Mechanical + electrical systems in architecture, engineering, and construction--TOC

A general introduction to common building industry practices and trends ensures that the reader has a basic understanding of the industry. Such an understanding is beneficial because it validates the need for all building industry professionals to under stand the subjects presented in this text: building mechanical and electrical materials, components, equipment, and systems.

This introduction is particularly helpful to the reader who has little or no experience in the building industry.

THE BUILDING INDUSTRY

The global architecture, engineering, and construction (AEC) industry accounts for about 10% of the world's gross domestic product, 7% of all employment, and approximately half of all resource use, including about 40% of all energy consumption.

In the United States, the AEC industry is over a trillion dollar business ($1.7 trillion for construction alone in 2005). In 2005, the U.S. construction industry directly employed 7.3 million people and another 1.3 million people in architecture and engineering. The AEC industry is big business in the United States and worldwide.

In the AEC industry, architects and their support staff de sign buildings, while engineers and their support staff design the engineering systems within these buildings. Constructors, serving as contractors, and their employees and subcontractors build buildings. Construction managers supervise the construction project. Facilities managers and staff operate and maintain buildings. All players must effectively work together as the building design, construction, and operation team.

THE BUILDING MECHANICAL AND ELECTRICAL SYSTEMS

Well-designed, modern buildings are made up of many components and pieces of equipment that are integrated so that, when they are operated and maintained properly, they mutually per form as a single system. Simply put, an efficient building system is made up of many elemental systems. In buildings, mechanical and electrical technologies are among the most expensive and labor-intensive of these elemental systems. These mechanical and electrical technologies are used for heating, ventilating, and air conditioning (HVAC), illumination, electrical power distribution, plumbing and piping (water supply and sanitary drainage), storm drainage, building telecommunications, acoustics and acoustical control, vertical/horizontal transportation and conveying, fire protection and suppression, renewable energy sources, heat recovery, and energy conservation.

Mechanical and electrical systems in the building construction industry fit within classifications known as mechanical/ electrical/plumbing (MEP) or electrical/mechanical/plumbing/fire protection (E/M/P/FP) systems. MEP systems influence occupant health, comfort, and productivity, and greatly affect costs, including the first cost and operating (energy use and maintenance) costs. MEP systems are the heart and nervous system of a building.

ENVIRONMENTAL IMPACT OF BUILDINGS

The earth's natural resources are limited and world population continues to increase. With the passing of each day, there is a greater and greater reliance on natural resources and more degradation of the environment. Buildings account for a large amount of resource (energy and water) consumption, land use, atmospheric greenhouse gas emissions, and generation of environmental waste and pollution.

With about 4.5% of the world's population, the United States consumes nearly 23% of the total global energy. This means that the U.S. consumes energy over 5 times the world per capita average and over 100 times more per capita than many undeveloped countries. The United States is not alone in its energy-use intensity. Countries like Qatar, Kuwait, Norway, and Canada use energy at a higher per capita rate. From a global perspective, more developed, industrialized countries (e.g., countries in Europe, North America, Australia, New Zealand, and Japan) make up only about 17% of the world's population but use about three-quarters of the world's energy resources.

About 40% of the energy consumed in the United States is used in buildings. Thus, U.S. buildings use between 9 and 10% of the energy consumed worldwide. Of the energy consumed in U.S. buildings, about 40% is for space (comfort) heating, cooling, and ventilation; about 18% is used for lighting; and almost 20% is used for domestic water heating. (See Tables P.1 and P.2). About two-thirds of the electrical power produced is consumed in buildings. In addition, U.S. buildings generate about 40% of the atmospheric emissions that make up green house gases. Comparable magnitudes are used in most developed European and Asian countries. As a result, MEP systems have a significant influence on global resource consumption and associated waste and pollution.

Developed and developing countries are totally dependent on natural (material and energy) resources. Many less developed countries (e.g., countries in Africa, Asia [excluding Japan], regions of Melanesia, Micronesia, and Polynesia, Latin America, and the Caribbean) are striving to become more industrialized.

Many Asian countries (e.g., China, India, Taiwan, and South Korea) and some Middle Eastern countries (e.g., Dubai, Qatar, and United Arab Emirates) are examples of countries experiencing rapid growth. These countries are becoming more resource-use intensive at a time when their rate of population growth is substantial. As developing countries move toward industrialization, resource use in these countries increases substantially, so that limited global resources are taxed more and will be exhausted sooner. A growing global population coupled with ever increasing reliance on natural resources combines to create an outcome that is alarming. This concern makes a strong case for integration of sustainable design practices in building MEP systems.

SUSTAINABLE BUILDINGS

Sustainability is our ability to meet current needs without harming the environmental, economic, and societal systems on which future generations will rely for meeting their needs. It simply means using resources wisely. A sustainable or green building is designed to lessen the overall impact of a building on the environment and human health by efficiently using resources (i.e., energy, materials, and water), enhancing occupant health and employee productivity, and eliminating or reducing waste and pollution. Reducing the amount of natural resources required in constructing and operating buildings and the amount of pollution generated by buildings is crucial for future sustainability. In buildings, this can be accomplished by effectively using materials, increasing efficiency, and, developing and using new and renewable energy technologies.

