G and J

So if I have an ASHP and I want to benefit from a warranty I have no choice. Sod. At the start of this thread I asked “Am I missing something glaringly b obvious…” I now know the answer to that one lol

When I bath (I am a hippo!) I leave little hot water. When J showers (she very definitely is not a hippo!) it leaves loads of hot water, so I’m designing around my bad habits lol

Ummm, so do all heat pumps require unvented? In my infinite stupidity I see no reason why they would.

Noted. Thank you.

May I ask why that rather than other systems?

Sorry JohnMo, I don’t understand what that means. We are thinking along the same lines, for the same reason we’ve put an electric towel rail in our en-suite so it’s warm when the heating isn’t needed. J loves warm, soft towels. Do either of you have a very eco-unfriendly bath habit? I know I do.

Just googled it - so it’s the same system one uses for wet underfloor heating it appears. Interesting economy of scale if using the same tools and pipe for both….

Sorry to be dumb but presumably a Thermal Store is different in some way to a hot water cylinder?

So you are effectively saying that UV is dead simple to maintain?

Interesting how similar our thinking is…. 1. A 5kW monoblock ASHP. TICK! 2. A 300l ASHP UVC. I was thinking 300l ish, but vented. I believe they exist. 3. Hep20 push fit plumbing with the hot manifold preheated by convection above the cylinder. Pipes run in a radial fashion. 15mm for the baths, showers, and kitchen sink and 10mm for everything else. I’ve plumbed with Hep20 successfully before, and I’m happy to do so again - my plan is to work it so that no joints are buried - will be mostly radial. Pipe size perhaps depends on whether I go vented. 3. In slab wet UFH in a single zone downstairs. TICK 4. Electric UFH in all bathrooms. Ah, we’re thinking wet UFH in upstairs bathrooms. 5. Floor drains with waterless traps in every wet room for leak protection. Haven’t thought about this but yet.

Back in ‘91 I plumbed our house. Oil boiler in garage, hot water cylinder in airing cupboard, steel rads in most rooms, two tanks (little and large) in the loft. Showers have about 6’ head, and are fed by 22mm both hot and cold the cold being direct from loft tank to balance the pressures. They still work well, so assuming Aqualisa make similar I’ll be replicating as yes, I want to go vented. That way I can install and maintain, I’ve space in the right place in me loft and I do like simple. I (or someone) will be putting in an ASHP which will run the UFH and DHW. I might go a bit space age and fit a stirry up pump thingy, as I think that effectively increases the hot water capacity of a system, I’ll look into that in due course. One thing I’d improve (meaning reduce) if I could on my current system is the amount of water drawn to get hot water to each bathroom. I foolishly did some of the DHW distribution in 22mm copper and the rest in 15mm. Another thing I would improve is having no buried joints. I have dozens of solder joints buried in floors, etc. so the idea of using manifolds and continuous plastic pipes so every joint remains accessible appeals. I’ve read just about all I could find on here re vented vs unvented and I remain convinced that I like vented. I note however that the world quietly went unvented over the last three decades. First question. Am I missing something glaringly b obvious in concluding vented is ok for my new house?

I built this housey on sauuuuuuu saaaage rollllllllls… But I’m guessing I need a good rodent barrier. (With apologies to LadBaby!) I'm really appreciative of all the inputs guys, I think I need to reflect and revisit this soon.

So you adjust the voltage to hit the target pressure, but how do you measure the flow rate?

I’m going to have a good read through your blog, so if it’s in there that’s great. But if not headlines would help so thank you.

Some things you can’t put a price on. (Said the man who uses his Greggs app for his loyalty freebies A LOT! I ). 😉

No but they make yummy Mexican style vegan bake thingys. And their booby buns are vegan too, but not marked as such, I think because it would adversely affect sales. Obviously this is on topic as keeping me warm will reduce my bun and savoury bake requirements and so save money long term and help me live longer to see the payback.

