Changes to Part L – Some Answers

From 6 April 2018, changes to the minimum requirements when installing boilers in existing buildings will become effective, in England only. The Domestic Building Services Compliance Guide is a vital reference document for installers, specifiers, enforcement authorities and market oversight bodies and will be updated to reflect the changes.

The key changes are:

Gas boiler performance: space heating efficiency of the new boiler no less than ErP 92%

Controls minimum: time and temperature control required for all gas and oil boiler installations

Combi boiler installations must also include one of the following:


In 2005 Approved Document L of the Building Regulations changed to require the installation of condensing boilers. Since then, there has been very little in the way of changes to minimum standards for heating installations.

In September 2015 the EcoDesign of Energy Related Products Directive (ErP) was introduced, which takes a more holistic view of heating system efficiency by recognising the impact of controls on the overall “package” of installed components, which was the initial catalyst for developing this policy.

The Department for Business, Energy and Industrial Strategy (BEIS) launched a consultation document in December 2016, and the subsequent policy changes concerning minimum requirements when installing boilers in existing buildings will be effective from 6 April 2018, in England only.

The changes are not only beneficial to efficiency and emissions but are also easily adopted, low cost and simple to factor into a boiler installation:

Frequently Asked Questions

Q What will happen if I don’t comply?

A Installers who don't comply are breaching the Building Regulations and are therefore breaking the law and could face prosecution. This is policed by Building Control, although Gas Safe Register can refer incidents of safety concern to the HSE. Furthermore, if an installer were to invoice a consumer for non-compliant work, it may be considered fraudulent and therefore open to action from Trading Standards.

Q What should I do if my customer doesn’t want the extra controls?

A The householder is also required to comply with the Building Regulations. Having non-compliant work carried out may result in prosecution and penalties up to £5000 for the homeowner.

Q Why are boilers rated differently for SEDBUK, SAP and ErP?

A Because the method of calculation for boiler efficiency is different for all three ratings.

Q What is FGHR?

A Flue Gas Heat Recovery (FGHR) is an energy efficient device that recycles the heat from the flue gases which would normally be expelled into the atmosphere and uses it to preheat domestic hot water.

Q What is weather compensation?

A Weather compensation is a device that communicates between the boiler and an outside temperature sensor. It tells the boiler to alter the flow temperature in relation to the weather outside, leading to fuel saving and a consistent environment.

Q What is load compensation?

A Load compensation works by measuring the response of the heating system and controlling the flow temperature depending on the required load. When the boiler first fires, the increase in the return temperature is measured, giving an indication of the required load, and the boiler varies the flow temperature accordingly. The changes in the return temperature are then monitored and the flow temperature adjusted accordingly. This can reduce fuel consumption.

Q Where can I find more information?

A The updated Building Services Compliance Guide, will not be available until April 2018, but, keep an eye on as it will available at this website in April.