Natural Light Requirements for Commercial Buildings
23 December 2021
Natural Light in Buildings: Rules and Recommendations
IN BRIEF
- A comfortable and functional building requires natural light, however there are specific requirements you need to adhere to in order to meet Section J energy ratings.
- A Section J report focuses on energy efficiency, including the use of windows or skylights to reduce dependency on artificial lighting (and lower your power bills).
- Having plenty of natural light in your structure saves electricity, improves the working environment, enhances ventilation, and boosts the well-being of occupants.
- The number of windows needed is calculated based on the floor area and the building’s purpose. Skylights can be an alternative but they require careful consideration for heat and insulation.
Natural Lighting Requirements to Meet Energy Ratings
Designing your structure for the most energy-efficient result means that you’ll need to incorporate a certain amount of natural light. A building that is designed to capture available sunlight without heavily increasing heat will create a light, bright, airy space for your commercial building – and ensure you meet your Section J requirements.
Section J Specifications and Natural Light
Steelcorp’s Aaron Barker explains that “A Section J Report highlights the energy efficiency requirements for non-residential commercial buildings such as warehouses and factories. Covering a range of different categories, the Section J report looks at things like heating, ventilation, the performance of the building materials, glazing, and the efficiency of artificial lighting.”
“The overall aim of this report is to determine how much energy a structure will use and whether particular areas could be improved upon to reduce its ongoing energy consumption. It is part of the National Construction Code and is something that an architect or a qualified energy efficiency consultant can help you with.”
Part of the Section J will cover the requirement for natural light, through either windows or skylights. This will reduce the dependence on energy-hungry artificial light, and ultimately help to reduce your power bills in the long run.
Why Buildings Require Natural Light
Aaron notes that all habitable buildings such as homes have a mandatory requirement for windows to let in natural light. However, structures that will be used for commercial purposes also have their own set of requirements.
“Along with the Section J report which focuses on energy efficiency, there are some more general requirements around daylight and ventilation to keep the building and its occupants safe and healthy,” says Aaron.
“Allowing natural light into your commercial building not only saves on electricity but also helps to create a more comfortable working environment for your team. Windows can be opened to help improve ventilation and indoor air quality as well as improve well-being. Natural light is an important part of creating a healthy workplace, boosting serotonin and melatonin levels in the body for better mood and sleep patterns.”
It’s interesting to note that airflow through a building is improved when a mixture of both high and low openings are provided, so positioning windows at different heights can help boost air circulation.
How to Work out How Many Windows You Need in Your Structure
Your natural light requirement is calculated based on the floor area of the space, and what the building will be used for. Most commercial buildings fall under Class 7, 8, 9 or 10, depending on what kind of business will be conducted on site.
An architect can help with your specific design, but in general, window openings need to cover a certain percentage of the total floor area, often between 3% and 10%.
Light can also be ‘borrowed’ from adjoining rooms or spaces, so you can assess the total area of two rooms combined.
“Skylights or roof lights are another way to add natural light to your steel building, and because they directly face the sky they let in more light than a window,” adds Aaron.
“This means you can achieve a brighter result using roof lights or a combination of roof and window openings. Because more light is let in from above, the total percentage of space dedicated to roof lights can be less than that of windows.”
A few notes on skylights: it’s important to understand that skylights let a lot of heat into the interior so can make it less energy efficient in that sense. Additionally, wherever you have a gap for a skylight in the roof, of course, there is no insulation in that area. As a good compromise, we often suggest adding a skylight ‘skirt’ up high on the wall, enabling light to flow in and still allowing for good insulation.
In any case, it’s important to get advice from your architect on the best way to include natural light in your building design.
