G and J

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.

Oddly, if I swap the cement particle board for Osb it makes no difference. Boy am I out of my depth. I'm working hard to understand stuff so that we can make informed decisions when the architects pick things up, and I am learning lots, I think, but I feel a long way from having a good handle on all this. I do appreciate the time you are all putting in.

I suspect you may be misunderestimating (with a nod to George W) my capacity for fretting. I can fret about it all at once (it’s my version of multi tasking!). Being serious my thinking is that as a basic principle one sets the ideal as a goal. One gives ground unwillingly, and at times, one appears intransigent. But at the end of the process enough of the right info is gleaned then a good decision can be made. And yes quality comes top. Now all we need to do is identify what quality means. 🤷‍♂️

Yep, my u value gets worse with reducing centres. I only know this because I wrongly put 1200mm in to start with. Thankfully I’m used to feeling dumb and can smile about it. lol

Do you have further insulation within the frame?

I wonder if I’ve specified an inappropriate membrane on layer 9 then?

Also, I know I’m a pain but I worry - should I worry about “drying reserve”?

Now that is an interesting idea. So on top of the PIR/Rockwool (which totals 140mm I presume) what other insulation layer did you use? And is this inside wood cladding or a brick skin?

Wouldn’t rendering the brickwork, painting that to match the house render colour and paint the garage doors to match the house window colour link it for very little outlay?

I used to put built in ovens on a separate circuit till I was told not to bother by the sparky certifying a refurb that included full re wiring. That’ll be part of the planning I’ll do when I engage with a sparky. If needed it’ll be easy enough to run in at first fix. Re what else is on the downstairs ring, we’re pretty light on electric around the house, so not much in amperage terms. We will be having a quooker tap but from memory I think they’re lighter than my kettle.

Thank you for all that Ian - it’s access to knowledge like that that makes this place so fantastic. We may indeed thicken these up but I’ll leave that for now, partly because the area of our side walls dominate our situation and partly because I can only cope with so many hard sums at once lol. (Similarly the question of floor and loft insulation.) But it seems, even highly cynical, little old, round, bald fellas fall for the hype sometimes. Noted. Swapping the 140mm PIR for 140mm Rockwool increases the u value to 0.169, which I expect we could live with. Certainly if it made the house feel nicer - and it’s not worth giving up 3.5” of room space to get back to 0.129 in my initial build up. Oddly though, changing to Rockwool decreases the phase shift from 8.8hrs to 8.5hrs. Can’t pretend I understand what that means, so I probably should read up on phase shift.

Actually that’s a brilliant idea, well done. The 50mm PIR would keep the vapour barrier lovely and safe and snug, and stop it rattling (does that happen? I’m guessing it might if it was the airtight layer). I’ll pop it in ubakus and see if it objects. Still don’t know how to seal to the upstairs ceiling though. When I looked at rockwool generally it had half the R value of PIR, so in my case if I swap out PIR for frametherm my u value drops by circa 0.35. I’ve not compared the cost difference. Yet. (Or for that matter how much extra PIR is needed to compensate). I think the oven will run off the ring main. Won’t be running any cables horizontally except through the posi joists. The kitchen service void depth is the exception. That is on an outside wall, but the will have a larger service void to accommodate pipes. All other pipes will be in internal walls. I tend to fix kitchen units slightly further out to make life easy running drains and stuff behind the units, and I don’t mind a slightly larger worktop - I’m a messy cook and I like to cover acres with mess lol

Ah, sorry, I wasn’t clear. The OSB behind the plasterboard is just for stiffening and making the walls super solid and able to take light fixings everywhere. The sheathing on the outside of the frame is cement board, and that was the layer I was looking at.