wardie9025

Thanks @JohnMo - I was thinking about this the other day and worrying a bit imagining the ASHP COP dropping significantly because of all the potential short cycling or just the rooms getting cold. On reflection though we have a thick (85mm, a bit more in some places) screed that seems to be doing a good job as a storage heater so this will help hold the thermal inertia in the system I think. Like the look of those and probably less hassle than a central unit - it wont do my external free cooling though and this is quite important to me in our project.

To update on this one I can confirm that following the cold snap, we do actually need heating upstairs! 🥶 To be fair no loft insulation in a good portion of the house yet though as contractor is being slow and I'm running duct work but gonna get it in for sure after the last week or two! Looking at 150mm duct work for heating as primary use. @joth - note you said 200mm as sweet spot but this was more for cooling? Would be really keen to understand your set up and experience? Cheers!

@joth - thanks very much for the detailed response! Very helpful. Some follow on questions If I may....: What are your flow and return temps for the water side to the FCU in heating/cooling mode? Are you able to advise what make/model or FCU and dampers you used. I know you can get a few different brands but I'm keen to understand what people have experience with. Are the baffles (dampers?) binary position or modulating? How do you control these/did you programme the Loxone yourself? Thanks!

Thanks @Dave Jones - I have looked at these but they are expensive to put one in every room (though I haven't done the sums on a centralised system yet, including my time to install). The other thing is the size on the walls and the fact that they don't allow for any kind of passive purge for fresh outside air, to essentially get free cooling. That said, I've heard a couple of people say upstairs heating isn't really needed with UFH throughout which I'm willing to try because we could always install a central unit in the loft later if needed but we do want to put some insulation in the ceiling/first floor to deaden some of the noise from the kids stomping/jumping around so this will reduce heat transfer upstairs. @LA3222- I was looking at something like product: PAW-FC-D40-1/-R (panasonic.eu)

Hi all, posting a link to this here as its a bit of a mix of heating, ventilation and MVHR topics. Would be grateful for any review and comment! Cheers, Gaz

Hi all, posting a link to this here as its a bit of a mix of heating, ventilation and MVHR topics. Would be grateful for any review and comment! Cheers, Gaz

Hi all, Need some external advice for heating upstairs. Background - we are installing UFH downstairs throughout and removing all rads. Heating to be driven from ASHP at max 35 degC flow temp, open zone control with weather compensation. The whole slab comes up and down in temperature together. I will DIY install MVHR from the wet rooms to supply bedrooms only but the 'official' ventilation method as far as building control is concerned will be trickle vents that we'll just keep shut. The challenge is upstairs. I don't really want big rads (really want to rip them all out to be honest so I don't have to worry about their pressure drop form the ASHP pump) and also want to be able to cool with the ASHP so thinking fan coil units and whilst I could go one in each room, I had wondered about a central unit in the loft. I'd also like to be able to purge the house with cool evening air to prevent overheating in summer so....I was thinking two inlets to the FCU with dampers that either pull air from the landing when in normal heating/cooling mode) or the outside when in purge mode. So my questions: 1. Am I insane? What am I missing that could make this more complicated than it needs to be? 2. Does anyone know of a good controller that could do this? If not my thoughts would be either a) I have some basic Arduino knowledge that I'd quite enjoy putting to the test on something real so I could build an override function for the purge mode and manually activate it, looping out the standard FCU controller or b) buy a relatively inexpensive PLC and pay a freelancer a few quid to design me a simple control ladder logic that I could upload into it. 3. Is there a good way of running the MVHR and the FCU supply through the same ductwork or will the FCU fan just completely override the MVHR unit fan? If the latter I was just going to run two lots of ducts Cheers!

