zzPaulzz

They designed our lighting layout and supplied the fittings. I started doing it myself but It proved to be complicated with the vaulted ceilings etc, and I was holding up first fix.

Ah, no, not them. This was the chap who did my insulation under contract from MBC.

I guess you mean Norwich Architectural Lighting? We did.

I have blue Tescon patches on the inside of my SmartPly Airtight panels and roof membrane where holes were made to pump the cellulose

All done apart from driveway gates, a bit of landscaping and some more solar panels on the ground. Moved in in April, 12 month after breaking ground but only because work pressure forced me to get a project manager in, so less of the self-build sadly.

Yep. Currently have large expanses of glass on both, but should be reasonably shaded in the summer. Won't really know until we get to live in the place, but hopefully soon

My PHPP is using "GB0013a-Hemsby"

I agree, PHPP is a model, not a crystal ball. It remains the best tool I could find to test the combined impact of all the fabric choices I made. I have very little south-facing glazing so solar gain is a smaller problem than it might be. My last house was similar and in the extreme heat of last year it stayed bearable inside, but only if I vented the house at night and buttoned it up in the day.

Haha. Maybe, but not expecting to need AC. If the PHPP calcs are correct then the house will only exceed 25°C for a few days a year.

My Zehnder Q350 can be configured to turn on the supply or extract, or both (normal balanced mode). I wonder if I'll get a good cooling result if I use Home Assistant at dusk to switch the MVHR to supply only, chill the slab and also open all the Velux. Then, before dawn close the windows and switch the MVHR to balanced mode with summer bypass. Thoughts?

Yep, not counting on it.

That's my plan for the days where the PHPP predicts overheating: crack open the electric velux windows to create some passive stack cooling.

Nope. Hoping the MVHR will help. Otherwise I’ll be opening the three roof lights for passive cooling at night.

Yep, I heard that. Where do you think I need to watch for dew forming? Pipes above the slab, or on the floor tiles?

My house is near-passive (0.12 walls, 0.1 ceilings. 0.08 slab, MVHR, triple glazed but sub-optimal solar gain). I've installed UFH in the ground floor slab but the 4kW ASHP is not on yet. Installing electric UFH mats and electric towel rads in bathrooms, otherwise nothing else. I can run the ASHP in cooling mode if summer heat is a problem. Had very high humidity after plastering (85% @ 12ºC) so brought in some dehumidifiers running 24x7 and a 3kW fan heater running for 6 hours a day to get the house up to 18ºC and 55% RH. Turning on the MVHR helped. I'm very hopeful now that I'm more than covered for my space heating needs.