DEMAND CONTROLLED VENTILATION SOLUTIONS FOR SCHOOL ENVIRONMENTS

Schools are supposed to be pleasant and efficient places with the very best conditions for absorbing knew knowledge. To create that environment, a good indoor climate is required. Conducted research show that children perform better in classrooms with good ventilation because it keeps them alert throughout the day.

Increased learning ability with lower energy use

In a report from Svensk Ventilation (Swedish Ventilation society) you can read about the importance of a perfect indoor climate to maintain an optimal work environment in schools. The ventilation supervision and air quality in schools is partly based on system supervision based on routines for ventilation in the operator's own control program and partly on actual inspections on the premises. In schools, OVK (mandatory ventilation inspection) must be performed every three years according to the National Board of Housing, Building and Planning. The school's self-monitoring  ventilation/air quality program should include written routines to continuously check that the function of the ventilation and the air quality in general is so good that the students stay healthy and alert.

Requirements for ventilation, sound and temperature

The air flow should be 7 l / s and person and 0.35 l / s and square meter and the sound level should not exceed 30 dB (A), which is very quiet. The sound requirement for offices is in accordance with current standards of 35 dB (A) and when 3 dB (A) corresponds to a doubling, it is almost "4 times as quiet" in schools. There is no requirement for ventilation system to operate 24/7.

There are no set temperature requirements which is why cooling almost never is installed in preschools and elementary schools. This can be a problem when choosing large glass surfaces for architectural reasons. Many teachers or office workers that still work during the summer holidays may experience the lack of cooling as annoying. Thus, sun screen control becomes all the more important in order to maintain a comfortable room temperature during May/June and August/September. 

Fixed or variable airflows?

To meet the requirement of 7 l/s and person, you can either let the rooms have flows corresponding to 30 people x 7 l/s throughout the working day or you can demnd control the air flows with, for example, presence- or carbon dioxide sensors.

7 l/s corresponds to about 1000 ppm carbon dioxide and is a prescribed requirement. Therefore, regulating at 1000 ppm entails a stepless regulation of the air flow and thus adaptation to whether there are 2, 10 or 30 students in the school room. A presence detector cannot distinguish whether 1 or 30 students are present. This gives different energy use and can also cause the air to feel unnecessarily dry during the winter months if you ventilate too much.

Sintef in Norway has conducted a study on energy use on the various alternatives presence detector (DCV-IR) and carbon dioxide (DCV-CO2). See the graph on the right. Obviously, you save a lot of energy on choosing demand-controlled ventilation compared to constant air flows, regardless of the sensor, but you are clearly saving most with carbon dioxide sensors.

How many students are at school & how many rooms are in use?

A lot of studies have been performed on this subject. The conclusion is less presence and less use of classrooms and halls than expected. The graph on your left shows the occupancy of used schoolrooms at a typical high school. The fact that the school halls are almost completely empty after 14:30 on Wednesdays, is something that shows how important it is to have a demand controlled system for ventilation instead of  a fixed time channel that doesn't follow the school schedule. To also use the possibility of lowering the temperature to economy mode saves lots of energy.

How do we ensure a good indoor climate?

A perfect and well ventilated indoor climate is essential for children to feel good and stay alert. It also increases their ability to absorb new information and learn new things. Is it only through costly OVK inspection (Mandatory ventilation inspection) inspection that we can find out if the indoor environment is good enough?

The answer to this is no. The feedback is too slow and insufficient. With a demand controlled system connected to an intuitive web interface, facilty managers and operators can control airflow, carbon dioxide levels, pressure and presence in the premises in minutes. This allows them to verify data and adjust the system via a tablet, making everything more simple, comprehensive and better. The web interface can also be used to evaluate booking status if using data from integrated inhouse booking systems.

Svensk Ventilation (Swedish Ventilation Association) about the school environment


In a report from Svensk Ventilation (Swedish Ventilation society) you can read about the importance of a perfect indoor climate to maintain an optimal work environment in schools. The ventilation supervision and air quality in schools is partly based on system supervision based on routines for ventilation in the operator's own control program and partly on actual inspections on the premises. In schools, OVK (mandatory ventilation inspection) must be performed every three years according to the National Board of Housing, Building and Planning. The school's self-monitoring  ventilation/air quality program should include written routines to continuously check that the function of the ventilation and the air quality in general is so good that the students stay healthy and alert. Below you can read about the municipalities' view of school working environment and the conditions for taking part in the new state aid for school transitions.

