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Weekday summer afternoons will usually find me in my office, huddled under a blanket. I work on the fourth floor of Building S on the SAS campus, with most of the other JMP staff. It seems cold in my office in the afternoons, especially in summer. I’ve discovered I’m not the only one, and one theory is that the air conditioning gets cranked up during the hottest part of the day. However, other colleagues are cold in the mornings instead, leading to a second theory that office temperatures are affected by whether they get the morning or afternoon sunlight. A third theory is that the people in the offices are just warmer or colder by nature. Determining what factors influence office temperature is a problem JMP can help us solve.

JMP can help us design an observational study. First, we’ll brainstorm a list of possible factors that may affect office temperature. Next, we will use JMP’s design of experiments (DOE) platform to design a way that we can record the appropriate information.

Possible factors that affect office temperature are:

Office – There are 90 offices on this floor, and we want to sample all of them for each recording period.

Time of Day – Morning and afternoon. In our building, this seems as if it might affect the temperature in a number of offices.

Outside Conditions – Rainy, sunny, cloudy, etc. The weather and amount of direct sunlight could certainly affect the inside temperature.

Outside Temperature – Could extreme heat versus mild heat have an effect on what the temperature was indoors?

Type of Space – Interior offices versus exterior offices, larger offices versus smaller offices, common rooms versus private rooms. Any of these could have an effect on office temperature.

Thermometer – We have nine different thermometers available to take samples with. We want to control for variations among the thermometers.

East/West – Those with offices on the east side of the building might expect to have warmer temperatures in the morning with the sun shining into the windows.

Wing – Does the north wing of the building differ at all from the south wing?

Floor – Heat rises, so they say. Would offices on higher floors have a higher average temperature?

Volunteers – Sampling 90 offices multiple times is a large experiment, and we would need many volunteers. Different people may hold the thermometer differently, and some will be more patient than others.

When I first entered all of the factors in to JMP’s design of experiments platform, the number of runs required was more than 20,000. This was too many, and we had to sit back and consider the practical applications of this experiment. How could we take all factors into account and still have a manageable experiment? The number of offices (90) and potential large number of volunteers were greatly increasing the number of runs. To make the design manageable, we divided the floor into nine “sectors” of 10 offices each. A sector is completely arbitrary, but it makes the office chunks manageable for the purpose of giving assignments and taking measurements and reducing the number of runs. We chose nine sectors because we had nine thermometers.

Our final list of factors in DOE looked like this:

A few notes about the factors:

• The factors we cannot know in advance are specified as “Uncontrolled” factors. Outside temperature and outside conditions are beyond our control; we will make note of their values because we think they may have an effect. A third uncontrolled factor is volunteers, since we had no way of knowing who our volunteers would be each day or how many we would have.

• There are a few other factors not shown in this design, such as type of space and east or west. We will add these factors to the model later. Each office has a known value for these variable which will not change over the course of the experiment.

• One factor from the above list was left out completely: floor. It would be interesting to conduct an experiment that compared offices on various floors, but for this study our hands are full with a single floor.

We determined that three days would be long enough to get multiple observations per office, without being so long as to run out of volunteers or wear out our welcome. We wanted each office measured twice per day, or a total of six times. This translates to 54 “runs," where one run consists of one sector assignment of 10 offices. For design generation, we’ll group runs into three random blocks to represent the three days the study will last. That means the blocks are each of size 18.

This is manageable, although admittedly we might have cut a few corners in order to reduce the amount of work we need to do. Remember, this is intended to be an observational study to help determine what factors are most likely to affect office temperature; this is not a rigorous experiment. Here is a look at our finished design.

This post is the first in a series that will show how we conducted this observational study, from design to execution to analysis and visualization. In the next post, you'll see how we managed to sample 90 offices in an orderly fashion and how the data was assembled.

Can you think of any other factors that might affect office temperature? What might we have left out?

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Visitor

I just realised that you are probably acting in a scenario where you want to get the temperature "up" to an ideal temperature.

Being from "down under" I was starting on an assumption of "cooling down".

Anyway, to my comments. It's worth checking out whether ceiling and wall insulation is uniform throughout the building. We discovered a whole two zones were inexplicably ignored when it came to insulation, and it's one of those "invisible" factors which could easily affect multiple zones.

Heat loads from windows (double glazed??) and other insulating areas (door jambs etc.) might have quite an impact on a given zone.

Visitor

Melisa Turner wrote:

When determining the type of office space (interior/exterior, etc...) another factor may be what's across from that office. I have an office that is across from the the large fire doors (which are open 99% of the time). There isn't a wall or other office blocking the flow of air from the atrium to my office. I find this makes my office colder than others. This may not be an issue in other buildings though.

I'm very interested to see if there's an actual temperature difference or of it's just perceived. Although it wouldn't impact the results, it might be fun to have each volunteer tell whether they think their office is too warm, just right or too cold.

Visitor

Ellen Daniels wrote:

Have you considered the effect of humidity on the perceived comfort level? I have heard that men and women react differently to temperature ranges vs. humidity ranges.

Visitor

Daniel wrote:

I love it! A DOE for all of us building energy nuts!

