| Five Things Wrong with Commercial Rooftop HVAC Ductwork|
|Nearly every commercial building has HVAC (Heating, Ventilation, Air Conditioning) equipment, especially ductwork, on the roof. This ductwork is easy to ignore--unless you're a building superintendent responsible for managing the costs of operating the building. Increasing operational costs, the growing need for energy conservation, and air quality concerns dictate that five serious and related problems with these systems need to be addressed.|
Short useful life. Normal fiberglass-and-mastic insulation systems last about three years before points of failure become significant. Low spots in the top surface promote ponding of rainwater. The mastic itself is subject to UV damage from sunlight. Birds are common residents of holes and cracks, and they make the problem worse by digging out areas for nesting, and depositing their droppings, which tend to be corrosive. Mold and insects like these weak areas, too.
Water incursion. Water is an excellent conductor of heat, as anyone who has accidentally used a wet towel for a hotpad can tell you. As soon as water gets through a crack in the mastic protecting the fiberglass insulation, the wet fiberglass loses most of its insulating ability.
Air exfiltration. The pressure inside ductwork causes air to leak out every opening, reducing air flow in the rooms being heated or cooled, and causing the equipment to run longer and harder. Imagine trying to water your garden with a hose full of holes.
Air contamination. Water in the insulation encourages growth of mold and mildew, which finds its way inside the ductwork. This can be a serious problem in certain applications such as hospitals.
Poor insulation. Wet and torn insulation allow warmth (and coolth) to escape at a greater rate than when the system was new. This makes the air handling equipment run longer, shortening its life and consuming more energy as it runs.
People responsible for building operational costs, particularly anyone attempting to reduce those costs and reduce the building's carbon footprint, need to address all of these weaknesses in traditional roof-top ductwork systems.
It's unfair to mention problems without suggesting a solution. The solution needs to be a system that lasts a long time without failure, and require little or no maintenance. It needs to insulate the ductwork well, keep out water, reduce air leaks, and discourage the growth of organisms that can contaminate the conditioned air.
One innovator developing this kind of green technology is a company in Newark, Delaware. They have invented a rooftop duct insulation system that addresses every one of these problems. The product is called Techna-Duc, and the company is PTM Manufacturing LLC. Techna-Duc is a means of enclosing the original ductwork with aluminum-clad polyisocyanurate foamboard in a manner that prevents leaks, keeps out water, mold and critters, reduces air leakage, and is guaranteed for 20 years.