JoeJoe wrote:
I have a brand new combi running 18 radiators + 1 shower in my house. No
complaints there.

Problem is that the radiators seem to be getting very cold very quickly as
soon as the boiler is switched off. My suspicion is that the cause could be
because some of the pipes (copper) hat feed the downstairs radiators are not
insulated. I have a 1m high space under the house, where the pipes are
located, and it is freezing cold and drafty there.

Does it make sense?

Not really. Once the boiler shuts off, there is no more heat input into
the system. The various components will lose heat to the surroundings.
The rate of this heat loss will depend on how good each component is at
losing heat. Radiators are, by design, good at losing heat.


Will it be a good idea to insulate the pipes? It
shouldn't be a very big job.

Certainly not a bad idea to insulate them, but it won't make a
measurable difference to how quickly your radiators lose heat.


What shall I use? I was thinking about something like this (
http://www.screwfix.com/app/sfd/cat/...10943&ts=33331)

That's the stuff.


but: 1. it
seem to come in various levels of thinkness (which is suitable?)

The thickest you can fit in.


and 2. it may be tricky to fit in some places.

If you can't reach a particular piece of pipe, just leave it.


--
Grunff