The build is now watertight, which means we can get on with first fix plumbing, electrics and our mechanical ventilation heat recovery (MVHR) system.

Semi-rigid ducts snake their way around the ceiling carrying the distribution pipework for the MVHR system. This system will extract warm, moist air from the kitchen, bathrooms and utility room, put it through a heat exchanger to preheat filtered, fresh air which will then ventilate the sitting room, the snug and the bedrooms.

The ducts run in a continuous length from the various outlets back to a main distribution box, meaning there is very little opportunity for air leakage. The ducts, along with other services, will be hidden behind a suspended ceiling.

We’re using a high-performance, Passivhaus-certified MVHR unit from Airflow. As well as being efficient, this system also features CO2 and humidity monitors in the unit, so if it detects high levels of CO2 (which can make a room feel stale), it will automatically alter the rate of ventilation to ensure rooms feel both fresh and comfortable all year round.

Our system also features a brine heat exchanger which will pump brine through 100m of pipe that runs around 1m under the ground surrounding our new home. As the temperature at this depth below ground is consistently about 13°C, the brine solution in the pipes adjusts to that same below ground temperature.

This brine solution is then pumped through our heating matrix so that air pulled in from outside is then warmed or cooled to that same 13°C by the brine pipework.

By preheating/precooling the air before it hits the heat exchanger, our MVHR unit can work most efficiently.

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