> By: The Cooling Company
Key Takeaways
- Typical installed bands: spiral $12–$35/ft, rectangular $25–$90/ft, flex $5–$20/ft, insulation add $3–$15/ft.
- Require line-item bids, ASTM leakage testing, and a 5–15% contingency for hidden scope.
- Prefab and BIM on runs over 500 ft can cut installed hours by 20–40% and lower waste.
- Ask bidders to separate shop vs field labor, fittings, hangers, and testing for fair comparison.
What is commercial ductwork cost per linear foot?
Commercial ductwork cost per linear foot is a unit price used for budgeting and bid comparison. Owners use it to set allowances in early estimates and to screen bids quickly. Measure along the duct centerline and include fittings and hangers in your takeoff so your unit price matches what contractors quote. Many variables change that number on a project. Gauge, pressure class, insulation, and fittings all matter. Local wage rates and union rules also change installed costs. Always insist on line-item detail showing shop fabrication, field install, and testing so you can compare bids fairly.What does 'per linear foot' include?
Per linear foot normally covers raw duct material, shop fabrication, and field installation along the centerline. It often includes hangers, common sealant, and standard fittings. Owners should confirm whether items like fire dampers, curbs, or diffusers are separate line items. Ask bidders to show shop hours separately from field hours. That helps you see savings from prefabrication. Also require the type of sealant and insulation to avoid surprises when comparing numbers from different contractors.How do installed and material costs differ?
Material cost is what you buy from a supplier for raw metal, insulation, and fittings. Installed cost adds shop and field labor, equipment, overhead, and contractor markup. Expect installed numbers to be two to four times raw material costs on complex runs. Spot checking bids helps find missing scope. A very low material line with a high labor line may indicate onsite fabrication. Ask for sample shop drawings to see how much shop work each bidder plans to do.Which duct types use per-foot pricing?
Contractors commonly quote spiral round, rectangular, and flexible ducts by the linear foot. Spiral is often lowest per foot for comparable volumes. Rectangular needs more shop work, so it usually costs more per linear foot. Flexible duct is cheap per foot but can increase balancing and leakage risk if used excessively. Require allowances for connectors and supports when bidders price flex so totals match reality. (ASHRAE Technical Resources)How do contractors price duct runs?
Contractors build per-foot rates from material, shop hours, field install hours, and overhead. They also factor in crew productivity, site access, and coordination with other trades. Clear takeoffs and specified test criteria cut bid variance and help spot scope gaps in low quotes. Risk and schedule affect price too. Tight schedules often need extra crews or night work, which raises rates. Ask for separate pricing for overtime or expedited shop work to avoid surprises if the job schedule tightens.What line items appear on a commercial duct estimate?
Typical line items include raw duct, shop fabrication labor, field installation labor, fittings, hangers, and sealant. Insulation, testing fees, and protection are also common. Curbs, firestopping, and diffusers are often billed separately, so check each bid carefully. Require bidders to list allowances for uncommon items like stainless inserts, kitchen grease duct tie-ins, or smoke-control dampers. A clear breakout prevents a low base bid that later adds many change orders.How do labor rates influence per-foot cost?
Crew wage rates and size directly change per-foot pricing. Union markets may add 10–40% on labor-driven items. Skilled shop work for complex transitions also raises unit costs compared to simpler spiral work. Productivity matters as much as wage. A well-run shop with prebuilt stacks usually costs less per foot than field-fabricated transitions. Ask bidders for crew productivity hours per 100 feet to compare labor efficiency.When do access constraints raise prices?
Tight plenum spaces, narrow joist bays, and limited crane access slow work and raise costs. Smaller crews, multiple lifts, or special rigging are needed in these cases. Expect 10–50% higher per-foot prices when access is poor. Site mockups or a site visit report can expose access problems early. Use those findings in the bid documents so contractors price the true install difficulty rather than guessing on the fly.What are typical contractor contingencies?
Contractors usually add 5–15% contingency for missing scope, unforeseen penetrations, and sequencing problems. Owners should prefer a separate contingency line instead of an embedded markup for transparency. That makes it easier to approve or cut allowances later. You can ask bidders to show a zero price with contingency items listed separately. That approach helps you compare core scope prices and then decide on accurate risk allowances.Which materials and shapes change per-foot cost?
