The challenge

Passive House performance asks an existing house to behave in a way it was never built to.

• Achieving continuous airtightness across every junction between existing and new construction
• Sealing every service penetration as the work went up, with no way back once linings were on
• Keeping the new work in character with a heritage-listed terrace in a conservation zone
• Delivering every material down approximately 900mm of side access
• Scheduling deliveries, parking and lifting around the school directly opposite

The build

The building envelope received a comprehensive internal and external wrap system, designed to achieve a high level of airtightness and thermal performance.

The word that carries all the weight there is continuous. A wrap with gaps in it isn't a wrap, so every junction, every penetration and every corner has to be detailed and sealed as the work goes up.

Once the linings are on, none of it can be reached again. The performance specified on paper has to survive the construction process.

That airtightness is also what makes the ventilation system work properly. In place of air conditioning, a heat recovery unit supplies filtered fresh air while recovering energy from the air going out. That only works when air moves through the unit rather than leaking through gaps in the building.

uPVC windows continue that approach at every opening. Their insulated frames and tight seals help reduce heat transfer and air leakage, supporting the performance of the envelope rather than creating a weak point within it.

The extension was built with high ceilings and large north-facing windows to bring light deep into the house, with an internal deck linking new and old so air can move through both. Externally it's finished in brick veneer, so the new work sits with the original terrace rather than announcing itself.

All of it came down the side path, with deliveries, parking and lifting planned around school activity across the road.

The result

The terrace is bright where it used to be dark, and comfortable where it used to be cold and damp. It holds a steady temperature through summer and winter with far less heating or cooling, and fresh air moves through the whole house.

From the street it still reads as the heritage terrace it always was, which in a conservation zone is the whole point.