Kelvin

The other thing to question and research is whether you need UFH upstairs. It’s a big expense. For example we don’t have any heating at all upstairs, apart from an oil filled rad in the bathroom, as do many others on here. We have wired for some electric panel heaters just in case I am wrong about the need for heating. However the house has been up for 9 months and the heating has only been installed for a few weeks and upstairs has been fine.

It really will. There are many people on here with ASHPs and they are perfectly fine. Our previous house was over 300m2 and wasn’t particularly well insulated or airtight and it was sufficiently warm with more than enough hot water. The house you are building is similar in size to the house we’ve built. It’s very well insulated and very airtight. I can heat the place with a couple of oil filled rads and have done up to the ASHP being installed. You’re being given duff information on ASHPs I’m afraid. You shouldn’t need to spend anywhere near what your quoting for heating and hot water. Do you have details on insulation and airtightness targets.

My water supply borehole is 145m deep and it alone cost £18,000 (paid by the original land owner)

Yes I’d slow right down here and do more research on this. Few people install borehole based GSHP and many renewables companies that did both now just do ASHP.

Ah. I’m about to run into this problem. We will have a glass balustrade at the top of the stairs. The stairs and glass supply have made locally and I really doubt he will have any calculations. I’ve not asked him yet though. If that’s so presumably I’d need an SE to calculate the loads?

I just used metal straps bent around them and screwed to the joists https://www.screwfix.com/p/ced-all-round-band-12mm-x-10m/18298?kpid=18298&cm_mmc=Google-_-Datafeed-_-Building and Doors?kpid=KINASEKPID&cm_mmc=Google-_-TOKEN1-_-TOKEN2&gad_source=1&gclid=EAIaIQobChMIitjMhoj0gwMV2JZQBh3GbQKBEAQYASABEgLXQfD_BwE&gclsrc=aw.ds

It looks either written in house or it’s the front end of a spreadsheet.

Keeping the outside noise, outside, is part of the overall equation. I overheard the plasterers chatting today about how quiet the house was. It was blowing a gale at the time.

Given those three options the PIR might offer the best U value but overall it won’t be the best performing. Of the three the 0.12 blown cellulose is the best option.

Yes long term you are likely to have problems. My house is clad in Scottish larch and the supplier specified 150mm between the bottom of the board and ground level to reduce rain splashing back up onto the boards. This also allows air to run up behind the cladding and out the top. Yours is sitting in the wet when it rains hard against the pavers. How does air circulate behind the cladding? As for the mould it’s likely just surface mould and will clean off. Has the cladding been treated with anything?

What the timber frame guy is saying doesn’t match what you’re seeing though. As ProDave says get up there with a hose. Pick one area to start with (the balcony would be my choice) and see what happens. You might need to do it over a few dry days though. How quickly does it start leaking after the wind driven rain starts? That might give you a clue as to how far it’s travelling before you see it.

If it’s coming in there why does the timber kit supplier suggest it might be the balcony? Which window has the window supplier re-sealed? Do you have any construction pictures? Yes a surveyor may well have such cameras. They are cheap enough to buy yourself if you wanted to have a go at investigating it. Around £30/£40 for a cheap borescope and screen.

Just to clarify did it leak with the previous window too or just this one? Finding someone is hard for these sorts of problems. A small camera into a suitable light fitting is a good approach (switch the power off) You could use a hose aimed at the likely areas one section at a time to see if you can see a path the water is following or narrow the problem down. Oftentimes a leak is somewhere else from where you spot the water. Some pictures of the windows, where the water is appearing and the balcony would help.

How deep will your screed be? I put ours in a large duct when we were doing the groundwork. Our hob is on the island along with the dishwasher and Quooker so we needed a suitable cable for the hob and a separate cable for power.

What is it that fails other than poor installation as above?

I was going to ask what the typical failure is.

Here’s a thread on the subject.

Exciting stuff. Well done in getting started. Out of interest why did you decide to install a rain water harvesting system?

Can you show us the exact wall build up?

You are based on the example you gave of two houses with differing U values using two entirely different insulation materials. PIR is very different from blown cellulose or a mineral fibre in the overall performance of the building but your only measure appears to be payback based on U value. Both buildings will perform very differently over the whole year especially in the summer. You might find the PIR building overheats more compared to the blown cellulose building and you need to spend £6000 fitting measures to deal with it.

Sure but budgets aren’t unlimited and there is definitely a line to drawn on the diminishing returns graph. However I do think the op is looking at the problem too one dimensionally. There’s a lot going on in a wall/ceiling/floor build up beyond U value.

You also need to consider decrement delay as already mentioned. Therefore it’s not just about U value and payback it’s about comfort both in the winter and summer. Building physics isn’t a one dimensional thing with everything acting in isolation. Therefore using your example twin brother if he builds using blown cellulose and you build using PIR his house will be more comfortable to live all year round.

Given that windows are typically something like 5 times worse than walls, thermal bridges, hard to make air tight etc we removed two windows from our North facing wall and made the others smaller. We only have three windows and a door on this elevation.

What are all the other elements of the house specification so air tightness target, type of windows, etc. When you get to this level of insulation air tightness becomes the thing to focus on if you are going for a very airtight house (and why wouldn’t you be) then ventilation becomes a crucial aspect.

It’s as much about different materials making up the structure so if there’s no acoustic insulation then adding some will help but it will only help not eliminate it. My build up has 100mm acoustic insulation, 15mm plasterboard everywhere with some double boarding, plastered rather than Ames taping, all joints/spaces sealed. It’s hard to tell yet what the acoustic transmission is like as we don’t have any doors fitted yet. There’s a lot of marketing about dense acoustic wool but there’s evidence that as long as it’s at least 10kg/m3 there’s not much improvement by going ever more dense. Thick plasterboard, double boarding, resilient bars, sealing gaps, etc is what you need to do. Here’s a good thread on the subject.