Material, shape, gauge, and finishing set the shop time and weight of ducts. Those factors drive per-foot labor and equipment needs. Choosing the right type for pressure class and space reduces waste and keeps installed costs lower. Cost also changes when you need special coatings, double walls, or higher R-values. Those options add both material and labor, so show them as separate bid lines. That helps you trade off upfront cost with long-term performance. (ASHRAE Technical Resources)Which duct materials are cheapest per foot?
Galvanized spiral steel is often cheapest per installed foot for many commercial runs. It is fast to fabricate and light to handle. Flat rectangular galvanized comes next but needs more shop labor, which raises per-foot totals. Flexible duct is inexpensive per foot but can be costly in systems that need rigid flow paths. Overuse of flex can increase fan energy and balancing time, so limit it to short final connections.How does spiral compare to rectangular pricing?
Spiral duct usually costs less per foot because it rolls from coils and needs fewer seams. Rectangular requires cutting, stiffeners, and extra sealing. Expect rectangular to cost 1.5–3 times spiral per linear foot for similar cross-section areas. When space forces rectangular shapes, get a detailed shop layout. That shows where extra stiffening or welding will raise labor. Prefab rectangular stacks often cut field time and narrow the cost gap.How much does insulation add per linear foot?
Insulation adds roughly $3–$15 per foot depending on R-value, facing, and whether factory-applied. Exterior or unconditioned runs in cold climates need thicker insulation and vapor barriers. Sit at the high end of the range. Ask bidders to show factory-insulated vs field-insulated options. Factory insulation often saves field hours and gives better finish quality. Compare both total installed prices before deciding.Which gauges affect commercial duct pricing?
Heavier gauges increase material cost and shop labor for forming and stiffening. High-pressure systems need thicker metal and thus raise per-foot totals. Confirm gauge needs in the project spec to avoid scope gaps. If designers allow multiple gauges, request pricing for each option. That way you can see trade-offs between material cost and expected service life or pressure performance.How to convert per-foot rates to project budgets?
Translate unit rates into reliable budgets by measuring centerline footage, listing fittings, and adding testing and contingencies. Dont accept a lump sum without a clear scope. A clear takeoff reduces surprises and helps you compare bids apples-to-apples. Include allowances for penetrations, curbs, and ceiling repairs in your budget. Many projects add 5–15% contingency for hidden scope. If testing is required, add a separate allowance for possible repairs after failed tests.How to calculate installed linear feet for bidding?
Measure the centerline of each run and include equivalent lengths for elbows where specified. Use as-built drawings or BIM models to validate counts before issuing bid documents. Accurate takeoffs reduce change orders and disputes. If BIM is not available, walk the site with a tape and record high-risk zones. Note congested ceilings and long offsets so bidders can price those conditions directly. (ASHRAE Technical Resources)What contingencies should you include per foot?
Include 5–15% contingency on installed totals to cover hidden items like sleeves, curbs, and unexpected sleeves. Add another 5–10% allowance for failed leakage tests. Be explicit about what each contingency covers so funds are used fairly. Separate contingencies for rework and for owner-directed changes. That keeps contractor responsibility clear and helps you track where funds are spent during construction.How to translate per-foot costs into total budget?
Multiply the installed per-foot rate by the centerline footage and then add fittings, insulation, testing, and contingency. After that, include GC overhead and markup, typically 15–30% for commercial projects. That gives you a realistic total budget to compare to allowances. Ask bidders to show both subcontractor totals and the expected GC markup. That way you can see the true duct cost without hidden general conditions or profit added in unclear ways.When should you require testing or prefabrication?
Specify testing and prefab early in the specs to prevent leakage failures and reduce site labor. Use run-length or ceiling congestion thresholds to trigger mandatory prefabrication. Early rules like these save time and cut rework costs. Testing thresholds also matter. Owners often require ASTM or SMACNA leakage tests for major runs. Adding clear pass/fail criteria and retest rules in the contract helps avoid disputes and speed closeout.When is leakage testing mandatory for commercial projects?
