Site Work and Development

Considerations for Earth sheltering

- minimize earth moving by using a natural slope - granular soil: gravel, sand, and sandy loam. Clay soils are not ideal as they do not drain well and expand with moisture - tested and clear of radon concentrations - groundwater must be below building with positive drainage away from the building - adequate waterproofing of underground portion - insulation to keep indoor temperature comfortable and the prevent condensation from forming on cool inside walls especially in humid environments. - windows to keep adequate ventilation to control humidity and maintain good air quality

Slope of underground pipes (minimum)

0.3%

Steps to construct a green roof over a metal deck

1. Thermal barrier is placed over the metal deck to protect the insulation from heat transfer (required by code) 2. Rigid insulation on top as required by code. Some rigid insulation requires a board to protect it from layers on top. 3. Waterproof membrane placed over the insulation. 4. If required a root barrier is placed on top. 5. Drainage layer on top of root barrier. 6. Growth medium on top.

Steps to construct a green roof over a concrete deck

1. Waterproof membrane over a structural deck 2. Root barrier if necessary (if waterproof membrane is not also root resistant) 3. Rigid insulation is placed over the root barrier. Prevents water stored in growth media from extracting heat from buildings interior during the winter and also provides thermal insulation. 4. Drainage layer to allow for water that is not absorbed by plants and growth media to flow to drains. Slope of structural deck to be at least 1.5% and max of 30% but will require stabilization panels or battens. 5. Filter fabric above drainage to prevent fine particles of soil or growing medium from entering and clogging the drainage layer. 6. Growth medium is placed in thickness from 2 inches to 12 inches or more. Growth medium is an engineered mix of soil and organic material such as peat, sand, lava and expanded clay.

Slope of parking

1.5 to 5% but 2-3% preferred and should drain to perimeter of parking lot.

Slope of paved surfaces (minimum)

1.5%

Glazing factor

A LEED-based number calculated by taking into account window area, floor area, a win- dow geometry factor, light transmission, and a window height factor.

Passive solar system

Collects, stores and distributes solar energy without mechanical equipment

Intensive green roof

Deeper soil of 12 inches or more and support complex landscapes including shrubs and small trees. Can also include ponds and fountains.

Perimeter protection

It is a physical barrier that discourages or prevents unauthorized people or vehicles, or both, from entering the site or getting close to the building. For low-security sites, this may be as simple as a fence; for high-security buildings, it may include holding all unapproved vehicles at a required standoff distance from the building.

Reflective roofing or cool roof

Roof with a light colored material that reflects more of the sun's heat than it absorbs. Minimum reflectivity of 0.65 as new roof and 0.5 after 3 years based on EPA's Energy Star.

drain inlet

an opening in the ground that allows stormwater to run directly into the storm sewer; the opening is usually covered with a metal grate for safety and to keep out debris

Earth sheltering

burying a portion of a building underground. Earth's temperature is cooler in summer and warmer in the winter than air above ground and is also fairly stable. Benefits are: reduces unwanted heat gain/loss Shelter against cold winter winds Natural soundproofing Less outside maintenance Protection from natural threats 3 types: above ground, partially buried, fully buried

external-load dominated building (also called a skin-load dominated building)

is one whose energy use is determined mainly by the amount of heat loss or gain through its exterior envelope. Buildings of this type generally have few occupants per unit area and a small amount of heat gain from lighting, equip- ment, and people. Examples are houses, apartments, condominiums, and warehouses. Cold: cube Temperate: rectangular 1/1.5-2 Hot-humid: elongated rectangle 1/3-4 Hot-arid: courtyard

Diffraction

the bending of sound waves (or other kinds of waves) around the edge of a barrier or through a small opening

visible light transmittance (VLT)

the percentage of visible light that passes through a glazing material.

