I have a 12 year combi boiler and the company servicing it has highlighted a number of parts that are no longer available to replace. i.e. if one of these parts break it will be the end of boiler and an emergency job to replace it – fast!

Thus I am thinking that now is the time to do a considered (planned) replacement before a crisis develops. I am in a mid-terrace house with ground, 1st and 2nd floors. The main roof basically faces East – West, thus getting the sun in the morning, mid-afternoon, through to Sunset, precise timings being season dependent.

I am looking for green and energy efficient ideas and the companies to supply them. The only 2 things I will rule out are underfloor heating (am not prepared to tear up the floors {bathroom already has elec UFH}) and wind energy (a mast would not be popular /practical).

Your thoughts please.

  • Tony Taylor


    It sounds like your only options for ‘green’ solutions would be air source or ground source heat pumps.

    Air source is relatively easy to implement, however, they can be noisy and some do not work very efficiently at lower temperatures. It basically consists of an external heat pump unit which converts the outside air temperature into low grade hot water to use for space heating.

    Ground source is a similar technology, which is connected to a buried loop pipe or a vertical borehole, to use the stable ground temperature, which is again converted into low grade hot water to use for space heating.

    Both these technologies become energy efficient by converting the input energy into multiples of output energy, this is usually denoted as it’s coefficient of performance (COP), with figures varying wildly from 2 all the way up to 7. this figure means that 2 units of useful (output) energy are produced for every single unit of source (input) energy, for the former example.

    An air source or ground source heat pump creates low grade hot water for space heating, what this means is that the flow temperature from the heat pump unit is likely to be the region of 45 degrees C, which is perfectly matched for UFH, but not radiators. The normal flow temperature for a gas boiler is 80 degrees C.

    The low grade heat is also used to heat the hot water in a cylinder, another consideration, space and supply wise, with the hot water topped up to the magic 60 degrees C (to kill legionella) by an electric immersion heater, which defeats the object of being energy efficient!

    Unfortunately, your roof orientation is not ideally suited to solar thermal and this would only provide pre-heating for hot water.

    Without spending a lot of money and time, your best option would be to replace the combi boiler with a modern condensing type and also concentrate on how much energy you can save elsewhere.

    Hope this helps


  • Dominic Eves

    I pretty much echo the above. However, there is an option for underfloor heating without tearing up your entire floors. Google ‘Wundafloor’ they offer an overboard system, that can be laid on top of existing floors.

    We’ve installed their overboard system on our first floor of our self build. Check it out at http://aquatacklerblog.wordpress.com

    Any questions – feel free to email me at dom@theselfbuildsite.com

  • Andrew Walker

    Thank you both for your input. I shall bear your comments in mind as I proceed.

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