Measure twice, cut once.
This old adage is one that craftsmen understand well and never question. Careful measurement and planning is essential in producing any quality product, and when it comes to the building industry, a lot of time and effort is spent on measuring and analyzing how a building’s design will interact with materials and environmental conditions like wind, sunlight, water and gravity. In the last couple of decades the building industry has gone digital, and building measurement and analysis tools have become increasingly high tech. Building Information Modeling (BIM) software is a relatively new, promising tool that allows architects and engineers to digitally model the different elements of a building (shape, structure, heating / cooling, cost, materials etc) in real-time and quickly understand how specific changes in design or construction models will impact other variables like structure, loads, energy efficiency and the fiscal bottom line. BIM has especially helped to enable sustainable design – allowing architects and engineers access to higher tech tools than ever before to carefully integrate and analyze things like heat gain, solar, ventilation, and energy efficiency in their designs.
WHAT IS BIM?
Building Information Modeling is digital software that creates a 3D representation of a building, which is layered with additional project information. It is sometimes referred to as a “5D representation of a building”, where the 4th and 5th dimension are time and cost. For example, using a BIM model, an architect could simulate how wind would flow around and through a building, and how that ventilation and wind velocity might change if the building’s shape or surface material was changed. Other additional information that can be modeled in BIM includes component details and specifications, materials, structural loads, air flow, water flow, spatial relationships, scheduling information, cost and more. These are often facilitated directly within a BIM authoring tool such as Revit or Ecotect. BIM is NOT the same thing as 3D CAD (computer-aided design) modeling – the fundamental purpose of CAD is to illustrate and help people visualize how a building will LOOK, whereas BIM provides detailed information about how a building will FUNCTION.
Architects and engineers like BIM because it helps save them time in the design process, and developers and construction firms appreciate how it can save costs in materials and labor. Building Information Modeling is best used when analyzing how a whole bunch of complex variables work together, and it streamlines the communication process between various parties involved in the design of a building, making it easier to design better buildings. Because BIM increases efficiency in the design process, it is a boon to sustainable design.
THE MIAMI SCIENCE MUSEUM
A great example of how BIM can help architects design greener buildings can be seen in the Miami Science Museum, which is currently being built down on the Miami waterfront as a beacon of 21st century sustainable design. As a dynamic cultural, educational and research science institution, MiaSci is focused on operating with the highest environmental standards, while contributing to creating a healthy regional economy and community. MiaSci has established a Sustainability Platform that aligns the organization’s mission, program and operations with the people, the planet, and prosperity. Creating a building that would reflect and create a space conducive to their mission was essential. Designed by Grimshaw Architects, MiaSci won a grant from the US Department of Energy in 2009 to incorporate BIM into the design process in order to explore different environmental issues during the design stage and to ultimately produce a greener building.
Case Building + Technology group lead the BIM consulting on the MiaSci project and helped Grimshaw specifically model how the solar strategies, water systems, and the shape of the building impact ventilation through the space, and how these elements could in turn be maximized to not only reduce their energy and external resource needs, but how they could fill these voids on site, independent of the grid or other parties.
The Miami Science Museum carefully integrates the direction and location of the sun into its design – engaging in both passive and active solar design strategies. BIM was used to model out varying solar conditions throughout the day and the year to help design the building shape, overhangs and PV installations. Solar panels cover areas of both the museum’s roof and facade for energy capture from the sun. Highly efficient thin film PVs have also been used in areas such as the atrium and skylights to power up the building, but never at the expense of natural daylighting. Passive solar strategies are well-integrated into the design, and provide a mode for both heating and cooling. In fact, in many instances the PV panels offer direct shading for the building and the interior.
MiaSci is a virtual sponge when it comes to water catchment. A belvedere water feature is designed at the roof of the building and uses the natural bio-filtration of rainwater through mangroves and other elements within the opening. The museum’s green roof and interior green wall provide further bio-filtration as well as a temporary means of rainwater retention for later irrigation. Rainwater harvesting is also done at the roof surface, and all captured water is stored on grade in the car park area. Any water in excess of capacity is directed to wetland or to injection wells. Moreover, the museum’s toilets are just as efficient, using treated greywater captured from basins, showers and building systems.
Hosting several water exhibits, MiaSci draws upon rain catchment and the local bay as its main source of water. Freshwater exhibits are supplied by filtered rainwater; and as the museum is sited next to the Biscayne Bay, an inlet has been constructed below the building to draw in seawater for the saltwater exhibits.
MODELING AIR FLOW AND VENTILATION
The shape of the MiaSci building is not accidental. The building form was deliberately designed in a specific way to work with the pattern of wind flow on the site, and ventilation and airflow in regards to building shape was carefully studied and iterated using BIM. The MiaSci building was designed as a solid block on the north and west boundaries of the site, and the southwest orientation was chosen to take advantage of the prevailing winds.
It was understood early on in the design process that the museum’s size and openings were paramount to effective cross-ventilation. To find a balance that created neither too little wind and was still not too windy for comfort, a close analysis of the wind velocities and potential pressure build-up in BIM gave way to the creation of a “canyon” (or a vertical) through the canopy above the undercroft of the museum to relieve the positive pressure. Various simulations through BIM proved that although the canyon gave way to an air flow of significant force, the effect was restricted to the ceiling of the undercroft, and the air conditions at the ground level remained pleasant and comfortable. Numerous iterations were modeled to determine the optimal roof form and height we see today.
Opening to the southwest, the museum takes advantage of the site’s prevailing winds for optimal cross-ventilation and comfort within the total space, as well as the parking lot below. Stacked administration and gallery spaces sit on the eastern end of the museum, and air exchange within these spaces is maximized through an adjacent atrium. While gallery areas are fully conditioned mechanically, the air that is exhausted into these spaces is recycled to pre-cool the fresh air of the atrium, which then flows to cool the administrative floor eventually being exhausted through an acoustic double skin. Photovoltaic wind foils tops off the roof at the western end of the structure, and the radiant heat absorbed by the back of the panels induce convective air movement. The ventilation measures created for the museum are a carefully calculated and succinct system arrived at through a series of BIM analyses. The system holds tight from the start of air flow at the entrance, to the release at the roof and opposite administrative floor, and each step is wholly dependent on the shape of the structure.
Integrating BIM as a key tool in the design process has given way to a streamlined exchange of building information models and analytical data between Case, Grimshaw and their team of consultants — which includes engineers at Arup and architects at Rodriguez & Quiroga. Using BIM, Grimshaw was able to integrate any feedback they received early on and refine their design accordingly to best achieve their goals, the goals of their clients, and to create a truly sustainable structure that would provide a precedent for future green building initiatives.