SuperJohnG

@LA3222 typical....I was searching for this very thing and you'd already done the asking for me. What did you end up doing? I have three of these pads from tanners too. But of a pisser really, I wasn't expecting them and seems to have added complexity (and costs). I'm now back challenging the superstructure engineer on his points loads. He seems to think I have 34 Tonnes of point load from a roof on a single story vaulted area only 7m x 8m. Doesn't add up to me..

Great wee story of your journey. Thanks for that.

Protek seems to be the cheapest and the go to here for being responsive. Thats who I will be using.

@Adam2 quick check and if I reduce my ACH to 0.8, the ventilation heat loss drops from 1045 to 418W

Apologies- I thought that was for @SteamyTea. 3 or 400L UVC heated by the ASHP, with secondary immersion. I had put in 2 ACH as I thought this might be conservative. But maybe its overly conservative? It should be fairly tight out the box as it is a SIPS build. Is that what you were referring to?

Defo does. But I'd agree generally where there is no feedback seems like as good as a yes, looks fine. 8.5kW and 200mm spacing it is, seems fine to me. Let me know if we have any issues @LA3222 I'm definitely glad you're a year ahead and pretty much same build. Very helpful. 300 or 400l UVC for you?

so does anyone have any thoughts - is it as simple as taking that maximum heat loss (3.6kW in my case) allowing some losses etc and then specifying an ASHP from there? I was thinking I would have to possibly go to a bigger unit than the 8.5kW but it doesn't seem like it now?

I wouldn't see why not as that void is vented to atmosphere, hence condensation wouldn't be an issue

I'd maybe plan my MVHR vent above the sink then as it'll minimise the run. I'll need to go figure out how many I need for that room.

By above - it's maybe 3.5-4m above.

Thanks. I am planning a duct above the hob - but I have vaulted ceilings, so it will be as close as I can get, but sure how effective. That's is my plan to to have opposite sides of room also. why an extract above sink?

Finalising my building warrant drgs and my architect has a duct going from Island to external for the Hob. This would need to pass through my insulated slab and I don't fancy it. I assumed it would recycle below the hob and then vent below the island to the room. I'm sure this is the case, but can someone confirm this is ok and that it works well that way? Bora, Neff, Siemens, Nikola Tesla etc. It's probably quite important as I have high levels of airtightness also and MVHR so don't want an external duct. thanks in advance.

I did and may well - but I wanted to understand for myself. I was planning on using wunda stuff as it gets a good rep (probably with an Ivar manifold as per @Nickfromwales recommendation - but that's a whole other thread ?, which I'll link with yours) So did you give wunda a required w/m^2 value (for exmaple simialr to my 27W/m^2 - then tell them to work it out? seems as through 200mm spacings will eat the requirement no problem. That's the bit I was trying to understand - are those w/m^" values what loopcad calculates as the required heat input.

I maybe haven't worded that correctly - I have used the minimum OAT and added this to the spreadsheet. I am using the line for total daily heat loss to get the output. I tried that link, but seems extremely difficult to find the data. But essentially we are saying the same thing I believe. Its the footprint of the thermal envelope, where the UFH will be (I.e. excludes garage) as it's about heat loss through the floor. I suppose doing it accurately I would include the area in the rooms above garage as albeit they are internal floors - they will loose heat like the ground floor as the garage is not heated and vented. I did a quick check and doubled the size and made a tiny difference increasing the power required by 150W.

