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Matt Power

When it's 0 degrees outside, you've got to raise the indoor thermometer to 70 degrees. In 110-degree weather, you need to change the temperature by only 40 degrees to achieve the same comfort level. Since air-conditioning is inherently more efficient than heating (that is, it takes less energy to cool a given space by 1 degree than to heat it by the same amount), the difference has big implications for greenhouse gases.

In the Northeast, a typical house heated by fuel oil emits 13,000 pounds of CO2 annually. Cooling a similar dwelling in Phoenix produces only 900 pounds of CO2 a year. Air-conditioning wins on a national scale as well. Salving the summer swelter in the US produces 110 million metric tons of CO2 annually. Heating the country releases nearly eight times more carbon over the same period.

eric cantona

@ Matt - that's fascinating. I've never heard that before. the one caveat I would add to that, though, is that even in places like Vegas or Phoenix they are still heating their homes in the winter. might be an interesting study to determine typical 12-month Co2 emissions between Portland and Vegas relating to HVAC usage.

Brian - re: "shouldn’t there be some kind of concerted, collective effort to make sure we are planning sustainable cities as well as sustainable buildings?" - might be a good time for you to head down to Metro to see what they're up to.


Nice point Matt , and the real problem is no one should be living in the Las Vegas desert , unless they can stand passive cooling and minimal water.
Everyone is welcome to check out my article in today's Portland Tribune [pg c6] about green/cost
issues of a Park Roof for the Columbia River Crossing Bridge.

Jeff Guggenheim

Matt: You have an interesting point. However, I don't think it can be applied across the board.

For example, most larger buildings have to be cooled year around (even in frigid climates) as they are internally load dominated (heating loads are generated from within by lighting, computers, people, etc....) Energy inefficient buildings manage this heat load with the A/C systems.

Also, where is your source regarding A/C being more energy efficient than heating? I'd be interested in learning more about how they arrived at that conclusion.


I know we're on the left coast, but if you want a true heating v. cooling comparison I'd be more interested in comparing Miami with Boston in a typical residential single family house. The humidity and night temps greatly reduce the ability for night ventilation in the hot months. The SW desert areas are starting to be figured out from a passive cooling standpoint. It's the east coast climates that are a hard nut to crack. Water is a different story altogether.

Hold off on that gas tax funding for residential purposes. We've got to use that money to fix our transportation problems. If you were thinking carbon tax, I'd be ok with some money going there. Unfortunately we won't have to cross the carbon tax bridge for at least another 20 years anyway because it's political suicide in most parts of the country.

Jim Heuer

Apparently there isn't general agreement with Matt's assertion that the annual CO2 load for Phoenix is only 900 pounds. At this website:
They give a statistic that air conditioning a typical home has an annual carbon footprint of around 6000+ pounds of CO2.

Certainly Matt's comparison of a Northeast home heated by fuel oil is a bit unfair in comparison with air conditioning in a city powered extensively with hydro power.

It would seem that Brian's point is still well taken (and supported by a lot of the environmental web sites out there), that central air conditioning is over used in the U.S. Further, as energy costs continue to rise, we'll need to re-conceive our buildings and residences to make better use of natural ventilation and lower-energy alternatives for cooling in those places and times when ambient temperature is simply too high for normal human activity.

And dare we say or think it... maybe we'll need to re-evaluate (as billb suggests) our city building in places like Phoenix and the Coachella Valley (Palm Springs, etc.) that virtually require air conditioning. The trends in this regard will be hard to reverse... The latest statistics show that the population of the Coachella Valley has more than doubled (to half a million) in the last 10 years, and Phoenix has similarly experienced tremendous growth.

Contractor Guy

Incredible resource. I'm going to suggest this to all of the Phoenix air conditioning companies I know. Thanks again!

Seaver Franks Architects

This is a great article! As a group of Tucson Architects, we know all about high temperatures and we encourage regionally responsive architecture that respects and enhances the surrounding environment. We recently started construction on a new 5695 SF structure that is a LEED Platinum status candidate as recognized by the U.S. Green Building Council and is designed with open floor plans, excellent daylighting and natural ventilation. Our hope is that more new construction will follow suit.


Matt's analysis is flawed in that it only covers conduction (heat transfer from outdoor air through walls/windows/openings into the indoor air) and fails to account for radiation. The solar radiation has a far greater impact on A/C cooling loads than conduction.

External shading devices are the best ways to passively cool buildings - plant a tree on the south side or west side of your house or have large overhangs above windows.

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