Party Walls

Overview

There have been several local and global developments recently with regards to off-shore wind turbines. Advancements in energy storage from both wind and solar energy, coupled with the increased rate of adoption of wind turbines could serve as a major step towards a more renewable-based energy grid and a more sustainable future.

Updates on Energy Production

First, let’s explore some recent news surrounding the adoption of off-shore wind turbines. On a global scale, Scotland’s Hywind project recently proved that technology developed for and by the oil drilling industry can be successfully applied to off-shore wind turbines.[2] The floating 30 MW wind farm, made up of five turbines off the Aberdeenshire coast, has been operational since October 2017. During a three-month period of stormy conditions from November 2018 to January 2019, the wind farm managed to continue energy production at 65% of their maximum capacity. Note that during this period, a North Atlantic hurricane produced swells up to 27 feet! Over the course of a year “maximum capacity” is approximately 135 GWh of electricity – or enough to power 20,000 Scottish homes. To ensure that the turbines can withstand weather events on that scale, the floating turbines are ballasted by 5,000 tons of iron ore, and 1,323 tons of chain anchor it to the seafloor. This off-shore farm proves that wind turbines can be successfully deployed in deeper waters where it would be increasingly expensive to extend the physical structure of the turbine tower to the seafloor. Additionally, the US, UK, Ireland, Portugal, Spain, France, and South Korea all have started to piggyback off the success of the Hywind farm in various ways. For instance, South Korea partnered with the Equinor, the primary backer of Hywind, to conduct a feasibility study for a 200 MW farm that would be located off the coast of Ulsan.[3][4][5][6]

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Heat Pump Water Heaters in Multifamily Buildings

In Electrify Everything? Part 1 that I wrote several months ago, I mentioned that integrated tank heat pump water heaters (HPWHs) can work well in single family homes — even in colder climates. For example, we see quite a few installed successfully in basements in the Northeast. These devices remove heat from the surrounding air, so there needs to be enough heat in the basement air for them to work effectively. During the winter, a home’s space heating system probably needs to work harder to make up for the HPWH. In the summer, the HPWH provides a bit of extra cooling and dehumidification. We put together some guidelines a few years ago on how to get the most from these systems in single family homes.

Some places where I’ve seen problems:

•   Installing a HPWH in a basement closet. Even if a closet has louvered doors, there’s not enough heat/air for a HPWH to work well.
• HPWHs are relatively loud. If there’s a finished part of the basement (e.g., bedroom or office), the noise can be disruptive.
• Sometimes there is trivial heat gain to the basement (from outdoors, mechanical equipment, etc.). When a HPWH removes heat from the air, such a basement can quickly become too cold for the water heater to work efficiently (and too cold for comfort if someone uses the basement).

But overall, HPWHs in single family basements can work effectively.

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Net zero buildings are becoming increasingly mainstream, with many jurisdictions adopting policies to move towards net zero new construction codes. A good overview of advanced energy codes is available on the Getting to Zero Forum, which includes a snapshot of activity around the country including Washington, DC, New York and Massachusetts.

What Does it Mean to be Net Zero?

The term “net zero” commonly refers to zero-energy buildings. In simple terms, a zero-energy building is one that produces as much energy as it consumes on an annual basis. There can be nuances and caveats to this definition, but for now, we want to bring you up to speed on five key net zero energy strategies to consider if you’re interested in developing a net zero building.

1. Maximize space for on-site renewable energy.

How tall is your building?

• Any building over five stories will be challenging, if not impossible, to achieve net zero with on-site renewable energy production alone because building energy demand will likely exceed available site area. Maximize your solar with a smart layout and consider if other renewables, such as geothermal, are possible.

Do you have other spaces available for solar photovoltaics (PV)?

• Your development may have a separate parking garage or parking lot on site. These are great places to install a PV system, which can significantly increase the amount of on-site renewable energy production and help make achieving net zero more of a reality.

Do I have to have all renewables on-site to be net zero?

• If you don’t have enough room for on-site renewables, you can look into purchasing off-site renewable energy options, such as community solar, power purchase agreements, or renewable energy credits.

