Every passivhaus home has a controlled mechanical ventilation system with heat heat recovery (MVHR), and ours is no exception. With expert advice from Alan Clarke and Green Building Store we have designed a cascade system based around Zehnder Comfoair 160 VV Luxe ventilation unit. This is the smallest unit from Zehnder and can supply up to 160m3 of fresh air per hour – plenty enough for the two of us and a medium sized dog. Another benefits are built-in frost heater and automatic summer bypass when internal temperature gets over 21 degrees C. We have kept the ventilation ducts dust-free during the clay plastering and only installed the terminals just before commissioning.

The ventilation system works best when properly commissioned, so it was  great to have Alan and Nick coming over to help. Alan hired a nifty anemometer with self-balancing fan for accurate reading of flow rates, whilst Nick used manometer as an alternative way of measuring. We also installed a condensate drain, which wasn’t in place by default. A few hours later (including pub lunch & a game of ping pong) our system was set up. The first thing that struck me was how quiet the whole system is. The MVHR unit itself is just audible, but as it’s located in the Utility room it won’t be an issue. Supply & extract terminals throughout the house are totally quiet – a sign of good design and installation.

The next big step will be installation of hot water system and then we’re just about ready to move in – can not wait!


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