Insight

Heat loss calculations

One of the most common questions OFTEC’s technical team receives from technicians when installing a liquid fuelled heating system that is either part of a new system, or is a replacement component, is “what calculation method can, or should, I use?”

A recent survey showed 50% of OFTEC registered technicians were not aware of the recent changes made in England to Approved Document Part L (ADL).
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A recent survey showed 50% of OFTEC registered technicians were not aware of the recent changes made in England to Approved Document Part L (ADL). So firstly, we will provide some information about regional changes.

The changes made to ADL came into effect on June 15th 2022, whereby six documents were split into two Building Regulation 2010 Approved Document Part L volume 1: Dwellings and volume 2: Buildings other than dwellings.

The following text from the current Approved Document L, V1 (England), states:

Sizing space heating systems

5.8 The specification of space heating systems should be based on both of the following.

  1. An appropriate heat loss calculation for the dwelling.
  2. A sizing methodology that takes account of the properties of the dwelling, such as the CIBSE Domestic Building Services Guide.

Systems should not be significantly oversized.

Sizing domestic hot water systems

5.11 Domestic hot water systems should be sized for the anticipated domestic hot water demand of the dwelling, based on BS EN 12831-3 or the Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide. Systems should not be significantly oversized.

NOTE – For temperature limits to control legionella bacteria in domestic hot water systems, see Approved Document G.

This means that methods previously used, such as the whole house boiler calculation method CE54, are no longer acceptable and a suitable calculation, based on the aforementioned, should be used.

A room-by-room heat loss calculation is important for demonstrating that the system is not significantly oversized and will provide compliance. A record of this must be retained by the installer and a copy provided to the customer.

In relation to the question “what calculation method can, or should I use?”, There is no one answer to this question. Industry professionals, manufacturers, software developers, and app designers are all currently creating tools to help technicians.

OFTEC would encourage technicians to:

  • Watch our webinar with Heat Engineer Software Ltd (available on the OFTEC website).
  • Familiarise yourself with the appropriate regional requirements (QR codes below).
  • Pursue further training on heat loss and low-temperature heating design courses.
  • Obtain a copy of the Domestic Heating Design Guide.
This article originally appeared in the 2022 winter issue of Oil Installer magazine. View the magazine