Conditions for an air barrier to function properly

• The air barrier, assemblies, and whole building must meet the minimum permeance ratings listed above or as prescribed by the local building code. • The air barrier must be continuous around the conditioned spaces, including walls, roof, foundation walls, and slabs on grade. • All joints between materials, components, and assemblies must be sealed. • The air barrier must be securely and tightly joined at other building components such as windows, doors, the roof air barrier component, and foundations. • All penetrations for pipes, ducts, and similar elements must be sealed. • The barrier must be securely attached to the structure to prevent billowing, tearing, or breaking away from attachments and other building components. It must resist the loads on it caused by wind, stack effect, and HVAC systems, both as positive and negative air pressure. • The air barrier at movement joints must be capable of moving with the joint without breaking or tearing. • The air barrier must be durable and last the life of the building, or maintaining it must be possible. • If both a vapor retarder and an air barrier are used and they are separate membranes, the air barrier should be 10 to 20 times more permeable to water vapor diffusion than the vapor retarder, to pre- vent trapping moisture between the two layers.

ADA exterior ramp requirements

1:12 max. slope min. width of 36" 5' landing at top and bottom and max. 30' between landings If rose is greater than 6", provide handrail 34-38" above ramp with 12" extension at top and bottom.

How much does electrical lighting account for in a commercial building

30-40% sometimes 50%

Slope of pedestrian walk

8% (1:12) maximum, 6% preferred outside of buildings, 4% preferred inside buildings

Thermal Storage Wall

A high-mass wall placed directly behind a south-facing glass wall. The high- mass wall collects solar energy during the day for release at night, as a form of direct gain system. Most thermal storage walls are vented, which allows cool air to circulate in the space between the glass and wall, become heated, and travel by convection up and over the wall and back into the space. Ex: Trombe wall

Radiative cooling (nocturnal cooling or night-cooled mass)

A passive or active design strategy that uses thermal mass to collect and store heat during the day for release at night. This works best in climates where there is a significant difference between daytime and nighttime temperatures, such as the southwest and temperate climates.

Altitude

Apparent height of sun Measured as an angle from horizon 0-90 degrees

Earth sheltered- partially excavated

Built into excavated side of a hill. Ideal for buildings in Northern Hemisphere. North side of building built into the hill and the south side is exposed for solar heating, views and daylight. East/west sides may be partially or completely buried

Direct gain systems

Collect heat through south facing glass and then store heat and high mass materials. Glass must be well insulated or low e and have a U-factor 0.35 Btu/ft2-hr-°F

Azimuth

Compass orientation of sun Number of degrees east or west from due south (ex 45 degrees west of south) Number of degrees with due north as 0 (ex 215 degrees)

Flat-plate collector

Consist of a net- work of pipes located on an absorptive black surface with low emissivity, placed below a covering of glass or plastic. The pipes carry the heat transfer medium, which is usually water with antifreeze but can also be another liquid or air.

Climate for cool roof

Cooling degree days exceed heating degree days.

Photovoltaics (PV)

Directly converting sunlight to energy. Photovoltaic (PV) cells are made from various types of semiconductor materials, deposited or arranged on a variety of substrate materials to form flat panels. There are also concentrator systems that focus sunlight on the PV cells to increase energy production, but these are generally limited to use in large-scale power generation.

geothermal energy

Draws on heat sources within the earth. The earth absorbs and holds solar radiation within its great mass, keeping the temperature underground relatively constant year round. In the winter, when the air temperature is colder than the underground temperature, a geothermal system uses the heat in the ground to warm an embedded piping system, transferring the heat to the heating system. In the summer, the underground piping system releases excess heat from the air into the cooler ground. The water is cooled and is used to cool the air in the building.

Greenhouse Design

Features a large glazed area on the south side of the building, with a heavy thermal mass wall separating the greenhouse from the rest of the structure. A rock bed or high thermal mass floor is built in the greenhouse. While the greenhouse often overheats and is subject to heat loss at night, the stored heat circulates into the rest of the building at night.

