Conor

I'd go for a concrete raft.100mm EPS100 (or more) with DPM, 100mm concrete + mesh above. Can be power floated for a smooth finish. Very simple solution and will easily take the weight of a car.

If you have big concerns over airtightness and measures required to make a non-airtight construction air-tight, you could change to an inherently airtight method, e.g. ICF.

We're going with the Baskil "silver" which is basically a light grey with a blue tinge. We agree that dark grey / anthracite will be out of fashion in a few years.

@dnb sloes + Bramleys = sloe jelly. Bit of a family tradition over here and far tastier than redcurrant or cranberry jelly. A Christmas favourite. You do need several kilos of sloes tho...

Two units does make sense... But it is two installations, two extra wall penetrations (200mm RC concrete), two extra sets of filters to change. I'm hoping to get a large service void though the whole building, so will locate the MVHR in middle floor, then large ducts running vertically to each floor that will have its own manifold. Definitely more factors to think about.

And the new European NZEB - near zero carbon emission buildings.

Thanks @Dan F. The zehnder Q600 was top of my list as it technically meets the requirements... But will have to run at almost full power for 0.5ach. think I need to go a touch bigger. Thanks for the video... Really puts the size of the installation of such a big unit in to perspective!!

I have the large one from Screwfix... Titan I think. Great job. Tool function and also wet function. Not used the wet function yet.

Do you have any wall vents? E.g kitchen extractor? Pull the cowl off and you should be able to see in to the cavity. Ditto if you have a electric or gas meter box. My money is on poorly installed 100mm of mineral wool. You don't be able to do anything about it. If you are in luck, the cavity will be empty and you'll be able to pump with beads.

Anybody any experience of this or other Airflow products? It's definitely on the pricey side, but seems to be one of the few single units that's big enough for my house. Comes out marginally less than two smaller Zenhder units. I want to oversize the MVHR installation so it's not running hard all the time. (we are 320m2 and over three floors with high (2.7m) and vaulted ceilings (3.5m), and aiming for PH standards and want a unit with F7 filter, auto bypass, humidity control etc - any other suggestions welcomed!) https://www.epicair.co.uk/collections/heat-recovery-mev-units-view-all/products/airflow-dv245-r-adroit-heat-recovery-unit C

No comment on the costs, but that kitchen and utility layout isnt the best. E.g. look at the journey required to fill a saucepan and put it on the hob. Visit a kitchen designer before starting works.

150mm hollowcore slabs, 25mm insulation boards, UFH clipped to boards, 50mm liquid screed. I've a service void coming up the middle of the building. so the two loops (one for wetrooms, one for bedroom). Manifold etc will be in the basement. 5KW ASHP via a buffer tank. It's a passive house so the loops will be minimal. I'm only planning on three zones - basement, master bedroom (first floor) and all other areas (main living area on ground floor)

Cheers. That's who did the concrete for the basement slab funnily enough.

Who did you go with?

Missed a detail - 50mm PIR insulation under the rafters, then airtightness membrane, all held in by 50mm batons screwed through to the rafters. That plus the gaps between 215mm rafters filled with rockwool will give you a u value of around 0.1. no ventilation required and no risk of condensation. Who's advising you re insulation? Architect?

50mm batons on the underside of the rafters then plasterboard on top. Acts as a service void for electrics etc. We're also leaving a larger void at the peak by bringing batons across under the main ridge steel to give a 150mm service void for the MVHR ducting.

What's your targeted build U values, glazing and airtightness? We're building to passive standards but will have UFH in bathrooms and master bedroom only upstairs. Reason for UFH in the masterbedroom is that it has a fair bit of south facing glass and we want to be able to use the UFH loop for cooling in the summer. It costs buggerall to install so would be a missed opportunity. Post heater in MVHR will only delivery a very small amount of heat energy. Somebody on here said it's a max of 2kW.

I'm going for sand and cement screed, half the price of liquid. Issue with concrete is you'll need an awful lot of working to get it level and smooth enough for flooring, e.g. powerfloating. And getting it in to the house won't be easy. That'll soon eat away at any cost saving over screed.

Welcome. Very similar to our situation, we're just two and a bit years ahead of you. Have a read of my blog to get an idea of what is involved and how bloody long everything takes.

office is only one in that list. It could be argued that a large walk in wardrobe off a bedroom could be used as a habitable room.... e.g. we'll be using ours as the baby's room for a year or so. "A room used for dwelling purposes but which is not solely a kitchen, utility room, bathroom, cellar or sanitary accommodation."

I second this. Spoke to a roofer when trying to sell my old roof slates and he charges 70p labour only... But he's a one man band and in northern Ireland so understandably a bit cheaper than other parts of UK.

We're building using hollocore slabs and assumption has been we'd use concrete stairs as well for both basement and first floor. However, these are in the main contract as £1959 each.... And then we've to cover, ballustrade etc. Timber staircases seem to be a lot cheaper, and finishing seems to much easier. I'm worried that they won't feel "solid" and will eventually creak etc. Are concrete worth the extra for the convenience and durability? Or are modern timber staircases much better now? Main staircase will be carpeted, and one to basement will be what ever the hell leftovers we have to finish it!

For that sort of job you should be paying more like £250. It's a morning work for a surveyor with GPS unit. They are very useful to have re services. And if there are ever any disputes or queries, you've solid, verifiable measurements to refer to, e.g. of a neighbour says you've built 500mm too far forward, this is a doddle to check. If you've not surveyed it, and it's setout incorrectly, you could be in a world of pain that will cost a lot more than £250.

We have a 250mm floor build up in our basement. The current design is 150mm PIR and 100mm S&C screed. Can I go to 175mm insulation and 75mm screed, or will that be too "bouncy"? Google suggests 75mm or even 65mm is OK. It's 115m2, and I'd rather be paying for insulation than screed.... and it's only £9 more per sheet to go from 100mm + 50mm to 100mm + 75mm.

Edit: Total floor heating. The northern Ireland branch has been bought over and is now under heat.ie. they are advertising heat pump "services" so looks like they have gone down the supply and fit route as have no prices for just buying an ecodan. Disappointed, as they were way cheaper than other palces and a 40min drive for me! I remember that there was a branch in London, but when you Google it, nothing comes up. Back to the topic... I have been searching for other big name monblocks - LG therma, daikin etc. Seems to be a supply issue as I'm not seeing a whole load of choice.