ChrisDL

I was going to ask the same question as this topic. I was planning on running 22mm hot and cold to each (15m ish will be the furthest distance to bathrooms upstairs) wet room/area of the property then branch down to 15mm for each element from a smaller manifold. Sounds like 10mm for toilets seems advisable. Is there a recommendation or preference for using PEX or polybutylene pipe? Many thanks.

16m2 is the allowed for space. But granted it will be gobbled up. Again, the preference for one unit if possible.

Thank you for the recommendations. I will follow up the suggestions.

Good to know... but as a single or double run?

Hi Dave your experience sounds unusual as I believe Zehnder are one of the most premium brands... Might go to show that I don't need to spend top £. I see few people have complaints with the Vent Axia's and buying two units could save me a lot.

This is interesting, I had wondered if a commercial unit might work... But have assumed it would be noiser and since it was likely to be in less noise sensitive areas, office, school etc. I will call them though. Did they also supply you ducting or did you use another brand for that?

Good to know. What brand unit and ducting did you end up with and are you pleased with it?

If I do end up with two units they will both be in the same central room in the home. Unfortunately no opportunity to have units either end of the house. I have measured today and the longest run to a bedroom will 16m. Which I could double up.

Yes, reading the forums this is something not to be missed and I was planning to include decent attenuators between the MVHR unit and manifolds. If all the units will sound equally quiet at the valves that is great. At the unit itself won't matter being in a laundry/utility room at the rear of the house. Reliability and efficiency are probably the other considerations. Again one large unit if it existed would mean I don't have to double up on attenuators, manifolds, supply and extract atmosphere ducting either.

Good morning, I am wondering if anyone has any recommendations for a large single MVHR unit? Or would I be better off with two? I have had some preliminary discussions and quotes from suppliers which have all recommended two units... but I guess it is in their interest to sell more! The property is quite large at 530sqm. Based on building regs 1.08 m3/hr that will equate to 572m3/hr - based on the advice I have read on this forum and running a unit at 50% I would need two, either Zhender Q600, Brink (Ubbink) Flair 600, or at the more affordable end of the spectrum Vent Axia Kinetic High Flow. I don't want to spend more than is necessary, but quietness of the system is paramount, I would hate to have buyers remorse and wish I had purchased another unit. I am about to start some calculations for duct runs to see if I will need to double up any 90mm semiflexible ducting - from the manifold to the extract/outlet the longest run would be about 15m. On a side note has anyone had any experience with Blauberg Blaufast ducting/manifolds? https://www.blauberg.co.uk/vents-ducts/semi-rigid-duct-systems ? Thanks.

Hi Nick - Yes it is the 380's.

I have also fallen foul of the Insulhub liquidation. Slightly different from some of the poor people here in the fact I have probably 3/4 of the materials to finish the house - but not enough to finish and no garage.... What is also so disappointing is the support and knowledge has been pulled from under our feet as well... I notice @Nickfromwales comments in not recommending a Woodcrete block... which is a shame since I have one! I was considering a parge coat and was relying on Insulhubs team to guide me.... unlikely to happen now I suspect. I am wondering what the recommendation to might be to those of us with a partially built project? Just mix in Nudura? Many thanks, Chris

With respects to Zoning UFH, would people recommend minimum as possible? I was thinking of running the entire downstairs as one zone. But upstairs individual thermostats for each bedroom. Depending on preference I guess.

This sounds simple and effective. Ideal. 👍

Evening all, A few weeks ago with the help of this forum I managed to get my head around my UFH requirements, link here, Thanks to @JohnMo @Adsibob @jack . Now I am looking for help regarding combining a ASHP with a backup oil boiler. Should state, we are off grid, and although we are installing a very large PV array - electricity will be our limitation in winter and hence the need for the back up oil. If anyone wants to see my heat calculations/energy requirements click here. So my first question is does anyone know of a way to control a ASHP by way of battery level or PV generation or a ASHP with the ability built in? All the ASHP I have looked at advertise a back up facility based on outside temperature. My first thoughts were I could completely switch off the the ASHP by automation when the batteries are depleted past a certain level... but I am wondering whether ASHP would suffer from being turned off/on like this? Second question, assuming I can make a ASHP work, is regarding the rest of the components. I should trust my plumber... but I would like a understanding. After much deliberation and reading on this forum I have decided on installing a UVC rather than a thermal store but I am a unsure on the buffer requirements. Below is my bare bones understanding. Do I need a buffer between the boiler/ASHP and UVC as well? Also out of interest if I decided to add a biomass boiler to the design instead/with would I need a buffer then before the UVC or before everything else?

Just received back a design based on two Vent-Axia High Flow units which I thought I would share. A lot of the runs are pairs of ducting (denoted by the number below the diffuser), I wondered if one 90mm would suffice for these long runs but two 75mm will allow more volume. I haven't got much to compare against other than one branch design which I have dismissed. Does this look sensible to people? Tweaks/suggestions I can ask to make?

Thank you @jack and @JohnMo. Looks like the my calculations are not too detached from reality! Which is reassuring. My expectations are based on my folks old place which absorbed it's own mass in energy daily and was never really warm. I will plan for 250mm spacing which should give us plenty of margin for adjustment. @JohnMo could you explain circuit pressure for me? Is this essential information to know?

Thank you @jack and @Nickfromwales. Ha, No we are a family of 5 with 2 dogs. We will have extended periods of time with family from abroad staying with us but no more than 10 people for more than a few days max... that's more than enough of the in-laws! It would appear I would probably be pushing it to drop to one unit... and may very well regret it - it won't be desirable to retrofit another unit in once we have moved in. Does anyone have an opinion on the boiler flue positioning?

