Scofield considered source energy accounting for energy losses during generation and transmission as well as site energy , and used area-weighted energy use intensities, or EUIs energy per unit area per year , when comparing LEED and non-LEED buildings to account for the fact that larger buildings tend to have larger EUIs. In , Fuertes and Schiavon  developed the first study that analyzes plug loads using LEED documented data from certified projects. In general, energy modelers considered the energy consumption of plug loads of equipment that are constantly running such as refrigerators as well as monitors and computers predictable.
Overall the results suggested a disconnection between energy modelers assumptions and the actual performance of buildings. Energy model might be a source of error during LEED design phase. Stoppel and Leite  evaluated the predicted and actual energy consumption of two twin buildings using the energy model during the LEED design phase and the utility meter data after one year of occupancy. According to Newsham et al.
Newsham et al. In consideration of a building's indoor environmental quality, published studies have also included factors such as: acoustics, building cleanliness and maintenance, colors and textures, workstation size, ceiling height, window access and shading, surface finishes, and furniture adjustability and comfort. In , a paper published by S. Schiavon and S. These factors include the ease of interaction, building cleanliness, the comfort of furnishing, the amount of light, building maintenance, colors and textures, workplace cleanliness, the amount of space, furniture adjustability, visual comfort, air quality, visual privacy, noise, temperature, and sound privacy.
The results showed occupants tend to be slightly more satisfied in LEED buildings for the air quality and slightly more dissatisfied with the amount of light. The overall finding was that there was no significant influence of LEED certification on occupant satisfaction in consideration of the overall building and workspace ratings. Based on similar dataset 21, occupants , in , Schiavon and Altomonte,  found that occupants have equivalent satisfaction levels in LEED and non-LEED buildings when evaluated independently from the following nine factors: 1 office type, 2 spatial layout, 3 distance from windows, 4 building size, 5 gender, 6 age, 7 type of work, 8 time at workspace, and 9 weekly working hours.
LEED certified buildings may provide higher satisfaction in open spaces than in enclosed offices, in smaller buildings than in larger buildings, and to occupants having spent less than one year in their workspaces rather than to those who have used their workspace longer. The study also points out that the positive value of LEED certification from the aspect of occupant satisfaction may tend to decrease with time. In , a study on indoor environmental quality and the potential health benefits of green certified buildings was developed by Allen et al.
One of the limitations of the study was the use of subjective health performance indicators since there is a lack of definition on such indicators by current studies. On-site, workstations were measured for thermal conditions, air quality, acoustics, lighting, workstation size, ceiling height, window access and shading, and surface finishes.
Responses were positive in the areas of environmental satisfaction, satisfaction with thermal conditions, satisfaction with view from the outside, aesthetic appearance, reduced disturbance from heating, ventilation and air-conditioning noise, workplace image, night-time sleep quality, mood, physical symptoms, and reduced number of airborne particulates. The results showed green buildings exhibited superior performance compared with similar conventional buildings. Current latest study published in , by Altomonte, Schiavon, Kent and Brager, specifically investigated whether a green rating leads to higher occupant satisfaction with IEQ.
In addition, the rating level and version of the certification has no impact on workplace satisfaction.
There are some possible explanations. Many intervening factors in the time between design and occupancy can alter the existence or performance of the strategies that LEED awarded.
Survey participants may also misinterpret the satisfaction with an IEQ parameter, or bias with personal attitudes. SDA is a metric that measures the annual sufficiency of daylight levels in interior spaces and ASE describes the potential for visual discomfort by direct sunlight and glare. According to Reinhart  the direct sunlight requirement is a very stringent approach that can disable good daylight design from achieving this credit. Reinhart propose the application of the direct sunlight criterion only in spaces that require stringent control of sunlight e.
However, it also attributed substantial benefits to the increased productivity from the better ventilation, temperature control, lighting control, and reduced indoor air pollution.
From a purely financial perspective, in several studies found that LEED for-rent office spaces generally charged higher rent and had higher occupancy rates. CoStar Group collects data on properties. LEED focuses on the design of the building and not on its actual energy consumption, and therefore it has suggested that LEED buildings should be tracked to discover whether the potential energy savings from the design are being used in practice. The U. Green Building Council provides an online directory of U.
LEED-certified projects. It provides searchable access to a database of activities, buildings, places and collections of green building-related information from many sources and programs, as well as, specifically provides information about LEED projects. They show differentiation in a growing and competitive industry, and they allow for varied levels of specialization. A LEED Professional Credential provides employers, policymakers, and other stakeholders with assurances of an individual's level of competence and is the mark of the most qualified, educated, and influential green building professionals in the marketplace.
LEED certified buildings are intended to use resources more efficiently when compared to conventional buildings simply built to code.
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However, analysis of energy and water use data from New York City shows that LEED certification does not necessarily make a building more energy or water efficient. Often, when a LEED rating is pursued, the cost of initial design and construction rises. There may be a lack of abundant availability of manufactured building components that meet LEED specifications. Pursuing LEED certification for a project is an added cost in itself as well.
