Energy efficiency

With targets for Co2 emissions becoming more stringent, builders are being asked to build more sustainable and energy efficient buildings. They have done this extremely well, but while that’s great news in the winter, these houses can overheat in summer. 

That’s even more of a problem as our climate becomes increasingly volatile. As I write this, we’ve just come through the hottest February most people can remember with temperatures reaching 20°C in some places. Summer has come early, swallows have been sighted in the South of England and it’s becoming increasingly difficult to second-guess what the weather will do. We’ve seen hot days in the middle of winter, cold days in June, snowstorms followed by heat waves. It all makes viewing The Day After Tomorrow an increasingly uncomfortable experience.

Despite the deniers, climate change is very real indeed and that creates all sorts of problems. As builders focus on energy efficiency, they look at better insulation and improved air tightness. Every hole or gap in a building represents an escape route for heat and energy, so plugging these gaps is one of the most important jobs for designers. 

Unfortunately, when the weather gets warmer, the heat has nowhere to go. Buildings get hotter and hotter and in the height of summer life can become pretty uncomfortable for occupants.

Generally speaking humans feel most comfortable when temperatures are around 21°C. However, if they get warmer, life can feel distinctly sweaty. In extreme cases, such as when temperatures hit 25-26°C at night, it can even become dangerous.

Recognising the problem

There is a growing recognition about the dangers of overheating and this is forming a key part of the pre-build SAP tests, but there are ways around it. For example, if a test identifies a significant overheating risk, builders may be able to get around this relatively easily by simply stating that the building will have its windows open 100% of the time.

That’s simple to say in theory, but less so in practice. The truth is: many buildings will not be able to provide proper ventilation all day every day. If you live on a ground floor flat, for example, you’re hardly going to be keen to leave the window open all night. There is, then, a difference between the pre-build and as-built tests, but this is not something the builders will need to worry about. They’ve got it through their tests – it will be the occupants who suffer.

Addressing overheating

Overheating can be caused by a number of issues.

• Poor ventilation: A common mistake is to focus on insulation to the exclusion of ventilation. An air-tight building may be poorly ventilated. For example – let’s say you have a home with large south and west-facing glazing. It is well insulated and the target air tightness is low so there isn’t much leakage throughout the home. In sunny warm days there is a lot of heat being generated with nowhere to go. If only some of the windows can be opened, or if there is no cross-ventilation to deliver a stream of cooling air, internal temperatures will become a serious problem.
• Heat islands: This is a particular problem in urban areas such as London which are generally one or two degrees warmer than the rest of the country. This creates heat islands which will see temperatures spike in comparison to the surrounding area.
• Communal heating: Blocks of flats may be covered by communal heating systems. This may mean there is a lot of hot pipework moving throughout the building which is poorly insulated and has a high risk of heat loss.
• Over insulation: So much attention focuses on keeping heat in that not enough is given to letting it out.

How should builders mitigate against overheating?

The solution starts with the design team and they are becoming savvier and more imaginative when it comes to combating overheating risks. You should employ someone who can identify areas where the potential for overheating is high and take steps to ensure that overheating doesn’t happen. This means that when you’re building the project everything is done in the right way. Rather than pushing a button to avoid failing the pre-built SAP test, you have found a way to meet energy efficiency requirements while also ensuring it will avoid overheating when used practically.

Putting it into practice

There are many ways this can be done. For example, we recently worked on a large site in East London which exhibited many heightened risk factors for overheating. It had hundreds of battered units which had been identified as having an overheating risk. They were west-facing with south facing windows and had poor ventilation with no flow of air. It used communal heating, was highly energy efficient and was located within London which, as we’ve mentioned elsewhere, brings with it all the associated problems of heat islands.

To solve this problem, we introduced mechanical ventilation and some heat recovery solutions to bring down the temperature at peak times and mitigate the overheating risk.

Over-heating is a growing problem, and climate change is making it worse. As our weather becomes harder to predict, it will become more difficult to regulate the temperatures inside the house. Government demands for energy efficiency will continue to increase which will in turn lead to buildings which retain more and more of their heat.

The good news is that, if you take action early, there are solutions which will mitigate these problems. Whether by addressing issues in the design phase to ensure cross ventilation or introducing more mechanical ventilation, designers can ensure the people who live in their buildings will not find them becoming unliveable during summer.

