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Saturday, 12 July 2008

U-values, plans and spreadsheets

Posting on this blog, while not temporarily suspended, per se, is taking longer than normal. This is entirely the fault of the house which we've recently purchased. I'm longing to provide details of the Burgeoning Gatorade Trailer Disaster at Work, as well as inside information into corporate law and the results of our successful lawsuit, as well as tale of very flat hiking in the north of England, but for the next week our output will be limited.

The reason for this is that , until I actually achieve, once again, a state of worklessness, a state which is imminent (Thursday 17th July), I go to work, come home and work on the house - even if not physically we calculating U-values like crazy, researching environmentally friendly products, discussing design details or walking the cats. Tonight for example, after a ten hour shift tearing down walls and filling plaster, the Red Haired Boffin is in one room drafting amended plans for our Planning Application, while I'm researching the price of materials for our kitchen extension so we have a baseline materials cost which we can use to assess the quotes we are obtaining from builders.

Most of this renovation is by us, and our plans are the most ambitious we've ever attempted. We are only going to get builders to do a very small proportion of the work we've planned, and the actually task before us is massive. It includes:

Designing the extension to the house (including structural designs)
Designing a new heating system which incorporates solar, gas, underfloor heating and baseboard radiators.
Designing a new type of lighting system based entirely on LED lighting
Designing an insulation system that improves current English Building r3egulations standards by a massive 1000%

Then designing and making a kitchen, two bathroom suites, three window skylights and installing a bamboo floor.

At the moment we are busy tearing out all the ceilings and exterior wall finishes, right back to bare brick (in the UK, walls are usually brick smothered in at least an inch of rock hard plaster). We're also ripping out the whole ground floor subfloor, insulating beneath the floor to about 150mm of high density insulation, laying an underfloor heating system, re-laying a new subfloor, then laying a bamboo floor on top.

All of this means we're right into the math. We have to work out the final heat efficiency of out house after we've insulated (this is called the u-value, and is based on the heat transmissions of the walls, ceiling and floor), then work out how much radiant heat we need to heat a cubic volume displaying this level of thermal efficiency, then convert that figure into an equivalent output figure(given an anticipated output of the underfloor heating, radiators), work out how many radiators we need, convert that figure into another related figure which is called BTU (British THermal Units), a figure that describes the power output of our planned solar panels and back up gas heater, then search the market for products that fulfil our criteria.

Last night I did all of these calculations then found that I could not find a gas boiler which was weak enough for our needs, because if we insulate as planned, the thermal efficiency of the house would mean that in winter we would be returning hot water to the boiler(gas powered water heater), which is very bad for the boiler. The dilemma was therefore to reduce our insulation ie make the house less thermally efficient, or to increase the number of radiators. An increase in the number of radiaters, while cat friendly is very disadvantageous in terms of our budget - it means more materials, more plumbing, more thermostats. So today is back to the drawing board.

Maths becomes complicated when one starts discussing cubic flow rates per minute - the number of variables are truly astonishing. But the trip is worth it. I have found a few other hardy souls who have attempted to do what we are attempting, namely an inner city off the grid eco-house- but in truth, most of our contemporaries are people we would probably avoid socially - mid thirties hippies, with not an eye for asthetics, strong body odours and straggly pony tails. We, I've concluded are eco-chic. It's environmentalism with high heels. But like the eye-brow plucker, beauty - especially self-build post hippy enviro-realism (as I do'nt, but would, call it if I was in marketing) - comes at a price. You've got to work at it baby.

Therefore tales of our other lives will have to wait a week or so. IN the meantime, our planning spreadsheet is at the top of the page. It is colour coded. Red meads something needs doing. Green means it has been done. Yellow is an information box. Please feel free to dip in. Regular progress reports will follow, but not at the expense of commenting on our other lives. Just as soon as I've worked out these flow through figures for 25mm copper pipe.

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