Redbeard

Has the roof been stuffed full of insulation? If so you could end up with condensation on the underside of the roof 'deck'. What did the installers tell you?

Apparently it only works when you sit it on a 230V hot-plate.

Are you doing this from the top or from below, with the boards in situ? I assume from the top as you refer to taping as VCL (on the warm side). Why not carefully cut joist-width slivers of 25mm PIR and glue to underside of joists, then when you slide the 125 PIR down it should meet at the bottom of that 'fillet'. Yes, the joint won't be tight as a duck's whatever, but an extra piece of softwood won't be very insulative either.

I forgot to mention that. Maybe it's a basic H & S measure - glue your left glove to the stack with silicone while you use more of the same stuff to make a right mess just below...? (Remember not to take hand out of glove).

Oh yes, poor insulation and a cold void will do it! (a) The supplier should come back and remedy that (unless insulation of ducting was specifically 'by others') and (b) What did they say/promise? I'm trying to establish whether they in effect gave you a 'performance specification'. If so, the 'actual' has not met that spec. You say that you did not expect the MVHR to provide for your full heat load, but not too far off. What did they tell you it *would* provide?

Surely some sort of balancing issue? I would be asking the supplier exactly why they believe that a 10 degree difference in supply air temp is to be 'expected'. I would then expect them to point to design specifics if they are to explain why.

Hmmm. I'd like them to show me it was roofing mastic designed for 'pointing' lead. I have never seen that in white. Even if it is not it may 'behave' OK but it is the wrong horse for the course. Is the scaff still there? Sad if not. It would take 30 mins max including climbing to sort it now. 99% of passers-by will not notice it but I suspect you will, and it will annoy you. Given that they appear to have used 'Leadmate' below I guess it may just be a case of having the wrong stuff in the gun and using it anyway. I am not a roofer, BTW.

Welcome. If you have not already done so, please start a new topic under the relevant heading so that the replies go to that rather than in this intro section.

Looking back on previous posts I cannot be certain that your addition of timbers has actually increased structural strength. Have you got a designer? If your pic 2 went a bit higher then maybe you could avoid a sketch and simply annotate the pic. Critical issues are: How much will the floor come UP (assuming existing additions are not SE-specified) and How much does the roof come DOWN (assuming exg rafters 75mm and the need for an absolute min of 150 PIR, plus a min 50mm air-path above, and a 'plenum chamber' below the ridge). I have some concern re height under the dormer ceiling too. Let's see what it would look like with the same 150 insulation/50 air path and, perhaps (not mentioned for sloping roof, but needed) counter-battens for a Service Void.

Don't think pics show enough. Draw a quick floor plan so we can see where stairs might go. and a section to see if any bits of structure will 'impinge'. At 7'6" (just under 2.3m) its sounds like it is going to be really tight once you 'come down' with the requisite insulation and ventilation above that (assuming 'cold roof' constr'n). Again, lets see a section dwg with dimensions on. It can be as 'sketchy ' as you like, as long as dim'ns are there.

Could have wished for your fully-installed prices, @JohnMo!

I think it never makes sense. Keep the full one.😉

In another thread @saveasteading said: "Hijacking the post. Apologies. Wouldn't it be useful if members could publish the cost of their windows divided by the area?" I'll start: Green Building Store 3G timber, U value appr 0.75W/m2K - factory glazed and finished- 1 bay, 1 opening casement. Appr £635/m2 installed: 2014 Local Yorkshire window manuf'r, 2020. 3G TF to similar spec to GBS: Appr £690/m2 installed Green Building Store 3G timber U value appr 0.85W/m2K, *supply only*, 4 windows and one fully-glazed door: £734/m2 2022

Several years of experience tells me that this may not be 100% accurate! Yes, if you buy a £5 (or whatever that is in Euros) gun it may clog up or bend whatever type of foam you use. No gun which I have used with FM330 has ever failed and they have all been in the £10 - £20 range.

Probably insulation, primarily. Then of course if you want UFH you are all ready to go.