People who live in Passive Houses say that when you virtually eliminate all outside noise through your well insulated and airtight enclosure, the noises inside become much more apparent. So what are the things that go bump or (more likely) buzz in the night in a Passive House?
When we’re not making noise ourselves, our fridge is by far the loudest thing in our home. Beyond purchasing an EnergyStar appliance that you know will run relatively efficiently, there’s not a lot to be done here, and the background hum of a fridge is not a concern in my books.
The ventilation system is extremely quiet. Very efficient heat recovery ventilators like the Zehnder Q series units we have are not only inherently more quiet than less efficient units, they are also tested to meet stringent sound performance requirements. In occupied spaces, it is inaudible except when we operate in boost mode and even then, we can only hear a slight whir if all else is silent and we train our ears to hear it.
The hydronic heating system is also very quiet. In the mechanical room we can hear the low hum of two small pumps moving water through the pipes when there is a call for heat.
So far so good. But what was that godforsaken buzzing sound? I only heard it on our side when in the mechanical room, but in the other unit, it was very apparent upon opening the front door- the kind of whiny buzz that could be used for sleep deprivation and other forms of subtle torture.
Further investigation identified the culprit, which was this innocent looking guy:
This is an ASCO RedHat general duty actuator for a solenoid valve that is part of the emergency drain down system (which protects the heat pump in the event of a power outage). It consumes about 10W and is continuously powered, which equals not only unwanted noise, but wasted energy.
Some back and forth with Len, our neighbourhood hydronic specialist, and a bit of googling turned up this RedHat electronically enhanced solenoid actuator, a next generation product that reportedly only consumes ~1 W and is specifically designed for applications where noise is an issue:
$400 in parts and a couple hours of Len’s time later, et viola, problem solved. I can now say with confidence that all is quiet on the Passive House front.
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