Peter Alspach

Peter Alspach

Principal / Director of Design Performance, NBBJ
A creative multi-disciplinary engineer and building physicist with over 20 years of experience delivering high profile and complex projects around the world, Peter’s work merges technical and sustainable design with applied research and data to create healthier spaces for people, communities and the planet.

To Reduce Disease and Fight Climate Change, Design Buildings that Breathe

Healthy air quality in buildings improves cognitive function and combats the spread of disease, but its implications for carbon reduction are perhaps the most important benefit.

May 10, 2022

Principal / Director of Design Performance, NBBJ

The benefits of fresh air have long been tied to health and productivity. But as we continue to examine the built environment’s role in climate change, its implications for reducing a building’s carbon footprint are increasingly important. In this post, the fourth in a series about healthy buildings (the first three posts covered light, noise and access to nature), we illustrate how solutions like operable windows and breathable facade systems are key to maintaining a healthy indoor environment and reducing energy use in buildings. This post was co-authored by Peter Alspach and Eric Phillips.


Long before the pandemic, studies indicated the correlation between indoor air quality and health. Lower levels of outdoor air supply have been associated with increased sick leave among employees, while improved ventilation corresponds with higher test scores and decreased school absences among students. Covid-19 further underscores the importance of proper ventilation and air quality in preventing disease transmission since it has been shown that the virus spreads more rapidly in poorly ventilated spaces. And while natural ventilation has positive implications for health and cognition, it can also reduce a building’s carbon footprint in lieu of conventional mechanical ventilation and air-conditioning systems.

While few climates can rely completely on natural ventilation, many climates have significant periods of the year where natural ventilation is an effective and low-energy solution to providing increased ventilation rates and space conditioning. Designing for mixed-mode buildings—buildings that can operate mechanically or naturally—allows for the best of both worlds in a changing climate.

Healthy air drives performance—of people and buildings 

The air we breathe is affected by hundreds of indoor and outdoor pollutants, and the baseline for what is considered healthy air—as defined by minimum air quality standards—is below what is ideal for performance. Good indoor air quality positively affects creativity and cognition, while even minor indoor pollutants can inhibit our ability to concentrate and process information. That’s because cognitive performance increases significantly when indoor CO2 levels are lower than those that result from current ventilation standards.

Natural ventilation can provide increased levels of outside air to a space relative to code. Bringing in two to four times as much outdoor air as required by code not only increases performance and reduces the risk of viral transmission, it also decreases energy use and operational carbon emissions. For example, in a Tokyo University of Science study on the energy saving efficiency of a natural ventilation strategy in a multi-story school, researchers analyzed ventilation and cooling load reductions based on the opening and closing of several windows. The results showed that the natural ventilation strategy could effectively establish required indoor conditions and compared with the mechanical ventilation system, could decrease energy consumption by approximately 30%.

To improve ventilation by increasing air exchange rates, features like operable windows or garage doors—which open to the outside and can be used for natural ventilation or to create dynamic indoor-outdoor spaces—can be incorporated into a building’s design. Classrooms at the new lower school campus of the Westmark School in Encino, CA—which is targeting LEED Gold certification as well as International Living Future Institute Zero Carbon certification—feature oversized doors that can be opened to create regular moments of engagement with the powerful benefits of outdoor learning and reduce the need for traditional mechanical systems.

The new lower school campus at the Westmark School outside of Los Angeles incorporates hangar doors that harness energy savings as well as the benefits of nature to improve cognitive performance for its students. 


Natural ventilation increases resiliency

Natural ventilation’s benefits extend beyond reducing disease transmission and carbon emissions. It also allows our buildings to remain habitable, even under power outages and extreme weather conditions. Hospitals are now beginning to re-examine operable windows for patient rooms, even if only to be used in an emergency. And during Covid, some hospitals were able to use operable windows to allow for retrofits of increased isolation and higher ventilation rates.

The Dumfries and Galloway Royal Infirmary in Scotland features high-performance operable windows that help maintain a comfortable, energy-efficient internal climate and enable optimum natural light in patient rooms.


A breathable facade design takes the idea of resiliency even further. This envelope-first approach prioritizes energy efficiency and comfort simultaneously and enables thermal autonomy—a building’s ability to maintain its thermal environment if power is compromised. Thermal autonomy is critical during events like heat waves, when sealed environments such as high-rise multi-family residences can become dangerous, especially for elderly or otherwise compromised populations.

