Shaun McD

Sorry, my bad! I just assumed the zero VAT rate still applied without confirming!! Since it no longer exists then naturally this thread is out of date and can be ignored! Thanks for taking the time to respond @Conor

Hi all, We are started our self build just over the border from Northern Ireland, and we have a VAT rate of 13.5% on all construction materials here. During our last self build 8-9 years ago, we found a few suppliers in Northern Ireland who sold us materials at 0% VAT, provided we collect ourselves. Does anyone know what sort of tracking is done on new builds in Northern Ireland for this? For example, if I can get the address of a new build in Northern Ireland and say buy a heat pump, have my address as the new build in Northern Ireland on the account, but collect myself, is there any chance that the new build would get audited and someone flag that two houses worth of materials have been purchased against it?

This is very similar to what we have chosen, we are using a breathable racking board, we have opted for a 70mm internal insulation board, and in place of the VCL, we are taping the joints. Another detail we have is to return a 25mm insulation board on window jambs to kill the cold bridge from window to frame. We have a calculated wall uvalue of 0.13. Our frame is 400c so hoping that will help with wall firmess, but may still look to use OSB behind kitchen, and otherwise use 15mm or 2 x 12.5mm for utility/plant room.

I think with the doors opening in we will be looking to place mats on the outside of the doors (both have covered porches) I looked at their site and all the glue down options stated as 2, 2.5, or 3mm, do you know that to be incorrect?

Hi all, Finalising details for our insulated slab and need to lock in door threshold heights! As confident as one can be with an impulsive other half, we plan to use Karndean (or similar) glued down for the 3 areas with external doors, two open in and one slider. We have not yet picked the specific style of floor and when I spoke to retailer, they recommended leaving 7-9mm for a flush threshold height (3mm leveling, 2mm glue, 2/3mm floor covering). Can anyone confirm those sound right before we lock in heights? I am leaning closer to the 9mm side and can also compound floor up a little at doors it needed, Kind regards, Shaun

Hey John, I am by no means an expert in this field, I did the design and installation in current house and planning the same for the next one. Couple of small points maybe worth considering; Loft location is convenient in one way, but is also a torture in another. You need to access the machine to change filters (twice a year for us), and when my machine played up a few months back, it was less than fun getting it down the attic stairs to have a full inspection. If possible, I would look into placing the unit in a closet or wardrobe on the first floor. I wouldn't be greatly concerned with the balancing between floors since the overall balance is correct, but, I would also possibly have a look at having two machines, one upstairs, one downstairs. As you can opt for smaller units, the price may be very similar, but gives you more overhead if you want to run higher rates than those listed without much stress on the units.

Apologies for the rude statement, i would like to edit this to state that this is my experience with SOME plumbers, and it is clear based on this forum alone that there is a huge difference in how some wish to operate! I have no doubt there will be plenty of plumbers who would be happy to work of a design and also provide input free of charge, like several on here who have given their time and knowledge for no financial gain, but they are just tough to find in my area! I will endeavor to keep hunting!!

Plumbers have very sensitive ego's, they seem to struggle to do what the customer asks, let alone take some other mans seconds...

I feel your pain @Jimbo37, based in Donegal and finding it very difficult to get anyone to "design"! I think we have had maybe 1 reputable installer so far ask for heat loss, and i asked a couple of others if they would not need to know heat loss, one answer was that he uses 40W/m2 for new builds. Thats at 25 deg temp difference, and maybe is not terrible, but my calcs for 25 deg is 15.9W/m2, so would be some what overkill to install a heat pump to hit 40! One of the main challenges I have found, as others have also stated, is getting a machine as someone not in the trade. A couple of plumbing supply stores will sell me a machine, told me they wont give me the same price as the plumber (odd) but that it will be sold as seen, zero warranty. I have had a little more luck with commercial refrigeration companies, e.g. a company based in Donegal told me that they will sell me a Daikin unit, and if I have their engineers commission and do an annual service then they can provide the full 7 year warranty. There is options out there, just a PIA to find! I am trying to work with some local plumbers and take an active role in design to see can I find a happy medium, but may end up a DIY job yet

Great information, maybe I am naive but that seems like a great result, free daytime PV running the HP in cooling mode and seeing upwards of 5 degc temp offset, id be delighted with that!

