Party Walls

“Net zero” can mean a lot of different things depending on what you choose to measure – zero energy usage, zero carbon emitted, zero lifecycle impact, etc.

At Steven Winter Associates, Inc. (SWA), we work with clients who are approaching net zero from different angles: driven by institutional goals, climate concerns, marketing campaigns, and connecting with municipal emissions targets. One thing we see over and over is that super high performance is difficult to achieve, but with a key simplification – there are not many ways to do it. All roads may lead to Rome but the closer you get, the fewer roads there are to take.

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In Part 1 of this blog post, we highlighted two of the most commonly used insulations in the U.S.– XPS board and closed-cell polyurethane spray foam – and noted that they are produced with blowing agents (HFC-based) that are putting more carbon into the air during construction than they save during building operation for many decades. We left you with a question: if we don’t use these insulations, how can we make up for the loss of the helpful qualities that has made us dependent on them?

Insulation Alternatives

One part of the answer comes from the development of new materials. In Europe over the last decade, Honeywell developed a new blowing agent, a hydro-fluoro olefin (HFO), which claims a global warming potential (GWP) of less than one, which is less than that of carbon dioxide.  First in Europe, and now in the U.S., manufacturers such as Demilec and Carlisle are coming to market with a closed-cell polyurethane spray foam that uses this blowing agent instead of the HFCs that carry a GWP of well over 1,000. These spray foams have a slightly better R-value  than their high-carbon predecessors, and otherwise have the same qualities that make them useful in multiple contexts – air/vapor barrier capability, conformance to irregularities and penetrations, etc.  However, they also have many of the same downsides – high flammability, potential (and not completely understood) off-gassing post-application, and the basic fact that they are petroleum products.

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It is clear to see that the Passive House (PH) standard is here to stay! Across North America, more States, Provinces, and Municipalities are integrating PH into their building standards. One of the more recent adopters is the City of Toronto. In the most recent version of the Toronto Green Standard (TGS), the PH standard is offered as an alternative compliance path to TGS Tier 3, and with this alternative compliance path one obvious question comes to mind: What is the major difference in required component efficiency for a multifamily building in Toronto that is looking to meet either the PH standard or TGS Tier 3?

The PH standard is performance-based and is focused on decreasing whole building energy demand, improving building durability, providing optimal occupant thermal comfort, improving indoor air quality, and reducing carbon emissions. The PH standard reduces building operation costs, decreases carbon emissions, and supports an improved indoor environmental quality for building occupants. The TGS has similar goals and benefits when compared to the PH standard, and there are some obvious synergies in the program design between TGS and PH. The tiered energy category in the TGS takes a similar approach to PH by offering an annual budget for three different categories. For PH you must comply with a total energy budget for annual heating demand, annual cooling demand, and total source energy use intensity. Similarly, but slightly differently, the TGS offers a budget for total site energy use intensity (TEUI), annual heating demand or Thermal Energy Demand Intensity (TEDI), and the additional category of Greenhouse Gas Intensity (GHGI). In both standards, the path to compliance is non-prescriptive and designers can implement a variety of component efficiencies and system options. See table 1 and 2 below:

Table 1: Passive House Standard Criteria

Table 2: Toronto Green Standard Tier 3 Criteria

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As members of the HERS Rating community, we are very excited about the recent study conducted by Freddie Mac determining that homes rated under RESNET’s Home Energy Rating System (HERS) between 2013 and 2017 sold for an average of 2.7% more than comparable unrated homes.

Using a national random sample, the property value analysis found that better-rated homes are sold for 3 – 5% more than lesser-rated homes. In this case the “better” rating means a higher energy efficiency rating. It’s unclear from the study if this means a home with an average HERS rating, such as HERS 55 in the Northeast, could be valued at 2.7% more than the unrated home. And perhaps one approaching Zero Energy, such as HERS 10, could be valued at 5% more than the lower-rated home. I could be doing some very creative math here, but doesn’t that imply that the better rated home might just be valued about 7.7% more than the unrated home?

