Accessibility Guidelines ARCH 40411 Fall 2024 PDF

Accessibility ARCH 40411 FALL 2024 Chapter 11 Accessibility The IBC contains scoping provisions for accessibility...

Accessibility ARCH 40411 FALL 2024 Chapter 11 Accessibility The IBC contains scoping provisions for accessibility (for example, what, where The fundamental philosophy of the and how many), code on the subject of accessibility is that everything is required to be accessible. The code’s scoping requirements then address the conditions under which accessibility is not required in terms of The ICC A117.1, Accessible and exceptions to this general mandate. Usable Buildings and Facilities, is the referenced standard for the technical provisions (in other words, how) Accessible Route An accessible route is a continuous, unobstructed path connecting all accessible elements and spaces in a building, facility, or site. At least 1 accessible route (36” min. width) is required to connect all accessible facilities on a site: Accessible Entrances The current requirement requires 60% of public entrances to be accessible, plus additional entrances so the total number of accessible public entrances is equal to the number of required exits (based on building or fire codes; typically two), but not exceeding the total number of planned public entrances.  Section 406 Curbed Ramps Flared sides 1:10 max. slope 406.2 Counter Slope Counter slopes of adjoining gutters and road surfaces immediately adjacent to the curb ramp shall not be steeper than 1:20. The adjacent surfaces at transitions at curb ramps to walks, gutters, and streets shall be at the same level. 406.3 Sides of Curb Ramps At least as wide Where provided, curb ramp flares shall not be steeper than 1:10. as curb ramp 406.4 Landings Landings shall be provided at the tops of curb ramps. The landing clear length shall be 36 inches (915 mm) minimum. The landing clear width shall be at least as wide as the curb ramp, excluding flared sides, leading to the landing. EXCEPTION: In alterations, where there is no landing at the top of curb ramps, curb ramp flares shall be provided and shall not be steeper than 1:12. Curbed Ramps 406.6 Diagonal Curb Ramps Diagonal or corner type curb ramps with returned curbs or other well-defined edges shall have the edges parallel to the direction of pedestrian flow. The bottom of diagonal curb ramps shall have a clear space 48 inches (1220 mm) minimum outside active traffic lanes of the roadway. Diagonal curb ramps provided at marked crossings shall provide the 48 inches (1220 mm) minimum clear space within the markings. Diagonal curb ramps with flared sides shall have a segment of curb 24 inches (610 mm) long minimum located on each side of the curb ramp and within the marked crossing. Accessible Routes Walking surfaces with a running slope not steeper than 1:20, and 36” min. wide  Walking Surface The clear width of walking surfaces shall be 36” min. EXCEPTION: The clear width shall be permitted to be reduced to 32 inches (815 mm) minimum for a length of 24 inches maximum provided that reduced width segments are separated by segments that are 48 inches long minimum and 36 inches wide minimum. Walking Surface 403.5.2 Clear Width at Turn Where the accessible route makes a 180 degree turn around an element which is less than 48 inches (1220 mm) wide, clear width shall be 42 inches (1065 mm) minimum approaching the turn, 48 inches (1220 mm) minimum at the turn and 42 inches (1065 mm) minimum leaving the turn. EXCEPTION: Where the clear width at the turn is 60 inches (1525 mm) minimum compliance with 403.5.2 shall not be required. Section 303 Change in Level 303.2 Vertical Changes in level of ¼” maximum in height shall be permitted. 303.3 Beveled Changes in level greater than ¼” in height and not more than ½” maximum in height shall be beveled with a slope of not steeper than 1:2 304.2 Floor or Ground Surfaces EXCEPTION: Slopes not steeper than 1:48 shall be permitted. Section 303 Change in Level Threshold condition Transition between floor finishes Section 304 Turning Clearances 304.3.1 Circular Space The turning space shall be a space of 60 inches diameter minimum. 304.3.2 T-Shaped Space The turning space shall be a T-shaped space within a 60 inch square minimum with arms and base 36 inches wide minimum. Each arm of the T shall be clear of obstructions 12 inches minimum in each direction and the base shall be clear of obstructions 24 inches minimum. 304.4 Door Swing Doors shall be permitted to swing into turning spaces. Clear Floor Space 305.3 Size The clear floor space shall be 48” minimum in length and 30” width Floor space is permitted to include knee and toe clearances Floor space shall be positioned for either forward or parallel approach Clear Floor Space 305.5 Position Unless otherwise specified, clear floor or ground space shall be positioned for either forward or parallel approach to an element. 305.6 Approach One full unobstructed side of the clear floor or ground space shall adjoin an accessible route or adjoin another clear floor or ground space. Clear Floor Space 305.7 Maneuvering Clearance Where a clear floor or ground space is located in an alcove or otherwise confined on all or part of three sides, additional maneuvering clearance shall be provided in accordance with 305.7.1 and 305.7.2. 