A key design objective of modern residential, commercial and industrial facilities is to incorporate a concern for energy consumption, as well as occupant comfort and safety. A lot of investigations about the comfort of residential buildings and industrial facilities show that the large part of the claims are due to the excessive sound level of the HVAC systems .


An incorrect design and an inadequate installation procedure are usually responsible for the generation of a unacceptable sound level. In an HVAC system, the noise is normally produced by the fans and by the turbolence of air that flows through the ducts. Due to the flexing of the metallic walls, the pressure variations of the air inside the duct produce vibrations, causing mechanical energy is to be radiated outside as sound energy.


A healthier, more productive and more attractive environment depends in large part on a well-designed and properly-insulated HVAC duct systems. Carrying air to conditioned spaces inhabited by people, sensitive equipment, or a combination of both. The advent of enhanced Indoor Air Quality (IAQ) has influenced engineers to 1) keep interior ducts free of foreign materials that bring fibers into the air stream or support mold growth, and 2) address sound reduction mechanically through deflection and other methods. However, not using interior insulation results in increased transferred noise, energy loss, and higher cost solutions.



As far as the “breakout” noise reduction in ducts, the acoustic performance of an insulation material can be categorized into two mechanisms: noise absorption and sound insulation. For duct lining applications, the primary acoustical goal of the insulation is to achieve noise reduction through the absorption of incident sound waves. The peculiar semi-closed cell structure of the K-FONIK OPENCELL 240 is properly designed to increase the percentage of sound absorption. The sound absorbption coefficent (α), that qualifies the performance of an acoustic insulation product is, infact, strictly dependent from the flakes dimensions and from the empty-full ratio in the material structure.

The second mechanism involved in sound insulation phenomena is strictly related to the mass of the material in that the higher the mass, the higher the performance. K-FLEX OPEN CELL 240, with a density of 240 kg/m3 affords an Rw value of 14dB Moreover it should be noted, that insulation, when adhered to the duct, affords also reduce noise created by vibration from the walls of the duct, changing the inertial characteristics of the metals sheets.

Studies show that commercial buildings spend more than half of the energy use on maintaining the conditioned temperature. To control this, thermal insulation is commonly used to reduce energy consumption of HVAC systems and equipments. The characteristics of K-FLEX OPEN CELL 240 as thermal insulation material offer an effective aid to the control of heat gains and losses in HVAC duct lines, with a sensible reduction of the heat flux to the walls. The interior duct insulation with K-FLEX OPEN CELL 240 is also useful to reduce problems due to the presence of heat bridges often observed in duct support.


For an insulation material installed inside of a ductwork, all the aspects related to the Indoor Air Quality (IAQ) have to be considered, of course, with extreme attention. As well as ensuring that the air passing in the plant does not contain fibers or dust, the insulation materials have to avoid the formation of moisture and condensation inside the ducts, but above all a good ductwork insulation material should not promote the bacterial proliferation. For all the reasons above, where it is necessary to insulate the ducting from inside, elastomeric products are preferable to fibrous ones. As proved by a study conduced by the Rubber Research Institute of Malaysia (cf. Amir-Hashim, “The Environmental Advantage of Natural Rubber Latex products” Malaysian Rubber Board) the NBR rubber based materials and bacterial proliferation appear to be “biologically recalcitrant”. This is also confirmed by other problems in ductwork due to sources: a stydy from the University of Munster, Germany (cf. Alexander a wrong insulation solution. Lions Alexander Steinbuchel, Institut für Mikrobiologie, Westfälische Wilhelms-Universität Münster, “Biodegradation of natural syntetic rubber”). The resistance of K-FLEX NBR-based products has also been repeatedly proven by testing to ASTM G21 Standard, confirming that there is a little or no fungal growth even without using any special antimicrobials additives.