Avoiding the ill-effects of poor fenestration design

From enhancing wellbeing to reducing heat loss and energy bills, there is more to good fenestration design than meets the eye. The term ‘fenestration’ itself encompasses a wide range of systems that each have more than one purpose, and the size, style, and positioning of all glazed units need to be carefully considered. Windows provide both daylight and ventilation, but must also limit heat loss to prevent damp or draughty interiors. Doors must be safe and secure, but also easy to operate and maintain. Curtain wall systems, widely favoured for aesthetic reasons in the commercial sector, can also help 
improve the overall thermal performance of the building envelope. Balancing performance with practicalities and style together with sustainability can be a challenge, but this need is also what has driven innovation in the industry, and in terms of sustainability, aluminium systems are leading the way.

Why aluminium systems are fit for purpose

Popular on new-build developments, aluminium fenestration systems are also the ideal choice for replacement and retrofit projects. As the development of thermally efficient aluminium windows systems has come on leaps and bounds over the last decade, this means that many older healthcare buildings don’t come close to complying with the 
current regulations. The reality of this is that these buildings are also more expensive to heat. With energy costs at an all-time high, replacing and upgrading windows to a system that is not only easy to maintain, but which also gives exceptionally low U-values by retaining more heat, is a wise investment for the healthcare sector. The added benefit of switching to an aluminium window system with a high performance thermal barrier is that they are built to last and require little or no maintenance throughout their lifespan. The durability of aluminium windows can be further enhanced by powder coating, which enables new windows to be colour matched to any existing fenestration systems that are to remain in place. Upgrading to more energy-efficient windows which don’t create any cold spots or draughts can also create more adaptable interior spaces by enabling radiators to be 
moved from their conventional positioning under the windows.

Understanding U-values

When we talk about the thermal performance of fenestration, what we are really concerned about are U-values. Put simply, when it comes to U-value ratings, less is more, and the lower the figure, the more heat is retained. The U-value of a window system is dependent on a number of factors, including the frame material, the type of glazing, and the use of a warm edge spacer bar which provides the space and insulation between the two or three panes of glass.

Thermally broken aluminium windows are particularly effective at achieving lower U-values and preventing heat loss. Most systems on the market use a strong polyamide as an insulator to prevent heat loss between the inner and outer frame, but it has also been possible to create a system that incorporates an even more effective thermal barrier made from expanded polyurethane foam — a material more commonly used in insulation and cladding products.

However, is less always more? It’s important not to take any quoted U-values at face value, but to view them in the context of both operational and embodied carbon. Is the system fully recyclable? Is the manufacturing process energy-intensive, and is the carbon footprint around transportation
a concern? Aluminium systems can
often provide the solution, as products such as those manufactured by 
Senior offer cradle-to-cradle recyclability and exceptional durability. Choosing a UK-based manufacturer will also limit 
the amount of mileage, and therefore carbon, generated through the distribution and delivery of fenestration products to site.

Opening up door options

As heat can also escape through doors, it is important to choose a door system that can achieve low U-values so that the amount of energy lost is minimised. Automatic opening and sliding doors are of course a common feature in hospital environments, as they save space and reduce the number of touchpoints. However, it’s essential to routinely check that doors all work effectively, as those that stay open for too long, or do not fully close, will contribute to further energy loss.

Glazed doors can aid navigation and boost daylighting, and although they may not be suitable for areas of healthcare facilities where a greater level of privacy is required, they can make a huge difference to the main entrance and communal public areas. Aluminium-framed commercial doors are also suitable for interior spaces, as they are non-corrosive, meaning they can withstand the rigorous cleaning procedures required of a hospital environment without any detriment to the quality of their finish. Glazed aluminium internal doors also allow natural light to flow, and any obstacles or other building users to be easily seen, so that accidents from collisions can be avoided.

Daylighting by design

The link between natural daylight and wellbeing has been well documented; providing those who are using a healthcare facility with uninterrupted views of the outside can have a positive effect on their wellbeing and recovery. The strength of aluminium allows larger expanses of glazing to be supported in much slimmer frames to maximise daylighting, and as there are so many different shapes and sizes available, an aluminium window can open up even the smallest room.

The use of aluminium curtain walling can also transform a building’s façade, maximising natural light, and creating a clear connection with the outside areas. Whether curtain walling is being used to frame a striking external entrance, create a feature glazed atrium, or is being installed internally to ‘zone’ open-plan communal spaces, choosing a slim-profile system will create a much sleeker effect.

Mitigating solar gain is also a key consideration when a building incorporates a large amount of glazing, and here the use of a louvre system will not only help, but can add another aesthetic detail. Choosing a curtain wall system that is fully compatible with the specified aluminium windows and doors is another way to create a more energy-efficient façade.

Giving ventilation a boost

Creating a well-ventilated space is also crucial for healthcare settings, and replacement windows need to feature easy-to-use opening mechanisms or trickle vents. Bear in mind that trickle vents will affect the U-value performance of a window, so always be sure to push your supplier to provide the most accurate thermal calculations from the offset.

There are many styles of opening mechanisms to choose from, but this function must be taken with a view to safety, and specifically how falls from height can be prevented. The use of window restrictors is a standard procedure, as outlined in the Health Building Note 00-10 Part D: Windows and associated hardware, but a window replacement strategy also opens up the possibility of the use of new innovations. For example, a parallel push-style window can be a safe option for controlled ventilation and airflow. With hinges on all sides of the frame, the window can be easily pushed open, and yet will remain parallel to the wall. This enables rooms to be safely ventilated, with the limited opening helping to reduce the risk of falls from the window.

With so much to consider — not least the challenge of working on existing healthcare facilities which are still operational, specifiers responsible for updating NHS estates face a huge and complex task. Tapping into the expertise of the supply chain can highlight areas where additional savings can be made, both in terms of maintenance costs and embedded carbon. At Senior we have launched a new consultancy service to advise on how the retrofitting of new aluminium fenestration systems can help to create healthier and more sustainable buildings across the healthcare sector.