305.7.1 Forward Approach Alcoves shall be 36 inches wide minimum where the depth exceeds 24 inches. Section 306 Knee and Toe Clearance 306.1 General Where space beneath an element is included as part of clear floor or ground space or turning space, the space shall comply with 306. Additional space shall not be prohibited beneath an element but shall not be considered as part of the clear floor or ground space or turning space. Protruding Objects Objects with leading edges more than 27 inches and not more than 80 inches above the finish floor or ground shall protrude 4 inches maximum horizontally into the circulation path. EXCEPTION: Handrails shall be permitted to protrude 4 1/2 inches maximum.  Protruding Objects Vertical clearance shall be 80 inches high min. Guardrails or other barriers shall be provided where the vertical clearance is less than 80 inches high. The leading edge of such guardrail or barrier shall be located 27 inches maximum above the finish floor or ground. EXCEPTION: Door closers and door stops shall be permitted to be 78 inches minimum above the finish floor or ground. Reach Ranges Reach Ranges 308.3.2 Obstructed High Reach Where a clear floor or ground space allows a parallel approach to an element and the high side reach is over an obstruction, the height of the obstruction shall be 34 inches maximum and the depth of the obstruction shall be 24 inches maximum. The high side reach shall be 48 inches maximum for a reach depth of 10 inches maximum. Where the reach depth exceeds 10 inches, the high side reach shall be 46 inches maximum for a reach depth of 24 inches maximum. Doors, Doorways and Gates Door openings shall provide a clear width of 32 inches minimum. Clearances at Doors in a series Door Hardware The force for pushing or pulling open a door or gate other than fire doors shall be as follows: 1. Interior hinged doors and gates: 5 pounds max. 2. Sliding or folding doors: 5 pounds max. Maneuvering Clearances without Doors  Ramps 405.2 Slope Ramp runs shall have a running slope not steeper than 1:12. 1” rise needs 1’-0” run If 24” rise , then 24’-0” length of ramp needed 405.3 Cross Slope Cross slope of ramp runs shall not be steeper than 1:48. 405.5 Clear Width The clear width of a ramp run and, where handrails are provided, the clear width between handrails shall be 36 inches minimum. Maximum length of ramp without a landing is 30’-0”  Ramps 405.6 Rise The rise for any ramp run shall be 30 inches maximum. Maximum length of ramp without a landing is 30’-0” If 36” rise, then need 30’-0” run plus 5’-0” min, landing plus 6’-0” ramp = 41’-0” total length. 405.7 Landings Ramps shall have landings at the top and the bottom of each ramp run. Landings shall comply with 405.7. Handrails Handrails at Stairs Handrails at Stairs Handrails shall be continuous within the full length of each stair flight or ramp run. Inside handrails on switchback or dogleg stairs and ramps shall be continuous between flights or runs. EXCEPTION: In assembly areas, handrails on ramps shall not be required to be continuous in aisles serving seating. Mounting Heights Heating Ventilation and Air Conditioning A R C H 4 0 41 1 FA L L 2 0 24 HVAC systems Heating the technology of indoor environmental comfort. Ventilation Its goal is to provide thermal comfort and acceptable indoor air quality. Air Conditioning  ASHRAE 62.1 ASHRAE was formed as the American Society of Heating, Refrigerating and Air-Conditioning Engineers by the merger in 1959 of American Society of Heating and Air-Conditioning Engineers (ASHAE) founded in 1894 and The American Society of Refrigerating Engineers (ASRE) founded in 1904. A global society advancing human well-being through sustainable technology for the built environment. Its primary focus is on building systems, energy efficiency, indoor air quality, refrigeration and sustainability within the industry, through its continued research, standards writing, publishing and continuing education programs. ASHRAE 90.1  Commercial Buildings Energy Code Most states have adopted an energy code which is based on the national model energy codes–the International Energy Conservation Code (IECC) for residential buildings and Standard 90.1 for commercial buildings (42 USC 6833). Always verify jurisdiction and applicable codes State Portal | Building Energy Codes Program Operating Costs 23% 51% Percentage of operating 12% costs which are associated 19% with repairs, maintenance, energy and utilities Repairs/Maintenance 18% Energy/Utilities Cleaning Administrative 28% Roads/Grounds/Security How can we stay warm? What is the greatest source for heat  Cooling System In the 1840s, physician and inventor Dr. John Gorrie of Florida proposed the idea of cooling cities to relieve residents of "the evils of high temperatures." Gorrie believed that cooling was the key to avoiding diseases like malaria and making patients more comfortable, but his rudimentary and expensive system for cooling hospital rooms required ice to be shipped to Florida from frozen lakes and streams in the northern United States. Gorrie began experimenting with the concept of artificial cooling. He designed a machine that created ice using a compressor powered by a horse, water, wind-driven sails or steam.  