Overcoming Condensation on Internal Stack Pipe

Live in top floor flat. Have removed excessive boxing around communal
stack pipe (that goes through my flat from roof down to sewer) in
order to make space for much needed cupboards.
However, stack pipe (some 4 inches diameter and made of cast iron) is
attracting much unwanted condensation due to being so cold! Obviously
I need now to insulate it, hence this post and wish to seek advice as
to best way to proceed.
My thoughts so far are :
1. Just box around like before but much smaller boxing to allow for
cupboards.
2. First insulate stack pipe with Screwfix "Spiral Wrap" page 457 of
catalog 89 item 62194-89 - which is a kind of self adhesive foil
covered bubble wrap, then box around.
3. As 2 above but then add a covering of aluminium foil tape on top
of the spiral wrap to help prevent water vapour ingress using
Screwfix "Aluminium Foil Tape " page 162 catalog 89 item 15089-89.
Ideally would like some purpose made insulation sleeve to fit around
and cover join with foil tape. Does anyone supply this?
Thanks in advance for your help and interest.
Reply to
Graham
The key is to make sure that the stack gets no vapour. I.e. it needs a vapour barrier.
Insulation not required, though it would at least make sure you didn't lose heat via the pipe.
When I was slating my kithen floo during that very hot simmer a few years back, I was disconerted to see what appeared to be a leak in the newly installed plumbing. Thetr was just a temporatuy rttap iff teh incoming cold..all other plumbing was blanked off pending kitchen installation. I eventually worked out that with all the cement I was mixing, the air was saturated with vapour, and the constant use of the cold tap was causing condensation on the incoming main..which was dripping off.
In your case, I'd build boxing out of foil backed board, and stuff rockwool in it.
Reply to
The Natural Philosopher

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