Glueing insulation to CH pipes.

[wobbly2]

I have posted before about our heating but have not really found a solution, so apologies for any duplication.

I'm after some advice on how to insulate the central heating pipes beneath our ventilated suspended timber floor, where the pipes cross the floor joists.

• There is insufficient room/depth to fit insulation above the pipes, which are mainly 22mm and ¾”.
• The gap above the pipes varies between 2 or 3mm to nothing and in several places the floorboards touch the pipes.
• The existing lagging is not very thick, perhaps 9 or 10mm, made of very lightweight sponge foam that is disintegrating and where severely squashed is split, resulting in it sagging away from the pipes and/or falling off.
• I understand the current building regs require pipes installed in an unheated space to be insulated with 25mm thick insulation.

To make things more difficult the floor joists are only 4" deep and have already been over notched and some will need replacing/sistering due to being severely weakened; so notching the joists deeper is not an option.

My thoughts are that we only have two choices:-

1. Replaced the pipes and fix them to the underside of the joists, which will be expensive and very disruptive or
2. Insulate the existing pipes where they are, which will be difficult because there is no room above the pipes and therefore little to no insulation to hold itself in place.

• I've thought to shave the top off the insulation such that when installed it wraps around the pipe with its cut edges pressed against the underside of the floorboards, relying on the floorboards, underlay and carpet to provide insulation at the top; not ideal but hopefully much better than we currently have. With this method, keeping the insulation in place will need some support otherwise it will/may drop off over time. I wondered about:-
  • Supporting it from below with timber battens.
  • Glue the insulation to the pipes if acceptable, in which case what would be a suitable adhesive?
  • Wire/tie the insulation in place. Not ideal because if the wire/tie fails the insulation will drop off.

Any help will be much appreciated.

 

[Tigercubrider]

Cable ties.
The only issue will be accessing the relevant areas to grip the ties tight.
You can trim foam insulation where needed, obviously this lowers the insulation factor but the floor absorbs the heat and technically, at least, sends it to the home.

 

[wobbly2]

So toastier radiators and underfloor heating.

It seems anything that provides an escape path for the heat is frowned upon these days, no gaps, thinning, air movement from within etc. Won't pulling the cable ties tight deform the insulation pulling it away from the floorboards producing gaps and thinning the insulation where the ties are placed, making it less effective or will the loss be negligible and of little importance?

Thinking about it, any form of tying the insulation in-place will most likely stop the cut edge of the insulation from pressing up on the underside of the floorboards, resulting in gaps that will allow the heat to escape, or again am i concerned about nothing?

 

[Tigercubrider]

Cable ties don’t need to be tight to support items.
Logic says that if there’s room and the ability to position the insulation, turning the foam so it sits atop the pipe rather than hangs off it will help. Ditto where room is scarce. Loads of insulation is held on with insulation tape but it can go gooey and fail. Cable ties hold effectively and don’t tend to fail.

You can only do what’s possible.

 

[Alec_t]

In the grand scheme of things, the length of pipe over notched joists is only a small percentage of the total pipe length, and wood is a reasonable insulator anyway, so heat loss from that small percentage won't make much difference to your heating bill.

 

[StephenStephen]

I shaved the top and, where needed, taped them in place with a bit of duck tape - worked fine.

Don't worry about it being frowned upon!

If they're heating pipes, then you're only going to have hot water in them when you want to heat the rooms, which are above the pipes - so yes, it's effectively a little bit of underfloor heating...

 

[wobbly2]

In the grand scheme of things, the length of pipe over notched joists is only a small percentage of the total pipe length, and wood is a reasonable insulator anyway, so heat loss from that small percentage won't make much difference to your heating bill.

Hi Alec, I don't think I have explained properly or I don't understand what you are saying.
The issue is not where the pipes pass through the notches in the joist, it's where the pipes span between the joists as the floorboards almost sit directly on top of the pipes with perhaps a 2 to 3mm gap at most between them (pipes and floorboards).