Does pipework inside house need lagging

[phatboy]

I am re-plumbing the whole house using Hep2O manifolds and plastic barrier pipe, so a pipe run to each outlet (15mm & 10mm, as flow requirement dictates).

Most of the pipework will be in the loft, below the insulation. Should these pipes be lagged, as they should be the same temperature as the rooms below? Would there be a risk of very cold water entering the cold pipes causing condensation on the pipes, and damaging the plasterboard?

Any advice much appreciated!

 

[Madrab]

Best practice to lag pipes everywhere, as anywhere they are not heating the living spaces then it's just wasting energy.

I would try to avoid mixing 15mm and 10mm feed pipes, radiator sizes dependent. The most efficient systems are typically on a 22mm backbone with 15mm feeds to the rads unless the house is highly insulated and there are a small number of rads with low output.

 

[phatboy]

Best practice to lag pipes everywhere, as anywhere they are not heating the living spaces then it's just wasting energy.

I would try to avoid mixing 15mm and 10mm feed pipes, radiator sizes dependent. The most efficient systems are typically on a 22mm backbone with 15mm feeds to the rads unless the house is highly insulated and there are a small number of rads with low output.

Thank you.

This isn't CH plumbing actually, it's hot and cold to every outlet in the house, so 10mm to a wash basin, or toilet, should be plenty, and reduce the dead leg of water.

In the name of cost saving, I may insulate the part in the warm side with 9mm Armaflex, and the parts that go outside of this with 19mm. If that seems reasonable? Armaflex is bloody expensive!

 

[Madrab]

Ah ok, fair enough. 10mm supply pipework to outlets can be more than enough, especially with smaller number of outlets with water saving inserts etc.

Of course, any insulation is better then none and you are correct Armaflex isn't cheap. HW side especially as it minimises heat loss on the way to the outlet and keeps it warmer for longer in the pipework.