Thermal autonomy is also important when quantifying energy consumption, since it measures how much of the available ambient energy resources a building can harness. Currently, researchers at UC Berkeley are working to create an integrated building design process that combines the assessment of three internal air quality factors—thermal, luminous and ventilation autonomy—into a single workflow to help predict building performance.

These types of porous building solutions are not limited only to new buildings. Many pre-war buildings already feature operable windows, an added benefit when renovating or retrofitting. Building additions or portions of new constructions can also be designed to incorporate natural ventilation strategies. For example, the atrium at the Bill & Melinda Gates Foundation in Seattle, WA—which serves as the central gathering place for the campus and can accommodate up to 1,000 people—features operable windows while the connected buildings are sealed, allowing the adjacent buildings to reap the benefits of natural ventilation in a targeted biophilic space.

The operable windows in the atrium at the Bill & Melinda Gates Foundation provide thermal comfort and energy-saving benefits while enhancing connection to the outdoors.


Finally, to effectively harness the benefits of natural ventilation, it is important to focus not just on building functionality, but also building form. Designing to allow as many spaces as possible to exist in proximity to operable windows, for example, has synergies not only with ventilation but also daylight access—another highly critical aspect of human health and wellness in the indoor environment.

Avoiding pollution and increased energy use

It is important to note that while the benefits of natural ventilation are many, there is also the potential for noise and air pollution, and increased energy use that can counteract conservation efforts, if not implemented correctly.

Periods of high outdoor air pollution—wildfire smoke and pollen are the two most common issues, as well as noise pollution from construction or traffic—are a concern when relying primarily on natural ventilation. Before implementing operable windows, a local air quality risk review is critical, and some locations may wish to continuously monitor local air quality and signal building users when ambient air quality is poor. The ability to run “mixed mode” (switching back and forth between operable windows and mechanical ventilation) and having a well-designed mechanical ventilation system in place during periods of pollution is also important. For example, persistent wildfires in the areas surrounding the Westmark School often negatively impact air quality, so individual classroom spaces feature oversized doors that can open and close. When the doors are closed, students still receive the benefits of daylight and nature without breathing contaminated air. 

Increased energy use when operable windows are open can be detrimental to energy conservation—like driving a car with the heat on and the windows down—however, there are ways to incorporate operable windows while also mitigating the energy penalty. Automation or mechanization of windows or select windows within a space that serve as a signal for other manually controlled windows can help alleviate this problem. Window switches that signal open windows to maintenance staff and that can also prevent heating and cooling when the windows are open are another solution. Signaling systems like a red or green light are useful if tuned correctly and lastly, use of windows in spaces that have greater ownership—such as residences or private offices—have a lower likelihood of misuse.

NBBJ’s Seattle office features operable windows which utilize a signaling system that indicates when windows can—and should—be opened or closed.


Finally, changes in climate can also result in impacts to local air quality, increasing ground-level ozone and particulate air pollution. CO2 concentrations in outdoor air are rising and projected to increase due to continued emissions, exacerbating current challenges with high indoor CO2 levels, especially with mechanical systems where the ability to increase ventilation rates is limited. Operable windows provide a large jump in outside ventilation, which can help to maintain indoor CO2 levels, even as outdoor levels rise.

In conclusion

Because of the potential benefits, natural ventilation is increasingly being proposed as a means of saving energy and improving indoor air quality. Design solutions like operable windows and breathable facades that can be applied on a variety of building types and scales improve air quality and reduce carbon emissions in buildings while providing added benefits for the health, performance and safety of the people who occupy them.

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Getting to Zero

Rethinking Carbon in the Built Environment

December 17, 2021

Principal / Director of Design Performance, NBBJ

Editor’s Note: As we work with our clients to improve the health of people and the planet, addressing carbon emissions from the built environment is imperative. In this series, we focus on the ethics and economics of carbon-based decision-making, as well as actionable steps to reduce both embodied and operational carbon.

This post was co-authored by Peter Alspach, Margaret Montgomery and Megha Sinha


It goes without saying that the conversation around climate change dominates news headlines. Seemingly every day, we read about extreme weather events, rising energy prices and dwindling resources. This year alone, the US has experienced eighteen separate extreme weather disasters costing up to $1 billion each.

