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13JANUARY 2017SITESC O N S T R U C T I O N12 JANUARY 2017 SITESC O N S T R U C T I O N

The Role of Building Envelope In Achieving High Performance Goals

By: Diaa El-MasryArchitect, LEED AP, GSAS CGPGeneral ManagerQatar Green Leaders

Building Envelope & Green BuildingBuilding envelope has direct impact to severalaspects of Green Building criteria. It affects (negatively or positively) the ability of a buildingto meet certain green building requirements/criteria. Two of the common green building rat-ing systems, namely LEED & GSAS, have been analyzed to figure out the relationship between building envelope and the overall performance of the whole building.

LEED (Leadership in Energy & Environmental Design) is a glob-ally recognized green building rating system developed by USG-BC (United States Green Building

Council). LEED is adopted in Qatar for a large number of projects, mainly in Education City and Msheireb Downtown Doha project.

GSAS (Global Sustainability As-sessment System) is a regionally recognized green building rat-ing system developed by GORD (Gulf Organization for Research & Development). GSAS is widely

adopted in Qatar for a larger number of proj-ects, mainly in Lusail City and governmental projects.

Both systems are performance-based, using a point-based mechanism to award projects more points for performing better in several performance categories. The following is a summary of our findings, which reflects the im-portance of the building envelope in achieving higher performance under LEED & GSAS:

General Considerations:

LEED - (IP) Integrative Process

• Building Orientation• Building Massing & Shading• Integration of Envelope Properties• Feasibility of Different Alternatives

Urban Considerations:

LEED - (LL) Location & LinkageGSAS - [UC] Urban Connectivity

• Acoustic Conditions of the Building Surroundings.• Crime Prevention.• Privacy Control.• Security Requirements.

Site Considerations:

LEED - (SS) Sustainable SitesGSAS - [S] Site

• Heat Island Effect Reduction - Roof• Light Pollution Reduction• Wind Comfort• Shading of Pathways• Rainwater Management

Water Conservation:

LEED – (WE) Water EfficiencyGSAS - [W] Water

• Rain Water Collection from Roof• Water used for Cleaning Envelope!

ABSTRACTIn this Article, we will focus on the relationshipbetween building envelope and green buildingperformance, not only in Energy saving but alsoin other aspects of green building. We will pro-vide a quick guide on how to enhance the pa-rameters of the building envelope in order to fill the gap between code requirements and green building goals.

TOPICS• A Building Envelope is Not Just Envelope/ Shelter!• Functions & Performance Parameters.• International & Local Codes.• Building Envelope and Performance Criteria in LEED & GSAS.• Better Envelopes, Innovations & Advance- ments

WHAT DEFINES A BUILDING ENVELOPE?A building envelope: is the physical separator between the conditioned (indoors) and uncon-ditioned (outdoors) environment of a building. It is sometimes used synonymously with build-ing enclosure but the latter term also includes the broader aspects of appearance, structure, safety from fire and security. It can take many forms and compositions, but basically it may be composed of the following components:

• Floors (Below-Grade Systems)• Walls (Walling Systems)• Roofs (Roofing Systems)• Fenestration (Glazing Systems)• Shading Elements

FUNCTIONS OF BUILDING ENVELOPEDepending on many aspects of the building architectural form, the building envelope plays an essential role in “sheltering” the building oc-cupants. The Five basic functions of a buildingenvelope are:

• Weather Barrier• Air Barrier• Thermal Barrier• Alien Barrier!• Structural.