Cooling System 1851 John Gorrie granted a patent on refrigeration system 1880 used in industrial settings primarily for ice and freezers for meat 1890s interest shifted to transform cooling to serve buildings 1902: New York Stock Exchange one of the first building  Cooling System At the St. Louis World's Fair in 1904, organizers used mechanical refrigeration to cool the Missouri State Building. The system used 35,000 cubic feet of air per minute to cool the 1,000-seat auditorium, the rotunda and other rooms within the Missouri State Building. It marked the first time the American public was exposed to the concept of comfort cooling. General public first experienced comfort cooling technology came in the 1920s, (movie theaters)  Cooling Systems Post-war era: central air conditioning, and window air conditioners which in turn created population growth in hot-weather states like Arizona and Florida by the late 1960s. 90% 1920s - 1960s: homes with some form of Mechanical refrigeration use was limited. air conditionings One ton is equal to the heat absorbed in melting 2,000 pounds (1 ton) of ice at 32 F in 24 hours Key Influences in the development of HVAC Thermodynamics Fluid Mechanics Allowed HVAC systems to develop and Electricity Construction improved our understanding of the impact of the Materials environment to a building and its occupants. Medicine Controls Social Behavior  ASHRAE Indoor Air Quality 62.1 Indoor Air Quality Rise in Asthmatics Increase dissatisfaction with indoor air quality in buildings and airplanes Healthcare Pandemic Cause and effect are complex  ASHRAE Indoor Air Quality 90.1 Energy Conservation Consumption without compromising comfort an indoor air quality. Requires significant cooperation between disciplines that design buildings  Heating Human Comfort Air Movement Cooling Human Comfort Filtration Humidification Ventilation Dehumidification  Human Comfort Heating: Air Cooling Movement Heating: the process of adding thermal Human energy(heat) to the air in the conditioned Comfort Filtration: Humidification space for the purpose of raising or maintaining the temperature of the space. Ventilation Dehumidification  Human Comfort Heating: Air Cooling Movement Cooling: the process of removing thermal Human energy(heat) to the air in the conditioned Comfort Filtration: Humidification space for the purpose of raising or maintaining the temperature of the space. Ventilation Dehumidification  Human Comfort Heating: Air Cooling Movement Humidification: the process of adding water vapor to the Human air in the conditioned space to raise or Comfort Filtration: Humidification maintain the moisture content of the air. Ventilation Dehumidification  Human Comfort Heating: Air Cooling Movement Dehumidification: the process of removing water vapor to Human the air in the conditioned space to Comfort Filtration: Humidification decrease or maintain the moisture content of the air. Ventilation Dehumidification  Human Comfort Heating: Air Cooling Movement Ventilation: the process of exchanging air between Human the outdoors and the conditioned space Comfort Filtration: Humidification to dilute the gaseous contaminant in the air and improve or maintain air quality. Ventilation Dehumidification Ventilation is always required ▪ Natural or mechanical  Human Comfort Heating: Air Cooling Movement Filtration: the process of removing particulates and Human Comfort biological contaminants from the air Filtration: Humid- ification delivered to the conditioned space to improve air quality. Dehumid- Ventilation ification  Human comfort Heating: Air Cooling Movement Air Movement: the process of circulating and mixing air Human through conditioned spaces in the building for Comfort Filtration: Humidification the purposes of achieving the proper ventilation in the space breathing zone and facilitating faster thermal energy transfer. Ventilation Dehumidification  HVAC System Selection Must consider many items beyond just comfort within the space that is being design. Fundamentals of system design Operations Maintenance One must fully understand the objectives of the system and the space it is serving  Key Factors to Consider Key factors in selecting most suitable systems Number of Occupants Building Materials Orientation Functional Use of Space Hours of Operations Fresh air Requirements Equipment Selection Maintenance and Operations Human Comfort Acceptable Standards 80% Thermal comfort standards. Percentage of occupants that are satisfied ASHARE 55 is the Standard for Thermal Comfort defines acceptable conditions for occupants Human Comfort Influencing Factors 1. Thermal and Humidity Condition 2. Air Quality 3. Acoustic Environment 4. Lighting 5. Physical Aspects 6. Psychosocial Situation Human Comfort Influencing Factors 1. Thermal and Humidity Condition 2. Air Quality 