Consequential Improvements – Part L2B Building Regulations 2010

Where an existing building has a total useful floor area over 1000m² and it is intended to;

1. Build an extension.
2. Install the initial provision of any fixed building service (other than a renewable energy generator).
3. Increase the installed capacity of any fixed building services (other than a renewable energy generator).

Then it may be necessary to undertake additional works to the existing building as well as the new work. These works are referred to as Consequential Improvements.
When applying the requirements it is important to review the exemptions contained in paragraph 3.5 to 3.22.
The requirements can also apply to large dwellings over 1000m² (see Approved Document L1B).
The requirements are that in addition to the principal works, consequential improvements will also be required in order to comply with the requirements of Part L 2010, unless it can be demonstrated that such works to the existing building are not technically, functionally or economically feasible. Such supporting evidence must be prepared by a suitably qualified person.
Measures that would be considered economically feasible are generally based on a simple 15 year payback on the cost of the thermal improvement works through energy savings – unless there are other unusual circumstances, such as the building has a life span of less than 15 years.  In this case a reasonable provision would be to achieve a simple payback on the life of the building.

Consequential Improvements on extending a building

To demonstrate compliance it would be acceptable that the consequential improvements provisions can be restricted to a value of not less than 10% of the value of principle works or the cost of the extension.
The value of principal works and consequential improvements should be calculated by a suitably qualified person and submitted as a report to the Building Control Body.

Examples of technically, functionally or economically feasible consequential improvements include;

1. Upgrading heating systems, cooling systems, air conditioning or air handling systems more than 15 years old by provision of new plant or improved controls.
2. Upgrading general lighting systems that have an average lamp efficacy of less than 40 lamp - lumens per circuit watt – and that serve areas greater than 100m² by the provision of new luminaries or improved controls.
3. Installing energy metering.
4. Upgrading thermal elements having a ‘U’ value worse than table 5a.
5. With provisos and exclusion by replacing existing windows, roof lights and doors (see guidance).
6. Subject to conditions by increasing on-site low and zero carbon energy generating systems.
7. Other measures recommended as a consequence of the EPC.

Consequential Improvements on installing building services

Consequential improvements will apply where it is intended to install a fixed building service as the first installation, or as an installation which increases the installed capacity per unit area to an existing service.

Examples of technically, functionally and economically feasible consequential improvements include;

1. Where economically feasible improve the buildings thermal performance to those parts of the building served by the services installed, and in addition.
2. Make consequential improvements to bring the existing as well as the new building into compliance with Part L unless it can be demonstrated that such works to the existing building are not technically, functionally or economically feasible.

The cost of the improvements required in (1) cannot be considered as contributing to the value of such consequential improvements in (2).  This is to avoid higher CO2 emissions due to a higher level of servicing from the new building services conditioning the environment.
The ‘installed capacity per unit area’ to an existing service is defined as the ‘design output of distribution system output devices [thermal units] serving the space in question divided by the total useful floor area of the space’.
This means for instance that if the boiler size to serve an extension is increased, rather than to increase the existing buildings heating provision, consequential improvements must be carried out in accordance with the requirements for an extension but not to comply with the requirements for increasing the installed capacity as described below.

Consequential improvements on increasing the installed capacity per unit area of a heating system

Unless it is demonstrated that such works are not technically, functionally or economically feasible, consequential improvements will apply where the installed capacity per unit area of a heating system is increased.  The 10% rule threshold as described for other consequential improvements does not apply. Examples of technically, functionally and economically feasible consequential improvements include;

1. Thermal elements within the area serviced by the systems and having a ‘U’-value worse than those in Table 5 (a) must be thermally upgraded.
2. Existing windows, roof light etc (with provisos and exceptions) within the area served and that have a ‘U’-value less than 3.3W/m2.K are replaced in accordance with table 3.

Consequential improvements on increasing the installed capacity per unit area of a cooling system

Unless it is demonstrated that such works are not technically, functionally or economically feasible, consequential improvements will apply where the installed capacity per unit area of a heating system is increased.  The 10% rule threshold as described for other consequential improvements does not apply. Examples of practical and economically feasible consequential improvements include;

1. Thermal elements within the area serviced by the systems and having a ‘U’-value worse than those in Table 5 (a) must be thermally upgraded, and
2. If the areas of existing windows and roof windows (not display windows) within the area served exceeds 40% of the façade area or the rooflights area exceeds 20% of the roof area and the design solar load exceeds 25W/m2, then the solar control provisions should be upgraded to meet at least one of the following criteria's to reducing solar gain and thereby the cooling requirements which in turn reduces energy consumption:

• the design solar load is no greater than 25W/m2
• the design solar load is reduced by at least 20%
• the effective g-value is no worse than 0.3 (See CIBSE TM37 calculation), and

3. Any lighting system within the area served by the relevant fixed building service, which has an average lamp efficacy of less than 45 lamp-lumens per circuit watt, should be upgraded with new luminaries and/or controls in accordance with the Non-Domestic Building Services Compliance Guide.