The primary objective of HVAC design is a balanced system that efficiently delivers the required volume of conditioned air to all of the building’s spaces. However, there are additional requirements, such as thermal efficiency, noise reduction, and condensation control that significantly influence long-term cost and productivity—and ultimately the cost of ownership. The most effective method of meeting these requirements is insulating the ductwork that delivers the conditioned air.
Benefits & Methods of Insulating Spiral Pipe
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 (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.
Dual Wall Insulated Spiral Pipe
Comprised of two concentric spiral pipes of different diameters with the intervening space filled with insulation (usually fiberglass), dual wall insulated spiral pipe is virtually airtight, and the insulation is protected from the four most common types of failure: job site damage, erosion due to high-pressure, turbulent airflows, and condensation. Since the insulation is factory installed, time-consuming and labor-intensive installation at the job site is eliminated.
Available in Perforated (Acoustical) Liner or Solid (Thermal Insulation) Liner
Duct liner absorbs equipment and air rush noises over a broad spectrum of sound. Glass fiber construction traps noise and dissipates it within the fiber matrix. Air is delivered, not noise. It also performs as a thermal insulation to conserve energy.
Additional benefits include increased fire safety due to the noncombustible nature of the metal duct, and mineral wool insulation is available which will withstand temperatures to 1000º F.
When noise reduction is required, the inner wall of dual wall spiral pipe is perforated with thousands of 3/32″ holes on 3/16″ centers. These holes effectively channel system noise, flanking noise and cross-talk noise into the insulation layer where it is absorbed. To reduce the possibility of insulation particles entering the air stream, the insulation is impregnated with an acrylic binding agent. Antimicrobial agents are commonly used to inhibit the growth of mold and bacteria, which can compromise indoor air quality.
Almost all of the fittings available for single wall spiral pipe are available for dual wall spiral pipe, giving the designer the same flexibility enjoyed with a single wall system. As with single wall spiral pipe, dual wall fittings are male and dual wall pipe is female, so simple, efficient, and economical slip-joint installation is available to the contractor for many, especially light commercial, applications. For higher pressure and larger diameter applications, there are several economical and proven flange connection methods. (Click on Installation tab above for installation instructions.)
Specifically designed as an interior insulation material for sheet metal ducts used in heating, ventilating and air conditioning, Sonic XP provides an optimum combination of efficient sound absorption and low thermal conductivity, as well as certification for indoor air quality as a low emitting product by the GREENGUARD Environmental Institute. It also features rapidly renewable bio-based materials rather than nonrenewable petroleum-based chemicals traditionally used in fiberglass insulation products. It contains no phenol, formaldehyde, acrylics or artificial colors.
|General Properties & Compliance|
|I-P Units||SI Units|
|Thickness (1.5 PCF)||1″, 1.5″, 2″||25mm, 38mm, 51mm|
|Thickness (2.0 PCF)||.5″, 1″||12.7mm, 25mm|
|Air Velocity (max.) ASTM C 1071||6000 fpm||1829 mpm|
|Service Temperature (max.) ASTM C 411||250ºF||121ºC|
|Microbial Growth ASTM C 1338, G21||Airstream surface mat facing is treated with an EPA-registered anti-microbial agent to aid in the prevention of fungal and bacterial growth. Does not promote or support the growth of mold, fungi or bacteria.|
|Co9rrosiveness ASTM C 665||Does not accelerate corrosion on steel, copper or aluminum.|
|Surface Burning Characteristics||UL/ULC classified. Does not exceed 25 Flame Spread, 50 Smoke Developed when tested in accordance with ASTM E 84, CAN/ULC S102-M88, NFPA 255 and UL 723.|
|Water Vapor Sorption||Less than 3% by weight.|
|Specification Compliance||IN US: ASTM C 1071; Type I / ASTM G 21 / GREENGUARD Indoor Air Quality Certified® / GREENGUARD Children & Schools Certified SM / NFPA 90A and 90B
IN CANADA: CAN/ULC S102-M88 / CAN/CGSB- 51.11-92
|Sound Absorption Coefficients (ASTM C 423, Type A Mounting)|
|Type||Octave Band Center Frequency (cycles/sec.)|
|1.5 PCF 1″ (24 kg/m3 25 mm)||.18||.36||.58||.86||.95||.90||.70|
|1.5 PCF 1.5″ (24 kg/m3 38 mm)||.35||.51||.83||.93||.97||.96||.80|
|1.5 PCF 2″ (24 kg/m3 51 mm)||.34||.64||.96||1.03||1.03||1.03||.90|
|2.0 PCF .5″ (32 kg/m3 13 mm)||.09||.14||.40||.60||.73||.82||.45|
|2.0 PCF 1″ (32 kg/m3 25 mm)||.25||.35||.69||.89||.96||1.01||.70|
|2.0 PCF 1.5″ (24 kg/m3 38 mm)||.274||.55||.87||.99||1.00||.98||.85|
* Coefficients determined per ASTM E 795 Type A Mounting. NOTE: ASHRAE Handbook for HVAC Applications – Sound and Vibration Control contains insertion loss values for lined sheet metal ducts.
