AC Ducting in Small Spaces

Principles that keep small space AC comfortable

Tight interiors make airflow behave like traffic at rush hour. The path matters more than the distance. Begin with the equipment’s fan curve and set a static pressure budget that the ductwork must meet. In compact layouts, total external static pressure often needs to stay low, so the duct system must be smooth, short, and free of sharp transitions. Oversized grilles and diffusers reduce face velocity and sound. Place supplies where heat appears first such as sun side glazing or near cooking zones and position returns to pull across the occupied area rather than short cycling back to the unit.

Supply and return planning

Every cubic foot of air supplied needs an easy way back. In tiny rooms and van cabins, a generous return path avoids whistling and pressure imbalance. Use a return that is roughly ten to twenty percent larger in free area than the combined supply outlets. Keep the return away from immediate supply throw to prevent recirculation and improve dehumidification.

Sizing, routing, and pressure control in tight runs

Right sizing starts with the manufacturer’s airflow requirement in cubic feet per minute and the acceptable pressure range. In many small systems, expect about 300 to 400 CFM per ton, then adjust using the equipment chart. Translate that airflow to duct diameter using friction rate tables, not guesswork. Favor larger, smoother ducts with fewer fittings to hold the friction rate down. Use long radius elbows whenever possible and avoid crushed or kinked flexible ducts. Each fitting adds equivalent length, so count it carefully and keep the total in check.

Quiet is a design decision

Noise in compact spaces stands out. Lower face velocity at diffusers reduces hiss. Acoustic duct liner, lined plenums, or short lengths of flexible duct used as a decoupler can damp fan noise, but avoid long flexible runs. Add balancing dampers near takeoffs rather than choking the diffuser itself. Isolate the air handler with vibration pads and ensure the return is large enough to prevent intake roar.

Materials, insulation, and moisture management

Rigid round duct offers the least friction for a given size and holds shape in cramped chases. Ovalized round can tuck into shallow cavities without a big penalty. Flexible duct is helpful for final connections but only when fully stretched and supported to prevent sag. Whatever the material, insulation and vapor control are non negotiable in small, humid environments. Closed cell insulation or jacketed duct with intact vapor barrier stops condensation. Seal all seams with mastic or approved tape so the outer jacket remains unbroken.

Condensation control and details that matter

Cold air through warm cavities invites condensation. Maintain continuous insulation, avoid compressing the duct, and keep cold surfaces isolated from humid room air. Slope horizontal supply trunks slightly to prevent water from pooling if moisture ever forms. In vehicles and tiny structures, protect ducts near exterior metal to prevent thermal bridging. Choose diffusers with a throw pattern that clears obstacles and delivers air across the room without drafts.

Balancing the system for even comfort

Small spaces still benefit from simple zoning. If there are distinct areas such as a sleeping nook and a galley, split the supply with separate branches and include balancing dampers to tune airflow. Measure temperature and noise at the seat, bunk, or desk rather than only at the unit. A brief test with a hood or anemometer to verify outlet airflow will save time and frustration. If a branch is starved, reduce resistance by opening dampers on that path before increasing fan speed. Fan speed changes should be the last step after the ductwork meets the pressure target.

In mobile cabins and compact vans, routing often lives in ceiling chases and furniture cavities. Keep bends gentle, avoid squeezing flexible duct behind panels, and anchor supports so the shape stays true. Short, direct, insulated, sealed, and balanced remains the recipe for quiet comfort.

OZK Customs builds this thinking into real interiors. Our team routes compact trunks with long radius turns, sizes outlets from performance data, and hides plenums cleanly so cabins feel cool without the racket. If you want a turn key solution, explore our Recreational vans to see how airflow planning fits into complete builds. For a fully tailored cabin, review our Custom build vans page, or if you prefer a finance friendly platform, see Mainstream vans.

Ready for smooth, quiet airflow

Small spaces reveal every mistake and reward good planning. Choose an honest static pressure target, size ducts from real charts, protect the vapor barrier, and balance the branches for an even, low noise climate. That is how you get calm, dry air where you sit and sleep.

At OZK Customs in Fayetteville, we design compact air paths that work. Whether you need a complete custom van or a partial upfit with refined ducting and electrical integration, we build for comfort, durability, and clean service access. Tell us how you travel and we will turn it into a cabin that breathes.

Strong next steps

• Share your priorities and timeline
• We will map a clear airflow plan
• You will drive away with quiet, even cooling

Final step Use the form below to start your build with OZK Customs. Airflow should be felt, not heard.