Nickfromwales

Ok, so why such a "tall" building? Is this destined to have an apex roof? Why not go for a flat roof and avoid the height. I don't have any other suggestion other than "don't continue with this plan, and work a new plan to have this above ground at soleplate level, doing away with a pumped drainage. There are so many red flags here i am losing count! Please give us the whole story so we can get you the best replies.

14 - timber lining? I wouldn't want wood there! Why isn't that cement board also?

This is the correct route, but then you must NOT use the paint as the layers will need to breathe. FYI, putting the AT paint on the floor will be utterly useless and do diddly squat for AT. The AT needs to come past this layer in the garage, and then that membrane gets taped to that layer. Look at AT as a perfect cube, will all lines, corners etc in contact with one another, as anything less will gives terrible results for a lot of time and money spent. If you can have the cylinder anywhere else, then do so, the garage should be the absolute last option as the heat loss over winter will be significant (albeit a cost / compromise that you may be willing to accept to gain space inside the house). Go way above B Regs levels of insulation in the ceiling of the garage, as this will pay huge dividends over time, that's because the garage will be the coldest draughtiest area in the building so will attract heat loss. You may also need an airtight door separating the garage from the house, or do away with that altogether, IF you want to get a great AT score? You buy insulation once, it lasts a lifetime, but gas and electricity will keep costing you for your lifetime, a cost you need to mitigate against with every effort. The same can be said about the insulation everywhere else, as UK B Regs offers the poorest house you can legally build, and is an utterly dire standard on a very, very good day (and that is the most you can expect if / when the work is executed meticulously by a builder with a conscience which doesn't happen with high frequency btw).

Well, they celebrated building their 100th home in the UK in 2023, but that is a tiny percentage. My marketing team discovered that there are somewhere between 15,000 to 18,000 UK self builds per annum in the UK (domestic 1-offs) as an 'average' (albeit these were quite difficult statistics to accurately ascertain) so that's the way I gauge their 'presence'. Might I ask what the attraction to this particular company is? I am indifferent btw, just more curious than anything. What size home are you building?

Which just goes to show how under-qualified these bodies are to provide a global summary of an entire property vs just adding the number of ticks in particular boxes and then down-grading you like Neanderthals.

Are you gluttons for punishment? Why on earth (or clay lol) are you going down so low with an outbuilding??? Is this to get the ridge height down to appease permitted development or planning rues? Sounds like you are making ridiculously expensive and unnecessary rods for your backs here, sorry. Having a garden room that needs a sump pump is insane (and my ICF guy is Canadian so I know they do these types of things without batting an eyelid) so I think you need to have a serious sense-check here before going any further.

So when exactly did they put this through your door?

The issue is about zone control then, as the flow temp may be "OK". How do you propose to control the heat input and floor temp? Do you have UFH anywhere else in the dwelling?

Most ASHP's have a 7 year warranty, from the few I've been associated with, and that's even from the likes of Stiebel Eltron who offer 5 iirc. Lifespan / longevity is found (promoted) by good design and sizing the unit so that it can live a relaxed and long(er) life.

You may be 'over-worrying' here tbh. Permeability isn't the issue here, it is movement. If you allow 2mm per day you'll be A OK, and if this is primed properly and a good, conscientious tiler employed vs 'the builders mate', then you have no reason why this shouldn't be a successful undertaking. Excellent prep work can be wasted on a shite tiler and I've seen them all. FYI, I've been tiling high-end projects for 25+ years. FWIW, I would have given you a bollocking for removing the battens, as that will likely do more harm than good. The battens will offer some fixed mechanical bonding, to both the screed and the Ditra + adhesive, and will likely be the backbone so they defo need to stay.

Bum steer, sorry. Do NOT fit steel plates, you just prime the battens and fill up with tile adhesive for the Ditra to bed into. I'd recommend something like (a little more expensive but very good) Bal Flex One tile adhesive, LINK, as this offers even further decoupling by itself.

Hi. Are you improving and upgrading the existing bits to match the performance of the new SIPS stuff from Potton? I assume they've comprehensively commented on this already? That assumed, MVHR will be mandated and then a full heat loss (and overheat) analysis can be done on desktop to allow you to tender to any decent A/C company. Best to get the horse and the cart in check, and then you can provide vital information to these 3rd parties YOURSELF, vs expecting them to do this heavy lifting. The best due diligence is the one(s) you do yourself. Potton should have already given you ACH targets and U-values etc for their 'bits'? Just need to add the existing part and you're off to the races. You could have elaborated here just a little bit lol...... No, it wont. Unless these are 2 separate and non cojoined items then they will always be as one; they'll be the same heated and airtight envelope, so the weak one will bring down the stronger and not vice versa. Who's advising you on your M&E side, as this sounds like you're getting less than great information upon which to be making these decisions?

