Shading in the energy performance calculation

For all new construction, both residential and non-residential, permit applications since Jan. 1, 2021, must meet the requirements for Nearly Energy Neutral Buildings (BENG). To determine the energy requirement (BENG 1) of a building, a BENG calculation determines both heat and cold requirements for each month. The results of these 24 calculations are added together to determine the total energy requirement. Monthly average values are used in the calculations.

Due to the assumptions of the BENG calculation, which are described in the NTA8800, it appears that for most homes, the cooling requirement is less than 10% of the total energy requirement. This often does not match calculation based on hourly data. As a result, regulations often underestimate the likelihood of overheating and solutions that reduce cold demand do not feature as well in BENG calculations. However, practice shows that complaints about overheating are increasing. Future climate scenarios also show higher temperatures. Thus, this makes it increasingly important to look closely at the building's cooling requirements in the design and follow the so-called "ladder of cooling." This contains four steps:

1. provide a cooling environment (e.g., with trees or green roof);

2. repel heat (for example, with screens or blinds); 

3. passive cooling (e.g., with night ventilation);

4. environmentally friendly active cooling (e.g., with heat pump).

Applying movable blinds

Applying solar shading reduces solar heat gain. This causes the cold demand of the house to decrease. In the BENG calculation, the same time fractions were calculated until 2024, when the blinds are down, for both the heat and cold demand calculations. This increased the mid-season heat demand because the desired solar heat gain is reduced.

Because most of a building's energy needs are determined by its heat requirements, the effect of shading is not readily apparent in a BENG calculation. Fortunately, the 2024 version of the NTA8800 changes this. With manually operated or intelligently controlled blinds, they will now stay up as soon as the building has a heat requirement. As a result, the blinds are optimally utilized by taking advantage of the free solar heat when it is desired. The heat requirement in the winter and in-between seasons will not go up, however, the cold requirement will always go down.

This is in line with practice, solar shading is a product that adapts very well to the seasons and the heating or cooling needs of its users. In the winter and mid-season, the useful solar heat gain can be utilized,while on hot days the unwanted entry of solar heat into the building can be reduced. Solar shading also prevents direct radiation. This benefits both the thermal and visual comfort of the user.

Precisely because of this adaptive behavior, solar shading is an ideal tool for creating a good and healthy indoor climate. It should be kept in mind that the BENG calculation is not a comfort calculation.

Shading in a building with cooling

When active cooling is used in a building, this system often has insufficient capacity to keep the home at the desired temperature throughout the season. Filling this cold demand by a system with active cooling causes a significant increase in the home's energy consumption. 

When shading is used in a building, active cooling will be omitted for much of the year. After all, what doesn't come in doesn't have to go out, which is also reflected in the "ladder of cooling". In combination with active cooling, solar shading has a positive effect on BENG 2. When additional cooling is required, the required cooling capacity will be significantly reduced. This will save on the energy consumption of the home. This is especially welcome in these times of high energy costs.

Changes NTA8800:2024

From July 2024, calculations will be made with the new version of the NTA8800. It will then be possible to calculate with intelligently controlled blinds. ISO 52016-3 is used for the adjustment of the blinds. This standard describes the switching points for shading that depend on the heat or cold demand, lighting intensity (lux) and indoor temperature. In the 2024 version, blinds operated from outside are also included in the calculation. As a result, sliding panels are now also valued as shading.