Hi, I’ve got my MVHR designs but wondering about coming up through the floors deck (above posi joists). I have one section where all of my upstairs ducts will come through as o 7 ducts each with 75mm diameter. I’m wondering whether I should cut a rectangular section and add noggins around the edges of deck or individual circular holes or something else? Thanks

As my MVHR unit is loft based, I constructed a small floor to ceiling cupboard in my sons room for shoes and the like.  At the back of this is a 300mm*500mm void which I pass a bunch of ducts and an SVP stuffed with sound insulation as best i could.  All through egger ontop of posi's.  Personally I wouldn't cut each hole individually.

 

Edit,  All this is within the heated envelope of the house.

Edited August 7Aug 7 by crispy_wafer

1 section. Its quite common to have a hole like this somewhere. On some sites they cut a hole 1400 by about 200 to pass plasterboard up through then nog and patch after. 

On 07/08/2026 at 07:13, junglejim said:

Hi, I’ve got my MVHR designs but wondering about coming up through the floors deck (above posi joists). I have one section where all of my upstairs ducts will come through as o 7 ducts each with 75mm diameter. I’m wondering whether I should cut a rectangular section and add noggins around the edges of deck or individual circular holes or something else? Thanks

That's what we have done. Noggins around the Finn Joists. Currently the 22mm T&G is in place, ready to be cut through when the duct is installed. Ours are 108mm insulated pipes.