I am wanting to install underfloor insulation (ie Earthwool batts) between the bearers under my house.
The measurement between the bearers is 420mm but I am wondering if I could use the 470mm wide batts and squeeze them into the smaller area? The wider batts are more convenient to install as they can be stapled into position by tabs on the sides of the batts whereas the narrower batts need straping.
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Welcome to the Workshop community @Diannelin. I'm happy to answer your question.
I would advise using the 420mm batts and strapping. Strapping them in place once you start should be just as fast as using the tabs system.
The tabs are designed to hold the batt in place at 470mm so when you compress them there is the potential for the batt to sag in the middle. This is due to the batt not being stretched across the bearers tightly. This might be fine when installing but they may sag over time due to gravity. This will drastically change the R-value and potentially you'll need to strap them anyway.
If you would like further information or had questions about the process, please let me know.
Thank you so much for the information.
I will go with the 420mm batts as you suggest.
Appreciate your reply.