|Thermal Conductance “C”* and Resistance “R”† (ASTM C 177)|
|Thermal Conductance “C”* and Resistance “R”†|
|Product||Conductance “C”||Resistance “R”|
|1.5 PCF 1″ (24 kg/m3 25 mm)||.24||(1.42)||.42||(.74)|
|1.5 PCF 1.5″ (24 kg/m3 38 mm)||.17||(.97)||6.0||(12.06)|
|1.5 PCF 2″ (24 kg/m3 51 mm)||.13||(.74)||8.0||(1.41)|
|2.0 PCF .5″ (32 kg/m3 13 mm)||.48||(2.73)||2.1||(.37)|
|2.0 PCF 1″ (32 kg/m3 25 mm)||.24||(1.36)||4.2||(.74)|
|2.0 PCF 1.5″ (32 kg/m3 38 mm)||.16||(.91)||6.3||(1.11)|
Standard Double Wall Duct Liner
Sonic XP® Duct Liner
Renewable bio-based, our standard duct liner insulation has a maximum temperature rating (ASTM C 411) of 250°F (121°C). Although zinc on galvanized metal melts at 788°F (420°C), the Manual of Industrial Ventilation Recommended Practice, 23rd edition, suggests that operating temperatures not exceed 400°F (205°C). Figure R-Value of duct liner per inch of thickness = 4.2 at 1.5 PCF.
High Temperature Insulated Spiral Pipe
Knauf Insulation ET Batt 1000°
Applications for Industrial Furnaces, paint and laminating ovens, panel systems or heating equipment. ET Batt 1000° used in conjunction with Aluminized Type 1 metal which offers a maximum temperature of 1000°F (538°C) or 304 Stainless Steel offering 1450°F (788°). Both Sonic XP and ET Batt 1000° products offer ECOSE® Technology and UL GREENGUARD certification validated to be formaldehyde free. Does not exceed 25 Flame Spread. ASTM C 1338 Microbial Growth Protection.
AccuFlange and WonderFlange are proven in economical systems that reduce job site labor. Job site labor can be further reduced by having Spiral Manufacturing install your flanges at the factory so they are ready to install when they arrive at the job site.
Double Wall Slip Joints
AccuFlange is a patented connection system, which, when installed and sealed per recommendations, is suitable for use on all systems across a wide range of internal duct from -10″W.G. to +10″W.G. It is available for both single wall and double wall pipe, and in a variety of materials. AccuFlange is easy and efficient to install, and reduces field labor. It is fastened internally to pipe and fittings with tack welds or Tek screws (eliminating the need to align bolt holes) and sealed with mastic. The mating flanges are then jointed with a gasket and Tek screws, or a Quick Draw clamp (see below).
WonderFlanges are the strongest (1/8″) and most economical connectors available for dual wall spiral pipe. Unlike angle rings, WonderFlanges are designed to slip inside the Spiral pipe, and are fastened to the pipe by welding, or with Tek screws using prepunched 9/32″ holes that do not need to be aligned. WonderFlanges can be used on 1″, 2″, 3″, or 4″ double wall Spiral pipe and fittings. Mild steel is the standard material. Galvanized and SS are available. Wonder-Flange rings are fused together at the factory and arrive at the jobsite ready for mounting.