saveasteading

I meant after a winter of the ground source pipes removing the therms. They look like this but with arms and legs: That needs an Ancient Greek letter. You mean deeper to the perimeter? It makes sense to have deeper insulation round the perimeter, and shallower to the middle, but that isn't happening. It's just going to be a less efficient area of the building, balanced by the centre of the slab being over-insulated. Perhaps PIR to full depth around the perimeter and 2 layers eps centrally is the pragmatic (and finicky) decision. It is intuitive rather than proven, but I'm confident I could write a page of 'proof' for the building inspector if it was necessary... but it isn't and will just be our decision.

We were discussing what to do with rooms that should be cool. Larder/ cupboard etc. and does the Utility room need to be warm? The current decision is to put the ufh pipes in anyway but not connect them, so we have full flexibility if (when) there is a revamp. I think the same logic can be applied to the whole house if ufh is a likely addition in future. If diy'ing the cost isn't great at this stage but simply wont be done at a future stage.

where, where, where please?

that's great to get real figures. Thanks. We have the constraint and advantage of an existing 175mm slab, and the insulation will be 200mm thick. Because of its HP/A being 0.2, we start with a U value of 0.35 with no insulation, with 100mm pir this becomes 0.21. For 200mm I haven't looked. It is from a very old manual with 'never throw this out', scrawled on it, because the 'uninsulated' graph is not often published. Interestingly one of the graphs shows that 25mm or 40mm are almost equally effective when hp/a reaches 0.15. Also that 60mm and 200mm converge at about 0.07. With beam and block, which I like in certain situations, the hp/a does not apply. I've just been reading a rather superficial article in 'Build-It' magazine. It happens to have an advert for ground-source facing it. It does mention the very high area of ground required for a surface system (3 times the house size) and the high cost of boreholes. But it doesn't mention that some ground is worse than unsuitable and that the pumping takes a lot of power. It says it never needs defrosting but I know that to be untrue for all cases.... or maybe the issue has ben sorted. In reality, surface systems are not heated by the ground, but by last year's sunshine. Slinky coils seem to have disappeared as they aren't mentioned. I wonder how much the temperature at 1m depth drops by the end of winter.

So far, simply using online published rates with no allowance for quantity.. celotex or other names all seem to be the same price as listed below, since when I've found cheaper but must check the spec. eps varies by vendor and many don't do it. please excuse that the Tab key doesn't work PIR thickness £/m2 £/m3 25 4 161 50mm 6 121 75 8.4 112 100 10.4 104 Now found approx £88/m3 120 12.7 106 EPS 25 2.16 86 50/75/100 all 86 unfaced pir 90-100 £8.51 £85/m3 as you will see, this bears out what some of you clever people have said about 100mm being the most competitive.

Apologies for an oversimplified discourse. I meant 'we' as the simple requirements of the regs for a new build, but with BH level of care and supervision. So it will satisfactorily airtight but with the resulting dribbles of air through the fabric, and more at fans and any vents. Good pun on manor/manner. Draughts was a deliberate over-statement. I meant airflow that isn't designed. Every time the front door is opened there will be a few m3 of air in or out, however well mvhr is designed. I don't suppose we will ever know the reality unless we here of a newbuild without MVHR that is failing on air quality, or someone builds 2 otherwise identical houses for comparison... and that won't happen. Plus cynical me says that there is an industry that sells mvhr, but not one that suggests not adopting it. Included in the decision are the weaving of ducts through the structure, the ease of maintenance , and the unknowns. Me? It remains debateable and I have plumped for 'not'.

I'm aware of that but reminders are no bad thing. I wonder how well a soft packaging eps would fare beneath 100mm or more of PIR and a grand piano on top. perhaps with a big enough dish under each wheel it would be ok. This is whimsical: I am not saving amazon packaging to try it.

Something else I didn't know. Seems to be a saw tooth but with a wavy profile to avoid sticking, and produces less dust. Between a saw and a knife. £22 The Bahco insulation saw has been specially developed for cutting various types of insulation material

Sorry I don't understand the question.

Best wishes everyone and esp thanks to the moderators.

Excellent graph thanks. May I ask it's origin? That's for an infinite area or based on some HP/A assumption? Theres a bit of a kink at 100mm ish thickness which seems wierd and that really underlines how worthwhile 100mm is. Severely diminishing returns after, I'd say, 200mm PIR. And no significant benefit after 0.3? ie a complete waste of resources.

