When do you turn on your AC?

[clamum]

If you have horizontal blinds, then you want to close them the way that leaves the top part of the blind closest to the window (not the bottom portion of the blind). Otherwise you lose most of the benefit of closing them.

Let / be the blind and | be the window. Then you want this to keep the rising hot air from rising through the blind slats (hot air is trapped on the window side of the blinds):
/ |
/ |
/ |

Not this (rising hot air rises right through the blinds into the room):
\ |
\ |
\ |

In winter you need to reverse that direction so that any heat does rise into the room (many people find this ugly though). Having the blinds open in daytime is better, but you don't always want to do that for privacy reasons.

For fun, one day I ran my exact horizontal blind dimensions through Ansys Fluent computational fluid dynamics simulations (http://www.ansys.com/Products/Fluids/ANSYS-Fluent). Having the blinds the wrong direction reduced the benefit of having blinds by almost half.

Hory shet, I didn't realize there was a difference. My blinds are vertical and are just crappy apartment blinds. It would be interesting to know the difference in degrees F between the horizontal blind closing options if someone did an accurate, controlled test. Honestly it's hard for me to believe that there's any difference more than a degree or two, everything else being the same, but I suppose cooler is better and it's a simple thing to do regardless.

 

[dullard]

Hory shet, I didn't realize there was a difference. My blinds are vertical and are just crappy apartment blinds. It would be interesting to know the difference in degrees F between the horizontal blind closing options if someone did an accurate, controlled test. Honestly it's hard for me to believe that there's any difference more than a degree or two, everything else being the same, but I suppose cooler is better and it's a simple thing to do regardless.

Vertical blinds won't have this issue, because they are aligned with the natural flow of the air.

The horizontal blind orientation isn't a major difference, because blinds themselves aren't generally a massive part of the heat loss/gain of a house. But when they are oriented the wrong way they basically become individual aids to natural convection. In the summer, in the wrong orientation hot air from contact with the window + heat from the sun on the blinds easily rises out of the blind/window space and cold air easily flows towards the window to replace the hot air -- the exact opposite of what you want to happen. The reverse is true in the winter. Cold air from contact with the window sinks easily through improperly oriented horizontal blinds then hot air flows easily through the slats to replace it.

 

[dave_the_nerd]

When it gets warm.

 

[Rifter]

when it gets to hot

 

[gorcorps]

I have two things:

- I don't sleep with windows open and like it cool when I sleep, so if I can't cool the house down to at least 73 before I go to bed and close the windows, I'll use the AC
- If I can't get the house below 77 with the windows open during the day, AC comes on (set to 73)

 

[Thebobo]

85 ish or over

 

[Azuma Hazuki]

I don't, ever, on account of not having one. Which really sucks from June to October.

 

[Stopsignhank]

When my wife says so. I am not sure what temperature that is at as it is a moving target.

 

[lxskllr]

I don't, ever, on account of not having one. Which really sucks from June to October.

Know what feels good? Laying in front of a fan, and spraying yourself with alcohol. Also, check out peppermint soap. Feels great when you get out of the shower.

 

[RLGL]

When it hits 90 F

 

[adairusmc]

68 degrees here

 

[MtnMan]

When the wife tells me to....

 

[MrSquished]

I don't go by the temperature outside at all. I just keep it at cool and keep the thermostat set to 70-72 degrees in the warmer months when I am home - it will go on if it needs to and won't if it doesn't - and simply raise it when I leave to save money. It's not rocket science.

 

[shortylickens]

I used to turn it on when I couldnt sleep. Now I use a bed cooler.

https://www.amazon.com/gp/product/B005504PVK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

 

[olds]

70

 

[zerocool84]

When it hits 90 F

This

But I don't live in places where it's crazy humid

 

[Svnla]

Whenever my body feels hot. I do not know how people were able to live down here before AC/electricity.

 

[Red Squirrel]

When it starts to hit about 23-24 in my office I will often turn on the central AC. Got it last year and it's nice so I tend to want to use it more. Well worth the money. I had a portable one before that which I'd setup and turn on at about the same temp but it was very loud and didn't do the whole house.

I actually used it the other day, was 22 outside which is probably the warmest it's been so far this year, so it had hit around 23 in my office. I had got back in the house from doing a bit of spring yard work like raking so I was hot.

Since our hydro rates are insane here I normally try to tough it out as much as I can but 25C is going to be my cut off where I just give in and turn it on. I can do it from my phone or computer too so I have tendency of doing it just because I can. On super hot days I might even set it from work before I leave so that when I get home it started to cool to take a bit of the edge off. I see A/C more as a luxery so my default setting is to just have it off. My neighbor's condenser unit is running almost 24/7 in summer even if they're not home. He's a lawyer so he can afford it I guess.

What's funny is now we're back to winter weather. There's snow on the ground now. It was shorts and tshirt weather like a day ago.

 

[Red Squirrel]

If you have horizontal blinds, then you want to close them the way that leaves the top part of the blind closest to the window (not the bottom portion of the blind). Otherwise you lose most of the benefit of closing them.

Let / be the blind and | be the window. Then you want this to keep the rising hot air from rising through the blind slats (hot air is trapped on the window side of the blinds):
/ |
/ |
/ |

Not this (rising hot air rises right through the blinds into the room):
\ |
\ |
\ |

In winter you need to reverse that direction so that any heat does rise into the room and the cold is blocked from sinking through the horizontal slats into the room (many people find this ugly though). Having the blinds open in daytime is better, but you don't always want to do that for privacy reasons.

For fun, one day I ran my exact horizontal blind dimensions through Ansys Fluent computational fluid dynamics simulations (http://www.ansys.com/Products/Fluids/ANSYS-Fluent). Having the blinds the wrong direction reduced the benefit of having blinds by almost half.

I always put mine the second way so that the air from the heat registers does not get "redirected" in by them. Though never crossed my mind to reverse that in summer, as you're right the heat from between the window and blind is going to tend to want to go up and come out. I just got these blinds like a year ago though, for longest time I just had these crappy sheers that offered like no privacy. Now the black van with the small dish outside that keeps port scanning my wifi can't tell if I'm eating or sleeping anymore.

 

[FeuerFrei]

I don't. It's off all summer. Hope you don't mind sweat.