Nice point on insulating loop feed lines, would never think on these things! Is handling which area gets flow first just position on manifold? all very interesting, I have yet to get into too much detail on the cooling side! Main factors so far are the solar gain redistribution and opting for a heat pump (if possible) with a cooling function. On that note, again on pipe spacings, using flow rates and pipe spacing to help not over heat areas with higher solar gain seems clear, but on the flip side, when it comes to cooling the slab by pumping around 13-16deg C water, would it not be a plus point to have more pipe, i.e. less spacing? The principle that the more water in the slab will allow for more heat extracted? Having pipes at 300 centers are bound to be less efficient at cooling the slab than at 100mm? I am sure there is maths that can be done on how much heat can be extracted by volume of water i guess

Thank you very much @SteamyTea that all makes sense now! Will try do some calculations and see where that leads but open to the idea of using different spacings now! I assume, if rooms do not share loops, a portion of this can be achieved by adjusting flow rate for each loop? From what I have seen though, the controls on this are not exactly fine, so I guess you wouldnt want to be relying on this as your only way to control it, thus the need for different spacings?

Ok so during shoulder months and I assume summer, run the pump during sunlight hours to help circulate the solar gain? This is very interesting and first time I heard this perspective. If I'm right then basic principle is that the risk of defrosting is much greater when the ashp is working in dhw and much less risk when doing central heating temps regardless of the load? So to help this one should try avoid having the ashp heat the dhw? Is that the general idea? An example of the setup, say for Nov - Feb, reduce the ashp set point for dhw way down, and set a timer switch to bring on the immersion during night rate electricity to top up the tank to a modest set point of say 50c, and have pv add input whenever it can? Sound about right? What sort of oversizing of uvc would you recommend?

Great to hear! In your photocell example, does that mean that when the ASHP runs at night you are not running the manifold pumps? Help me understand this, if each room has one large window then for sure solar gain will be different, but assuming the same fabric, losses will be pretty close to each other no? So since from a heat loss perspective would the emitter size not be the same? I appreciate if you can accurately map solar gain then you could decrease the emitter size appropriately, but not seeing the downside to keeping them the same? This is backing the concern with using room based stats at all, but I get stuck with the idea of maybe sometime for some reason liking or needing to have the ability to set room temps independently from each other, e.g. trying to keep a bedroom at 18/19c v centralized living at 21c. Think I will just have to come down on one side at some stage Interesting, yeah was pretty set on mixer valves based on reading here!! I guess I could still achieve the solar gain redistribution with a 2 way valve and pump. Would never have thought a bleed would have such an impact, and once you removed mixer you found 26c ashp output and 26c input at manifold?