Ethically, carbon-based decision-making is imperative. Six of the top 10 greenhouse gas emitters are developing countries, and the US and Canada emit more than double the global average per capita. The least developed countries emit the least carbon dioxide, but the effects of climate change are felt most strongly by these nations. And globally, climate change disproportionately impacts women and communities of color. For example, weather events fall harder on disadvantaged communities, who generally have fewer resources and take much longer to regain equilibrium.

So, how does the built environment come into play? According to a 2019 report by the World Green Building Council, the building and construction industries together are responsible for 39 percent of all carbon emissions in the world. Moreover, according to UN Habitat, cities consume 78 percent of the world’s energy and produce more than 60 percent of greenhouse gas emissions–yet they account for less than 2 percent of the Earth’s surface. The conversation about how to get to zero-carbon can feel daunting, but we believe that creative and world-changing solutions are within our reach. In this series, we will discuss the main considerations to achieve zero-carbon in our cities and the built environment, with the goal of counteracting the building industry’s growing impact on climate change.

Beyond the Building Footprint
The scale of the challenge at hand necessitates that zero-carbon thinking start well before the building footprint—at urban, district and campus scales. It is at this scale that critical carbon reduction strategies and policies as they relate to energy infrastructure, transportation, land use, urban tree canopy preservation, existing and new building construction, and public-private partnerships must be made to create meaningful and long-lasting change.

Cities are leaders in the climate change movement in large part because city government—and mayors in particular—are more directly connected to their constituency than state or federal legislators. They also hold the majority of carbon emissions for most of their locations, and they have the authority to move more quickly than state, federal or national government.

For example, the City of Boston has introduced the Carbon Free Boston initiative, a comprehensive plan to become carbon neutral by 2050 by putting strategies in place to cut emissions from cars and buildings. Likewise, Denver recently became the eighth US jurisdiction to pass a building performance standard, and Seattle’s Mayor Durkan issued a Climate Executive Order during the COP26 Summit to accelerate efforts toward net-zero emission buildings.

Applying carbon-reduction strategies at the city level is important in mitigating the built environment’s carbon footprint. Tencent’s Net City, in China, prioritizes people and the environment, rather than automobiles, for a healthier experience.


A Shift in Thinking
Zero-carbon buildings require a shift in thinking at the onset to meet the aggressive targets we need to achieve by 2030. Where a project is located, its height, massing, materiality and whether it needs to be built at all are considerations that can affect a building’s contribution to carbon emissions. On a recent high-rise office tower, our design team made the early decision to incorporate a steel, below-grade parking structure when concrete would be more conventional path. As a result of these and other design decisions, this project has a projected embodied carbon 10% below the ILFI Zero Carbon threshold of 500 kg/m2.

In addition, a project’s location touches issues from preservation of the natural environment to equity and accessibility. For example, building in an urban area accessible via low-carbon public transportation as opposed to a suburban or rural area where the automobile dominates affects emissions—and employee and community well-being. A client recently considered relocating a new headquarters from downtown to a suburban site and found that it would be detrimental to many of their employees who depended on local transit for commuting. Instead, they chose a site where transit access was more available.

Planning around low-carbon public transportation options such as subways or designated bike lanes not only impacts emissions, but also touches issues such as equity and accessibility.  Amazon’s Seattle HQ features a two-way cycle track and a dedicated entrance for bicycle commuters, promoting health and ease of access.  


The Economics and Benefits of Integrated Thinking
The best approach to carbon-based decision-making is through integrated thinking early in the process. Often, we can leverage one design strategy to achieve multiple goals and amplify value. While sustainability measures may appear costly at a project’s onset, the overall energy savings throughout the lifecycle of the project are exponential. Integrated thinking at the onset enables successful zero-carbon buildings by avoiding the layering of costs further down the road. Embracing carbon-based decision-making as an economic opportunity allows us to build the building of 2050, today. Future retrofitting for sustainability requirements will be more costly, not to mention more environmentally damaging, than an up-front investment.

