Because of the inclusion of extensive noise control criteria in the 2010 Guidelines For The Design and Construction of Health Care Facilities and with acoustical points available in LEED for Healthcare (released last year), I have found healthcare facilities designers increasingly interested in ensuring that their designs address the acoustical environment. However, achieving the acoustical criteria in these documents is not always easy. It sometimes requires changing customary design practices.
Designers may find that standard details they have used for years, aren’t sufficient. This can apply to the HVAC systems, the exterior glazing, the room finishes, or even patient room partywall details. In fact, there has been much talk about patient room partywall details and some gypsum wallboard manufacturers claiming or strongly suggesting that acoustical gypsum wall board must be used in order to meet the Sound Transmission Class (STC) criteria in these documents.
So why are they suggesting that expensive acoustical gypsum wallboard must be used?
The 2010 Guidelines and LEED for Healthcare have similar recommendations/requirements because they are both based on the same document, the Facility Guidelines Institute’s “Sound & Vibration Design Guidelines for Health Care Facilities.” This document requires a minimum of STC45 for patient room partywalls. This doesn’t seem like a difficult criteria to meet… after all it’s easy to open the Gypsum Association Handbook and find a wall detail that will suffice. Something as simple as a 3-5/8” steel stud wall with one layer of standard gypsum board on each side and some batt insulation will do the job. But it’s not that simple. If you look at a collection of recent STC test reports from reliable laboratories you find a range of about STC43-48 for that simple wall construction, and that’s for walls which have 25 gauge studs spaced 24 inches on center. If you use 20 gauge, you reduce the STC by about 5 points. 16 gauge, minus 6 points. Wallboard lighter than 5/8” Type X, lose another point. 16 inch spacing, loose 3 points. Wall cavity not full on insulation, lose more points. It is possible to design a wall with steel studs, two layers of gypsum board each side, and batt insulation and not have the wall meet STC45. But to be more constructive, here are some examples that would meet STC45:
• 25 gauge 6” mtl. stds. 24” o.c., 1 lyr. 5/8” Type X GWB each side, cavity full of batt insulation
• 20 gauge 6” mtl. stds. 24” o.c., 2 lyr. 5/8” Type X GWB each side, cavity full of batt insulation
• 25 gauge 3-5/8” mtl. stds. 24” o.c., 3 or 4 total lyrs 5/8” Type X GWB, cavity full of batt insulation
OR
• 16 or 20 gauge 3-5/8” mtl. stds. 24” o.c., 1 lyr. acoustical gypsum wallboard each side, cavity full of batt insulation
Of course all of the walls must be thoroughly sealed to the underside of the deck and the through penetrations by pipes and conduit must be sealed. The acoustical degradation caused by double sided headwalls should also be considered.
Are these patient room partywall types standard practice? Perhaps for some, but certainly not for everyone. Similarly, there are criteria for HVAC system noise, room acoustical finishes, and facade glazing that may differ from the standard practice of some designers. I’ll address some of these other issues in future articles.