Should I insulate vent pipes in loft (from DHW cylinder and central heating)

[Oxbow16]

Hi

 

I recently did some pipe insulating in my loft.

 

The only two I didn't do were the vent pipes. Not sure if that is the right term for them? They are the pipes that feed water back into the top of the tanks when there is excess, presumably from steam, expansion, etc. The one going to the cold water tank is 22mm. The one going to the F+E tank is 28mm.

I didn't insulate them because...

 

1. The water has to rise from the airing cupboard into the loft, UP the pipes until the very end where the pipes bend down through the tank lids. As such, water can never be sat in the pipes can it? And if so, it cannot freeze if not sat in it.

 

2. If both are used for excess, steam, expansion etc, then won't any water travelling through always be hot?

 

Or have I missed something? If anyone could confirm whether they need insulating or not that would be great.

 

Many thanks

[BotusBuild]

My opinion - if it's in the loft, and it MIGHT contain water, then insulate it. Better safe than sorry

[marshian]

You need to think very carefully about the water level in the pipes in an open vented system

 

Those tanks that feed the CH system and HW system have a level of water in them - the same level of water will be in the expansion pipes (they will be at equilibrum with the tank levels

 

So draw a line from the tank level to the pipes and insulate to just above that point

 

If un-insulated then they will contribute to heat loss from HW tank or the CH circuit - it might be small but heat rises as a general rule so heat will be lost.

 

I moved my CW tank and CH header tank 3m away from the loft hatch because I always caught my back on the support frame and it gave me a more usable loft space - However this meant I had to extend all the pipework by the same 3m (as a result I have quite long runs in the cold loft space) I insulated all the pipes with thick wall pipe insulation OD for both 15mm and 22mm is around 62mm which means my pipe lagger mitre box can be set up to work well with either size insulation

 

Happy to be corrected on this by more knowledgeable contributors