EIFS, Architecture, and the Sustainable Design Revolution

by Richard Martens, LEED AP
BASF Construction Chemicals, LLC - Wall Systems

Last updated: 09-14-2010

Introduction

Architecture has always been the marriage of aesthetics, function, economics, and building science. Every successful project ever constructed has balanced these often conflicting requirements.

Nonresidential projects are a financial exercise from beginning to end—projected revenue streams must cover construction and operating expenses, limiting the initial and life-cycle costs a project can bear. Function and aesthetics create building value-in-use. And if design is not supported with adequate building science, unexpected cost overruns and/or premature building failure are likely outcomes.

These interdependent considerations make architecture a uniquely challenging profession. The demands of sustainable construction add a further dimension of complexity.

Sustainability Drives Change in Design and Construction Practices

While conserving energy has become a national priority, the goals proposed by Edward Mazria in his Architecture 2030 Challenge take sustainability to a higher level. This program (supported by the AIA, U.S. Council of Mayors, U.S. EPA, and many others) targets a 60% reduction in carbon dioxide emissions by 2010, and additional 5% reductions every 5 years until building operation becomes 100% carbon neutral in 2030.

That means by 2030, operation of new buildings would not consume any greenhouse gas-creating fossil fuels whatsoever. Architecture 2030 raises the bar for everyone in the construction industry, not just architects.

To reduce energy consumption and address the goals of Architecture 2030, construction practices will need to change. Today's lowest initial-cost bid process will not be able to keep pace with ever-tightening regulations and increasing demand for high-performance buildings.

As design and construction become more sustainable, today's focus on lowest initial-cost will be displaced by integrated project delivery practices. Early design phase collaboration among larger, more diverse design teams will help architects deliver projects that are both sustainable and cost-effective.

Architects will need all the collaboration they can get. Trying to attain sustainability objectives through product selection is not likely to answer the complex tradeoffs inherent in architecture. Taking a holistic viewpoint enables designers to create systems-based strategies, where key components of the building are evaluated on their contributions to multiple design objectives. That way, aesthetic, functional, economic, building science and sustainability goals can be effectively reconciled to meet the emerging demands of 21st century architecture.

EIFS and the Initial-cost Paradigm

Exterior Insulation and Finish Systems (EIFS) are systems that can be configured in many ways to meet a range of end-use needs. Most of the EIFS used in the United States have been configured to meet demand for outstanding visual appeal at low initial cost. This has influenced general perceptions of the properties that EIFS are able to provide.

EIFS have performed very well in the lowest initial-cost environment, as shown by the large number of outstanding projects completed with EIFS claddings. Many of these buildings have performed well for 30 years or longer.

Take a life-cycle cost approach and EIFS can be reconfigured to do much more. Provision can be made for water drainage, R-value can be substantially increased, an air barrier can be added, and impact resistance dramatically improved, all for very little extra cost. Compare these High-Performance EIFS with traditional materials like brick, stone and metal composite, and EIFS can substantially reduce initial cost in addition to providing outstanding performance and aesthetics.

Controlling initial cost in addition to life-cycle cost is an important aspect of sustainable construction, because the pillars of architecture (aesthetics, function, economics, building science and now sustainability) will never change. This is particularly true for designers who intend to pursue certification under the new, more challenging LEED 2009 standard.

Description

EIFS Design for Sustainability

The U.S. Green Building Council's (USGBC) Leadership in Energy and Environmental Design (LEED) rating system provides a comprehensive approach to sustainability. It sets performance objectives for design professionals, and provides them with latitude to attain environmental goals in creative ways that take the needs of various stakeholders into account. As a result, materials per se do not qualify for credit under LEED. Performance counts—and designers that leverage the benefits of the materials they choose and maximize all dimensions of performance will be the most successful.

That is why a detailed understanding of the properties of High-Performance EIFS, and the ways that EIFS-related design decisions contribute to overall project objectives, is so important.

EIFS Design for LEED-rated Buildings

LEED has six sections—Sustainable Sites (SS), Water Efficiency (WE), Energy & Atmosphere (EA), Materials & Resources (MR), Indoor Environmental Quality (EQ) and Innovation & Design (ID).

The Material and Resources section deals with materials directly, but in the case of EIFS it is of secondary importance. That is because the greatest contributions EIFS can provide come from the combination of thermal performance, exterior appearance, weight reduction, and cost-effectiveness unique to these products. EIFS contribute toward multiple design objectives, helping architects create buildings that satisfy their many constituencies, including those related to LEED.

LEED-NC Energy and Atmosphere (EA) Prerequisite 2

This is where EIFS can make their most significant contributions to designs targeting LEED ratings. All new LEED-rated buildings must demonstrate an improvement in energy performance at least 10% beyond the requirements of ASHRAE 90.1-2007. Further improvement qualifies for up to 19 points under Energy and Atmosphere (EA) Credit 1.

