August 9, 2022

How to Prevent Overheating in Highly Glazed Home Designs

Written by Rebecca Clayton

luxury home inspiration - preventing overheating in highly glazed home design

With Summer’s in the UK seeming to get warmer every year, and changes being made to the UK building regulations regarding overheating, conversations around how to prevent overheating in highly glazed home designs are becoming more common.  


Whilst many people still believe that in a highly glazed home design, what causes overheating, the glazing is not the issue it's poor design that causes overheating. Solutions such as solar control glass, opening glazing elements and external shading can prevent overheating in highly glazed home designs. 


What is Solar Gain and What is a G Factor? 

Solar gain refers to overheating in internal spaces caused by infrared radiation from the sun travelling through glazing and becoming trapped inside.  

luxury new build home with oversized solar control glazing

This happens as the rays are emitted from the sun as shortwaves and as they enter the home they are absorbed by the materials and then emitted as longer infrared rays, meaning that they are unable to travel back through the glass and then become trapped. 

There are many ways to reduce this, such as utilising modern advances in glazing technologies, incorporating various shading elements and clever architectural design.    

G Factor is essentially the term for the total incident radiation that passes through the glass. It is usually seen written to two decimal places, this is the percentage that passes through. So, 0.67 would mean 67% can enter the home through the glass. 


Approved Document O to Tackle Overheating 

Approved Document O is the relatively new part of building regulations that outline rules to prevent overheating in new build dwellings. 

Within this new set of regulations, are locations set as high risk, low risk, etc. depending on the risk they have been deemed will depend on the regulations and requirements for the build, including the glass specification. 

contemporary new build home with timber overhang for solar shading

If you think this means that new build residential projects can't be designed with large glazing elevations, you are mistaken.

In fact, as shading is included as standard for projects in high risk locations, the glazing limits can sometimes allow for larger glazing elevations than a project in a lower risk location.  

This can either be achieved through the simplified method set out in Section 1, or by using the dynamic thermal modelling method set out in Section 2. 

IQ work from architectural drawings and will design and manufacture the architectural glazing elements to meet the specs stated on these drawings. It is up to the architect on the job to figure out what requirements the glass needs to meet as this can be affected by many other factors on the project which we as glaziers wouldn’t have the information on.  


Does Triple Glazing Prevent Overheating?

Although many people may think that triple glazing would increase the solar gain in internal living spaces, it is in fact the opposite.  

sustainable new build home with triple glazed sliding doors

As triple glazing has a lower G factor than double glazing, this means that triple glazed systems will be better at reducing solar gain during the warmer months. To further prevent overheating in highly glazed home designs.  

Triple glazing has many benefits on top of this, such as better thermal performance for the winter months, better water tightness and air permeability and more.  

With a move toward more sustainable homes, triple glazing is increasing in popularity. Our Invisio structural glazing system can be specified with triple glazing and our minimal windows 4+ triple glazed sliding door system even underwent hurricane testing and surpassed the requirements! 


Solar Control Glazing 

The best way to prevent overheating in highly glazed home designs is to specify the glazing with solar control glass. IQ would always recommend this for glass roofs and large south facing glazing elevations, however, it can be specified on any of our insulated glazing systems.  

This type of technical glazing solution involves applying a thin metal oxide coating to the inner face of the outer pane of glass in a double or triple glazed system. There is a range of solar control coatings available, affording you different levels of light transmission, external tints and solar control. 

highly glazed home design with solar control glazing

Although the coating is usually always applied to the inner side of the external pane, sometimes with bespoke and complex glazing designs the coating may need to be applied to the inner pane, which will still function but with less efficiency, meaning that a higher level of solar control may be needed which may mean less light transmission. 

Depending on what the architectural drawings say the glazing needs to achieve, IQ’s design team will work closely with glass suppliers to ensure this is achieved.  

One of IQ's projects was a contemporary home in Devon, Sanctuary House, which used solar control glazing for most of the external glazing solutions combined with a timber-lined overhand on the top floor. This design helped to prevent overheating in the highly glazed home design whilst also reducing solar glare, as one of the homeowners has a degenerative sight issue which required lots of light but no glare.  


Approved Document F about ventilation  

There are many benefits to increased ventilation for interior spaces, including helping to remove moisture, smoke, cooking odours and indoor pollutants from the living spaces.  

