Most industrial exhaust must discharge at roof level to comply with NEA requirements. Getting ducting from the unit to the roof involves constraints that are frequently discovered too late, after the lease is signed and the fit-out is underway. By then, the options are limited and the cost of solving the problem is borne entirely by the tenant.
This post is for industrial tenants planning exhaust installation, food production operators verifying unit feasibility before lease, and tenants with exhaust-dependent operations assessing a new unit. Confirming routing feasibility before signing is the single most important due diligence step for any exhaust-dependent operation, especially food production or any process involving cooking fumes, chemical fumes, or significant odour.
Building Rules on Duct Routing
Buildings restrict or prohibit external wall mounting of ducts for appearance, structural load, and liability reasons. Internal routing through shared shafts requires permission from building management and, in multi-tenant buildings, from other tenants whose floors the duct passes through.
Roof access and penetrations require landlord approval. Once approved, penetrations must be weatherproofed and the duct flashed to prevent water ingress.
Maximum duct size is typically limited by the building’s shaft or structural provisions. A system requiring a larger duct than the building permits cannot be installed without major modification.
Common Routing Scenarios
Designated exhaust shafts are the ideal scenario: purpose-built vertical shafts with spare capacity. If one is available and sized appropriately, routing is straightforward. Many purpose-built food factory buildings have these.
External wall mount requires building management approval, structural supports, and weatherproofing. It is visible from outside the building and some landlords restrict this approach entirely.
Internal routing through occupied floors is rare and complex. It requires written permission from every intervening tenant. In practice, this option is rarely available in multi-tenant buildings.
Shared duct systems require checking both capacity and compatibility. Connecting to a shared system that is already at capacity prevents additional connections.
Roof-Level Constraints
Discharge direction must not blow toward neighbouring air intakes. NEA may require specific discharge heights and directions depending on nearby sensitive receptors.
Minimum discharge height above roof level is specified by NEA and varies by building context.
Rooftop space is competed for. Other tenants’ HVAC equipment, antennae, and structural elements occupy roof space. A duct route that appears feasible may be blocked by existing installations.
Structural capacity for heavy ductwork must be confirmed. A duct full of grease and condensate weighs more than a clean duct, so structural support must be sized accordingly.
Summary
Rooftop duct routing is constrained by building rules, shaft availability, roof-level space competition, and structural capacity. Before committing to a unit, confirm shaft availability or external mounting permission, maximum permissible duct size, discharge direction and height requirements, and whether the building has a history of exhaust complaints. These constraints cannot be resolved after signing if they were not identified before signing.
For the full exhaust and ventilation overview, see Exhaust / Ventilation / Odour Control Basics.
For the exhaust system viewing checklist, see Viewing Checklist: Exhaust System Condition.
For make-up air requirements, see Make-Up Air Explained.
For noise control basics, see Noise Control Basics.
For grease duct maintenance, see Grease Duct Maintenance.
References
[1] NEA: Air Pollution Control — Exhaust and Emissions. https://www.nea.gov.sg/our-services/pollution-control [2] NEA: Odour Management. https://www.nea.gov.sg/our-services/pollution-control/ [3] SCDF: Acts, Codes & Regulations (Fire Safety). https://www.scdf.gov.sg/fire-safety-services-listing/downloads/acts-codes-and-regulations [4] SCDF: Fire Safety (Buildings) Regulations. https://www.scdf.gov.sg/fire-safety-services-listing/downloads/acts-codes-and-regulations [5] BCA: Building Plan Submission. https://www1.bca.gov.sg/safety-and-standards/building-control-act/ [6] MOM: Workplace Safety & Health. https://www.mom.gov.sg/workplace-safety-and-health [7] JTC: Industrial Space. https://www.jtc.gov.sg/find-space/