Standards - Design Comparison

The number and scope of standards is constantly growing. It is almost a science in itself for a planner to know all the standards well and to be aware of which ones may and must be applied for which purpose. In addition, the planner must ensure that they are always up to date with any changes. Unfortunately, in practice, compliance is often limited to simply collecting and documenting the individual proofs.

Understanding cause and effect as well as interdependencies, and recognizing that a smaller, economically sustainable sizing is in fact sufficient, is not made possible. Worse still, the standardized procedures can hardly be checked for plausibility anymore.

In particular, the sizing of heat pumps is often based on an excessively large, oversized heating load of the building. As a result, the units are frequently so large that they quickly leave the modulation range and then begin to cycle. This increases wear and tear, reduces efficiency, and raises the CO₂ emission intensity. An illustrative analogy is a matchstick, which produces higher emissions when being lit and when being blown out. The more often these phases occur, the worse it is for any generation component.

Germany

Germany has its own regulations and requirements for calculation methods used to size components. The fundamentals of physics and mathematics are, of course, identical worldwide.

However, the standards and guideline committees define their respective requirements in isolation from one another, depending on whether a peak value for a particular season or an energy demand is to be determined. In addition, the calculation methods for heating, cooling, and energy differ from each other.

The heating load according to DIN EN 12831 [DIN 12831, 2025] is calculated for an unspecified point in winter solely from the losses due to transmission through constructions and ventilation to the outside air, resulting in a simultaneous maximum heating load for rooms and for the entire building. The planner, however, receives no information about heating energy or part-load operation with its hourly frequency distribution at other times during winter.

The cooling load according to VDI 2078 [VDI 2078, 2015] is determined from an extreme summer daily profile, which is repeated three times in succession, resulting in the cumulative maximum cooling load for rooms and for the entire building. However, the planner receives no information about cooling energy or part-load operation with its hourly frequency distribution at other times during summer.

The annual energy demand according to DIN 18599 [DIN 18599, 2025] attempts to calculate monthly results for heating and cooling energy by using daily sums of usage and monthly climate data, together with estimated monthly utilization factors of internal heat gains from occupants, equipment, and lighting, as well as solar heat gains through the windows, both for usage zones and for the entire building. However, the planner receives no information about part-load operation with its hourly frequency distribution at other times of the year.

The summer comfort according to DIN 4108 Part 2 [DIN 4108 Part 2, 2023] evaluates selected rooms without active cooling to determine whether they overheat excessively in summer. In addition to an characteristic value method, an hourly annual simulation is also recommended to determine and assess the overheating degree-hours.

The results are each determined in isolation and are not comparable with one another, since they are based on different boundary conditions and calculation methods.

The Building Design Days + Energy method creates a unified foundation based on physics and the mathematical formulas already used in existing standards. The differences for specific objectives are determined solely by the boundary conditions. Through design factors, it is specified which shares and magnitudes are to be applied for sizing, in combination with the Climate Design Days for the various regions.

For example, it makes no sense to simplify by omitting real existing influences in winter if these must be included in the input for summer and therefore have to be entered anyway.

• The BDD+E method addresses the omission of existing influences in a standard verification by means of design factors. These factors can, for example in the case of heating load, set the share of internal heat gains from occupants, equipment, and lighting to 0%.
• However, in the future the standard could also specify a fixed share of, say, 35%. Alternatively, the planner could test a different percentage and transparently agree on it with the client.

Europe

Each country has its own regulations and requirements for calculation methods to size components. The fundamentals of physics and mathematics are, of course, identical worldwide.

European standards are developed jointly and then translated by each country into a national version. The aim is to achieve consistency in content and application.

The only differences lie in the boundary conditions — mainly the outdoor climate, the varying consideration of contributions that either reduce or increase the target value, the typical construction methods of buildings, the use of spaces, and the energy sources used for electricity generation. For sizing, extreme peak values are often taken retrospectively from the outdoor climate for safety reasons. However, climate change forces us to look ahead into the future, since buildings will be used and operated in the years to come.

The Building Design Days + Energy method creates a unified foundation based on physics and the mathematical formulas already used in existing standards.

Each country then only needs to define the differences in boundary conditions for specific objectives. In the BDD+E method, the Climate Design Days are generated for the various regions, and through the design factors it is specified which shares and magnitudes are to be applied for sizing.

The advantages for planners are that simply by changing the boundary conditions, they can carry out an assessment in accordance with the applicable standards of any European country. In addition, they can also apply their own design factors in order to communicate a potentially more sustainable solution by comparison.

Since the calculations for heating and cooling with respect to capacity, frequencies, and energy are based on the same mathematical foundation, it is sufficient for a comparison to evaluate and document only the differences in boundary conditions. The transparent representation makes it possible to recognize cause (input) and effect (result), providing a sound basis for decisions on sizing.

Worldwide

Each country has its own regulations and requirements for calculation methods used to size components. The fundamentals of physics and mathematics are, of course, identical worldwide.

The Building Design Days + Energy method can be applied globally (see also Europe).