Pipe insulation

[Tuttle]

I'm installing central heating, hot, cold and pumped hot and cold pipework (6 pipes in total, in copper) under a first floor, notched into the top of floor joists.

My problem is that the joists are only 174mm deep so the maximum notch allowed is 21.75mm, which is not a problem for the 15mm central heating pipes (feeding three radiators) but is a bit tight for the hot and cold water supplies, for which I plan to use 22mm pipe (feeding a power shower, bath, wc, a couple of sinks and a washing machine).

I am planning on cutting 22mm deep notches in the top of the joists, but this means that the 22mm pipe will be tight up against the floor boards, and with no room for any pipe insulation. I should be able to insulate the heating pipes ok, and I could keep hot and cold pipe separate, but I can't see how I could insulate them at all.

So my question is, do the hot and cold water pipes have to be insulated / what would others do in this situation?

I need to get this right as it is an extension and so is subject to building control approval.

Thanks

 

[plumber0808]

If there's a room above then you don't need to lag them, if its a roof area then yes you need to lag them. If you can not notch them drill through the joists.

21.75mm is the max permitted but in practice this never is the case and it would be notched to take 22mm pipe

 

[Tuttle]

If there's a room above then you don't need to lag them, if its a roof area then yes you need to lag them. If you can not notch them drill through the joists.

21.75mm is the max permitted but in practice this never is the case and it would be notched to take 22mm pipe

Thanks.

Yes, there is a room above (or a landing actually, but I guess that's the same as a room) and a room below.

 

[Tuttle]

I think I found the answer in the Domestic Building Services Compliance Guide as well (Gas-fired space heating and hot water systems, Table 3):

i. Primary circulation pipes for heating and hot water circuits should be insulated wherever they pass outside the heated living space or through voids which communicate with and are ventilated from unheated spaces.
ii. Primary circulation pipes for domestic hot water circuits should be insulated throughout their length, subject only to practical constraints imposed by the need to penetrate joists and other structural elements.
iii. All pipes connected to hot water storage vessels, including the vent pipe, should be insulated for at least 1 metre from their points of connection to the cylinder (or they should be insulated up to the point where they become concealed).
iv. If secondary circulation is used, all pipes kept hot by that circulation should be insulated.

So it looks like I'm ok, apart from pushing the notch depth a little bit 🙂

 

[Guest123]

If you find it impossible to use pipe insulation, then wrap a layer of glass wool (or similar) loft insulation under the pipework and a layer over it. It can be nailed to joists too with a 25mm baton.

I tend to insulate everything I can that is going to be hidden under floors and behind walls etc. Saves a headache in the future.

 

[chris watkins]

I take it that the floor void is between the ground & first floors ?
If it were on the ground floor & ventilated all the pipes would have to be insulated. Just to be clear.

 

[Tuttle]

Yeah, its in the void between the downstairs ceilings and first floor floor boards.

I've got quite a bit of rockwool insulation lying around here at the moment, perhaps that would be a good thing to put under the pipes in the notches as well to stop any heating/cooling noises (as well as around the pipes).

Not sure what you mean by "It can be nailed to joists too with a 25mm baton" though?

 

[Guest123]

Nailing it to the joists is a good way to secure it if you have to wrap it over the pipes. Normally I put a layer under the pipes and a layer over it. Rockwool is cheap to buy and works a treat. It's great for getting into all the hard to insulate areas too and small sections torn off can be secured with tie wraps. Wear gloves and a mask though!

Rockwool is also good for insulating under baths, especially steel ones that give you a cold bum in the winter. Keeps the heat in the bath when filled.

 

[AWheating]

put some rap lagg betwwen the joists and the pipes to stop noise and use some nail clips evey other joist or so to stop watta hammer. I would not worry about cutting a few mm more than allowed tbh aslong as you stick to notch zones you should be fine. keep the cold away from the hot and heating if possible.


if you did want to pipe lagg it all you could drill the center of the joist and put plastic through.