Insulating a Crawl Space

[DampCat]

I've just discovered that one of my bedroom walls is completely uninsulated. I've drawn a crude diagram this:

The blue line is the bedroom wall. Behind it is a crawl space. That wall is just plasterboard screwed to some batons and nothing behind it and when you stand near it you can feel the cold permeating through. I have built in wardrobes on that wall and my clothes are freezing when you put them on.

What's my best option for insulating? The hatch for the crawl space is very small, I'm not sure I can get kingspan up there. Is it just a case of using some rolls of insulation between the batons? Do i need to plasterboard over the insulation in that case?

There's also a load of uncovered pipes up there for the hot water. Bleeding British gas

 

[DampCat]

Because British Gas installed the new boiler and hot water cylinder in the garage from the old location in the airing cupboard upstairs. They still haven't wired in the immersion heaters after 2 years of calling once a week. It was they who routed the new pipes through the crawl space into the loft and left them unlagged.

It's a monumental task as the wardrobes are part of the wall, not like a wooden system built to fit. I'd have to destroy the wall and rebuild and replaster it to insulate from this side. If that's the only option then I'll just have to live with it until we can take on that level of work. On the other side it's empty so I was just hoping it could be done from there. I could just cut the insulation board into many pieces to get through the hatch if that's not going to ruin any thermal properties

 

[DampCat]

None of this was supposed to be about the pipes. I don't have a problem with the pipes being there and not sure where I said I did. The small issue is they're unlagged in an uninsulated area. I will lag them. Frustrated with people not doing their job properly.

I will cut PIR board into smaller pieces to get through the hatch, place and tape them. That seems the easiest solution (lots of cutting). The crawl space floor is already rockwooled to 250mm so that should be fine.

Can I use PIR for the underside of the roof in that part? Or is that not necessary?