JohnMo

I will possibly use screw piles on an out building in our wood, but not on a house that could be there for a century or more

Scottish larch, which I still have treat with a UV protection

Do a search on the internet for £100k house builds. That will give you an idea of spec. When upscaled to your house. £200k will give you modest well insulated house, but you will have to very careful on spec and make sure you spend the money wisely. What ever the architect says it will cost, take with a very large pinch of salt.

So if it's not windy, you don't have trickle vents - you don't have ventilation. Back to basic - open the windows, get a fan in the bathrooms. The average person looses between half to one litre of water per day just by breathing. If you don't ventilate you end up with damp house - you have a damp house. Your problem was being masked by open fireplaces.

When we doing our house I asked the architect about screw in piles and firmly told they would be expected to last the life of the building, so would be rejected by the council.

Here is ours.

Would it be be easier you use a sheet of toilet roll, place it near the mvhr inlet/outlet terminal, if stays in place its an extract, if it blown off it's a supply terminal. Cut and paste from passivhaus magazine, which make me wonder if you are just chasing your tail, with a dehumidifier, with the enthalpy heat exchanger? "Vaisey points out that on the other hand, if the relative humidity internally is too low, it can lead to dry skin, itchy eyes, and a dry nose and throat, creating a very uncomfortable environment for the occupants. It is suggested that the ideal level of relative humidity in a home is between 40% and 60%. The major sources of moisture inside the home are the occupants, cooking, showering and plants. When an MVHR system without an enthalpy heat exchanger is used, that moisture is lost to the outside — all that is transferred to the incoming air is heat. These systems also remove moisture from incoming air. However, the Flair 325 comes with an optional enthalpy heat exchanger. This works by allowing water vapour from the extracted internal air to transfer to the incoming air, raising the relative humidity. The quantity of moisture that is transferred depends on the relative humidity of the indoor and outdoor air and may run to about 60%. This is particularly useful with cold, dry alpine environments, with low levels of relative humidity. The enthalpy heat exchanger also recovers both thermal and latent energy from the extracted internal air, energy which would ordinarily have been lost to the atmosphere. “The average relative humidity in the UK is between lows of 70% and highs of 90% which is considered high, suggesting humidity recovery is not that big an issue in the UK,” Vaisey says." Would it be worth getting hold of a thermal camera, to see if you have local cold spots? Any water pipes in the wall close too or above where you have condensation? We had pressure tested our pipes, and had a drip every hour or so in service, took a while to find the issue.

Not sure of the legal side, but I would send in writing (email) stating that unless they get someone out in the next 48 hrs, you will appoint a 3rd party roofing specialist to rectify the issue and this will be back charged to the builder. But first put a drip tray to catch the water water.

So what the starting condition of your house?

Sounds very much like you have a ventilation issue. I take you sleep with the windows and vent strip closed? Without cross flow ventilation, your breath moisture is condensing on the cold areas around the windows. Would also guess the CO reading in your bedrooms are very high, not good for your health. Where you have mold clean off with a weak bleach solution. Your closed off fire places should have a ventilator grid in them, this can be internal or external. First things to do. Do your windows have vent strips, if so open them all, if you don't you will need to open the window slightly. You need extractors in your wet rooms, I would go with dMev, these are quite and run all the time, get ones with humidity detection so they boost only when needed, not every time you switch the light on or walk into the room. Or the other option would be dMVHR, but you need them installed in most room to be effective, quite like Prana units https://ecostream.org.uk/d-mvhr/ You can do all the above quite easily, mvhr will need you rip the house apart to install.

Once you less than 3 ACH you need to add additional ventilation I believe, our wood burner is ventilated directly through the wall so does not use house air. Which doesn't need additional ventilation. You can get a diagnosis air test for about £200, which will depressurise the house and can then go around the house and feel where you have leaks. Another way would be put on your extract fans and go around with a candle or similar and watch when the flame moves, by doors, windows, sockets etc. Make list go around an repair/ draft proof etc.

What about a ground array at the end of the garden? With optimisers on each panel to limit the effects of shading. PV with an immersion diverter, to use excess generated electric to make hot water. Battery storage expensive. Before any of the above look at insulation, draft and air leakage. That's the best money spent. Before you go to a heat pump, you need a house that can operate on low temperature heating, otherwise running costs will be high.

