floor insulation in garden room

[Jupiter01]

I have this type of floor and foundation for my garden room. I will be fitting PIR insulation into these sections, with a batten screwed at the bottom to hold it in place. A couple of questions for the experts:

1. What's the easiest method to cut this 75mm insulation?
2. I was planning to have the insulation flush at the top. Not sure why but that's how I've seen it done...However, some of the floor sections will have 15mm pipes and cables running through the joists. How do I adapt the insulation in these sections?

Thanks in advance.

 

[stevie888]

Simplest is a woodsaw. Ideally cut with a small taper so you have to gently tap the piece in and it then grips with no gaps. Flip the board for the next cut and go vertical as you only need 1 taper.

It might sound obvious but cut across the short dimension of the board: much easier..

Simply set the insulation low and you have a gap for your services.

 

[endecotp]

You can buy "insulation knives" that have the advantage of not creating a lot a dust. Or just buy the cheapest (longish) woodsaw you can find, that's what I did.

Re pipes, what I did was to buy one board of thinner PIR and cut that up to use where the pipes run, leaving a gap. But in my case the insulation was sat on a flat subfloor, so it would be more difficult for you.

Cables in insulation have specific rules to prevent them from overheating. Ideally keep the cables away from the insulation.

 

[Jupiter01]

Cables in insulation have specific rules to prevent them from overheating. Ideally keep the cables away from the insulation.

I am reluctant to put the cables below the insulation as they will then be exposed to the elements. I was planning to use a similar arrangement to the pipes. The cables can run in a void between the OSB floor and the insulation, which would have been set deeper in the sections that have pipes or cables running.

 

[Jupiter01]

I've had a rethink on this and am now planning to take all cables and water pipes up the wall and back down to where they need to be. There isn't too many points and this will just allow me to crack on with the floor and get it finished.
In the wall and the ceiling I was going to keep the cables and the pipes in the air void, behind the insulation. Perhaps I should lag the plastic pipes?

 

[endecotp]

Perhaps I should lag the plastic pipes?

Yes, you should worry about the frost risk. Do you have a way to isolate and drain down for the winter?

(Any hot water pipes?)

 

[Jupiter01]

Yes, you should worry about the frost risk. Do you have a way to isolate and drain down for the winter?

(Any hot water pipes?)

Yes, isolation valve as it enters the building. No hot water pipes