Save energy but do not sacrifice the indoor air quality

by Professor Olli Seppänen

Nordic Ventilation Group (NVG) works for better performance and understanding of ventilation and its effects.  Topic is now more important than ever. Good ventilation is essential for good indoor air quality, and health of the building occupants. It is known that proper ventilation improves the productivity, learning, health, and even sleeping. During the Covid pandemic it has been shown that efficient ventilation reduces the infections caused by the virus particles in the air.

The other side of the coin is the fact that a lot of heating or cooling energy escapes from buildings with exhausted air, totally it can be 5-10% of total national primary energy use. Most of the new buildings in Nordic countries recover the heat from the exhausted air by heat exchangers, in some countries heat recovery is mandatory even in the residential buildings. This reduces significantly the energy need of buildings.

Energy saving is currently the focus in EU. Energy use could be reduced drastically by stopping heating and ventilation, of course, this should not be done. If space heating and ventilation is reduced, it must be done very skillfully so that the indoor environmental quality is not deteriorated. Severe moisture and IAQ damages, caused by low ventilation and heating are still in the mind of professionals.

Hopefully, current need to reduce energy use do not repeat the mistakes done before. It is extremely important to maintain adequate ventilation in the occupied spaces of the buildings. Energy savings can, however, be achieved targeting heating and ventilation better into the rooms and areas where occupants are. Empty or partly occupied room do not need the same amount of ventilation or even heating than fully occupied spaces. Large potential for energy savings can be achieved with the better targeted ventilation and heating.

HVAC systems can be complex and require regular maintenance and adjustment to the changes in the use of the building. Regular inspection of ventilation is needed. Inspection is mandatory in most countries in the new buildings but not in existing.  Need for regular inspection has been realized, first in Sweden, where the ventilation inspections have been mandatory already since 1991. In Finland an official guide for inspections was published in September 2022. Experience has shown that regular inspections are necessary, particularly for the complicated systems, like demand control ventilation (DCV).

Recent Nordic Ventilation Forum showed that the problems in ventilation performance are very common in DCV systems in all Nordic countries. Improvements are needed in the construction process, equipment, automation, IAQ-indicators, and many other areas. Covid pandemic has shown that better controlled ventilation should be available in fight against air borne infections. Current systems are not able to vary ventilation rates at as large range as required for good energy efficiency and air quality. New criteria for ventilation rates and design are needed and put in practice.
A major task of NVG is to collect, develop and share the knowledge of the better performance of ventilation. The current activities of NVG are focused on the lessons learned from the Covid pandemic for better design and operation of ventilation including new criteria of design ventilation rates, control by demand, use of sensors in practice, effectiveness of ventilation, and use of air cleaners to assist ventilation.

This blog offers a platform to the NVG members to express their ideas to a larger professional audience. In a long run it will be a significant source of information to bodies involved in development of new ventilation and IAQ technology.