Hi openHAB community, I recently completed an HVAC automation project for my home in Phoenix Arizona and wanted to share what I learned. Our summers regularly exceed 115F with attic temperatures hitting 160F+ so efficient climate control is critical.
I am running openHAB 4.x on a Pi 4 with a Honeywell T6 Pro thermostat via Z-Wave, Aqara temperature sensors in multiple rooms plus the attic via Zigbee, and an Emporia Vue for energy monitoring.
The biggest win was a pre-cooling automation that drops the house to 73F before our utility peak pricing starts at 3pm. During peak hours the house drifts up to 78F but stays comfortable. This alone saved about 15-18% on summer electricity bills.
Other automations that helped:
- Attic temp monitoring triggers whole-house fan at night when attic exceeds 140F
- Window/door sensors pause HVAC if anything is left open over 60 seconds
- Automated south-facing shades close when direct sun hits those windows
Curious if anyone else is using openHAB for climate management in hot regions. What automations have made the biggest difference for you? Also looking for Zigbee outdoor temperature sensor recommendations that can survive 120F+ summers.
Quick update on this project. I ended up switching from the Aqara sensors in the attic to Sonoff SNZB-02D units because they have a wider operating temperature range. The Aqara units were reporting erratic readings above 150F which made my automations trigger incorrectly.
Also discovered that running the whole-house fan automation at night is much more effective if you pair it with a delayed thermostat schedule. Instead of cooling to 73F all night, I let the fan bring the attic down to 100F first then only kick on AC at 5am to pre-cool before sunrise. This cuts about 2 hours of AC runtime per day.
For anyone curious about the energy savings numbers, my July bill went from around 380 dollars down to 315 after implementing all the automations. Most of the savings come from the pre-cooling strategy and the attic fan.
Not a hot climate for sure, but when I moved into my current house there was no AC at all. I’m at 7000’ altitude and the number of days over 100 °F is one or two per year so ACs are not standard. Whole house fans are also not standard.
But it still gets uncomfortably hot.
And while ACs and whole house fans are not standard, basements are standard. And the temperature difference between the top floor and the basement in the summer was usually 15 °F. So one of my first home automations I created after “fixing” the garage door opener was pretending we have an AC and running the forced air heater fan to bring some of that cold air up from the basement. It made about a 5 °F difference.
Eventually we put in an AC mainly because of smoke from the wild fires. It’s hard to sleep with the windows open when the air is unsafe to breath. So I shut down that automation. But it remains one of the most impactful automation I’ve run.
I found controlling shades using something like OpenWeatherMap binding to get precise sun location readings has been beneficial. My need was two pronged, both energy savings as well as protecting floors from fading due to sun exposure. A combination of azimuth, season (although sun elevation is usually available and more precise), and outside temperature (and rules of course) gives me set it and forget it control. For instance, you may want the sun hitting those windows with shades up in the winter for warming. Took a little time finding the relation between the extremes (summer equinox, winter equinox, etc) and how exactly that translates to sun exposure on my house, but worth it.
Hi, being in the middle east (uae), I am in the extreme desert heat during the summer, and on top of that, high humidity due to being on a small island on a beach, sea temp in the summer peaks at 36C.
My 2bed 1550sqft condo is connected to the district cooling plant.
The system works on the same principle as a car engine radiator. FCU (fan coil unit). Plant sends cold water which cycles through coils which have a fan in front. Controllers are KNX which is connected to OH.
Billing model is made so the usage is not really penalized (1RTh costs 0.08$ but you pay 23$ per RT of capacity per month (so in my case 60$ capacity charge and peanuts on usage).
Nevertheless, I have control rules in place because:
usage still burns some electricity (fan coil units consume 70-140W)
high usage = more maintenance
careless usage with opened balcony - condensation, mold.
OH Rules:
when house gets empty, shutdown everything (AC included)
when someone comes home, if temp threshold is met, start AC
failsafe - if balcony or window is opened, stop ac immediately (no timer, as even 1 minute with high humidity outside and/or temperature difference will cause water condensation start dripping from the grill in the false ceiling). return the ac when door/window is closed.
failsafe - if indoor temp drops below certain threshold stop AC (sometimes certain residents do not use auto mode button, so if the fan is started in manual mode it will never stop)
failsafe - if indoor humidity passes the threshold and stays like that for x hours, start AC regardless if house is empty/full
if auto mode is enabled, set the desired temp automatically (based on month of the year, room..)
separate rule that defines all temp thresholds based on time of the year
zigbee leak detectors in drip tray below FCU where condensate (removed humidity) drips, drain sometimes gets clogged with dirt and tray fills and spillover happens.
edit: some additional rules that monitor indoor/outdoor absolute humidity, if the difference becomes big and certain thresholds are met, we get an email alert to close or recommendation to open the balcony.
The changes in humidity can be extremely fast due to wind change. You can have dry desert air (wind coming from inland desert) for hours, and then within 10-15min suddenly humidity went from 15% to 70% and temperature dropped for 4-5C (wind direction changed, wind comes from the sea)
