G and J

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.

Excellent question, and the simple answer is I don’t yet know. Peeps have referred to using the sheathing as the airtight layer which makes sense until I get to the upstairs ceiling (I’m assuming a cold loft).

With the plasterboard, OSB and 11mm service void that will accommodate 25mm back boxes. There won’t be any pipes in them. (Though I will have to cut the hole in the OSB oversize so the back box can grip the plasterboard.) We're planning vertical cladding, hence the 40mm for counterbattens, but I don’t know how to do that on ubakus. I like the idea of Frametherm 32 @ 140mm to deaden sound, but not sure it’s worth 60mm off of the width of the house. Will investigate, thank you.

And in my experience many struggle for a myriad other reasons, often factors outside of their control, though I’d be interested to understand your data source on that one. I still think gas is likely to be the most sensible answer here.

You could have an instantaneous elector water heater, however I suspect there might be a bigger issue. I visit peeps in their homes, usually social housing. Some councils and housing associations have done what you are suggesting for option2. The result is cold houses, ASHPs going 24/7 in cold months, and heating bills unpaid due to their sheer gargantuan scale. I suspect that these organisations have simply fallen for the hype. These properties tend to be as retrospectively insulated as can be hoped, and they run happily and cheaply on a high flow temperature gas boiler. But they simply don’t suit low flow temps and they need lots of heat, which gas still is. Having replaced a gas combi less than 9 years old I think the world of gas is farcical. The carbon to produce a new boiler must outweigh the gas saved. But I strongly suspect irritating and high maintenance gas is still your best bet. Sorry. But top marks for wanting to do the right thing. (PS I am actually a fan of ASHPs, will be fitting one in our new build, but I’ve also been a landlord).

So, the answer is on site stick built. Took me a while but I got there. I've been looking at ubakus and that’s been rather illuminating, though it’s raised as many questions as it’s answered. I seek a wall build up that is circa 300mm thick, has a sensible u value, has the required fire resistance due to proximity of boundary being less than 1m. Experiments show using lots of PIR makes for a thin and insulative wall. Rockwool or cellulose increase u value quite a bit. I note the comments on here about PIR alternatives being better for sound attenuation, etc. and I thought long and hard about this but then I realised SIPs were PIR and reports appear to say that they make good houses. So, I've come up with a build up which appears to hit the mark but there is a warning on the drying reserve. Should I worry about that?

We bought our plot with outline permission in ‘91. It had gone through and the planners fought us on detailed every step. Most unpleasant. We clearly suffered because we tried hard to plan a build that looked dead right for the road/village, meaning we had little to concede to let the planners feel they had won. A few years later we bought some field behind us for extra garden. The planners were just as difficult. A few years after that we decided to extend. Put in our plans with much gritted teeth and trepidation, despite again working hard to design for looking right and not disadvantaging anyone else. We were in for a shock. The planners were lovely, could not have been more helpful. They seemed to recognise that we were trying to do the right thing and they responded accordingly. They even made suggestions that improved our design. A few years after that we had cause to apply in the Lake District for conversion of part of a garden to parking space. In a conservation area and the National park. Again they were lovely and helpful. Our experience this year was also good. In fairness we tried hard to design a house which would look right for the area so maybe many would view our plans as lacking ambition, rather staid perhaps, but the planner put the time into feeding back on our pre app, we followed the suggestions made so I can’t but view their service to us as professional and helpful.

Gym in man cave at bottom of garden. Long throw 3D projector in top kitchen cupboard projecting onto wall of snug area next to woodburner. 400m from swimming pool, so better for the environment to use that or indeed the river which is even closer. Still no snooker table though. And yes we use up spare space, we fill it with tat that we should not be keeping!

Given complete free range I’d have had a basement, but we didn’t actually need the space; I’d probably hardly ever use that beloved full sized snooker table, or the drop down scalextric track above it; it would probably badly bust our budget; and we’re building on very sandy soil v close to neighbours 100+ year old foundation free crumbling, timber frame houses. I can dream.

Actually, I think I should recuse myself for being unbelievably off topic. Sorry!

Have you watched Grand Designs : The street series (I think it’s called). What a wow of a set of disparate designs, but I love the idea of enabling self building to be accessible to more peeps.

I wonder if an MVHR design service offering independent advice would make money. Send in your plans, fill in a questionnaire, get back a list of requirements for each element, suggested vent locations, maybe a couple of suggested products to make searching easier to get into, etc. I’m currently swamped with offers of ‘free (but biased) advice’. Sigh.

Granted. I think in public buildings bold statements and innovative design can really lift an area. However I wonder how many of the more eye poking designs one sees on the tele are driven more by the ‘look at me’ ethic than the drive to improve the general look and feel of a locale. I want our house to be brilliant to live in, but I only need two people (plus a small dog) to love it. I’m quite happy if (in time) no one else notices. On the practical side I want it boringly cost effective to build and run. No alarms and no surprises……please.

Interesting idea. The non larch bits are either glass or render and I think the render will be ok on the same wall build up as the larch. (Dangerous thing, assumption!) We put a lot of thought into the look of our new pad and we’d be disappointed if we have to change it, plus, I’ll not be going back to the planners unless I have to. They’re lovely, helpful peeps but it slows everything down so much!