For a six story building (plus a basement) each of the six floors has a useable area of =3716 m2 (40.000 ft2) There are two riser systems, each serving halt of the useable area on each Moor What are…

Question

Options

• ATwo sleeves
• BThree sleeves
• CFour sleeves
• DFive sleeves

• A
  10% (4)
• B
  17% (7)
• C
  2% (1)
• D
  71% (30)

Explanation

Five sleeves are required because each of the two riser systems needs a supply air sleeve and a return air sleeve (2 × 2 = 4), plus one shared exhaust/relief duct sleeve common to both systems passes through the slab between the fifth and sixth floors, giving a total of 4 + 1 = 5. This 4+1 configuration is the standard layout for a dual-riser commercial HVAC system where supply and return are handled independently per riser zone, but exhaust is centralized.

• A (Two sleeves) is wrong: two sleeves would only account for a single supply duct per riser system - it ignores return air entirely.
• B (Three sleeves) is wrong: three would cover supply, return, and exhaust for only one of the two riser systems, leaving the second system unaccounted for.
• C (Four sleeves) is wrong: four accounts for supply and return for both riser systems but omits the shared exhaust/relief duct that must also penetrate the slab.
• D (Five sleeves) is correct: it captures the full 4+1 layout - both supply and return for each riser (4), plus the one shared exhaust sleeve (1).

Memory tip: Think "4+1 rule" - two risers × two functions (supply + return) = 4, plus 1 shared exhaust = 5. If a question gives you two riser systems, always ask yourself: supply, return, and what's shared?

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