3. Acoustic Environment 4. Lighting 5. Physical Aspects 6. Psychosocial Situation Human Comfort Temperature and Humidity Standards: ASHRAE 55 Temperature: 75 degrees 1. Temperature and Humidity Relative Humidity 50% ▪ Acceptance of slightly lower temperature if humidity is slightly elevated If temperature is at an acceptable level and the humidity is then space will seem too warm. Due to rate of evaporation of moisture from the body Human Comfort Thermal and Humidity Control More than simple air temperature Air flow is impacted by speed of air, pressure, air density and temperature. If Air Flow ▪ Too high- drafty Occupant will sense discomfort if ▪ Too low: stagnant and stuffy above 30 fpm in winter above 50 fpm in summer  Human Comfort Radiant Temperature Radiant Temperature of Architectural Components Impacts human comfort regardless of temperature of the space Windows and fenestration Occupant will feel warmer if sun is shining in If temperature outside is colder, heat radiated from body to cooler surface and thus feel discomfort Radiant Heat Horizontal sun: most effective on south facing facades Vertical: most effective on east and west facades None: northern facades Human Comfort Air Quality Air Quality Affected by pollution form occupants Affected by contents of the space Amount of outside air that is brought into space will dilute pollutants and improve indoor air quality. Densely occupied spaces and spaces where heavy polluting activities are present require a much higher amount of outside air and greater air changes per hour. Human Comfort ASHRAE 62.1 Air Quality Air Quality Affected by pollution form occupants Affected by contents of the space Amount of outside air that is brought into space will dilute pollutants and improve indoor air quality. Densely occupied spaces and spaces where heavy polluting activities are present require a much higher amount of outside air and greater air changes per hour. Human Comfort Air Quality Indoor Air Quality (IAQ) Directly impacted by the quality of outside air. Filtration ▪ may be required if outside air contains pollutants Human Comfort Lighting All lights give off heat which directly impacts the cooling system of a space. Perception of comfort. ▪ Too bright: glare, eye stain ▪ Lower light levels: occupants may struggle to read or perform fine motor skills. Results in eye stain and potential headaches Human Comfort Physical Aspects ▪ Architectural Design ▪ Forms ▪ Spatial Volume ▪ Interior Deign ▪ Furniture ▪ Height of workspace ▪ Reflections ▪ Color selections ▪ warm and cool palette ▪ bold, primary palette Human Comfort Psychosocial Situation Interaction of people within a space can impact human comfort. Adjacencies Undesired transmission and distractions from an adjacent space Function use of space Other people, close proximity Loud talkers Odors Human Comfort Acoustical Environment Undesired transmission of noise generating activities within space Form adjacent space Froom outdoors Equipment HVAC system  Human Comfort Acoustical Environment Design Requirements defined by Noise Criteria (NC) Logarithmic sum of noise level in eight octave bands, measured in decibels. ‘White Noise’ low levels of constant noise Varying levels or intermediate can be detrimental Specialty Spaces: recording studio, church, performing arts  Human Comfort Individual Aspects Health ▪ Age, healthy, well-being Vulnerability ▪ Clothing (light weight in conditioned space) Expectations Preconceived opinions base don visual perception of past experience  Human Comfort Clothing and Activity Level Clothing : Can directly affect thermal comfort Lighter clothing, less insulting value, increased loss in body heat Heavier clothing- more insulating value Activity Level Strenuous activity generates more heat and potentially greater comfort in space with lower temperature. Active occupant tend to be more tolerant of lower temperature and higher air velocities than occupants sitting sedately in an office or classroom Thermodynamics - Laws Thermodynamics is the study of heat, energy, and motion. Thermo refers to temperature dynamics means energy in motion. The three laws of thermodynamics help us understand how heat, energy, and motion work within the universe.  Thermodynamics - Laws Zeroth law of thermodynamics If two systems have equal heat flow back and forth and one of the two systems has equal heat flow back and forth with another system, all three systems have equal heat flow with each other. Hot coffee will eventually transfer its heat to If A = B and B = C, then A = C become equal with the room temperature Thermodynamics - Laws First law of thermodynamics An increase in energy in a system is the same as the energy given to a system in the form of heat or work. Energy cannot be created or destroyed, only changed. The amount of energy given to a system is the same amount of energy taken from the surroundings. Thermodynamics - Laws Second law of thermodynamics Given a pair of systems touching with different temperatures, heat will flow from hot to cold until the temperature of the systems becomes equal. Direction of Transmission High Pressure Low