Now that you’ve considered renewables, let’s move on to net zero building design considerations.

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Letter grades are coming!

NYC’s building owners and real estate management firms now have one more thing on their plate to consider: Local Law 33 of 2018. LL33 compliance will assign letter grades to buildings required to benchmark energy and water consumption. The energy efficiency score will relate to the Energy Star Rating earned using the U.S. EPA Energy Star Portfolio Manager (PM). The law will come into effect on January 1, 2020, and will utilize the previous year energy data to set the energy efficiency score and letter grade as follows:

A – score is equal to or greater than 85;
B – score is equal to or greater than 70 but less than 85;
C – score is equal to or greater than 55 but less than 70;
D – score is less than 55;
F – for buildings that fail to submit required benchmarking information;
N – for buildings exempted from benchmarking or not covered by the Energy Star program.

Why is my letter grade lower than expected?

Property owners should be made aware that if their property earned an energy efficiency score of 75 for the 2018 Benchmarking filing, the new score for the 2019 benchmarking filing may have fallen as much as 20 points. In LL33 terms, what could have been a letter grade “B” could now be “C” or “D” based on PM updates implemented in August 2018. Property owners will want to learn how the Energy Star PM update will affect their LL33 letter grade.

To understand the correlation and impact that the August 26, 2018 Energy Star PM update will have, it is important to look back at what took place as part of that update. (more…)

I can get worked up about units, and this can really annoy people. It especially annoyed students I taught in grad school. I was pretty tyrannical when grading; they always had to include units in their calculations. They could have all the right numbers, but they didn’t get full credit unless all the units were right too. I have no regrets about being such a stickler, because I see tons of confusion about this in the building & energy fields. So here’s a rant about one of my pet peeves: power and energy.

Question: What’s the difference between Power and Energy?

Is this some kind of philosophical question? A koan to meditate upon? No. There’s a real answer (in the engineering world at least). Power is the rate of energy.

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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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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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As a native Californian, I often marvel at my home state’s progressive attitude towards environmental conservation. In 1988, we were the first state to adopt air quality standards, which the federal Clean Air Act would later be amended to resemble. More recently, landmark legislation such as A.B. 32, or California’s Global Warming Solutions Act of 2006, set the first statewide requirements for GHG emissions reductions in the country. Today, cities like San Francisco have plastic bag bans and zero-waste initiatives. However, our culture is one of sustainability partly out of necessity—in January 2014, Governor Brown declared California’s severe and sustained drought situation a state of emergency. Despite our already resource-constrained present, California’s population is anticipated to increase by 14% over the next fifteen years to 44 million people. The good news is, we’ve made some big strides recently in planning for the future demands of an ever-growing population.

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Earlier this week, we posted a video about the CT Zero Energy Challenge’s first-place winner, the Benker/Wegner Residence. Today we bring you the story of the third-place winner in this year’s challenge, the Taft School’s Residence. Aside from housing faculty members, the home is serving as a teaching aid for Taft students to study the design details of a high-performance home, and to understand the experience of living in one.

After installation of a 13kW photovoltaic (PV) system, the home achieved a HERS Index of -14! The SWA team is providing certification support for a slew of exciting green building programs including the stringent Passive House US™ Certification, LEED for Homes, Living Building Challenge™, and ENERGY STAR v3.1.

Check out the video featuring the project team members: Architect, Elizabeth DiSalvo from Trillium Architects; Builder, Chris Trolle from BPC Green Builders; and SWA’s Maureen Mahle.

Question? Comment? Submit it below; we would love to hear from you!

BACKGROUND

The multifamily building industry has adopted a best practice long touted by the building science community: continuous insulation at the exterior of the building. However, even in this ideal circumstance in which the insulation is installed flush and without gaps against the exterior substrate (concrete block or sheathing) with an air barrier applied to this substrate beforehand, the overall performance of the insulation will be vastly reduced by the installation of shelf angles.

