Capitol Tower

The Platinum Standard: Piloting the New LEED v4


Location: Houston, TX       
Owner: Skanska Commercial Development  
Size: 700,000 SF, 35 stories
Parking Garage: 1,360 spaces  
Expertise: Structural, Civil, and Traffic Engineering, Parking   
Architect: Gensler
Certification: LEED v4 Platinum Pre-Certification

The U.S. Green Building Council (USGBC) launched LEED v4, with its tough new life-cycle standards, in November, 2013. In the view of many, there is “before v4” and “after v4.” It is what some might call a green building game changer. In the words of Skanska’s Chief Sustainability Officer, Elizabeth Heider, “LEED v4 gives owners another reason to bring everyone to the table early on new building projects.”

This was certainly the case with Capitol Tower.

Textbook Teamwork

Shortly after the beta launch of LEED v4, Skanska Commercial Development, a subsidiary of Skanska Group, a global project development and construction company, enrolled their planned office building, Capitol Tower, in downtown Houston, in the program.

Teamwork was the central factor in successfully negotiating the learning curve during the beta program. One of Walter P Moore’s key operating principles (see our “5 Coordinates”), teamwork focused the entire team from the start on Skanska’s ultimate objective of achieving LEED v4 Platinum certification.

Capitol Tower is designed to be, in Skanska’s words, “the very model of a modern, sustainable office building.” When occupied, it will consume 25% less energy than the typical baseline performance (annual energy cost) of commercial office buildings. Along with rainwater harvesting, the building is engineered with a demand-control ventilation system, energy recovery wheel, and AcoustiFlow fans. The recovery wheel not only improves indoor air quality, it reduces total HVAC equipment capacity.  All of this requires the structure to make special contributions, as well.

It’s development unwittingly set in motion a number of sustainability “firsts.”

  • It was Skanska and Walter P Moore’s first project using the new LEED guidelines, with a steep learning curve.
  • The building earned LEED v4 Platinum pre-certification, a first in Houston and one of only three core-and-shell projects in the nation to do so. (Core and shell originated in the U.S. to help eliminate waste. Interior lease space is left undeveloped to be fitted out later by the tenant with materials supplied by the developer.)

Capitol Tower is also planned as the first large-scale commercial development to apply Whole-Building Life-Cycle Assessment (WBLCA) criteria under LEED v4.

A Materials World

One of the major changes to LEED standards in v4 is an emphasis on building products. In particular, the mix of ingredients in materials like concrete, which can make up a significant percentage of a building’s construction materials. Our goal was to reduce the quantity of cement in the concrete mix. The result?  Measurable improved environmental performance.  

We worked closely with concrete suppliers to understand the environmental impact of the project’s concrete in six different categories (CO2 emissions, depletion of stratospheric ozone, acidification, eutrophication, formation of tropospheric ozone, and depletion of non-renewable resources). Concrete suppliers don’t have ready reference to this kind of information. Using special software, we then re-crafted our specifications, clearly articulating them to ensure that they were understood by all.

By bringing Walter P Moore’s own multi-disciplined team to the table we were able to consider LEED v4 comprehensively and innovatively from the start, while learning and implementing design parameters for the new guidelines.

Aggressively Good

One of 100 projects to Beta test LEED Version 4, Capitol Tower is one of only three projects in the world to achieve LEED v4 Core and Shell Platinum Pre-Certification. While the project could have pursued certification under the current version of LEED, the developer, Skanska, elected to pursue the significantly more aggressive LEED v4.

To achieve platinum certification the project needed to attain a majority of the revamped materials and resources credits. This included the whole-building life-cycle assessment credit. Walter P Moore led the team, which was the only one to attempt this credit in the LEED V4 Beta program. This credit recognizes a building’s reduction in impacts associated with the manufacturing and erecting of materials.

We used the ATHENA Impact Estimator to help quantify the significant sources of environmental impacts. Based on our studies, the team developed a strategy of aggressive cement minimization, which leads to a 19% reduction in Global Warming Potential (GWP), a 12% reduction in acidification, and a 33% reduction in the production of ozone depleting materials.