Sunday, January 14, 2007

Green Home Improvement - Energy

It's been a revolutionary eco-living week chez Kane this week (hence the lack of posts). We've had a new condensing boiler put in along with a solar hot water panel on the roof. The condensing boiler is about 97% efficient compared with the 80% efficiency of the knackered old 80's combi we found when we moved in, which will save a lot of gas and carbon dioxide in itself.

To comply with building regulations, we had to have thermostatic valves installed on most of our radiators. These use a gas filled piston to open and close the radiator valve depending on the room temperature. We've found this has really helped level out the heat in the house and cut draughts.

Most solar hot water systems use a twin coil hot water tank which is heated by a conventional boiler and the solar panel in parallel using a coil each.

We didn't have space for this type of tank and wanted to keep 'hot water on demand', so we went for the alpha boiler system. This has its own tank heated by the panel (the picture shows it without its polystyrene cover). If the water in the tank is above 60°C the water feeds the taps directly. If it is below 60°C, it feeds into the boiler for a top up - using a lot less gas. This arrangement means we never heat water with gas that we don't use as we would inevitably do with a hot water tank system.

The standard rule of thumb is that a well-positioned panel will provide 70% of the hot water for an average household. Frankly our panel is not well positioned as we're in a valley so we don't get much sun in the winter and our chimney shades the panel from the south west. So at the minute it's not doing an awful lot - raising the water temperature by about 3-5°C, but in couple of weeks it will be getting direct sunlight and we'll be able to see what it can do. This seasonality will lengthen the payback and reduce the carbon savings, but we put it in as much for the statement as anything else.

Sadly, we've been wandering about for the last couple of days getting envious of houses with unshaded south facing roofs bathed in lovely winter sun...

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