The right daylighting strategy can greatly improve the quality of your family’s life at home for little or no extra expense.
Does a bad-weather day leave you feeling "stuck" inside, or do you smile at the idea of enjoying what a great house you have? Most likely, some spaces in your home are too dark or gloomy, others get too much direct sun, and your family usually has all the lights on to avoid feeling depressed or claustrophobic. As a result, some parts of the home are underused, the family's less inclined to spend quality time together on a cloudy day, and you're paying for dozens of lights turned on all winter.
I embrace detailed analyses right at the early design phase and can help you build plenty of natural daylight into the design of your new house. Enjoy spending time with your family in a bright home instead of wandering between gloomy rooms that are too dark and rooms that have horrible glare. Stop paying for all those lights being left on all the time and start being able to enjoy every square foot of that house you've paid to build.
By the end of this article, you'll have a better understanding of the main parts of a daylighting strategy: how much and what kind of light enters the building, when and where the light enters the building, and how the light moves around once it's inside.
BENEFITS OF DAYLIGHTING
Natural light is a powerful aspect of a well-designed building. Daylight in buildings improves both energy efficiency and occupant comfort. In addition to the scientific calculation of distributing light throughout a building and the subjective study of the impact of natural light on psychology, great daylighting is also an art that builds interest throughout a space. Variety of light is sometimes just as important and effective as uniform lighting in others. For example, bright, focused light is appropriate for special areas of interest or circulation.
Daylighting is mostly a passive system of crafting where, how much, and what kind of light enters a building. Passive daylighting is essentially the collection and reflection of sunlight and daylight from the well-lit parts of a building into the darker areas to promote a more even distribution of light without the use of special mechanical devices or added energy. The primary goal is to minimize the need for lights throughout the year, and the secondary goal is to capture enough solar energy in the winter to reduce heating requirements. Daylighting used to be an art of architecture before the proliferation and sophistication of artificial, electric lighting. It's experiencing a renaissance as energy codes encourages the building owner to focus on energy efficiency and occupant health.
BUILDING DESIGN IMPACT ON DAYLIGHTING
Regardless of the building type, daylighting does not mean adding windows and making them bigger. It is a system which must be designed to balance the occupants' needs with the home's context and the effects of design decisions. Since each building and its context are unique, the daylighting strategy must also be tailored to the project and the activities within.
The daylighting design begins before designing windows and skylights. Early in the design process, one must consider the building orientation, building form, and location. Orienting a building East-West is generally the simplest and most effective way to maximize exposure to sunlight and minimize the depth that the light needs to penetrate. This long façade exposed to the sun's arc across the sky is also an easy means of capturing solar energy during the winter. The surrounding topography also impacts available daylight. A house in a valley, at the foot of a mountain, or in a forest will receive less sunlight than a house on a hill, near the top of a cliff, or in a clearing.
WINDOWS
The location of windows is subject to factors that sometimes contradict each other: exterior view, interior illumination, and solar heating.
Size windows appropriate to the climate to avoid undesirable heat loss during cooler weather. Reduce window size as much as possible except where needed specifically for a view. Small windows properly located and oriented will provide ample, quality, useable light with minimal unwanted side effects.
Eliminate glazing below 30"-36" unless a view downward is specifically important. For example, if you overlook the waterfront or are located at the top of a valley, you may want to see down. Otherwise, the additional glass only yields unproductive daylight and reduces the building's overall insulation value.
Use tall windows instead of wide windows. The window head height determines how far daylight makes its way into the home.
Design light to enter a room from two sides wherever possible. Illumination at a given time of day is better, and there won't be a time of day when the room is quite dark. Courtyards are historically an architectural solution.
OTHER ACCESS TO LIGHT
Increasing the size of windows is not the only way to allow more light into the building. Daylighting features include:
Skylights
Clerestory windows; these are separate windows that are above head height either in the wall or in a raised portion of the roof.
Light wells
Flared window openings inside, outside, or both: this is especially effective for high-performance houses in which the walls are thicker.
DAYLIGHT CONTROL
Consider solar heat gain control in conjunction with daylighting; too much is as bad as too little. Exterior shading devices and other solar devices are commonly used to reduce direct sunlight especially in hot climates, but they can also be used to diffuse natural light and reflect it into the space. These devices may be exterior or interior, and they may be fixed-position, manually adjustable, or automatic.
Overhangs (roof or the floor above)
Light shelves
Horizontal louvres
Vertical louvres
Brise-soleils
The angle of horizontal louvres or brise-soleil features may be designed or adjusted to suit the angle of the sun for the latitude at which he building sits.
Screens (commonly used in architecture of the Middle East)
Vegetation - deciduous trees will reduce excess sunlight in the summer but allow more low-angle sunlight into the house during the winter when the trees are bare.
The properties of window glass itself - visible transmittance and solar heat gain coefficient - play a role. The glass can be tinted, and the darker glazing will reduce the overall level of visible light passing through. A special coating is typically used to reflect the portion of sunlight responsible for most of the heat gain; the result is a larger window without a corresponding increase in unwanted indoor heat.
LIGHT WITHIN THE HOUSE
Design elements such as mirrors, light tubes, light shelves, and reflective surfaces to direct light through the building. The colour and texture of interior surfaces also affect how well light is reflected into the building.
Shiny ceilings or walls highlight material imperfections, so we usually rely on white or near-white paint to improve reflectivity - particularly on the ceiling where it has greatest impact.
Glare control is a consideration not only for direct sunlight but for reflective surfaces. Glossy floors must be located with care and in conjunction with the study of window locations to avoid unwanted glare.
ARTIFICIAL LIGHT
Even with well executed passive design strategies, electric lights are unavoidable both as a code requirement and to provide light in buildings at night or even adequate illumination levels at some times of day. Electric lights should be energy efficient to minimize waste heat. Artificial lighting should be colour-corrected to suit the type of natural light entering the space. For example, LED lights are available in warm, daylight, or bright white.
Light fixtures should be aligned parallel with windows so that the artificial light supplements the natural light rather than compete with it.
Lighting design should incorporate photosensors or occupancy sensors where practical to turn off or turn down artificial lighting automatically. Indoor lights are less bright than outdoor light, so you may not notice them being left on. This wastes electricity and creates waste heat that you need to cool during the summer.
CONCLUSION
A daylighting design process can become a very complicated exercise. There is a limit to the return on invested time and effort though, as human behaviour and unpredictable weather have a significant impact on the indoor environment. Keep in mind a subjective perspective based on how the sunshine can be expected to enter. As long as your daylighting strategy has taken into account the key elements above, your family can be expected to enjoy their home year-round.