Thanks @ProDave, why always a 2 port valve for each manifold and DHW? (ignoring solar gain redistribution). Would the one for DHW not be surplus to the valve controlling heat V DHW? House is single storey but in 3 connected blocks so hoping I can treat it as a single input for heating, and allow for solar gain redistribution within each manifolded area, i.e. east side of house & west side of house. Appreciate your point on general answers, learning from this thread and others that there is more difference in ASHP controls between manufactures than I was expecting!! I will be sure to get into more detail once we have downselected the manufacturer we want (can get)! Tbh I am struggling to make sense of any solid calculations to know for sure which is the ideal spec, but I have used Jeremys spreadsheet for total envelope loss, and spent some time in loopcad doing this by loop etc. (I do need to fine tune this) Re. pipe spacing, while I appreciate it may not be strictly needed and not be the most cost effective route, I am struggling to see why I would not default to 150mm pipe spacing; It will allow for larger volume of water so that either manifolded area would be less dependent on the need for a buffer My understanding is the more water in the system available to output heat, the lower the water temperature can be With the kore insulated raft foundation, the is much larger than standard volume of concrete, acting making me think that having a large heat emitter running at low temps is better? These may not be great reasons, but on the otherside, I dont know what the downside to taking a cautious approach to this is, outside of cost of materials, labour at installation, is there any drawback to smaller pipe spacings? Thanks @JohnMo I think my two manifold areas can be 120m2+ each (house 265m2), so im hoping that by taking the volume of water in the smaller of the two manifold zones and using that as the basis to require/size a buffer. Note taken on WC, makes sense! Can I ask how the pump and mixer was causing a drop in temp? Is the point of the mixer not to set the temp for all loops on that manifold? Is it in the response time that you seen an improvement then? And (assuming you have an upstairs manifold and a downstairs manifold) did you remove both pump & mixer from both manifolds or just one? Sorry if this is a simple question! Thanks for this @Temp this was my thinking based on previous experience with a gas boiler system, but I had assumed (again prob incorrect thing to do) that this would not be an ideal setup for a low energy build? I would have thought I wouldnt want to give any single room the ability actually turn on the ASHP in order to prevent short cycling? My thinking on what would be expected for this type of system; North facing room drops below room stat set point, opens manifold loop for room. Manifold pump is triggered, pumping open loops in this manifold combined with now open north facing room. If north facing room takes enough heat out of open loops then this will drop the temp in these zones, where a centralised house stat lives. Only when this centralized stat drops below its set point (meaning that the whole manifold zone is at or below this temp) then will the ASHP trigger? I was thinking the alternative would be to remove the room based stats completely and have either 1 centralized, or 2 (1 within a central point in each manifold zone) call the ASHP, assuming that the heat distribution within the zones will work itself out? Seems to be others on here who start out with loads of room stats but end up removing them. I have been using Jeremys calcs for whole house and then loopcad as a starting point for each "room", but I am thinking I will do a more exact room by room sheet alongside loopcad in the coming days! @PeterW Am I right in that you suggest this as it is really the more fool proof option? Meaning that while it may not actually add any efficiency to a well designed system, it will help an otherwise poorly designed system? Second question, since the stat on the buffer is reading water temp v room temp, im guessing that this is either accounted for in the ASHP controls or do ASHP controls typically have input options to state that the stat is reading water temp v room temp? Suppose what I am wondering is does this make it a little bit trickier to set room temp, as there wont be a direct match from the buffer temp to the temp we want in room? If I want to set a room at 21c, I cant tell the ASHP to look at the buffer stat and heat it until it 21c right? This will be a different number... Third question if I may, I have been looking at UVC's and looks like we have 3 priorities to hit, 1 - Coil size suitable for ASHP, 2 - Element location for PV (bottom of tank), 3 - Volume for our usage. I seen the, for lack of better phrase, "combi" cylinders which have both UVC and buffer in one, e.g. https://www.jouleuk.co.uk/pre-plumbed-heat-pump-package-w-buffer/ While this option looks to be a no go based on priority 2 (location of element for PV), assuming that such a tank exists that meets the 3 priorities and has an inbuilt buffer, are these a good option, or do you typically always opt for a stand alone buffer? Last question on this ha, any logic in having a buffer with an element connected to a secondary PV output?

Hi all, getting closer to signing myself up for the plumbing and heating on our new build but have some basic heating system operations that I would like to clarify/confirm to make sure I am not missing out on anything! So basic system; Mono bloc ASHP Appropriate ASHP suitable DHW Cylinder Assuming no buffer tank UFH coming from 2 manifolds; - both manifolds will have pumps and blending valves Questions; How does ASHP know the DWH needs heat? I assume it connects to a probe in the cylinder? How does ASHP know the heating system needs heat? Is this via a temp probe somewhere in the house connected to ASHP? If the above is correct, I assume the ASHP uses this and the outside temp to work out temp of water to output based on weather compensation? Does each manifold need to have a motorized valve to disconnect it from heating circuit? (Mainly curious if this is best practise, but in reality I plan to opt for this to allow for some sort of solar gain distribution like Jeremys) It looks to be standard practise to have a stat and valve for each manifold loop, and if any of the loops is calling for heat then this is the trigger to run the pump on this manifold? If I opted to run without stats in each room, how would the manifold pumps be triggered? (ignoring whatever solution is used for solar gain distribution) Would this be linked to the trigger in point 2 above? Thanks in advance for input and no doubt follow up questions!

Yip pretty much, have only found one installer who is keen on ashp and i am struggling to get a response from him! Hoping someone in the forum has a recommendation to reach out too!

We have a GSHP in our current build which we chose at the time, around 7 years ago. Fully agree that the CoP WILL be better with Geo, and concepts like borehole recharging only help that further. The issue however is the initial capital to install v ASHP, specifically in highly insulated and air tight houses. I just cannot make the maths work unless we get incredibly unlucky with ASHP unit and weather, that the higher CoP by the GSHP will come close to offsetting the higher capital costs. I have tried to have these conversations with the local installers and its clear that they want to opt for the more general idea that better CoP is the only consideration to consider. All of this combined with ASHP units needing replaced at 5-7 years, terrible real world CoP values for ASHPs etc. for them make the option very clear. I think however the data they are using is skewed, and like everything else bad new travels far. The majority of installs over recent years here are ASHP so of course there will be some bad designs resulting in machines running constant, giving both high bills and reduced life of machine. Based on the research I can find, and seems backed up heavily by this forum, a well designed ASHP system, while never achieving the CoP of GSHP, and lasting an acceptable life of 10-15 years, will pretty much always be the cost efficient option. Thanks for the vote of confidence on the DIY option, I feel like it is partly crazy but also maybe the best option ha! The heating system can pretty much be designed on here from what i can see, just need to get some understanding of regular plumbing best practices now too! Soil pipe vents, water hammer, etc. its a long and daunting list!

