Looking for ideas to cool our house more efficiently

[begood]

We live in employer-provided housing. We have central air-conditioning, but it's not terribly efficient. We have a 1300 s.f. house, two stories. The house is in full sun, southern exposure, until about 2:00 in the summer, after which it's shaded by big trees on the north side.

I work at home in a study on the second floor. We all sleep on the second floor. We live our lives, basically, on the second floor aside from eating supper, which we usually do outside. We even watch TV in the evening on the second floor.

But here's the problem. The thermostat is on the first floor, in a north-facing room that we spend almost no time in. To get the second floor to cool to 76 degrees (I am of A Certain Age, and trust me, you do not want to see me if my house is hotter than that), we have to keep the thermostat at 71. SEVENTY-ONE. That's insane.

We do not have any ceiling fans. I believe the employer would install them if we bought them, but I don't know how long that would take.

I use a Vornado fan from Costco at night - I blow that sucker right at my face! I've tried putting one at the bottom of the stairs to shoot colder air up, but it doesn't seem to work.

The house design will not accommodate a whole-house fan. I do have a semi-finished attic where I could put a fan in the window, but it's a teeny-tiny window. Would just putting a box fan in front of the window to blow hot air out work at all?

Costco currently has window fans for $39.00. Would it be worth putting them in and blowing out hot hair? Or would having windows open completely defeat the purpose of having central air?

Oh, and I also have a very small window unit that we have used in the past to cool the attic when we had company staying up there. I could put it in my study and use it during the day and just not cool the rest of the house at all, but then it would get STUPID hot and I wonder if it would take just as much electricity to cool off the house each night as it would to keep it marginally cool all day.

[Greg]

Sounds like a bad case of over-exposure.  I would recommend shade materials (roll-up bamboo awnings?) for the south-facing exterior windows and glass doors if any.

Don't worry too much about what setting you have to use to make the system work, it's just how the system is set up.  Theoretically you could try a remote thermostat but my point is that the use would be about the same to achieve what makes you comfortable. 

Check your furnace (assuming forced air here) to see if it was a fan setting to just circulate the air, this might help equalize the upper and lower floors, which could help in cooling the upstairs.  This might depend on whether or not there is a return vent upstairs.

ANY attic ventilation will help keep the upper floor cool.  Try just leaving the window open to see if it helps, a fan would probably help even more.  The question is, where would the cooler air come from if the fan is blowing out the hot?  There would need to be cross-flow, like with a window at each end, to really work.

Good luck!

[phred]

What are the night-time temperatures where you are living?

Some initial ideas on the air conditioner:  How long has it been since the coils were cleaned (this is a spray on, drip-dry solution)?  Does the unit need a partial recharge of refrigerant?  Is the furnace filter unclogged?  What side of the house is the outside unit on?

Small fan in attic window: Do this in the evening.  Greatly effective if you can fabricate some kind of shroud to direct all of fan exhaust out the window instead of some partially hitting the wall. Would be nice if this window is on downwind side of house.  Try with using ac on, and with ac off but first floor window open just a little. Do this if evening outside temp is less than in house temp

Are windows on west side of house visible from street, or have great view?  If you don't mind blocking them off, you could cover them with some of that temporary winter window kit plastic, with sheets of bubble wrap, or even by force-fitting a sheet of Celotex into the greater window opening.

Even with central air, a room unit in your room may be best

[begood]

Sounds like a bad case of over-exposure.  I would recommend shade materials (roll-up bamboo awnings?) for the south-facing exterior windows and glass doors if any.

Don't worry too much about what setting you have to use to make the system work, it's just how the system is set up.  Theoretically you could try a remote thermostat but my point is that the use would be about the same to achieve what makes you comfortable. 

Check your furnace (assuming forced air here) to see if it was a fan setting to just circulate the air, this might help equalize the upper and lower floors, which could help in cooling the upstairs.  This might depend on whether or not there is a return vent upstairs.

ANY attic ventilation will help keep the upper floor cool.  Try just leaving the window open to see if it helps, a fan would probably help even more.  The question is, where would the cooler air come from if the fan is blowing out the hot?  There would need to be cross-flow, like with a window at each end, to really work.

Good luck!

Thanks, Greg!

We have a set of french doors on the south side of the house, which is also where the A/C condenser is. I do plan to request a full workup on the A/C. We just cleared a bunch of overgrown weeds from around and pulled ivy that had grown all along the back of it. I like the roll-up bamboo blinds idea. I don't want regular blinds there, and there are sidelights too. I wonder if we could get one bigass wide bamboo shade and install it above the french doors/sidelights so we could cover it all with one? Of course then we couldn't get out the doors...

