Inadequate duct insulation can result in significantly higher long-term energy costs. Uninsulated or poorly insulated heating or cooling ducts that run thru spaces with a high ambient temperature differential can give up significant amounts of heat energy to the environment or, in the case of cooling, absorb unwanted heat. To compensate, heating and cooling units will either have to work harder, or will need to be resized to meet the increased demand—both of which increase energy costs.
In addition, inadequately insulated duct on cooling runs thru spaces with high relative humidity or high dew points can result in condensation on external duct surfaces—leading to expensive damage to other building components (such as ceiling tiles and drywall), promoting the growth of unhealthy mold and bacteria (known health hazards which are costly to eliminate), and further reducing the effectiveness of the duct insulation itself.
Workplace noise in schools, offices, hospitals, and other commercial buildings is known to compromise worker focus, communication, productivity, and even health; and while it is difficult to assign a dollar value to these factors, they will be on-going, unless avoided with advance planning, improved system design and a well-insulated duct system.
System Noise: HVAC systems inherently generate noise from (1) the fan and other mechanical equipment that drives the air and pressurizes the ducts, and from (2) the noise of high-speed air as it passes through ducts, fittings and registers.
Flanking Noise: Uninsulated or poorly insulated ducts can pick up noise directly through the duct walls and transfer it, both up and down stream, throughout the system. For example, ducts that pass through mechanical equipment rooms or manufacturing areas will pick up ambient noise and transfer it to office and other work areas.
Cross-Talk Noise: Openings in the duct system, such as registers, allow extraneous noise to directly enter the duct system and be transmitted to other work areas through their respective registers. Such noise is not only distracting, but it can adversely affect privacy and confidentiality.
External, or Blanket Insulation, for Single Wall Spiral Pipe
External (blanket type) duct insulation consists of a fiberglass mat with a vapor retardant facing (foil or paper) on one side. The contractor installs it on-site, and it is the least expensive insulation method in terms of material costs.
However, installation is labor intensive, and the quality of the installation depends on craftsmanship and attention to detail. The insulation must be cut and precisely fitted by hand to avoid gaps and reduce sagging on both horizontal and vertical runs. Joints must be completely sealed with tape or mastic, and special care must be taken in sealing the unavoidable holes in the vapor retardant barrier caused by pipe mounting hardware. Since the insulation is fragile and exposed, it is subject to damage from a variety of mechanical agents, which increase the potential for condensation on cooling runs.
Interior Insulation (Duct Liners) for Single Wall Spiral Pipe
Spiral Manufacturing offers several methods to internally insulate single-wall spiral pipe using specially engineered insulation (duct liners) designed specifically for this application.
This type of insulation is installed under controlled conditions at the factory, and engineered to minimize insulation particulates from entering the air stream, and prevent the formation of molds and bacteria.
Additional considerations are air velocity and air temperature. Above an air velocity of 600 feet per minute the surface of the insulation can be compromised and particles can enter the air stream. Temperatures above 250ºF (121ºC) can also degrade the insulation.
A final consideration is duct cleaning. This must be done according the recommendations of the manufacturer of the insulation. Overall, interior insulation (duct liners) perform well in terms of thermal efficiency and noise reduction. Spiral Manufacturing offers standard solutions, but we have the flexibility to meet your special needs.
Dual Wall (also called Double-Wall) Insulated Spiral Pipe
Dual wall insulated spiral pipe consists of two concentric spiral pipes with insulation filling the space between the pipes. It is shipped from the factory with the insulation pre-installed, reducing job site labor costs. Also, without unsightly insulation, the system is much more aesthetically pleasing.
Unlike external, blanket type insulation, there is no cutting, taping, or sealing of the insulation, and, since the outer pipe is steel and also serves as the vapor barrier, there is little threat of mechanical damage to the insulation itself, or the vapor barrier.
Unlike interior insulation (duct liners), air velocity and high air stream temperatures do not damage the insulation; and duct cleaning does not require special methods to protect the insulation. For noise reduction applications, the interior pipe is perforated with thousands of holes, which progressively reduce downstream noise. The initial material costs of dual wall insulated spiral pipe are higher, but installation and maintenance costs are lower.