School should be a pleasant and efficient place, optimised for learning

To create such an environment, a good indoor climate is required and researcher David Wyon's report shows that children perform better in well-ventilated classrooms and it also reduce allergy problems. Proper temperature and air quality in the classroom increases students' performance by as much as 30%. At the same time, responding to environmental requirements and keeping energy consumption at minimal levels, may seem impossible. With lower indoor temperature and higher air quality, performance increases. Students with poor learning ability actually have even more difficulties in case of the opposite.

"The experiments were conducted on behalf of ASHRAE, the American Plumbing Technical Association, with the aim of seeing how air temperature and outdoor air supply affected performance. Neither teachers nor students knew that they were part of a study. Like most other schools, the school had classrooms. in a south facing position with large glass windows and good light, as well as an outdoor air that was clean because the school was close to the sea.

"Normally, the indoor temperature was 23.5 degrees. We took it down to 20 degrees and our research showed that for each degree we lowered the temperature, performance improved by 3.5 percent. If we assume that the temperature on a really hot summer day rises to 30 degrees in a classroom, then the performance ability of the students drops by 35 percent, says David Wyon." Source: Swedish Ventilation.


"The experiments were conducted on behalf of ASHRAE, the American Plumbing Technical Association, with the aim of seeing how air temperature and outdoor air supply affected performance. Neither teachers nor students knew that they were part of a study. Like most other schools, the school had classrooms. in a south facing position with large glass windows and good light, as well as an outdoor air that was clean because the school was close to the sea.

Articles (swedish)

Bra luft i klassrummet ger 30 procent bättre studieresultat - Svensk Ventilation

Inomhusluftens betydelse för en god arbetsmiljö i skolan - Svensk Ventilation

Assessment of ventilation/air quality

Supervision of ventilation and air quality in schools is partly based on system supervision and routines for ventilation in the operator's inhouse control program and partly on actual inspections in the premises.

Guidelines on what airflows are needed in schools and other information that is important to know about supervision (swedish):
Public Health Authority General Council 2014: 18 on ventilation
Supplemental guidance on ventilation

BBR, Boverket's building rules (The Swedish National Board of Housing, Building and Planning)

These regulations contain regulations and general advice for the Plan and Building Act, PBL. The law text is general and gives few specific numerical values:

“Buildings and their installations must be designed so that they can provide the conditions for a good air quality in rooms where people stay more than temporarily. The requirements for the quality of the indoor air must be determined based on the intended use of the room. The air must not contain pollutants in a concentration that causes negative health effects or troublesome odors"

In the case of air flows, the following is stated:
“Ventilation systems shall be designed for a minimum outdoor air flow equivalent to 0.35 l / s per m2 of floor area. Rooms should have continuous air exchange when used. "

Since there are almost no specific requirements, you have to verify compliance with the law. This can be done by calculations or measurements, but also by following advice and regulations from the proper authorities. 

BFS, Boverket's constitution

The Housing Agency also issues regulations on mandatory ventilation control, OVK, which must be done every three years for schools. During an OVK inspection, it must be verified that society's requirements for hygiene, health and the environment in regards to the air quality are fulfilled.

AFS, The Swedish Work Environment Authority's constitution

The Swedish Work Environment Authority works to ensure that laws on working environment and working hours are followed by companies and organisations. There are around eighty regulations that deal with various matters concerning workplaces. The Occupational Safety and Health Act applies some what even outside the professional life. Thus students, carers and conscripts are  equal to white collar workers. Therefore, in the school premises, the Swedish Work Environment Authority's regulations also apply to the students' work environment. The most relevant regulations regarding ventilation are:

• Workplace design, AFS 2009: 2

Here you'll find advice on airflows per person, highest CO2 level, lowest exhaust airflow for certain premises etc. There are also requirements for the design of safety ventilation such as flow benches etc.

The Public Health Agency

The task of the Public Health Authority is to develop and disseminate scientifically based knowledge that promotes health and prevents diseases and injuries. The Public Health Authority publishes writings in a constitutional collection and has issued a writ that specifically relates to ventilation.

• FoHMFS 2014: 18, General advice on ventilation

Regarding schools, this can be summoned as:
“In schools and childcare facilities, the outdoor air flow should not be less than about 7 l / s per person in sedentary employment. An addition of at least 0.35 l / s per m2 of floor area should be made so that contamination from sources other than humans is also taken into account. If the carbon dioxide content of a room regularly exceeds 1,000 parts per million (ppm) in normal use, this should be seen as an indication that ventilation is not satisfactory. "

 

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