Cellulose Answer Man: Your Source For Information
Paul C. posed an interesting question:
I am a contractor working with cellulose to put into ceilings for builders in Australia. We have currently been questioned on the issue of the weight limitations for dry cellulose in ceilings (putting excessive pressure on plasterboard ceiling sheets) as compared to fibreglass batts. We would typically install R4.0 – R6.0 into new build projects which we would estimate somewhere between 4kg and 6kg per m2. While the same in fibreglass batts is estimated at only 2kg/m2.
Would you have any information or reference material that would assist us in determining appropriate weight limitations for cellulose installed in ceilings? I realize this may vary depending on how the ceiling has been constructed – however at this point we would be grateful for any information that may be able to assist us to use as a reference for supporting the use of cellulose insulation into ceilings.
Great question and one we have not received before. This is really a non-issue. The 6 kg/m2 is about 1.23 psf. For ½-inch US Gypsum Sheetrock installed 24” On Center, it will support 2.2 psf, per USG data sheets. Likely the products available in Australia are much different. Even with currently-published data you could install RSI R10 (US R-60) and still be well below the published weight limit. We have had an e-mail dialog with a senior researcher at the USG Corporate Innovation Cente studying insulation loading on ceiling Sheetrock as it pertains to ICC Evaluation Services Acceptance Criteria. They have looked at their Sheetrock product with up to 4 psf of insulation on it and found no problem.
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