Natural Lighting

Natural lighting, also known as daylighting, is a technique that efficiently brings natural light into your home using exterior glazing (windows, skylights, etc.), thereby reducing artificial lighting requirements and saving energy. Natural lighting has been proven to increase health and comfort levels for building occupants.  

We start our discussion by defining the sources of natural lighting. Then in order to better understand the design principles and the daylighting fixtures available, we introduce natural lighting design and daylighting fixtures. Lastly, we include cost analysis to help you evaluate the most cost effective options.  

Effective natural lighting will admit natural light, but will avoid admittance of direct sun on task surfaces or into occupants' eyes. Daylight inside a home can come from three sources:  

Direct sunlight

direct light from the Sun.  

External reflection

light reflecting off of ground surfaces, adjacent buildings, light shelves, and wide window sills. Excessive reflectance is undesirable as it causes glare. 

Internal reflection

light reflecting off of internal walls, ceiling, and the floor of your home. This also includes high reflective surfaces such as smooth or glossy surfaces, light colored finishes, and mirrors around a room.

Most daylighting components are integrated in the original construction plan, however, technologies such as tubular daylighting devices, skylights, electric lighting controls, and optimized interior design may be considered in retrofit projects. 

The science of daylighting design is more complex than simply bringing light into a home. When adding a daylighting fixture, you must consider balancing heat gains and losses, glare control, and variations in daylight availability. Additionally, window size and spacing, glass selection, the reflectance of interior finishes, and the location of interior partitions all must be considered. Furthermore, there are many different types of daylight fixtures and each has its own unique set of design considerations.  

If you're considering implementing a natural lighting window, be sure to check out Windows and Rooftop Page to better manage the heat gains or losses through the daylighting source.  

Video filmed by the U.S. Department of Energy 

Daylighting Fixtures

Windows

are by far the most common daylighting source. Windows specifically used for daylighting are generally implemented in the design phase since the window head height and glare control is easier to deal with during that time.                     

Skylights

are a common top lighting source, and are implemented in the design phase. Skylights can be either passive or active, though the majority of skylights are passive. Active skylights are windows that have a mirror system within the skylight that tracks the Sun, and are designed to admit more sunlight by channeling the light into the home.                                                                                                                                                                                Image source: yourhome.gov.au                        

Tubular lights

also known as solar tubes, are light channels that allow light to enter from the roof and be reflected using mirrors into a home. They have become more popular for top lighting in recent years. This is largely because they can be installed in retrofit projects easier than skylights and are cheaper for the homeowner.                                                                                                                                                                                                                                  Image source: inhabitat.com

Redirection devices

take incoming sunlight and direct it towards the ceiling space. They aim to reduce glare and to increase daylight penetration. These devices typically take on of two forms: louvered systems or a large horizontal element. Horizontal elements are commonly referred to as light-shelves.                                                                                                                                                                                                                                                                                           Image source: iitbuildingscience.wordpress.com

Solar shading devices

are often implemented to control the solar gains and potential glare from windows. These shading devices include overhangs and blinds.                                                                                                                                 Image source: sustainabilityworkshop.autodesk.com

Daylight-responsive electric lighting controls

incorporate photocells to sense the available light and act accordingly by dimming or turning off the electric lighting system in response.                                                                                                                                                       Image source: www.digikey.com

Solar-tubes can cost as little as $500 (This Old House), while most homeowners spend about $600-$1000 per window added to a home (Home Advisor). Designing a new build for effective natural lighting fixtures may add little to no cost to the overall house construction costs.7

Depending on how much artificial lighting is offset, natural lighting renovation payback can range from 5–50 years (considering lighting use only). The overall payback can be greatly reduced if the natural lighting fixtures are installed on the south face of your home, as you will receive passive solar heating benefits from the fixture. In Ohio energy losses from windows on north, east, and the west side of a home are always net loss due to conductive losses, while windows within 30 degrees of true south are energy gains (due to solar radiation gains in the winter).  

 

 

References

"Natural Lighting in Home Design: So "lar" So Good" by greenbuild.org. 

A discussion of natural lighting design in new home construction.  

2  "Siting with the Sun: Passive Heating and Daylight" by greenbuildingadvisor.com

How to design around the sun to lower heating and lighting needs.  

3 "Passive Solar Design Strategies" by the National Renewable Energy Laboratory.  

A large document with detailed discussion into passive design building strategies for residential houses in Columbus, Ohio.  

4  "Daylighting" by level, a sustainable building design website.  

Article discussing the sources of daylight, how to maximize daylight penetration, and how to passively improve interior lighting levels. 

5"Daylighting" by Gregg D. Ander of the FAIA Southern California Edison; updated by the U.S. Department of Energy Federal Energy Management Program (FEMP) 

An in-depth view of the application of these natural lighting arrangements and technologies.

A short article discussing the cost of a natural lighting light tube versus a conventional window installation.  

A cost analysis for adding 1-10+ new windows to a house.  

9"Lighting Efficiency" by Center for Climate and Energy Solutions 

A discussion of all aspects of lighting efficiency, including a short discussion of natural lighting source considerations.