Hello, I have recently built a twin block 450mm plinth wall on which will sit a wooden box beam followed by a timber frame wall with straw bale infill. Hanging from the box beam and just into the blockwork will sit engineered 300mm i-joists at 40mm centres spanning the 7.7 metre width and sitting in a stub wall through the centre. The perimeter wall will be well ventilated with 65m air bricks and DIY vent sleeves passing through the clockwork to ensure a decent air flow. I'm looking for advice on wether to use thermafleece or similar sheepswool or wood fibre board for the insulation. My questions as follows:
1) How best to fix from above, potentially using ply wood fixed to the bottom flanges as a support for the insulation?
2) Where to place membranes to ensure air tightness and contain liquid spills from above?
3) Any other tips?

Thanks!

Tony,

1) which materials would you classify as biodegradable in this context? What alternative would you recommend from an eco point of view? I do not wish to us PIR.

2) noted, thanks.

3) why strawberry netting instead of marine ply?

Posted By: djhThe main worry with underfloor insulation is moisture, followed by rot and/or pest infestation. That's because of its position and because it is difficult to inspect and maintain. Unfortunately, the best way to let water drain out of underfloor insulation is to leave the bottom exposed, whilst the best way to keep pests out is to seal it closed.

Rigid insulation between joists is difficult to install properly, especially without foams, so one common alternative is rockwool.

Thanks for your view DJH.

Posted By: tonyI would go for quilt, either rock wool, fibreglass or ecowool(fibreglass with recycled plastic I think)

Hi Tony, do you have experience of using either of these. Or a preference. Ecowool claim to have a product which is formaldehyde free and low in VOCs. I'll check it out.