When designing for energy efficiency, the building envelope is the place to start. Creating a tight, highly insulating building envelope is the most cost-effective way to minimize energy consumption. Reduction in base heating/cooling demand allows HVAC systems to be downsized, reducing initial cost and improving energy efficiency. For designers contemplating the use of alternate energy strategies such as building-integrated photovoltaics, an efficient building envelope is needed to ensure that these expensive resources are not wasted.

To maximize the benefits of High-Performance EIFS, it is important to understand how LEED evaluates the energy efficiency of a structure that has yet to be constructed. LEED provides both prescriptive compliance and thermal modeling options.

Prescriptive compliance paths developed by ASHRAE and the New Buildings Institute each provide a set of design requirements. All requirements must be fulfilled to meet EA Prerequisite 2 and attain a specific number of EA Credit 1 points. Thermal modeling is an alternate approach that uses computer software to simulate building energy performance. Projects that target more than 3 EA Credit 1 points must use thermal modeling.

LEED EA Prerequisite 2: Prescriptive Compliance Options

ASHRAE has developed a series of Advanced Energy Design Guides focused on Small Offices, Small Retail Buildings, Warehouses and K-12 Schools. These Guides contain prescriptive compliance paths that can be used to meet EA Prerequisite 2 and provide 1 point under EA Credit 1.

The New Building Institute's Advanced Buildings Core Performance Guide provides prescriptive options for larger buildings (up to 100,000 ft², excluding health care facilities, warehouses and laboratories). Meeting Core Performance Guide requirements can provide 1-3 points under EA Credit 1.

Two aspects of the ASHRAE and Core Performance Guide prescriptive compliance paths are relevant to EIFS design. First, all Guides require use of an air barrier. Second, the Guides require minimum levels of exterior wall insulation for each climate zone and wall configuration. While the Guides describe specific combinations of cavity insulation and continuous exterior insulation, they also define maximum wall assembly U-factors that can be used to qualify alternate insulation designs.

Interestingly, the four ASHRAE Guides, The Core Performance Guide and the ASHRAE 90.1-2007 standard all contain slightly different insulation requirements. For the sake of simplicity, the chart below combines all ASHRAE Design Guide and ASHRAE 90.1-2007 requirements. Simply specifying an EIFS with the thickness of expanded polystyrene (EPS) insulation in the chart below creates a wall system that meets all ASHRAE insulation requirements. Similarly, specifying the EPS thicknesses given in the following chart creates walls that meet Core Performance Guide insulation requirements.

EIFS EPS Thickness meeting ALL ASHRAE Requirements (inches)

Climate Zone	1	2	3	4	5	6	7	8
Mass Wall	1.5	2	3	3.5	3.5	3.5	4	4
Steel Framed	1.5	1.5	3.5	3.5	3.5	3.5	3.5
Wood Framed and Other	2.5	2.5	2.5	3.4	4	4	4

EIFS EPS Thickness meeting Core Performance Requirements (inches)

Climate Zone	1	2	3	4	5	6	7	8
Mass Wall	1.5	1.5	2	2	3	3	4	4
Metal Framed	3	3	3	3	3	4	3.5
Wood Framed and Other	3.5	3.5	3.5	3.5	3.5	3.5	3.5

The only compromise involved in placing all insulation outside of the framing is a slight increase in wall thickness. There are many benefits.

First, placing all of the insulation outside of the wall cavity reliably locates the dew point (the temperature at which humidity condenses to form water) outside of the wall cavity. This is a key consideration. Dew formation inside the wall can create conditions conducive to mold growth and material decomposition. Cavity insulation moves the dew point inward, and should be balanced with an appropriate amount of exterior insulation. By exploiting the high insulation value of EPS board used in an EIFS, walls can be designed to locate the dew point outside the wall sheathing. In an EIFS with drainage, sheathing is protected with a secondary water-resistive barrier and a drainage plane. Design professionals should always evaluate dew point locations for their projects.

Second, exterior insulation eliminates thermal bridging. In many climate zones, metal framed walls cannot meet prescriptive requirements without continuous exterior insulation. This is because thermal bridging reduces the effectiveness of cavity insulation by up to 65% - R21 batt insulation in certain cases delivers as little as R-7.4 actual performance.

Third, EPS insulation is highly cost-effective. EPS will be installed wherever an EIFS is used. Increasing the thickness of EPS adds insulation value for material cost only, since little or no extra labor is needed. In addition, all costs associated with cavity insulation can often be eliminated.

Fourth, thermal expansion and contraction of the building framing is dramatically reduced because framing is no longer subject to daily temperature changes. This reduces building movement and associated stresses.

Recently, the Department of Energy's Oak Ridge National Laboratory (PDF 69 KB, 3 pgs) completed a 30-month evaluation of the hygrothermal performance of EIFS, stucco, and brick walls. The wall system found to have the best overall performance—an EIFS with 4" of EPS insulation and an air barrier—meets or exceeds all ASHRAE and Core Performance Guide insulation and air barrier requirements in the continental U.S. and much of Alaska.

LEED EA Prerequisite 2: Thermal Modeling Option

Thermal modeling must be used for buildings larger than 100,000 square feet, for certain types of buildings, and whenever more than 3 points under EA Credit 1 is needed.

