Planet friendly architecture, guidance and inspiration​
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Taking the fuss out of architecture and building projects

Top tips on how to make your building cooler + comfortable 😎

We’re now into the heart of the summer holiday season - that time of year when historically a lot of people have chased warmer weather abroad. With temperatures here in the UK climbing, it feels like a relevant time to talk about overheating. Not the kind we expect on holiday, but the uncomfortable kind we deal with while working, living, and simply going about our regular day to day lives, trying to stay comfortable in our own homes. Overheating is sometimes called ‘solar gain’ as it is extra heat gained from the sun.

When I was growing up in Bournemouth, on the south coast, during the 1970’s and 1980’s the summers were fairly warm and long. From memory we had warm weather from mid-May until early September. Having lived in Sheffield for 25 years now, which is about 250 miles north of Sheffield, I have observed the cooler north is no longer as cool as it once was. However, it is a cooler place to live in my opinion, but that’s probably a different definition of the word ‘cool’ in the context of overheating. The summers in Sheffield are now longer and hotter than the summers I experienced in my youth in what is a warmer part of the country. I understand that the UK is classified as a cool temperate climate but I’m not so sure if that is the case any longer. The climate has definitely changed in my lifetime.

In the UK overheating is often associated with large areas of glass and south facing facades, often seen on modern buildings, both houses and commercial properties. Think of how hot a conservatory or orangery gets in the summer. The glass amplifies the effects of the sun. Highly glazed buildings have become widespread in the last 100 years or so, mainly driven by some of the architectural fashions of the 20th century [such as modernism], and improvements in glass technology and cooling systems that offset the effect of the overheating. Read on to discover my thoughts on these + loads more.

I also believe that summer times in the UK are getting hotter and more frequent due to human-caused climate change. Our ancestors + the current generations are to blame. Our lifestyles have most probably had a negative effect on the environment, globally, indirectly and directly, and probably, a lot of the time, without realising. That’s right, you and I, right now, we are also part of the problem. This isn’t intended to be a Newsletter full of criticism but rather provide some solutions to these problems we are experiencing.

These human interventions, that probably started with the industrial revolution in about c1750, have resulted in the atmosphere warming up and baseline average temperatures rising. Recent years have seen extreme heat records broken, and days exceeding 30°C have more than trebled compared to historical averages. As I write this, in August 2026, the UK is on track to beat all previous records, for the hottest summer ever. The heat can also feel more intense in the UK, due to factors like relatively highly insulated homes trapping the heat, the materials that buildings are made from, high humidity and urban locations.

Over the last 40-50 years UK buildings have been progressively designed and constructed to retain heat for the colder winter months [although most of them are not as energy efficient as they should be, in my opinion]. If the buildings are well insulated, draft stripped and double glazed, this can sometimes mean the warmer indoor environment is harder to cool down as the heat is retained for longer.

Dense building materials, such as masonry and concrete, also absorb the heat and release it later in the day [have a high thermal mass] which also mean buildings stay warmer throughout the night time and mean it can be harder to cool down quickly. This is in contrast to lightweight building materials, such as a timber framed construction, which heats up and cools down quicker [low thermal mass].

The UK often experiences ‘maritime’ heatwaves with higher relative humidity. This means that our natural in-built water-cooling mechanism [aka sweating] doesn’t work as well as it could do. Sweat doesn’t evaporate as effectively [which extracts heat and cools us down] making the temperature feel much higher and stickier.

Built up, urban environments, where there are thousands of people living, such as towns and cities, absorb heat during the day and slowly release it + local transport networks [more vehicles etc.]. release heat. This called the ‘urban heat island’ effect. London is meant to be the worst area in the UK for suffering from the urban heat island effect, Manchester and other large cities are not far behind. The urban heat island effect can cause local temperatures to feel between 5-10°C hotter than other rural or coastal areas, that are less built up.

Hopefully it’s fairly obvious that too much sustained heat is bad for human health, and other creatures. This is starting to move out of my area of expertise, but I understand that overheating is dangerous to our health because it forces your organs to work beyond their limits to regulate core temperature. When natural cooling mechanisms, such as sweating and widening blood vessels fail, your body can experience life-threatening conditions like severe dehydration, organ damage, and heatstroke. Overheating also affects our wellbeing and productivity, as it impacts the quality of our sleep and can also affect cognitive performance and mental alertness. I could probably write more about the dangers of overheating, but I suspect there are lots of other resources available that you can easily access, that talk about the medical harm resulting from overheating in much more detail.