We live in a pretty sticky area, where sometimes the temps get below the inside temperature, but often do not. And sometimes the temps are lower but it's so humid outside it still feels hotter.

I will look to see if we have a "fan" setting on the thermostat - we do have a furnace (we use fuel-oil for heat, but it's forced warm air).

[begood]

What are the night-time temperatures where you are living?

Some initial ideas on the air conditioner:  How long has it been since the coils were cleaned (this is a spray on, drip-dry solution)?  Does the unit need a partial recharge of refrigerant?  Is the furnace filter unclogged?  What side of the house is the outside unit on?

Small fan in attic window: Do this in the evening.  Greatly effective if you can fabricate some kind of shroud to direct all of fan exhaust out the window instead of some partially hitting the wall. Would be nice if this window is on downwind side of house.  Try with using ac on, and with ac off but first floor window open just a little. Do this if evening outside temp is less than in house temp

Are windows on west side of house visible from street, or have great view?  If you don't mind blocking them off, you could cover them with some of that temporary winter window kit plastic, with sheets of bubble wrap, or even by force-fitting a sheet of Celotex into the greater window opening.

Even with central air, a room unit in your room may be best

Hi phred! Like I told Greg above, I will request an A/C cleaning/inspection/filter replacement. The A/C unit is on the south side of the house, tucked in a corner for maximum heat retention. :( We get stretches in July and August when the temps outside never get lower than inside, like, upper 70s to even 80 overnight. And huuuuuuuumid. Blech.

I put light-blocking curtains in my daughter's room (south and west windows), and I leave our heavy velour curtains closed on the west side of our room in the summer. I hate to do it, because I loooove light, but HOT light, not so much.

I will experiment with a fan in the attic. The Vornado is about the right size if we put it right in front of the window. The last time my husband took the A/C unit out of the window, a little bat was clinging to the sill beneath it! Scared them both!

[phred]

Problem with curtains is that the light has already passed thru the window, and thus the heat builds up inside the house.

ac on the south side is worst place it can be, as you already know.  Could you rig an awning or patio roof covered with ivy (?) .  That way both the ac and the Fr. doors will be shaded from the sun while air flow to the condenser is not blocked

It's not the heat, it's the humidity! Have you tried a semi-portable dehumidifier to make the house more comfortable while not having to have the ac on as much?

[begood]

Problem with curtains is that the light has already passed thru the window, and thus the heat builds up inside the house.

ac on the south side is worst place it can be, as you already know.  Could you rig an awning or patio roof covered with ivy (?) .  That way both the ac and the Fr. doors will be shaded from the sun while air flow to the condenser is not blocked

It's not the heat, it's the humidity! Have you tried a semi-portable dehumidifier to make the house more comfortable while not having to have the ac on as much?

I did not know that about heat and curtains and the inside of the house! Learn something new every day (sometimes more here on the MMM forums. It's an epiphany an hour around here!). I like the idea of trying to shade the AC unit outside, and I think we could do that with a trellis-type deal for not a lot of money. The french doors lead to a deck that is probably five feet higher than the A/C unit, so I'd need to approach each one separately. We do have a humidifier in the basement for the summer. I could try moving it and see if it made a difference.

I really appreciate these brain-storming ideas!

[Milspecstache]

Need to see your house layout to really recommend this but...

In my house I don't currently have AC for the upstairs (worked on it today in fact so I am 2 weeks away from having it turned on) so when it is hot like last summer I use 2 fans to push cold air upstairs and push the warmer air downstairs.  The cold air fan was turned to push air vertical up to the balcony (from the ground floor) and the warm air fan was turned to push down the stairs.  Surprisingly this worked enough to keep it tolerable upstairs.  Just a temporary solution last summer while I saved money to buy the mini-split units for the upstairs.

[greaper007]

2 things I do. 

1. Do you have a basement?   If so just make this your summer quarters.   We all sleep in the basement all summer and I make it through a Denver summer without using the air once.

2. Put in a whole house fan.    It gets rid of the warm air in the house when it cools down at dusk.

Otherwise just be very judicious with opening and closing windows.   Mine get closed around 8 am, that keeps the cool air in from the night before.   I open them up when it cools down at dusk.   And for gods sakes don't open your blinds.