In addition, the costs associated with many sustainable solutions are changing rapidly, with solar and wind power now tracking lower in price for the grid than coal or gas power plants. Employing long-term thinking that recognizes the cost of energy over a building’s lifetime pays back in dividends. In Boston, the BERDO 2.0 city ordinance dictates that buildings over 35,000 square feet or those that have 35 units or more report their energy and water use to the City of Boston every year. Those buildings not meeting the city’s emissions standards must then pay a fee on any overages. And in Southern California, our team recently designed a net-zero energy hospital where the cost of on-site solar power was less than half ($0.05/kWh) of the typical utility rate, not counting demand reduction benefits.

Creative and innovative solutions to reduce the building industry’s carbon footprint are within our reach. Microsoft’s corporate campus expansion taps geothermal wells 550 feet underground to provide power and achieve the company’s goal of becoming carbon negative by 2030.


Now that we are aware of the implications of our decisions regarding climate change and carbon emissions, we are ethically bound to act responsibly. In the words of UNESCO in an article on the ethical principles of climate change, “Adapting to climate change and trying to mitigate its impacts are not just a matter of scientific knowledge and political will; it demands a broader view of a complex situation.”

In the next installment of our series on carbon-neutral buildings, we dig deeper into the subject of embodied carbon and the urgency of addressing it for the architecture, engineering and construction industry.

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Thriving, Not Just Surviving: Solving the Climate Crisis

A Visit to the 2019 UN Climate Action Summit

October 4, 2019

Principal / Director of Design Performance, NBBJ

I had the privilege of joining the 2019 UN Climate Action Summit in New York City earlier this fall. Amongst the many tracks at the event, my focus was on Infrastructure, Cities, and Local Action — how to bring climate solutions to bear in cities that are on the front lines of emissions, impact and action. As the creators of cities and the urban context, our profession plays an integral part of any climate crisis solution and must be actively involved in driving the world forward.

My key take-away from the summit is the broader societal success that will result when our cities transform into zero-carbon economies. Zero-carbon cities will be healthier, cleaner, more connected, more resilient, and the drivers of innovation and green economic success. They will be the places where you want your children and grandchildren to live. It’s hard to argue against that.

It is of utmost importance for the design industry to elevate the discussion around these greater societal benefits, especially in these times of disagreement over the urgency of the climate crisis. Focusing on the non-climatic benefits can drive greater change while we reap the environmental benefits. There are stories and threads for every audience — be it economic growth, resilience and security, human health, ecosystem restoration or social justice.

What can we do, as city designers, in a context where, as Ms. Maimunah Mohd Sharif, executive director of the United Nations Human Settlements Programme, said at the summit, 75% of the 2050 infrastructure has yet to be built? Here are a few ideas:

  • Bring long-term thinking to our projects. All our current buildings will be around in 2050 — are they able to make the transition and meet the 2050 goals for zero carbon?
  • Utilize full-cost, life-cycle accounting in our decision-making, bringing in the cost of carbon and societal impacts and evaluating them from construction to decommissioning.
  • Focus on the human experience — zero carbon means little if our projects aren’t wonderful places for people.
  • Focus discussions around non-carbon benefits to build stakeholder support.
  • Don’t look for a “new tech silver bullet” — the solutions we need, from heat pumps to solar and wind energy, are here, now.
  • Lead from within.*

While getting to zero carbon by 2050 is a daunting task, it is achievable. We see tremendous growth in action and commitment across the public and private sector — whether it’s Amazon’s recent Climate Pledge, New York City’s buildings’ carbon emissions law or the consortium success of the C40 Cities Initiative.

I’m bullish about our capabilities and the passion and talent across the AEC industry and beyond. Together, we can drive this exponential curve to zero carbon and enjoy a beautiful and healthy future in our cities — cities that will house 5 billion of us by 2050.

“Getting there [to zero carbon cities] will be the growth story of the 21st century.”
—Lord Nicholas Stern, London School of Economics


* Here are a few of the things NBBJ is doing:

  • More than a decade of commitment to the Architecture 2030 Challenge
  • Leaders who are active in their communities, from driving local code changes to serving on national and international boards and committees, including the Living Futures Institute, the AIA’s Energy Leadership Group and ASHRAE
  • Founding sponsorship of and membership in Targeting 100! with the University of Washington
  • Our Legacy Project in partnership with the Nature Conservancy


Banner image courtesy of Pixabay.

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