jack

Right, I've had a bit of time this morning to look more closely at this. It's actually the pressure relief valve that's failed. The 15 mm pipework from outlets of the PRV and the PTRV joins before the tundish (I assume that's acceptable?), so it isn't possible to tell which one's failed without disconnecting the pipework from the valve outlets. The failed valve is a Reliance 102-series 3.5 bar PRV. Apparently that's a "cold water only" valve. I think this was the valve originally supplied with the cylinder, but it's also possible I asked that it be replaced at the same time I had the TPRV replaced a few years back. Either way, it doesn't appear to be the correct valve for this application. Annoyingly, none of the Reliance valves designed for hot water systems come in a 3.5 bar variant. There's 107 series that is allegedly for "cold water use only", but it has a 110° max working temp. Shame I didn't realise what was going on yesterday or I could have given their technical department a call to see what the deal is there. On the assumption that I shouldn't increase to a 4 bar version, and a 3 bar version is too low given I'm already having issues with the 3.5 bar version, I may need to look elsewhere. Annoyingly, I can't see any obvious options with the same form factor, inlet fitting, and outlet fitting. If the Reliance 107 model mentioned above isn't suitable, it might be time to replace both valves with a different brand and adapt the outlet pipework to suit. Anyone have any thoughts?

I'd need to check, but definitely nothing like 90 deg. The issue is that the immersion is quite low on the tank (the upper immersion died and I've never gotten around to replacing it). By the time that lower region of the tank gets hot enough to turn off the immersion, there's been a lot of time for the water at the top of the tank to get very hot due to convection. That was my thinking when I mentioned a destratification pump.

Did it ~15 times aggressively but no luck. Any recommendations for an alternative brand? What's "big" in this context? It's a 22 L tank for a 250 L unvented cylinder. Minimum appears to be something like 4-5%, but rule of thumb is 10%, so it's above the minimum but a little short of the rule of thumb. The bladder on the original one died a few years ago, so I replaced it with a new one with a replaceable bladder. I'd ideally rather hang onto that than replace it again, although if it's important, I'm pretty sure I have the space for a larger one. Any brand you'd recommend?

Thanks Nick. I tried that a few times earlier, but could try it a few more times and see what happens. No HRC circuit. I just checked and the expansion vessel had no pressure. Bah! So likely that, possibly made worse by the immersion diverter. I need to put a reminder in to check the pressure in the expansion vessel more regularly.

The overtemperature/pressure valve on my pressurised DHW tank has started leaking (again). This is the model: My understanding it that it's a combined temp/pressure release valve (there's a separate 3.5 bar overpressure valve connected to the same tundish). I also remember reading that these types of valves have a tendency to leak after they've been triggered, or even after testing. This is the second time this one has failed. Last time, the bladder on the expansion vessel had failed without me realising, leading to higher than usual system pressure. However, I don't now whether that was the cause of the valve failure. Our static pressure is less than 3 bar, so I doubt the system has ever seen anything like 4.5 bar, even with the immersion diverter working. I wonder whether the immersion diverter is occasionally causing the temperature near the top of the tank to exceed the trigger temp for this valve? I recently installed the relay module on our Eddi immersion diverter, which will let me control the maximum temperature better. I also have a couple of spare pockets that I could use for something like a solar mixing pump, but I'd rather avoid any more complexity. So my questions: If you had to speculate, what do you think is the most likely source of failure? If it's likely to be temperature, are there brands of valve that are better at coping with being triggered and returning to closed without leaking? What is the most appropriate pressure for my expansion vessel? Anything else I should be thinking about? Thanks as always.

Welcome, you're in the right place.

The mods removed it because it was a breach of copyright.