Earth sheltered- above ground

Fill earth is bermed against the walls on one or more sides

Earth sheltered- fully buried

Fully buried with a courtyard in the middle to allow for access, daylight, an outdoor living area and ventilation

Insulation that uses HCFC and CFC

HCFCs identified as ozone depleting compounds and to be phased up by 2030. CFCs also deplete the ozone and have been phased out since 1996

Shading device for south facing facade

Horizontal louvers or overhangs

Benefits of PV

It reduces demand on nonrenewable energy sources, such as coal- and gas-fired power plants. It can reduce energy costs because the power is generated on site and the excess can, in many states, be sold back to the utility. It produces electricity with no pollu- tion, and the energy captured comes from a free resource.

Disadvantages of Daylighting

Large areas of glazing can lead to glare and unwanted heat gain and heat loss imbalanced lighting can be a problem if side lighting is too strong. because daylighting will not conserve energy if electric lights are used even when natural light is sufficient. Automatic switching is often used to over- come this problem.

Extensive Green Roof

Less than 6 inches deep which is capable of supporting meadow grasses, sedums, herbs and perennials

Location of air barrier

Location doesn't matter for function but for ease of construction typically located behind exterior cladding and outside sheathing which allows ease to install, seal, join to other building components, and properly support. Location remains the same if air barrier is also a vapor barrier. If vapor barrier and air barrier are separately provided, then it depends on climatic region, interior environmental conditions, and the specific construction of the envelope

Growth medium

Material with proper nutritive and drainage characteristics for the proposed plants

ADA curb cutout

Max. Slope of 1:12 Max. Slope at flared side 1:10

Slope of automobile road

Maximum 15% but 10% is preferred. If over 10% then a transition ramp that is 1/2 ramp length at top and bottom.

ADA parking requirements

Min. 8' wide stall 5' (car) or 8' (van) wide access aisle (must be on the passenger side for van ADA parking) Max. Slope for ramp to accessible pathway 1:12 (not allowed for van parking) Signage in front of parking spot with B.O. sign at min. 5' AFF

Cross slope of pedestrian walk

Min. Of 1/4" per foot if non ADA. 1/4" per foot for ADA walk.

Maekawa equation

N= (f/565) (A+B d) f is the frequency of the sound (in hertz), d is the distance (in feet) of the acoustical line of sight from the source of the sound to the receiver, and A + B is the length (in feet) of the shortest path around the barrier, as shown in Fig. 12.23. The Maekawa equation is empirically derived, and units are not consistent. The Maekawa equation is for point sources; for a linear source such as a highway, the noise reduction is about 20% to 25% less than that calculated by the equation.

Air Leakage

Natural air movement in to and out of a building; infiltration/exfiltration caused by differences in pressure between the indoor and outdoor air. These differences can be caused by a combination of wind, the stack effect, the mechanical system in the building, and other factors.

Tinted glass, reflective glass, and heat-absorbing glass

Only reduces solar heat gain but only the visible spectrum. Doesn't allow for use of daylighting to conserve energy and allow for views our (is always darker). Also doesn't allow for use of solar heat gain when it's desirable (winter)

dynamic buffer zone system

Outer layer of glazing built around an existing building. Prevents and controls condensation that may result from remodeling and upgrading the existing building's ventilation, heating, and cooling systems to higher humidity levels. The space between the existing building and the new facade is ventilated with dry, preheated air during winter months.

Air Barrier

Part of a building envelope system that controls infiltration and exfiltration. It consists of materials, components, and assemblies on all vertical and horizontal surfaces exposed to the exterior. An effective air barrier can reduce energy consumption and help keep out pollutants and excess moisture.

Convective loop system or Thermosiphons

Place the solar collector below the inhabited space. The air within the space is circulated by natural convection as the warm air rises and cool air falls back to the collector. The cycle continues indefinitely. Convective loop systems can be used to circulate either air or water

ADA exterior stair requirements

Rise: 4" min and 6" max Tread: 14" min. For 6" rise For areas likely to have ice or more than 4 risers, provide handrail 34-38" above stairs with 12" extensions at top and bottom Tread to have cross slope of 1/4" per foot for drainage

Roof Pond

Stores heat in large water-filled bags on the roof of a building. In winter during the day, the bags heat up. At night, insulation is moved over the roof pond, and the bags release heat down- ward into the building. Can be reversed in the summer. During the day, the bags are covered with insulation so that they absorb heat only from the building. At night, the insulation is removed and the absorbed heat is transferred upward and away from the building.

