Ducted Ventilation to Guestrooms from Corridors

Summary: The new codes now allow ducted guestroom ventilation for hotels in the west coast states which have now moved from the Uniform Building Code to the International Building Code.

Discussion:  The following code analysis is presented to document the conclusions stated in the summary above.  This topic requires a step-by-step analysis of the code and there is really no short cut to what appears below.  Just to be clear, the question is: Are fire/smoke dampers required at the penetration of the duct into the guestroom at the corridor wall?

Code Analysis:

1.    The code defines four relevant types of separation that must be addressed as part of the code analysis.  Those types are: Fire Barriers, Fire Partitions, Smoke Barriers, and Smoke Partitions.

2.    Addressing each type of separation, we find the following:

a.    Section 706 Fire Barriers: This applies to the hotel corridors.
b.    Section 708 Fire Partitions: This applies to the separation of hotel sleeping units (guestrooms)
c.    Section 709 Smoke Barriers:  This section does not define where smoke partitions are required. It is silent regarding where the section is applied.
d.    Section 710 Smoke Partitions: This section does not define where smoke partitions are required. It calls upon other sections to provide that definition.

3.    Are smoke barriers and smoke partitions involved with guestrooms?

a.    Section 419 Group I-1, R-1, R-2, R-3:  This section applies to guestrooms and states that walls separating sleeping units shall comply with Section 708.  That means the walls between guestrooms are Fire Partitions.  It does not elaborate and extend the rating to Fire Barrier, Smoke Barrier, or Smoke Partition.

4.    Section 706 requires ducts and air transfer openings comply with Section 716.

5.    Section 708 requires ducts and air transfer openings comply with Section 716.

6.    Section 716 addresses duct and air transfer openings of all types.  Paragraph 716.6 Where Required defines where fire dampers, smoke dampers, and combination fire/smoke dampers are required for each type of separation. There are then two cases to analyze the hotel guestrooms. The first case is a duct routed in the corridor with taps to each guestroom through the corridor wall. This case involves crossing a Fire Barrier. The second case is a duct routed from guestroom to guestroom which involves crossing a Fire Partition. These two cases are analyzed below.

7.     Duct Routed in Corridor: Since we know from above that guestroom separation from the corridor is a Fire Barrier, then the applicable sub-paragraph is 716.5.2 Fire Barriers:

a.    This code requires fire dampers except where the duct system is constructed of 26 gage steel and the ductwork is continuous from the air handling equipment to the air outlets in the guestrooms.
b.    Conclusion: The 2006 IBC allows air supply to guestrooms from a common duct in the corridor without fire dampers or smoke dampers as described above.

8.    Duct Routed in Guestrooms: Since we know from above that guestroom separation is only a Fire Partition, then the application sub-paragraph is 716.5.4 Fire Partitions:

a.    716.5.4 Fire Partitions:  This sub-paragraph requires fire dampers in ducts and air transfer openings except when all of the following conditions are met:
i.    Building is sprinklered.
ii.    Duct penetration is less than 100 square inches.
iii.    Duct is 26 gage steel.
iv.    No openings communicated to corridor.
v.    Duct installed above a ceiling.
vi.    Duct not terminated at the corridor wall.
vii.    A 12 inch steel sleeve through the corridor wall is provided for the duct.
b.    Conclusion:  The 2006 IBC allows an air supply to guestrooms from a common duct in the corridor without fire dampers or smoke dampers if the conditions of 716.5.4 are met.  The following is a review of those conditions:
i.    Sprinklers:  No problem.
ii.    Duct less than 100 square inches:  We need 30 cfm of air per guestroom, therefore, a 4″ diameter duct is sufficient for a guestroom.  A 4″ duct has an area of 12.5 square inches and meets this criteria.
iii.    26 gage steel is standard.
iv.    The duct would have no openings to the corridor since the corridor air system would be a separate system.
v.    A ceiling would be provided for the corridor.  This is not always the case, but would be necessary (and desirable) under these conditions.
vi.    The duct could not be terminated at the corridor wall of the guestroom.  This requires some form of soffit in the guestroom, which is easily accomplished.  The grille can then be installed at the wall of the soffit.
vii.    A 12 inch sleeve through the corridor wall is easily provided.  The requirements for this sleeve are detailed further in the code.

 

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