I've also been known to wear a wet T-shirt on really hot days.

[geekette]

I don't know where the OP lives, but in central NC, when summer's humidity kicks in, there's no point in open windows.

When we moved into this house, the upstairs was much warmer than downstairs.  We looked in the crawl space and there are dampers on the main duct work (article here).  Adjusting those allowed us to send more air upstairs.  It really, really helped.

[Rural]

I don't know where the OP lives, but in central NC, when summer's humidity kicks in, there's no point in open windows.

Yep. We turned off the climate control a couple of weeks ago, and we're still holding steady in the upper 60s inside (thermal mass FTW), but indoor humidity is now over 70%, so we're going to have to do something to avoid mold on the walls. I'm watching for a low humidity night, hoping that opening up will help, but I expect I'll have to run a dehumidifier in the next day or two.

[Gimesalot]

Crazy idea here... but it really works for me!

When it gets really hot, put your feet in a bucket of water.  I know it sounds crazy, but in New Orleans the summers are brutal and I manage to keep the a/c at 82 to 85 most of the time by cooling my feet.  It will at least make you feel cooler.

Less crazy idea...  Can you work from somewhere else? If you can leave during the day and set the thermostat at 85 during the day, and then blast the crap out of that place at night, you could end up evening out the costs.

One last comment, I don't think the fan will work because it will most likely replace the hot air with cooler humid air.  Since you don't like the humidity, you will have to run the a/c to dry the air out.

[deborah]

We have a set of french doors on the south side of the house, which is also where the A/C condenser is.

Does the hot air from the air conditioner rise (as hot air does) and go in the french doors - thus heating the house? You might think seriously about some form of blocking this from happening - a "storm window" for the french doors, directing the heat from the air conditioner another way...

I wonder if we could get one bigass wide bamboo shade and install it above the french doors/sidelights so we could cover it all with one? Of course then we couldn't get out the doors...

Shadecloth is good. You are trying to stop the glass from getting direct sun on it. If it is on the south, a horizontal  shade cloth (or pegola...) will do this. If sun strikes a window, it turns it into a very good heater.

As warm air rises, all it takes at night to cool houses is a window open at the very bottom level, and a window at the very top. This will encourage a current from bottom to top, dragging through cooler air from outside at the bottom. It is preferable that the bottom window is on the coolest outside area, as this will cool the house more quickly. If your house has a lot of rooms, warm air can get stuck in some, so you would need to open more windows. Fans do help, but are not essential. Your attic window, and one at ground or basement level would be best.

[agent_clone]

Bubble Wrap on the windows is apparently a good insulator (bit of a problem with seeing the picture outside but the light would still be there!).

Otherwise except for the fact that you have an upstairs upstairs and I would have no idea on how you would put them up and down I would suggest awnings or shade sails on the outside.  Awnings would probably need to be attached to the house, the shade sails just need somewhere to attach them to (e.g. on poles).

[begood]

I like all these ideas! For that stretch when it does get cooler at night outside than inside, we could easily open windows in the basement and the attic and try to direct some air flow. That's a no-cost opportunity, which I appreciate!

I hit an immediate snag on the bamboo shade idea  - we have vinyl siding on the house, and no idea how to install something to it, whether it's an awning or a bamboo blind. BUT! I like the sail shade idea, or one of those big (like, BIG) umbrellas. A friend uses one to shade her pool in the afternoon. We might be able to angle it to cover the A/C unit and the french doors at the same time. WIN! I'm exploring that today.

I don't think the hot air from the A/C unit comes up to the french doors, deborah. It sits about five feet lower, and slightly behind the deck where the french doors are.

Our basement is unfinished - okay for storage, but I would wilt into a depressive pile of sadness if I had to go down there to work for hours. But I like how you're thinking, and maybe I could at least move into the coldest room in the house (where the thermostat is) and work there, which would allow me to nudge up the A/C during the day and then we could turn it down at night.

Hive mind! I love it!

[S0VERE1GN]

I'm sure its already been said: but spend lavishly on the best exhaust fan you can find, and maybe even see if you can install a whole house attic fan in the house and get a rent discount/ get paid back.

[Gerard]

I work at home in a study on the second floor. We all sleep on the second floor. We live our lives, basically, on the second floor aside from eating supper, which we usually do outside. We even watch TV in the evening on the second floor.

I apologize if this is the stupidest feedback you get, but can you change your life around in the summer so that you spend more time on the cooler first floor?