TBL P.1 RESIDENTIAL BUILDING ENERGY USE, BY PERCENTAGE.

End Use:

Space heating , Appliances , Water heating , Refrigerators , Space cooling , Dishwashers

Single Family | Multifamily

52% 33%

22% 23%

17% 32%

4% 6%

4% 5%

1% 1%

TBL P.2 COMMERCIAL BUILDING ENERGY USE, BY PERCENTAGE.

End Use / Office / Health Care / Retail / K-12 Schools / Colleges, Univ. / Governmental / Lodging

Space heating 25% 23% 30% 45% 32% 36% 16% Space cooling 9% 4% 10% 6% 5% 5% 6% Ventilation 5% 3% 4% 2% 2% 3% 1% Water heating 9% 28% 6% 19% 24% 17% 41% Lighting 29% 16% 37% 19% 22% 21% 20% Cooking 1% 5% 3% 2% 1% 2% 4% Office equipment 16% 6% 4% 2% 2% 6% 3% Refrigeration Negl. 2% 1% 1% 1% 2% 2% Miscellaneous 5% 13% 5% 2% 11% 7% 6%

= = =

TBL P.3 CHARACTERISTIC PERCENTAGE OF CONSTRUCTION AND COST BREAKDOWN OF A 100 000 FT^2 OFFICE BUILDING PROJECT.

Division of Work:

General conditions; Site work; Concrete; Masonry; Metals; Woods and plastics; Thermal/moisture protection; Doors and windows; Finishes; Specialties; Equipment; Furnishings; Special construction; Conveying systems; Mechanical; Electrical; Total

Percentage of Construction :

11%

10%

100%

Cost Breakdown :

$ 750 000

$ 1 000 000

$ 2 000 000

$ 2 750 000

$ 1 000 000

$ 2 500 000

$ 2 000 000

$ 2 250 000

$ 1 000 000

$ 1 250 000

$ 1 000 000

$ 750 000

$ 1 000 000

$ 2 500 000

$ 1 500 000

$25 000 000

Description:

General procedures, superintendent, trailer, fence, traffic control, insurance

Excavation/backfill, roads, walks, landscaping

Concrete foundations, framing, slabs

Concrete masonry, brick, stone, reinforcement, mortar, grout

Structural steel framing, light-gauge framing

Wood framing, millwork, cabinetry

Insulation, roof coverings, caulking, cladding

Doors, windows, glass, and glazing

Drywall, plaster, floor and ceiling coverings, paint

Signs, flagpoles, restroom accessories

Kitchen equipment, laboratory casework

Artwork, furniture, room partitions

Computer rooms, clean rooms

Elevators, escalators, moving ramps, walkways

HVAC, plumbing, fire protection

Power distribution, lighting, telecommunication

Complete project construction costs

= = =

MEP DESIGN AND LAYOUT

MEP components and equipment influence building design and layout. Dedicated building spaces or rooms must be reserved for MEP components and equipment and serve as the nucleus of these technologies. This can include, but is not limited to, central utility plants, boiler and chiller rooms, fuel rooms, electrical switchboard rooms, transformer vaults, and metering and communications closets. These spaces can make up a significant portion of a building floor area. Large commercial buildings have a single mechanical room of considerable size and often require additional rooms throughout the building. Sky scrapers may have mechanical spaces that occupy one or more complete floors. In contrast, a small commercial building or single-family residence may only have a small utility room.

The size of MEP rooms is typically tied to building occupancy type and is usually proportional to the building size; that is, hospitals and medical centers require more MEP space than schools, offices, and residences. For example, in offices, department stores, and schools, the MEP floor area is typically in the range of about 3 to 8% of the gross floor area; in hospitals, it’s about 7 to 15%; and in residences, it’s typically less than 3%.

Allowances must be made by the building designer to locate spaces near the habitable spaces, especially those spaces with the largest demand for heating, cooling, power, and water (i.e., kitchens, restrooms, bathrooms, and so forth).

MEP SYSTEM COSTS

Design and construction costs of MEP components and equipment are significant in buildings. Commercial and institutional buildings and large residences necessitate that an engineer de sign the MEP systems, whereas, in small residences, design is done by the mechanical and electrical trades. Design fees for MEP systems in commercial buildings typically range from 20 to 40% of the overall design costs, depending on building occupancy type and size.

Actual MEP construction costs for buildings vary by building occupancy type and construction method. In residences and retail stores, the range is generally between 10 and 20% of the construction costs; for kindergarten through high schools (K-12), it ranges from 15 to 30%; for office and university classroom buildings, it ranges between 20 and 30%; and for hospitals and medical centers, it’s typically between 25 and 50%. A characteristic percentage of construction and cost breakdown of a commercial office building project is provided in Tbl. P.3. In this example, mechanical and electrical systems (including conveying systems) account for 20% of the overall project construction costs.

