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Discuss..... Background: 15m3 mono pitched roof rear extension, UFH in slab on 200 PIR, 150 cavity, full fill. Triple glazed 1200 wide window one end, 1800 wide sliding door other end. I'm aware that we need some ventilation under Approved Document L, I'm trying to convince the wife that we need dMVHR in this space. She doesn't like the windows open (at all, it would seem)... She hates drafts and feels the cold.

Multi head mini-split, job done.... Cheap as chips, easily controllable, easy to fit.

This is running without the extension line set. Just the pipework from the indoor unit, straightened out a bit more, then with the ends re-flared. It doesn’t complain about the reduced length. All mini splits have a reservoir anyway to accommodate variations in line set length.

Cheers…. That’ll work well as I’ve got a couple of shorter lengths of continal 16mm left over from another job

I’ve got a 125mm slab going down next week in my extension, on 200 of pir. It’s not large, just 2.8x5…. Do I need to bother designing this in loopcad or can I just bang down some pipe on 150 centres and call it done? Plan is to run it off an ashp.

Boilers and rads in the bin, air-to-air mini splits for everyone, direct unvented cylinder…. Cheap, easily turn-off-and-on-able, reliable.

They can... they will...

In case you were wondering, yes, this came from appliances direct. It was about £550 or something. I didn't use the supplied extension set, I simply re-flared the ends of the indoor unit pipework. Pressure tested it to 100psi with pure argon (I'm a welder, I have it in stock) then vacuumed down for 20 mins. Float the low-side gauge up to 20psi then remove the pump+adapter from the service port. Then crack the valves and back seat them. Easy when you watch enough youtube.

Yep, having just installed one last night, I can't believe how these things aren't more popular - amazing products. Instant heat, instant cool, easy to install.

I would 100% go for A2A - easy, instant on/off heat that costs naff all to run, and naff all to install. Perfect for a holiday let.

I just finished installing this last night, at my off-grid place in Dorset. This is to provide shoulder season heating (and possibly all winter heating) in a room that currently has a burnt-out woodburner as the only source of heat. We don't have any central heating at this property. The woodburner will be in the metal skip soon. Easy install, and so far seems to heat and cool well. 700w when in heating mode.

4m, lucky you…. We’re end of terrace so we’re limited to 3m external.

I’m sure you’ll breeze through this. I know what you mean about the stress of the unknown, and although my project is a drop in the ocean compared to yours (rear extension), the fact that the digger is on site and the builders are starting today, has given me lots of stressful days arguing with the wife 🤣 This isn’t your first rodeo, sounds like you’ve thought of everything and it’s all falling into place. Mine is my first rodeo 🤦‍♂️

Ah, the great PIR con….. PIR is great stuff, don’t get me wrong, but the manufacturers have spent an enormous amount of time and money marketing the stuff as the only product worth using. The reality is, other products are perfectly decent when applied to the correct thickness, and they bring other benefits. Specifically in the case of cavity wall insulation, the ability for the product to completely contact the inner skin, flowing around the mortar snots. All insulation has a U value, so one product can give just the same performance as another, it just might need to be thicker.

I’d go full fill fluffy (something from rockwool, probably) on 150 cavity…. Standard method that every builder knows and understands. We’re about to start a rear ex next week in this exact buildup. Rendered conc, 150, cellcon inner.

I remember BIL (brickie) mentioning poured in situ boot lintels when he was working in Germany in the late 90’s, so that would tally up with what we might be seeing here.

Be aware of the price of 200mm cavity ties, they’re eye watering…

It’s single skin construction using those fired clay hollow blocks, with interlocking joints. I’m not sure if this will have ewi but I assume so. it’s almost like the lintels are set back from the face of the block then the gap is filled with foam.

Snapped a photo of a new build going up in Langenfeld, thought it might prompt discussion on a few things. Are those externally insulated lintels?

Look in the daikin installation manual and wire/plumb it up as per their designs, using their controls. that way you’ll get best efficiency. Im going to get shot for saying this here, but no need for the tmv or pump on the ufh manifold, let the ashp do it all.

I’d have my real reservations about getting the heat transferred up through the 22mm chipboard tbh…. I would be inclined to full fill the joist depth with insulation then use an overlay panel system like torfloor2, or if you have the buildup height available then an overlay panel with some self leveller over the top.

I would 100% expect a window company to know that check reveals are a thing in Scotland. It's really unacceptable that the OP has been messed about because of this incompetence by the window companies surveyor.

You don't even need drawings... Scotland = check reveals... Simple...

I genuinely don't know how this industry manages to recruit such incompetent people... It's shocking really

If a glazing company doesn't know what a check reveal is, and how to measure one, they shouldn't be in the glazing business...