(Also, don't give up on interior curtains. Yeah, some of the sunlight may become heat, but you're still reflecting a lot of light back outside before it gets the chance to heat your floors etc. That's why we open curtains when we want solar gain, after all.)

[OldDogNewTrick]

You can purchase relatively inexpensive window film that will significantly cut back on heat coming through from direct sun. Also get heavy drapes and keep them closed during the day. I can keep my house 1-2 degrees cooler just by not opening a drape during the hottest part of the day.

Outside awnings work wonders, but it is a rental so you have some difficulty there.

I have a fan on a stick in a corner of my office pointed right at me! The white noise masks outside noise and the breeze allows me to work comfortably with a higher thermostat setting.

[Greg]

I meant to put the bamboo awnings on the outside.  Inside only helps with light, the solar heat has already gotten in by then.  Outside keeps both heat and light out. 

Vinyl siding makes it tricky.  Sometimes you can mount directly to the window frame, depending on what they're made of.

[Emg03063]

Window film and fans, as has been stated.  If nighttime temperatures are below target temps, add inexpensive thermal mass to hold the cold in longer.  I'm using empty gallon milk jugs filled with water.  Cost is near zero.

[OldDogNewTrick]

Window film and fans, as has been stated.  If nighttime temperatures are below target temps, add inexpensive thermal mass to hold the cold in longer.  I'm using empty gallon milk jugs filled with water.  Cost is near zero.

Interesting. How many of those do you need to make a discernible difference?

[dcheesi]

Problem with curtains is that the light has already passed thru the window, and thus the heat builds up inside the house.

For cooling, I would think that solid white curtains would be the best, since they reflect more of the light back out instead of absorbing it.

Also, I would think that solid curtains would at least slow down room heating during the day, since a lot of the heat would initially be trapped in the air buffer between the curtains and the window.

ac on the south side is worst place it can be, as you already know.  Could you rig an awning or patio roof covered with ivy (?) .  That way both the ac and the Fr. doors will be shaded from the sun while air flow to the condenser is not blocked

How much of a difference does this make? Now that I think about it, my heat pump is on the South side and in the sun part of the day...

[phred]

dcheesi:
 Reflecting the light back out is not the same as reflecting the heat back out.  Also, heat is not trapped in the suggested curtain buffer as the pleats and folds act like vertical chimneys to keep pushing the heat gain towards the ceiling and thus heating the second floor.  For your idea to work, the curtains/drapes would need to be plastic or otherwise impervious, and completely sealed around the window by using cornices at the top, magnets at the sides, and completely resting on the sill or floor.
The following is from "Natural Frequency"
"Once solar gains have passed through a window and hit an internal blind, they are already inside the space. Only if the blind surface is highly reflective and the solar rays redirected straight back out the window will this not result in some heat build-up. Thus, whilst the blinds may effectively block glare and daylight, conduction, convection and radiation will usually convey a large portion of the heat to the internal space.

If the space between the blind and the window is open at top and bottom, a convection current will likely result. This means that air warmed by the Sun will rise out of the top, causing a negative pressure in the gap between the blind and the window which will act to draw in cool air from near the floor in through the bottom. Such a system is a very efficient heat transfer mechanism which can be used to good effect in winter, but is rarely desirable in summer."

As to your heat pump on the south side of the house.  A typical ac system, as you may already know, works - in a manner of speaking - by temperature differentials.  The cooler the air, the easier it is for the condenser to dump heat.  It will then run less and cool more.  By being directly out in the sun, it will be harder for the condenser to dump heat  It will run a lot longer - maybe even all day - while cooling more poorly.  However, the south side is good in winter as the components reverse their function

[phred]

what this house really needs is big deciduous trees blocking all summer sun from the south side of the house.  Since trees grow slowly, this is not going to happen.  There are some fast growing trees, such as the Empress, but the wood from these is brittle - as in branches dropping without warning, and the trees are famous for plugging sewer lines.

While not perfect, cover all south and west windows with window film that can be peeled off later.  On cool nights (which you say rarely happens) put a fan in the attic widow - the one on the downwind side.  Open a first floor window on the upwind side.  Do not open basement windows unless basement has been tested for radon, and there are screens to keep critters out (does Texas have any snakes?)  The fan is needed because natural air flow will take too long to cool all the mass inside the house (furniture, interior walls)
Get the ac unit checked and cleaned, as mentioned  Add a dehumidifier or an additional window unit upstairs.  Six or eight feet in front of the outside unit erect a portion of louvered fencing to shade the unit while not blocking air flow.  This will need to be in a vee shape to block both south and west sun.  Alternatively, you could erect portions of chain link covered with vines.
Hopefully the south side of the yard doesn't have any patio, driveways or bare ground to reflect more light and heat into the house.

