Go to Forum Home Building Services Air source heat pump +?

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    • #31471
      Anonymous

        I am building a fairly substantial very well insulated new house (lots of thermal mass) and propose heating via air source heat pumps (2no.3phase), part u/floor but mostly ducted warm air. My question is, should I also consider solar thermal or should I use the air source 24/7 for both hw and dhw to get the most out of it. I will have a fairly large summer demand for heating /hw as a result of an indoor pool.

      • #37892

        I can't see any reason to use ASHPs, except the grant.

      • #37893
        Alan Clarke
        Participant

          2no. 3phase heat pumps sounds like a big electricity bill!

          You probably want to look further at heat recovery from the pool before turning to heat pumps.

          Solar thermal is a pretty obvious choice for pools normally – collectors work most efficiently at 30C or so, and day to day peaks are smoothed out by the mass of the water in the pool.

        • #37894
          Robert Rickey
          Participant

            David,

            I am doing a near PH refurb, on the gas grid and will be installing PV via a local buying group. I had intended to install a new boiler sized for the job with a thermal store, but a local ASHP salesman suggested that the combination of PV and heat pump would reduce energy use generally and costs. I haven't tried to analyse it, but why is the gas boiler still the favoured option?

          • #37895

            How can a house, presumably high-mass and glazing to match, overheat in average temperatures of around 8 degC in April and 10 degC in October? There are thousands which don't.

            This seems to be at variance with the principles of physics.

            Unless you are in a region like the Channel Islands, you will probably need a second heating system anyway for severe weather.

          • #37896
            Anonymous

              I too was surprised by the M&E consultants view as to overheating, however, the house (in one of the southern most points of the UK) will have some 150 sq.m of south facing glazing. The windows are deepset / overhung and will therefore be shaded when the sun is at its highest and hottest in the summer months. It's just that when the sun is low and still has some warmth the overhangs will not come into play. We only very rarely see a frost down here though I have specified a couple of 8kW wood burners for the two main living spaces – just in case.

              Coincidentally, I looked at another house nearby last week in order to view a glazing system similar to the one I'm thinking of using (U-value around 1.1) and where they also have high thermal mass. The owner has only recently moved in and is already complaining of overheating. They too have a woodburner but have only felt it necessary to use it twice this last winter.

            • #37897

              If a house has natural gas, installing an ASHP plus a woodstove and maybe electric resistance water heating seems an expensive way to make clinmate change worse and double or triple the number of space heating/DHW systems you need. Why do it?

              Similar with a rural house with space to store LPG, in my view. That plus solar has emissions well below an ASHP (note solar plus an ASHP doesn't make much sense for technical reasons, too long to go into here.)

              As for the overheating, if it has 150 m2 of south glazing, does it have 750 m2 of floor area? Have you done any analysis with PHPP, either by yourselves or a consultant?

              Suffice it to say decent building designs in central Europe (e.g. Vienna, July average 21 degC) can be kept comfortable in heatwaves, so I think something has gone significantly wrong if people are facing overheating in almost the coldest summers anywhere in the EU.

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