Ductwork Buyer's Guide for Kenyan Homes & Businesses

Why Ductwork Design Matters as Much as the Equipment It Serves

It's easy to focus entirely on the AC unit, ventilation fan or chiller when planning a project, but the ductwork distributing that conditioned air is just as important to real-world performance. Undersized, poorly routed or leaky ductwork can waste a significant share of a system's capacity before it ever reaches the rooms it's meant to serve — meaning even a premium, correctly-sized unit can underperform badly if the ductwork carrying its output wasn't properly designed.

Types of Ductwork Materials & Systems

Galvanized Sheet Metal

The most durable and common choice for commercial installations, galvanized ductwork holds its shape well over long runs and stands up to demanding environments, though it costs more and takes longer to install than some alternatives.

Fiberglass Duct Board

Pre-insulated and relatively quick to install, fiberglass duct board suits many commercial applications but is less durable than metal in high-traffic plant rooms or harsh environments.

Flexible Ducting

Useful for short connector runs and tight spaces where rigid ductwork is impractical, flexible ducting is quick and cheap to install but loses more airflow efficiency than rigid options, especially if runs are longer than necessary or poorly supported.

Insulated vs Uninsulated Ducts

Insulation reduces heat gain or loss along the duct run and prevents condensation forming on the outside of cold supply ducts — a detail that's easy to skip to save cost but expensive in wasted cooling capacity and potential water damage over time.

Sizing & Design Basics

Correct duct sizing balances airflow requirements against static pressure — undersized ducts force air through too small a passage, increasing pressure, noise and fan strain, while oversized ducts waste material cost and space without improving performance. This calculation should be based on your system's actual airflow requirements and duct routing, not a generic rule of thumb applied regardless of the specific building layout.

What Drives the Cost

• Material choice. Galvanized metal costs more upfront than fiberglass board or flexible ducting but typically lasts longer in demanding commercial settings.
• Duct run length and complexity. Longer runs, tight ceiling voids and multiple direction changes all add labour time and material cost.
• Insulation. Insulated ductwork costs more initially but reduces energy loss and prevents condensation-related damage over the system's life.
• Access constraints. Working within an existing building's tight ceiling voids or finished spaces costs more than installing ductwork during new construction.
• Sealing and balancing. Proper joint sealing and post-installation airflow balancing add a modest cost but meaningfully improve real-world efficiency.

Where Proper Ductwork Design Matters Most

• VRF and ducted AC systems, where duct design directly determines how evenly cooling is distributed across multiple rooms or zones.
• Commercial kitchen extract, where undersized or poorly sealed ductwork can allow grease buildup and reduce extraction effectiveness.
• Industrial ventilation, where airflow volume and duct material need to withstand dust, fumes or heat specific to the process involved.
• Hospitals and laboratories, where duct design affects airflow direction and contamination control, not just comfort.

Retrofitting Ductwork Into an Existing Building

Adding or modifying ductwork in a building that wasn't originally designed for it is meaningfully more complex than installing it during new construction — ceiling void space, structural obstructions and existing finishes all constrain what's possible. A proper site survey before quoting is especially important for retrofit projects, since routing decisions that look simple on paper often run into real obstacles once work begins, and a contractor without retrofit-specific experience is more likely to be caught out by these constraints partway through the project.