[Emg03063]

Window film and fans, as has been stated.  If nighttime temperatures are below target temps, add inexpensive thermal mass to hold the cold in longer.  I'm using empty gallon milk jugs filled with water.  Cost is near zero.

Interesting. How many of those do you need to make a discernible difference?

The heat capacity of water is 4.184 J/g*K, the highest of any commonly available material by far.  That means it requires 4.184 Joules of energy to heat a gram of water by one degree kelvin (or Celsius).  A gallon of water is 3.79 liters which is also 3.79 kg, which means that it will absorb 15.84 kJ of energy for each degree Celsius of temperature increase, or 8.8 kJ per deg Fahrenheit, or ~8 BTU.
(See http://www.mrmoneymustache.com/2011/09/01/what-is-thermal-mass-and-how-can-it-make-you-money/).  In a 17 degree temperature swing, each gallon absorbs 136 BTU.  Extrapolating from MMM's calculations, and assuming $0.10/kWh for power, each gallon saves approx $.03/month in electricity, so 33 to save $1.00/mo.  (Of course, the less efficient the AC, the greater the savings).  I can't say the difference has been discernible, but they were essentially free, and I have the space so why not?  For the OP, managing the solar gain is priority.

[greaper007]

How and where do you store the jugs to get the most out of thermal mass?   I have a brick house and we take a beating in the evening with a large south facing wall.

[greaper007]

What other cheap ways are there to cool if you own your home?    I've been really working on not using my air.    I plan on installing a whole house fan this year, it worked great in my last house.    I have a split level and we live in the basement during the summer.

I like the awning idea and the window film.   Does anyone know which ones are best, are they removable?   I really try to maximize my southern exposure for free heat during the winter.

I need to throw some more insulation in my attic and I thought I would put in a radiant barrier while I was up there.   I've heard that the benefits are negligible in an insulated space, but it would double as a venting system for for the eave and ridge vents.   About the same price as buying the Styrofoam vents.

[Emg03063]

Radiant barrier cut my summer power bill by 1/3, and that was for relatively new construction.   To get the most out of thermal mass, you would cover your walls, ceilings and floors in it.  Me, I just store jugs on the floor around the edges of the room, under tables, beds and couches.  It's not thermally optimal, but it's simple.  It's May in North Carolina, daytime highs are in the 80s, and I have yet to turn on my AC.

[SJS]

Could you somehow redirect the airflow in the ductwork?  We have a second home in AZ (and we are still here for winter - was up over 100 this weekend!) and we weren't getting enough air out of a few vents - so husband bought some kind of metal square to drill over the ducts we want to redirect from - basically  he blocked 50% flow from those ducts.  Has helped enormously.

We also just had a whole house energy audit done - about $100.  Well worth the money.  They'll do a bunch of checking then give you good ideas/tips of things you can do to make your home more energy efficient. 

[begood]

I appreciate these ideas that continue to come in. Our first step? Bubble-wrapping the attic window on the south side of the house. We got a whole box of bubble wrap from a friend, so it was free and easy. :)

We also did get the window fan from Costco. We haven't put it in yet (spring is taking its own sweet time, I'll tell you what!) but we're going to install it in the north-facing window in our bedroom and set it to suck out the hot air. I can still blow another fan on my face if I need it at night. :)

My goal is to keep the thermostat 3 degrees higher than we did last year. Start there, anyway. Not a huge amount, but if I could do that, it should help our electric bill in June, July, and August.

[Emg03063]

If your issue there is solar gain, and you're not inhabiting the space, throw some aluminum foil in front of the bubble wrap (towards the window) if it's not foil faced.

[phred]

I like the awning idea and the window film.   Does anyone know which ones are best, are they removable?   I really try to maximize my southern exposure for free heat during the winter.

You want folding awnings.  Ours were canvas lashed to a steel pipe framework.  Fold down in summer, up in winter.

As for the window film, browse your Home Depot or Loews

[begood]

If your issue there is solar gain, and you're not inhabiting the space, throw some aluminum foil in front of the bubble wrap (towards the window) if it's not foil faced.

Will do, Emg03063!

