A well-tempered indoor climate is the decisive factor for a high level of working and living comfort in buildings. At the same time, efficient energy management is becoming crucial for sustainable building planning in times of scarce resources and rising average temperatures. New regulations also make an effective cooling load calculation program an absolute necessity. Nevertheless, the cooling load calculation rule of thumb can provide an initial overview of the cooling capacity likely to be required.
On cold winter days, a carefully planned heating system ensures efficiently heated rooms; in summer, a correctly designed air conditioning system guarantees pleasant coolness despite the increased solar radiation. In both cases, a cooling load calculation program helps with the dimensioning of appropriate systems.
The basis for this is a precise cooling load calculation in advance. This is the only way to determine the power required to achieve the desired temperature. There are some essential factors, guidelines and parameters to consider. In this article, we break down the most important elements in detail.
The most important facts at a glance
A cooling load calculation program can be used to calculate the required cooling load of a building
The VDI 2078 guideline is decisive for the detailed calculation in rooms and buildings
Simplified rough calculations provide a rough overview of the required output
What exactly is a cooling load and what types are there?
The cooling load calculation is a procedure that helps planners and tradespeople to determine the appropriate output of cooling appliances. The specifications of the VDI 2078 guideline on "Calculation of thermal loads and room temperatures (design of cooling load and annual simulation)" are taken into account.
Although the guideline is not legally binding, it has proven itself in practice and summarizes all relevant rules and recommendations of the current state of the art.
The cooling load calculation according to VDI 2078 enables a comprehensive calculation of the cooling load, room air temperature and operative room temperatures of all rooms, regardless of their air conditioning. All factors that influence the thermal room behavior are taken into account. This guideline therefore provides a reliable basis for effective room air conditioning and ensures a pleasant room climate.
In Europe, the cooling capacity is specified in kilowatts (kW), while some non-European manufacturers use the capacity specification in BTU. 1000 BTU corresponds to 0.2931 kW.
A distinction is made between different types of cooling load.
External cooling load
Basically, the cooling load calculation involves combining external and internal heat loads. This is the only way to determine how high the cooling requirement is in the respective property. The external loads, which are strongly influenced by the orientation and architecture of the building, include
Radiant heat through windows, floors or doors
Transmission heat through exterior walls, roof surfaces and non-air-conditioned neighboring rooms
Internal cooling load
The term refers to the climatic interior of a building and takes into account factors that depend in particular on the use of the respective rooms. These include, for example
Equipment (electrical appliances, computers, screens, etc.)
Users
Machines
Neighboring rooms
Technical processes carried out
The difference between sensible and latent heat
The cooling load calculation is one of the most important elements in planning optimum room air conditioning. It can be used to determine the cooling capacity required to create a comfortable and productive working environment. In the calculation, the distinction between sensible and latent heat is crucial for a correct result.
Sensible heat is the energy that is transferred by heating or cooling air. Latent heat is any type of heat that is transferred by chemical or physical processes.
Both have an effect on the room temperature. Sensible heat has a direct effect on the air temperature and therefore on the room climate. Latent heat, on the other hand, does not occur in the form of a change in temperature, but in the form of a loss or increase in humidity in the room and therefore also causes a change in the room climate.
Both types of heat are essential when calculating the cooling load. For this reason, an efficient cooling load calculation program should be able to take both sensible and latent heat into account. This is the only way to achieve an optimum level of cooling capacity in order to create and maintain the desired indoor climate.
Why is the cooling load calculation so important in building planning?
It plays a decisive role in the optimization of indoor climate control. It helps building planners to determine the optimum performance of a cooling system.
The cooling load calculation can be used to determine which cooling system is best suited to a building. It provides results on the required power consumption, the type of cooling system, the materials to be selected and technical parameters. This allows you to select an energy-efficient system based on this data in order to achieve optimum temperatures in a building.
The cooling load calculation also helps you to create a realistic budget for your project. The calculation provides information on how much energy you will need to adequately air-condition your building. This makes cost management much simpler and more precise.
How is the cooling load calculated?
In principle, the cooling load can be calculated in two different ways: As a simplified approximate cooling load calculation or in a detailed calculation based on VDI 2078.
Approximate cooling load calculation - The cooling load calculation rule of thumb
A detailed calculation can only be implemented correctly with the appropriate software and requires precise knowledge of the respective room and building parameters in order to deliver correct results. However, this information is not always available.
A rough estimate can therefore be provided by a rough calculation. This involves
Ceilings, floors, windows and walls measured and the dimensions noted
Alignment and heat input of the components determined
internal loads summarized
the cooling requirement is calculated using the determined loads.
Especially if data is missing or in the event of an acute system failure, a rough calculation is the quickest way to obtain at least a rough overview of the required output.
The following rule of thumb applies for a simplified calculation: An optimally insulated building requires approx. 30 watts of cooling capacity per cubic meter of room volume.
Although the formula provides an estimate, it does not take into account any details of the design, usage data or dynamic external factors. As a result, the requirement determined in this way is usually somewhat higher than a well-founded computer-based calculation.
Data-supported to the ideal room climate: the cooling load calculation according to VDI 2078
The requirements of the directive can be of great benefit when planning cooling systems in buildings - despite the relatively strict specifications.
It provides precise rules for calculating the cooling requirement based on data such as room size, usage, heat sources and outputs as well as the outdoor climate. A precise calculation allows the required maximum cooling load to be determined exactly, which can help cooling systems to work much more efficiently and cost-effectively.
Too high or too low a cooling capacity can lead to an inadequate indoor climate or cause unnecessary energy costs. In addition, an accurate cooling load calculation can help the cooling system to last longer and require less maintenance, as only the exact amount of air within a room is dissipated.
The use of modern calculation software such as Trimble Nova makes it easier to create a precise performance simulation. The relevant parameters can be clearly summarized into an overall calculation and embedded in a seamless BIM workflow, even for complex systems.
What must a cooling load calculation program contain?
Cooling load calculation programs are indispensable tools for engineers and technicians who plan and install cooling systems in buildings. Such a program must take various aspects into account in order to be able to perform an accurate cooling load calculation and embed it in the complex system of the building technology.
This includes data on room size, usage, number of people, heat sources, outside temperature and humidity. The properties of the building materials used and the type and number of windows and doors must also be included in the calculation.
Another important factor is the type of cooling system to be used, as well as its performance and efficiency. A good cooling load calculation program should be able to automatically record and evaluate this data in order to perform an accurate calculation.
A precise calculation is not only important for the indoor climate and the comfort of the occupants, but also for energy efficiency and the associated cost savings.
Cooling load calculation programs are essential for effective energy management
Correct calculation of the cooling load is a key indicator for the sustainable planning of building projects. Especially in times of scarce resources and rising average temperatures, precise planning is essential for effective energy management.
With the support of a modern software solution, the calculation process can be significantly accelerated, which can contribute to a noticeable reduction in time and costs. In addition, such a software solution can make all relevant data and calculation results available to all project participants in a transparent and comprehensible manner.
Trimble Nova is a particularly powerful CAD and calculation software that can realistically model and display even highly complex cooling load calculations - from parameter input to the final result. The integrated calculations allow the results to be processed and integrated in real time.
The implemented connection to Trimble Connect is essential for a shared data environment and also ensures that the calculated key figures are available to all relevant project participants - without any loss of time or efficiency.
With this software basis, even complex calculations can be implemented precisely and provide planners with an effective cooling load calculation program that ensures a permanently comfortable indoor climate.
