yellowbert

Thanks @Temp - that is also a great point - perhaps fan coils for most of the upstairs on the same zone as the UFH on the ground floor - with some supplementary electric UFH for the bathrooms which can be linked to a timer / stat - that would give us the efficiency of a single zone for all the plumbed in heating but the flexibility of having heating in the bathrooms when everything else is off. I think I'll work through the individual room heat loss calculations, which may take me some time - I'll then share my workings on here which should hopefully be helpful for anyone else trying to work through the same process of designing their own heating system. I'm sure I'll make lots more mistakes on the way.

So if putting UFH or fan coils upstairs on the first floor - would you do this on the same single zone as ground floor or as a separate 2nd zone?

Thank You @JohnMo - this makes more sense than trying to hit the very lowest flow temp for that 1 coldest day. And just to confirm - when you say design flow - thats referring to the ASHP flow temp rather than the mean temp of the flow and return?

Thanks @SteamyTea - To be honest this is something we are a little worried about - PHPP calcs that the architect has done shows there won't be any problems, but it's a big leap of faith to just trust the numbers - a bit like trusting that we won't need heating upstairs! In addition to looking at shading some windows I'm starting to think it might be worth installing either UFH or fan coils or similar upstairs so that we have a method of heating if needed but also to actively cool in the event that rooms do over heat on those really hot days. That's also an excellent idea and won't cost much for the peace of mind that we can add the panel heaters if we need to in the future. @SteamyTea - This is exactly the kind of thing I'm not looking forward to quite so much as the other work - one of the things that scares me the most is shifting several tonnes of bricks as I'll likely have to do a lot of the demolition work myself to save cost 😬

Thanks @JohnMo that makes a lot of sense. So it would be better to do individual room heat loss calcs so that I can find the optimum pipe spacing for each room rather than having the same pipe spacing throughout. Once I know the individual heat loss for each room I can then use the graph to determine pipe spacing for various mean flow temps and I need to make sure that I don't go below the min flow temp of the ASHP. e.g If the min flow temp for the ASHP is say 25oC - should I aim to get all the way down to this with an appropriate spacing? I guess these calculations are all for the worst case coldest day - so would you also do the same calcs for the shoulder months to make sure the flow temp on those days is also above the min flow temp for the ASHP or does that not matter? Thanks again - Hoping to gradually understand this as its such an important part of what we are trying to work towards in terms of a relatively low energy renovation.

Hi everyone, 1st Post so hopefully it all makes sense 🙂 I'm currently in the design phase for our extension / renovation project and am trying to understand more about heat loss and UFH design so that I know what questions to ask and what possible issues to look for when we start getting our UFH quotes and designs back. I've downloaded and completed the "Heat Loss Calculator" put together by the amazing Jeremy Harris and calculated a Total heat loss of 3.55kW with -4oC Outside and 21oC Inside. To move forward and start designing the UFH layout: Do I need to do detailed individual room heat loss calcs? if so any guidance on how to get started with those. I've read that I should try to achieve UFH pipe centres as close as possible to minimise flow temps. How do I calculate whether 150mm or 200mm is appropriate? With our design meeting Enerphit - I've assumed that we would have no UFH upstairs - Is this realistic or should we include a 2nd zone for first floor heating? Is our ground floor U-value of 0.13 good enough for efficient UFH with low flow temps and will it be economical to run using an ASHP or do we need a lower U-value? For info regarding the thermal envelope: We are aiming to reach Enerphit and PHPP shows we can do this but we do have a few constraints - particularly with the ground floor construction, which needs to be a suspended floor due to clay soil and ground heave. Location: West Sussex Internal ground floor area = 132m2 Floor U-value = 0.13 (TETRIS beam and block with 75mm screed - UFH to be 16mm pipe within screed) Wall U-values = 0.12 - 0.14 Roof U-value = 0.12 Windows and Doors Triple glazed with U-value = 0.76 average Thanks everyone - feeling a bit lost and need some direction to get progressing again - Hopefully not too much info in 1 post.