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Between gift shopping and trying to keep up the holiday spirit with decorations at home, it can be frustrating to try to remain sustainable. It may feel as though you’re forced to choose between enjoying the holidays and feeling guilty about putting up all those lights around your tree.

Here are 10 ways you can have a festive holiday and feel better about it too:

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The residential energy efficiency industry has been using blower door testing since the mid 1980’s to measure the air tightness of homes. Since then, we’ve evolved from testing single family homes, to testing entire apartment buildings. The Passive House standard requires whole-building testing, as will many local energy codes, along with assembly testing. While the concept of – taking a powerful fan, temporarily mounting it into the door frame of a building, and either pulling air out (depressurize) or pushing air into it (pressurize) – is the same for buildings both large and small, the execution is quite different for the latter.

Commonly called a whole-building blower door test, we use multiple blower doors to create a pressure difference on the exterior surfaces of the entire building. The amount of air moving through the fans is recorded in cubic feet per minute (CFM) along with the pressure difference from inside to out in pascals. Since the amount of air moving through the fans is equal to the amount of air moving through the gaps, cracks, and holes of the building’s enclosure, it is used to determine the buildings air tightness. Taking additional measurements at various pressure differences increases the measurement accuracy and is required in standards that govern infiltration testing. Larger buildings usually test at a higher-pressure difference and express the leakage rate as cubic feet per minute at 75 pascals or CFM75.

SWA staff at a project site setting up a blower door test

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As part of the Climate Mobilization Act, and in accordance with the its greater carbon emissions reduction goals, New York City passed Local Laws 92 and 94 in April 2019, mandating the installation of rooftop solar photovoltaic systems and/or green roofs on buildings across the city. The new requirements will go into effect on November 15, 2019 and will apply to all new buildings and any existing buildings completing a full roof deck or assembly replacement.

The Mayor’s Office estimates that the solar and green roof installations mandated by these bills will result in 300 MW of new solar capacity, 15 million gallons of new stormwater management capacity, 1 million tons of greenhouse gas reductions, and hundreds of green jobs. Based on these projections, this will account for close to 2.5% of the city’s overall emissions reduction goals.*

The laws require that solar and/or a green roof be installed on all available roof space. Areas deemed “not available” and excluded from the requirements include:

• Areas obstructed by rooftop structures, mechanical equipment, towers, parapets, guardrails, solar thermal systems, cisterns, etc.;
• Fire access pathways and zoning setbacks;
• Recreational spaces that are recorded in the Certificate of Occupancy.

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In a world where everything seems to be packaged in two layers of plastic, where we are encouraged to constantly discard items to make room for new ones, and where social media drives our desire to consume the newest trends, it can seem impossible to reduce our waste. Living a zero-waste lifestyle seems almost too overwhelming. I find myself wondering, “How can I possibly reduce waste when industries target consumers to do the opposite?” and “Even if I do make changes in my own habits, is it enough to make a difference?”

I struggle with the same paralyzing vastness that Jonathan Chapman mentions throughout his book Emotionally Durable Design. Paralyzing vastness describes the tendency to do nothing when a task seems too large to conquer, instead of taking smaller steps. In the past, the seemingly vast nature of zero-waste living discouraged me from doing anything beyond entry-level recycling, but I realized that minimizing my waste is something worth tackling. Therefore, I will be sharing some ideas for working towards a zero(ish)-waste lifestyle — because going from zero to one hundred, or in this case one hundred to zero can be scary — and I’ll include my experience implementing a few of the ideas myself.

WEEK ONE: Apartment Composting

In blogs and articles that speak on behalf of zero-waste living, the importance of sharing with others and asking for help getting started is most frequently emphasized. For example, my apartment complex does not offer any composting services, but the SWA office does (yay sharing!). For week one, I started composting and designated two small resealable containers — one for food waste, and another for paper towels — that are now living on my kitchen counter. I intended on utilizing these two bins throughout the week, and then bringing them to the office for a dump. If you have the ability to start your own compost bin, that’s great too.

