Inside America's Passive House Library

Mount Vernon Library Commons redefines sustainable public design though Passive House certification and advanced ventilation with Geniox DOA systems

Mount Vernon Library Commons

The Mount Vernon Library Commons is a groundbreaking example of sustainable public infrastructure.

Certified to PHIUS+ 2018 standards, this 120,000+ ft² facility combines energy efficiency, community engagement, and advanced ventilation solutions.

Key to its success is a semi-centralized ventilation system powered by Systemair’s Geniox air handling units, delivering balanced airflow, MERV 13 filtration, and energy recovery for optimal indoor air quality.

Complemented by thermal, radiation, and moisture control strategies, the building offers a healthier, more resilient environment while reducing operational costs and setting a new benchmark for PHIUS-certified public projects.

130,000 kWh

Solar Power Generation

The building produces over 130,000 kWh annually, supplying approximately 19–21% of the building's power needs (without EVs = +/- 45%).

A Landmark for Sustainability

The Mount Vernon Library Commons is the largest public project in the city’s history, built to PHIUS+ 2018 standards and certified in July 2025.

Its design reflects a commitment to energy efficiency and community engagement.

Community-Centered Design

Beyond books, the library offers EV charging, meeting rooms, and a commercial-grade kitchen, creating an environment for learning, collaboration, and resilience during extreme weather events.

2025 Phius Award for Public Space Excellence

Led by Julie Blazek of HKP Architects, this project won the award for Public Space Excellence at the 2025 Phius Passive Projects Design Competition.

: Americas
: 2025
Architect: HKP Architects
Mechanical Systems Designer: FSI Engineers
PHIUS Certified Verifier: Tom Balderston
Builder: Lydig Construction
QA/QC: Balderston Associates/Tom Balderston
Owner/Developer: City of Mount Vernon

Introduction

Located in downtown, the Mount Vernon Library Commons sits on the corner of 2nd and Kincaid, welcoming people right off Interstate 5. The building is the result of a $61 million investment in the local economy. As you approach from I5, bright LED lights spell the words 'Commons', next to wonderfully accentuated wood and glass paneling. Approaching from the east will reveal picturesque stained-glass windows with clear trees over the expanse of the facade. The appearance reflects its purpose: the two-story building looks sustainable because it is.

The library was built to the Passive House Institute of the United States (PHIUS) standards and certified to PHIUS+ 2018 (now the equivalent of PHIUS CORE) in July 2025. The library functions as more than just a place to check out fascinating reads.

Overall, the library is a home to community involvement. The building offers public library services, off-street parking with EV charging stations, a community center with meeting rooms open to all, and a commercial-grade kitchen where residents can learn, teach, and share meals together.

Most public service buildings enable public servants to provide valuable, non-quantifiable services to their community. The local operational budget can make it difficult to sustain or justify some of these services to taxpayers.

Justifying the high energy usage of a 120,000+ ft² building may be one such difficulty. Still, the true value of public infrastructure lies not in what can be quantified, but in the lasting impact it has on the people it serves.

According to the International Energy Agency (IEA), buildings account for 30% of the global final energy consumption and contribute 26% of global emissions. What's more, because of transmission, delivery, and production losses, energy consumption can be up to 3 times more than the actual energy used at the site. ENERGY STAR® data shows that the average U.S. library has a site and source energy use intensity (EUI) of 71.6 and 143.6, respectively. In contrast, the Mount Vernon Library Commons is 20% more efficient when compared to the modeled standards.

Energy Consumption Comparison

Metric	Units	Modeled Standard	Mount Vernon Library
Site EUI	kBTU/ft²	71.6	14.89
Source EUI	kBTU/ft²	143.6	41.68

EUI comparison between a modeled standard library and the Mount Vernon Library Commons.

Putting this table into perspective, compared to a standard new office building, this library's site EUI is 20% more efficient and the source EUI is 29% more efficient, saving taxpayers' money and optimizing the energy-efficiency of the building.

One of the most remarkable features of the Mount Vernon Library Commons is its ability to generate clean energy. The library generates over 130,000 kWh/yr.

This clean energy supplies almost 21% of the building's power needs, making the library’s immense public value even easier to justify.

PHIUS Principles

Achieving these levels of energy efficiency, and eventually energy generation, is built on PHIUS principles. These 4 core principles include:

Thermal Control

Air Control

Radiation Control

Moisture Control

These principles create more than just an energy-efficient building, they take it another step further to create a holistically, comfortable indoor space.

Thermal Control

Creating a stable indoor environment requires separating the outdoor environment from the indoor environment. This concept is known as "thermal control". When implemented correctly, this design method maximizes comfort and energy efficiency by regulating temperatures year-round. This concept is put into practice by creating a high-performance enclosure and eliminating thermal bridges.