That’s more than good enough for me. I’m sure you are a sensible person, but I trust your dog’s senses completely. Noted, though I’d rather not have to rely on such things. It also stops warm, wet(ish) air from inside getting to a cold surface inside the wall which would risk condensation, so that is a very good thing. May I ask what your wall airtight strategy is?

Have you been snooping in my car?

That looks soooo far beyond me, but thank you. I was planning on my PhD being on The Statistical Variation of Tastiness of Greggs Vegan Sausage Rolls over time of day. Obviously significant field research needed. That’s more my level.

I am drawn towards a composite rockwool and PIR solution like Thorfun listed. 140mm rockwool stuffed in frame (easy to do, improves sound performance) thence a skin of PIR to deliver thermal insulation, and that’s where the trade off between wall thickness and u value hit. It is likely to deliver a poorer u value than we could have but that’s ok, once I’ve looked at the other elements I can analyse the balance and we can make informed choices. And I would have stopped there and moved on to the next element had ubakus not had a little red triangle. However, I think there is a possible flaw in its analysis. If I have a build up such as: then I get no warning triangle on drying reserve. However, if I add a layer of PIR on the outside of the vapour barrier I get: So, the addition of the PIR layer is the only addition. It is next to and outside of the barrier which should let nothing through. So if PIR does not absorb, store or transmit water as has been stated then it’s almost like it’s a 50.5mm thick vapour barrier - so why should it change whatever the drying reserve is? If PIR was able to absorb, store and transmit water then it would be no different to the rockwool that it is next to. Either ubakus has a quirk or there’s something fundamental that I’m failing to understand.

Definitely, though I’m still effectively analysing the options. Thoroughly agree that there is a danger of being diverted by detail, and I’ve done that calculation and found similar results. It’s kinda scary that it appears from my rule of thumb calcs that insulation much above building regs does not show a financial payback. U value is a predictable metric, so it’s an easy one to focus on, as is build cost. So as I look at each possible build up I naturally calculate the u value and yes, I’ve got build cost in the back of my mind (otherwise I’d use aerogel!) but because I have no easy accessible metrics for sound transmittance and ‘comfort feel’ I’m effectively having to glean what info I can from this and other posts.

Which is kind of understandable, it is only like a plumber always using the same make of boiler through familiarity, it makes for a working solution but with the combined knowledge on here I’m going for better than that. So I’m going for a modified version of your suggestion, I’m doing my research and then working with the architect for the best overall solution for us. I will be using The Spreadsheet too, but I want to work through each element individually first.

@Thorfun And how does your house feel to live in? Do you notice noises from outside?

So if we work hard on being airtight then it sounds like a fully PIR solution should yield a nice place to live. It’s not a noisy environment, and we are close flanked both sides by neighbours with the narrow alleyways in between very rarely used (except by me carting loads of greenery from front to back for tip runs).

Soooo, I think I’m at a point where I do need to wait for my architect input. I have various wall build ups of various thicknesses, none of which I can yet be confident about moisture control. I don’t know that there’s a problem with them, but I need to know there won’t be. I have a wall build up made of lots of PIR which fits my desired thickness and has a good u value, but opinions have been shared about the acoustic properties of that design (and how nice a house built such will be to live in). Alternative insulation yields designs which are either a bit thicker, have a lower u value of both. I like the 140mm rockwool batts idea in terms of acoustic attenuation but I don’t yet know if we can trade off the insulation level with other elements. The idea of some PIR part filling the frame, then rockwool filling the rest of the frame, then another layer of PIR sounds like a good compromise but it makes a PIR/rockwool/PIR sandwich and that sounds like a recipe for trapped moisture, unless PIR will allow moisture through - maybe the non foiled stuff will. For me, having built a blockwork house, concerns about wall solidity play straight to my anxieties, so if anyone has a timber clad, PIR insulated house I’d be very grateful for you sharing your thoughts on my concerns and whether they are reasonable. On the brightside, yesterday I bought a shiny new tailored boiler suit. Tailored meaning I cut 8’ off of the legs (I’m short and round) using pinking shears (it is pride week). So I may not have a wall design yet but I do now look like a navy blue Tinky Winky.