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What is the chances of cuts in galvanised duct rusting? Got bare metal and moisture. Granted it should never condense if everything is good. Are the cuts painted over or does everyone use the joints that go inside the duct so the cuts aren’t in the flow? Was looking at the Lindab safe duct for ease of getting a good seal but the duct goes into these and a cut there seems like a bad idea.

Thanks. That was design from online seller. Had some concerns over it but didn’t know enough when first got it. Learning process, going to spend the weekend doing the calculations. Are there any recommended templates? Was gonna copy some of the previous posts as a starting point. Was concerned about the amount of exhaust in kitchen, utility and Qc with no supply for them. The amount of ducts in that design wouldn't be possible, the access holes needed would be to big.

Ventilation GF.pdfVentilation FF.pdfApologies for delay getting back. Your hybrid system sounds very interesting. I’ve attached one location guide for radial ducts. I moved the ground floor manifold trying to get better location but it was above the island originally. I was thinking of hybrid system 4 distribution boxes for the supply, 2 for upstairs and 2 down and this would make shorter runs and smaller holes in walls. Had got to point where after all that was thinking a simple branch system would be easiest.

Hi. Left it to the last second, roof going on and need to get an MVHR system. Original spec was couple of drimasters but living in house with one and it creates a very noticeable cold draft. In previous house most the extraction points and chimney were blocked up due to drafts and noise of them flapping in the wind (never had any condensation). So hoping MVHR will be better. Due to costs going to be doing a self install but have quotes for 2 competing systems. One is radial and the other is a branch system. It’s a 2 storey with a concrete first floor so the branch system is looking attractive to minimise hole size required thru the slab and the block walls on flat holding them up. However the radial system of continuous pipe to every duct and the ease of install is appealing although realise still need the big ducting to get to them. Reading the forums a few have installed both systems in different builds, did you have a preference? The house is kinda a T shape with a bit joining them in middle. Both radial and branch designs have system installed in hotpress on one side but this will cause quite long pipe runs to the valves and the for the external supply and exhaust. Considering moving unit into attic. This would make very short external runs and then have separate ducts for both sides of the house with each downstair manifolds installed between ceiling and slab. Not sure though how the system would be balanced if the rings are in the manifolds as they will be plastered over. Am I missing something, do you need to leave a hatch or can it be balanced at the valve? Can’t take all the individual radial pipes from the attic, hole would be too big. What’s the consequences of going for the 90mm over 75mm radial ducts? There is quite an increase in airflow versus the increase in price.