Letters: March/April 2006
A version of this article appears in the March/April 2006 issue of Home Energy Magazine.
The Interfaith Coalition on Energy, a nonprofit energy efficiency organization working with churches in Philadelphia, Pennsylvania, recommends on their Web site that churches not use ceiling fans during the heating season, since the fans may add to the heating load of the buildings (see http://interfaithenergy. com/article2.htm).
We had a recommendation on the governor’s Web site for people to use their ceiling fans at home to save natural gas for heating. I challenged this and had it removed. Unfortunately, I have not found very much more than the article I mentioned above regarding the use of ceiling fans during the heating season to defend my skepticism. Can you help?
Home Energy’s go-to guy for ceiling fan questions, Chris Calwell, replies:
Many of the claims for ceiling fan energy savings stem from some detailed research done at Kansas State University about 20 years ago. If memory serves, they were primarily validating the effect on comfort from wind chill—that is, the cooling energy savings rather than the heating energy savings. The article you mentioned noting that there is no particular benefit from destratifying warm air at ceiling level was compelling. Given what you found, I would tend to agree with you.
That said, churches are a special case that’s a bit different from homes. The ceilings are often much higher and the usage much more episodic. I’ve tended to believe that ceiling fans can save energy in the winter in homes in some cases. If you heat with a wood stove or a forced-air furnace, it can be difficult to get uniform mixing of the heat. Ceiling fans running in reverse bounce the air off the ceiling at relatively high velocity and then send it back down along the perimeter of the room at lower velocity. This tends to minimize the wind chill effect while still helping to push some of the warmest air in the house down where it can be felt by the occupants and the thermostat.
I had a cathedral ceiling in my house with a wood stove and measured air temperatures in the high 80ºsF near the ceiling, while temperatures close to the floor were more like 65ºF. In that situation, destratification seemed like it could definitely help. Still, I fully agree with your other points about not running ceiling fans in unoccupied rooms and not running them with air conditioners.
Wisconsin’s Ventilation Standards
I just wanted to say thanks for a great article on Wisconsin’s weatherization ventilation standards (“Ventilation Standards at Work,” Nov/Dec ’05, p. 12). The article clearly explained the ventilation requirements for the ASHRAE 62.2 standard. And, while the $400 average cost for implementing the standards in Wisconsin is way more than we spend on ventilation in Michigan, it seems like a good investment in clean air. I like not having a minimum building tightness standard, which has recently been growing dramatically in Michigan, supposedly to keep up with the ASHRAE standard.
I was confused by only one thing in your article. In the section “Piloting ASHRAE 62.2” (p.15), you mention that pilot agencies were allowed to “use any of the three methods to provide ventilation to their units.” What three methods are you referring to? You listed Quadrature or Ecotope as evolving methods for ASHRAE 62.1 calculations in ZipTest Pro software. Is that one (or two) of the three? Is it Rick Karg’s spreadsheet? Anyway, you lost me there. Otherwise I thought everything made great sense.
Author Martha Benewicz replies:
Good to hear from you and thanks for your comments, Thom. The three methods for calculating ventilation requirements that the pilot agencies in Wisconsin chose from include the two ASHRAE 62.1 calcula- tions, Quadrature and Ecotope, and the ASHRAE 62.2 method. Quadrature is the building tightness limit-advanced (BTLa) calculation on ZipTestPro software; Ecotope is the 62.1 calculation on ZipTestPro2 software. We upgraded the TI- 86 calculators of the pilot agencies to ZipTestPro2, but we did use Karg’s spreadsheet in the pilot.
I read with interest the article “Energy Efficiency Through Education and Low-Cost Measures,” (Sept/Oct ’05, p. 10). The authors write, and it is crucial to note that,“participants reported on baseline consumption characteristics, the installation of energy efficiency measures, and the adoption of savings actions. The savings estimates were drawn from these data, and the results have been impressive.” It would be helpful to know whether the estimated results and savings reported will be verified with a pre/post-treatment, weather normalized billing analysis, and onsite verification of measure installation.
As many of us are aware, there is often a big difference between projected results versus measured results. Even with the best energy auditors, computerized energy audits tend to overpredict savings. I suspect the same may be true of participant-reported results.The reported savings really should be clearly labeled as projected savings. The numbers the authors give imply very high savings compared to programs that directly install a more comprehensive set of measures but measure their savings through billing analysis.
Author M. Sami Khawaja replies:
Mr. Laverty raises a good point regarding our article. We have a few responses.
Our surveys gather data regarding baseline conditions including the wattage of replaced bulbs, hours of use, number of people in the household, number of showers taken, and so on. These data are then used to estimate the savings. For example, a 100W bulb replaced with a 23W CFL will save 28 kWh annually for each daily hour of use. This is just a fact and not subject to variation. It is conceivable that the reported hours of use may be in error or that the recipients may increase usage after installation of the CFL. Errors in reporting are as likely to be understated as overstated. Therefore, the statistical average can potentially eliminate this data noise. The same argument holds for the other measures covered in our article.
In contrast, an energy audit is based, for the most part, on assumptions derived from prototypical homes. The auditor may override some of the assumptions with data from the actual home. If the home-specific values are not used or entered incorrectly, the audit tool will not accurately estimate savings. Also, most audit tools do not do a very good job in dealing with the interactive effect between measures, nor do they handle the order of installation well. Behavioral changes can have a tremendous impact on heat loss and audit estimates. Light bulbs, showerheads, and so on are not impacted to the same degree.
The suggested pre/post-treatment analysis has been tried successfully at times. We applied it to the REACH program in Indiana where the participants only received intensive energy education. The savings were nearly 12%. We compared before and after energy consumption of treated homes against a group of comparable nonparticipant homes.
Pre/post-treatment analysis is not always easy to do. This is especially true when the ratio of data noise (variations due to weather, economy, and so on) to the signal (savings) is high.