However, these higher initial costs can be effectively mitigated by the savings incurred over time due to the lower-than-industry-standard operational costs typical of a LEED certified building. This Life cycle costing is a method for assessing the total cost of ownership, taking into account all costs of acquiring, owning and operating, and the eventual disposal of a building. Additional economic payback may come in the form of employee productivity gains incurred as a result of working in a healthier environment.
Further, the USGBC has stated support for the Architecture , an effort that has set a goal of using no fossil-fuel, greenhouse-gas-emitting energy to operate by LEED is a design tool and not a performance measurement tool. It is also not yet climate-specific, although the newest version hopes to address this weakness partially.
Because of this, designers may make materials or design choices that garner a LEED point, even though they may not be the most site- or climate-appropriate choice available. On top of this, LEED is also not energy-specific. Since it only measures the overall performances, builders are free to choose how to achieve points under various categories.
A USA Today review showed that 7, certified commercial building projects targeted easy and cheap green points, such as creating healthy spaces and providing educational displays in the building. Builders game the rating system and use certain performances to compensate for the others, making energy conservation the weakest part in the overall evaluation. LEED is a measurement tool for green building in the United States and it is developed and continuously modified by workers in the green building industry, especially in the ten largest metro areas in the U.
For instance, a building in Maine would receive the same credit as a building in Arizona for water conservation, though the principle is more important in the latter case. Another complaint is that its certification costs require money that could be used to make the building in question even more sustainable. Many critics have noted that compliance and certification costs have grown faster than staff support from the USGBC.
These costs should be significantly reduced if automation and technology are integrated into the implementation. Many federal, state, and local governments and school districts have adopted various types of LEED initiatives and incentives. A full listing of government and school LEED initiatives can be found online  and is updated regularly. In the state of Nevada , construction materials for a qualifying LEED building are exempt from local taxes.
Pieces of construction that are deemed "inseparable" parts, such as concrete or drywall , qualify. The state of Maryland passed its High Performance Buildings Act in , requiring all new public construction and renovation of buildings greater than 7, square feet to meet at least the LEED Silver standard, or two Green Globes. Between and , the state is required to fund half of the required additional cost for public school construction or renovation to attain that standard.
Many local governments have adopted LEED incentive programs. Program incentives include tax credits, tax breaks, density bonuses, reduced fees, priority or expedited permitting, free or reduced-cost technical assistance, grants and low-interest loans. The Philip Merrill Environmental Center is recognized as one of the "greenest" buildings ever constructed in the United States at the time when it was built. Sustainability issues ranging from energy use to material selection were given serious consideration throughout design and construction of this facility.
Of these, the calculation method is an economical and commonly used method of determining concrete masonry fire resistance ratings. The calculations are based on extensive research, which established relationships between the physical properties of materials and the fire resistance rating. The calculation method is fully described in the Standard and IBC Section , and determines fire resistance ratings based on the equivalent thickness of concrete masonry units and the aggregate types used in their manufacture.
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Private commercial listing services allow the designer to select a fire rated assembly that has been previously tested, classified and listed in a published directory of fire rated assemblies. The system also is somewhat inflexible in that little variation from the original tested wall assembly is allowed, including unit size, shape, mix design, constituent materials, and even the plant of manufacture. For prescriptive designs, the IBC provides a series of tables that describes requirements of various assemblies to meet the fire resistance ratings specified.
The last two options listed above require justification to the building official that the proposed design is at least the equivalent of what is prescribed in the code. The calculated fire resistance method is based on extensive research and testing of concrete masonry walls. The fire resistance rating of concrete masonry is typically governed by the heat transmission criteria. From the standpoint of life safety particularly for fire fighters and salvageability, this failure mode is certainly preferable to a structural collapse endpoint, characteristic of many other building materials.
The calculated fire resistance rating information presented here is based on the IBC and the Standard refs. Extensive testing has established a relationship between fire resistance and the equivalent solid thickness of concrete masonry walls, as shown in Table 1. Equivalent thickness is essentially the solid thickness that would be obtained if the volume of concrete contained in a hollow unit were recast without core holes see Figure 1.
For partially grouted walls where the unfilled cells are left empty, the equivalent thickness for fire resistance rating purposes is equal to that of an ungrouted unit.
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For partially grouted walls with filled cells, see the following section. Typical equivalent thickness values for these units are listed in Table 2. If all cells of hollow unit masonry are filled with an approved material, the equivalent thickness of the assembly is the actual thickness. This also applies to partially grouted concrete masonry walls where all ungrouted cells are filled with an approved material.
Applicable fill materials are: grout, sand, pea gravel, crushed stone, or slag that comply with ASTM C33 ref. The fire resistance rating is determined in accordance with Table 1 utilizing the appropriate aggregate type used in the masonry unit and the equivalent thickness.