Party Walls

Choosing Insulation for Carbon Value – Why More is Not Always Better Part 2

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.


The Making of the 2021 International Energy Conservation Code (IECC)

When I first started working at Steven Winter Associates, I didn’t know that one day I’d find myself involved in the development of codes and standards that impact how our buildings get built. I certainly don’t consider myself an expert, but I have learned a few things the hard way and thought they’d be worth sharing if you might be new to it.

So, here’s my very high-level summary of the code development process with respect to the 2021 International Energy Conservation Code (IECC), aka the “model” energy code. If you are looking for more detail, the ICC webpage has plenty of resources and a more detailed infographic than the one we’re showing and discussing here.

IECC Code Development Process Chart


Call to Action: Voting Open Until December 6th on the Changes Proposed to the 2021 IECC

ICYMI: The code change proposals for the 2021 IECC are open for voting by Governmental Member Voting Representatives (GMVR) from Monday, November 18th through Friday, December 6th, and your vote is instrumental in making buildings consume less energy! [Need a quick refresher on the code process? Check out our blog post here!]

Does your vote even matter?

Overall, there are not actually that many voters on a given proposal. In the energy proposals, last cycle, it ranged from about 200-400 voters per proposal, even though there were a total of 1,247 voters on the Group B codes, which includes the IECC.

IECC voting numbers

So a small handful of voters can entirely shape the future of the energy codes that dictate how energy efficient our buildings will be! If history repeats itself, while some online voters tend to align with the Committee, many online voters align their votes with those cast by their fellow ICC voters at the Public Comment Hearings. This happened 81% of the time in 2016. Unlike 2016, in this cycle all the electronic votes cast during the Public Comment Hearings will be rolled into the online vote tally (although those voters can still change their vote).


Whole Building Blower Door Testing – Big Buildings Passing the Test

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.

Image of SWA staff setting up blower door test

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


Choosing Insulation for Carbon Value – Why More is Not Always Better Part 1

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)


Foundation Waterproofing 101

Foundation Waterproofing Cutaway

Credit: Basement Waterproofing Baltimore (2018, February 20).

Designing buildings with water protection in mind is critical to protecting buildings from future damage, difficult/costly repairs, and potential litigation. Foundations are by necessity in the ground. So is water. Foundation waterproofing is intended to keep them separate, by providing a layer of protection between a below-grade structure and the moisture present in the surrounding soil and fill. Waterproofing is especially important when the foundation lies below the water table or in a flood zone. Read on to learn about different approaches and materials used to waterproof foundation walls and slabs and specific detailing needed to provide a watertight enclosure. And, check out Part 2 of this series for specific guidance and examples to achieve a watertight enclosure.

Why is foundation waterproofing necessary?

Did you know? Water intrusion makes up more than 70% of construction litigation.Water

Foundations are basically holes in the ground that want to fill with water. Poor site drainage, through-wall penetrations, concrete cracking/mortar joints and movement, door/window/vent openings, flooding, high water tables, hydrostatic pressure – all contribute to the propensity for water to fill the subterranean void we have established. Foundation leaks are difficult and costly to rectify, not to mention designer/contractor financial liability. Water in a basement is water in a building. Excess moisture within a building is a recipe for higher RH and increases the potential for condensation, and mold and other allergens.

Luckily, foundation water intrusion is usually preventable. The goal is to identify all the potential water transport mechanisms, and address them, through good design practices, proper detailing, and quality execution. (more…)

Reducing Air Leaks in Multifamily Buildings (and why you should care)

If there was ever a silver bullet when it comes to best practices in multifamily buildings, air sealing would be it. Compartmentalization – or air sealing each unit to prevent infiltration between units and to the exterior – addresses many major issues we see in buildings.


  • Air sealing is the best strategy to keep pests out and limit their movement within a building.
  • Air carries a lot of moisture, so eliminating air leaks helps keep buildings dry and reduces the risks of mold and water damage.
  • Compartmentalization prevents contaminated air from garages, basements, attics, and other undesirable sources from entering living spaces.

Improves COMFORT

  • Air sealing reduces drafts and eliminates hot and cold spots.
  • Limiting air transfer from one unit to the next reduces transmission of noise, smoke, and odor between units.

Wastes less ENERGY

  • Air sealing lowers heating and cooling bills maintaining a more consistent indoor temperature.
  • Compartmentalization improves the performance of ventilation and mechanical systems by limiting pathways for stack effect – the force of warm air from low to high – to occur in larger buildings.

How to Air Seal Multifamily Units

It’s important to remember to create a complete air barrier around the entire cube of a multifamily unit, not just to the exterior – any and all penetrations need to be sealed.


2016 New York Energy Code Blower Door Testing – How Does it Measure Up?

Written by Sunitha Sarveswaran, Energy Engineer

Welcome to part three of the air sealing blog post series! In previous posts, we have reviewed the substantive changes in 2016 New York Residential and Commercial Energy Code, focusing specifically on the new blower door testing requirements. In this blog post, we’ll examine how these requirements stack up in comparison to green building certifications that we are already familiar with: LEED for Homes, LEED BD+C, ENERGY STAR® Certified Homes, ENERGY STAR® Multifamily High-Rise (ES MFHR) and Passive House (PH).

To make this easier to digest, we’ve divided this comparison into two parts – compartmentalization and building envelope. If you need a refresher on the difference between these two types of blower door tests, we recommend referring to the article “Testing Air Leakage in Multifamily Buildings” by SWA alumnus Sean Maxwell.


Oh, the Weather Inside is Frightful!

Winter in the City

Wintertime in New York City: cold wind whips down the avenue and seems to follow you as you leave the frozen street and enter your building. The cold gust pulls the heat out of the lobby and even seems to follow you as you make your way up the building, whistling through the elevator shaft as it goes. The colder it gets outside, the worse it gets inside. Can’t somebody please make it stop? Is it too much to ask to be comfortable in your own lobby?

No, it is not too much to ask, and yes, we can help. It is 2016 and we have the technologies and expertise to better manage this all-too-common problem, but first we must examine what forces lay at the heart of the issue.