Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)


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.

Buy individually or both books together. Delivery is free!

powered by Surfing Waves

Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

    • CommentAuthormoonmirror
    • CommentTimeApr 21st 2007 edited
    I have been trawling the internet for hours looking for a breakdown of components required for underfloor heating and GSHP
    We are going to start a gound floor house extension in about 5 weeks and would like some green underfloor heating
    60 sq meters solid floor

    The idea sounds so simple and GREEN, if i cant come up with some thing i will have to run some more rads from our existing gas boiler.

    Any tips or help would be much appreciated

    Hi. I can only guess you've spent those hours looking in the wrong places! I 'Googlrd' for half a minute and came up with these 2:



    I do not recommend or have any connection with them. I simply know that they are 2 firms doing 'standard' UFH systems and components. REHAU also seem to do courses. We've got a Thermia 6kW GSHP at South Yorkshire Energy Centre (www.syec.co.uk). By all means ask Q's.

    I hope this is useful.

    P.S: It's only really Green if you use Green elec.
    • CommentAuthormoonmirror
    • CommentTimeApr 22nd 2007 edited
    Thanks Nick, sorry i was assuming you needed a special type of under floor heating for a GSHP.
    You have just given me an idea though, i have got a boat at the bottom of the garden.

    Would this be any good, i found them on ebay

    I am trying to get a price breakdown
    You won't be saving any emissions by using a GSHP rather than a gas boiler. The COP on the heat pump just offsets the inefficiencies of the power stations generating your electricity. Think of the alternative uses you could put the cash towards e.g. a more fuel efficient vehicle, holidays by train rather than plane, local produce rather than supermarket, buying a bike etc. Also, consider the embodied energy in the manufacture of an unnecessary heating appliance.

    I should think you could run the underfloor off your gas boiler or else put the rads in.
    Moonmirror wrote: "Would this be any good, i found them on ebay

    For what? For a boat's batteries, yes. For much more, no. Also depends v much where the boat is...
    • CommentAuthormoonmirror
    • CommentTimeApr 22nd 2007
    Just thinking it would be easy to have a wind turbine mounted on my boat and run a cable 100 yards to where the GSHP will be.
    • CommentAuthorGuest
    • CommentTimeApr 23rd 2007
    "You won't be saving any emissions by using a GSHP rather than a gas boiler. The COP on the heat pump just offsets the inefficiencies of the power stations generating your electricity".

    I had thought GSHP would be saving on emssions. I got a quote a few months ago. It was a high cost but reduced energy bills by 50%. (currently using oil fueled boiler with relatively new boiler). Of course cost does not translate to the same thing as emissions but one would assume using part renewable source that emissions would be lower dispite the great use of electricity to run the pump.

    You'd need a hell of a lot more than a 400w turbine could deliver. Have you looked at www.bwea.co/noabl for an indication of your local w/speed?
    • CommentAuthorGuest
    • CommentTimeApr 23rd 2007
    Even if you have a turbine which will supply the steady-state power a GSHP needs to run (2-4kw depending on the capacity) you'll have a heck of a hard time finding a turbine which will supply the starting current which may be as high as 100A or more (the LRA "locked rotor amps" of the compressor). Same thing with a PV array connected to an inverter.

    Paul in Montreal.
    Alex, it all depends on the COP of the heat pump set up. If you were just using the GSHP to supply heat at very low temperatures to under floor heating (which would deliver the heat required over a large surface area so low temperatures will do the job) then you might get 5 units of heat out for every 1 unit of electricity you put in because GSHPs work most efficiently when there is a small difference between the output temperature and the temperature of the ground. However, if you were using it to run your existing, normal sized radiators and heat water for bathing etc, the higher temperatures required to deliver the necessary heat and hot water would reduce the COP to say 3 out for 1 in. Given that the power grid only delivers about 1 unit of energy as electricity for every 3 units of fossil fuels you burn, you can see that there is little emissions benefit in the second scenario.

    If you currently have a fairly modern oil boiler it seems suprising to me that your running costs in financial terms would be halved. You might like to question the supplier on the COP which he has assumed in his estimates. You might find that the capital investment in the GSHP could be better spent on insulation, draft proofing, heat recovery ventilation etc.
    • CommentAuthormoonmirror
    • CommentTimeApr 23rd 2007

    Wind speed at 45m agl (in m/s) 5.9
    Wind speed at 25m agl (in m/s) 5.3
    Wind speed at 10m agl (in m/s) 4.6

    Sorry got the square meters wrong its only 30 square meters
    • CommentAuthorGuest
    • CommentTimeApr 24th 2007
    Chris, very useful information. The make up of the heating is 2/5ths underfloor in a slab and the rest mainly upstairs is radiators so it would seem a questionable estimate of saving. I am working on the insulation and draught proofing. Alex
    moon mirror,
    Here are some clarifications for you.
    Your existing oil based boiler will probably run on biofuel with minimal modification there are many outlets and I can probably point you to one in your area.
    If you were to retain this unit and supplement it you will have all your heating requirements resolved. I would suggest a mix of solar thermal a large calorifier and a simple back boiler on your wood stove with perhaps PV/micro wind to power it as icing as your best renewable mix at the lowest cost.

    Other renewables could indeed power albeit rather expensively (Wind/PV/Hydro etc) your GSHP if it was small enough but unless you have a large collection area and an excellent resource group they are best suited to LTHW only. For a typical micro GSHP of 1kW e you would need to allow for around 8 hours use with a couple of starts during winter. You should contact the HPA in the UK for the best advice and practices.
    Were your pockets very deep you could even go with the 400 W wind turbine 100 yards away (size cables for volt drop),(does the river flow at the bottom of the garden as we can supply micro water wheels and this is much more regular) providing you have excellent site wind resources (suggest simple monitoring at the hub hieght rather than rely on BWEA figures only. These devices should then be coupled with a PV array for daytime charging to a battery set up of around 400 to 600Ah and an inverter (sine wave).

    First budget would be less than £5K and really quick second alternative is looking more like £20K and rip up your garden disrupt nieghbours etc etc let alone open up the can of environment agency abstraction licence and planning permission.
    PV and HRV work very well as they can use the heat gains when the house is in use particularily from bathrooms and kitchens. Some of our projects have used the DC versions to eliminate the conversion losses and downsize the plant even further.

    Unless you are islanded our advice would be do what your grandfather would of done but use better insulation and get the fabric losses down.

    Hope this helps

    Paul Johannsen
    Thames Renewables
Add your comments

    Username Password
  • Format comments as
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   

© Green Building Press