What is the best duct to use?

[Risemead]

I have had a few quotes for the MVHR installation for our new build.

They will use four units to cover the "basement, FF & two units to cover the GF".

They have quoted for the Vent Axia units.

What do you think is the best ducting I should expect them to quote for?

One has quoted using rigid PVC - I feel this is not good? shall I ask them to change?

The other one is Galvanised spiral ducting to externals and to manifold boxes, with 75mm OD radial ducting system – x15 rolls semi-rigid ducting (50mtrs).

I come across the semi-regid is more prevalent in domestic installations, is this ok to use? or any other suggestions?

Anything else I should be looking in the quote to make sure I am not missing any?

[Tims]

What are the 4 units? Is it a really big build or are they single room units. 75mm OD diameter semi rigid ducting is fairly usual for a radial system doubled up on a lot of feeds, 15 * 50m rolls I guess says its a really big build and again rigid galvanised spiral duct (insulated) is fairly standard to the outside world. I think that the only real reason that semi rigid is preferred over rigid PVC is ease of routing but if your system is being installed during the build I'm sure that rigid PVC is fine and may even have slightly less loss (maybe not though)