UK Market Update 14 March 2025

EcoDuct Pre-insulated Ductwork and Alignment to Building Regulations Approved Documents Parts F and L

Approved Document F:2021 - Ventilation

Legal requirement:

The legal requirement reported in AD Part F is that ventilation shall be adequate and that mechanical ventilation systems shall be commissioned.

Guidance:

The guidance for mechanical ventilation systems is that appropriate design (i.e. correct air conditioning design and correct duct sizing and duct routing through the building) shall provide:

·     The required ventilation rates

·      Acceptable level of noise 

·      Acceptable level of pressure losses through the duct

In effect, all the above has to do with correct duct sizing and duct design – regardless of the type of ductwork used, sheet metal or pre-insulated.

 The guidance for air ductwork is:

·     Use rigid ducts wherever possible (as opposed to flexible ducts)

·     Seal ductwork to prevent leaks

·     Commissioning of mechanical ventilation systems

·     Provide access for maintenance 

Conclusion:

For all the guidance, pre-insulated ductwork is a suitable solution and fully aligned to the criteria and EcoDuct, with particular advantages i.r.o. the reduced use of flexible ductwork and no requirement to seal the ductwork as it does not leak (Class D at 2,500 Pa – refer Table and Graph below).

Approved Document L:2021/2023 - Conservation of fuel and power

Legal Requirement:   

L1. Reasonable provision shall be made for the conservation of fuel and power in buildings by:   

·     limiting heat gains and losses (…) from pipes, ducts and vessels used for space heating, space cooling and hot water services. 

·     providing fixed building services which are energy efficient to a reasonable standard (...) and are commissioned by testing and adjusting (...) their efficient use of fuel and power. 

Guidance 1:

·    Ductwork that carries warm or cold air should be insulated throughout its whole length to achieve heat transfer no greater than that given in Table 4.6.

·     Condensation should also be controlled. 

·     Consult BS 5422 as necessary. 

Approved Document L states that the requirements of Part L can be met when the heat transfer from the ductwork does not exceed the limits specified in BS5422:2023 tables 12-14. This calculation should be performed for each project, keeping in mind that the conditions outlined in BS5422 are standardised and may vary from project to project. 

 Guidance 2

.    Ventilation ductwork should be made and assembled so as to be reasonably airtight. 

·    Ductwork should comply with the air tightness specifications in either of the following: 

o   BESA’s DW/144.

o   BS EN 1507.

o   BS EN 12237.

o   BS EN 13403. 

 Further guidance on Air leakage testing of ductwork:  

·     8.10 - for ducted systems that are served by fans with a design flow rate greater than 1 m3 /s, ductwork leakage tests should be carried out. Tests should follow the procedures in the Building and Engineering Services Association (BESA) documents DW/143 and DW/144.

·     8.11 - for low-pressure ductwork, if at least 10% of the ductwork is tested at random and achieves the low-pressure standard as defined by DW/143, a calculated improvement in both the building primary energy rate and building emission rate may be claimed. Details are given in the National Calculation Methodology Modelling Guide. 

 Conclusion:

For all the guidance, EcoDuct pre-insulated ductwork fabricated from KoolDuct phenolic insulation panels is a suitable solution, fully aligned to the criteria and meets the requirements of Table 4.6 and BS5422, with particular advantages i.r.o. insulation thickness and airtightness (see table below).