I've added an extra layer of plasterboard above the existing one in this bay as a precaution against noise from the filter getting in to the room below. I've no idea if this is likely to be necessary, but it's now or never! It also might reduce additional outside noise coming in through the extra 150mm diameter duct hole cut in the roof soffit getting there too. The ventilation filter is at the end of the bay and has been attached via flex duct to the soffit vent. I added an extra noggin / cross beam to catch the silencer in the unlikely event it becomes detached from the stud wall.
The filter box is attached to the roof rafters with this "handle" made of OSB offcuts.
The filter box is attached to the handle with screws through the top of it into the OSB. A bit of sealant on each for a proper seal.
View of filter box through the hatch from the room below. It's pretty easy to reach through, open the box and exchange the filter cartridge.
Test fit of the partially assembled silencer in the eaves bay. Propped on various wood offcuts until the correct height is reached, is plumb and does not foul on the sides of the bay;
Wood props at the hatch end.
A test fit of the duct flange & duct to filter box. Once in place I drew round the flange to determine the correct position to cut the duct hole in the silencer. When properly installed I will use flex duct to connect the silencer to the filter box so they are acoustically decoupled.
Hatch cover, the wooden frame will be painted white to match the ceiling. The frame is larger than I had hoped, but necessary to ensure a reliable seal.
Inside of the hatch cover with double plasterboard layer. The frame has rebates cut for rubber seal.
Final silencer assembly. This one is the standard design, it didn't have to be stepped like the exhaust silencer as the house structure does not impede it in this bay;
It's also the original width, 20mm wider than the exhaust one, which had to be reduced to fit the narrower bay. It is a considerable size.
Flange in place. Let us hope my measurements were good!