Shelf angles (also know as relieving angles) are designed to support the expansion and contraction of the brick coursing; however, this presents a direct challenge to the continuity of exterior insulation. Standard design details interrupt the exterior insulation at every shelf angle, typically at every floor in line with window lintels. Since the shelf angle is made of steel, a highly conductive material, this interruption impacts not only the effectiveness of the insulation in general, it provides a considerable thermal bridge over the entire horizontal band of the building at every occurrence.

A recent article by Urban Green Council, “State Energy Code Clarification Will Stem Heat Loss through Walls,” made it clear that a continuous shelf angle has “about the same poor thermal performance as [an] exposed slab edge.” The full article can be read here.

 

SWA RECOMMENDATION #1: LIMITING SHELF ANGLES

Not all buildings require relieving angles. Building owners, architects, and structural engineers should first ask themselves whether relieving angles are necessary at all for the building being designed. If it is determined that these angles will be necessary, the next question the structural engineer should ask himself is what the minimum frequency necessary is to support the brick course. Generally speaking, buildings do not need one shelf angle per floor—despite this being common practice.

In addition to the aforementioned energy implications involved in specifying shelf angles, there are other benefits to eliminating these steel members when possible. The most obvious impact is on upfront costs. At approximately $25/foot of angle iron (via Union Iron Works), shelf angles for multifamily buildings in New York City can cost tens of thousands of dollars.

Upfront and operating (i.e. energy) costs aside, there is also the embodied energy of the material to consider. Not only does the manufacture of the steel angle contribute to its embodied energy, but also all of the energy used to transport these pieces to the project site. By reducing the need for the production of these angles, the overall energy expended to construct a new building decreases.

One additional consideration for owners is the maintenance required for shelf angles. The introduction of brick lintels creates an inherent and inevitable need for future maintenance. Since the cost of this upkeep is often considerable, owners may wish to use the opportunity to limit shelf angles during design to reduce long-term maintenance costs.

 

SWA RECOMMENDATION #2: OFFSETTING SHELF ANGLES

In addition to limiting their frequency, consider a shelf angle offset to further reduce thermal bridging. One such system that allows for this is manufactured by FERO called FAST (FERO Angle Support Technology).

FAST is designed to offset the shelf angle from the structural backing, allowing the insulation and air barrier installations to be more continuous. More information about this product can be found on their website.

SWA welcomes the input of design teams for other possible solutions to achieve a more continuously insulated wall. By accomplishing this, the building will have a truly continuous thermal envelope. As a result, thermal bridging will be eliminated along with the associated energy losses.

 

 

CONCLUSION

To implement best building practices, fulfill the continuous insulation requirements of certification programs, and comply with NYC Energy Conservation and Construction Code, SWA recommends limiting the number of shelf angles in the construction of the envelope. This will help limit upfront material and long-term maintenance costs.

SWA also recommends off-setting the shelf angle to reduce the thermal bridging these steel elements create. Fewer shelf angles means that there are less obstacles imposed on exterior insulation, resulting in less thermal bridging. Limiting the impact of shelf angles produces a more robust and insulated envelope that will, in turn, positively impact the energy performance of the building and comfort of its occupants.

SWA would like to thank Robert Murray for his assistance with this article.

Robert J. Murray, P.E., LEED AP, Principal
Murray Engineering, PC
307 Seventh Avenue, Suite 1001
New York, NY 10001
Telephone: 212.741.1102
Email: rmurray@murray-engineering.com

 

REFERENCES

1. Anderson, J., D’Aloisio, J. DeLong, D., Miller-Johnson, R., Oberdorf, K., Ranieri, R., Stine, T., and Weisenberger, G. “Thermal Bridging Solutions: Minimizing Structural Steel’s Impact on Building Envelope Energy Transfer.” American Institute of Steel Construction. Modern Steel Construction, 1 Mar. 2012. Web. <http://msc.aisc.org/globalassets/modern-steel/archives/2012/03/2012v03_thermal_bridging.pdf>.

2. FERO: Engineered Construction Technologies. Product Catalogue. Edmonton: FERO: Engineered Construction Technologies, 2014. Web. <http://www.ferocorp.com/pages/fast/fast.html>