"TheScullster" wrote in message ...
Not too sure of your layout, but better to go up in duct size than down!
That way you get 6" (150) stuff - readily available and (more importantly
perhaps) you decrease rather than increase the velocity for a given air
flow - therefore should be less noisy.

Phil

Thanks to all that have replied, you've given me plenty to think
about. I should have provided some details of the ducting run I'm
thinking of doing. Some of the points made would be very valid on a
larger run, but I'll be sure to consider them in this run that is just
less than 2 meters. To give you an idea of where I up to on this
'do-er' up property, please see the URL below.

http://oli4uk.tripod.com/ducting01.htm

Again, Thanks to all that took the time to reply.

- Oliver.