Energy efficiency

With targets for Co2 emissions becoming more stringent, builders are being asked to build more sustainable and energy efficient buildings. They have done this extremely well, but while that’s great news in the winter, these houses can overheat in summer. 

That’s even more of a problem as our climate becomes increasingly volatile. As I write this, we’ve just come through the hottest February most people can remember with temperatures reaching 20°C in some places. Summer has come early, swallows have been sighted in the South of England and it’s becoming increasingly difficult to second-guess what the weather will do. We’ve seen hot days in the middle of winter, cold days in June, snowstorms followed by heat waves. It all makes viewing The Day After Tomorrow an increasingly uncomfortable experience.

Despite the deniers, climate change is very real indeed and that creates all sorts of problems. As builders focus on energy efficiency, they look at better insulation and improved air tightness. Every hole or gap in a building represents an escape route for heat and energy, so plugging these gaps is one of the most important jobs for designers. 

Unfortunately, when the weather gets warmer, the heat has nowhere to go. Buildings get hotter and hotter and in the height of summer life can become pretty uncomfortable for occupants.

Generally speaking humans feel most comfortable when temperatures are around 21°C. However, if they get warmer, life can feel distinctly sweaty. In extreme cases, such as when temperatures hit 25-26°C at night, it can even become dangerous.

Recognising the problem

There is a growing recognition about the dangers of overheating and this is forming a key part of the pre-build SAP tests, but there are ways around it. For example, if a test identifies a significant overheating risk, builders may be able to get around this relatively easily by simply stating that the building will have its windows open 100% of the time.

That’s simple to say in theory, but less so in practice. The truth is: many buildings will not be able to provide proper ventilation all day every day. If you live on a ground floor flat, for example, you’re hardly going to be keen to leave the window open all night. There is, then, a difference between the pre-build and as-built tests, but this is not something the builders will need to worry about. They’ve got it through their tests – it will be the occupants who suffer.

Addressing overheating

Overheating can be caused by a number of issues.

• Poor ventilation: A common mistake is to focus on insulation to the exclusion of ventilation. An air-tight building may be poorly ventilated. For example – let’s say you have a home with large south and west-facing glazing. It is well insulated and the target air tightness is low so there isn’t much leakage throughout the home. In sunny warm days there is a lot of heat being generated with nowhere to go. If only some of the windows can be opened, or if there is no cross-ventilation to deliver a stream of cooling air, internal temperatures will become a serious problem.
• Heat islands: This is a particular problem in urban areas such as London which are generally one or two degrees warmer than the rest of the country. This creates heat islands which will see temperatures spike in comparison to the surrounding area.
• Communal heating: Blocks of flats may be covered by communal heating systems. This may mean there is a lot of hot pipework moving throughout the building which is poorly insulated and has a high risk of heat loss.
• Over insulation: So much attention focuses on keeping heat in that not enough is given to letting it out.

How should builders mitigate against overheating?

The solution starts with the design team and they are becoming savvier and more imaginative when it comes to combating overheating risks. You should employ someone who can identify areas where the potential for overheating is high and take steps to ensure that overheating doesn’t happen. This means that when you’re building the project everything is done in the right way. Rather than pushing a button to avoid failing the pre-built SAP test, you have found a way to meet energy efficiency requirements while also ensuring it will avoid overheating when used practically.

Putting it into practice

There are many ways this can be done. For example, we recently worked on a large site in East London which exhibited many heightened risk factors for overheating. It had hundreds of battered units which had been identified as having an overheating risk. They were west-facing with south facing windows and had poor ventilation with no flow of air. It used communal heating, was highly energy efficient and was located within London which, as we’ve mentioned elsewhere, brings with it all the associated problems of heat islands.

To solve this problem, we introduced mechanical ventilation and some heat recovery solutions to bring down the temperature at peak times and mitigate the overheating risk.

Over-heating is a growing problem, and climate change is making it worse. As our weather becomes harder to predict, it will become more difficult to regulate the temperatures inside the house. Government demands for energy efficiency will continue to increase which will in turn lead to buildings which retain more and more of their heat.

The good news is that, if you take action early, there are solutions which will mitigate these problems. Whether by addressing issues in the design phase to ensure cross ventilation or introducing more mechanical ventilation, designers can ensure the people who live in their buildings will not find them becoming unliveable during summer.