or CSH3/4 equivalence.

The interest in the a2a heat pumps is partly down to usage. I have 3 lodgers at the minute and would be looking to have 6 (!) after the extension work to earn a crust from the place. Don't mind living in a tech hippie commune whilst each room brings in £500/month. Some are like me and happy with 17C/too hot over 21C, whereas others are cold at anything less than 25C. (tip: avoid letting a room to skinny foreign girls that have never paid a utility bill in their lives) Occupancy patterns are all over the show; mixture of recent grades, grad students, postdocs etc.

http://www.saturnsales.co.uk/Mitsubishi-High-Efficiency-SRKZJX-S-Wall-Air-Conditioning-Heat-Pump.html?category_id=1

I was going to stick an a2a unit in each study bedroom; hotel style. Electricity meter on each one for no arguments over billing, and hooked up to a DIY home automation system for occupancy sensing/remote control etc. Ultimate in zoning. Yes "grossly oversized" but that means you can ramp temperatures quickly and IME that's as important for perceived warmth as actual temperature.

No bloody gas safety certificates or gas standing charges either, so provided that the seasonal average COP is >2 (my current gas bill £400 incl £75 standing charge on a G-rated non-condensing boiler; certificate £100) it'll be cheaper to run than gas. Plus A/C if required. (with lots of people in a house all sharing communal cooking etc the heat load is significant) Plus huge redundancy. Until the electricity goes off, but they that'll kill any modern gas boiler anyway so no harm there. The inverter driven units will probably run off 180V DC ok (everything else in the house does, except tumble dryer, cooker, hairdryer, and vacuum cleaner) so you just hook up to the car at that point. (Gen1 Honda Insight; good for 10 kW @ 180V DC @ 3k rpm - I'm amazed that the site power people haven't started converting hybrids as self-propelled secure gensets yet!)

Could be tempted by a "mini split" system etc but these would require more expertise than nailing a box either side of a wall. Tricky to find that from UK tradesmen outside the commercial sector.

The interest in wood/EWI is obvious; the steel would be to get around planning restrictions on height and footprint/plot area. Maximise headroom for a given clear span as compared with timber framing and minimise internal structural shear walls.