Resilient Bar under Rafters

[MortarThePoint]

You can use Resilient Bar on ceilings and on walls so it stands to reason (?) you can use them under the rafters of a pitched roof.

 

I'm tossing up between the following three options, all to allow 75mm of below rafter Mineral Wool insulation:

1. 50x47 timber batten on 25mm standoff blocks [£1.20/m]
2. 50x25 timber battens on 50mm stand off blocks (strong enough to take my weight on a single one spanning 600mm) [£0.80/m)
3. Resilient Bar on 63mm standoff blocks (no way strong enough for me to stand on) [£1.50/m for comparison as at 400mm c/c unlike timber at 600mm c/c]

 

The Resilient Bar has the benefit of near eliminating the batten thermal bridge as the insulation behind it would be the full 75mm except where the blocks are which improves U-value by about 0.004. One thing I can't decide if it's a good thing or a bad thing is that Resilient Bar won't couple the plasterboard to the trusses as solidly as timber battens would. The bad side of that could be a sloped wall with a bit of give, though I haven't heard of people complaining about walls with Resilient Bar being flimsy, but maybe that's because of the sound isolation meaning I can't hear their cries. The good side is that it could protect the plasterboard from minor movements of the trusses as they age. Could that help avoid cracking.

 

Obviously the Resilient Bar would be good for sound isolation, but that's not needed here.

 

Has anyone used Resilient Bar under rafters or have any thoughts on this?

 

Edited April 1, 2022 by MortarThePoint