I have awarded hearts to people I agree with.... which is contrary to good logic of listening to all views. But my prejudice, or is it exierience and intuition, is that mvhr is grossly over-rated. We build to control air leakage, then pressure test at high pressure with all fans and vents sealed. Then we remove the seals and allow draughts to flow freely from each wc and kitchen. Unless they have automatic shutters but they seem rare. Stuffiness can only raise from habitation, but then the fans are used which draw air from everywhere, to be replaced by whatever leakage there may be. Nobody suffocates. I've only had old draughty houses but the steading (family owned) has no mvhr and has no issues of stuffiness or condensation. I promise to report if that changes. In business I did no homes, but offices, nursing homes and school classrooms* would have the same issues..in all cases we agreed with the client to "chance it" without mvhr.... no problems reported ever. That's x 20 applicable projects at a guess. So I think I'm right. Still listening of course, but we don't intend to fit £20k on mvhr at the current project. * This seems extreme, with 30+ kids in a room. High ceilings help of course but window vents and door openings appear to suffice. Perhaps the teachers open windows sometimes.

Overlap is probably enough, but taping will guarantee it and keep it in place while insulating/screeding.

Cutting. I've just been discussing it with the guy likely to be doing it . He likes the latest and best tools. But for this he says a coarse cut handsaw and a big bench. He is up for the challenge of tiny waste figures if I predraw the best use by room.

Other people are saying that. And I've only ever done small amounts using a handsaw or slicing opposite faces. You've had a lorryload. Presumably not all laid as one area, so you've done it. So any recommendations? What tool? On the floor or a big bench? I think the gross wall perimeter is about 400m. Half of that to cut, x 2 layers. A lot of cutting. So that needs to be efficient and precise. If it's worth buying or hiring the best tool it would be good to know.

But perhaps they haven't. What was their brief?

Thanks all. What have I learned so far? Eps is much easier to handle and cut neatly. As a good fit is a strong benefit this looks like a real plus for it. The unfaced pir appears to be aimed at other uses than construction....keep it in mind for other purposes. I'm reminded that pir shrinks. Perhaps not in an underfloor situation. And it is a pain to cut. Gaps are inevitable, and the double layer, staggered joint, principle is pretty well essential. Factory cuts from one corner for the first layer, then reverse for the second. It's for minor benefit, but why not? AND as the division walls go in, it's apparent that there will be a lot of cutting-in. And that some spaces may be relatively consistent in level so tweaking to an optimum depth isn't so tricky ...perhaps each space will be insulated to the same thickness with any steps being at doors.. I may buy some 25mm eps to make this simple and best value. Waste. I hate waste in principle and in cost. The unused material and then the skip. Perhaps each room needs a plan.... offcuts get taken to where they will fit neatly. Fortunately our workers understand this and our timber waste so far is tiny. I will work it out. Guessing 2%.

10 year return would be my judgement, if that fits your advice. The "very best" implies value for money by my way of thinking. Eg passivhaus to me isn't the best, but a benchmark that is admirable but seldom the best thing to do measured by money or carbon.

It's been interesting to follow how strongly you are making this argument. I think you are wrong, and have even started sympathising with the other party. Reasonable care is judged by what skills they may be expected to have. In this case that would not apply to knowing all the building regs, esp as they apply to an existing property, and whether they are expected to write a long list of exclusions. But the credit card company may decide on some other logic. So I've no more to say.

Of course. But that 50 % is off a published list price for a few boards. My estimates will always assume expert buying. I'm assuming both, with the rest from waste control, optimising the design, detailing. And minimal skip cost....or have you a secret of using offcuts? 50 +20.% Almost free! Actually this is the one area where my estimate seems high. I'll report back when decisions are made...this isn't going in for about 8 weeks. Any more experience of the unfaced stuff from anyone? My instinct too. So prob the 150mm goes down as 2 x 75, on dpm, and following whatever dips and ridges. Then tape and dpm. The 'ponds' can be reassessed for 25mm boards or screed and I'm tending towards just screed it. PIR at about £80/m3 and add tape and labour. Screed material I'm only guessing at £150/m3???? Extra labour about 15 minutes. Ahhh. Best do a level survey.

I'd be surprised if an arbitrator or similar deemed a window installer should have these skills. Unless they advertise.. 'more than a window company' sort of thing. If you'd gone through a general contractor then this might be different, but you'd have paid a lot more.

Yes.

That's arranged. But on site so he can see the vast amount already from them and the future scope. And he can go away with some homework. Interesting about the stocks. The cost £/m3 seems to be in just 2 bands. 25mm to 50mm is dearer. Above that it is nearly identical whatever thickness as if the foil had no value. But the local merchant buying in a whole load of one size would get them a good price so I'll look I to that. Another benefit would be phased delivery. When we need it and less handling. And we can order just enough and a few more later if needed. I'm thinking 5% waste....any thoughts? Faffing is what I do. Efficient, holistic design, negligible waste but without stinting on quality. If I can make £1,000 by faffing I will do so. Or put another way: 20% saving on materials: imagine that on the whole project. The floor insulation value with 150mm of whatever on 150 concrete and HP/A of 0.1 gives us plenty and I'll take the cash now thanks.

I would say that tape or staples are a temporary fix but a sensible way to prrp and tidy for now. Is there a designed detail?

You might simply be able to push up the elbow to stop the leak. I'd repair the bigger holes ASAP. A pointing tool is a good investment and disguises my amateur work.