Andrew,
Thanks for posting your poster. That is a lifetime of tweaking, as some technology advances and some, such as passive solar, has been around for eons!
You definitely have a more challenging climate. We can typically open windows around 7pm and close them by 9am. Automatic, thermostatically-controlled windows would be a nice improvement, but manual works here, even if we don't get the times exactly right.
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M Keith Sharp
Emeritus Professor
Louisville KY
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Original Message:
Sent: 07-06-2023 09:23 AM
From: Andrew Stone
Subject: Trick for nighttime ventilation cooling
I too am a huge fan of nighttime "cool loading". As my friend and solar cooker extraordinaire Mark Chalom always says "Passive solar means an active owner".
Being in the southwest, we enjoy 40 degree F daily temperature swings - and our 96 degrees F afternoons, because of low humidity, aren't unbearable. However we have noticed that it stays hotter longer than it used to and it may be midnight or 2am before the outside air dips below 70 degrees F.
I check my mobile weather app to see when it'll be worth opening windows at night, and as a light sleeper, I'll get up to open the windows at 1am or 2am, and set an alarm to shut them when temperatures get back up to 75 degrees F at around 8am.
As a result, we went all the way into Mid-June without turning on our heat pump coolers in our exterior insulated passive solar adobe home, and we have banked a bunch of kW from our net-metered PV system for winter comfort without compromise or yelling at the rest of the family to turn the heat down.
My poster presentation on "40 Years to Net-Zero" from ASES22 documents a lifetime of DIY going green.
Andrew Stone, President
NM People's Energy Cooperative
Together A Just Energy Transition
¡Sí, hablo Español!
Original Message:
Sent: 7/5/2023 4:18:00 PM
From: Mike Curran
Subject: RE: Trick for nighttime ventilation cooling
Our house is partially surrounded by trees and we're in a rural area so it often cools down enough at night to open the windows in the back bedrooms and run a window fan at the opposite end of the house. By morning it's almost cool enough that the A/C doesn't come on until late in the day, if at all.
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Mike Curran
Retired EE
Original Message:
Sent: 07-04-2023 01:07 PM
From: M Keith Sharp
Subject: Trick for nighttime ventilation cooling
Discovered a trick for cooling with nighttime air thought you all might be interested in. Nighttime ventilation cooling is driven by wind and/or by the stack effect (hot air indoors rising to exit high windows and being replaced by cool outdoor air entering through low windows). We typically don't have much wind at night, so the stack effect is what we mostly use. We have high windows in a loft, and windows on both the main floor and in the basement.
Opening the loft windows and the basement windows cools the basement well, but does not cool the bedroom on the main floor as much. We have found that it is better to leave the basement windows closed, and open the loft windows and the main floor windows, including the bedroom. Even though the stack height is roughly half as much, we get better cooling of the important rooms.
The coolest air is drawn into the rooms with the highest priority for cooling. Duh. Makes sense after the trials, but was not so obvious beforehand.
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M Keith Sharp
Emeritus Professor
Louisville KY
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