Issues with IWI on a single wall?

[mrbrunes]

Hi

My end terrace's front room has a 5m x 3m solid brick 9" side wall which I'd like to insulate via IWI (likely 50mm PIR). EWI not possible due to conservation area. Exact method TBD as I'm still trying to digest the Gov.uk IWI Guidance, lots of threads and all sorts of scary stuff about thermal bridging and moisture control.

The front wall is also solid wall but contains a bay with three secondary glazed sash windows plus a front door - basically lots of "fiddly" bits around already lossy areas with just two <1m x 3m areas of "normal wall". It's going to be significant extra disruption and extended labour time to insulate that as well.

Will leaving the front wall uninsulated cause real problems? Is it really worth the extra labour? Or will just insulating the large side wall be OK (as long as I make sure it's sealed properly etc.)

 

[John D v2.0]

You can insulate selectively but it means there will be less wall that's cold, meaning any humidity in the air has a smaller area to condense in, meaning you're more likely to get mould on the remaining area.
I think for me it would depend if the uninsulated wall is north facing, but it's a judgement call

 

[^woody^]

You need to think exactly on why you want to do this, and what problems you are trying to solve and what benefits you hope to get. What's the cost of all this instead of alternative solutions - one of which is turning the heating up.

50mm is a bit random is not a great amount of insulation so why 50, and not 60, or 70 or 100? What about the floor (if timber), and draughts. If you hope to save money, what savings over how long? It's a lot of disruption, so will there be tangible gains?

If you have condensation issues now, be careful not to just shift them around, or if you are borderline be careful not to create issues.

Basically, you need to think a bit more laterally than just 'I want to insulate one wall with a random thickness of insulation'. Otherwise you may be disappointed.

 

[mrbrunes]

Tx for the replies.
The reason for 50mm is that I think it will be an improvement over no insulation at all, given that seating will be near this wall with a CH radiator and it will look reasonably acceptable with the pre-existing victorian coving as long as I taper it back near the top. Otherwise anything more than 50mm plus pboard is going to look awful. I recall seeing somewhere that 60mm would be an ideal compromise but I think it's just too thick. The old plaster is gone since I'd already taken down an old lath & plaster wall and so I thought a bit more dust wouldn't hurt!

The timber floor is already insulated with rockwool over a finished basement.
Front door draughts are noticeable so that will be the next project. I'm not sure how draught-proof one can make a period door with varying gaps and single glazed panels, so I'll be putting in a door curtain or possibly construct a small internal porch if it's really bad.

I've no condensation issues currently. The potentially left-as-uninsulated wall is south-facing and won't have any seating nearby (so hopefully a slightly colder wall won't be too noticeable).