I went to work this morning and forgot about this only to come back to plenty of replies...thank you all! To try and capture all points and follow on questions in one uber reply: @JohnMo - there was no insulation under the floor. There are now no floors with a new slab going down with some insulation on top before a tick screed (see orginal post for why having a screed as well....too late on that one). @ReedRichards - going for this one. HP was on the plans submitted to planning permission. @JamesPa - no sadly don't have this option but as above, was part of our planning submission for the build. @gmarshall - good to know and would certainly like to know a bit more detail if you're willing to share, either here or DM? Where abouts in the country are you? @gmarshall - agreed and lack of upstairs heating is also a concern here. After speaking with an installer who gets the low temp open zone systems with pure WC control he basically suggested that a) you might get enough heat upstairs from down stairs and U/S tends to be a couple of degrees cooler anyway and b) leave the rads in and then see how you get on, replacing if they aren't good enough. On point b) there's also a question about whether I want to leave old crappy single panel rads in my nice new HP/UFH system as im fairly confident they wont cut the mustard (not even finned!). I was also thinking the same, ref "charging" the slab so interested to know more about whether this is just on a timer or how else you have set up? Which panasonic model do you have? My other thought for upstairs was self-installed "warm air" heating so run ductwork and a coil into a ceiling diffuser for each room but as this is easier to do post main build from the loft I figured I have some time. Haven't quite figured out controls for that yet though..... @JohnMo @gmarshall @JamesPa - Ref the noise, I will review and do the calcs for siting to make sure its at an acceptable level. One question....if approved through planning, is it still subject to the MCS noise limits? Not wanting to be difficult or annoy the neighbors in anyway and clearly its not a V8 but it would still be good to understand guidance vs constraint in this context??

Hi all, We have an extension/refurb ongoing and I'm just looking to finalise the heat pump sizing. Having taken some advice I'm very likely going for a Panasonic unit. The dilemma comes to sizing so I thought I would ask to see what peoples experience suggests. We had some heat loss calcs done that assumed a 5kW heat loss but when I discussed with someone in the know this corresponded to an average heat loss of around 33 w/m2 which seems too low for a 1960s build, even after new extension and relay of concrete floor with 100mm PIR underneath the heating - moderating this up and assuming an average of 50w/m2 gives 8.32kW at -2 external. Looing at the tables that Panasonic provide, the performance of the HP drops at -2 to 7.38kW so my thinking was do I go for a 9kW T-CAP with no drop off in load at low temps or go up to a 12kW model - concerned about ability to modulate down and maintain good SCOP if I oversize too much! Efficiency has been the top priority of this part of the whole project. Planning to self install - MCS not worth it. I've included UFH drawings and some assumptions below so welcome any and all feedback! Assumptions: Assumed 50w/m2 heat loss throughout based on advice and looking at the heatgeek table and choosing a reasonably conservative estimate- not used loop cad for the calcs but that does spit out just under 9kW so figure that size would be fine on the basis that it would allow for some over capcity where I've been conservative. Pipes sized at 20mm throughout to minimise pressure drop. Plan to throttle down on flow rate if needed Pipes goi20230808-41NFR UFH Piping-v1.0.PDFng into 100mm thick screed (couldn't persuade builder last minute to drop the screed and go insulation under slab...long story and I've probably compromised a bit much but hey ho) so high thermal mass. Assumed, 35degC flow temp and a dT 2degC for the design but can increase to dT5 if needed depending on what flow rates the HP needs. Planning for a Panasonic Aquarea J series; self install - BUS not worth it as they just add the 5k on to take it off again. Hit me!!

Hi all, Thanks for the responses and very interesting conversation and sorry for the radio silence - its been manic whilst we finalise our build! Have now manage to design the system in loopcad and putting it up here for people to throw rocks at. Assumptions: Assumed 50w/m2 heat loss throughout based on advice and looking at the heatgeek table and choosing a reasonably conservative estimate- not used loop cad for the calcs but that does spit out just under 9kW so figure that size would be fine on the basis that it would allow for some over capcity where I've been conservative. Pipes sized at 20mm throughout to minimise pressure drop. Plan to throttle down on flow rate if needed Pipes going into 100mm thick screed (couldn't persuade builder last minute to drop the screed and go insulation under slab...long story and I've probably compromised a bit much but hey ho) so high thermal mass. Assumed, 35degC flow temp and a dT 2degC for the design but can increase to dT5 if needed depending on what flow rates the HP needs. Planning for a Panasonic Aquarea 9kW - for high COP; self install - BUS not worth it as they just add the 5k on to take it off again. Hit me!! 20230808-41NFR UFH Piping-v1.0.PDF

