Home A/C airflow question. Door open or door closed?
 

Facts: Single level, 2000 square foot house with a single AC unit. All ceilings are vaulted and floorplan is very open. Thermostat is in the hall next to the kitchen. Outside temps are around 75 degrees. The back door is open. My wife begins to cook dinner. House starts heating up due to 400 degree oven. AC is typically set to 78 degrees.

Eventually the AC kicks on as 78 degrees inside the house is exceeded. The back door is still open.

Do you leave the back door open and assume the cooler air outside is going to come in the house as the hot air goes out?

Or, do you close the back door because you need to keep the newly made cool air inside the house?

Please show your work. :)

How cool is it outside?
I was going to ask how humid it was, but now that I'm on my PC instead of my phone, and I see that you are in Phoenix...

If it's 72° and cooling off, then I would turn the AC off and open more of the house to get some airflow through the house (hopefully, there is a breeze). A cross breeze should carry the heat from the kitchen out of the house.

If it's 75° outside, not cooling off and fairly still, then I would probably close up the house because without a breeze to move the air through the house (would have to have in inlet and outlet, some something opposite the back door) or if the temp outside is too close to the temp inside, you're just not going to cool off much.

If you were in Houston or another humid area, I would probably say close up since the AC will not only cool the house, but will also pull the humidity out of the house which is always a good thing around here.

We can't here as the humidity is too high
so the damp outside air will freeze up the a/c coils
if too much is let in too fast

btw you need a kitchen vent fan

open widows turn on whole house fan

Close the door. You run the A/C with doors and windows closed. Or shut off the A/C and open all the windows. You may recirculate the air with the fan in the latter case but keep the compressor off.

JR

Your kitchen should have a hood, fan and vent to extract heat from cooking. If it doesn't, install one.

Basic rule of physics involving flow: the air coming from the AC system will flow the most to the place of least resistance. Having the door open has more of the AC going to the kitchen and right out the door. javadog has the best answer

Close the door once your A/C kicks on if you want it to run.

I am a home energy nerd and my 1800 sq ft house in SoCal rarely needs A/C. This method works well in Calif. and off-summer seasons in Phoenix.

1. Install attic fan w t-stat to remove hot air above 105F and keep attic well ventilated. Attic temps can soar to 150F in summer and bake the house from the top down.

2. Plant trees or vines on the south side of the house to keep the sun off in summer.

3. Open windows any time outside temps are below 78F and run a window or whole house fan all night.

4. Close up house tightly in the AM to preserve the cool overnight air.

5. Use a programable t-stat for A/C that comes on only 1hr before I get home if temp rises above 80F. Set to 78F.

Sept. elect bill was $60 for the month.