Well now, read on my cool friend to find out more about what methods are available to you. I’ll be sharing some top tips that can help you reduce overheating in your current home or place of work. Some of these methods are better suited to new building design, and some can be used for both new building design and retrofit upgrades to existing buildings. I will also share my thoughts on where I think the future of building design might be heading in the UK, to reduce overheating.

Guidance on how to reduce overheating in your building

Is there anything I can do to make my home or place of work cooler or less affected by overheating?

You will be glad to hear, yes, there absolutely is. Read on my hot friend to find out more, so we can continue to be the coolest of friends.

Some of these ideas are more practical and easier to implement than some of the others. Perhaps some of this information can be applied to your house or workplace and put in place before the next heatwave or by spring next year. I really hope so.

Generally speaking, there are two types of cooling. Passive + Active. Passive means it is built into the fabric of the building and does not need any further power or energy to generate cooling. Active means there is an engine behind the cooling system and the engine needs energy to be powered, usually by electricity, so these systems are not energy efficient. Ideally only use passive systems so you don’t use up more energy and thus make this climate change problem any worse. If using solar PV panels to power the active cooling system this is better, if possible.

Here are a few cooling options to consider:

1. Passive night time ventilation cooling. Essentially, you need to open up windows and doors during the cooler night time so the hot air can be flushed through and replaced with cooler air. Ideally opposite each other so good cross flow ventilation happens. Security and acoustics are the main issues that need to be considered with night time cooling, so this method is not always possible. Opening the windows in the upstairs rooms and opening loft hatches [where the ceiling is insulated] is also really effective as it creates a pressure change, the hot air is sucked up into your loft space and replaced with cooler air that enters from the windows. If you have loft rooms / a loft conversion it obviously won’t work. Also, only open windows and loft hatches during the evening and night time, not the daytime as you are just letting in hot air. Small gaps during daytime perhaps, to encourage a breeze. Security, acoustics and pollution may also need consideration here as well, at the design stage, not after the building is constructed.

2. Passive shading devices - horizontal. Such as large overhanging roof edges, protruding or recessed balconies above ground floors, overhanging features, covered external corridors, open on one side, that creates shading and ventilation to the rooms behind [such as an open, shopping arcade corridor below offices above], brise soleil [or horizontal slats], awnings, shade sails, and slatted structures like a pergola. We have a shade sail above our south facing sitting room windows / French doors and, while not perfect, it does work, the internal temperature is a lot cooler when it’s used.

3. Passive shading devices - vertical. Such as external sliding shutters, external blinds and internal blinds. External shutters and blinds are some of the best systems out there that make a massive difference, as they reduce the heat entering your rooms before the sun hits the glass. Surrounding features such as trees and buildings can also help create shadow and can assist with a passive cooling strategy.

4. Passive shading devices - window + door recesses [reveals]. Smaller shades [that still help a bit] can also be created by moving new [or replacement] window or door frames further into the wall, so a shadow is created and less sunlight is let in. Can be useful for thicker walled properties. Creating feature frames, or protruding boxes, which stick out from the face of the wall and surround windows and doors is another neat trick that can be used to create extra shading to doors and windows,

5. Passive materials - less glass. Reduce the amount of glazing on east + south + west facing walls, modern glazed facades create greenhouse type sweaty spaces. Not so easy for existing properties [not impossible though] but easier to implement on new build projects. Ideally try to limit the glazing ratio to 11% - 18% of the total floor area, preferably below 12%. Also avoid full-height glazing as it is harder to shade, loses more heat in the winter and doesn’t provide much more daylight below about 800mm height. See also the other section below that mentions PHPP.