Approved Document F of the UK Building Regulations is designed to ensure that ventilation not only delivers the required airflow but does so efficiently and quietly. 

Approved Document F about ventilation to help combat overheating

This can be done in the form of opening glazing elements such as windows and doors, as seen in our Edge Hill project in Newcastle (pictured right), or by utilising one of our automated rooflight systems such as the M.A.R.S automated sliding rooflight system or the A.R.E.S automated venting rooflight system for ventilative cooling.  

By ensuring a home has adequate ventilation and incorporating opening glazing elements, this aids in preventing overheating in highly glazed home designs.

This is most effective when opening elements are strategically placed in the home to allow for cross ventilation.  


External Shading Solutions to Prevent Overheating

Alternatively, you could shade large elevations of glazing from solar radiation using external shading solutions. On the external face of properties, large elevations of glass can be shaded by canopies, awning roofs or a louvre roof system. The louvre roof system from IQ is designed with flexibility in mind and is the perfect addition to any glazing package.

A luxury external facade shading system can also be specified as part of your IQ glazing package. This new and innovative external façade shading system has been designed to allow for
seamless integration with the external cladding of any building. 

External Shading Solutions to Prevent Overheating

Vertical fixed louvres can also be incorporated into a contemporary home design.

Treeside, an incredible new build in Surrey that specified IQ glazing, has vertical louvres on the outside of various glass walls and oversized sliding doors around the home, including on the exterior of the glass wall with a Juliet balcony in the bedroom.

This helps to prevent overheating and provides privacy, while still allowing in a vast amount of natural light.

Natural shading solutions can also be utilised, such as surrounding trees or buildings. Clever architectural designs that prevent the glazing from being in direct sunlight for most of the day can help significantly with reducing overheating in highly glazed home designs. 


Luxury Homes With Timber Shading Overhangs 

For one-off new build homes, timber overhangs can be designed to shade large elevations of glazing around the home. IQ's bespoke glazing solutions have been specified on a wide range of projects that utilise this.

Luxury Homes With Timber Shading Overhangs 

Stonecrop, an award-winning sustainable home in the East Midlands, is an excellent example of where timber and architectural glazing have been combined to help the home merge with the surrounding landscape

The bespoke timber ceiling was continued to the exterior of the home, protruding out and creating an external timber overhang that provides shade for the structural glass walls and helps to prevent overheating in the interior space of this highly glazed home design.  


Internal Shutters  

Research conducted by the BBSA shows that internal shading can reduce room temperatures, although factors such as colour can affect their effectiveness.  

Unlike curtains, internal shutters can reflect some of the rays back through the window, especially when specified in white or a light colour.

do internal shutters combat overheating

However, internal shutters have a limited effect and external shading is significantly more effective in preventing overheating.

With any type of internal shading solution whether it shutters, blinds or curtains, there is also the risk of heat energy becoming trapped between it and the window, which can create a chimney effect and actually end up heating the interior space. 


Water at the Perimeter of the Building 

By incorporating outdoor water features such as a pond or a pool, this help to enhance evaporative cooling. 

Open bodies of water around the edge of the home exploit a phenomenon known as phase change, the same physical process that makes an air-conditioning unit work, or helps a tree to cool the air around it.  Water at the Perimeter of the Building to prevent overheating

Liquid moisture is wicked away by warm air, which it readily absorbs as water vapour. To change from dense liquid to light gas, the water needs to draw energy, as heat, from somewhere to help it over the hump of that change. 

A garden room on Melbury Road in London has glass walls the whole way around the build, created using structural glass walls and slim framed sliding doors.

The glass garden room is surrounded by a moat-like water feature that aids in preventing overheating inside the glass box. 


Although overheating is an issue, solar gain is not. Solar gain can actually be utilised as an environmentally heated solution in contemporary home designs, but this is a delicate balancing act and needs to be combined with solutions in this article to ensure that this does not lead to overheating in the home.  


An excellent example of this is our Cotswolds project, which was granted planning permission under paragraph 80 (previously paragraph 79), which has a structural glass wall and slim sliding doors across the whole south facing side of the home. 




For more information about how to prevent overheating in highly glazed home designs, contact the IQ team today.