As the energy crunch really starts to bite, we need to remember one the basic reasons that heating, ventilation and air conditioning systems should be kept clean. It’s not only a question of hygiene, air quality, fire safety and comfort:

A dirty system cannot function as designed

A clean system uses less energy.

One of the most important studies in this field came from the Danish Building Research Institute back in 1997

Summary SBI (Danish Building Research Institute) Report 280:

‘CLEANING OF VENTILATION SYSTEMS IN MULTI-STOREY RESIDENTIAL BUILDINGS’. The effect of cleaning on ventilation system´s performance and electricity consumption’, Jan Bach Nielsen (Aalborg University, Denmark). ISBN 9788756309585

5 systems were tested over a period of 4 years

1 comprised exhaust only and 4 systems were ‘balanced systems’ with exhaust and supply

Conclusion: 

On average the total airflow fell as follows per year:                 Exhaust 5,4%         Supply   1,2%

Cleaning of the systems showed that an average of 77% of the reduction was due to the soiling of the system. The reduction close to the grilles was considerably greater

On average, the specific electricity consumption of the fans rose 5% per year over the study period of 4 years. Of this, up to 80% on average was due to soiling of the systems.

 

Since then, a number of studies have confirmed the obvious fact that a dirty system is less efficient and uses more energy. That could be due to clogging of components such as heat exchange coils – the ASHRAE study showed 10-15% energy savings from cleaning main AHU cooling coils, thus reducing pressure drop and increasing thermal effciency. In other instances, the simple effects of turbulence caused by a rough, dirty surfaces, rather than the designed smooth surfaces of galvanised sheet steel, are implicated in increasing resistance and thus energy to move the air.