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Energy usage in buildings is almost 40% of the total energy consumption worldwide, while we spend 90% of our time indoors. So how can we lower energy consumption in buildings in a good way without compromising comfort?
The building systems and parameters to control
The HVAC system in a building is essential to deliver a good indoor climate and to reduce energy consumption. An important part of the HVAC system is the air handling unit (AHU), where parameters such as airflow, operating time, demand control and temperature are essential to optimize the running of the whole building system and deliver a good indoor climate.
Starting with the correct set-up for the airflow: if the airflow is too low, it may result in people's discomfort, lowering their productivity or causing health issues. On the other hand, if the airflow is too high, one might feel draft, sound issues, and cause unnecessary energy consumption. Lowering the airflow by 10% can decrease energy consumption by 20%.
Making sure that the operating times are correct is another crucial factor. A reduction in operating time will directly reduce the power consumption of the air handling unit. A good tip is also to reduce the operating time, i.e. decrease the airflow or turn off the air handling unit during holidays, or when the building is unoccupied.
Moving on to the indoor climate control system, there are clear benefits of using a demand-controlled system where even the smallest adjustments can make significant energy savings. For example, decreasing airflows when people are not in their office and adapting the flow according to number of occupants according to CO2 levels, can rapidly reduce the power consumption of a fan in an AHU, etc.
The supply air temperature should be slightly under the room air temperature for good air distribution. Lowering the supply air temperature by a couple of degrees Celsius (winter time) and increasing the temperature a bit summer time could save energy without a notable impact on comfort or productivity. Energy recovery ventilation significantly reduces the need for heating and/or cooling. For example, the estimated impact of reducing indoor air temperature by 2 degrees Celsius could lead to a decrease of 20% in energy required for heating (largely depending on the building's characteristics, location and usage, etc.).
The mix of the room's surface and air temperatures is known as the operative temperature. The operative temperature is a factor to consider as it greatly impacts people's comfort and, therefore, is vital to control.
People's impact on comfort and energy
Partially people can adapt their indoor climate comfort in a building by using appropriate clothing in the various seasons, for example, layered clothing in the office dependent on the weather outside. However, one must also be aware of the effect of people's activity indoors, for example, at the office (the prolonged periods of sitting at the office desk) or classroom (one-hour class time with regular breaks for stretching, etc.). Lowering indoor temperature becomes critical when there is prolonged sedentary activity, thus also having a significant impact on people's productivity.
The building's service team can also greatly influence the energy consumption of the building systems by proper maintenance. It is widely known that poorly installed, balanced, commissioned and serviced building systems consume more energy. One of the common mistakes is having both heating and cooling systems simultaneously running in a building, with overlapping set-points, leading to a waste of energy. The service team must also regularly check all set points and the cleanliness of the whole system during maintenance.
The building owners have good maintenance knowledge nowadays, but very often, regular and proper maintenance is lacking. It can be noted that wireless technology will make it easy to maintain the building's systems in today's digital world.
Indoor environment sensors play a huge part in the correct operation of a building. Nowadays, all buildings should have indoor environment sensors to measure parameters such as temperature/humidity, CO2, etc. And the building's occupants (owners, users, visitors) should also be educated on interpreting the values measured by indoor environment sensors.
To conclude, energy-saving actions are individual for every building. However, the goal is always to deliver a good indoor climate for all building occupants.