WillM

Thanks for the detailed reply. In answer to your Q's I have not got MVHR and it has not been renovated to PH levels but the builders have worked on PH houses before and have taken care everywhere to minimise gaps. This is entirely anecdotal but I was very surprised how quickly it warmed up in the main open plan living area from just one small electric radiator and 1 tiny blower heater having been on to get some of the plasterwork drying out so I am hopeful on the actual efficiency levels in real life. I assume because no MVHR I cant accurately calculate the air change per hour ? If so, any advice what value I should put in cells B5 and B6 please?! Regarding your comment about your boiler being massively oversized, if its modulating and providing the heat you needed at 54% of its potential max then is it burning more gas than a boiler that is correctly sized but running at higher % of its max potential output? Apologies if these are elementary questions - this is all pretty new to me!

Thanks for the advice. Is an "X plan" common language? Ie will my fitter know what I am on about if I say this to him?

Can anyone direct me to a good U Value table of materials please?

This is exactly my gut feeling - thanks for confirming all points.

Yes insulation under the UFH but total house U value still higher than is ideal for ASHP. I have run the new internal pipework in the size that will fit with an ASHP if we want to go that route in future when prices for pump and electric hopefully reduce. For now though the LPG made the most sense overall. I dont have enough south facing roof to make a big enough solar install viable either.

Thats great, thank you. I'll have a play later!

Hi all, I have got a completely renovated and now well insulated 4 bed detatched house with wet ufh throughout , 1 bathroom, 1 shower, no radiators. Original build date was 1970, filled cavity external walls. 1600sqft over 2 floors. The main living area is open plan with double height ceilings and a lot of glazing. My plumber has said “min 30kw LPG system boiler and min 210 litre indirect hot water cylinder” My concern is that this a bit too vague for my liking and he hasn’t done the proper maths! Maybe it’s fine, but would be good to know if anyone here knows better ?? thanks in advance