Thanks all for input so far. Long response....here goes.. @Dave Jones Good to know. I had considered adding a "trimmer battery" i.e heating/cooling coil to the MVHR outlet and if MVHR alone wont be enough to keep upstairs warm/cool then this is how I was thinking we could do warm heating/cooling upstairs. @Dave Jones, a couple of follow up questions: 1. What heat pump are you using? 2. How do you intend to activate cooling mode if OEM doesn't support cooling in the UK? I've seen you can buy a cooling mode resistor to activate it on the control board of some heat pumps and DIY install? I had thought I'd also like to be able to cool. 3. How do you intend to control water flow to the coil? Solar not planned at the moment as its very budget dependent. Intend to fit "for but not with" i.e. space in the dist board and run the cables etc and then fit at the end if money left. Thinking we need immersion heater in the tank, solar diverter and batteries if budget allows (have seen a great DIY example on here somewhere). Anything else??? Not done the sums yet but I don't think we'll need that much. We have 3 kids (but only one daughter!) - oldest is 9 so not at major hot water usage yet but we do want to plan for the future. If you don't mind me asking, what's your hot water usage - both volume and profile through the day? - walls - 0.6 - allowed for 75mm cavity for extra partial or full fill insulation in the extension. Existing walls are cavity wall insulation of unknown quality; possibility of suck out and re-install later? - floor - 0.18 - 100mm insulation under the slab. - roof - 0.15 - insulation is currently rubbish. Need to upgrade but I'll DIY this for the existing house. Sound reasonable??? @Dan F - excellent point. We will get as tight as reasonably possible but wont be looking to get to anything like passiveso yes, need to plan to include heating on the first floor. I guess this is where the coil on the MVHR outlet could come in as an easy win to get the heat in. Cheers! Gaz

Hi all, We are about to push the go button on a big extension/retrofit and I want to make sure my ducks are in a row. Final advice being taken on heat source (probably ASHP) sizing as well as a few other bits but want to make sure the bits that need to be finalised for the main build are correct. I've uploaded a PDF to show 1) where we are disturbing anyway (most of the house!) and 2) what my thoughts are around heating. 1969 house in Southampton with some existing extensions to be largely demolished and remodeled with the opportunity for significant changes to optimise the fabric and heating emitters whilst we move out. Please test me on the main points and assumptions to date: 1) floor is concrete slab throughout; we assume there is no insulation underneath and as the back of the house is to be removed, we have the opportunity to smash the slab up and and re-lay it to keep the heating consistent in the kitchen/dining/sitting area (see plans). If we do this, only the lounge remains so we may as well smash this up and relay as well. 2) aim is for very low temp heating system (targeting 35degC max at -2 external); 3) insulation under the slab with with pipes either cast into the slab or clipped onto the slab for high thermal mass. Pipes at 100mm centers throughout with no allowance for kitchen units/toilets etc (e.g. pipes everywhere). This sorts downstairs heating. 4) upstairs heating - either via fan coil rads or warm air? Have also had a suggestion that with an MVHR unit extracting from downstairs and supplying upstairs would mean that heating actually not required upstairs. Be gentle, but not too gentle! Cheers! Gaz 20230603-Heating and Plumbing (excl UFH pipe) -v1.0.pdf

Just about to push the go button on a retrofit UFH in the slab.....any follow up experience/comments as its been a few years since these works were done?? Any and all input very much appreciated! Gaz

Hi all, Just come across these.... Capillary Tube Mats - Radiant Heat for Natural Air Conditioning (beka-klima.de) Not big in the UK but seem to have a presence on the continent particularly Germany. Just wondering if anyone has any experience with them? Cant see anything on here from a quick search? Cheers!

Thanks @ToughButterCup! By 'that', I mean test ideas before committing funds - hope that makes sense? Mechanical engineer here.