So I've pretty much decided to DIY our MVHR install using a radial system. I'm also having a go at designing it, but am not sure how to calculate the total static pressure of the system, so I can make sure it's not working too hard. The passive huas trust indicates it should be <100 Pa ideally.   I get the general idea of pressure drops, and how to work out the pressure drop of an individual run. You sum the pressure drop from each component in the run, bends, ducts, attenuators, at