Category: Low Energy

This is a key topic at the moment due to climate change and the potential increases in temperature in the future. Overheating is a common occurrence in most new and existing buildings and is highly dependent on the actions of the occupants i.e. to open windows or deploy shading methods.

Passivhaus looks to minimise the risk of overheating by including a criteria that requires that internal temperatures do not exceed 25 degrees for more than 10% of the year. This is where the energy balance of heat losses and gains are critical. Overheating occurs when the gains are higher than the losses. Heat gains are caused by solar gains and internal gains from occupants and appliances. The best strategies for preventing heat build up are shading, opening windows, optimised glazing, good hot water system design and energy efficient appliances. If all else fails then active cooling has to be introduced.

Even Passivhauses overheat! This can be due to unusually hot or sunny weather, overheating in a specific room i.e. due to a high proportion of glazing to floor area, a higher occupancy than anticipated, more internal equipment or appliances, failed shading devices allowing increased solar gains, or occupancy behaviour such as not opening the windows

There are a few design strategies that can be employed to reduce the risk of overheating:

1. Reduce solar gains through correct orientation and proportion of glazing.
2. Reduce internal gains through efficient appliances and hot water system design i.e. small pipe run lengths and temperature of storage and distribution.
3. Maximise cooling potential through window ventilation and mechanical ventilation.

Unfortunately though there are still limitations and constraints with these strategies such as windows not being opened due to external noise, pollution, security, safety, accessibility or whether there is anybody home to open them. Or shading not being used as it blocks out the view, hard to use or whether there is anybody at home to deploy them. Passivhaus uses stress tests as part of the design to try to minimise these risks.

In summary, overheating is likely to become more of an issue as the climate temperatures rise and the best way to reduce the risk is to minimise the solar and internal gains through good design.

You may not know that Thinking Buildings are members of the Passivhaus Trust.

The Passivhaus Trust (PHT) is an independent industry leading organisation that promotes the adoption of Passivhaus in the UK. The PHT is part of the global Passivhaus movement and the UK affiliate of the International Passive House Association (iPHA).

But what is Passivhaus and why should I be interested?

Buildings are accountable for 35% of the total global energy consumption. Passivhaus is a tried & tested solution that gives a range of proven approaches to provide net-zero-ready new and existing buildings which are designed for occupant health and wellbeing. Passivhaus buildings provide a high level of occupant comfort whilst using very little energy for heating and cooling.

Whether you are looking to strive towards full Passivhaus accreditation or looking to use some of technics to lower your energy bills or carbon footprint we are able to help. Do give us a call to discuss your ideas. We can often help at an early stage if you considering if it is right for your, your building or site.