Green roof (vegetated roof, garden roof or eco-roof)

System of planting containers with soil and vegetation installed on top of a roof Benefits: - energy conservation by reducing cooling and heating loads - reducing storm run off - absorbing carbon dioxide - filtering air and binding dust particles - reducing heat island effect normally by exposed roofing membrane - protecting roofing membranes from ultraviolet light degradation, temperature extremes, wind and hail - adding acoustic insulation - aesthetic appeal to the roof

Electric field vector mapping (EFVM)

Technique to identify leaks in roof gardens. Growth medium is wetted to provide an electrically conductive layer, and the deck is grounded. A leak will cause electric flow from growth medium to deck below and using probes technician can detect precise location.

Solar constant

The amount of solar energy that falls in a unit time on a unit area that is 93,000,000 miles from the sun and oriented on a plane perpendicular to the sun's rays. The mean value of the solar con- stant is 433 Btu/hr-ft2. Some of this energy is lost as the energy travels through the earth's atmosphere

Radiation spectrum

The entire range of electromagnetic radiation extending from 0 Hz to about 1023 Hz. This includes visible light as well as infrared radiation, radio waves, and gamma rays, among others.

Equation of Time

The factor used to account for the difference between solar time and clock time. Solar time is based on the position of the sun. Its basic unit is the solar day, the time the earth takes to make one complete rotation on its axis. A solar day may be slightly more than or less than 24 hours by clock time; its exact length changes from day to day due to the earth's elliptical orbit around the sun and the tilt of the earth's axis. Depending on the time of year, solar days may pass more quickly or more slowly than days on the clock. As the small differences accumulate, solar time can be ahead or behind clock 1 time by as much as about 16.5 minutes. The equation of time is also expressed in the analemma. The difference between solar time and clock time is also affected by one's position east or west within a time zone; this is a separate factor from the equation of time.

analemma

The figure-eight curve that represents the angular offset of the sun from its mean position as viewed from the earth. At any given point on the earth, if the position of the sun is noted at the same time every day for a year, the figure of the analemma is produced.

Solar savings fraction

The fraction of the total energy used by a system that is provided by a solar technol- ogy. The solar savings fraction, represented by the variable f, is a decimal fraction from zero (where no solar energy is used) to one (where all energy used by a system is solar energy).

Movable Insulation

The insulation is removed during sunlight hours and replaced at night or during cloudy weather to prevent heat loss. This type of insulation can be manually operated, power operated, or automated. Common types of movable insulation include roll-down shutters, insulated shades or curtains, swinging panels of insulation, and expanded polystyrene beads blown between panes of glass.

Balance-point temperature

The outdoor temperature at which a building makes a transition from a heating need to a cooling need.

Daylight autonomy

The percentage of an area that meets a minimum daylight illuminance level for a specified fraction of the operating hours per year (e.g., 300 lux for 50% of the time). It is one of the options for receiving LEED credit in the Daylight category.

Daylighting

The placement of windows, reflective surfaces, and other design elements so that natural light can give effective internal lighting during the day.

net metering

The requirement that a utility pay and charge equal rates regardless of which way electricity flows as part of the utility grid. Thus, excess electricity generated with photovoltaics or wind systems can be sold back to the utility.

Solar time

The time as defined by the sun and its position relative to the earth. Because the length of the solar day varies, most references use the mean solar day as a basis for timekeeping. This is the average length of a solar day.

Open loop system

The water is heated directly in the solar collector

Insulating glass (also called double glazing or double-pane glass, or triple glazing or triple-pane glass

This is a glazing assembly in which two or three panes of glass are separated by sealed air spaces or partially evacuated spaces that act as insulators. Using an inert gas in a vacuum compared to air is more efficient

Thermochromic glazing

Type of switchable glazing that changes darkness in response to temperature; it becomes translucent when it reaches a certain temperature. Like photochromic glazing, the change is an inherent property of the material, so this technique offers less control than electrochromic glazing does.