Many codes and project specs require leakage testing on conditioned duct systems or smoke-control systems. ASHRAE and local code adoptions often set limits. Owners should require ASTM E1554 or E783 tests where performance matters. State the accepted test method and the maximum allowable leakage in the specs. That prevents bidders from using low-seal methods and keeps final performance predictable.How does prefabrication reduce installed hours?
Prefabrication moves work into a controlled shop environment where quality and speed are higher. Prefab cuts field hours by 20–40% on long, repeatable runs. That reduces waste and the risk of field fitting errors. Use prefab for long straight runs, repetitive transitions, and multi-floor stacks. Ask for prefabrication schedules and mockups so you know what arrives on site and when.What tests verify duct tightness and explain results?
ASTM E1554 and E783 are common test methods. Results report leakage as cubic feet per minute per 100 square feet or as a percentage of system flow. Those numbers let you compare systems and set acceptance criteria. Interpret results against your contract limits. A small cfm number may seem fine, but it could still raise fan energy. Ask your mechanical engineer to translate leakage numbers into expected fan energy impacts. (ASHRAE Technical Resources)How to specify acceptance criteria in contracts?
Specify a leakage class or a maximum cfm/100 ft2 per ASHRAE or SMACNA. List the test method, retest rules, and who pays for repairs. Attach a payment holdback tied to passing tests to align incentives. Also define the threshold for when the contractor can use repairs versus full replacement. Clear repair standards reduce arguing after failed tests and speed project completion.What documentation should contractors provide?
Require shop drawings, test reports, insulation certificates, and as-built centerline footage. Those deliverables speed commissioning and closeout. Insist that reports show who performed the test and their equipment calibration dates. Make a checklist of required documents in the contract and hold a portion of final payment until they are delivered. That ensures you get the records that protect system performance.Ready to reduce duct bid waste?
Start by using baseline per-foot bands for quick screening. Then require line-item bids, shop drawings, and a clear testing plan. That process cuts low bids that miss scope and reduces surprise change orders once work starts. If you need help, get a cost review before you award work. A short third-party check of takeoffs and test criteria often saves far more than its fee. Use that review to tighten specs and set fair acceptance rules.How to request a cost review from a pro?
If you are in Las Vegas, Henderson, or North Las Vegas, call The Cooling Company at 17029308411 for a duct cost review, line-item bid check, and leakage test plan. Staff will give a written checklist and suggested contract language to reduce bid waste and rework. Outside our service area? Ask any bidder for NATE-certified technicians, a clear line-item breakout, ASTM test methods, and shop drawings. That checklist helps you compare bids and find contractors who meet commercial standards.What should you look for in a bid before you sign?
Check that bidders separate shop fabrication from field labor and list fittings, hangers, and insulation. Verify the specified leakage limits and who pays for retests. If a bid hides key items, question whether price risk is being shifted to you. Also verify references and recent project photos. Look for proof of similar work, prefab capacity, and test results. A contractor who shows past test reports and shop samples likely knows how to hit spec and reduce rework.How to protect yourself from cost overruns?
Include holdbacks tied to testing and required deliverables. Keep a contingency line and demand clear repair responsibilities for failed tests. Approve shop drawings before field work so most problems are solved in the shop. Track change orders closely and require itemized pricing for each change. That keeps costs transparent and stops small field fixes from growing into large unbudgeted items.Final action for Las Vegas area owners?
Call The Cooling Company at 17029308411 to book a commercial duct cost review and prefabrication plan. The team serves Las Vegas, Henderson, and North Las Vegas and will provide a written bid checklist, test criteria, and shop drawing review. If your project is outside those cities, ask bidders for NATE-certified technicians, ASTM leakage testing, and detailed shop drawings. Those items help you achieve predictable costs and lower long-term operating expense.About The Cooling Company
The Cooling Company has been serving the Las Vegas valley with professional HVAC services for over a decade. Our team of licensed, NATE-certified technicians specializes in air conditioning repair, heating system maintenance, and complete HVAC installations. We're committed to providing honest, reliable service with upfront pricing and a 100% satisfaction guarantee on all work performed.- Phone: (702) 930-8411
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