Pressure High Temperature Low Temperature High Humidity Low Humidity High voltage Low voltage Thermodynamics - Laws Third law of thermodynamics When a system has a temperature of 0 kelvin, absolute zero (the lowest temperature), the entropy (energy that cannot be used to do work) is at 0. Randomness: the movement of molecules Entropy: measure of the molecular disorder or of the probability of a given state; starting energy = work done plus entropy (some is lost to friction)  Direction of Transmission Everything is trying to to seek balance or equalization Applies directly to Energy  Psychrometry The science of measuring the water vapor content of the air. Measures the properties of moist air, their control, the effect on materials, and human comfort. Moisture content in air varies significantly under different conditions including Temperature Pressure Altitude 1911: developed the Rational Psychrometric Formulae ▪ Dew point temperature ▪ Relative humidity ▪ Humidity ratio ▪ Dry-bulb temperature ▪ Wet bulb temperature ▪ Humidity ▪ Specific humidity ▪ Absolute humidity ▪ Psychrometric ratio Psychrometric Chart Graphic Representation of of the physical and thermodynamic properties of air. Must understand the properties of air if you are going to change them. Cooling changes the property of air.  Psychrometric Chart Key Components 1. Dry Bulb temperature 2. Wet Bulb temperature 3. Dew Point Temperature 4. Relative Humidity 5. Specific Humidity Need any two variables to determine other variables Psychrometric Chart Additional Components 6. Absolute Humidity 7. Specific Volume 8. Enthalpy Wet Bulb Dew Point Wet Bulb temperature: temperature at which water, by evaporating into moist air at a given dry bulb temperature and humidity ratio can bring air to saturation adiabatically at the same Wet Bulb 61 temperature, while pressure is maintained constant. Dew Point: 53 60 grains Dew Point: is the temperature of moist air which is saturated and has the same humidity ratio as that of the given Condensation 75̊ sample of moist air. Relative Humidity Amount of moisture that a given amount of air is holding Relative = Humidity Amount of moisture that a given amount of air can hold (percentage) Relative: not constant a percentage that includes temperature and moisture  Real Relative Humidity moisture levels Relative Humidity: 60 = 45% RH 132 grains 132 60 grains The higher the air temperature the more moisture it can hold The cooler the air temperature the less moisture it can hold 75̊  Real Relative Humidity moisture levels Relative Humidity: 60 = 45% RH 132 grains 132 The higher the air temperature the more moisture it can hold The cooler the air temperature the less moisture it can hold 75̊ Relative Humidity- Heating Winter Conditions Room temperature: 75̊ F db Window surface temperature: 35̊̊ F db Dew Point (saturation) = 35° If RH is above 23% then condensation issue 23% RH 35̊ 75̊  Relative Humidity- Cooling Summer Attic Space Condition 95̊ F db 40% RH Dew Point (saturation) = 67̊ F Any surface that is below 67̊ F will condensation Typical distribution air is 55̊̊ F Cold duct within hot humid space will condense. (Not concerned with inside air condition, just the surface temp of the duct) 67̊ 95̊ Insulation Two known parameters allows one to calculate any other condition(s)  Climate Classifications Approximate zones of temperature and humidity Humidity places higher demands on the HVAC system Terminology – HVAC system Sensible Heat - Heat that can be measured or felt. Sensible heat always causes a temperature rise. “its not the ‘dry bulb’ (can ‘sense’- due to temperature difference) temperature heat that impacts comfort it’s the ‘wet bulb’ Latent Heat - Heat that produces a change of temperature and the state without a change in temperature; i.e., humidity” ice to water at 32 oF or water to steam at 212 oF.  Wet-Bulb Temperature Enthalpy: TOTAL HEAT (Enthalpy) - Total heat energy in a substance. Sensible + Latent Enthalpy is related to Wet Bulb Cooling is achieved by reducing current enthalpy to target enthalpy (or more)  Enthalpy - Cooling Cooling Hot, Humid Air Goal: 50% RH (“Houston”) means removing more energy than cooling hot, dry air GOAL (“Phoenix”) to the same cooling point  Typical HVAC Process Paths Heating is typically a “constant” “No such thing as a free lunch” specific humidity (gr/lb) process Can't get everything at once Cool from Need to humidify if air too dry AC Unit Cooling + Here Dehumidifying Cooling can take different paths GOAL Reheat coil (Hot water or electric) Steam Humidifier (heat + moisture) May need to reheat or dehumidify Heat from Here Gas Furnace to both control temperature and relative humidity ▪ Wet Bulb temperature line ▪ Relative humidity ▪ Dry-bulb temperature ▪ Wet bulb temperature ▪ Absolute humidity vapor pressure ▪ Enthropy Scale ▪ Specific Volume of Dry Air ▪ Dew Point ▪ Point established by any two parameters  Total Heat Latent and sensible heat are types of energy released or absorbed in the atmosphere. Latent heat is related to changes in phase between liquids, gases, and solids. Sensible heat is related to changes in