Buildings are responsible for almost 40% of the UK’s energy consumption and carbon emissions, so it is important to improve the energy performance of buildings and identify ways in which the energy consumption and associated costs can be reduced.

A new dwelling must be built to a minimum standard of total energy performance. Airtightness regulations are outlined in Building Regulations Part L – Conservation of Fuel and Power, which apply to new buildings in England and Wales. Certain renovations and extensions focus on improving airtightness to achieve greater energy efficiency so builders and developers must consider the quality of the building fabric, including walls, roofs, floors, windows, and doors, to ensure that the building envelope is properly sealed and there is minimal air leakage.

Making a Building Airtight

Airtight building solutions effectively protect and preserve the building structure to provide a healthy and comfortable living environment The primary objective of airtight construction, whether in the roof, façade, or floor area, is to safeguard the insulation and the overall structure. Airtightness is the control of air leakage in a building through the elimination of unwanted draughts an interstitial condensation. Applying airtight and windtight solutions during construction will effectively protect and preserve the building structure and provide a healthy and comfortable living environment.

The Building Envelope

The building envelope is a boundary line that separates the indoors from the outdoors, and includes exterior walls, foundations, roof, windows and doors. To achieve airtightness standards, a building envelope can be created with the installation of an airtight vapour control system. Achieving reasonable standards in airtightness reduces condensation, mould, rot, damp and the potential for structural damage. Good airtightness improves insulation, enhances thermal efficiency and improves energy efficiency of a building.

In both England and Wales, the maximum permitted air permeability for a new dwelling has been reduced from 10 m3/hr.m2 to 8 m3/hr.m2 @50Pa. However, the ‘notational dwelling’ described in Part L, against which the actual building design is compared, has an air permeability of 5 m3/hr.m2. In our experience, 5 m3/hr.m2 is a more common worst case scenario in new builds in the UK.

The maximum air permeability for buildings other than dwellings has also been reduced from 10 m3/hr.m2 to 8 m3/hr.m2 in both jurisdictions.
Critics have argued that the figures could have been more ambitious. Indeed, figures from the UK’s Airtightness Testing and Measurement Association indicates that the average airtightness of a new dwelling in the UK was already at about 5 m3/hr.m2 as far back as 2016.

It is anticipated that both England and Wales will reduce the maximum air permeability, at least for new dwellings, to 5 m3/hr.m2 when introducing the next anticipated update to national Building Regulations Part L in 2025.

The current air tightness regulations are outlined in Part L (Conservation of Fuel and Power) of the Building Regulations. These regulations apply to new buildings in England and Wales and certain renovations and extensions focus on improving the air tightness of buildings to achieve greater energy efficiency. This means that builders and developers must consider the quality of the building fabric, including walls, roofs, floors, windows, and doors, to ensure that the building envelope is properly sealed and there is minimal air leakage. By improving the air tightness of buildings, builders can create more comfortable and healthy indoor environments, reduce energy consumption, and ultimately save money for the building owner.

EPC (Energy Performance Certificate) provides an energy efficiency rating on a building. EPC’s rate a home from A (very efficient) to G (inefficient). They report how costly heating and lighting a building will be and what the CO2 emissions are likely to be. Since 2008 they are mandatory on all domestic and commercial buildings in the UK under the implementation of the Energy Performance of Buildings Directive.
Source : A guide to Energy Performance Certificates for the construction, sale and let of non-dwellings – GOV.UK

1. Junction Exterior Door Sill / Sill
2. Junction Exterior Door Lintel / Vertical Wall
3. Junction Intermediate Floor /Vertical Wall
4. Junction Rolling Blind / Vertical Wall
5. Junction Inclined Roof / Window
6. Penetration Inclined Roof
7. Junction Inclined Roof / Roof Ridge
8. Junction Inclined Roof / Vertical Wall
9. Junction French Window / Vertical Wall
10. Penetration of Top Floor
11. Junction Top Floor / Vertical Wall
12. Perforation Vertical Wall
13. Vertical Wall (Cross Section)
14. Junction Window Lintel / Vertical Wall
15. Junction Window Reveal / Vertical Wall (Horizontal View)
16. Junction Window Sill / Vertical Wall
17. Junction Lower Floor / Vertical Wall
18. Penetration Lower Floor / Crawlspace or Basement
19. Junction Service Shaft / Access Door
20. Junction Internal Wall / Intermediate Floor