6. Passive materials - solar control glass. This is glass which has a special coating that reflects the heat back again, but this can be relatively expensive, and often has a slight tint or colour to the glass. Glass has a property called the ‘g-value’ [or solar factor], this measures how much solar heat passes through a window or glazing system and enters a building. Expressed as a number from 0 to 1 [or 0% to 100%], it represents the sum of direct solar transmission and heat absorbed by the glass. A high g-value [for example 0.70] lets 70% of solar radiation through, therefore good for cold climates. A low g-value [for example 0.30] lets 30% of solar radiation through, therefore good for warmer climates or east + south + west facing windows to reduce overheating.

7. Passive materials - bio-based insulation. Certain natural insulation materials also have a heat absorbing property, such as wood fibre and cork insulation. The insulation can absorb a certain amount of heat and then discharge it slowly over time without causing discomfort. I love natural organic insulation as it’s err natural and helps us more than say insulation made from petrochemicals like Kingspan and Celotex, in my opinion.

8. Passive materials – light coloured exteriors. Using white or light colours for the exteriors of buildings can help reflect heat and light, whereas dark colours will absorb heat and light. Big culprits of these in the UK are roofs or cladding, that are often dark coloured. I know that flat roof membrane manufacturers sell white or light grey versions that are intended to reflect heat and light. Light coloured renders, bricks, stone and cladding can help with this sort of thing. I sometimes find that light coloured rendered buildings in the UK can sometimes look a bit bland and don’t always stay light coloured for long, especially after 1-2 UK winters. Using light coloured materials in the UK can be designed to look more interesting though with a bit of forethought.

9. Active - air conditioning. Active cooling devices include systems such as ducted air conditioning, non-ducted single room comfort cooling, and even evaporative cooling and iced air cooling, in conjunction with fans. However, on new build properties active cooling systems will affect the overall energy efficiency performance as more energy will be required to power the active cooling systems during the summertime. Changes to other parts of the design elsewhere might be needed to ensure the new building meets the energy efficiency requirements of the Building Regulations.

10. Active - integrated heating + cooling systems. You can also combine active cooling systems into heating systems, such as underfloor heating and heat pumps, or chilled water coils. The heating system is reversed, instead of running hot water through the system, cold water is run through the system. However, this needs to be carefully and properly designed and installed, by an experienced engineer, to avoid unintended consequences and damage to the heating system. Additional pieces of equipment are sometimes needed.

11. Active - single cooling heat pumps. Alternatively, a separate heat pump could be introduced, that is used for cooling only.

Further reading for new building designs – overheating specific design guides

I’ve also included a few other resources / specific overheating reduction design methodologies below so you can investigate more fully in your own time.

• Building Regulations Approved Document, Part O – Overheating Mitigation. This relatively new part of The Building Regulations came into effect in 2022 and now requires all new homes to ideally manage overheating risk with a passive approach. Option to adopt a ‘Simple method’ or ‘Dynamic method’. The Simple method adopts some of the techniques described above but is quite rigid. The Dynamic method involves computer modelling with specialist software and is the most flexible method to use. Only suitable for houses and not other building types yet, but I expect it will be updated to apply to all building types soon.
• CIBSE TM29: 2026 - Overheating risk in dwellings: a design stage methodology. CIBSE = The Chartered Institution of Building Services Engineer. TM = Technical Memorandum. Specialist design guide that must be used in conjunction with specialist heat simulation and modelling software. Needs to be completed by a qualified Building Services Engineer, familiar with suitable software. Very flexible. Also only suitable for dwellings and not other building types yet, but I expect it will be updated to apply to all building types in the near future.
• PHPP, latest version. PHPP = The Passive House Planning Package. This is a comprehensive, Excel-based energy modelling tool developed by the Passive House Institute in Germany. It is widely used to design ultra-low energy reliant buildings and also has a good section dealing with excessive glazing and overheating. I understand the PHPP overheating tool is not yet recognised under The Building Regulations but it can be a useful tool to demonstrate compliance or that suitable techniques are adopted or avoided at an early stage, and then taken through to final design with certified overheating methodologies and completion on site.

Perhaps lifestyle changes could also include going for a two hour lunch that includes an afternoon power nap or don’t complete cognitive heavy work tasks at the hottest time of the day. Personally, I am up for an afternoon nap kind of lifestyle but not sure if that will be happening in the UK anytime soon?

