Modeling Suntubes to Design for Daylight

The benefits of natural light within the built environment have now been researched, written about and accepted as a fundamental design characteristic in successful architecture. Creating a connection to the outdoors provides the stimulation required to regulate our circadian rhythms, which can result in improved comfort and productivity. In addition, increasing natural daylight in our homes and work environments decreases the demand for electric lighting and therefore, electricity consumption.

While traditional skylights can provide a good visual connection to the outdoors, suntubes are better insulated, are more efficient at distributing daylight without glare, and don’t have the ‘thermal liability’ of a skylight. Suntubes, Solatubes, SunTunnels, Solar Tubes - whatever brand or label you choose - all are products we often recommend in our projects that have proven to be a real asset to daylighting design. Although they are often located in a project using ballpark guidelines, computer daylight modeling provides more opportunity for strategic placement.  Below are two of our recent projects with examples of how the products were used, lessons learned, and best practices.


Lompoc Transit Center

The Transit Center was built with four large commercial bays that included fleet maintenance spaces, a bus wash station, office space, support and storage space. The client’s experience at other facilities was that the bay doors were being left open to bring daylight into the spaces which caused issues with wind, dust and glare. Rather than closing the doors and installing high bay electric lighting, we were brought onto the team to investigate suntubes as an alternative solution. We ran daylight simulations comparing light levels for different times of the year, with the bay doors open and closed, with different quantities of tubes, and an option of Kalwall systems in certain buildings.

A sample comparison below shows daylight levels on a summer day with eight tubes (left) versus sixteen tubes (right):

Screen Shot 2017-12-11 at 7.59.30 PM.png

The suntubes were very effective in bringing highbay light into a space without using any electricity.

One complication for this project was when we began designing the roof top solar arrays. CalFire requires a 4-foot clearance around all openings, including suntubes, and at the eaves. In our effort to properly daylight the spaces that could not be effectively reached using side lighting, we were also carving out roof top area that would be unavailable for solar modules.

A solution that emerged was moving some of the planned solar PV panels to the canopy over an adjacent work area.  This allowed some of the electricity generation to be assumed by a concentrated installation, while freeing up space on the main building for daylighting mixed with a smaller PV footprint.


Financial Building

This project comprised a three-story multi-use building with significant glazing on all orientations, using a spandrel glazing system. We assisted the design team in improving the building’s daylight by making suggestions such as glazing performance specifications, altering the footprint shape and rearranging interior spaces to increase the depth of daylighting.

Through modeling, we demonstrated that a thinner footprint provided greater opportunity for daylight and had improved energy performance. The architects - Arris Studio Architects - were then able to create a building with great perimeter daylighting. We then focused on improving interior spaces such as common work areas of the third floor. We recommended a “shared light” strategy where suntubes were placed throughout the corridor, and the interior office doors were changed from solid to glazed, creating more consistent light levels on the top floor from the perimeter to the core.

Initially the owner group also wanted a large skylight in the lobby area but after modeling different scenarios, we suggested multiple suntubes that would still provide ample daylight but reduce glare, prevent UV-light from fading the furniture, and reduce heat gain that would have occurred with a single large skylight. You can see in the image below that four suntubes were located in the interior rectangular space directly in front of double doors to bring in light for occupants deep in the space, while single suntubes provide daylight to both the corridor and the adjacent interior spaces (through glazed doors).


Screen Shot 2017-12-11 at 8.06.53 PM.png

Suntubes, interior glazing, a thinner footprint, and coordination with roof-mounted solar panels are all strategies to achieve a high performance building that is a great place to work. To achieve all that, daylight modeling is a great tool for effective design decisions.