Electrochromic glazing

Type of switchable glazing that consists of a multilayered thin film, applied to glass, that can change between opaque and clear or change colors when a burst of low-voltage electrical current is applied. Once the change has been made, the current does not need to be maintained. This type of glazing allows varia- ble transmittance in the visible portion of the spectrum while reflecting in the infrared spectrum, thereby reducing solar heat gain. The voltage can be controlled manually or automatically

Photochromic glazing

Type of switchable glazing that darkens under the direct action of sunlight. As the light intensity increases, the window becomes darker. Although offering the advantage of automatic action, this type of glazing does not offer the control of electrochromic glazing. For exam- ple, there could be times when clear glazing is desirable, such as on a cold, sunny day.

Transition-metal hydride electrochromics

Type of switchable glazing that makes it possible to have a glazing material that changes from transparent to reflective. These products are based on coatings of nickel-magnesium instead of the oxides used in other electrochromic materials.

Active solar energy systems

Use pumps, fans, ducts, pipes, and other mechanical equipment to collect, store, and distribute solar energy. In order of most common use, active solar systems are used for domestic and process water heating, space heating, space cooling, and electricity generation. Practical generation of electricity is still limited due to the expense of photovoltaic (PV) cells, but this is slowly changing as more efficient and economical PV cells are developed. A typical active solar system requires three components: a collector, a storage device, and a distribution system

Shading device for east and west facade

Vertical louvers

Air locks

Vestibule entry system or revolving doors that limit cold drafts from coming in as well as reduces heat loss.

Ground light

Visible light from the sun and sky, reflected by exterior surfaces below the plane of the horizon.

Flood test

Way to verify watertightness. Area is flooded with 2 inches of water for 48 hours and the building interior is inspected for leaks.

crown

a gradual cross slope for drainage from the center of the roadway to the sides. This slope should be a minimum of 1 4 in/ft

light shelf

a horizontal surface placed above eye level that reflects direct daylight onto the ceiling while shading the lower portions of the window and the interior of the room. A light shelf also has the desirable effect of distributing the light more evenly from the window to the back of the room

vapor-impermeable barrier

acts as both an air barrier and a vapor retarder in the same material. Vapor transmission can be caused by diffusion through materials

solar heat gain coefficient (SHGC)

amount of solar radiation that is transmitted through the entire window assembly, expressed as a fraction of the total amount that strikes it. The SHGC is a decimal fraction between zero and one; a value of one would indicate a window assembly that lets all solar radiation pass through, and a value of zero would indicate a window assembly that lets none pass through.

catch basin

an underground reservoir that has a sump built into it; debris settles into the sump instead of flowing down the sewer and potentially clogging the pipes.

Closed loop system

antifreeze or some other transfer medium is heated in the collector and circulated to a heat exchanger, where the domestic water is heated by the transfer medium. This allows use of a nontoxic chemical that facilitates the heat transfer but guarantees that it will be kept sepa- rate from the domestic water supply.

Switchable glazings

are chromogenic window that change their characteristics based on particular environmental conditions or through human intervention.

Focusing collector

are parabolic reflectors that focus the incoming radiation to a single pipe that carries the heat-transfer medium. Because the reflectors direct the sun's energy to a specific point, focusing collectors operate at a much higher temperature than flat-plate collectors. However, they must be continuously aimed at the sun for maximum benefit, so they are usually attached to mechanisms that automatically track the sun's path.

Phase change materials

are used to avoid the overheating and wide swings in temperatures that can occur with concrete, masonry, and water. Eutectic salts that change from a solid to a liquid at a fairly low temperature, around 70°F, are commonly used phase change materials. They store large amounts of heat because they also store latent heat as they undergo the phase change from solid to liquid. At night, the heat is released as they again change state, from liquid back to solid.

