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How to marry comfort and performance with low carbon in use

Words:
Ricardo Moreira

How do reconcile the conflicting needs of noise and temperature control on a design that favours window opening over air conditioning? Technology has the answer

Indoor environmental comfort depends on various factors – radiant and air temperature, air movement, air quality, noise, daylight and views, to name a few. Though they interact, we still tend to tackle them in silos. Parametric modelling can help navigate these often competing demands to support a holistic approach.
 
The Association of Noise Consultant’s recently published Acoustics, Ventilation and Overheating Guide starts to address the interaction of overheating and noise. It tries to move noise targets towards a more nuanced view that includes natural ventilation needs (though air quality is dealt with as a limiting factor, driving buildings towards mechanical climate control). 
 
Since noise and overheating mitigation call for opposing solutions on window opening, the guide – facilitated by dynamic simulation software such as IES and TAS – promotes the identification of the times windows need to be operated, which can then be correlated with the review of noise levels under more flexible targets. Design solutions such as acoustic attenuation panels and balconies can supplement that approach. In urban areas, however, it is still very challenging to meet acoustic targets, so facade design needs to be well thought-through. One thing is clear: both comfort aspects benefit from limited glazing sizes – smaller is better. 
 
However, with overheating/daylight, the latter benefits from larger window areas. This area has seen the publication of a recent standard, BS EN 17037, which takes a more flexible and site-specific approach. Unlike the traditional BRE method, its climate-based analysis considers location, orientation and seasonal variations. This should allow external shading to be applied to areas of a building which receive more sunlight, such as overhangs and balconies on south facades, without endangering daylight targets. The standard’s view-out requirements prioritise glazing width, indirectly penalising full-height glazing, which can only be seen as a plus for overheating risk mitigation. Apart from industry standard software such as AutoCAD with MBS plugin, parametric tools can be useful here.
 
XCO2 has been using such tools at an early design stage to assess the interaction of overheating, daylight and energy performance. Using Rhino models with Grasshopper to explore design variations, Honeybee for technical simulations and Butterfly for thermal comfort, we can quickly determine the ideal combinations of window size and configuration, openable areas, external shading configurations, glazing specification and even acoustic attenuation panel areas for different facade orientations. The approach opens up exciting possibilities for earlier, more effective collaboration between architects and specialists, resulting in environmentally optimised buildings. At masterplan level, these tools and Ladybug are used for insolation modelling to inform massing configurations.
 
This shows the usefulness of considering environmental comfort and performance holistically. Software tools and new methodologies can help produce well-rounded robust designs. For that, it is crucial to collaborate early with consultants and to make environmental comfort and performance project priorities. 
Ricardo Moreira is co-founder and managing director of XCO2

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