Carbon Dioxide and HRV

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 in the living room peak at about ~ 800ppm when everyone is home and decline to about 400ppm about the time we get back home.  While I had thought about dropping the ventilation rate while we were at work/school, it is clear that the default ventilation rate is about right.

Popular posts from this blog

Temperature (Out vs. Old vs. New)

Image
I have fielded more than a few questions about the temperature of our passive house versus the temperature of the house that we lived in prior (on the same lot).  So I've used the data I had on hand which is temperature (°C) recorded every 5 minutes over since October 2012. For the sake of consistency I am only using the NetAtmo sensors that I have had for that entire period. So I only have one outside sensor and one inside sensor located in the the respective living room. The outside sensor moved around a bit, but it should be good enough.  I've converted those measurements to hourly averages.  This ends up being ~ 66,955 hours to play with (52,232 hours from the original house, 14,723 hours from the passive house). I've left the rental house out of this comparison, but it was disturbing like the original house despite being ~ 20 years old. The key take-home messages: The passive house a much less variation in temperature than the original house (or outside).  In the summe
Read more

international passive house open day...

We had ~49 people come through the house for one of the International Passive House open days of 2019. As the event is not as widely publicised as Sustainable house day when we had more than 200 people through. The visitors who came through for this open house tended to already know a fair bit about passive houses (with many dragging along family members who they were working to convince of the merits of passive house living). Lots of the visitors were already planning or working on projects that were including passive house principles.
Read more

Water wall...

... Currently a work in progress... Thermal Mass A material’s capacity to absorb, store and release heat. Thermal mass is typically used to moderate temperature extremes by releasing heat when the home is cool and absorbing heat when the home is warm. Specific heat capacity A material's capacity to store heat (measured per unit mass). Some materials are better at storing heat than others. Water can store 4× as much heat per kilogram as concrete. Density Mass per unit volume (mass / volume). Denser materials have more mass per volume so they can make up in density what they lack in specific heat capacity. Concrete has twice as much mass per m3 as water. Thermal conductivity The ease with which heat travels through a material. Ideally, thermal conductivity should be moderate so that the absorption and release of heat synchronises with the building's heating and cooling cycle. Both water and concrete are highly effective! In comparison, steel and water hold a similar a
Read more