The other factors that affect our perception of temperature are the relative humidity level, amount of air movement, and the person's clothing and activity level. For instance, if you have a lot of plants in your office, the humidity will be higher, and you'll feel warmer!

Your facilities group may be over-cooling the air in the summer to reduce the humidity levels. Often times, raising room temperatures during the summer time here in the south increases energy use, as we have to re-heat the air before it reaches the room.

Anxiously awaiting the results...

Visitor

Bonnie Watts wrote:

In addition to what Ed Webb said about the HVAC, since there are more than one HVAC zone, does one zone affect the other zone as to when one shuts off and the other turns on or the length that it stays on, etc.

Visitor

Wes Avett wrote:

I just scanned the article but didn't see anything about the office door position. I've seen a big difference in temperature depending on the door being completely open, completely shut or inbetween.

Visitor

Ursula Hagstroem wrote:

This is so great. I have been waiting for this study, since I am freezing in my office all the time and others say it's warm in their office. A factor might be the vents in each office. Some of the offices might have half shut vents, some might be open. Also I think it depends if you have a room with a window. Those seem to be warmer (obviously).

I am excited on the outcome.

Visitor

Tom Disque wrote:

I think exterior vs. interior office locations are the main culprit. My office has a window to the outside; it's at least 10 degrees warmer on average than a nearby interior office. Wall insulation (or lack thereof) might be a factor here.

How about male vs. female? In social settings, I've often noticed that when the men are comfortable, the women are freezing. When the women are comfortable, the men are sweating.

Visitor

Jeff Alford wrote:

Audrey,

Have you given consideration to whether office doors are typically open or closed? I imagine that this could have a signficant effect on room temps.

Visitor

Anonymous wrote:

Neat blog!

This is a pretty good list of factors that you are considering in this experiment. For how you divide up the offices, it might be better to check with facility to see how they control room temperatures - they might have a way of dividing up the offices to separately control them.

I am looking forward to seeing the data, and see which factor(s) are the main ones to contribute to room temperature.

Visitor

Gary Burchett wrote:

Another issue to consider is that different people will react perceive the same temperature differently. Are there characteristics of the observers that are affecting their perception? Could time of day be a factor as well in this perception, such as before or after lunch, did they they go to the gym, did they return from outside, etc. In other words, can you identify quantitative differences in the observers that could be the cause of their qualitative observations about the temperature? I believe adding this would seriously complicate your observations.

Visitor

Anonymous wrote:

The computers in use give off some heat thoughout the day. There are 90 offices, most with 2 sometimes 3 machines. Many offices have multiple monitors. Also, there are several labs and a basement full of servers. More incandecent light bulbs being on longer, etc. This effect is most likely small and I realize the AC units regulate this heat. Just a consideration. Maybe people working near yellow lights and busy servers (in office or near labs) are staying warmer?

Visitor

Ed Webb wrote:

You failed to include the HVAC (heating, ventilation, air conditioning) system itself. You mentioned dividing the floor into nine zones because you have nine thermometers. But do your zones match those of the ventilation system. How many thermostats are on the floor? If each thermostat represents a ventilation zone and that zone matches your arbitrary zones, then your results are OK and could be used to improve conditions. But if your zones don't match the actual HVAC zones, then the results, though interesting, cannot be acted on. And is each HVAC zone controlling one HVAC unit acting independently or do the thermostats make decisions as a group, driving one or more HVAC units outside?

Perhaps Facilities can help you refine your zones to match the HVAC zones and provide some more info about thermostats and their relationship to the fans in vents or to the actual HVAC units that heat and cool.

I look forward to hearing about your results because we have similar issues in my building.

Visitor

Alan Lorden wrote:

Other factors could include heat generating equipment in the offices. For example I have 4 Dell desktop computers in my office that give off a considerable amount of heat.

Another factor to consider is whether a person works in their office with the door open or shut. This seems to make a big difference in airflow especially in the smaller offices.

Visitor

Michael Muha wrote:

How about checking with facilities beforehand, to make sure no temperature/air flow settings get changed during the three days? Or checking with facilities after the runs, to see if there were any mechanical, electrical, thermostat changes, or other issues during the three days?

Visitor

Anonymous wrote:

Having your office door open or closed can affect the temperature. And the type of lightbulbs used in the office does also (halogen bulbs generate more heat than flourescent bulbs).

Visitor

Jean-Louis wrote:

One important factor : the presence or not, and number + power of machines (PC, printer, screen, radio, own coffee machine, ...) in that room.

Another one : number of persons working in that office

Visitor

Anonymous wrote:

Have you considered internior offices versus window offices?

Visitor

Johnny wrote:

you need to consider radiant heat from light fixtures and machines and their proximity to the thermostats.

Visitor

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Visitor

Mike Luckenbill wrote:

No need to read your article in total .. I worked for 40 years in offices and only one was perfect all the time. Normal problems

1. Many offices are on a floor of a building that has removal walls ... after 2 or 3 tenants .. who knows where the thermostat is?

2. Huge systems are either all heat or all cool. That causes grief.

3. Windows don't open. Give me a break !!!!

4. Some people want it hot all the time hence a heater under the desk.

Best ever office:

Individual control for each room was nothing more than a remote control to a air flow control valve per office. Heat or cool always available. Windows would open.

It was great !!