I can't help you with recent costs, but we've lived in a house with MVHR for (unbelievably!) 10 years this Christmas. There's no way I'd ever consider building a house without it. There's something magical about having fresh, warm air throughout the house in winter. I don't really think about it any more until I encounter stuffy air in other peoples' houses in miserable winter weather. If you're even vaguely handy, it's one of the most straightforward things you can self-install, and you'll save a lot of money compared with having professionals do it. We installed everything ourselves except the drain and the power supply wiring. I did most of it myself over perhaps three easy days, with my wife helping me pull ducts through the easi-joists. There are arguments about the costs/benefits of running an MVHR system. You have a permament load of something like 10-40 W, depending on how big the unit is and what flow rate you run, which is a a few tens of quid a year in electricity. You need to regularly clean and occasionally replace filters, which could be another few tens of quid a year depending on brand, how often you replace them, whether you're willing to make your own from cheap filter media, etc. I'd be surprised if the reduced cost of heating due to the heat recovery offered by MVHR didn't save us more than the cost of its power consumption and filter maintenance. That said, it's a big upfront cost. If it last 10 years, it's something like £300-400 a year if you install it yourself. I doubt MVHR saves us anything like that amount on our heating bills. That said, I'm coming up to 10 years with the same unit. It's becoming apparent that the motors need new bearings, but otherwise the unit shows no sign of degradation. Hope that helps.

Have you listened to any of the Peter MacCormack podcast? Too many right-wingers and Reform nutters overall for or my liking, but otherwise some very interesting guests you're unlikely to encounter on many other shows.

I don't disagree with any of that, but it's a matter of personal preference which option is riskier or less pleasant to look at. My personal opinion is that I wouldn't mount one in the rooftop position being proposed. I'd be concerned about the noise impact in the bedrooms. I think it looks horrible on the roof (the drawing view from the garden places it against the wall - it needs to be moved a long way out to give a more accurate impression). And I think the risk of noise to the upstairs neighbour shouldn't be ignored. Yes it's 7m and a decent unit won't make a lot of noise, but there's brick wall behind the unit, a brick wall to the side, and the same on the neighbour's side of the fence, without a fence or any other ground-level obstacles to absorb and disperse sound. I could live with it being in the garden if that were the only alternative. Face the outlet down the garden. Screen the garden side parallel to the fence. That will leave the unit in a corridor without any obstructions to the front or rear, so there's no risk of recycling cold air.

100% this. It's trivial to hide an ASHP at ground level in a garden. The right shrub or an open screen a short distance from the unit will completely hide it.

If the plot you're looking at has full planning permission for that house, you might consider re-applying for permission for something that will be cheaper to build. Even with the cost of another architect, you could potentially end up saving money overall with a cheaper design. How long does the current planning permission have to go until it expires? If it's still got a fair bit of time to run, you could easily get permission to get something else built without risking the existing permission expiring. Just over a year from demolition to moving in.

MBC Timber Frame. Irish company, but I think they have a factory somewhere in south west UK. I used them over 10 years ago, but several on here have used them more recently. Copy and paste this term into Google search: "mbc site:buildhub.org.uk" You can use glass with lower transmission values (i.e., it's designed to let less light through). A better idea, imo, is to build in some sort of external shading. We have electrically operated external venetian blinds on some windows, which are very effective, but there are other options, like shade cloth. You can get them built into concealed boxes at the top of the windows, so they're more or less invisible when not in use. You might end up with some visible guide rails on very wide windows, but they're pretty discreet. Not the cheapest option, but then neither is installing the amount of glass you're planning! I don't have any photos of my house on BuildHub, but plenty of others have shared. The MBC search above should show some options.

+1 to all this. For reference, our house is almost exactly the same size as yours. We project-managed our build 10 years ago, but we had the benefit of using one provider for the foundations and timber frame. There were definitely some very stressful periods, mainly around poor (sometimes laughably so) workmanship and how that would be handled by the trade that did it. It's certainly doable, especially if you're well-organised and thick-skinned. We have similar amounts of glazing in our kitchen diner and it's one of my biggest regrets. Lots of glass can work okay if the space is big enough to allow furniture to be positioned well away from the glass. In our case, the space is something like 6 x 5.5 m and there's nowhere to put furniture without it being up against a window or sliding door. If I were doing it again, I'd get rid of most of the floor to ceiling windows and replace them with large ordinary windows on low walls (roughly table or back-of-sofa height). I'd also also replace the 5.5 m long slider with a pair of french doors with windows either side.

The ground beam above looks like reinforced concrete, with cages having 16 mm internal longitudinals (don't know the proper term for them) and 8 mm rings (ditto). That said, I can't visualise it either. Selexus, are you saying something like the cages for the ground beams sit higher than the lower level of mesh you want to tie in to, and you're therefore unable to easily lay out the UFH pipe because the tops of the cages are in the way? A couple of sections showing the relationship between the ground beams, the mesh, and the insulation would be very helpful. I have reinforcement beams in my raft, but the cages for those sit below the mesh, in channels formed in the insulation.