Building forms + features will have to change to adapt to the solar gain challenges we are experiencing. Hopefully, good building designers will get creative and think about how to design and make a cooler building from the very start of a project. Initially, I think this will be harder for Clients and designers to adopt as will involve a mindset and process change to how things have been done in the past.

I think we will see less glazing, less fully glazed facades, and more permanently fixed shading devices. Combinations of the following passive methods are likely to be adopted and incorporated into building designs more regularly:

• Large overhanging roof edges / features.
• Protruding or recessed balconies above ground floors.
• Covered external corridors, open on one side, that creates shading and ventilation to the rooms behind.
• Protruding horizontal slats above windows and doors.
• External sliding shutters.
• External blinds.
• Light coloured exteriors.

This means that some of our buildings may start to reflect how buildings in hot countries have already looked for several centuries.

Integrated heating + cooling systems are also likely to be adopted more widely for new build properties, such as heat pumps that have cooling capabilities as well as heating for the winter.

However, sadly, I think it is more likely that a lot of people will move towards the path of least resistance. This probably means that active methods will be increasingly used, such as air conditioning or comfort cooling, especially in existing buildings, which are unlikely to be policed or managed by statutory legislation, such as The Building Regulations. In theory, using active methods of cooling could be ok if they are powered by renewable energy systems, such as solar PV. If not, this is likely to put more demand on the national grid and will use up more energy and thus emit more CO2 which is not energy efficient and is not good news for the environment. The embodied carbon and embodied energy of the renewables and air conditioning plant also needs to be considered.

The external aesthetics of external air con units also needs to be thought through. In my opinion, large rectangular fan units popping up around buildings is not going to look very attractive, unless they are sited thoughtfully and / or masked with suitable screening. Acoustics and impact on the neighbours should also be investigated to ensure they are not a nuisance. It’s worth noting that Planning Permission is often required for external pieces of equipment such as ASHP’s or similar apparatus. If in doubt, check before getting prices and installing.

When studying at university in the 1990’s I always thought active cooling methods weren’t going to be needed in the UK. The last few years of extreme temperatures seem to suggest otherwise; unless building designs change significantly, as described above. From many years’ experience and observation, the construction industry seems to move very slowly so I’m not expecting building designs to change significantly any time soon, unless forward thinking building designers are used.

Each location, orientation of each facade and each project are different and may require a different approach or specific details.

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Get in touch and I can show you how best to optimise your building, so it is cooler during the hot summer times.

A famous low energy project that was not successful

This isn’t actually a success story but rather a bit of a project failure. It’s intended to be a sobering reminder of unintended consequences. This actually created a building that was meant to be a progressive eco build but ended up using a lot more energy than was expected.

The project we are looking at is Woodhouse Health Centre which is one of Sheffield’s largest doctors surgeries. The existing building was relatively famous when first constructed in c1989 as it was a pioneering, super energy efficient building, originally designed by sustainable building pioneers Robert and Brenda Vale. Woodhouse Health Centre, featured highly sustainable construction techniques, still used in current building designs today. It was widely recognised in the construction industry at the time as ground breaking and won a few awards. I even studied this building as part of my architectural technology degree course back in the 1990’s.

A few years ago, [to my delight] I was actually appointed to work on this building to create an extension and extensive remodelling to various parts of the building, to better serve the current needs of modern GP practices. This isn’t about highlighting my work but rather what I discovered when completing my initial investigations and information gathering before starting design work. This involved extensive interviews with the members of staff and management.

The original existing building design featured passive energy design such as lots of natural light to reduce reliance on electrical lighting, extremely high levels of insulation [super insulated], high thermal mass materials, relatively low embodied energy and embodied carbon, high levels of air tightness and MVHR [Mechanical Ventilation with Heat Recovery] throughout. The building still exceeds the minimum levels of the Building Regulations today and requires very little energy to heat the building during winter time. Arguably, this building was a precursor to the industry best practice, ultra-low energy reliant, building design code of Passivhaus.

However, the original design intent, while admirable, backfired as the building design did not consider how to deal with overheating in a practical way. I understand overheating was considered in basic form and high level roof windows were intended to be opened at night time to provide passive ventilation cooling. Unfortunately, the night time ventilation cooling strategy was not implemented. Primarily because the end users were not properly briefed by the designers or building contractors about how to operate and manage the night time cooling. Security was also an issue and leaving roof windows open could have meant intruders could easily access the surgery.

