What is Nzeb? A Nearly Zero Energy Building (Nzeb), is one with a very high energy performance and that gets a very low amount of energy mostly from renewable sources on-site or nearby.
Why do you need to know about regulations?
A failure to address the new requirements at an early design stage may result in expensive ‘bolt-on’ technological solutions later in the process, or possibly even an inability to achieve compliance on completion. To avoid the situation you need to hire an architect or other competent building professional and BER assessor at the beginning of the project.
The early design stage DEAP assessments by the BER assessor will inform the final design as your designer experiments with different configurations to achieve the most robust and cost-effective solutions. The BER assessor will issue a part L compliance report using the DEAP software to ensure all the requirements of the new regulations are properly implemented into the house design. You will also need to carry out one or more a tightness tests during the build process to ensure you are on track with compliance as part of a proper site management/ airtightness regime. Last but not least, it's also very important to know that the regulations apply to both new builds and existing homes. Remember, the legislation has always placed ultimate responsibility for compliance on the designers, builders and owners of the buildings.
Extensions and renovations
A significant feature of the updated regulations is the requirement for ”major renovations”* to meet a ”cost of optimal” energy performance standard (in the ROI this is a minimum BER of B2) insofar as this is “technically functional and economically feasible”.
*“major renovation” means the renovation of an existing dwelling where more than 25% of the surface area of the existing buildings thermal envelope undergoes renovation. Thermal envelope meaning the entire surface area of the building through which it can lose heat to the external environment or the ground, including all the heat loss areas of walls, doors, windows, floors and roof. As an example, if you install external wall insulation (EWI) combined with upgrading existing windows and doors then this could very easily add up to 25% of the surface area of the Thermal envelope.
Appendix F of the TGD, Part L (Technical Guidance Document, Energy) shows how to calculate the percentage of renovation surface area of typical dwellings, and table 7 of the TGD, Part L indicates categories of major renovation works that meet the cost of optimal performance level. Note that table 7 refers to works “planned as a single project” suggesting that 25% rule is not intended to be aggregated over time.