Solar heat gain
Designing for daylight is often a balance of admitting light while blocking solar heat. In warmer climates, building design is dominated by a year-round need for cooling. While cooling is still relevant for commercial buildings in cooler climates, heating begins to play a bigger role.
It is particularly important in the mornings, when the building is cooled from the previous night and occupants are just arriving. The fraction of incident solar energy a window transmits into a building is called the solar heat gain co-efficient (SHGC), which is commonly a static property of the glazing system. Building designers have to balance the opportunity for passive solar heating against the risk of increased summer cooling when selecting the glazing assembly. For warmer climates, where cooling is used nearly all year, the decision is a simple one. However, for cooler climates, designers and engineers must put much more effort into optimizing glazing properties and also account for building shape, orientation, functional use, and climate, if one wants to minimize energy used for HVAC.
Solutions to maximize daylight
Daylighting requires natural light, and the amount of natural light available to any given structure depends on location, particularly the latitude of the building site. Latitude determines the availability of sunshine and the sun’s angle—important considerations when designing for daylight. However, the best daylighting strategies can fail if there is not an intelligent way to manage sunlight.
Automated shading systems with smart control capabilities lower shades when there is an elevated risk of glare and raise them when the sun is not shining on the façade. Given manual shades tend to stay down, the biggest benefit of smart shading control systems is they remove impediments to daylight when shading is not necessary. In Canadian cities, where shades are needed on nearly all sides of a building, smart control systems substantially increase daylight infiltration.
Windows featuring smart-tinting glass show the most promise in maximizing daylight and views in buildings, as they can offer both a high SHGC when clear and a low SHGC in the dark state. In winter, smart-tinting properties can keep the windows clear on the east façade to help heat the building before employees arrive. In the summer months, the east windows can be tinted in the morning to keep the building cool. Smart-tinting windows enable full automation of when to clear/tint and by how much. Since they can be programmed to clear groups or individual windows when there is diffused light and to tint to mitigate glare, natural light is maximized at all times while controlling solar heat gain.
Successful daylighting design for high-latitude projects incorporates shading with sufficient opacity to prevent glare from the direct sun on all façades, as well as smart controls that retract shading or untint windows, while also selectively admitting or rejecting solar heat gain.