Retro-fitted air conditioned, comfort cooling systems were installed to a lot of the rooms to create a more comfortable environment for end users.

The MVHR systems were also not understood or explained to building end users, this led to the decommissioning of the MVHR systems and natural ventilation systems used instead, which were not as energy efficient.

Essentially, the building aspirations and intended performance failed.

This meant the building consumes more energy to provide a comfortable and healthy environment, and also emits more carbon dioxide into the atmosphere.

This raises important questions about current and future buildings, overheating and occupant comfort. Is overheating being addressed adequately at all design and construction stages for all building types? Not just residential new builds, as Part O of the Building Regulations. Are building designers ensuring that the building users are briefed on how to operate their building to create the optimised and comfortable environment that is expected? Is enough Post Occupancy Evaluation completed and acted on [remedial works completed] when the results are not as positive as they could be?

I would also like to add this project was a project success from my perspective. The Client’s goals and aims were successfully achieved, on budget and on time. The extra facilities needed exceeded expectations. It’s probably worth noting this project was also a shortlisted finalist at the AT Awards for excellence in Architectural Technology 2021.​

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Want some advice and guidance on how to reduce overheating in your house or place of work? If so, please get in touch so we can…

Has this Newsletter helped you? If so, I’d genuinely love to know what you found helpful. Even better, if you’ve implemented something in real life and it is making a positive difference. Just reply to this email and let me know.

New places

If you are new to my newsletter then each month, I share a photo of somewhere I've been. Just sharing something about my love of buildings and nature. I also love travelling to new places and cultures. Whenever I go on holiday, I try to take a few photos of buildings and places I find fascinating and interesting. I’m by no means a professional photographer but I’d like to share some of these places with you, hopefully they capture something of what I experienced.

Last month’s photo was of the Ben Youssef Madrasa in Marrakesh, Morocco. Taken in 2010, during my honeymoon.

My photo shows the central courtyard and reflective pool. Completed around 1565, the Ben Youssef Madrasa was the largest Islamic college in the Maghreb at its height. Today it is a historical monument and is renowned as a masterpiece of Saadian and Moroccan architecture. The building features well preserved intricate Zellige tilework, carved cedar wood, and detailed stucco ornamentation. Really gorgeous patterns and details throughout.

The Ben Youssef Madrasa features a wealth of passive cooling methods. The courtyard contains covered external corridors, open on one side that creates shading to the rooms facing the courtyard. There are not many external openings, windows and doors are kept minimal and small. Thick Adobe mud walls provide high thermal mass, with openings strategically placed to provide good cross flow ventilation. Light colours have also been used to reflect light and heat. It could also be argued the central pool also provides some form of water absorption cooling. Despite being hotter and drier than the UK, this building remained remarkably cool and comfortable inside.

As can be seen, some of the techniques described above are nothing new, people who live in hot countries hundreds and thousands of years ago integrated many passive methods to make their buildings more comfortable and healthy. Would love to see if we can complete more projects like this in the UK, that use passive cooling methods yet remain surprisingly cool.

So, what do you think this is a photo of and where was this photo taken? If you think you know where the photo was taken or like the photo and want to find out more, hit reply and let me know. Hint – these are some of the oldest timber gates in Europe.

You’ll have to wait until the next newsletter to find out where this photo is from. I know, I can feel the pent up excitement from here.

What's next

Next time we will have a look at how to reduce some of the risks on a project by conducting early, invisible forensic detective work. Spending a bit more time and relatively small amounts of money up front to get the right surveys and associated information should save more time and money in the long run. Keep an eye out to find out more.

That’s it for now, hope you enjoyed this and I look forward to sharing more with you soon.

By the way, in case you are wondering, you’ve been sent this email because we’ve spoken in the past, perhaps discussing your project, or you have asked me a question via the website, social media or we have met in real life. I do hope you found this email helpful, entertaining and inspiring. However, if this is not the case, please hit unsubscribe at the bottom. I’ll try not to be offended, although I probably will be a little bit! I know, I know, it’s me, not you [it usually is].

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