SWA High Performance Design Best Practice: Limiting Shelf Angles in Masonry Buildings

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.

Fig. 1. An infrared (IR) image that shows the thermal impact of shelf angles

Fig. 1. An infrared (IR) image that shows the thermal impact of shelf angles

 

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).

Fig. 2. Typical FAST TM system detail

Fig. 2. Typical FAST TM system detail

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.

Fig.3. An offset shelf angle

Fig.3. An offset shelf angle

 

Fig.4. A wall section with an offset structural shelf angle

Fig.4. A wall section with an offset structural shelf angle

 

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>

Accessible Design: Common Mistakes & How to Avoid Them

Part 1: Public and Common-use Areas

After years of inspecting multifamily housing developments across the country for compliance with regulatory requirements for accessible design and construction, our accessibility group has compiled a list of common violations – violations that could easily have been avoided before construction even began. By addressing requirements for accessibility in the early phases of a project, designers can preempt the need for costly remediation during construction and greatly reduce the possibility of potential litigation.

Here are just a couple of examples of common violations that we come across on a regular basis:

  1. Slopes of Accessible Routes
    At least one accessible route is required to connect site arrival points, accessible building entrances, various site and building amenities, and dwelling units in the project. All too often, we arrive on site to find that the slopes of these accessible routes are not compliant (sometimes more than twice what is allowed), necessitating the ripping up of sidewalks and flooring materials – an undertaking that can quickly become expensive. When considering an accessible route, there are two important slopes to keep in mind: cross slope and running slope.

    — Cross slopes of accessible routes must be no more than 1:48 (2%). Areas where two accessible routes intersect, as well as the clearance at doors, must not exceed 2% when measured in any direction.
    — Running slopes of accessible routes must be no more than 1:20 (5%). If the running slope of an accessible route exceeds 5%, it is then considered a ramp and all ramp criteria apply, including the requirement for handrails on both sides of the ramp.

    By identifying the required accessible routes on the drawings, and providing notes and slope indicators along these routes rather than spot elevations, it is possible to greatly increase the chances of compliance once the concrete is poured and the building is constructed.

  2. Protruding Objects
    Sconces are common examples of protruding objects.

    Sconces are common examples of protruding objects.

    Accessible design isn’t just about ensuring equality for those with mobility impairments. Another important, and often missed requirement, applies to those with visual impairments. A protruding object can be something as basic as a wall sconce, bar countertop, or drinking fountain; and as seemingly innocuous as a piece of artwork on the wall. Any element that is located 27-80 inches AFF and projects more than 4 inches from a wall can prove hazardous to someone who does not have the ability to see it. The projecting objects themselves may seem small, but the cost of replacing hundreds of lighting fixtures throughout a building can be astronomical.

    While the best method of avoiding protruding objects is to specify wall-mounted sconces and other fixtures with a low profile, there will of course be situations that require other solutions. Where a protruding object exists, a cane-detectable barrier must be provided below it to ensure that a person with a visual impairment will be able to identify and avoid the potentially hazardous object. This can be as simple as positioning a planter or built-in piece of furniture below a wall sconce or piece of artwork, or installing a foot rail or knee wall below projecting bar countertops. Locating drinking fountains within alcoves is another method of achieving compliance.

By addressing these common violations in the design phase of a project, it is possible to greatly reduce the need for change orders and costly delays once construction begins. A little planning ahead can save a lot of time and money in the long run.

Stay tuned for Part 2: Dwelling Units – coming soon!

HUD’s 2015 IAH Graduate Student Design Competition: SWA Supported

2015_IAH_Banner

HUD’s 2015 Innovation in Affordable Housing student design and planning competition has hit full stride. Building on its successful inaugural run in 2014, this year’s competition has university representation from over 20 states. Strategic teams of 3-5 graduate students and a faculty advisor, primarily from architecture, urban planning, real estate, business, and environmental engineering programs, are challenged with redesigning a 300-unit senior housing property for the Houma-Terrebonne Housing Authority (HTHA). Competitors will craft actionable solutions that consider economic, social, and ecologic issues unique to the region’s affordable senior housing sector. Successful projects will address needs of senior residents (quality of life), site and building codes, finance strategies (incl. leveraging partnerships), integrated energy efficiency technology, and community connectivity. Following a rigorous review process, select finalists will travel to Houma, LA in March for a site-visit intended to prepare competitors for refining their final submission. The winning entry will be chosen by a judging panel of industry thought-leaders, and awarded $20,000 at a ceremony in Washington, DC ($10,000 to the runner-up).

Steven Winter Associates, Inc. (SWA) recognizes the critical need for global availability of quality, affordable housing. Our support of HUD’s competition will advance studies in this emerging market by initiating a new generation of student-professionals into the industry. SWA fulfilled a lead role in competition development, outlining the competitive structure, project submission requirements and guidelines, and final judging criteria. Additionally, SWA spearheaded all marketing efforts for the competition, including a robust registration outreach campaign consisting of email blasts, phone communication, social media, and direct mailing. Work on the IAH competition demonstrates the firm’s continued support of student and professional competitions, adding to past programming efforts with the SBIC’s Beyond Green™ High Performance Building Awards and the Housing Authority of Norwalk’s Affordable Housing Design Competition. The firm’s involvement reinforces SWA’s commitment to progressing innovation in high performance building practices, and validates SWA’s reputation as an industry authority on sustainable multifamily building science.

Visit the the #IAH2015 website here: bit.ly/IAH2015

The Access Files – The Truth is Out There

Peter Stratton

Peter Stratton, SWA’s Director of Accessibility Compliance and Consulting

SWA Access is the quarterly publication created by SWA’s Accessibility Compliance and Consulting Group to convey the importance of, and help  demystify the often complex world of accessible design, construction, and compliance. After all, as the group’s director, Peter Stratton, often says, “Sustainable Design is Accessible Design.”

Each edition of the newsletter features a section that answers specific questions asked during project work or public seminars. We will periodically post these items to Party Walls, but if there’s something you would like answered now, you can post your question in the comment section below and someone from SWA’s accessibility team will answer them (and in a timely manner!)

Q: Under the Fair Housing Amendments Act, are multifamily housing developments that utilize valet parking still required to provide a total of 2% accessible parking spaces serving covered dwelling units?

A: Yes. the guidelines require that accessible parking be provided for residents with disabilities on the same terms and with the full range of choices that are provided to all residents. Providing valet parking in lieu of self parking does not change this requirement. A minimum of 2% of the parking spaces that serve covered dwelling units must be accessible. Local code requirements may be more stringent when it comes to requirements for accessible parking. Find more information by visiting:
Supplement to Notice of Fair Housing Accessibility Guidelines: Questions and Answers about the Guidelines.

Q: Is it true that HUD now accepts the 2010 ADA Standards (2010 Standards) as an alternative to the Uniform Federal Accessibility Standards (UFAS) for compliance with Section 504 of the Rehabilitation Act of 1973 (Section 504)?

A: Yes. HUD issued a Notice, effective May 23, 2014, that permits recipients of Federal funding to use the 2010 Standards as an alternative to UFAS on projects subject to Section 504. However, HUD has deemed certain provisions of the 2010 Standards to provide less accessibility than is currently required by UFAS. So, be sure to learn about the exceptions if you choose to apply the 2010 Standards to your next project. HUD’s Notice remains in effect until the agency formally adopts an updated accessibility standard for compliance with Section 504.