Portable HVAC ducting provides temporary climate control in situations where permanent ductwork does not exist, has failed, or is not practical. From construction sites needing temporary heat to prevent concrete freeze damage, to outdoor events requiring climate-controlled tents, to data centers needing emergency cooling during HVAC failures -- portable ducting is the bridge between the climate control equipment and the space that needs conditioning.
Unlike permanent HVAC installations, portable ducting prioritizes rapid deployment, flexibility, and reusability over aesthetics and long-term durability. This guide covers the duct types, sizing methods, and deployment techniques for the most common portable HVAC applications.
Portable Duct Types and Materials
Portable HVAC ducting uses flexible duct materials that can be quickly deployed, repositioned, and stored when not in use. The primary options:
| Duct Type | Temp Range | Weight (12" x 25ft) | Best For |
|---|---|---|---|
| PVC-coated nylon | -4F to +248F | ~8 lb | General portable cooling/heating, construction sites |
| Layflat polyester | -4F to +180F | ~5 lb | Event tents, temporary offices, disaster recovery |
| Insulated layflat | -4F to +180F | ~12 lb | Outdoor runs exposed to sun, long duct runs |
| Canvas fabric | -4F to +180F | ~10 lb | Portable blower connections, heavy-duty temporary ventilation |
| Silicone fabric | -65F to +550F | ~15 lb | Portable industrial heat ducting, engine exhaust |
Layflat duct is the most popular option for temporary HVAC because it collapses flat when the air system is off, making it easy to store, transport, and deploy. When the blower runs, air pressure inflates the duct to its full diameter. Standard layflat duct is available in 8-inch to 36-inch diameters and lengths up to 100 feet.
Application 1: Construction Site Climate Control
Construction sites need temporary HVAC for three primary reasons: worker comfort (OSHA heat stress prevention and cold weather protection), process requirements (concrete curing, drywall drying, paint drying), and material protection (freeze prevention for plumbing and finishes).
- Temporary heating. Portable direct-fired or indirect-fired heaters connect to 12-24 inch layflat or wire-reinforced duct to distribute warm air through the building under construction. For freeze protection of concrete, maintain a minimum 50F ambient temperature for 72 hours after pour.
- Summer cooling. Portable spot coolers (1-5 ton) and larger temporary AC units (5-25 ton) connect to 12-18 inch insulated layflat duct to deliver cooled air to work areas. Insulated duct prevents condensation on the exterior in humid conditions.
- Sizing: For a 5-ton temporary AC unit (2,000 CFM), a 16-inch duct delivers air at approximately 1,400 fpm -- acceptable for temporary applications where noise is not a primary concern. For a 25-ton unit (10,000 CFM), multiple 24-inch ducts or a single 36-inch duct is required.
- Deployment tips: Route duct along walls and floors, not through high-traffic areas. Use sandbags or duct anchors to prevent wind from blowing the duct out of position. Protect duct from foot traffic and equipment traffic with ramps or overhead routing.
Application 2: Special Events and Tents
Outdoor events, wedding tents, corporate events, and temporary structures need climate control during hot summers and cold winters. Portable AC and heating units connect to the tent structure through flexible ducting.
- Sizing rule: 1 ton of cooling per 200-400 sq ft of tent area, depending on occupancy, sun exposure, and geographic location. A 40x60 tent (2,400 sq ft) needs approximately 6-12 tons of cooling capacity.
- Duct layout: Run main ducts along the tent ridgeline with branch drops every 20-30 feet for even distribution. Use layflat duct for the main trunk and smaller wire-reinforced duct for branches.
- Aesthetics: White or clear layflat duct blends with tent fabric. Avoid industrial-looking metallic duct for client-facing events. Duct can also be routed under the tent floor with ground-level diffusers.
- Connection: Most rental AC units have round supply connections in 12, 16, 18, or 24 inch diameters. Use hose clamps or zip ties to secure layflat duct to the unit outlet. Duct tape is acceptable for temporary event connections (unlike permanent HVAC).
Application 3: Disaster Recovery and Emergency Cooling
When a building's permanent HVAC system fails, portable equipment and ducting provide emergency climate control within hours rather than the weeks or months needed for permanent repairs.
- Data centers. Server rooms that lose cooling can reach damaging temperatures within 10-15 minutes. Emergency portable AC units with 12-18 inch insulated duct are pre-positioned or rapidly deployed to maintain server temperatures below 80F until permanent HVAC is restored.
- Hospitals and healthcare. Patient care areas require maintained temperatures per CMS (Centers for Medicare & Medicaid Services) requirements. Portable cooling with insulated duct keeps patient rooms comfortable during HVAC emergencies.
