The last week delivered sustained heat with peak temps in the 30C+ range (90F ish). Inside? The top blue line in the graph below tells the story. The setpoint for cooling is at 75F so you can also see that the CERV only cools part-time but has been effective when needed.
The lower greenish line records the effect of the earth tube in reducing intake air temp.
How about humidity? The bottom pale blue line is house air bumping along at 60-70% RH when the humidex was 40+. The top line is the Relative humidity (RH) of the intake after transiting the earth tube. The reason for 100%RH is that this air was hot and humid at intake and during transit, the temp dropped raising the RH and condensing (dehumidifying) in the earth tube. The earth tube has a slope and a drain to cope with condensate. I have been monitoring it and all is operating as designed thus far.
The window overhangs have been doing their job. With the passing of the solstice, the sun will penetrate more over coming weeks but for now, it barely has an effect after 10am.
NOTE: My apologies in advance for the confusing temperature scales. While our CERV2 is an amazing device, it is made in the USA and has not yet been taught to play nice at all times with Centigrade temps and the metric system.
Daily power consumption for the entire house including cooling/ventilation is running at little over 10kWh or about $1 a day.
Those are some impressive numbers Chris! I am impressed by the CERV2's ability to cool actively.
ReplyDeleteDo you think you'll have to add a dehumidifier in the future?
DeleteWe will see how the actual measured humidity tracks. The modelling did not indicate the need for further dehumidification. Climate change conditions may change the situation too. Certainly can accommodate it if needed.
DeleteHow does the earth tube drain the condensate? You must have a basement.
ReplyDeleteThe tube slopes away from the house to the tower and the tower inlet end has a drainage bed under it.
DeleteChris, how did you find the combo of the CERV2 and the 5kW duct heater over last winter? Would you do it again and if so, what might you change about the CERV2 unit in general? It's pretty rare in Ontario, so your insight is valuable!
ReplyDeleteThe combo works great after a slightly tricky initial setup. Totally hands off after that it barely measurable temp variations. We have had two 12 hour+ power outages (one at -15C). The temp drop was only about 5C but the recovery was surprisingly fast at about 1 hr.
DeleteThe CERV should have a better implementation of Celsius, better fasteners for the filter hatches, better interface for controlling and loggin the duct heater. Pretty minor stuff. We could have done a bit more duct noise muffling as it is noticeable (subjectively) at high speeds especially since the house is so quiet otherwise. And our ducting install is a bit restricted on flow to 1st floor (nit picking). The low flow rates are are new ground for HVAC installers.
The folks that make the CERV2 are excellent to deal with at every stage. Knowledgeable about IEQ in general and passive house, responsive and available.
Do it again? Certainly unless something else comes along that I am unaware off. No regrets.
After discussion with Rob Blakeney (Local Impact Design) and Ben Newell (Build Equinox) they pointed out that as result of us setting a high (75F) cooling setpoint and the incoming air temp being low (from the earth tube) the algorithm of the CERV2 elects to run on 'free cooling' mode which means the heat pump is not activated. I lowered the setpoint which caused the CERV2 to switch to "vent cooling' with heat pump activated. We only had a week or so of hot humid weather since then but it appears to be dropping the relative humidity about 10% which gets us back to a better range of 50-60%
ReplyDelete