I assume that you need the roughness to calculate the fan duty.
I would recommend that you involve a ductwork textile manufacturer early in design.
They normally have computer packages which could emulate the air flow pattern within the space and give you advice on what type of textile duct is...
The 'weighted louvres' you are looking for are called in UK air pressure stabilisers.
If you type on the net you will see some USA based manufacturers.
I personally used them for pressurised staircased or operating theatres in UK.
Hello,
I am a mechanical engineer with experience in healthcare in UK.
Recently I have been asked to design operating theatre suites to American standards.
In UK we have clear design guide, HTM 03-01 for theatres being the most relevant. This document provides clear advise on pressure regimes...