Change in TOjuli Rules: Risk of Overheating

The TOjuli requirement, introduced in 2021, aims to limit overheating in (new-build) homes. Passive measures such as sunshades and overhangs are the best solutions. Although solar control glazing can also help, it also blocks the sun's heat on cold days, which can lead to a loss of passive heat gain. Active cooling can consume additional energy and is not always effective if the right conditions are not met.

New conditions for active cooling (NTA 8800:2024)

The update of NTA 8800, effective from July 1, 2024, states that active cooling alone is not enough to meet the TOjuli requirement. Additional conditions must be fulfilled to ensure that the cooling capacity is sufficient. Three methods are provided:

1.  **Limiting Solar Gains**: At least 95% of the glass surface must block solar radiation through sunshades, solar control glass, or the shadow of overhangs/balconies. Homes with little glass surface are also exempt from additional cooling capacity requirements.
2.  **Dynamic Cooling Load Calculation**: The generation and delivery capacity of the cooling system are calculated according to parameters from the Environmental Regulation Annex XVI. The intended cooling capacity must be entered in this calculation to assess whether overheating is adequately prevented.
3.  **Simplified Calculation (Annex AA NTA 8800)**: This method determines the required delivery capacity per living space (e.g., floor cooling) and the minimum cooling capacity of the cooling generator (e.g., heat pump).

Conclusion

From July 1, 2024, the conditions for active cooling will be tightened to better align with the required cooling capacity, effectively reducing the risk of overheating in homes. Avoiding excessive solar radiation remains the simplest and most effective method.