Tuesday, July 3, 2012

Cooling Without Power

I know there are a few million people out there now in hot weather and without power due to the storm.

Here are a few ideas on cooling without electricity that are quick to implement and might be helpful during the hot weather power outage.

If you know people who are without power in hot weather, please pass on these ideas to them.

- Stop window solar heat gains during the day.  Windows that face south, east or west are major sources of solar heat gain that tend to cook the house.  Its critical to stop this heat gain from heating the house.

The best place to stop the solar heat gains is outside the windows with external shades -- this keeps the heat totally out of the house.  If you are working from the inside of the house, closing blinds (especially if they are reflective) is helpful.   Putting aluminium foil against the window would be much more effective in that it efficiently reflects both the visible and IR in the sunlight back out the window.

An easy and quick to install set of external shades like these can make a huge difference...

More on window shading here...

- Water the roof.  Putting a sprinkler on the roof to wet it down intermittently will cool the roof by evaporation, and therefore cool the attic.  The cooler attic will reduce the heat gain to the house.  Here is an example roof cooling system...

There are more examples in this section of the Cooling page on Build-It-Solar...

Example of a fancy roof cooler, but a sprinkler or two will do.

- Shade the house.  This may not be that easy to do on short notice, but anything that shades the exterior of the house will reduce heat gain.  Maybe a jury rigged set of Shade Sails?...

- Using cool basement air.  Some people have reported that circulating cool basement air to the living area can be quite helpful.  This is a simple example of Fran's system...  While this system uses a small fan, if you open a window in the basement and a window as high as possible in the house, the stack effect will tend to circulate the air even without a fan.  Or, I guess, you cold just move down to the basement?

- Ventilation.  In these days of Air Conditioning and powered everything, people tend to forget how effective night time open window ventilation can be.  Opening windows on opposite sides of the house in the direction of the wind is helpful.  In multi-story homes, opening windows low and high makes use of the stack or chimney effect to circulate more air.
If it cools off enough at night, using as much might ventilation as possible to cool the thermal mass of the house will make it more comfortable on  the following day...

If you can rig up a fan that is solar powered or car battery powered, this can help a lot with the ventilation.  Solar powered attic ventilation fans are available at a lot of hardware stores...

- Evaporative Cooling.  One simple form of evaporative cooling that has been reported to work pretty well if you have a concrete patio and a window above the patio where air is flowing into the house.  You wet the patio area down with a hose, and try to keep it wet.  The evaporation of the water cools the air before it enters the window.  The evaporation also adds humidity, so this will not be as effective if the humidity is already high.
Conventional evaporative (swamp) coolers require some power, but much less that conventional AC units for the same output, but, again, are less effective in high humidity areas...
Some evaporative coolers are solar powered -- an example...

Edit July8: Note the DIY solar powered evaporative coolers here...  This is something one might be able to make on short notice for cooling during an extended power outage.  It could be run directly off solar or a solar charged car battery.

Mist Cooling.  Mist cooling can be very effective for even fairly large outdoor areas.   Here is one DIY outdoor mist cooler...   Dripworks sells an inexpensive mist cooling kit...

- Cooling just your immediate area.  This section gives two simple schemes in which only your immediate sleeping area is cooled...  Very little power required.
If you can get ice, the water bed scheme might work with ice cooling?  Insulate around the outside to keep the coolth in the waterbed.

- Reflective roofs.  This is perhaps a bit extreme, but you could change your roof color to white...

There are dozens more cooling ideas on the Build-It-Solar Passive Cooling page -- many of these require no or minimal electricity to implement ...

If you know of any additional good cooling ideas for emergency power outage situations, please add them in the comments, or email me -- Gary...

If you try any of these methods, I'd like to hear how they worked out for you.



  1. Another way is through solar shades clayton, ca it will maintain temperature as well as saves energy.

  2. I found windows at the highest point of the attic very helpful to let out the hottest air, in particular during the night. Even without any wind, you will notice a slight breeze of cooler air entering the house at the bottom and leaving it at its top.

    I just suggest to add a motor and a rain sensor to avoid a flood from a nightly thunderstorm.


  3. Highly recommend the white metal roof. If you use metal shingles the cost differential can be as little as 20% compared to an asphalt roof. Get different bids!!

  4. Best way is to adequately insulate roof and walls with blown insulation, shade east south and west facing windows and cool down house at night if air temperature is cool enough. Also seal leaky air ducts. Cook using a solar cooker to avoid heating the house. I have done this in Sunnyvale CA and house temperatures stay cool during the day without air conditioning, fluctuates less than ten degrees Fahrenheit. Our energy bills are very small. Where drought is a problem the water cooling is a problem too. Solar panels on the roof may also reduce roof heating. Radiant barrier stapled to rafters helps cool attic also.

  5. love the homer bucket mini evap cooler, thanks for adding it.

  6. Kudos again for showing some great ideas on a very important problem.

    Summer residential air conditioning loads are the single biggest problem for North American utilities.

    Swamp coolers in the West are in second place to white roofs - http://greenbuildingindenver.blogspot.com/2012/05/dont-worry-about-swamp-cooler-water.html

  7. I still go for ventilation to cool my house because I really want to feel freshest air out there. I have my own solar powered fan which truly helps in the ventilation process. Really, we need a cool house even if power is not accessible. We don’t want to see ourselves freaking out because of the sweats and all. That would be so much of a problem to deal with when we could not take care of stuffs after the storm because of our bad mood.

  8. Homes built for evaporative coolers will have the ductwork in place, but for most retrofit installations, you'll want windows opened.


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