P.O. Box 1209 
P.O. Box 1209 
Seattle, WA 98111-1209 
Seattle, WA 98111-1209 
Tel: 787-3000 
Tel: 787-3000 
www.portseattle.org 
www.portseattle.org 
SUSTAINABLE DESIGN APPROACH & SUSTAINABLE DESIGN STRATEGY 
WORLD TRADE CENTER WEST HVAC REPLACEMENT 
PURPOSE 
This serves as a summary document for the sustainable design coordination for the World Trade
Center West's (WTCW) Heating, Ventilation, and Air Conditioning (HVAC) Replacement project.
Additional information can be found in meeting minutes, commission documents, and the University
Mechanical Contractors December 2018 Investment Grade Audit & Energy Services Proposal and
mechanical system design documents developed by the firm Ecotope. 

SUSTAINABLE DESIGN APPROACH 
The WTCW HVAC Replacement project was identified as a pilot project for the Sustainable
Evaluation Framework. Staff hired consultants to provide alternatives to replace end-of-life HVAC
equipment. An internal interdisciplinary team was formed to evaluate alternatives to balance costs
occupant comfort, overall system and building energy efficiency, and advance the Century Agenda
greenhouse gas (GHG) goals. Meetings were held in late 2018 and 2019 to complete energy audits,
conduct building assessments, and identify potential components to form the basis of the HVAC
system replacement alternatives. Port of Seattle (Port) project staff met in January and February of
2020 to evaluate consultant audit findings and recommendations, prioritize goals, and identify and
compare alternatives based on the project's sustainability criteria. 
FRAMEWORK CRITERIA 
Coordination on this project and development of alternatives occurred prior to adoption of the
Sustainable Evaluation Framework and identification of the Framework Criteria. Goals identified
during project development align with the adopted Framework Criteria in the following manner: 
Reduce GHG Emissions/ Protect Health and the Environment. Staff created alternatives to
replace the end-of-life equipment while also maximizing overall system, building, and energy
efficiency, to reduce maintenance and operating costs, and to reduce GHG emissions. Tenant
health, comfort and disruptions during construction also were considered. 
PROJECT GOALS 
The Port's interdisciplinary team met in January 2020 to solidify project goals. 
Cost Effectiveness 
o  Balance project costs against environmental benefits 
o  Incorporate cost-benefit analyses for all alternatives, including life cycle cost,
incremental net present value, and carbon cost alongside capital cost 

Page 1 of 4

o  Consider project delivery efficiencies, including identification of additional work that
could be completed as part of planned primary HVAC replacement efforts 
o  Leverage energy efficiency measures to reduce utility costs for the Port and building
tenants and maximize utility rebates and incentives to drive down project costs. 
Greenhouse Gas Emission Reduction 
o  Eliminate use of fossil natural gas for heating to reduce greenhouse gas emissions 
o  Advance efforts to achieve Century Agenda goals 
Energy Efficiency 
o  Reduce building energy use intensity from pre-project 2017 baseline 
o  Maximize overall energy savings 
Impacts to Tenants 
o  Incorporate HVAC technologies that offer occupant comfort improvements 
o  Minimize disruption to tenants during the construction process 

SUSTAINABLE DESIGN STRATEGY 
The aforementioned goals were used to evaluate three design alternatives. A cost-benefit analysis was
assembled for each alternative and recommendations were presented to the project sponsors in
February of 2020. This project included replacement of the building's two HVAC systems and related
components that would be affected or could be replaced while working on these systems. 
DESIGN STRATEGIES 
Alternative 1: In-kind System. This was the original design plan for the project. It included a
like-for-like electric rooftop unit (RTU) replacement with no other proposed changes to the
WTCW's mechanical systems. This approach would incorporate a similar, but significantly
more modern RTU, powered by electricity, and use the existing ductwork and controls. 
Alternative 2: State-of-the-art System. This design alternative includes replacing the existing
RTU with a state-of-the-art high efficiency dedicated outdoor air system (DOAS) unit for
ventilation, upgrading controls, and a decoupled variable refrigerant flow (VRF) air-source heat
pump system in place of existing variable air volume boxes (VAV) for improved zonal space
conditioning. The project also includes replacing the kitchen HVAC system, which currently
runs on natural gas, with an electric system that includes hood and exhaust fans with variable
frequency drives (VFD), VRF electric heat pumps, and a small DOAS unit. This approach
would eliminate natural gas use for heating. 
Alternative 3: Hybrid Approach. This design includes like-for-like RTU replacement, a
controls retrofit, and replacement of existing VAV boxes with newer models. The project also
includes replacing the kitchen HVAC system, which currently runs on natural gas, with an
electric system that includes hood and exhaust fans with VFD, VRF electric heat pumps, and a
small DOAS unit. This approach would eliminate natural gas use for heating. 


