RIBA 2030 Climate Challenge target metrics for all buildings

Overheating

With considerably more focus on building temperatures in all seasons becoming excessively high for occupants, it is great to see these as the headline target for health and wellbeing. Paradoxically, as we better insulate buildings, improve air tightness levels in buildings and build with more glass, ventilation design can suffer and temperatures can quickly become unmanageable. To achieve levels of 25-28C for a maximum of 1% of a building's occupancy is a tough target. The current pass threshold for TM52 (the European overheating standard) is <3% and whilst the RIBA target is eminently achievable, it will require detailed and professional thermal modelling to de-risk the design and allow design teams to confidently progress going forward.

Success in designing for overheating is intimately related to ventilation design within the building.

Ventilation (CO2 levels and air quality)

Extensive work undertaken by the Chartered Institute of Building Services Engineers (CIBSE) has proven that CO2 levels within a building is directly proportional to the effective ventilation of the rooms forming said building. 900 ppm (parts per million) is a standard value and not overly strenuous as far as ventilation design is concerned either. Practically, if you design the building to meet current Part F Building Regulations you will meet this criteria.

Due to the nature of air and increasing complexity of building design to design effective ventilation and ensure that overheating is managed, building physics modelling is the ONLY way to ensure the subtleties of the results are fully explored and risks mitigated. We are well beyond guessing and having full confidence that once built the building will be fully optimised.

To reduce the performance gap, system commissioning and post occupancy evaluation (POE) will ensure the building is performing the way it was intended.

Daylighting

Natural daylight into a building in all seasons is critical to boosting levels of mental health and productivity. Building orientation, levels of fenestration and maximising views all can have an effect on the amount of daylight captured, but like other aspects of building design going to extremes can lead to excess heat loss, increased overheating and higher building costs.

The RIBA targets for daylighting (>2% av. daylight factor and 0.4 uniformity), similar to ventilation are not overly strenuous and the CIBSE LG10 best practice guide will allow most designs to pass. If anything, the daylight factor is becoming quite a simplistic method of calculating real light levels but other useful methods such as daylight illuminance and daylight autonomy methods are outputs from most modelling packages now.

As you will be increasingly aware, with an accurate building physics modelling the subtle interplay between daylighting, ventilation and overheating can be navigated more robustly whilst making the most of the site, views and natural energy.

Volatile Organic Compounds (VOCs) and Formaldehyde

This element of occupant health is a new one for many and reflects the focus on trying to further improve indoor air quality, reduce man-made materials and eliminate chemicals that can contribute to adverse respiratory, allergic or our immune system reactions.

Targets for VOC and formaldehyde, 0.3g/m3 and 0.1g/m3 respectively, can be initially assessed by looking at manufacturer’s product data sheets and measured using sensory equipment once construction is completed. Whilst the practical measurement of these emissions in a building is unlikely to be an overnight transformation it can focus the designer’s and client’s mind on more responsible material procurement and purchasing; particularly for paints and finishes used in the building where contact with occupants can be direct.

If you have any questions about the RIBA 2030 Climate Challenge, please don't hesitate to contact the Mesh team today.