While using paper towels throughout the week, I felt less bad about it knowing that they wouldn’t be going into the landfill, but I developed some questions: If I use the paper towel with cleaning supplies, can it be composted?… Is it worth collecting small bits of food waste when I could just eviscerate them in the garbage disposal?… Are garbage disposals bad for the environment and/or do they affect the energy utilized for wastewater treatment?

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SWA’s Enclosure Group is acutely aware that insulation is the most important single material choice to maximize the enclosure’s thermal resistance over its operational life. Many of us in the building industry believe that, combined with a good continuous air seal, the highest insulation value makes the greenest enclosure, helping to reduce a structure’s carbon footprint and combat climate change. It may come as a surprise, then, that some of the most commonly used insulation materials are so carbon-heavy to manufacture and/or install, that for many decades they wipe away the carbon-energy savings they are supposed to provide.  The following is a detailed discussion of how and why this is, and what the industry is doing to change the equation.

Embodied vs. Operational Carbon

The built environment looms large in the climate picture, because almost 40% of the total carbon put into the planet’s atmosphere each year is attributed to buildings. Over the past 30 years of green building, we have overwhelmingly focused on operational carbon – the carbon that buildings emit as they are being used. Only recently have we begun to focus on embodied carbon – the carbon that goes into constructing buildings, which is typically far greater than the energy saved in the first decades of operation. Changes in energy codes are aimed at operational carbon, and even those organizations and standards that have been at the forefront of promoting sustainable building [LEED, PH] have not been quantifying or limiting embodied carbon, although they bring attention to it.

The Time Value of Carbon

Assuming that a building stands for many decades, or even centuries, its operational carbon will eclipse its embodied carbon over its lifetime, and therefore when the building’s carbon Life Cycle Assessment (LCA) is calculated, operational carbon savings will be more important than embodied carbon saved/spent in the long run. Why does embodied carbon deserve equal weight with operational carbon? Because of the total global carbon emissions from buildings, 28% is pegged to embodied carbon. That’s already a large percentage, but when you consider the near term, the first 30 years of a building’s life, the percentage jumps to about 50%. In effect, every new building is in carbon debt upon completion due to the huge amount of carbon emitted  in order to construct it., And in order for the climate to benefit from the energy savings provided by a well-insulated and sealed enclosure and a high efficiency energy system, the building needs to last and be used for a very long time. The problem is that we may not have 30 years, let alone 60, to pay off that carbon debt.

In the first 30 years of a building’s operational life, 50% of its total carbon emissions are still due to embodied carbon (Source: Architecture 2030)

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Before you can really dig deep into the advanced design concepts of embodied carbon analysis and whole building energy modeling, you must first perform some bare minimum prep work. An easy way to get the pre-schematic plan up on its legs quickly is to add qualitative performance measures to the architect’s program study or create an Owners Project Requirements (OPR) document. For this article, “qualitative performance measures” refer to the metrics that express embodied carbon, but can also include operational energy, water, and even healthy materials.

An integrated design process (IDP) anchors the architectural program to performance metrics such as carbon dioxide equivalents (CO²e), Energy Use Intensity (EUI), and zero Energy Performance Index (zEPI). So, by completing the IDP, you’re getting the basic tools to optimize embodied carbon and operational energy use in your design:

1. Target the early phase of the project
2. Prepare a Carbon Hotspot and Simple Box energy analysis to compare carbon sensitivity of different schemes not limited to wall and roof construction, massing, and solar exposure.
3. Schedule a workshop with the design team and owner to discuss findings and recommendations.
4. Establish performance targets such as total Carbon Dioxide equivalents as a basic program requirement.
5. Choose a compliance pathway and verify design with Life Cycle Analysis and a Whole Building Energy model.

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