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How To Increase Indoor Air Quality When You Live In The North

Ah winter. The coldest part of the year. In some parts of the northern US, winter is a time of not just cold, but extreme cold. When -20⁰ with the wind chill is normal, sundogs are a regular (albeit beautiful) sighting and it’s so cold it can’t even snow.

For K12 schools in these areas, it’s hard for administrators to justify cancelling school when it’s absolutely frigid simply because there are too many of those days each year. So, what to do? Keep the kids inside and keep the buildings warm. But how? This is an expensive challenge many school administrators in the far north face each and every year. Add to that the ever-rising number of absences due to sickness each winter and you’ve got two big problems. But what if you could solve both issues with one solution?

As engineers, we know there is a direct correlation between high absences due to sickness and the way in which many school buildings in the far north are heated each winter. The fact is, northern winters are rough. From about Omaha, Nebraska and south, induction displacement is an excellent HVAC system for schools. But for districts located further north, those students, teachers and other staff are forced to occupy buildings that, we believe, could be operated better. Most facility directors and school administrators are happy as long as the rooms are warm, but as engineers, it is our duty to look beyond warmth and design properly ventilated spaces. In fact, the code requires this of us.

As an MEP engineering consulting firm with several locations across the upper Midwest, these two problems had plagued our team members up until recently. At this point, we’ve tackled them head on with several of our K12 clients. And while the traditional induction displacement ventilation systems work great for most of the country, these two unique problems called for one unique solution. Obermiller Nelson Engineering (Obernel) team members worked with Titus HVAC to come up with a solution that not only ventilates rooms at the code-required rates, it also keeps these spaces warm.

Surprise, Surprise: Northern Winters Are Colder Than Most

According to Current Results, a weather and science facts website, North Dakota is the second coldest U.S. state, second only to Alaska. Minnesota? Right behind them. Then comes Maine and Wisconsin. These are real temperatures, where real people choose to live, and just because it’s cold doesn’t mean you get a day off school. The show, er, school must go on!


“The first time we got involved in a project utilizing induction displacement units was in Bismarck {N.D.},” said Paul Nelson, Mechanical Project Manager in Obernel’s Minneapolis office. “At that time, there was one way/name in induction displacement units, but we were hopeful to find an option that would better suit our area where it’s so heating dominated. It wasn’t so much about the number of months out of the year that we’re in heating mode, but instead our focus was on finding a solution for the severely bitter temperatures we experience. It pushed us to deal with heating a little bit differently. So, we started to talk to a few different manufacturers, about the approach to induction displacement and we helped develop a slightly new take on the technology that’s a better fit for our climate.”

Poor Ventilation = High Absence Rate

The problem here is that because it’s so cold, many schools just focus on getting the building warm. While that is certainly important, it’s not the only thing that matters. It is just as important to properly ventilate these classrooms. Without proper ventilation, all the germs from all the kids just keep re-circulating in every classroom. Picture breathing in all that air, over and over again. Thinking about it this way, it’s no surprise we see more kids taking sick days in winter than the warmer months. Say it with me, indoor air quality.

You wouldn’t want to breathe in the same air as this sick kid would you? The point is, if a school district values providing the best learning environment to their children, then indoor air quality should be one of their top priorities. While trying to prove what causes such a high amount of sick days in the winter is tough, there have been many studies that indicate poor indoor air quality as one of the leading causes. It is simply not good enough to only focus on maintaining a comfortable temperature.

According to the U.S. Environmental Protection Agency, failure to prevent or respond promptly to IAQ problems can “increase long- and short-term health problems for students and staff such as cough, eye irritation, headache, allergic reactions and, in rarer cases, life-threatening conditions such as Legionnaire’s disease, or carbon monoxide poisoning.” In contrast, good indoor air quality is an important component of a healthy indoor environment and can help schools reach their primary goal of educating children.

In addition, a study from the Journal of Toxicology and Environmental Health, a peer-reviewed public health journal covering environmental toxicology, indicated that “poor air quality may impact children’s health – specifically respiratory health, attendance, and academic performance.”

Good News: You CAN Get the Best of Both Worlds

There are a bunch of different options for heating, cooling and ventilation systems. A few that are worth mentioning for this article are:

  1. Displacement Ventilation: it’s been around a long time
  2. Active Chilled Beams: these are usually in the ceiling and do a typical mixed-air distribution
  3. Induction Displacement Units: these bring together active chilled beams and displacement ventilation.

The system we helped develop takes induction displacement one step further. It’s induction displacement ventilation plus a dedicated heat outlet. We set out to solve the problems caused by simultaneously heating while also ventilating through displacement ventilation.

The problem is not about the number of heating months, it’s about finding a way to offset the extremely cold temperatures we deal with. This problem is not a function of how many days our buildings operate in heating. It is a function of the design temperature (the coldest temperature we need to account for).

“We recommend induction displacement ventilation with a dedicated heating outlet. The principles of heat transfer tell us that heat wants to go from areas of high temperature to low temperature. With our design-strategy for classrooms, we neutralize this heat transfer through the exterior envelope, (walls, roof, slab on grade, etc.), by designing to have a vent blowing hot air up the outside wall of the building. This way, students and teachers don’t feel the cold seeping in from walls,” Nelson said. 

By pushing hot air up against that wall, it’s like sacrificing that energy to go towards the heat loss that’s already going through the wall. Now that the envelope heat loss has been accounted for, even on the coldest, sub-zero day, the room will be neutral, (meaning it won’t need any additional heat), if the space is unoccupied, and when the room is occupied it will actually require a little bit of cooling.

In an occupied room in this situation, having cooler air flow throughout the room would feel very comfortable. The air is flowing through the room at a very slow speed (i.e. no feeling of draftiness), and that flowing air is slightly cooler than the room temperature air (i.e. no feeling of stuffiness). People are giving off heat, the lights are giving off heat, the projector the teacher’s using to go through their lesson is giving off heat. The room is getting fresh air that’s slightly cooler than room air. As it flows out across the floor and passes by people, they warm up that air, which then creates a current of air that goes up across their face and up to the ceiling. At this point in this occupied classroom setting, when the kids exhale, their germs (and whatever else they’re exhaling or coughing) go up to the ceiling and eventually out of the building through the exhaust system.

So, if you’re considering induction displacement without a dedicated heating outlet to offset the envelope heat loss, then you must heat the room with your displacement ventilation. As soon as the temperature of the room is 3-4 degrees above the room temperature, the displacement airflow stops completely and goes right up to the ceiling. Because the air is moving very slowly, there’s nothing pushing that air out across the room. It’s just kind floating. Once that air gets warmer than the room air it becomes more buoyant than the cooler room air. There is no denying that the result of this approach is a comfortable room, but we lose the ability to ventilate effectively and you certainly aren’t displacing anymore.

Forcing the kids’ germs to go up and out creates better indoor air quality. One great way to accomplish this is with displacement ventilation, and we believe induction displacement with a dedicated heating outlet is a great option for those of us crazy enough to call the cold north, home.

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