The most successful homes are designed as complete building systems, in which the fabric, structure, and building services work together to achieve clearly defined performance targets.

A fabric-first approach establishes those targets from the outset. Through careful consideration of insulation, glazing, thermal bridging and airtightness, the design team creates a building that requires less energy to heat and cool, provides greater comfort and performs more efficiently throughout its life.

Once the building fabric has been designed, the mechanical and electrical strategy can be developed to complement that level of performance. Heating, hot water, ventilation and renewable technologies should all be considered as one integrated system, rather than as individual products selected in isolation. Air Source Heat Pumps, solar PV, battery storage, intelligent controls and other building services should be specified to suit the building, ensuring systems are neither over-specified nor under-specified.

An important part of this process is the SAP assessment. As the design develops, the SAP energy assessor models the home's predicted energy performance, allowing the design team to test design decisions, review system specifications, and refine the building before construction begins. The assessment should continue to be updated as the design evolves, ensuring that the completed home meets the required performance level.

The airtightness strategy should also include testing during construction and again at completion to verify that the building is achieving its design performance and that the ventilation strategy reflects the measured level of airtightness. This not only supports compliance with Building Regulations but also provides confidence that the completed building is performing as it was designed.

This integrated approach enables every element of the home to work together. The building fabric determines the performance target, the ventilation strategy responds to that performance, and the building services are then designed to suit the completed building. The result is a healthier, more energy-efficient home where technology supports the building's performance rather than compensating for its weaknesses.

These principles have long been recognised within Passive House design, where careful attention is given to the relationship between the building fabric, airtightness, ventilation and building services. While not every project seeks Passive House certification, adopting these principles can help deliver homes that are better performing over the long term.