temperature of a gas or object with no change in phase. HVAC - Cooling Mode Refrigeration: cooling a space, substance or system to lower and/or maintain its temperature below the ambient one (while the removed heat is rejected at a higher temperature)  Refrigeration Cycle Types of refrigeration processes that make chilled water or air: Compressive refrigeration Absorption refrigeration Evaporative cooling is not refrigeration but is integral to many cooling methods. Pressure Boiling Water Sea Level: 212° F 18,000 ft above Sea Level: 175° F Refrigerant R-22 under pressure: can boil at 40 F Refrigerant Past Refrigerants 1st refrigerants: ammonia and sulfur dioxide Key Properties January 1, 1996: CFC-11 and R-12, were phased out of production Lower boiling point Common Refrigerants R-22 and R-123, R-134a, R-410a and R-407c. Good heat transfer Anticipated Refrigerants R-32, Propane (R-290), ammonia, R1234 ZE  Refrigeration Cycle High Energy Movement Low Compressive Compressive Refrigeration Components Compressor: pressure increaser Condenser: heat rejector Expansion Valve/Metering Device: phase changer Evaporator- Heat Absorber Mediums: refrigerant (R-xxx) Condenser may be water-cooled or air-cooled Compressor Compresses the refrigerant which enter in a vapor state. Reduces the amount of space that the vapor is in Moves the refrigerant between the evaporator and condenser coils. Acts as a pump – only component that move refrigerant through the circuit.  Condenser The condenser rejects heat from the system. Types: Within an air- Remote Water-cooled cooled chiller stand-alone condenser Air cooled Can be packaged with other system components or a separate system element Within a Water-cooled residential chiller split unit  Metering Device Expansion Valve Purpose is to allow for pressure drop from high to low. Compressor increases pressure, while the metering device reduces pressure Manipulating temperature through pressure to get heat in and out of air Metering Device Expansion Valve Regulate the refrigerant by pressure which is entering space. Entering into compressor increasing pressure Entering evaporator decreasing pressure Gas Law: if drop the pressure then temperature drops  Evaporator The evaporator absorbs the heat Make cold refrigerant which allows it to absorb heat Coils are cold (in relationship to air stream) Typically, approx. 40̊̊ F, generally keep above 32 F For a freezer condition will want below 32 F Since it is colder, heat moves to or is attracted to cold coil (energy transfer: hot to cold) Evaporator Process of Absorbing Heat Boiling Phase changes liquid to vapor temperature of receiving source must be higher than the condensing temperature, so the outdoor temp can absorb the moisture. Sub-Heating Phase Temperature and pressure increases change from liquid to vapor state Functions the opposite of the condenser Heat Exchangers Evaporators and Condensers Types: Air-cooled Natural convection Usually for heating systems (radiator) Forced convection Fan in furnace Fan on condenser outside Water-cooled Tube in tube or double tube Shell and coil Shell and tube Provide efficient surface area to exchange energy to then be moved by the working fluid (refrigerant)  Refrigeration Cycle- Absorption Types of refrigeration processes that make chilled water or air: Compressive refrigeration Absorption refrigeration Evaporative cooling Use water mixed with ammonia or lithium bromide  Evaporative Cooling Process of absorption cooling Uses changes in a salt concentration between different tanks to move energy. Requires multiple pumps and high temperature energy source instead of a compressor to do work on the system. Most often done by steam as a heat source, but can also be done with solar collectors These systems are less efficient that compression, but are most useful when waste heat is available for input to the generator (power plants, old central energy plants) Newer plants use waste heat more efficiently for other processes (becoming obsolete)  Evaporative Cooling Types of refrigeration processes that make chilled water or air: Compressive refrigeration Absorption refrigeration Evaporative cooling  Evaporative Cooling Evaporative Cooling Water dropping over pads or fin tubes through which outdoor air or water is circulated. As free water is evaporated to vapor, heat is drawn from the outdoor from the circulating water, and then distributed to the indoor spaces. The only works in hot arid climates for direct cooling where the outdoor air has low humidity levels and evaporation will take place. When only cold air is needed and not the removal of humidity is the concept.  