Please read a copy of the proposed amendment to DW 144 insulation section and submit your comments below.

30 THERMAL INSULATION

30.1 Provision and application
The provision and application of thermal insulation to ductwork is not normally the responsibility of the ductwork contractor. The information in this section is provided for general guidance only and more detailed information on thermal insulation can be obtained from TIMSA (Thermal Insulation Manufacturers and Suppliers Association) and TICA (Thermal Insulation Contractors Association ) both of whom have jointly provided the information in this section.

30.2 Insulation categories
Ductwork systems distribute chilled, warm or dual-purpose chilled or warm air. Where ductwork is required to be insulated before installation, the specification should be agreed with the designer and be in compliance with the Building Regulations Approved Document L – Conservation of Fuel and Power to standards not less than those set out in the Non-domestic Heating, Cooling and Ventilation Guide. The stipulated maximum heat loss/gain limits should be calculated in accordance with BS EN ISO 12241 using the standardised assumptions contained within the document. TIMSA publish an HVAC Guide as assistance to achieve Part L compliance.
Insulation should be installed within the guidelines given in BS 5970:2001 Code of practice for thermal insulation of pipework and equipment (in the temperature range –100ºC to +870ºC)

30.3 Non-metallic pre-insulated ductwork
Non metallic pre-insulated ducts should be in accordance with BS EN 13403:2003. Non-metallic ducts pre-insulated must have a minimum fire classification of Class 0 (to BS476: Part 4, 6 and 7) to satisfy the Building Regulations Approved Document B Fire Safety. These standards are for both on-site and off-site fabrication. Thermal insulation of pre-insulated ductwork should comply with the Building Regulations Approved Document L as per clause 30.2

30.4 Condensation and vapour sealing
Where the temperature of the air within the duct is at any time low enough to promote condensation on the exterior surface of the duct and cause moisture penetration through the thermal insulation, vapour sealing may be called for, and in this case the most important requirement is to limit penetration of the seal.

The extent of any vapour sealing of ductwork and the support method to be used must be clearly specified in advance by the designer.

For cooled systems, it is also important to ensure that the risk of condensation is adequately controlled. For guidance on controlling condensation reference should be made to both BS 5422: 2009 and the TIMSA HVAC Guide.

Care shall be taken to ensure that the integrity of any vapour seal is maintained and reference in this respect must be made to BS 5970:2001.

30.5 External ductwork
Some commonly used systems used to weather protect foil faced mineral wool slab (glass or rock ) are black PIB sheeting (polyisobutylene) or aluminium cladding, although other proprietary weatherproof jacketing systems are becoming more common such as Fibre Reinforced Plastics ‘FRP’

PIB sheeting is acceptable and economical in ‘protected’ areas, i.e. away from birds, foot traffic and strong sunlight. The problems that can occur in ‘unprotected areas’ are as follows:

• Bird attacks which penetrate both PIB and foil vapour barrier leading to water ingress, and reduced thermal efficiency.
• Exposure to foot traffic to access other parts of roof areas can cause the PIB to split – again leading to water ingress and loss of thermal efficiency.
• Water ingress may not initially be apparent but eventually the weight of the saturated insulation below a duct can cause delaminating of the PIB sheeting. Remedial works could involve not only removing the cladding and insulation but also the ductwork
• If the vapour barrier is breached, ductwork condensate causes further breakdown
• Leakage of air from the ductwork can cause insulation damage and degradation as the cover becomes ‘bloated’ and susceptible to breaking up.
• Ductwork corrosion can occur due to exposure to moisture
• Energy costs and carbon emissions can increase due to inefficient insulation.

Aluminium cladding is a more rigid protective finish than PIB, less susceptible to bird damage but more expensive. Even so, problems that can occur in ‘unprotected areas’ are as follows:
• If top surface is exposed to foot traffic, seams can open and allow water ingress. This causes many of the problems previously highlighted for PIB
• If the top surface is dented in any way, water pooling could occur

30.6 Practical issues
TICA members are sometimes faced with problems which could be avoided if the design and project teams addressed some of the following issues before the ductwork is installed:
• Lack of services co-ordination, mainly in builders work risers and plant areas, results in conditions that are difficult to meet the established standards for ductwork insulation.
• Ductwork installed too close to the fabric of the building and in particular roof levels results in conditions that are make it impossible to meet the established standards for ductwork insulation, with the exception of pre-insulated ductwork which can be installed directly any surface level.
• In restricted areas, not enough consideration given to insulating ductwork either prior to insulation or progressively during installation.
• Lack of attention to the selection of support members and the subsequent affect on issues such as vapour sealing, support collapse.
• Alternative proprietary methods to PIB sheeting and aluminium cladding on external ductwork

TICA themselves should be approached as they and their members can provide guidance in order to eliminate many of the issues listed above.

Tags: Manufacturers and Suppliers, Thermal Insulation, TICA, TIMSA

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