BUILDING INSULATION


Insulating HVAC systems – the importance of correct specification


Will Wigfield, product manager for HVAC and Fire Protection at Rockwool, explains why insulating HVAC systems is important and how to choose the right solution


T


he goal of thermally insulating HVAC systems is to reduce heat transfer, which saves energy and ensures the efficient operation of building services. Ducts and pipes, when in operation, can also be


very noisy. Appropriate insulation can reduce the noise by providing acoustic absorption. Insulation of HVAC systems is governed by building regulations and British Standards. In England, the guidance to the Building Regulations provided in Approved Document L describes the minimum provisions for the insulation of pipes and ducts serving space heating, hot water, chilled water and ventilation systems, in both new build and existing properties. BS 5422 provides methods for specifying


thermal insulating materials needed on pipes, tanks, vessels, ductwork and equipment for certain defined applications and conditions within the temperature range – 40°C to +700°C. It is meant to work as guidance for designers, specifiers, contractors and manufacturers of thermal insulation in the HVAC sector, supporting Approved Document L as the reference point to determine the minimum thickness of insulation required to conserve energy in building services.


Accurate calculations


The insulation thicknesses given in BS 5422 have been calculated using generic thermal conductivity values that correspond to common insulation types. Insulation manufacturers can assist projects seeking more accurate thicknesses by carrying out calculations using product-specific thermal data in accordance with ISO 12241. Note that the thermal performance of some insulation materials is known to deteriorate over time. As such an aged thermal performance is declared, which typically takes the form of a ‘time averaged’ lambda value over 25 years. Other materials, such as stone wool, have a thermal performance that does not change with time. This is important for specifiers and installers to keep in mind when deciding which material to use, based on the expected lifespan of the building or HVAC installation.


Rockwool has made selecting the optimum thickness of HVAC insulation quicker and easier, with the development of an online calculator - ROCK-EQ. Purpose designed for mechanical


engineers, consultants and insulation installers, the calculator produces detailed, project-specific calculation reports and recommendations in a matter of minutes. The tool provides extensive calculation options. Users enter basic information about their specific site conditions and performance requirements, and tool calculates the optimum thickness based on the insulation product selected. The calculator can be used to specify solutions for a range of requirements, including condensation control, heat gain or loss, personnel protection, and protection against freezing.


Avoiding thermal bridging


Important to consider, but often overlooked when it comes to thermal performance, are pipe supports and fixtures. Pipe support systems require a loadbearing material to be installed between the support and the pipe surface, and as per the guidance in BS 5422, this material should also be insulating. Traditionally, wooden blocks have been used for this purpose; however, these provide little to no thermal benefit, and are not suitable for use where there is a requirement for non- combustibility.


More recently, insulated pipe supports made from non-combustible stone wool have been introduced, thereby providing a thermal performance while also minimising any increase to the fire load of the system.


Safety first


Inappropriate combustible insulation materials can cause a fire risk. The ducts and pipes of HVAC systems reach every corner of the building, their route often hidden from direct view. Fire could spread a long way through the system before being discovered. Effective fire-resilient insulation acts as a barrier between ducts, to slow down or prevent the passage of flames and smoke around the building. However, thermal HVAC insulation manufactured


from stone wool is non-combustible. It will not provide a medium for fire spread or significantly add to the fire load of the HVAC system. Specialist insulation like DuctRock® is EN-tested


to provide ductwork systems with a fire resistance period of up to two hours.


Fit for the future


For new installations, the results are best if HVAC insulation is part of the plans and design from the outset. Existing HVAC installations, provided they are in good working order, can be refitted with insulation. This will achieve the same benefits and can be more cost-effective than replacing the whole system. It is important that the insulation product is specified correctly for the individual application. To help ensure optimum performance that continues for the lifetime of the building, insulation should be installed by approved specialist TICA-accredited contractors. Installing insulation that is fit for purpose and safe helps to protect lives, reduces the carbon footprint of the building and creates a comfortable environment for its occupants.


6 BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2023 Read the latest at: www.bsee.co.uk


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