Party Walls

Did you know that there are two pathways for earning Passive House certification? There’s Passive House International (PHI) and Passive House Institute US (PHIUS). Using an energy modeling software, both programs evaluate a building based on a variety of factors. Despite the misleading moniker, certification is not limited to just housing. In fact, building types from residential and commercial high-rises to industrial factories have earned Passive House certification around the globe. However, the two certification programs are run by separate institutions, using different energy modeling software and standards. However, both ultimately maintain the shared goal for high performance, low energy buildings.

Historically, around 2013, the PHIUS organization developed a new standard called PHIUS+ 2015 with a climate-specific approach and an alternate modeling software. Starting in March 2019, PHIUS projects will be held to updated requirements under the PHIUS+ 2018 program.

PHI also offers project and climate specific cooling demand thresholds, having previously begun offering alternate certification options in 2015. Additionally, PHI created a program called EnerPHit to provide more flexibility for retrofits. PHI recognizes buildings that exceed its standard certification by offering Plus and Premium certification, as well as a Low Energy Building certification pathway for projects that are near PH efficiency.

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*click here to read Part 1 of this blog

In climates with significant heating and/or cooling seasons, Passive House projects must have a balanced heat or energy recovery ventilation system. These systems use a heat exchanger to transfer heat and moisture between the outgoing return and incoming outdoor airstreams. The operation of recovery ventilators reduces the energy required to heat and cool decreasing the building’s carbon footprint. Project teams can select either:

• Heat Recovery Ventilators (HRV) that transfer heat from the return air stream to the outside air stream; or,
• Energy Recovery Ventilators (ERV) that transfer heat and moisture from the return air stream to the outside air stream.

Deciding between an HRV and an ERV gets more complex when the Passive House concept is scaled from a single-family home to a multifamily program. What the industry has learned from the development of airtight buildings and programs such as Passive House and R2000, is that indoor relative humidity must be controlled through continuous ventilation. The extremely air tight building envelope required of a Passive House, combined with high internal moisture gains from an occupant dense multifamily program (coming from occupants, kitchens and bathrooms), forces additional moisture management considerations during mechanical ventilation design. Maintaining acceptable interior relative humidity in both the heating and cooling season is paramount for building durability and occupant comfort. It’s appropriate that Passive House professionals claim this simple motto: “Build tight, ventilate right!”

In New York City where the multifamily Passive House market is rapidly growing, there is a significant heating season and a demanding cooling season with high humidity (Climate Zone 4A). With this seasonal variation, there are four primary operating scenarios for an HRV or ERV that need to be considered during design:

Summer Condition – HRV

An HRV operating in the summer (hot-humid exterior air and cool-dry interior air) introduces additional moisture to the building through ventilation. Heat is transferred from the incoming outside airstream to the return airstream leaving the building which cools supply air, but exterior moisture is not removed from the incoming air. The building’s dehumidification load increases as a consequence of additional moisture from the outdoor air.*CON*

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As the Passive House standard continues to make waves across New York City and the U.S., an entirely new design process has evolved to respond to the challenges of higher insulation levels, balanced mechanical ventilation, and perhaps the most difficult hurdle – an air tightness level that most would think is impossible. For the recently certified Cornell Tech building on Roosevelt Island, the tallest Passive House in the world, a several year-long coordinated effort was required to achieve such a feat. So what is the requirement, how is it measured, and what are the strategies and considerations required to achieve it?

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The number of multifamily residential projects targeting Passive House certification has been rising steadily over the past several years, bringing along many exciting challenges. This has been especially prevalent in New York City, where increasingly stringent energy standards and a desire for innovation have made designing to Passive House standards an attractive goal. As the number of these projects passing through our office continues to grow, we have discovered some important overlaps with one of our other consulting services – Accessibility Compliance.

