Ok, I'll respond to some points:
- The Ground floor UFH is at the bottom of 250mm of concrete, which is sat on top of 225mm of insulation. I expect it to be a strong stabilising influence on the internal temperature of the house, but have huge latency. It could easily take 24h to react to any changes in ASHP activity.
- Aircon is non-negotiable for me. It can react to changes in temperature demand very quickly, and provide substantial cooling and heating. Mrs Awesome is at the stage of life where her demands for temperature changes can be unpredictable and volatile. It's expensive to install and operate (coincidentally, Mrs Awesome...), but the UFH should keep things stable so it isn't needed frequently. MVHR does not have the circulation rates to provide decent levels of cooling. I'm very dubious about switching the UFH ASHP into cooling mode as I still want hot water in a heatwave.
- Yes, I have a big glazed gable but I will also be fitting external louvres and shutters to mitigate solar gain.
- I'm going big on solar PV / battery, and also will be fitting a basic but decent MVHR. My system is coming in around 5k for a 4 bed house, 12k seems a bit excessive.
My question is all about the MCS grant - if the UFH is providing heat to all rooms from the bottom of the slab, is that enough to obtain a grant or do I actually need to have wet pipes in all the rooms?