You don't wait til it's -6, that's the lowest temperature, not seeing why you would have an issue in summer. Quote from manual "The insulating properties of Durisol Wall Forms allow winter construction without additional heating or insulation sources being required. Durisol wall systems have been constructed in temperatures as low as 22 °F (- 6°C) without any complication." No

Wages - Myself, no wage, the 2nd guy £10 hour, for hours worked. £1500. Durisol is woodcrete, with PIR insulation -6 is from Durisol build manual.

Durisol walls cost breakdown only, doesn't include internal battons, parge coat or external stone slips or timber finish. Scaffold were mostly installed for the roof so not include in wall cost. £7k to Durisol Rebar £500 £1160 for cement pump x2 £1500 for wage 2k for concrete Total £1 2160. No idea what poleplates, ledger system are so obviously didn't use them. No support required for concrete pour other than ply on corners, but has been used a few times so no real cost. Airtightness was achieved with a concrete, lime, sand parge coat, which was around £400 in materials.

We don't seem to have any issues. My thought process was. You pour the concrete, it fills the space fully, as it drys the concrete shrinks, you heat the house, the concrete expands to fill the gap. Plus that what the architect and structural engineer had on the drawing. Our longest run of floor is about 13m.

The PIR upstand will be your expansion strip, you don't need a further expansion strip. You put polythene / DPM over the PIR only to stop a chemical reaction between the aluminium foil and the cement in the screed. I cut it flush with top of screed after the pour. The order my floor was build. Finished floor went in prior to the walls, on our build. DPM Structural steel re-enforced concrete slab. 200mm, in two layers of PIR, with 70mm upstand Thin black polythene. Staple UFH piping to PIR through poly sheet. Instead of screed, I have C34 fibre re-enforced concrete above the insulation/UFH pipes, 100mm thick.

Another option would Posi rafters. These are pre made in a factory, which cuts site time down, ours are approx 9m long. Our flat roofs were ready for boarding over in two days. Used the gaps for running mvhr etc We then under draw with 50mm Short battens, then counter battened with a further 50mm, to give a 350mm cavity, this was then spray foamed.

We used JHJ Joinery and JHJ Insulation, for our roof joinery and spray foam insulation. Based near Inverurie. Got most of my PIR (floor insulation) and Rockwool sound insulation from insulation hub (online).

Others can be used, for a passivhaus or otherwise. Ring around suppliers, look on internet, look on eBay. Do you need preheat? Preheat is for frost protection of the heat exchanger, I think you need to get down to -6 to -10 deg C for that to make any difference. We have not kicked in to protection mode yet because of frost, so not seeing the benefit with a UK climate.

Our house is long and not very deep, so the worst case for good u values, we achieved a floor u value of 0.09 (200mm of PIR). Had to do a lot of detailing on the sub walls below dpc, with thermolite blocks an loads of insulation, to get rid of thermal bridging, the structural engineer and architect introduced.

We put 200mm PIR in our floor. 100mm X 2 is what we did, with staggered joints. To be frank cutting 100mm was a pain, 200mm would be a really big pain. When cutting you want to eliminate any gaps to not let the heat escape through an easy route.

You are looking for continuity of insulation, which what I am seeing. A lot also depends on who you get to do the work, we had no other choice than strip foundations and a structural slab, which was then insulated and further slab of concrete on top.

Personally I would not want a heater under my bed, I get hot enough as it is. UFH heater works best as background heat, it runs at low temp for a long time, not really suited to bedrooms, where want it comfortable to get dressed and undressed, but cool while you are sleeping and same when you are out of the room. Our UFH takes about 6 to 8 hrs to react to a temp change, so we now run it on all the time, with single thermostat controlling the whole house except the bedroom where they set at 17 deg. I would install electric UFH in the bathroom, have it hot when you need it off all other times, plus install an electric towel rail so you dry towels in the summer. Some people go under stud walls, I avoided it, to limit the " I just drilled a little deep and there is water coming up" from a contractor.

We commissioned ours before the floor covering were down, but now (3 months later) have to replace all the filters, which I knew about and a cost I was planning for. But also ensure you install filters in all extract points not just in the mvhr unit. Until the floor covering, the paint etc is in place there will be dust.