Christine Baldwin of HKP Architects described the indoor library space in 2023 as "This building is being designed to be passive house certified. That means it will be surrounded by a tight, exterior envelope that allows to heat the building less and cool the building less in the summer months."

Christine continued, "In times of wildfires, there will be less smoke that is brought into the indoor spaces of the library, making sure the interior space is more comfortable for the occupants, such as the library patrons."

Air Control

Achieving an airtight exterior envelope requires air-sealing the enclosure to minimize infiltration of outside and loss of conditioned air. However, this creates a ventilation issue as there is limited natural air exchange.

Balanced ventilation with either heat or energy recovery solves this problem. Creating dedicated outdoor openings encourages intentional air movement that is comfortable and efficient.

For this project, Phius certification required a minimum of 0.6 Air Changes per Hour (ACH). On their blower door test, the team met this goal by achieving 0.055 ACH—4x better than Washington State code required.

Balanced Ventilation

For balanced ventilation, the construction team decided to use a semi-centralized ventilation system; one to ventilate the library and the other to ventilate the community center. In this system, a single mechanical unit - typically a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV) - serves an entire floor. Therefore, this design required an air handling unit (AHU) for each floor of the library. FSI Engineers selected Systemair’s Geniox AHUs to meet the building’s performance goals.

Now, these AHUs supply filtered air through a MERV 13 filter and condition it with a hot water coil. They pull air from areas like bathrooms and cooking areas to remove toxic, volatile organic compounds (VOCs) from the premises. Air is then replaced with the filtered and conditioned air supply through the energy recovery wheel, aiding in comfort and improving the indoor air quality (IAQ).

Kitchen Ventilation: Makeup Air

The commercial grade kitchen also required ventilation. Exhaust ventilation is handled by a 3,570 CFM centrifugal fan. With this much air going out, Washington State Mechanical Code requires makeup air to be reintroduced at a similar rate to the exhaust air rate. Again, FSI Engineers chose Geniox to supply fresh, conditioned air, ensuring the space remains safe, efficient, and comfortable for all.

Radiation Control

HKP architects designed the library to take advantage of solar radiation and prevent overheating. Implementation of high-performance glazing techniques help optimize cooling loads, such as installing windows (double- or triple-paned) and doors with proper solar heat gain plus appropriate shading strategies. Daylighting uses the sun's energy in the heating season to reduce heating loads and helps reduce lighting loads by incorporating natural light to improve the indoor environmental quality (IEQ).

Moisture Control

Maintaining the correct humidity level throughout an airtight space requires proper vapor and moisture control design, and selecting the correct type of mechanical systems. When prioritized, the indoor space feels more comfortable and building materials lasts longer.

FSI used Systemair Geniox air handling units to provide DOA. The design, installation, and early use of these units has been seamless. The energy recovery wheel provided exemplary performance to support our design in achieving PHIUS Certification. If and when I have the chance, I will use these units again on any project.
Ola Jarvegren
Principal, FSI Engineers

Conclusion

Building a library of this magnitude to PHIUS standards is an incredible achievement. Many construction firms and public bodies came together to build the largest project in Mount Vernon's history.

"Passive House Certification makes this building 75% more energy-efficient than code buildings, which will save taxpayers year-over-year in operational costs. It also makes this building healthier, more comfortable, and available for shelter in extreme temperature events," said Julie Blazek, partner at HKP Architects.

"[The Mount Vernon Library] is the first publicly bid building of its kind in the [United States]." Looking forward, Julie expects visitors from all over the United States, "There are so many incredible sustainable features that this project will be a destination for other architects, engineers, builders, students and interested public people to come and tour."

Former transportation secretary Pete Buttigieg, from a May 2024 press release, had this to say, "Having a library, public restrooms, a community center, and a kitchen all under one roof — and only steps away from Skagit Station — will be a game-changer for the people of Mount Vernon."

The Mount Vernon Library Commons is a model for sustainable library design and public infrastructure.

By integrating Passive House principles into every aspect of its design, from thermal insulation to advanced ventilation systems, the library achieves exceptional energy performance while enhancing occupant comfort and community resilience.

The use of semi-centralized ventilation, energy recovery, and high-efficiency air handling units ensures that indoor air remains clean, conditioned, and safe—even during wildfire events or heavy kitchen use.

As a PHIUS-certified building, it not only reduces operational costs but also sets a precedent for future public projects.

Geniox

Geniox offers ideal energy saving and low operational cost, with a long lifetime and the least impact on the environment.