Yup, what he said 👆

Yup. @HandyAndy, you cannot connect to the underground pipe with that boss strap. Completely against b regs. You need to expose more, get a 110mm Y branch (not a T branch) and then extend a new piece of 110mm pipe to a gulley pot underneath where the shower pipe exits the wall (as close as you can get it). You need to approach your building control person BEFORE going any further.

I’d say you should look for min 16a or a comfortable 20a continuous load device, 13a is still cutting it a bit fine imho. Shelly’s can do this and seem well suited to this application. It’ll need a separate 16a or 20a supply for each ‘channel’ / immersion, so don’t take both feeds off one breaker (so you’ll need 2 positions in the CU to do this properly too).

13a peak, 10a constant. Resistive heating can suck full power for sustained periods, and everything warms up really quickly. Fuses will run ‘molten’ where the metal is borderline melting point, and the heat then spreads and it goes terminal. Use a timer to fire a pair of contactors, and make sure the 2 immersions are fed independently, and things will be less ‘toasted’ looking

Contactor all day long matey. The plug is rated 10a continuous…… you dodged a bullet there 🙁

Welcome aboard. 😎👍

No need for thanks, and glad you see this feedback as constructive In a nutshell, your natural infiltration from having a modern building regs build (apologies, but 🤢🤮) will almost definitely be bean-counted by design, work executed at the minimum deliverable standard (you hope), and holes / gaps etc all left to blow a hoolie through. When the natural infiltration rate hugely exceeds the MVHR flow rate (which is tiny in normal operation in an airtight dwelling) you’re stuffed. You’ll be sucking in ice cold air from outside all winter (which will be Baltic during the arse of winter btw) and pumping it into the bedrooms and living spaces. It’s a fact that this will significantly increase your heating demand, as there will be (I fear) the square root of feck all heat recovery with such an install. I talk more people out of these types of retrofits than into them, after, of course, explaining to them WHY. Most salespeople fail to state the cons, naturally, as they need to pay the mortgage etc. 🫤

At least you took it like a man lol.

How quickly can you walk through an empty train, vs a packed one? A bit like, "What is the sound of one hand clapping" to the untrained ear I'm afraid.

Ah, Christ on 2 bikes. I just read your intro....... MVHR into a house which isn't airtight? I don't have much more to say that won't make you look like you've just peeled a very big bag of onions, sorry.

Noise? There shouldn't be any 'noise' if the unit is fitted according to the application. I oversize if there is any risk of the client requiring "graveyard quiet" and not had a complaint yet (quite the opposite in fact). Acoustic dampening is achieved via attenuators, and vibration / transmission of, is dealt with by never (having to be) running the unit at near full speed. I use strap band and (sorry @Conor) hate the clip bases and monster zip-tie approach, and I've banded to the upper P5 deck (Egger board), to the posi-joists, and everything in-between, and I have not had an issue in the last 8+ years of installing, or being associated with the design & installation of, an MVHR arrangement. MVHR does not, nor should it, make 'noise'. If it does, something has gone very wrong with your design process.

"Hey Siri, dial gate", and the magic happens. You old fart lol.

It's very simple. In the winter when you turn the heating on, for the 3-4 months of the year that you will be heavily reliant on space heating (in the majority of homes) you'll be at <25% or less PV production, so if you have a 4kWp array you'll not be getting even a reliable 1kW of PV production (when it's one of the sunnier days in the heating season ). That <1kW will be sucked up by the house, so there's "goodbye" to any dreams of diverting excess ANYWHERE as you won't have any. If, for eg, you have space & budget for an 11-12kWp array (maxed out on 3ph, for eg) and it's all South facing, then maybe you'd still get DHW from excess. But even with that size array, during the heating season, you'll be very lucky to get a reliable 2-3kW return from the array. Costs of PV then go beyond the costs of just feeding cheap, grid electricity into the ASHP in the 1st place, for dumping steady low grade heat into a big thick insulated raft slab as a 'storage heater'. Get the calculator out, remove the rose-tinted goggles, and the evidence will support itself.