It isn't a democracy or a popularity contest. An objection totted out 20 times shouldn't(!) have any more effect than the same objection made once. And lots of pointless objections shouldn't(!) make any more difference to the outcome than none. Fingers crossed, but it sounds like you ought to be okay.

As I guess you know, things like cutting down unprotected trees are completely irrelevant and the planning officer will ignore them. Depending on your council's policy, give the number of objections, there's a decent chance the application could be called into the planning committee for approval. That's an entirely different can of worms.

I don't remember the details, but I asked a question on a plumbing or electrical forum many years ago. Can't remember the details, but it was something where there wasn't much real info online and I wanted to understand the issue before I got someone onsite to quote for the work. All I got was a load of aggressive wankers piled on saying I was cheap for not paying someone for the advice. I've never experienced anything quite like it.

(Context: I'm a moderator.) As you may have picked up if you've spent some time browsing BuildHub, the anti-monetisation vibe runs deep. The site has no ads, sponsorships, or subscription fees. Everything is run by unpaid volunteers. Some of our members, like @Gus Potter, are very much on board with - and defensive of! - that ethos. I personally think it's one of the reasons that experienced people like Gus, @nod, @craig, @Nickfromwales, and many others, are so willing to freely give their time to help other members. I spotted the YouTube reference when you first posted, but in the context of the rest of your post I personally didn't see a problem. In theory, it could become an issue if your channel unexpectedly got very successful and became monetised. Even then, you'd need to keep posting links to the channel for that to become a problem. I imagine you'd get a polite request at that point to stop posting about your channel, but as you say, given your intentions that's a pretty unlikely outcome. In any event, you seem to be self-builders in the fullest sense of the phrase. I would love to have had the time, energy, skills, and confidence to do something similar when we similarly replaced a 1950s bungalow 10 years ago.

Yes. I think the main issue here is that the roofer stopped the skirt when it reached the first lip, which is short and doesn't have an overhang. The skirt should have continued up higher into what looks like it might be the actual drip trim above the screw (see circled bit in my post above).

Agreed. Stick with EPDM, it's great stuff when used properly. That's likely true. As far as possible, membranes should always be designed to direct water over and/or away from junctions, rather than relying on sealants. In this case, it looks like the orange circled section of the extrusion is an overhang: If that's the case, then I suspect the EPDM should have been lapped over the channel with the screw in it and tucked up and bonded into that recess. Can you check the rooflight manufacturer's installation instructions? Don't worry too much about damage to the wood. It's been a dry summer for most of us, so the wood was probably well and truly dried out before the latest rain. A winter or two isn't likely to have caused permanent damage, especially given the seal was probably functional for a lot of that time. If you're at all handy, this is doable without professional help. In the short term, I'd get hold of some decent waterproof plastic and cover the roof light with it, leaving enough at the sides to hang down and cover the area with the leak. Tie it down and leave it like that for a few weeks for everything to dry out. In a couple of months' time, and ideally after a dry, hot couple of weeks, you can install the EPDM permanently. Your rooflight manufacturer can probably point you in the direction of how this should be done, or there are loads of Youtube instructional videos (or ask here when you're ready). Given that the leak is only at the top, you don't need to worry too much about anything other than making sure you get the top edge well tucked up and bonded into the recess, and that it extends down past the sloped part.

Your assumption isn't naive, that's exactly how summer bypass should work. Are you sure the function is enabled, and the mechanism is in working order?

I'd also recommend asking your question in one of the relevant sub forums (Other Heating Systems is probably best). Lots of members don't check the Introduce Yourself forum, plus any useful answers to your question will more easily be found by others with the same problem in the future.

Welcome Kevan. For a house with passive-class insulation and airtightness, it's feasible to do everything with direct electric heating. Have a look at @TerryE's posts on the topic. He uses cheap overnight power to do most of his house and water heating. While he pays more per kWh of delivered heat, he's saved the cost of an ASHP and associated plumbing/electrics.

Welcome! You could try posting your question over in the Ireland sub forum. I get the impression we don't have huge numbers of Irish members, but that's probably the best place to find Ireland-specific advice