Share this...


  • If an STC of greater than 38 is required, interior access doors will almost always be necessary. The addition of access doors and between-glass blinds is a great way to improve acoustic performance and reduce solar heat gain, but remember that dual glazing in not recommended for cold-climate hospitals.
  • The practical limit on sealed IG air space width is 3/4” to 1” depending on make-up.
  • Don’t use glass manufacturers’ acoustical performance data to predict “whole window” performance. There’s no dependable way to “adjust” for the effect of rigid support.
  • Mix and match STC requirements based on location and elevation to minimize cost, e.g. add access doors on the lower floors adjacent to the highway only.
  • Make sure that acoustical performance requirements are written in clear, technically-valid language, preferably citing STC or OITC, and that the glass descriptions in the Glass and Glazing section of the specification match the acoustical requirements of the Metal Windows section.
  • No manufacturer can reasonably be expected to test every frame-glass combination, so specifiers are encouraged to accept existing test reports at bid time, as proof of compliance. Test-to-test variation is greater than minor configuration or make-up differences. Demanding “guarantees” of performance for untested frame-glass combinations at bid time will result in costly over-design.