Hi all, Very much on the fence to DIY v tender out the heating system supply & install for our new build. Naturally there are some massive RISKS to a hobby diy IT professional taking on the task, regardless of savings available! I am basically writing off any hope of warranty for one! A major PRO that has come out of a few months research and conversations with local professionals is that it will indeed save a chunk of money, but also will allow for best practice install in materials choices and equipment choices, e.g. having pumped manifolds with blending valves is not on the list of options for local professionals, with some going as far as saying they would not warranty the job if I insist on having them installed! Another recurring issue is around GSHP v ASHP, with several local installers basically pricing themselves out when I push for ASHP. I have had no less than 3 installers tell me that I MUST install the next size up ASHP v GSHP, with some suggesting that this is even on the low side. Maybe its my simple non professional brain, but I understood 6kw to equal 6kw regardless if ASHP or GSHP, and all they really changes is the amount of input energy to get 6kw, not that an ASHP will need to be 8kw to output 6wk of heat! With this in mind, does anyone have any recommendations for installers either local, or willing to travel for such an install? Feel free to private message if you would prefer not to share private contact info, but would appreciate any help on trying to find people happy to do the job and know how to do it well!

My own personal experience, I am glad we went through an architect for design. We tried to get input from down selected TF companies to help on a redesign, but in reality, its the big obvious things that hit the pocket hard, not really having walls not in multiples of 4/600mm etc. Roof layout, projections, curves, non standard heights, large spans without the ability to support will all cost, and you just find a balance between budget v design. Some TF companies supply "kit" houses of course, which come in set sizes/layouts, but in our experience, they do not come in with the cost saving they should, so a sensible design with a custom home TF company will not be exponentially more expensive, but has the potential to be much better suited for your needs. What I also liked with having our own architect is the additional safety of independent certification. I spoke with a few TF companies who do their engineering "in house", which has the benefit of small cost saving, but would worry me of what happens if the company goes under, or how do they handle the difficult over engineering conversations. Our chosen TF company has a completely external engineering firm work on all structural calculations, and it is their insurance on the line etc. The allows me to have an independent relationship with the engineering firm to ask my own questions etc. and personally gives me much more comfort, separation of church and state! My advice would be to work with an architect, be up front that the intended construction is TF, advise on budget etc. and work out the main design. Once that is complete, engage multiple TF companies to discuss their approach to structure, insulation, air tightness, working with other trades etc. and get your quotes from the companies you like.

Main point will be at server cabinet, centralized position for all data & AV cables. Loft is cold, with standard detail of airtight membrane on ceiling. I will have penetrations for external cameras, sensors, external lights, external power etc. Is my understanding incorrect that items like this would need to penetrate the airtight layer? House is TF build with an external block leaf, I assumed that an external light for example would drop down the cavity from the cold loft, with the cable routing through the airtight layer in the switch? I could be wrong but I think there are minimum bend radius requirements for cat 6/6a and these can be 25+mm, im assuming this be fine for 99% of locations but thought I better ask

Ha thanks, I have visions of dozens of cables coming in at certain points and nightmares on how to seal it all up ha! Im hoping that concerns about radius for data cables will be a non issue?

Hi all, Planning mode for new build and wondering about best practice for cable drops which may need to come through air tight layer. Naturally the intent is to keep these to a minimum but there will be some required for external cables, but was also wondering if there is radius issues for cat6/a which may force me to go above airtight layer? As a solution to drops coming through the layer, what is peoples preferred approach? Would it make sense to use some sort of semi rigid material, drill the appropriate size holes for cables, and use airtight paint on both faces of semi rigid material to create a seal? The this semi rigid material can be joined to membrane via tape?

Yeah fair point. In terms of working this back to ASHP sizing, is there big negative to having a much larger machine than needed? Assuming for heat loss at the average temp range is naturally a chunk smaller, so adding 125% to this number will be a chunk smaller than the -10 worst case heat loss * 125%. And how would I normally go about adding the energy needed for DHW into the overall heat loss? Also on buffer v no buffer - how did that look for you?

Ok good to know. For the pipe spacing, whats the cons (outside of cost to install) of having them closer to allow for lower flow temps? Does the principle of having more water in the floor allowing for more heat/cooling not fully translate?