I really don't like the strategy of super cooling in the morning. I prefer fresh air instead. I throw the windows open wide and let all the cool morning air in. By midmorning I'm usually starting to close those windows because the outside air is getting warmer. By mid afternoon I'm closing all those windows and turning on the AC and setting the temperature to 1 degree (Fahrenheit) cooler than the current room temperature. I've found that temperature is in the range of 78-84 degrees depending on humidity. Then the AC kicks on and removes all the humidity and makes things comfortable. In the evening when it starts cooling back down again I turn off the AC and open the windows back up.
I'm paying 50% less in cooling costs than those cooling an equivalent space as mine and I'm getting plenty of fresh air and I'm still working comfortably. Heck, today is one of those days where the highs are going to be in the low 80's and I probably won't even need to turn on my AC. In fact it's already at the high for today, 84, and it's 76 inside my house and I have a nice breeze coming through the window.
Just another way how working from home is saving me money and improving the environment.
I predict in certain areas, "free cooling" systems will become the standard. These are system which do just what you talk about automatically. When there is a need for cooling and exterior air is cool enough, supplement supply air with air from the outside. This way your AC system load is reduced, or if cool enough, the compressor doesn't need to run at all to remove heat from your home by replacing it with cooler air from outside.
Free cooling is already part of many commercial AC systems, usually referred to as an "economizer".
I wish I had a system like that and have thought about it a lot. I live in Calgary and today will be 28C and it will go down to 12C at night. I wish my system could just run a fan at 7am and draw in a ton of cool air to cool the house. Instead my AC runs for 30 minutes or whatever. Seems like a waste.
I'm working towards that with my Home Assistant installation, using inside and outside thermometers. You can trigger the fan based on the appropriate parameters, time of day, temps, etc.
I did a bit of reading after posting my comment and it looks like many HVAC technicians recommend against doing this in a residential setting due to humidity issues. Sounds like most HVAC economizers are for commercial settings.
I've been wondering why my Nest thermostat doesn't already have an option to do this. I can turn on the fan manually, but it's not smart enough to do that automatically when it's cooler outside than it is inside.
Your system only exchanges heat with the outside (via a refrigerant). The fan only circulates air; on its own, it doesn't draw air from the outside (by design; you don't want to be cooling outside air).
The system would need to have a second mode and a fresh air intake, as well as wiring and support from your thermostat. It can be done, but HVAC is a slow-moving industry.
I have a similar lows in the 80s. Except high is 105. I also have a wife that likes it 65 (70 is our great compromise). I don’t think any of this precooling/ventilation hacks would work for me. This time of year, even at night (thermal mass), if my AC turns off the house temp goes up about 1F every 5-10 minutes. It’s just brutal.
I don't want to pay for them but I do wish I had automatic windows. It would be so nice if my windows automatically opened if the temperature outside was a few degree's cooler than my house and I was in "cool" mode. If it took the wind into consideration, even better. My house cools off so nicely when I open windows on opposite sides, but I have to remember to open and close them at the appropriate times and I have to be around to do it.
Automatic windows seem hard, but you can accomplish this "easier"(not super easy, but doable if you are a home DIYer) by having a "whole house fan" + a make up air unit(basically a vent that opens up when the fan turns on, supplying outside air to replace the air the house fan takes away).
Fairly common to see here in Boulder and the front range in older homes(before ubiquitous AC units), because it tends to be cool at night + hot in the day during summers, so around 5AM you can have the house fan turn on, cool your house, and then you ride that throughout the day until the evening when the temperature starts to drop again. Works quite well IMHO - my first rental had a system like this as well as AC, but I actually never touched the AC.
They also had a bunch of other adaptations for better Summer airflow. Large, open attics with multiple windows or vents, open to the lower floors (no doors in the way), to help hot air go up and out; high ceilings (an aid, not a hindrance, to cooling, if you're not using AC); floor plans and house placement that took prevailing winds into account; larger windows for better airflow when they're open, and usually on all sides of a house, roughly symmetrically (look at modern houses, lots of them have at least one side with no windows); big, straight, end-to-end hallways to let air blow through; and so on.
AC cooling efficiency requires abandoning several of these, and others are simply not given much thought because they don't matter if you're using AC all the time anyway. Which is unfortunate, because it shrinks the parts of the year in which going AC-free with windows open is viable.
Adaptive vents, too. Why cool the whole house when I'm going to be in two rooms for the majority of the (hot) afternoon before opening the window to the bedroom in the evening?
I want floor vents that are wireless networked, coupled with occupancy, CO2, and temperature detectors. They should have the smarts to figure out when to open and close, such that rooms are never stuffy, and never too hot or cold.
If you setup water heater / cooled systems using the in-floor (sometimes in-wall) pipes, they get that almost for "free" - you can turn on and off zones very easily.
That's a fine idea when building a new house, but untenable for a house that is not being thoroughly renovated. My forced-air HVAC system is built-in, and replacing the register vents would run me under $2K at $100 a pop. Ripping up my flooring and installing in-floor heating would cost me tens upon tens of thousands of dollars.
That's essentially what zoning is, most commonly used to heat/cool different floors of a house separately without having to have multiple furnaces and AC units. If I understand correctly, you want the shut-off flaps or gates as close to the blower as possible for maximum efficiency—just shutting off the vents at the ends of the lines would mess with pressure and airflow in the rest of the system in undesirable ways.
I'm paying 50% less in cooling costs than those cooling an equivalent space as mine and I'm getting plenty of fresh air and I'm still working comfortably. Heck, today is one of those days where the highs are going to be in the low 80's and I probably won't even need to turn on my AC. In fact it's already at the high for today, 84, and it's 76 inside my house and I have a nice breeze coming through the window.
Just another way how working from home is saving me money and improving the environment.