pipe lagging

[byron]

I have been advised today that plastic pipe used for c/heating runs does not need to be insulated as you would copper pipe,ie in runs thro loft areas.Woild this be correct.

 

[outinthestix]

I've seen a few frozen plastic pipes . For what it costs I'd lag 'em.

 

[corgiman]

yep they can freeze, the may not burst but they sure as hell can freeze

as stix says whats the harm better safe than well you know the rest

 

[ChrisR]

Also they lose a huge amount of heat. Not as much as copper but it will cost you dear if you don't use the best insulation.
Measuring pipe temperatures round heating systems can be alarming - often 30% lost under ground floors where hairy felt rubbish insulation has been used.
It's cheaper to use 22mm pipe, because you need so much less insulation than 15mm!

 

[byron]

Thanks for the replies ,what would be the best brand to buy ,is the stuff .wickes worth buying

 

[corgiman]

I think its all much of a muchness

 

[chrishutt]

It's cheaper to use 22mm pipe, because you need so much less insulation than 15mm!

How so? The surface temperature of the pipe will be the same and the insulation thickness required for heat conservation will be the same.

 

[byron]

That reply got me thinking as well

 

[ChrisR]

As in all things, consider an extreme - you wouldn't be able to keep water warm in a 1mm pipe, but in a 1m pipe you'd have trouble changing it.

Cooling effect of environment is proportional to
(surface area divided by volume).

= (length * pi * diameter) /(length * pi * diam *diam /4)
Ignore the 4, as we're just looking for proportionality and you get
1/(diameter)

So eg if you need 25mm insulation for 15mm pipe you only need
(15/22) * 25 = 17mm for 22mm pipe

Which is somewhere the Water Regs Byelaw 49W35 figures of 25mm for 15mm pipe and 19mm for 22mm pipe.

I was wrong about the costs though, now that copper is more expensive. The extra cost of the insulation for 15mm is about (1.60- 1.05=) 55p per metre (prices from screwfix)
whereas 22mm tube cost about £1 per metre more.


Insulation figures vary by 2 :1 for best:worst materials.
Best figures are 0.020 W/mK or better (lower!)

 

[byron]

I will take your word for that chris,thanks