Blog: The Hot Topic – Why are we overheating?

Global climate change is causing more extreme weather patterns, which not only leads to discomfort but also increases energy consumption. This exacerbates climate change even further and creates a cycle of demand the Earth cannot fulfil. Overheating assessments are now required to meet Building Regulation Part O, and we now offer this service at Bowman Riley. This assessment is best undertaken at the planning stage or otherwise; the earlier, the better to avoid serious issues.

Why Do We Need to Assess Overheating?

Climate change will be an increasingly significant driver for change, with heatwaves becoming a regular occurrence in around 20 years. The Summer of 2018, with its record-breaking hot temperatures, currently has a 10% chance of reoccurring. By 2050, this will increase to 50%.

The Heat Island effect not only increases daytime temperatures but also prevents nighttime purge cooling. A growing elderly population, more vulnerable to the effects of overheating, and the rise in ozone, nitrogen dioxide, and volatile organic compounds (VOCs), which increase mortality rates, further underscore the need for proactive measures. Additionally, refrigerant leaks from cooling equipment, such as air conditioners, will contribute to 20% of ozone depletion.

Building Contributions to Overheating

Building Regulation compliance previously focused on reducing heating demand through increased insulation and air tightness, inadvertently increasing cooling needs. Inappropriate designs, such as excessive glazing, insufficient shading, low thermal mass, and inadequate ventilation, further contribute to overheating. Unrealistic expectations for space usage, like overlooking security or safety concerns when considering ventilation, and optimistic assumptions for natural ventilation, exacerbate the issue. Heat gains from risers in multi-storey units and changes in space use also play a role.

Why Have Part O as Opposed to the Previous Strategy?

The previous strategy was inadequate for continued use as it was out of step with international standards, allowing builders to find ways around it due to its rigidity, using a simple 28°C backstop. The new Document O now considers noise, security, protection from falling, and pollution. New modifications include graduated window openings from 22°C to 26°C, assumptions about window closure below 22°C, and night-time ventilation standards for bedrooms.

Adaptive Comfort

The adaptive comfort concept defines how we perceive comfort depending on the outdoor climate. For instance, in Winter, we wear thicker clothing and accept lower indoor temperatures than in Summer. Based on academic research, this method varies with individual preferences and building use, classifying buildings into three categories of sensitivity: CAT 1 (high sensitivity, e.g., hospitals), CAT 2 (moderate sensitivity, e.g., residential houses), and CAT 3 (low sensitivity, e.g., warehouses).

The Two Routes

There are two routes to pass overheating assessments:

1  Simplified Route

• Uses glazing areas, location, cross ventilation, and minimum free areas.
• Doesn’t allow sampling; all units must be individually tested.
• Has a narrow passing criterion.

2  Dynamic Simulation

• Much more accurate.
• Allows sampling.
• The PASS design route is much wider.

Standards like TM52, TM59, and BB101 guide these assessments, ensuring buildings meet overheating criteria and maintain internal air quality by regulating CO2 levels.

Conclusion

As we face increasingly extreme weather patterns, ensuring our homes and buildings are equipped to handle overheating is crucial. Overheating assessments, now a regulatory requirement, provide a proactive approach to mitigating the effects of climate change. At Bowman Riley, we are committed to supporting sustainable building practices through comprehensive overheating and internal air quality assessments. By addressing these issues early in the planning stage, we can create comfortable, energy-efficient spaces that contribute to a healthier planet.