An airtight building envelope ensures that there are as few gaps and cracks between the internal and external building environment. This enables the occupant to maintain full control over the internal environment. This contributes to significant improvements in thermal comfort inside the building.

Using quality and sufficient insulation in the construction of the building allows for good thermal separation. This allows for separation between the external environment and the heated or cooled conditions in the internal environment. This improves thermal comfort inside the building and reduces the risk of condensation.

Installing mechanical ventilation allows the recovery of heat and the delivery of fresh filtered air. It does this without creating uncomfortable drafts, and without creating excessive demand on other heating and cooling systems.

Windows are another area where quality insulation can improve the energy efficiency of the building. Installing low emissivity glass with double or triple glazing along with non metal frames to reduce thermal breakages.

The size of the windows being appropriate to each orientation, allowing solar radiation to penetrate during winter months but not too much during the summer months. Making certain the windows are also properly sealed. It all contributes to the energy efficiency of the building.

Thermal bridging refers to the transmission of heat from one part of the building to another. The aim is to maintain control over the internal environment and manage how heat and cold move from the inside of the building to the outside.

As such insulation needs to be sufficient in thickness but it also needs to be continuous. Any break in the insulation can reduce the effectiveness of the insulation and result in thermal bridging.

Where it is impossible to further reduce the efficiency of the insulation then combining it with materials that do not conduct heat as well. Using timber instead of metal or strategically designing thermal breaks in the construction in order to reduce the flow of heat from one conductive material to another.

All of this contributes to higher energy efficiency and reductions in the risk of condensation leading to lower levels of comfort.

Indoor Temperature - Max 20˚C with no more than 10% of the hours in a given year exceeding 25˚C. Some allowances for extreme climates.

Heating and Cooling - Max heating demand of 15kWh/m2/yr or a heating load of 10W/m2. Max cooling demand of 15kWh/m2/yr or a cooling load of 10W/m2 (if installed). Some allowances for humid climates.

Humidity - Humidity estimates not exceeding 12g/kg for more than 20% of the year. This works out to approximately 60% relative humidity at 25°C.

Airtightness - Maximum reading of 0.6ACH50 with on-site verification.

Energy Demand - Maximum Primary Energy Renewable (PER) demand of 60kWh annually per square metre of living space.