As technological advances in both architectural materials and control systems facilitate finer degrees of management in a home, people’s expectations of comfort, control and energy efficiency are increasing.

The result can be an almost-symbiotic relationship, in which homes are able to work with their occupants in a more dynamic manner. One aspect that is attracting great attention is the use of light – both natural and artificial – and finding the optimum balance.

There is already a high awareness of the energy efficiency of a home and an occupant’s comfort that can be profoundly affected by the building’s orientation with respect to the sun. Sunlight falling on a building facade usually results in both heat and light transfer to the interior. While these may be welcomed during winter, they often cause problems through overheating and glare in summer.

The focus historically – especially in hotter climates – has therefore tended towards mitigation strategies against the effects of solar radiation. Fixed shading can prove effective in this respect, particularly in terms of blocking solar heat, which would otherwise lead to additional cooling; but in other cases some architectural design requirements call for alternative solutions.

Lately, emerging green targets and occupant comfort factors have spawned a new appreciation for the benefits of natural light – leading to the practice now known as ‘daylight harvesting’. This has shifted the focus towards house and apartment designs that are flexible enough to protect against the summer heat, while still able to embrace natural light and heat at other times.

Facade and fenestration

A key to finding the optimum balance of natural and artificial light is in the facade and fenestration design of the building. Dynamic facades, where motorised blinds help regulate different levels of protection, can accommodate a whole range of different scenic view, lighting and heat conditions.

From an energy management perspective, heat management takes precedence over light management, as heating and cooling account for a much higher percentage of energy usage than lighting typically does. Furthermore, with the growing market adoption of more efficient LED light sources, the difference in energy use between heating/cooling and lighting systems will increase even further in the future.

As such, it is best to use blinds to manage heat, as well as external light glare control, and then adjust the artificial light levels to where they need to be. As the sun angle changes and the heat-load diminishes, it will be possible to raise the blinds to take advantage of natural light and minimise the lighting component of energy usage as well.

Part of the challenge is to ensure the solution is flexible and intelligent enough to accommodate multiple indoor environmental scenarios, such as balancing light from natural and artificial sources and taking spatial-zoning and occupancy into account. It also includes integrating motorised blinds where applicable and adding the smarts to optimise the interaction with the lighting.

Sense and sophistication

The simplest form of an integrated lighting and blind system might use a timer to change blind settings depending on the time of day and season, with the lighting levels automatically adjusted accordingly. The introduction of sensors and more sophisticated programming, however, make for a system that responds to real environmental factors and delivers enhanced energy and natural light benefits.

For example, a blind position may be determined by readings from an external solar sensor, which measures sunlight incident on the building. If the measured solar radiation is above a certain threshold, the sensor communicates with the control system and instructs the blinds to close, thereby restricting the heat entering the building.

As the blinds are raised or lowered, the changing level of incoming daylight is measured by strategically placed light level (or daylight harvesting) sensors, leading to corresponding adjustments to maintain preset ambient lighting levels. It is best to set the dimming function to a very slow fade in order to maximise user acceptance. With gradual dimming over 30-second periods, occupants will not even notice the changes being made to the lighting levels.

Similarly, the responsiveness of the blind control system needs to be carefully programmed. To prevent blinds going up and down every time a cloud passes over the sun, systems are often configured with a built-in delay. For example, if the blind is automatically closed and the ambient lighting levels subsequently fall beyond the threshold, there will be a delay of typically 20 minutes before the blind reopens.

In the zone

Despite the benefits of an intelligent automated lighting and blind system, it is still important for residents to have a level of local control. Different people have different tolerances to light, so a manual override – available via a wall panel from the lounge, dining table, even the bed – provides a capability to make adjustments themselves. Most people are happiest when they feel as though they can exert an influence on their surroundings.

However, with the capacity for local control, there is also potential for individual users to collectively and unknowingly unbalance the carefully programmed settings for the building. To minimise the disruptive effect, presence detection sensors can be installed to detect when areas are unoccupied. The control system can then simply revert the settings for that zone back to the automatic defaults, when the space has been vacated for a certain length of time.

Careful allocation of residential floor spaces is essential for achieving optimal outcomes from integrated lighting and blind automation systems. If whole buildings were to be zoned as a single entity, regardless of the fact different areas experience different shading conditions at different times of the day and throughout the year, this will result in energy wastage and occupant discomfort.

Given the contribution of automated blinds to heating efficiency and the upcoming energy star rating system for homes, it is somewhat surprising that they are not always an automatic inclusion in ‘green residences’.

An integrated future

In practice, automated blinds can deliver a verified improvement to the measured energy performance of a home. Good results are dependent on careful spatial zoning, a holistic design approach and sound integration of communication protocols between the lighting and blind solutions employed.

Together, these factors represent the greatest challenges faced by most residential integration projects.

With improvements in integration between lighting and shading, homes and apartment complexes will work with their occupants more dynamically in the future to allow hitherto unprecedented levels of controllability and comfort.

Where comfort and efficiency have historically been regarded as incompatible goals, the careful inclusion of daylight control and harvesting technologies will serve to reduce overall energy usage while increasing indoor environmental quality in a more natural and sustainable manner.