Full text coming one day - this is mostly a place to find the spreadsheet for now

This is the spreadsheet I used to calculate the rates required for the whole house and various rooms, and the correct sizes for a tree-structure of rigid ducting that would be quiet and low-resistance wihtout being larger than they needed to be. The sheet can do both round and squre PVC and galv steel ducting, in sizes commonly available in the UK, but it's easy to add new pipe sizes and materials.

It does the turbulence and flow resistance calculations from first-principles (navier-stokes) so should give reliable numbers for any design.

The sheet was built for the particular tree-structure of piping I used, so you will have to modify which branches are added to which other branches for whatever duct layout you have. It would be lovely to have some nice graphical design software that let you draw the layout, then did the combination sums for that new layout, but that's some extra work to generalise this sheet, or combine it into CAD software or whatever. If anyone is enthused to do that work I'd be very happy to host it.

Some pics and system details will go here...