(Issue: August 2019)

It's Not Always About Circadian Rhythms, Tunable White in the Classroom

Submitted by NALMCO General Member ENERGYFICIENT SYSTEMS, INC. in Burlington, Iowa

Contact: Chad Palmer, CLEP, chad@energyficient.com

A case study of the effects of providing color tunable and dimmable features to an elementary classroom. 

Circadian rhythms, human centric lighting can mean different things, they are definitely lighting buzz words today. We wanted to explore the practical side of tunable white lighting in an elementary classroom.   

How would dimming and color tuning control be used in an elementary classroom? The conditions were set up to allow the staff to “discover” the new features of the system and decide on their own how to use them. The study took place over the 2017 school year and the data was collected in 2018. The study was done in a combined 84 classrooms at three separate elementary buildings in a Midwest school district.  

The scope of work included fitting each of the classrooms with new LED, flat panel type light fixtures that were 100–10 percent dimmable and 2700K to 6500K CCT adjustable. We targeted 45 foot-candles for the standard light level on the 4000K CCT setting. The controls used consisted of two Lutron Pico 0-10V dimmers. One with only dimming up and down with no preset and the other was the CCT control which had three presets and up and down as shown in figure 1.  
The data was collected using an online survey. Respondents had to answer all questions in order to complete the survey. We had a 96 percent response rate. There were 71 teachers and eight administration staff that responded to our survey out of a total of 74 teachers and 10 administration staff. We polled only those teachers and staff that used the classrooms with the new lighting.  

The survey was conducted during the month of May. The school year is typically 185 days starting on or about August 14 and ends on or about May 24. The instructional part of the school day starts at 8:30 a.m. and ends at 3:00 p.m., however the staff spends time in the classroom before and after those hours. 

Our survey involved classrooms that were used for teaching grades kindergarten through 4th grade the subjects covered are shown to the left and the staff’s experience varied with 36 percent of them with 10 to 20 years of experience as shown below.

The gender of the staff is mostly female with 75 female teachers and just four men. The age of the teachers was mostly 30–40 years old. 

We asked how they felt about the new features of the lighting. Specifically, we asked about the ability to change color where 82 percent of the respondents said they were happy with the ability to change the color of lighting in their classroom, 16 percent were indifferent about it and one person said they were not happy.  

We also asked the respondents how they felt about the ability to dim their lighting now and 92 percent responded that they were happy with the ability to dim the lights with only eight percent indifferent about it.  

The classrooms were fitted with flat panel type fixtures. Specifying the flat panel was an easy choice for our team. We were attracted to the clean modern look, slim profile, enclosed and low glare optics, dimmability, adjustable color range of 6500K to 2700K, with both 2’x 2’ and 2’ x 4’ shape forms, and its high efficiency. The flat panel is a very versatile fixture for a classroom setting.  

The teachers appreciated our choice in fixture style with over 90 percent of them responding to our survey as satisfied or very satisfied. Making a difference in the classroom was our ultimate goal. We wanted the teachers to have a next generation classroom with another tool they could use to improve the education experience and we wanted to give the district a next generation classroom that would be ready for the next curriculum and attract the next generation of teachers. Over 95 percent of our respondents said the color tuning feature made a positive impact on their classrooms and students. And nearly the same amount said the feature made their classrooms more comfortable for them personally.  

Dimming and bi-level switching is really nothing new to a new classroom design, but these were the first classrooms in the district to have 100 to 10 percent dimming. Originally, they were fitted with just on/off linear fluorescent fixtures. The teachers responded to the dimming feature similarly to the color tuning feature with nearly 100 percent of them telling us the dimming feature made a positive impact on their classroom and students and with the same amount responding it made them more comfortable personally.  

The teachers were also asked how likely they would recommend color tuning and dimming to their peers. With only three teachers responding with not at all likely the majority of our teachers were going to recommend both features to their peers.    

When asked if they were trained in how to use the new color changing feature of their lighting 21 percent of them said yes, even though they were never formally trained or given formal direction.  

Interestingly, there was a small percentage of respondents that were not aware the color of the lighting could be changed in their classrooms and the same said their students also were not aware.    

Ninety-four percent of the respondents said they had changed the color of lighting in their classrooms.  

We wanted to know which color they preferred. So, after prompting them as to which setting was which color, their responses were interesting. It’s easy to conclude based on those responses that teachers prefer bright white color in their classrooms because most of the respondents chose 5000K or 6500K as their favorite CCT. Considering they had to manually adjust the lights to get to the 6500K, it’s fascinating that 35 percent of the respondents preferred that color.  

Over half of our teachers changed the color of their classroom more than twice during a typical day with the other half responding that they changed the color only once per day. We were curious to find out what colors the teachers used and especially how and when they used them. Fifty-one percent of our respondents also said they change color to coordinate with an activity. The responses to how and what they used the colors for is shown below:

This word cloud represents the words used in the response to their description of how they use the color changing feature in their own words.

The positive changes noticed in the classroom that the teachers felt were related to the new lighting features are illustrated here.   

It was speculated that there would be changes in behavior. Thirty-seven percent of our respondents said they noticed changes in behavior that they think are associated with the new lighting. This word cloud are the words they used to describe the changes in behavior they noticed. Forty-one percent of respondents felt changing the color of the lighting helped students concentrate.  

Ninety percent of our classrooms were aware of the new dimming feature in their classroom and all of our respondents used the feature with a full one third of the respondents using the dimming feature more than three times each day.  

What’s the potential energy savings from dimming? To find out, we asked our teachers where they kept the dimming control set at for their “normal setting.” Eight-nine percent responded with their normal setting dimmed by 10 percent with a notable 20 percent dimming by 70 percent According to our survey, 90 percent of most users will dim their lights by at least 10 percent and 40 percent of users will dim their lights by 50 percent or more.  

Seventy-six percent of our respondents said they dim the lights for special activities. Some activities are more suited to dimming than others and our teachers responded with the following activities they use the dimming feature for smart board and projector use, classroom management/quiet time and watching movies/videos. We also received several “other” comments. Most notable, were comments saying they dimmed the lights to their own personal light level.  

There were some of our teachers that didn’t dim the lights according to our survey. Why don’t they dim? We asked those that said they don’t dim the lights and the responses were because they “forget” about it and just aren’t used to having dimming available.   

In conclusion, this school district set out to provide their teachers with new tools in their classrooms to give them a more comfortable classroom and a classroom that would enhance the classroom experience. We accomplished that and added additional energy savings to the project.