Section 27-335.1. Acoustical and thermal insulation; use in noncombustible construction

(a) Notwithstanding any  provision  of  this  code  to  the  contrary,
  acoustical or thermal insulation which is not noncombustible may be used
  where noncombustible construction is required if:
    (1)  it satisfactorily passes a test for determining noncombustibility
  of elementary materials,  based  on  the  test  procedures  of  A.S.T.M.
  El36-65,  and,  upon  exposure  to  fire  will  not  produce products of
  decomposition  or  combustion  that  are  more   toxic   in   point   of
  concentration  that those given off by wood or paper when decomposing or
  burning under comparable conditions; or
    (2) it has a flame-spread rating not greater than twenty-five, a smoke
  developed  rating  not  greater  than  fifty,  is  without  evidence  of
  continued progressive combustion when tested in accordance with the test
  procedure  of  reference standard RS 5-5, and upon exposure to fire will
  not produce products of decomposition or combustion that are more  toxic
  in  point  of  concentration  than those given off by wood or paper when
  decomposing or burning under comparable conditions.
    (b) Notwithstanding any provision of subdivision a of this section  or
  any  other provision of this code to the contrary, acoustical or thermal
  insulation, which is not noncombustible and  which  does  not  meet  the
  requirements  of  subdivision  a  of  this  section,  may  be used where
  noncombustible construction is required subject to the approval  of  the
  commissioner,  and  provided  it  is  installed in a composite method of
  construction, with a minimum of three inches  of  unpierced  masonry  or
  concrete on all sides.
    (c)  Notwithstanding  any  provision  of  subdivision  a  or b of this
  section or any other provision of this code  to  the  contrary,  thermal
  insulation,  which  is  not  noncombustible  and which does not meet the
  requirements of subdivisions a and b of this section, may  be  installed
  in  an  exterior  wall  system in any noncombustible construction group,
  provided that:
    (1) such insulation is of a thickness no  greater  than  four  inches;
  provided,  additional  thickness  used  exclusively  for  decorative  or
  leveling  purposes  shall  be  permissible,  where  the  area  of   such
  additional thickness does not exceed fifteen percent of the wall area on
  any single story;
    (2) such insulation has a heat value not in excess of six thousand BTU
  per square foot;
    (3) such insulation is installed in a composite method of construction
  and  is  separated  from  interior spaces by a thermal barrier having at
  least a one-hour fire resistance rating;
    (4) such insulation  has  a  flame  spread  rating  not  greater  than
  twenty-five  and  a smoke developed rating not greater than four hundred
  fifty, and is covered with, and sealed or joined by, material  having  a
  flame  spread  rating not greater than twenty-five and a smoke developed
  rating not greater than  fifty,  when  tested  in  accordance  with  the
  procedures of reference standard RS 5-5;
    (5)  such  insulation  is  installed  in  a  manner  which  meets  the
  requirements for firestopping set forth in section 27-345;
    (6) upon exposure to fire, the exterior wall system and  each  of  its
  components will not produce products of decomposition or combustion that
  are more toxic in point of concentration than those given off by wood or
  paper when decomposing or burning under comparable conditions;
    (7) the structure on which the exterior wall system is installed meets
  the  requirements of section 27-331 pertaining to minimum horizontal and
  vertical separation distances; provided, however, that  such  insulation
  shall  not be used on the exterior surface of a wall of a court or shaft

  if the horizontal or vertical separation distance between such wall  and
  another wall of such court or shaft is less than twenty feet;
    (8)  the  use  of such insulation on soffits or other horizontal areas
  shall not extend more than three feet beyond the  outside  face  of  the
  building enclosure;
    (9)  the  use of such insulation on buildings having party walls meets
  the requirements of section 27-332;
    (10) such insulation meets  the  acceptance  requirements  of  section
  27-131;
    (11)  the  results  of  a fire test of a representative portion of the
  exterior wall system meet the requirements of reference standard RS5-21;
    (12) the edge or face of the assembly containing  such  insulation  is
  labeled with the following information:
    a.  the  name of a nationally recognized testing laboratory acceptable
  to the commissioner which has inspected such insulation;
    b. the model of the exterior wall assembly for which  such  insulation
  is  listed  by  a nationally recognized testing laboratory acceptable to
  the commissioner;
    c. the identity of the manufacturer of such insulation;
    d. the flame spread and smoke developed ratings; and
    (13)  the  installation  of  such  insulation  shall  be  subject   to
  controlled   inspection   to  ensure  that  the  installation  is  fully
  consistent with the terms of the  listing  by  a  nationally  recognized
  testing   laboratory   acceptable   to   the   commissioner,  acceptance
  requirements of  section  27-131  and  the  manufacturer's  installation
  recommendations.
    (d)  The  commissioner may, with regard to thermal insulation, the use
  of which is authorized by  this  subdivision,  establish  by  regulation
  training  criteria  for persons installing such insulation, and prohibit
  the installation of such insulation by persons not  adequately  trained.
  Any  person installing such insulation shall certify to the commissioner
  that the installation is fully consistent with the terms of the  listing
  by   a  nationally  recognized  testing  laboratory  acceptable  to  the
  commissioner,  acceptance  requirements  of  section  27-131   and   the
  manufacturer's installation recommendations.
    (e) Definitions. As used in this section:
    (1)  "Composite  method  of  construction"  shall  mean  a  method  of
  construction  in  which  diverse  materials  are  combined  to  form  an
  assembly,  whether  the  assembly  is prefabricated or fabricated at the
  site of installation.
    (2) "Exterior wall system" shall  include  the  exterior  walls  of  a
  building and the appurtenances thereof.