Fabric duct and galvanised iron (GI) duct can both form part of a conditioned-air distribution system. The appropriate choice depends on the required performance, available space, operating conditions and maintenance arrangements. Compare complete engineered proposals against the same brief before deciding which offers better project value.
For facility engineers and project specifiers in Saudi Arabia, the useful comparison extends beyond duct material prices. Include outlets, connections, supports, access, insulation where required, testing and care. Keep every assumption visible, especially when one quotation includes work that another leaves to a different trade.
Start With The Same Project Requirements
Define the application before comparing products. Record the room use, dimensions, ceiling height, occupied areas and proposed air distribution layout. Identify whether the package concerns exposed supply-air distribution, concealed transport ductwork or a specialist duty. A comparison becomes misleading when the two proposals serve different boundaries. For the operating explanation, read how fabric duct works.
GI means galvanised iron; in ductwork discussions, confirm the proposed galvanised sheet-steel specification rather than relying on that abbreviation alone. Fabric duct likewise describes a system category, not a single material grade or performance rating. Ask each bidder to identify the exact products, fabrication requirements and supporting documentation.
Give both design teams the same airflow requirements and operating assumptions. Include available fan information, supply conditions, intended operating hours and any changes expected during normal use. Where inputs are missing, label them unresolved and assign a responsible person to obtain them before final evaluation.
Set the acceptance criteria with the HVAC reviewer. Ask how each proposal will demonstrate the required distribution and operating performance. Do not award a technical advantage simply because one bidder supplies more persuasive marketing images. Evidence should relate to the actual room and proposed installation. Coordinate the wider HVAC scope with the responsible designer.
Compare Air Distribution And Design Requirements
Discharge And Occupied Zone Coverage
A fabric system can discharge through permeable textile, engineered outlets or a combination. A GI system commonly conveys air to selected terminals such as diffusers or grilles. Compare the resulting room performance, including outlet selection and placement, rather than assuming the material determines comfort.
Ask for the proposed discharge pattern and the design assumptions behind it. Manufacturer fabric guidance identifies mounting height and required throw as selection factors. The corresponding GI proposal should explain its terminal selection and coverage assumptions. Both submissions should address obstructions, occupied locations and the intended room use. Reference: fabric system design considerations.
Avoid categorical statements that one option always eliminates drafts or that the other inevitably produces uneven temperatures. Require the project designer to assess the proposed arrangements. Where a performance prediction depends on assumptions about furniture, storage or occupancy, record those assumptions alongside the selection.
Pressure And Operating Range
Request the design pressure basis for each proposed system and identify the operating range. Ask how the duct arrangement, fittings and outlets relate to the available fan conditions. For the fabric option, confirm the exact product limits and any support arrangement needed at reduced airflow.
For the GI option, establish the construction, sealing and leakage requirements in the specification. A rigid material description does not establish installation airtightness or the required construction class. Ask the reviewer to confirm the applicable requirements and the evidence needed to show the installed system meets them. Reference: SMACNA duct leakage test manual overview. Confirm project applicability separately.
Routing Zoning And Coordination
Compare the actual layouts, including branches, transitions, elevation changes and access constraints. Establish how each proposal serves separate zones and accommodates controls. Avoid assuming fabric must always be a straight tube or that GI layouts are automatically suitable regardless of congestion.
Check coordination with lighting, structure, sprinklers and other services through the project drawings. For an exposed ceiling, include appearance during the expected operating conditions. For a concealed installation, verify access and the suitability of the proposed system for that location. Coordinate any later change through the responsible designers.
Compare Installation Scope
Supports And Access
Ask each bidder to show its complete support arrangement and identify who designs and supplies the fixings. Include access equipment, work areas and any restrictions on installation hours. A lower duct weight does not remove the need to check suspension details or the supporting structure.
Compare installation programmes on the same basis. Record fabrication information needed before production, delivery assumptions and the availability of coordinated drawings. Do not claim a fixed time saving without a project programme and comparable work scope. Installation speed is an evaluated outcome, not an automatic material attribute.
Connections Insulation And Associated Works
Identify the boundaries at the air-handling equipment, transitions and terminal connections. Confirm who supplies associated fittings, controls and access provisions. Ask the designer to specify insulation and vapour-control requirements where applicable. Include those costs consistently rather than pricing bare ductwork against a complete finished package.
For fabric, confirm the suspension accessories, end details and section identification. For GI, confirm the proposed joints, sealing, supports and any specified protective or insulating finishes. Both proposals should identify exclusions and any work expected from others, with written agreement on interface ownership.
Commissioning Evidence
Define the checks and records required for the installed arrangement before contract award. Ask who prepares the testing plan, carries out the checks and resolves defects. Include the relevant operating conditions and accepted drawings in the handover record. Neither duct material removes the need for agreed verification.
Compare Cleaning And Maintenance Requirements
Compare actual care arrangements for the proposed products. Fabric manufacturers may permit removal and laundering of specified sections, subject to their instructions. Establish the method for the installed textile, including handling, drying and reinstatement requirements. Washability alone does not establish a facility’s hygiene compliance.
For GI duct, ask how the specified installation will be inspected and cleaned. Review access locations, reachable surfaces and any limitations associated with internal components or finishes. Do not assume every metal system requires the same cleaning method or that cleaning can be completed without operational disruption.
Manufacturer fabric guidance distinguishes performance, appearance and hygiene considerations. Apply that distinction to the maintenance discussion: state the reason for cleaning and the conditions that trigger it. Avoid adopting a universal interval from another facility or another fabric grade. The site’s requirements and selected-product instructions should inform the plan. Reference: manufacturer care guidance.