Page 2 of 4

SUSTAINABLE DESIGN ALTERNATIVES ANALYSIS 
A cost-benefit analysis was prepared for each alternative. Table 1 provides the summary matrix of how
each alternative meets the project goals. It was determined that Alternative 3, Like-for-like RTU
Replacement with Controls Retrofit and VAV Box Replacement and Kitchen DOAS and VRF Heat
Pump, is preferred since it provides significant greenhouse gas reductions, eliminates natural gas as a
heating source, uses new HVAC technologies, and provides only moderate disruption during
construction and tenant comfort improvements at a marginal cost increase. Additional details are
provided below. 
Alternative 1: In-kind system. A new like-for-like RTU is the lowest cost alternative, disrupts 
tenants minimally, but provides low tenant comfort and minimal overall energy efficiency
improvements or greenhouse gas reductions. 
Alternative 2: State-of-the-art System. Use of a DOAS unit and air-source heat pumps to
replace the existing RTU and natural-gas fired kitchen HVAC system provides an innovation
example and an opportunity for the Port to pilot a state-of-the-art technology and achieve
significant energy reductions while eliminating natural gas for heating within the building. This
alternative presents the most innovative and ambitious approach to maximize energy efficiency,
occupant comfort, and greenhouse gas reductions, but it has the highest cost of all design
alternatives and largest disruption to tenants during construction. 
Alternative 3: Hybrid Approach. A more modern but similar RTU provides some energy
efficiencies but use of a small electric DOAS and heat pump to replace the existing natural gasfired
kitchen HVAC system provides an innovation example and an opportunity for the Port to
pilot a state-of-the-art technology while eliminating natural gas for heating within the building.
This alternative helps meet the project's energy efficiency and greenhouse gas reduction goals
through high efficiency components and by reducing GHG emissions from fossil fuels within
the building, but it is more costly, and construction is more disruptive to tenants than the base
like-for-like replacement. 

DESIGN ELEMENTS 
The detailed design elements will be part of the upcoming procurement for design and construction 
(Building Engineering Systems contract). This allows the Port to hire the contractor to design and
construct a custom system. A Basis of Design, including performance specifications, is being
developed as part of the Request for Proposals that is expected to be issued in August of 2020. 
Selection of a contractor will be based on meeting these design elements and performance
specifications. System performance will be monitored as part of the contract. 



Page 3 of 4

Table 1. Alternatives Analysis WTCW HVAC Replacement Project 
Greenhouse Gas Emission
Cost Effectiveness                                                                                 Energy Efficiency                           Impacts to Tenants 
Reduction 
Maritime/EDD
Expected
Building
20 Year      Capital Carbon     Lifecycle                                        Energy Use                                                         Tenant
Capital /                                                                                    Energy        Lifetime CO2                       Annual Energy   Level of Work
Incremental        Cost         Carbon Cost                                       Intensity                                      Construction      Comfort /
Construction    Life Cycle Cost                                                       Emissions        avoided                          Savings        in Tenant
Net Present      ($/Mt CO2       ($/Mt CO2                                        (reduction                                         Time        Temperature
Cost                                                                                  Reduction      (Metric Tons)                                (kBTUs)           Spaces 
Value          Avoided)         Avoided)                                        compared to                                                         Control 
(% from 2018
2017 baseline) 
Emissions) 

$0 
Alternative 1    $1.8M/1.3M        $3.3M                            $172,000        $318,000          0.0%              10             68 (2%)           84,000             Low              Low              Low 
(Baseline) 


Alternative 2    $6.7M/5.6M        $7.7M           -$4.4M          $13,000         $15,000            1.2%              519            43 (38%)         1,832,000           High             High             High 


Alternative 3    $3.5M/2.8M        $4.9M           -$1.6M           $9,500          $13,000           0.9%              376            60 (14%)          668,000          Medium          Medium         Medium 







Page 4 of 4