Thank you Adsibob - yes I have calculated a spacing of 250mm. Going to see if I can drag @JohnMo back into this to check the sheets I have filled in below. I don't understand the circuit pressure. I assume I should be doing this on a per room/ loop basis rather than the whole house? Wondering how common it is to be running such low flow temperatures...

Evening - rattling through future issues. Couple months ago I made use of @Jeremy Harris heat loss calculator to try and size a ASHP, link to that here. Moving onto UFH - from these calculations worst case scenario I may need in the depths of a very rare, dark and cold winters day 7kW per hour of heat energy to maintain our 21 deg C. Our barn conversion has a ground floor of about 300m2 and 200m2 upstairs, I have been recommended to go belt and braces and install UFH upstairs, more so because we have a concrete first floor. We are planning to have a polished concrete floor across most of the ground floor. I have read that UFH concrete has, albeit maximum, heating output of 100W/sqm. We have one central room of 100 sqm which could potentially throw out 10kWh itself. Now I would like to believe my plumber will recognise this but I am not so sure. Hypothetically with UFH upstairs and downstairs we only need 14W/sqm. This is where my concern lies and I would like either reassurance or someone to find fault in my calculations/assumptions. Since otherwise is UFH upstairs unnecessary? Or is it possible to run UFH that low? Spacing the loops extra wide, very low flow temperatures or rates. Appreciate any feedback/thoughts. Chris

You have confirmed my gut feeling and obviously the recommendations from suppliers. You pleased with your Brink though? It obviously operates quietly. Is it Vent Axia priced or closer to Zehnder products?

Couple of questions regarding peoples experience with MVHR Sizing and whether they have any brand recommendations (quietness being my main concern). I have only been in a property with a DOMUS system and admittingly did not notice it. I have been looking at and quoted for Vent Axia units and wondered what real life opinions of them are? Zehnder I been quoted for as well and I am sure they are dood but - but considerably more expensive and if I have to buy two.... I have also heard the brand Brink on these forums but can't find many opinions on them. Back to the sizing. We admittingly are a large barn conversion, 500m2, internal volume is basically 1500m3 with a large vaulted space. So far all the designs I have had back have recommended 2 units... and I would probably err towards the side of caution and go with that. But wondering whether if in reality I could get away with one to keep things simpler. I found this on PAUL Heat Recovery which suggests that a 500m2 property will need 375m3/hour to maintain a good Indoor Air Quality - anymore and it will be too dry. The Vent Axia recommended has a a 575 m3/h Airflow rate @ 100Pa which would mean it would be running at 65% of its potential. Would this be too noisy or overstretching one unit? Also whilst at it. Oiler boiler flue siting in respects to the MVHR. I can potentially house the oil boiler in the garage 35m away from the inlet of the MVH eliminating any risk of fumes... however it will be easier to site the boiler just behind the plant room, where the MVHR inlet/outlet will be, and I am wondering if I have a flue extension rising up to the eaves of the barn will said fumes be taken away enough not to get sucked back into the house. Wondering if anyone has any real world experience on this. Appreciate the opinions and recommendations.

Thank you for the above. Having a quick sum up I reckon my demand for heating energy and DHW will be almost equal across the year. Of course heating much greater when there is actually less PV. I suppose in a ideal solution one would have two heat pumps and two cylinders. One running at 30 for UFH and another for DHW. Compromising does a thermal store benefit UFH and ASHP cop more? Since it will be drawing heat from lower temperature water?

Trying to calculate flow rates.... Maybe someone can correct me if I am wrong in this assumption. Worst case scenario (cold day/no solar gain)- we may need 8kWh in heat energy per hour to maintain a balmy 21°C inside. From UFH running at 29°C (I think polished concrete can't push past much more than this for fear of cracking) returning at 21°C we need 900l an hour or 15l per minute. So about half the capacity of a 12kW heat pump until we start using showers/baths etc. So can heat pumps not run at half power? Or otherwise a buffer? Yes we are sizing for 6 - since there may well be 5 in a couple years and then guests. I do want a hybrid system of sorts. Because we are off grid I need to be able to tap into a oil boiler or alternative when the PV generation is not there. But when energy is abundant is makes sense to maximise using a heat pump I guess. There are the odd crisp sunny days in winter when our batteries will be charged and we have excess electricity - original thought was to dump this into a thermal store... however @ProDave and others a Thermal store is not often recommended. Consequently still looking for this buffer and 'thermal battery' in a UVC system. I feel like I am approaching the question of whether say a 500l UVC will suffice for DWH and heating ? Or do we need a buffer as well? With respects to the 'professional services' one recommended a 300l buffer with a 300l UVC the other a 180l buffer and two 305l UVC's In fact whilst I am at it... what even is the 'buffer' surely just a larger UVC will suffice? Another question on my mind is since there is no temperature stratification in a UVC how is that optimised for UFH? Sorry for all the questions.

I had calculated at 50°C with a starting input temperature of 5°C in winter. Calculated this to require 23.57 kWh of energy to heat. However I realise now this is overcompensating as 50°C is too hot for any purpose and will be blended down. However I was originally thinking along the thermal store route..... In summer not a problem we can have the immersion running all the time to heat water but in winter we won't have the PV spare - back up generator yes - but converting diesel to electric back into heat isn't as economical as a straight up oil boiler... although it is simpler.... And if the ASHP still has a SCOP or 3 it will get back up closer to oils 10kWh/l