Conor

Bear in mind that as bats are a protected species, this is more than getting around planning restrictions. I would not do anything at all (even ground works) until you've had the OK from a bat ecologist. You've been made aware of the bats, so any activities that result in their disruption or harm (e.g. construction noise/vibration or dust) would likely be looked at very harshly. We wanted to do works on a barn door (in a timber water treatment plant) to get electric cables through for temporary pumps, and the solution our ecologist made us follow was the careful removal of the doors, move them away from the building so we could then drill out holes for the temporary cables and hoses. The noise/vibration could cause the bats to flee their roosts.

It's encased in 200mm of reinforced concrete, it's not going anywhere.

Open fires have a net cooling effect as they draw out more heat energy (the warm air) than they radiate out (don't know about back boilers). They have no place in our world anymore. There's a house (about 150m²) that's just got fpp across the road from us and they have three open fires and a wood fired pizza oven in their house design... It'll either be freezing or unbearably warm 😅. Not sure how they'll pass their air tightness test. And your MVHR won't work properly at all, esp when it's windy or the fire is lit. So you'll be better off with trickle vents and bathroom extractors. And you'll also need a wall vent in the rooms where the fires are, so even draughtier. I think a room sealed stove is the obvious compromise.... You can always fire the door open for effect when the mood takes you. Sorry to be negative, but that's the reality.

Lhs line is the main vent stack with basement toilet connecting to it, them to the right we have the basin and shower, and finally utility sink / DW in next room. We originally had the toilet in same line as main soil stack from above, but BC asked us to put it in with basin and shower for some reason as it obviously meant the toilet line would be more than 6m unvented.

Do you ever think you'll sell the house? Of yes, then stick in a small ASHP as you'll have have difficulties selling a house without central heating. I think we're a decade or two away from unheated passive houses being widely understood and accepted.

Same when we did our extension. Had a spark to 90%, then I added some eternal sockets and extended a loop to my shed. BCO didn't care. I was worried I wasn't going to get signed off.

We did a Lot for the whole structure (founds, walls, tanking, floors, steels, roof), went out to three builders that I had researched that do ICF and concrete works etc. Went for the cheapest lol

How deep are your roof trusses? You need to leave a decent air gap. In our build, we're doing 100mm celotex between 150mm rafters, air tightness membrane under rafters, another 50mm celotex, 25mm service void made with batons, then plasterboard. Issue with spray insulation is consistency... Hard to get even coverage and hears of some horror stories.

My new Reolink is exactly the same. A single droplet of rain at nighttime or a passing car headlight sets it off, even with sensitivity set to minimum. The other one I have is a slightly different model and works absolutely perfectly.

If you have an ASHP, can be really effective at cooling the floor slab. Few here have done it and seems really effective. Alternative is an AC unit in a large space in the house (e.g. top of stairwell) and allow convection to distribute the cooling.

Is it going to be a free standing wall? You can just resin in wall ties at either end to the existing walls. Every third or fourth course. If it's just against an existing wall, just build it against it with a bit of a gap for mortar

That's a bit below average. When we did pressure management for UU, we'd set the PRVs to deliver a min of 20-25m head (2.2bar ish) to the highest elevation property in the zone. The minimum set by the regulator is 12m (1.5bar ish). What time of day did you test? There will be a big difference between middle of the night and peak demand times.... I.e. lowest when you want that shower!

@dpmiller RTU? Prices competitive?

Think you'll be ok unless somebody complains. Depends on your neighbours and your local planning authority. A developer near us decided to stick on another metre or so to half a dozen houses to get an extra floor in (2.5 story houses instead of 2) initiating a cascade of complaints form locals as they obviously blocked views over Lough for loads of people... Put in a retrospective application and surprise surprise were granted almost immediately. Get your brown envelope loaded up.

It will mess with balance. But only for the time the extractor is on. Unless you do a LOT of cooking, that will only be a few mins a day typically. Wouldn't worry too much.