In the United States, multifamily new construction projects consisting of four or more dwelling units are subject to the Fair Housing Act, as well as state, city, and local accessibility laws and codes. For the purposes of this blog we will focus on projects in NYC, although the majority of newly constructed residential projects across the country will be subject to some variation of the criteria discussed below, for both Passive House and Accessibility standards. With this in mind, we have chosen a couple of common problem areas that require particularly close attention. (more…)

Common laundry rooms are typically provided in market rate and affordable multifamily buildings. Because there are no ventless clothes dryers available for commercial use in North America (such as condensing or heat pump dryers), Passive House (PH) projects must make do with standard coin-operated, conventional vented clothes dryers. With a conventional electric or gas vented dryer, ambient air from the laundry room is heated and blown into the dryer’s drum as it tumbles. This air picks up the moisture from the laundry and is exhausted – sending hot moist air and lint particles to the outside. For any dryer that exhausts more than 200 cfm and in common laundries that have several dryers, make-up air must be supplied to the room so the dryers have enough air to operate properly. This make-up air must then be heated or cooled and therefore, increases the building’s energy demand.

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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.

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Green Energy Times is a bi-monthly publication chronicling the latest sustainability news in New England and New York (and beyond!). In 2016, SWA will be contributing a column for each issue. To start the year, SWA’s Heather Breslin discusses how and why the affordable housing market is beginning to embrace the Passive House Standard. The full article is featured below, or on page 27 of the February edition of Green Energy Times.  (more…)

Air-source heat pumps are a booming business. In the Northeast, manufacturers report that sales of residential systems have increased by 25-35% per year over the past 5-10 years. We’ve seen more and more systems being installed in existing homes (to provide cooling while offsetting oil or propane used for heating) and into new homes (often as the sole source of heating and cooling).

We’ve looked into these systems often, and from many perspectives. I’m planning a series of posts, but, for now, here are the answers to some basic questions we receive from clients.

First, the basics: What is an air-source heat pump (ASHP)?

It’s an air conditioner that can operate in reverse. During the summer, it moves heat from indoors to outdoors. In the winter, it moves heat from outdoors to indoors. We helped NEEP (the Northeast Energy Efficiency Partnerships) to put together a market assessment and strategy report on ASHPs. The early sections in this document (see p. 12) outline the different terms and types of heat pumps (ducted/ductless, split/packaged, mini-split, multi-split, central, etc.) Unfortunately, different people can use the same term to mean different things, but hopefully the NEEP Northeast/Mid-Atlantic Air-Source Heat Pump Strategies Report can help clarify things.

 

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Earning a green building certification is a significant achievement for a project as it represents a strong commitment to sustainability principles. When pursuing certification, it is essential to select the rating system best suited to your project type and performance goals.

In this blog piece, we will examine the anatomy of five popular green building rating systems, including their applicability to building type and a brief summation of typical advantages and challenges faced by clients pursuing certification. (more…)

SWA’s Senior Mechanical Engineer, Lois Arena, P.E., is one of the leading Passive House (PH) specialists in the country. She is regularly asked to speak about PH at conferences, after-hour educational events, and to firms seeking to increase their knowledge about the subject. For SWA’s clients, she provides a full suite of PH services including energy modeling and consulting to optimize energy efficiency and ensure that projects are designed and built to meet the rigorous Passive House Standard, as well as field testing throughout the construction process to aid the team in achieving the strict PH air leakage requirements.

In addition to working on multiple projects in the tri-state area, she is currently contributing to the groundbreaking Passive House project for Cornell’s new technical campus on Roosevelt Island. When completed, the residential tower will the tallest and largest Passive House building in the world!

The project has earned a lot of media coverage, from a groundbreaking ceremony that was attended by both NYC’s current Mayor Bill de Blasio and former Mayor Michael Bloomberg to an article in the New York Times and other media outlets. And of course now, on our Party Walls blog, where I was able to get the inside scoop on the project straight from the source!

Was Passive House certification Cornell’s initial goal for this project or was it recommended based on efficiency goals set by the owner or developers? (more…)