Reducing energy costs during heatwaves and maintaining work performance
Yesterday, a colleague called me - 32 degrees Celsius in his office, but only 24 degrees in mine. How can that be? Germany, Europe is suffering from heatwaves this summer and discussions on climate change are once again up with people and governments. Apart from the general and very serious consequences such as cardiovascular problems, heat stroke, death of people, and further fuelling devastating forest fires, the heat represents a considerable risk for companies too. From about 24 degrees Celsius, work performance decreases - at 30 degrees by almost 9 percent - and affects even healthy and young people. Especially workers outside, such as roofers, road and construction workers, are exposed to high temperatures; but also in offices, production and storage places, and shops the heat accumulates.
In this context, the German legislation specifies in the Technical Regulation for Workplaces that the temperature in workspaces should not exceed 26 degrees Celsius as a matter of principle. From 30 degrees on, the employer must take measures, and 35 degrees is the upper limit. Here, heat work can only be performed by means of very special measures, such as protective suits.
So, what can companies do?
High temperatures and heat waves like this will be the norm in the near future, not the exemption. Will the massive installation of air conditioning systems be the solution? A problem is that these consume a lot of energy, thereby causing significant additional costs, and also further heating up the outside air. A look to Australia, where high temperatures are commonplace in large parts of the country, reveals interesting perspectives on efficient passive cooling options for buildings. Australia‘s Guide to Environmentally Sustainable Homes recommends exploiting all passive options first before possibly using air conditioning for the remaining heat gap to be reduced. This saves energy and considerably costs.
What is the principle of passive cooling?
reduce the heat input into the building via shading and insulation
promote heat extraction from the building through appropriate ventilation and supply of colder air.
And how can you put this into practice?
In principle, proper ventilation is based on air flowing from the area of high pressure to the area of low pressure. There is high pressure on the side of the building facing the main wind direction. The air should therefore be able to flow freely from there to the opposite side (= cross ventilation).
Low pressure also occurs where warm air can ascend. Colder air (e.g., the night-time outside air or ground air) then flows passively in to compensate the low pressure. The flow works best in narrow spaces, such as corridors, stairwells, or narrow rooms. These principles can be considered in building and window design, and ventilation schemes. When it comes to night ventilation, there are often safety concerns about leaving windows open. However, this problem can be addressed with special vents.
Making sure in planning that heat-sensitive areas are located to the north, in lower levels of the building, or capsulated inside the building will reduce additional cooling demands. Even in an existing building, it is often still possible to optimize the use of space.
Blinds mounted on the exterior are much more effective than those mounted in the interior, since less heat gets inside behind the window screen. Wide canopies are very effective too, especially if they cast heavy shade. At the same time, they let in daylight. It all comes down to the right sizing of canopies and blinds, their location and orientation, as the position of the sun varies depending on the time of day, orientation and season. In winter, after all, sun radiation is often desired.
Insulation can also help against heat gain in buildings. It can be achieved both technical insulation materials and green facades and roofs. The latter have the advantage that they offer an additional cooling effect by evapotranspiration. But beware, once heat has entered the building, the insulation also holds it back for a longer time. Accordingly, insulation should be designed in combination with shading measures.
Colour of roofs and exterior walls
Here, the principle is the lighter the more radiation is reflected and the darker the more heat is absorbed and retained. So: light colours are the choice.
A roof space with good ventilation can provide a valuable temperature buffer to the interior.
Vegetation in front of the building ensures cooler outdoor temperatures. Trees or pergolas and espaliers are in particular effective in contributing to this effect by the dual effect of shade and evaporative cooling.
Even if these do not cool the air temperature, they can still distribute effectively the (cooler) air in the room. The perceived temperature of the moving air is lower than when it is not moving. Fans consume much less energy than air conditionings. Ceiling fans are particularly effective in this regard. If air conditionings have to be used, the additional use of ceiling fans can reduce their energy consumption by up to 75% due to better air distribution in the room.
This is only a selection of the many possibilities of passive cooling. The organization and design possibilities are manifold and should be selected and combined according to the specific building and its location. Only then, they can achieve their full service and avoid or reduce the use of conventional air conditioning systems, thus helping to reduce energy costs while maintaining work and production capacity.
See more options in Australia‘s Guide to Environmentally Sustainable Homes
Do you want to find out how your company is affected by heat and other climate change impacts and develop solutions?