[begood]

Just wanted to update now that we've had our first 90+ degree days:

We put a layer of aluminum foil and then bubble wrap on our south-facing attic window. There's a noticeable drop in the temp up there just from doing that - it's nowhere near as stifling as it was last summer.

We closed all vents on the first floor and closed the main duct in the basement going to the first floor. We're getting much more powerful airflow to the second floor now. The result? Instead of a 5-degree differential between first and second floor, there's now a 1-degree difference. So I was able to bump the thermostat up 3 degrees overall without sacrificing sleeping comfort.

I have a followup question, though: Is it better to leave the A/C on when I'll be away from the house for several hours so the temperature stays approximately the same? Or should I turn it all the way off, then put it back on when I get home? It will have more cooling to do then, so I wondered if it was worth it.

[phred]

experts say leave the ac running.  If you're gone for two weeks, then yes shut it off

[MrWednesday]

experts say leave the ac running.  If you're gone for two weeks, then yes shut it off

What experts? Michael Bluejay recommends shutting it off and provides not only logical reasons for doing so, but evidence based tests (that you can easily preform yourself if you want to check his results) demonstrating it is better to shut it off. http://michaelbluejay.com/electricity/ac-on-or-off.html

[deborah]

experts say leave the ac running.  If you're gone for two weeks, then yes shut it off

What experts? Michael Bluejay recommends shutting it off and provides not only logical reasons for doing so, but evidence based tests (that you can easily preform yourself if you want to check his results) demonstrating it is better to shut it off. http://michaelbluejay.com/electricity/ac-on-or-off.html

+1 - every expert I have read says to shut it off. Some suggest that if it can be set to come on at particular times, you might want to set it to come on 1/2 an hour before you get home, so the place has a chance to cool down.

When my parents lived in an exceptionally hot part of Australia, the water came from 100 miles away over the desert, and was actually boiling when you turned the cold tap on in Summer. Their hot water system was within the insulated part of the house, and in summer the hot water system was turned off, and "hot" water was used as cold. Even in those extreme temperatures, they only had the air conditioning on when they were home. 300 days of the year over 90F, 65 over 100F on average.

[begood]

When we lived in Florida, we replumbed the house (a common occurrence in lightning-prone FLA, with its copper pipes under concrete slabs... *smh*...) and ran the pipes through the attic. For six or seven months of the year, we had to tell house guests to be careful of the "cold" water coming from the tap since it would often be scalding hot!

Thanks for the link, phred. :)

[geekette]

We had a similar experience years ago in Key West.  We remembered noting the large white pipe beside the highway along US 1 from the mainland, and boy was that "cold" water aggravating on sunburn! 

[chops]

Lot of great ideas here - just wondering if it makes any sense to put the window film (or aluminum foil) on the outside of the window rather than the inside?  Would this help keep the sun from heating up the glass? 

[phred]

What experts? Michael Bluejay recommends shutting it off and provides not only logical reasons for doing so, but evidence based tests

Good for Michael Bluejay!  Now, lets do some thinking.  The OP is living in a house, and not in a calorimeter.  Is the area very humid?  With the air circulation off and the temps rising, any moisture entering with the heat can condense and lead to mold and mildew.  Turning the ac on later will not remove the mold once started.  My assumption here is that there are no leaking faucets or indoor plants to add their moisture
  Are their pets left in the house? Many modern breeds are not as hardy as their ancestors; they may die of heatstroke.
  Once the indoor gets up to 95, laptop batteries start to degrade, and hard-drives start to physically expand which may lead to damage when checking the ol' email on returning home.
  High temps cause wood to expand.  Wood floors may buckle; they don't unbuckle when later cooled.  Wood doors and drawers may warp and become very difficult to open or close.
 I will expand on my earlier comment.  If the OP is gone for more than about four hours, it will make sense to install a programmable thermostat to raise the ac setting between five and seven degrees for that time period.  On the other hand, if the trip out is infrequent, just raise the thermostat manually.

[lpep]

Full disclosure: I live in a 2-room apartment in Hanoi, Vietnam. It was 99 here yesterday, and the humidity is pretty high.

What I've learned from the locals: Buy a regular standing fan. It is surprising how well fans work at cooling you down. We haven't turned on the AC in two days, despite the 99 degree daytime temps (we were home all day). Take it with you from room to room. You don't need as much AC as you think you do. Also, if you have windows that get sun, seal those things off as much as you can. We have black-out curtains that help a ton.

Also: cold showers. Wet hair + fan is amazingly cooling. Open windows when it makes sense.