Iceverge

Nope, it's about 60% dearer than the readymix lorry. The cheapest way to get concrete is from the mixer truck..

Having used pumped insulation in the house attic and mineral wool batts in the garage I would happily say it's one of the best things I have done with the house. No itchy and scratchy show. I think @Gone West priced supafil when doing your house. Any idea of the cost installed? If you could find a machine to blow this behind a clear membrane you would have a cheap solution.

What's the UK price now? It's 4-5 years since I priced it here at €150/m3. Fitting mineral wool isn't particularly nice as jobs but it's very doable. Has anyone done blown mineral wool?

Tilt and turn baby. Tilt and turn!

Are you planning on stick building the frame? Have you considered blown insulation AKA cellulose. There's lots going for it.

Good layout, Nice to see a sensible square foot print. Personally I would pay the digger man another hour to level the site and forget about the step. It will make half the house unusable for anyone with a wheelchair or a pushchair.

Sliding sash looks pretty but is the draftiest window you can buy. I was in a new build of some neighbors, 0.15 walls floor and roof, compact foot print, wet plaster and plenty of airtight tape and MVHR. And sliding sash windows........ You could feel the cold breeze on the back of your neck sitting in the kitchen.

Any pictures? Is it mid bearing of the hollowcore slab or end?

You don't absolutely require MVHR, dMEV will give you adequate fresh air at less capex and slightly higher opex. However you'll have holes in the windows and you'll miss the chance to filter the incoming air for dust pollen etc. You will have more outdoor noise and drafts. I think your plan is a good one as you said. To throw a spanner in the works you could have an air driven heating system and allow the A2A units do everything and omit other central heating. There's drawback there too but it is a option.

I think this was on a forum here recently but I can't remember for who. 0.18W/m²K is just about achievable with a mineral wool 32 batt and 150mm cavity and some kind of light weight block inside. In reality I think a 200mm cavity and a cheaper 0.36 batt is better.

I assume you put battens inside the pir layer? 75*25? Did you have any issues with keeping them straight to hang the plasterboard?

100mm pir might be cheaper than 90mm. Worth a look.

Opening. I like to towel off ina cool breeze.

ubakus?

Mix up mortar 4:1 sand cement and trowel it into the chases where they're too deep. Maybe easiest done when the electrician is fitting conduit and push the conduit into the wet mortar. I know you're concerned but I wouldn't be too worried so long as everything is plumb.

I wouldn't worry about it. The calculator takes a snapshot of a temperature and assumes it stays -5 deg forever. Not very realistic unless you live in a valley somewhere that never gets any sun. Masonry is very tolerant of any damp. Masonry wall with mineral wool is somewhat vapour open so drying does occur both back into the house and out through the wall .

I could probably do any build method myself, masonry included. Unfortunately I would be long dead before I had finished. I think stick built has great advantages. 1. Speed 2. Many options to source materials locally 3. "Standard" TF constitution these days for mortgages and insurance etc. 4. No big deposit to find. 5. Easier airtightness + thermal bridging details. 6. No mega machines needed. Masonry is good but to make it work well you really need a simple box design, good masons and plasterers, a longer time scale and time for tricky airtightness and thermal bridging detailing. It's not impossible but for a high performance building (we did it) but it's more touble than it's worth. If you're will to accept something average it's fine. ICF and twin wall factory frames are excellent when done well but carry the risks of higher up front cost, waiting times, deposits, scarcity of extra materials if needed. Big cranes on site. Sometimes awkward insurance and mortgaging. Pick your poison.

That "mineral insulation panel" has a k value of 0.045W/mK. try it again with a "mineral wool 035" or "hk 33" for the EPS beads.

It depends on the U value you're after re the batts. They get a lot dearer once you get better than a k value of 0.035W/mK but I'm told they are easier to fit. We used EPS bonded beads. Works fine.

Correct . Thanks.

If you've got a reasonable head for heights and are willing to take your time and be careful you can do it yourself. Tree surgeons are charging around €1500/day near me for 2 men and a chipper. This was I think €175 per day. It's 12m reach but that's pretty much straight up so it's hard to chop anything higher than 9-10m without it falling near the base. For your situation an 18m machine would be ideal.. Keep the cuts reasonably small and you won't go too far wrong. Get tempted to reach out cut something big that you can't quite control and it'll bite you. Trees are dangerous, we all know that but don't be too swayed by the "can't do that mate" "need a pro mate", "Need to pay a weeks wages for a days work mate". If you're sensible and confident have a go yourself.

Mineral wool batts. Absolutely not put boards. They're next to impossible to install properly in the real world

Sadly @Gone West it was @ProDave who had the issues. Baumit silicone render over wood fiber I think I remember. That's assuming it's vapour driven moisture that's the issue. It's largely isn't in reality but rather the gaping holes left by the building process in the wall. I would be shy of rendering onto insulation in anything but a dry and stable climate. Ireland certainly isn't. I've seen another render failure over EPS near me recently. Constructed about 5 years ago. Meanwhile I've seen plenty of westerly facing sand and cement plaster over 60 years old on our farm with zero paint or maintenance and it seems to be holding on fine. For Timber frame especially I would like a cavity. Mineral wool or wood fiber being my preference for insulation external to the studs as they won't trap moisture. In any case I think for @Jess Shannon you'll make very little difference to the performance of an old building by getting caught in this rabbit hole. My suggestion of a 170mm wall, airtight layer and 50mm service cavity stands.

Yes. Didn't include it because I'm lazy.

I'll attract scorn here but I like a continuous layer of external insulation. It's keeps the studs and OSB sheathing warm and away from the elements. Provided you have adequate management of air movement through the structure (airtightness) and very good control over internal humidity levels the wall will quite happily dry to the inside provided you don't add any more low permability layers like internal vapour barriors. Unfortunately airtightness is rarely done well and internal humidity control relies on the long term occupants diligence so there have been numerous building failures, hence the caution urged above. In your case the U value of the extension is lightly to be neither here nor there in the grand scheme of things. Aim for Bregs with something robust, easily buildable and cheap. What really will make it feel more comfortable is good air sealing. Make sure this is done well. I would avoid PIR internally as half of it will end up in the skip as offcuts and you'll be searching for studs to hit while screwing through it. Also it's virtually completely vapour closed so any accidental moisture in the wall will struggle to dry either in or out. Far easier to bang up a few 2*2s with a nail gun as a service cavity and mineral wool is fast and cheap to install. I really like blown cellulose for TF but it may not be worth getting the man for a small area of an extension. Importantly everything above is off the shelf at every builders merchant in the country. Robust, buildable. Cheap.