Single Wall Insulated Spiral Pipe
Dual and Single Wall Insulated Spiral Pipe
The first task of the HVAC engineer is to design a balanced system that efficiently delivers the requisite volume of conditioned air throughout the building and to the various spaces within the building according to their individual needs. This requires the selection and sizing of primary heating, cooling, and other mechanical equipment, the layout and sizing of ducts, the number, location, and design of diffusers and registers, and many other calculations.
However, many commercial HVAC applications have additional requirements related to thermal efficiency and noise reduction, which significantly influence long-term energy costs as well as productivity—in other words, the cost of ownership. If these additional requirements are not defined in advance, and carefully factored into the original system design, expensive system modifications and retrofitting may be required at a later date. One of the most reliable, efficient, and low cost methods of increasing thermal efficiency and reducing noise without dramatically affecting overall system design is the specification of dual-wall or single-wall insulated Spiral Pipe.
Benefits Of Insulating Spiral Pipe
Material and installation costs are basically one-time costs, which are amortized over a relatively short period of time, and periodic maintenance costs can be expected with any mechanical system. However, poor or inadequate insulation can result in significantly higher, long-term energy costs, which only increase over time with each increase in the cost of fuel and invariable swings in ambient temperatures.
Uninsulated or poorly insulated heating or cooling runs thru spaces with a high ambient temperature differential can give up significant amounts of heat energy to the environment. Inadequate duct insulation may also require an increase in the size of heating and cooling units, causing them to work above of their most efficient operational range, increasing their maintenance requirements and hastening their eventual replacement.
Finally, uninsulated or inadequately insulated duct on cooling runs thru spaces with high ambient humidity will result in significant condensation, causing expensive damage to other building components (such as ceiling tiles and drywall). This promotes the growth of unhealthy mold and bacteria (which are costly to eliminate), and further reduces the effectiveness of the duct insulation itself.
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, communications, health, and productivity. It is difficult to put a dollar figure on this, but it is a continuing cost that can be 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 passing through ducts, fittings and registers. But a duct system is also and ideal conduit for transmitting noise from sources outside the HVAC system.
Flanking Noise: An HVAC duct system is an ideal conduit for transmitting noise from sources outside the HVAC system. Uninsulated, or poorly insulated ducts, can pick up and transmit noise from the spaces the duct passes through. For example, ducts that pass through mechanical equipment rooms or equipment rooms or… manufacturing areas will pick up ambient noise and transfer it to office and other work areas.
Cross-Talk Noise: Any opening in the duct system such as registers allow extraneous noise to directly enter the duct system and be transmitted to other rooms through their respective registers. Such noise is not only distracting, but it can adversely affect privacy and confidentiality the designer might want to consider in the initial planning stages.
Basic Methods For insulating Spiral Pipe
External, or Blanket Insulation, for Single-Wall Spiral Pipe
External, blanket-type insulation (often called duct wrap) consists of fiberglass mat with a thin vapor-barrier (foil or plastic) on one side. It is installed by the contractor, and it is the least expensive insulation option in terms of material cost. However, installation is labor intensive, and success depends on craftsmanship and attention to detail. The insulation must be cut and fitted fairly precisely to avoid gaps and reduce sagging on both horizontal and vertical runs. Joints must be sealed with tape or mastic, and special care must be taken to seal 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, and, if the vapor barrier is compromised, condensation and its related problems can result.
Interior Insulation (Duct Liners) for Single-Wall Spiral Pipe
Spiral Manufacturing offers several factory-installed options to internally insulate single-wall spiral pipe using insulation (duct liners) engineered specifically for this application. Since this type of insulation is within the air stream, it must be designed to minimize insulation particulates from entering the air stream, and to prevent the formation of molds and bacteria. Additional considerations are air velocity and air temperature. Above a velocity of 6000 feet per minute the surface of the insulation can be compromised and particles can enter the air stream. Temperatures above 250°F 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) performs well in terms of thermal efficiency and noise reduction.
Dual-wall spiral pipe comprises two concentric pipes of slightly different diameters (generally 1″ to 2″) with factory installed insulation filling the space between the pipes. While it is more expensive in terms of material costs, it offers several advantages over other insulation methods. Unlike external, blanket-type insulation, dual-wall insulation is factory installed, eliminating the need for labor-intensive, on-site fabrication—the process of cutting and fitting insulation, and sealing longitudinal and traverse joints with tapes and mastics. And, since the outer pipe is metal, it protects the insulation, and forms a durable vapor barrier that is not compromised by pipe hanging hardware.
Unlike with single-wall, interior insulation (duct liners), the inner pipe protects the insulation from gradual erosion from the air stream and contains any particulates from entering the air stream. This allows for higher air speeds, and makes duct cleaning easier—special cleaning methods are not required. Dual-wall, insulated Spiral pipe can handle significantly higher air temperatures.
For noise reduction applications, the interior pipe is perforated with thousands of 3/32-inch holes, which progressively reduce downstream noise and still protect the insulation from air stream erosion.
