Thornleigh Passive House

One of the keys to passive house is air tightness and mechanical heat recovery ventilation... which is great most of the time time. But during hot days and cool nights it is often beneficial to get as much night time cooling (i.e., ventilation) as possible - which means opening the windows. In our passive house the primary thermal mass is the water wall, and the house is designed to allow for efficient night ventilation of the house and water wall by opening two panels of the big north facing window near the water wall and the clerestory windows at the top of house. This creates a ' stack effect ' with the hot air rising out the top of the house helping to pull cool air in the house at the bottom... across the water tanks in the process. Last night was the first time we opened the windows to allow this night time cooling to happen (as today's weather was forecast to be very warm we wanted to cool down the house as much as possible before hand). While I'll work on a

The things one learns about ventilation... Our heat recovery system is set to by default to replace 1/3 of the house air volume every hour, and we have nifty little Netatmo sensors that measure carbon dioxide (amongst other things). I say 33% of the volume by default because the bathroom and kitchen contain booster switches that increase the replacement to 50% for 30 minutes - designed to clear the effects of cooking, showering, and other such activities.  Here I've attached a "normal day" from last week. It is fairly clear when the parents leave their bedroom to start their day, when we get home, and when we go to bed. In comparison our old house, had no mechanical ventilation but did leak like a sieve. The carbon dioxide levels in the living room of the old house would routinely get above 2000ppm, and quite often didn't quite get back to 400ppm before we came home from work/school unless the windows were left open. In the new house carbon dioxide levels