It means that the building envelope provides resistance to the following:

• Air (wind/air leakage)• Heat (hot/cold)• Light (indoor/outdoor)• Noise (in/out)• Loads (dead/live/wind)• Intrusion (safety/security/privacy)

A BUILDING ENVELOPE IS A SYSTEMA building envelope is not just a Shelter! Build-ing Envelope is a Sub-System of the Whole- Building. It is not just a wall/roof/floor/window/ door/... but, A SYSTEM! It can be considered as a sub-system of the building. And, by turn, it is composed of various sub-systems. By applying the “Systems Thinking” approach, we find that

building envelope is not only providing a “shel-ter” to building occupants but also contributing to the overall building performance. Usually, we think of building performance in terms of en-ergy saving and we think a better building enve-lope is improving only the energy performance.However, when measuring the performance ofa building by a green building rating system (such as LEED or GSAS), it is not a surprise thatthe building envelope is affecting various per-formance criteria. For instance, the following areas can be improved by applying a better building envelope:

• Prevention of heat loss/gain and reduce Energy demand• Urban Function and Cultural Identity• Architectural Innovation and Advanced Technologies• Sustainable Source as a Green Building element• Building Envelope is vital section of Building Science

A “BETTER” BUILDING EN- VELOPE?The performance of the Building Envelope con-tributes (negatively of positively) to the overallbuilding performance. The role a building en-velope plays in buildings is very similar to the role the skin plays in a human body! There are many factors that will help an architect defines a proper building envelope:

• Location (Climate Zone)• Season (summer/winter)• Operating Conditions (temp./humidity/...)• Appearance (color/texture/SRI/...)• Thickness (Composition/Layers)• Materials (conductivity/appearance/…)• Thermal Break (u-value/details/...)• Air Leakage (details/sealing/...)• Maintenance Frequency (commissioning/ cleaning/repairs/retrofits/...)

REGULATIONS AND CODES:On a related aspect, the building envelope is also regulated at different levels:

• International Standards• Local Codes/Building Regulations• Green Building Codes• Project Spec’s/Developer Requirements

I. INTERNATIONAL STANDARDS:* 2015 IECC (International Energy Conserva-tion Code, by International Code Council (ICC),Section C402 - Building Envelope).* ASHRAE Standard 90.1 (ANSI / ASHRAE / IESStandard 90.1-2016 -- Energy Standard for Buildings Except Low-Rise Residential Build-ings (5.2.1. Insulation, 5.2.2. Fenestration and Doors, 5.2.3. Air Leakage, ...).

II. LOCAL CODES (QCS, KAHRAMAA, PWA)• Kahramaa Regulations• QCS 2014 (Qatar Construction Specifications)• MMUP Urban Planning Regulations

Energy Conservation:

LEED – (EA) Energy & AtmosphereGSAS - [E] Energy

• Building Orientation & Massing• Envelope Area/Volume• Window/Wall Ratio• U-Values (Roof/Walls/Glazing/Floor)• Shading Coefficient (SC) of Glazing• Solar Heat Gain Coefficient (SHGC) of Glazing• Window Frame Fraction• Air Tightness• Shading Devices (Internal/External)• Integrated PV (BIPV)• Commissioning of Building Envelope

Material Procurement:

LEED – (MR) Materials & ResourcesGSAS - [M] Materials

• Responsible Sourcing of Materials• % Regional Material used in Envelope• % Recycled Content• Reused Materials• Structure Reuse• Design for Dis-assembly• Construction Waste Management

Human Considerations:

LEED – Indoor Environmental QualityGSAS - [IE] Indoor Environment

• Thermal Comfort of Building Users• Natural Ventilation (Operable Windows)• Indoor Air Quality• Low-Emitting Materials (Sealants)• Day-light & Views• Glare Control• Acoustic Control & Quality

Culture & Identity Considerations:

GSAS - [CE] Culture & Economic Value

• Heritage & Culture Identity• Support of National Economy• Integration in Urban Context

Conclusion:From the above analysis, we found that the Im-pact of Building Envelope in projects pursuing LEED & GSAS green building certification can be estimated as follows:

LEED:

• Total Credits = 57• Envelope-Related = 20• Weighted Impact* = 46 %

GSAS

• Total Criteria = 55• Envelope-Related = 21• Weighted Impact* = 48 %

(*) Estimations are based on GSAS-Commercial & LEED-NC v4.0 Rating Systems