Storm drains

collect water from roof downspouts, drain inlets, catch basins, and drain tiles surrounding the building foundation

holding pond

collects the site run- off and releases it into the sewer system at a controlled rate; it also prevents excess water from flooding other areas

stack effect (or chimney effect)

difference in pressure between the top and bottom of a building due to a temperature differential. The effect is most pronounced in high-rise buildings. In a cold climate, air will be warmer in the upper part of the building and cooler in the lower part, which causes exfiltration at the top and consequently infiltration near the ground to replace the lost air.

Low-ε glass, also known as low-emissivity glass

double glazing that includes a thin film or coating placed somewhere in the glazing cavity. The film or coating allows both visible and near-infrared radiation to be transmitted through the glass. However, as objects in the room are heated and emit long- wave radiation, the film or coating prevents the loss of this heat; instead, the heat is reflected back into the room.

ground-source heat pumps (GSHPs)

electrically powered systems that work like air-source heat pumps by either extracting heat from the ground in winter or giving off excess heat to the ground in summer. Within a GSHP, the heat from the ground is increased through a vapor- compressor refrigeration cycle. Features assemblage of durable plastic pipes buried in the ground. The pipes can be arranged either vertically or horizontally depending on the space available and the geology of the site. About 400 ft of pipe is required for every 12,000 Btu/hr of heating or cooling capacity needed. For heating, water is pumped through the plastic tubing in the earth to the heat pump, where the water's heat is increased. The GSHP can then be used to preheat water or exchange heat in a water-water or water-air heat exchanger. The cycle is reversed for cooling. GSHPs can be used for space heating and cooling and for preheating water for domestic hot water. They can reduce energy consumption of space heating and cooling by 20% to 50% and use up to 50% less energy for water heating.

Super windows

glazing units that combine two low-ε coatings with gas-filled cavities between three layers of glass. With a U-value of 0.15 Btu/ft2-hr-°F or less, these units can gain more thermal energy than they lose over a 24-hour period in winter.

Disadvantages of PV

high initial cost, the need for collectors to be placed in a location that receives adequate sunlight, low winter pro- duction, and the lack of electricity production during night hours. Battery storage is also high in initial cost and requires space to store the battery.

vapor-permeable barriers

include relatively thin sheets of spunbonded polyolefin (house wrap), polyethylene, elastomeric coatings, liquid applied spray-on or trowel-on materials, self-adhesive membranes, various types of sheathing sealed with tape, silicon-based materials, fluid-applied products, and combinations of these materials.

Top lighting

involves the use of light pipes, skylights, roof monitors, saw-toothed roofs, or sloped glazing. An additional, overhead source of daylight helps distribute the light evenly and provide daylight to a larger portion of the building. Top lighting works only in one-story buildings, low-rise stepped-back buildings, on the top floor of multistory buildings, and in buildings with one or more large, skylit atriums.

internal-load dominated building

is one whose energy use is driven by high heat gain from occupants, lighting, and equipment. Buildings of this type include office buildings, hospitals, retail stores, schools, and laboratories. Cold: cube Temperate: rectangular Hot-humid: elongated rectangle 1/3-4 Hot-arid: rectangular

Permeance

measure of how readily a material or membrane allows water vapor to pass through it. The unit of permeance is the perm, which is one grain of moisture per hour per square foot per inch of mer- cury difference in vapor pressure (1 perm = 1 g/hr-ft2-in Hg). If an air barrier is vapor permeable, it should have a permeance rating of 5 perms or greater.

Storm sewer systems

must have manholes for service access; these are located wherever the sewer changes direction, or a maximum of 500 ft apart. Storm sewers are always completely separate from sanitary sewer systems.

