acoustic foam fill for cmu

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Author Message Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 923 Registered: 01-2003 Posted on Tuesday, August 30, 2016 - 12:15 pm:    We're considering a couple of options to increase acoustic properties for a CMU wall in a school, sand fill or http://www.core-fill500.com/. I haven't seen the foam product before; any comments? Liz O'Sullivan Senior Member Username: liz_osullivan Post Number: 207 Registered: 10-2011 Posted on Tuesday, August 30, 2016 - 12:39 pm:    Some injection foams have urea-formaldehyde, which some green building programs prohibit. So check that out if you have any green codes or requirements. user (Unregistered Guest) Unregistered guest Posted on Tuesday, August 30, 2016 - 12:38 pm:    In north Texas area we specified foamed-in-place to fill cores instead of sand on quite a number of school projects. The contractors could not seem to keep the sand dry; and when one inspector asked the contractor to drill a hole in a mortar joint to verify sand had been installed, a large pile of sand poured out onto the slab. Dave Metzger Senior Member Username: davemetzger Post Number: 656 Registered: 07-2001 Posted on Tuesday, August 30, 2016 - 12:47 pm:    By "acoustic properties" do you mean reduce sound transmission? Mass is needed for that, so the sand would be more beneficial than foam. Also consider using normal-weight CMU--we've done that for theaters at the recommendation of the acoustic consultant. anon (Unregistered Guest) Unregistered guest Posted on Tuesday, August 30, 2016 - 12:43 pm:    Here's an oldie but goodie: http://www.cbisinc.com/PDF/General/110_Sound_Transmission_Through_Korfil_Insulated_Masonry.pdf Concluding that Korfil in CMU "appears" to improve STC values by 10%-15% for 8 and 12 inch thick walls. Here is another document (NCMA TEK 13-1C) that offers information about STC improvement in CMU with hollow and filled cores: http://www.ncma-br.org/pdfs/5/TEK%2013-01C.pdf Grout filled and solid block perform as well or better than sand filled block. ken hercenberg Senior Member Username: khercenberg Post Number: 1011 Registered: 12-2006 Posted on Tuesday, August 30, 2016 - 01:36 pm:    I'm not a big fan of foamed-in-place products or sand when filling CMU. Korfil works well, just remember to coordinate with your vertical rebar. Using the insert that allows you to center the rebar tends to work best. As Dave points out, mass seems to help. Fully grouting normal-weight block is worth looking at. Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 925 Registered: 01-2003 Posted on Tuesday, August 30, 2016 - 02:39 pm:    I was skeptical about the foam, as it has less mass than sand or grout fill, but the manufacturer claims it performs about the same. I had looked at the NCMA table and found the STC for CMU to be 53, the same as claimed for the foam. The report referred to by anon is interesting in that it includes a lot of supposition and not much testing. Perhaps the biggest (only?) advantage the foam has over sand was mentioned by "user": Drilling a hole in the block, as will undoubtedly happen, could make a mess. It has happened only rarely, but for other projects, I have specified grout-filled block, never sand or foam. David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1506 Registered: 03-2002 Posted on Tuesday, August 30, 2016 - 02:56 pm:    If the block is up above the students' reach, you might consider specifying acoustical CMU products. Sheldon, you did not indicate whether you needed to reduce sound through the wall (STC), or reduce sound within the room (NRC). The products below will increase the room's NRC and help to reduce the reflective sound waves. http://jandrisandsons.com/products/acoustical-cmu/ http://theproudfootcompany.com/Stores/Soundblox/ http://www.rpginc.com/masonry.cfm I have specified these acoustical block products in school gymnasiums and in mechanical rooms. David G. Axt, CCS, CSI, SCIP Specifications Consultant Axt Consulting LLC Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 926 Registered: 01-2003 Posted on Tuesday, August 30, 2016 - 03:48 pm:    Thanks, David. I am aware of those products and have used them, but in this case, I was called in on a project I had nothing to do with until today. I asked, but do not yet know what led to the decision to use sand-filled block, or what the target STC is. My assumption (I know, I know) is that we're after STC rather than NRC because acoustic block as you suggested was not used. Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 205 Registered: 10-2003 Posted on Tuesday, August 30, 2016 - 05:02 pm:    A few reminders about basic acoustics, and a question: Look at the noise reduction at specific frequencies to make sure the wall performance matches the project needs. A high stc wall with openings or gaps around the perimeter is a no stc wall. ----------- Is a layer of gyp board on resilient furring a competitive alternative? Michael Chusid, RA FCSI CCS www.chusid.com www.buildingproduct.guru 818-219-4937 John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1693 Registered: 03-2002 Posted on Thursday, September 01, 2016 - 12:38 pm:    I agree with Michael. Looking only at the STC of the wall/partition may not be the most effective approach for reducing. Doors, gaps, ductwork, wall/ceiling joints, etc. are all more likely to create problems.