Compare labour, access equipment, protection of occupied areas, removal and reinstallation work, and the time needed before service resumes. Record who authorises any interruption and how the facility will operate during the work. Removable sections do not establish that unaffected areas can remain in normal operation.
Where replacement sections or specialist services are proposed, confirm availability through the supplier. Treat delivery periods and support arrangements as quotation items to verify. Do not invent a service-life figure for either system or assume that a material category guarantees local spare-part availability.
Build A Lifecycle Cost Comparison
Initial Installed Cost
Request prices against the same scope and identify the quotation date. For a Saudi project, record the currency as SAR and show whether VAT and other stated charges are included. Compare complete installed packages, with exclusions and provisional items visible, rather than relying on a rate per metre alone.
Initial costs may include engineering, supply, fabrication, transport, supports, connections, installation access, specified insulation and testing. Mark items outside the bidder’s scope and obtain the corresponding cost from the responsible package. An unpriced exclusion should remain unresolved rather than being entered as zero.
Operating And Cleaning Costs
Energy comparisons require project calculations. Ask the reviewer to establish comparable airflow, fan operation, operating hours and the relevant system losses. Use the project’s applicable electricity tariff and dated assumptions. Neither fabric nor GI material alone demonstrates lower annual energy consumption.
Build cleaning costs from the agreed care method, labour allowances, access requirements and service interruptions. Keep the basis consistent across both proposals. If cleaning frequency has not been established, compare clearly labelled scenarios rather than choosing an interval that favours one option.
Repairs Replacement And Study Assumptions
Use a common study period and document how future costs are treated. Include expected repair and replacement events only where a defensible basis exists. Identify any assumed residual value and the financial approach used to compare costs occurring at different times. Keep US or other overseas reference factors out of Saudi project calculations unless specifically justified.
Lifecycle-cost methods consider costs over time rather than only the initial investment. For this article, the useful output is an evidence request and comparison structure, not a fabricated payback result. Test whether the preferred proposal changes when uncertain cleaning or replacement assumptions change. See the NIST building lifecycle-cost overview for methodology context, not Saudi rates.
| Factor | Fabric proposal | GI proposal | Evidence / assumptions |
|---|---|---|---|
| Design | Fabric, outlets and operating range | Construction, terminals and zoning | Common duty and coordinated layout |
| Installation | Suspension and section connections | Supports, joints and specified finishes | Complete inclusions and exclusions |
| Cleaning | Approved method and reinstatement | Inspection and cleaning access | Care plan and downtime |
| Operating cost | Calculated system and fan inputs | Calculated system and fan inputs | Same hours and project tariff |
| Lifecycle | Repair and replacement assumptions | Repair and replacement assumptions | Same study period; dated quotes |
If the conclusion depends on a poorly supported assumption, identify it as a decision condition. For example, ask for a revised cost comparison after the maintenance method is confirmed. A transparent unresolved item is more useful than an apparently precise total built from invented inputs.
Identify Unsuitable Or Unverified Applications
Keep ordinary comfort supply-air comparison separate from grease exhaust, smoke extraction, high-temperature processes and other specialist duties. Neither “fabric” nor “GI” establishes suitability for those applications. The responsible professional must assess the exact product, construction, operating conditions and applicable project requirements.
Verify material and environmental limitations for both proposals. Request the relevant evidence for temperature, exposure and fire performance where required. Do not describe a textile treatment as equivalent to a fire-resistance rating. Likewise, do not treat ordinary galvanised ductwork as a complete fire-rated system simply because it is metal.
A mixed arrangement may be proposed where different parts of the building have different requirements. Ask the designer to define its interfaces and justify each selection. Combining systems is an option to assess, not a promise that an unreviewed connection will perform correctly.
Compare Proposals With MTC
Share the common project brief, coordinated layout, operating assumptions and maintenance constraints with MTC. Request a comparison showing the proposed fabric and GI scopes, exclusions, material evidence and acceptance records. Ask the appointed HVAC reviewer to resolve technical uncertainties before selecting the package.
Review MTC’s Fabric Duct and GI Duct commercial pages to discuss the project comparison. Confirm the proposed scope and product evidence in writing with the appointed HVAC reviewer.
Frequently Asked Questions
Is Fabric Duct Always Cheaper Than GI Duct?
No universal cost advantage can be established from material names alone. Compare complete installed scopes and then evaluate operating, cleaning and replacement inputs over the same study period. Obtain dated quotations and identify exclusions. Any saving should be calculated for the project rather than copied from a manufacturer’s general claim.
Can Both Systems Be Used Within One Project?
A designer may propose different systems for different areas or functions. The arrangement needs defined connections, operating conditions and responsibility for coordination and testing. Ask for the reasoning behind each selection. A mixed system should be assessed as a complete design rather than assembled from independently chosen products.
What Evidence Supports An Energy Cost Comparison?
Use project-specific airflow, system pressure-loss calculations, fan selection, control assumptions and operating hours. Apply the relevant electricity tariff and identify the source date. The HVAC reviewer should confirm that both options meet the same duty. A general claim about duct material cannot substitute for that comparison.
How Should Cleaning Downtime Be Compared?
Request a method and programme for each proposed installation. Include access, any removal, cleaning, drying where relevant, reinstatement and return-to-service checks. Confirm how occupied areas will be affected and what temporary arrangements are needed. Keep assumptions about cleaning frequency separate from the duration of each planned interruption.
Does A Material Fire Classification Establish Suitability For Specialist Exhaust?
A material classification alone does not establish that a complete duct system suits a particular specialist duty. Require assessment of the exact product, construction and application by the responsible professional. Confirm the relevant project requirements and supporting evidence. Neither ordinary textile nor ordinary GI construction should be assumed suitable without that review.