MEP ASSOCIATIONS, SOCIETIES, AND AGENCIES

Many professional associations and trade organizations support the various MEP fields. Professional and trade associations are membership organizations, usually nonprofit, that serve the interests of members who share a common field and promote professional and technical competence within the sustaining industry.

Professional organizations, frequently called societies, consist of individuals of a common profession, whereas trade associations consist of companies in a particular industry. However, the distinction is not uniform; some professional associations also accept certain corporate members, and conversely, trade associations may allow individual members. The activities of both trade and professional associations are similar and the ultimate goal is to promote, through cooperation, the economic activities of the members while maintaining ethical practices.

Additionally, professional associations have the objectives of expanding the knowledge or skills of its members and writing professional standards. Many governmental agencies also exist that support the work of these industries. Examples of professional, trade, and governmental entities are provided in Tbl. P.4.

CONSTRUCTION STANDARDS AND BUILDING CODES

In the AEC industry, a standard is a set of specifications and de sign/construction techniques written by a standards writing organization ( see Tbl. P.4) or group of industry professionals that seek to standardize materials, components, equipment, or methods of construction and operation. In the United States, a building code is a law adopted by a state or is an ordinance (a local law) approved by a local authority (a municipality or county) that establishes the minimum requirements for design, construction, use, renovation, alteration, and demolition of a building and its systems. The intent of a building code is to ensure health, safety, and welfare of the building occupants.

Building codes began as fire regulations written and enacted by several large cities during the 19th century, and have evolved into a code that contains standards and specifications for materials, construction methods, structural strength, fire resistance, accessibility, egress (exiting), ventilation, illumination, energy conservation, and other considerations.

A model building code (i.e., International Building Code, National Electrical Code, and International Mechanical Code) is a standardized document written by a standards writing organization (a group of professionals) and made available for adoption by state and local jurisdictions. A municipality, county, or state may write its own building code, but typically it relies on adoption of model codes as the base of its building code, mainly because it’s easier. Amendments are usually made to the text of a model code to address local issues. Some states adopt a uniform statewide building code while others legally assign code adoption to local authorities (counties and municipalities). Technically, a model building code is not a code (a law) until it’s formally adopted. Model codes are periodically revised, usually every 3 to 5 years, to remain current with advancements and new practices in industry. Each time a model code is revised, it needs to be reviewed and adopted into law by the governmental authority having jurisdiction (control). As a result, different code editions may be in effect in neighboring municipalities at a specific time, which can cause confusion that can lead to design/ construction errors. Professionals in the AEC industry must be come familiar with and maintain a working-level understanding of current codes and standards, and must work hard to keep abreast of revisions in each edition of the code.

TBL P.4 EXAMPLES OF PROFESSIONAL SOCIETIES, TRADE ASSOCIATIONS, GOVERNMENTAL AGENCIES, AND STANDARDS AND CODE-WRITING ENTITIES.

Professional Societies

• American Institute of Architects

• American Society of Heating, Refrigerating and Air-Conditioning Engineers

• American Society of Mechanical Engineers

• American Society of Plumbing Engineers

• American Society of Sanitary Engineering

• Architectural Engineering Institute of the American Society of Civil Engineers

• Association of Energy Engineers

• Illuminating Engineering Society of North America

• National Council of Acoustical Consultants

• National Society of Professional Engineers

• Refrigeration Service Engineers Society

• Society of Fire Protection Engineers

• Society of Women Engineers Standards and Code-Writing Entities

• American National Standards Institute

• American Society of Testing and Materials

• International Association of Plumbing and Mechanical Officials

• International Code Council

• International Fire Code Institute

• National Fire Protection Association

• Underwriters Laboratories Governmental Agencies

• National Institute of Building Sciences

• U.S. Department of Energy

• U.S. Environmental Protection Association

• National Renewable Energy Laboratory Trade Associations

• Air Conditioning Contractors of America

• Air Movement and Control Association

• Air-Conditioning and Refrigeration Institute

• American Boiler Manufacturers Association

• American Gas Association

• American Water Works Association

• Construction Specifications Institute

• Gas Appliance Manufacturers Association

• Heating, Air Conditioning & Refrigeration Distributors International

• Hydronic Heating Association

• International Telecommunications Union

• Mechanical Contractors Association of America

• National Association of Electrical Distributors

• National Association of Home Builders

• National Association of Lighting Management Companies

• National Electrical Contractors Association

• National Electrical Manufacturers Association

• National Fire Protection Association

• National Fire Sprinkler Association

• Plumbing-Heating-Cooling Contractors Association

• Sheet Metal and Air Conditioning Contractors' National Association

• U.S. Green Building Council

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