Evaporative Cooling Evaporative Cooling Water dropping over pads or fin tubes through which outdoor air or water is circulated. As free water is evaporated to vapor, heat is drawn from the outdoor from the circulating water, and then distributed to the indoor spaces. The only works in hot arid climates for direct cooling where the outdoor air has low humidity levels and evaporation will take place. When only cold air is needed and not the removal of humidity is the concept. Cooling towers  Cooling Equipment - Applications DX Air Cooling Coil Home AC (split unit) Packaged RTU residential split unit Packaged Roof-top Unit (RTU) Chillers Air-cooled chiller Water-cooled chiller Primary difference between units: DX (direct expansion) unit cools air Air-cooled chiller Water-cooled Chiller units cools water. chiller Cooling Equipment DX Split System Basic Compression Refrigeration cycle Common for residential & light commercial Make air inside cold and air outside warmer Inside Evaporator Coil Furnace Fan Outside Compressor Condenser Coil Condenser Fan  Cooling Equipment Packaged RTU Same Cycle as DX Split system but all in one box. Make air inside cold and air outside warmer Common for all commercial building types “Air-side” components discussed next time. Cooling Equipment Air Cooled Chiller Makes water (instead of air) inside cold, and air outside warmer. Common for larger commercial through industrial Better comfort control than direct DX in large systems. Can be more efficient. Typically, all components of the chiller are packaged outdoors. Some units install the evaporator inside for freeze protection (remote evap.) Other units install all vapor-side components indoors for maintenance & freeze protection (remote condenser) CHILLER Cooling Equipment Water-Cooled Chiller Makes water (instead of air) inside cold, water outside warm, and air outside warmer. Common for larger commercial through industrial More efficient than Air-Cooled Chiller – Why? Evaporative cooling (cooling tower) reduces compressor work to remove energy Typically, all components of the chiller are packaged indoors. Cooling Tower is located outdoors Requires two sets of pumps. More complex control than air-cooled chillers Heating Heat Energy is always moving; the manner in which it moves can vary. Three ways heat is transferred: Radiation Conduction Convection. heat occurs by a path that does not include transfer of matter. Heating - Radiation Radiation: the effect energy as it strikes a surface. Infra-red (IR) through Ultra-violet (UV) are an electromagnetic field capable of transferring energy from a source, such as a fireplace, to a destination, such as the surfaces within a room. Radiation does not require an intervening medium; it can occur through a vacuum. Heating - Radiation The Power of 104° F 89° F Urban Trees 115° F 93° F Radiation Increasing temperature without touching the surface Common application Microwave Impact within Building Sun Lights Winter: Heat gain Summer: increase Cooling loads Radiation Ability to have a positive impact to Building Desired heat gain in winter Harvest heat through solar panels Can also occur within the space Transfer warm surface to cold surface Exterior wall is cold, then the heat within the room will transfer to the colder surface. Radiation Trombe walls: a passive solar building design strategy that adopts the concept of indirect-gain. Radiant heat from sunlight is transferred to mass which is converted to thermal energy (heat) and then transferred into the living space. Passive Heating Thermal Mass Orientation South Southeast Southwest Radiation Mechanical System Radiators – exposed Source Steam Hot water Electric Radiation Mechanical System Equipment types Walls Ceilings Floors Source Steam Hot water Electric Radiation Mechanical System Equipment types Walls Ceilings Floors Source Steam Hot water Electric Conduction Conduction: Takes place when two material media or objects are in direct contact, and the temperature of one is higher than the temperature of the other. The temperatures equalize; heat conduction consists of a transfer of kinetic energy from the warmer medium to the cooler one. Examples: Energy transfer: high to low Chilled human body in a hot bath Hot : high molecular movement molecules Cold: slower molecular movement Warm coffee to cold hands Second law of thermodynamics Conduction Increasing temperature through touching the surface Common application In-floor heating system Heat Exchangers Impact within Building Exterior Walls- Heat gain/loss Prevent Conduction Air gap, insulation, coatings Material Selections Conduction Conduction  Convection Convection Occurs when the motion of a liquid or gas carries energy from a warmer region to a cooler region. Tendency of warm air to rise and cool air to fall, equalizing the air temperature inside a room. Convection Tendency of warm air to rise and cool air to fall, equalizing the air temperature inside a room containing a hot stove. Convection The ground heats the air above it, which rises in convection currents and cooler air from over the ocean flows toward the shore to “fill in the gap” left by the rising warm air.... The flow of cooler air from the ocean toward the shore creates what is known as a sea breeze. HVAC Heating Mode Heat Energy is always moving; the manner in which it moves can vary. Three ways heat is transferred: Radiation Conduction Convection. HVAC - Application How do heating and cooling system work in actual installations to deliver comfort to the interior spaces?  