Thermal modeling software predicts the energy consumption of specific building designs. This software takes the benefits of air barriers into account, as well as the negative effects of thermal bridging.

While thermal models do not explicitly require building envelope performance like the Prescriptive Guides, the economics of the building envelope do not change. A tight, well-insulated building envelope is key to cost-effective reduction in energy consumption. EIFS provide excellent insulation value and air barrier performance. Designers that use thermal modeling get the same cost and performance benefits from High-Performance EIFS as those that use Prescriptive Compliance options.

LEED Credits Synergistic with EA Prerequisite 2 - MR Credit 1.1 Building Reuse

A synergy is an activity that makes a positive contribution to more than one LEED category. Recladding an existing building with EIFS facilitates reuse of the building, and also improves the insulation value of the building envelope. So EIFS can contribute to MR Credit 1.1 and EA Credit 1.

EIFS are an effective way to upgrade the appearance and curb appeal of an existing building while dramatically improving its energy performance.

LEED Credits Synergistic with EA Prerequisite 2 - EQ Credit 7.1 Thermal Comfort: Design

EIFS help attain this point as part of an overall plan to meet ASHRAE 55 requirements. The intention of ASHRAE 55 Section 6 is for the building envelope and HVAC system work together effectively, everywhere in the building. A building design that carefully integrates building envelope and HVAC systems design, as outlined in the EA Prerequisite 2 Section, clearly addresses this requirement of the ASHRAE 55 standard.

LEED Innovation and Design - ID Credit 1

The Innovation and Design credit makes provisions for innovations that benefit the environment. A major benefit of EIFS is their light weight. Not only does light weight translate directly to a lower resource demand and carbon footprint, it also dramatically reduces the embodied energy of a wall system. Lightweight EIFS reduce loading on the building frame and foundation, allowing other components of a building to be made lighter, further lowering their environmental burden.

Comparisons between EIFS, stucco, and brick walls made by RS Means¹ have shown that on a metal framed wall, EIFS contribute 2 lbs/ ft², compared with stucco at 14 lbs/ ft² and brick at 42 lbs/ft². Replacing a 100,000 ft² brick wall with EIFS reduces weight by over 4 million lbs—a savings of over 95%!

This is true eco-efficiency (PDF 500 KB, 36 pgs) — reducing environmental burden and the cost of construction.

Other Contributions to LEED Ratings

EIFS also contribute toward Materials and Resources (MR) Credit 2 Construction Waste Management, since EIFS produce very little waste, most of which is recyclable or reusable.

MR Credit 4 Recycled Content and Credit 5 Regional Materials are based on the weight percent of recycled and regional materials multiplied by the cost of the material. This final cost attributed to recycled and regional materials is divided by the total material cost of the building to create a final percentage. Buildings with greater than 10% recycled or regional material content are eligible for LEED points.

Conclusions

Architects have always been expected to balance the needs of a wide set of stakeholders to create designs that are functionally, aesthetically and economically effective. Sustainability adds a new dimension of challenge.

Those architects who are able to bring a systems perspective to these often-conflicting demands will have a competitive advantage over designers who select materials in isolation.

High-Performance EIFS can be used to advance multiple design objectives. They can create spectacular exterior appearances in a cost-effective manner. In addition, they can make significant contributions toward attainment of LEED Energy and Atmosphere Prerequisite 2 through specification of an air barrier and thermally efficient exterior insulation. Locating 100% of a building's insulation outside of the building sheathing reliably moves the dew point outside of the wall cavity, which is good design practice in all climate zones.

Lightweight EIFS reduce overall material consumption in a given building design, with clear environmental benefits in terms of resource conservation and embodied energy reduction.

The significantly greater eco-efficiency of EIFS over alternate wall cladding materials suggests that these innovative cladding materials will be used more extensively as demand for cost-effective, sustainable building design continues to rise.

Relevant Codes and Standards

• ASHRAE Standard 90.1-2007, Energy Standard for Buildings Except Low-Rise Residential Buildings
• International Code Council Evaluation Service Reports
• Miami-Dade County High Velocity Hurricane Zone Product Testing and Approvals

Additional Resources

WBDG

Building Types

All building types

Design Objectives

Aesthetics, Cost-Effective, Functional / Operational, Secure / Safe—Plan for Fire Protection, Secure / Safe—Resist Natural Hazards, Sustainable

Project Management

Building Commissioning

Products and Systems

Building Envelope Design Guide: Exterior Insulation and Finish System (EIFS)

Organizations

• EIFS Industry Members Association (EIMA)
• U.S. Green Building Council (USGBC) Leadership in Energy and Environmental Design (LEED)

Manufacturers

• BASF Wall Systems
  • Eco-Efficiency brochure (PDF)

Contact

Richard Martens, LEED AP – Market Manager, Nonresidential Sector
BASF Construction Chemicals LLC
Richard.Martens@basf.com

¹ RS Means evaluation of brick, stucco and EIFS wall cladding systems prepared for BASF Construction Chemicals, LLC.