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Permalink Reply by Andrew J. Courts, Jr. on January 24, 2011 at 11:01am

What is the difference between T-12, T-8 and T-5 lamps?  What don't people upgraded all the way down to T-5s?  Does it have to do with the ballast or expense?

Permalink Reply by Russ Jordan on January 24, 2011 at 4:56pm

T-5 lamps are in metric length, and are not a direct replacement for T-12 lamps in existing fixtures.

Permalink Reply by Michael Heaney on January 24, 2011 at 5:02pm

To replace a T8 with a T5 you would need to replace the ballasts and, I believe, the whole luminaire because of a difference in length. It's not cost effective. T5's are a good application for new "high bay" fixtures used in convention centers and other high ceiling buildings.

Another good option is high efficiency T8s, which cost about twice as much as a standard T8.  They use approx 28W vs approx 32W, which can be cost effective. 

 

Here comes too much information. In some applications you can decrease the number of lamps required by using a ballast with a higher ballast factor.  If you are motivated to seek out more information on ballast factors here's are two good sources http://www.lightsearch.com/resources/lightguides/ballasts.html
and here http://www.energystar.gov/index.cfm?c=business.EPA_BUM_Glossary

As the Lightsearch article says, "Ballast factor is not a measure of energy efficiency. Although a lower ballast factor reduces lamp lumen output, it also consumes proportionally less input power. As such, careful selection of a lamp-ballast system with a specific ballast factor allows designers to better minimize energy use by "tuning" the lighting levels in the space."

Permalink Reply by Bill Davis on January 25, 2011 at 8:37am

At NC State, we still have quite a few T12 40W lamps on campus.  We have found that in most cases, we can replace the lamps and ballasts with a T8 25W lamp without any real loss of light level in our classrooms and offices.  We have changed the color/temperature from a 3600K (kelvin) color to a 4100K lamp.  The higher color temp creates a perceived brighter light output and has been accepted on campus.  We have been able to see a payback in less than three years for most of this work (leaving fixtures in place and replacing lamps and ballasts).  Often we'll find that an existing 3- or 4- lamp fixture can be reduced down to 2- lamps without light levels dropping below standards.  

 

One note of caution - we have found that some of our buildings had high-efficiency ballasts installed with the T12 lamps.  The payback on changing out these fixtures is not nearly as quick.  It's important to do some field work surveying existing conditions before projecting energy savings.

Andrew J. Courts, Jr. said:

What is the difference between T-12, T-8 and T-5 lamps?  What don't people upgraded all the way down to T-5s?  Does it have to do with the ballast or expense?

Permalink Reply by Anna Leonard on February 22, 2011 at 11:29am

Is anyone familiar with Energy Star's Portfolio Manager? Would you recommend it for use by local governments? Or is there another program that you would recommend using? Anyone who has direct experience or knowledge would be useful. Thanks! http://www.energystar.gov/index.cfm?c=evaluate_performance.bus_port...

Permalink Reply by Michael Heaney on February 22, 2011 at 1:37pm

I don't have experience with EPA's Energy Star, but I took a class on it and have talked to other people who have used it.  The purpose of Portfolio Manager is to get Energy Star recognition for existing buildings.  For a local government seeking to document their energy efficiency, Energy Star is a good program, probably better than LEED EB (existing building) which costs more to obtain and maintain. Portfolio Manager is meaningful because it's based on actual energy usage as documented by utility bills rather than points that consider a wide range of sustainability considerations, some of which are controversial. The relative energy usage is compared to other buildings of the same type (e.g. offices, hotels, churches, etc.) based on size, location, number of occupants, and other factors.  See http://www.energystar.gov/index.cfm?c=evaluate_performance.pt_neprs...

However most local governments today are focused on cutting costs, not improving their image.  Portfolio Manager is still a good program for analyzing energy cost and usage, but in the short term it may be viewed as unnecessary overhead cost.  Identifying energy cost saving opportunities and comparing them to previous year data (ideally adjusted for degree days) is the shortest route to cutting energy costs.

 

Permalink Reply by Michael Heaney on February 23, 2011 at 9:24am

I learned yesterday that some public buildings in NC -specifically some school districts - do use portfolio manager as an "engine" to track and improve their performance and to set a goal (e.g. a 75 rating).  The analysis built in corrects for weather, fuel costs, etc.  So Portfolio Manager can be a useful tool even for public facilities with small staffs who are not interested in achieving Energy Star.

Permalink Reply by Bill Davis on February 23, 2011 at 9:45am

We (NC State) have been using Portfolio Manager to track Energy Star certification for our residence halls (3 Energy Star plaques, so far!).  It has a lot of metrics you can track, and it's customizable in the event you have metrics you want that they don't have.  One thing to mention - the real benefit of P.M. is the ability to look at the history of your buildings, so getting historical data into the system is important.  They provide Excel spreadsheets to download and fill in with bulk data.  You can send the file to EPA, and they'll put it in P.M. for you.  I had 20 residence halls with 10-12 years of data (80-100 meters).  It took me 2-3 days to compile the data and format it.  It took them about a week to get it into P.M.  I never would have had the time (or patience) to put it all in manually.