Lagging individual plastic water pipes or just put insulation on top

[volks]

Getting new plumbing in the loft with grey plastic pipe stuff. Should I lag the individual pipes or just put a roll of loft insulation over the top to trap heat in from the hot pipe/any rising heat from downstairs?

 

[CBW]

They should be insulated with pipe insulation to help prevent freezing/heat loss.

 

[volks]

They should be insulated with pipe insulation to help prevent freezing/heat loss.

Ah yeah of course, I just didn't know if it's better to insulate them individually or put rockwool over the top so the heat from the hot pipe gets trapped next to the cold pipe to warm it up.

 

[Madrab]

Ideally, if pipes are run in any space that is unheated then the pipes should be lagged.

That being said If the pipes are clipped parallel with the joists low down with the ceiling below and then >200mm of insulation is sat on top then I'm sure that would be fine. If they are above any insulation or up over the joists with insulation on top then no, they really should be lagged.

 

[CBW]

Ah yeah of course, I just didn't know if it's better to insulate them individually or put rockwool over the top so the heat from the hot pipe gets trapped next to the cold pipe to warm it up.

If you warm the cold up, then this might become a problem for bacteria growth, cold should be kept under 20 degrees, otherwise it’s classed as undue warming (against water regulations).

 

[volks]

Hi all. Follow up, my plumber advised not to lag the plastic pipes as they don't give off much heat anyway. He said to just throw some loft insulation on top.

Is he right or talking a bit of nonsense?

 

[Madrab]

Depends on what pipework it is, lagging or insulating in an unheated space is always recommended.

Either by individual lagging or insulation, just 'throwing some on top' wouldn't exactly be very effective, doesn't take much to lag a bit of pipe.

 

[volks]

Depends on what pipework it is, lagging or insulating in an unheated space is always recommended.

Either by individual lagging or insulation, just 'throwing some on top' wouldn't exactly be very effective, doesn't take much to lag a bit of pipe.

Well I think by throwing on top he did mean laying insulation over it and wrapping around the edges, but yeah. The gist is the same.

Pipework is PEX push fit plastic stuff as well.

 

[StephenStephen]

Heating water then allowing it to leak to the loft, the cold pipe or anywhere else is a waste of energy.
If it were mine I'd insulate the hot pipe carefully, making sure it's thermally separated from the cold, then put loft insulation over both.