@LA3222 this should make more sense now I've added the rest. ?? @LA3222 said

I've read various threads and views and back and forth and done some calculations based on information I have found here and of course from the very helpful spreadsheets provided by our friend @Jeremy Harris. I had pretty much decided ages ago I would get an 8.5kW Ecodan, which might go up to an 11.2kW ecodan unit. However I have not really advanced it beyond basic assumptions, what others done and some quick back of the fag packet calcs. I'm about to start foundations shortly hence, need to firm up on the UFH design for the in slab pipework and would appreciate some sense checking/ a wee nod that it seems ok. Build is SIPS with Kore insulated foundation, aiming for high levels of airtightness but not near PH (basically as best as I can get it without major hassle), Vent Axia Sentinel MVHR. ASHP which does UFH and DHW (UVC 3-400L tank). Secondary heat source of Log burner (I'm aware it's overkill likely - but I have 2 acres of woods, vaulted ceiling and need a backup in the event power ever went out). I would like to map out the steps in layman's terms to ensure they are right and I have followed it correctly from what I have read, then hopefully the thread can then be followed by others. Step 1 - Heat loss calculation: So I completed the heat loss calculator - see attached. I have a few checks to do on areas and might make minor adjustments but near as dammit it's close enough. I have added the OAT values for my local area (West Scotland, south of Glasgow) from the MET office. Now do I basically just use the 'Total daily heat loss power for average OAT (W)' value to find the maximum based on historical data and that defines the minimum amount of heating system required such below: which seems 3.6kW heat loss for January. The simply - I select a heating system which can supply this amount of heat as a minimum (ignore losses for now). So just simply selecting an 8.5kW unit would do the job easy? Step 2 - UFH design So Having found out the maximum heat loss above (3602W) then we can just plug this into the Heat loss and UFH calculator, which I have also attached. And provides the following output. So essentially, going on bare minimum I would need an UFH system which provides 27.7W/m^2 , based on 130m^2 of floor - so essentially if I don't use some slab area then I need to compensate and adjust the calc. Step 3 - UFH loop spacing So I know the total heat loss, I know how much heat input I have to supply per m^2 if I cover the whole area of 130m^2. So I get loopcad, then draw the circuits. Aiming for counter flow circuits as they provide the best option for even heat distribution, keeping circuits less than 100m in length. Now this is where I get a little lost, I have a figure of 27.7W/m^2 for the whole area to get my required heat input, however how do I correlate that with loopcad and also deciding what my spacing should be?! I have seen @PeterW mention quite a few times about the the spacing had to be adjusted but I am struggling to find the route here to confirm easily what it should be. My loopcad drawing (I've attached my current draft) showing for example 105W/m^2 in my living room, but I'm not sure how this should read in relation to my calculated figure. I'm pretty sure I'll need 200mm centres, but I'd like to ensure that was right. I've some adjustments to make to my circuits, but it's not far away. I was finding that the auto generate function for pipework isn't ideal but it works ok. The garage can be ignored - I ma installing pipework in there pre-empting possible future conversion of that area and hence pipe is cheap, so why not add it now. The manifold will go below the stairs - seems to make sense to me, I have a plant room directly adjacent and was going to put it in there but seemed better to get it out of there as I will have lots of ducts and this would clutter that up. Is it ok to run underneath the stairs? I assume I just have to tell the Joiners not to fit the stairs to the floor with big screws?! Step 4 - Zones I am only having downstairs heating, so it is a single manifold. I would prefer as few zones as possible, but a single zone wont work. I was thinking I can have two /possibly three. Zone 1 - Main family room area Zone 2 - Everywhere else excluding shower room and garage Zone 3 - Shower room Zone 4 - Garage (permanently isolated at the moment. I assume you can have multiple zones on a manifold, and can just split them up by using salus actuators?. So a single thermostat for family room can control three loops (each with an acutator) in that room? and so forth?. It's a long post , and actually I wasn't going to talk about zones but thought it was worth adding in. Thanks. Heat loss calculator - SuperJohnG.xls.xlsx Floor heat loss and UFH calculator - SuperJg.xls.xlsx Looopcad - SuperJohnG.PDF

This has been a great read. Like every fault....its so hard to see the obvious answer at the start...whats changed! Well done.

Id agree with @nod but that assumes you've planning, building warrant and funding in place. If not add 6-8 months minimum.

What a diddy of a person. Right decision...bin for them!

What fancy tools are we talking here? Standard type plastic pipe like speedfit or hep20 just require a pair of snips to make.lofe easier. You can buy cheap ones at 10 quid or say rothenberger for 50 quid. But not much more than that I am aware of?

Looks not bad to me...if I jave a spare 5 mins tomorrow I may just run it through mathcad. Its definitely a good analogy ?

I'm genuinely interested in how you did this calculation/ know this.

Thats pretty good. How did you get the prices with midsummer though? Was that a trade account.

Let's ignore the logical approach and cost weighted arguments, sometimes I feel we can assess too much here rather than just following what feels good. If you have the cash...spunk on the 8k, if not get what you can. Save the planet a little,.it might not be economically viable but its an easy way to pay back the earth by doing your little bit. By the way who is that quote from?

Thats seriously cheap I assume this is 8kw ? Thats midsummer solar. I asked if they would bring thr price. Down to trade prices but he says he won't. @canalsiderenovation seems to have accessed the trade prices somehow? His is around 25% cheaper. I could always try and see if they were interested in offering forum discount. Has to be as good as having a small trader buying repeatedly.