Underground drainage systems

perforated drains and enclosed storm sewers to carry the run- off from the site, either to a municipal storm sewer system or to a natural drainage outlet such as a river

Aboveground drainage systems

pervious paving, sheet flow, gutters built into roadways and parking areas, ground swales as part of the land- scaping, and channels to manage runoff and direct it appropriately

Transparent insulation

polycarbonate honeycomb material, acrylic foam, or fiberglass sandwiched between layers of glazing. It is used to admit light while providing a high degree of insulation. It can also be used over another thermal mass material to trap solar heat and then slow the loss of the stored heat back into the atmosphere. Although good for diffusing light, transparent insulation cannot be used where a view is desired.

shading coefficient (SC)

ratio of the amount of solar radiation that passes through a piece of glass to the amount that would pass through a similar piece of unshaded, clear, double-strength glass 1/8 in thick under the same conditions. Like the SHGC, the SC is a decimal fraction between zero and one. Not really used in US

Light pipes

round or square tubes with highly reflective interior coatings. They extend from the roof to the space to be lighted. Sunlight is captured through a clear plastic dome and directed down to a translucent diffusing plate at the bottom.

Indirect gain systems

similar to direct gain systems except that the thermal mass is not in direct sunlight. Rather, the mass is heated during the day by room air temperature and reflected sunlight. Not as efficient as direct gain system (only captures about 25%)

run-off

stormwater that accumulates on the site in excess of what can be absorbed by the ground

Superinsulation

technique of providing higher levels of insulation than normally used, tightly sealing all joints and cracks, and preventing any thermal bridges between the outside and inside, such as through studs. All portions of the building are carefully detailed so that every piece is insulated. Gaps, such as electrical outlets on exterior walls, are avoided or placed inside the insulation. In many cases, exterior walls have to be made thicker than would otherwise be needed to accommodate the added insulation. For homes, this includes using 2 × 6 studs instead of 2 × 4 studs.

window-to-wall ratio (WWR)

the net glazing area in a room or space divided by the gross exterior wall area. It does not include window frames or mullions.

Double envelope system

the outer skin of a building consists of two glazed layers that are typically separated by about 2 ft to 3 ft. Some type of sun control (louvers, blinds, or shades) and either a passive or active ventilation system is incorporated within this space. The system may include devices to redirect sunlight so as to enhance daylighting of the interior spaces. Outer layer moderates effects of environment Cavity can exhaust excessive heat buildup directly to the outside in hot weather, or it can be redirected to a heat exchanger to warm incoming air in cold weather. reduced cooling loads, enhanced sun control, reduced operating costs, optimized daylighting, and enhanced air quality when natural ventilation is used.

Daylight Factor (DF)

the ratio of the illuminance at a point on a horizontal surface indoors to the illuminance at a point on a horizontal surface outdoors and fully open to the sky, measured at the same time under overcast skies; direct sunlight is excluded. The DF is expressed as a percentage, but the percent sign is sometimes omitted (for example, a DF of 2% is sometimes expressed as a DF of 2).

Capacity of drainage system is based on

the size of the area to be drained, the runoff coeffi- cient (that fraction of water not absorbed), and the amount of water to be drained during the most severe storm anticipated by the design.

Spectrally selective glazing

transmits a high proportion of the visible solar spectrum while blocking up to 80% of the heat from the infrared portion of the spectrum. Especially good for buildings that have a long cooling season and that need high interior light levels.

sound barriers

wall barriers constructed of wood or concrete blocks, or earth berms. A barrier does not completely stop sound transmission; sound will travel over and around it through diffraction

Storage devices for active solar energy systems

water for water systems and rock beds for air systems. Phase change materials can also be used, but they are more expensive.

Sheet flow

water that drains across a sloping surface, whether that surface is paved, grassy, or otherwise landscaped. In most cases, sheet flow is directed to gutters or channels, which empty into a natural watercourse or storm sewer

Air leakage in a building is bad because...

• Air that enters through infiltration rather than through the ventilation system must still be condi- tioned to meet indoor requirements, which adds to the building's heating or cooling load. Typically, 25% to 40% of the heating and cooling energy used by a building is lost due to infiltration. • Similarly, conditioned air from within the building can be lost to exfiltration. • Infiltration carries dust and pollutants into the building. • Infiltration carries water vapor into the building, which can condense and contribute to mold growth and the degradation of building materials.