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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthordanpipe
    • CommentTimeMar 17th 2014
    Hi all, we are planning a major refurbishment & extension to our house, and we're keen to add renewables to it. The house is south facing (almost exactly) in the south of England, and the finished build will have a main roof with an area of approximately 40m2, and a side exension (stepped back) with a 10m2 roof. Both roofs at a 35 degree angle.

    What are your thoughts on how best to use this roof space? Our original plan was to put solar PV on the main roof - covering as big an area as possible - and put a solar thermal panel on the side extension roof, coupled with a megaflo system and thermostatic showers to make best use of the hot water.

    It's been suggested that it's better to use solar PV for hot water, as there's less wasted potential solar energy in the summer, so now I'm considering putting solar PV on both roofs. Whatever system we end up with, we want it to run itself with minimal tinkering - e.g. no manual switching on of immersion heaters - so the system would need to heat up the water with automatic backup from the gas boiler to provide sufficient hot water for morning showers.
    • CommentAuthorEd Davies
    • CommentTimeMar 17th 2014
    I'd agree with just using PV. There are arguments for using solar thermal for space heating applications but for DHW PV is probably better overall - it's somewhat cheaper per watt produced in poor conditions (when the sun's not bright but the water is hot), it avoids problems with heat dumps and can be used as electricity one the tank's hot as well.

    Before talking about details it's probably best to have in mind the expected use of the house. Will it be occupied during the day time much?
    • CommentAuthordanpipe
    • CommentTimeMar 17th 2014
    It'll typically be occupied during the day for 3-4 days a week (though that could come down to just weekends as my working arrangement varies). For heating we're planning wet underfloor downstairs, electric mats in the bathroom and ensuite, and rads upstairs. I hadn't planned on using solar for the heating (except the electric mats) - just for the hot water. Is that the best approach? Not sure how to integrate solar PV into heating, or if solar thermal is well suited to it.

    I estimate that the main roof can comfortably fit a 4kW system, so adding PV to the side roof would take it over 4kW - are there any complications with having a large PV array feeding in to the grid? I've heard it mentioned that permission may be required over a certain power output.

    I've also searched around and discovered products such as Apollo GEM which are designed for making best use of renewable electricity for heating water, which is ideal and leans the arguments in favour of PV of solar thermal.
    • CommentAuthorEd Davies
    • CommentTimeMar 17th 2014
    You might want to check out the new thermal solar/biomass CHP systems coming on the market it uses the same thermal oil technology as my commercial system but on a domestic scale.

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