- Post-disaster restoration. After flooding, fire, or storm damage, portable blowers and dehumidifiers use 8-16 inch layflat duct to direct dry air into affected areas for drying and mold prevention.
- Timing: The advantage of portable ducting is deployment speed. A trained crew can connect a portable AC unit and run 100 feet of layflat duct into a building in 30-60 minutes. Compare this to days or weeks for temporary rigid duct installation.
Application 4: Industrial Spot Cooling and Heating
Industrial facilities use portable ducting for spot cooling workers in hot environments and portable industrial heat ducting for process applications:
- Spot cooling. In foundries, welding shops, glass plants, and other hot-environment facilities, portable AC units with flexible duct deliver cool air directly to worker stations. OSHA recommends keeping worker core body temperature below 100.4F (38C) -- spot cooling is the most efficient way to achieve this in large, hot facilities.
- Process heating. Portable indirect-fired heaters with silicone fabric duct (rated to 550F) deliver hot air for paint curing, composite layup, concrete curing, and other temperature-sensitive processes. The duct must be rated for the air temperature at the heater outlet, which can exceed 300F.
- Confined space ventilation. Portable blowers with 8-16 inch nylon duct provide the fresh air ventilation required for confined space entry per OSHA 29 CFR 1910.146. See our industrial duct applications guide for detailed sizing.
Sizing Portable Ducting
Portable ducting follows the same CFM/velocity/area relationship as permanent duct, but with different velocity targets. Because noise is less critical in temporary applications, higher velocities are acceptable:
| Duct Diameter | CFM at 1,500 fpm | CFM at 2,000 fpm | Typical Portable AC Match |
|---|---|---|---|
| 8" | 523 | 698 | 1-2 ton spot cooler |
| 12" | 1,178 | 1,571 | 3-5 ton portable AC |
| 16" | 2,094 | 2,793 | 5-10 ton portable AC |
| 18" | 2,651 | 3,534 | 10-15 ton portable AC |
| 24" | 4,712 | 6,283 | 15-25 ton portable AC |
Duct Length Matters More for Portable
Portable ducting runs are often longer than permanent installations (50-200 feet from the portable unit to the served space). Each foot of layflat duct creates more friction than rigid or wire-reinforced duct. A portable AC rated at 2,000 CFM at the outlet may deliver only 1,200 CFM through 100 feet of 16-inch layflat duct. Always account for friction loss when sizing the duct diameter -- oversizing by one or two inches compensates for the long runs typical in portable applications.
Insulated vs Non-Insulated for Portable Applications
The insulation decision for portable ducting depends on the run environment:
- Indoor runs (conditioned or partially conditioned space): Non-insulated duct is acceptable. The temperature differential between the duct and the surrounding space is moderate, and the installation is temporary.
- Outdoor runs in sun: Insulated duct is strongly recommended. Direct sunlight heats the duct surface to 140-160F, warming the cooled air inside. Insulated layflat duct with a reflective outer surface reduces solar heat gain by 70-80%.
- Outdoor runs for heating: Insulation reduces heat loss but is less critical than for cooling -- the temperature differential is smaller and heat loss does not create condensation.
- High-humidity outdoor runs for cooling: Insulated duct prevents condensation dripping on people and equipment below the duct. In Houston, Miami, or any humid climate, uninsulated portable cooling duct will drip condensation continuously.
Deployment Best Practices
Tips from experienced portable HVAC contractors:
- Keep runs as short as possible. Every 10 feet of duct reduces delivered CFM by 5-10% due to friction. Position the portable unit as close to the served space as possible.
- Avoid crushing the duct. Layflat duct collapses under foot traffic, vehicle traffic, and stored materials. Route away from traffic paths or protect with ramps and covers.
- Secure the duct. Wind can blow lightweight layflat duct off position. Use sandbags, stakes, or duct anchors every 10-15 feet on outdoor runs.
- Seal the end. If the duct terminates in an open space (like a tent), attach a diffuser nozzle or register to distribute air evenly. An open duct end creates a jet of cold/hot air that creates discomfort near the end and leaves the rest of the space unserved.
- Check connections hourly. Temporary connections with hose clamps and zip ties can work loose as the duct expands and contracts with temperature changes. Inspect all connections at least daily, hourly in critical applications (data centers, healthcare).
For portable AC exhaust hose replacement and sizing, see our portable AC exhaust hose guide covering 5-inch vs 6-inch sizing, heat-resistant materials, and how to reduce hot air leakage.