HVAC Distribution Systems Each facility is different, and their requirements vary, therefore the choice of an HVAC system must depend on several factors, which include: Building Use and Scale Climate Zone Control Requirements Integration with Aesthetics Integration with other building systems Energy efficiency Fuels Availability Initial costs and life cycle costs Maintenance costs HVAC Distribution Systems Decentralized / Unitary system System that serves one room or zone Smaller scale system Limited controls Centralized system System that serves larger zones and multiple rooms Larger scale system Air Handler Equipment Higher degree of controls  Decentralized Unitary Systems- Types Window Air Conditioning System Residential/Light Commercial DX Split System Mini-split system (ducted or ductless) Packaged Terminal Air Conditioning (PTAC) Heat Pumps Multi-unit Variable Refrigerant Flow system Self Contained System Ground-mounted outdoor unit Roof-top Unit Refrigeration Cycle Low Energy Movement High Compressive Supply air Return air To outdoors Includes transfer of energy (heat) by conduction and convection Furnace DX Split System Common for residential & light commercial Conditions air within unit Distribution: single duct Fan that ‘forces air through the building Fuel type Gas-fired Electric Furnace DX Split System DISTRIBUTION Furnace: interior Condenser: Exterior Supply Air Ductwork distributed to each room (Floor, Wall or Ceiling Return Air Plenum or ductwork back to furnace (Wall or Ceiling) Furnace DX Split System Advantages Economical Low installation costs. Low maintenance/operation costs Ease to test, adjust and balance the system. Low energy consumption. Individual section can be operated without running the entire system in the building. Add-ons: Humidification/Dehumidification Small impact to building footprint: (5’-0” x 5’-0” area) Furnace DX Split System Disadvantages Limited Controls One setting for all rooms within zone Life cycle : 10-15 years Serves small area/zone: 2,000 sf Less energy efficient Mini-Split DX System Heating and cooling for individual rooms or spaces Located within room Conditions air within unit Ducted or ductless Inexpensive, easy to install Requires Condensate drain lines Mini-Split DX System Mini-Split DX System PTAC DX System Heating and cooling for individual rooms or spaces Located within room Conditions air within unit, no ductwork Through-wall condition PTAC: packaged Terminal Air Conditioner PTAC DX System Comparison Mini-split versus PTAC Mini Split System PTAC System: better options for residential spaces for a variety providing cooling and heating to hotels, dorm rooms, of reasons including efficiency and aesthetics assisted living facilities, and more since you can since mini splits are going to take up less wall install a unit in every room allowing guests to space and blend into rooms better than PTACs. individualize their comfort. more efficient than PTACs. Many models are On average, PTACs are going to be a more affordable energy star rated and since they're designed for option than mini splits. Attempting to install enough zone comfort, you only choose the rooms you mini splits to cool and heat a hotel is going to be want to cool and heat. much more expensive than multiple PTACs. A mini split's compressor is housed outside, so the Reliable and reduced maintenance. When you're a only noise you'll have indoors is from the unit's commercial property owner time is money, so it's fan. important to have a unit that doesn't constantly require downtime. Variable Refrigerant Flow System (VRF) Format Two-pipe Three-pipe Four-pipe Heating and Cooling typical: all heat or all cool (unless over 5-ton unit) Condenser Type: Air-cooled or water-cooled Condensing unit serves multiple units  Capable of both heating and cooling, heat pump systems Heat Pump work like a refrigerator, using electricity to pump heat from System a cool space to a warm one to move warm air indoors in Air Source the winter, and vice versa in the summer. Because they Water Source move heat rather than generating it, operational costs are Ground Source significantly reduced.  Difference between an AC unit and a heat pump is that heat pumps can reverse the refrigerant flow direction and transfer Heat Pump heat from the outside to raise indoor temperatures by utilizing System a reversing valve built into the compressor. Air Source A conventional air conditioning system on the other hand must Water Source rely on electric resistant heat strips within the air handler or Ground Source utilize a gas furnace unit to produce/distribute warm air.  Heat Pump System Air Source uses outside air as a medium for heat exchange. Inexpensive to install and commonly used functions well in moderate climates Heat Pump System Water Source Water source heat pumps dissipate heat by way of water instead of air. Requires well, lake, or other water source access Water source geometry to absorb and reject heat. Open or Closed Loop system Heat Pump System Ground Source Ground source or geothermal heat pumps take advantage of thermal energy stored underground, transferring heat in a similar manner to air source heat pumps. The constant temperature of the ground, allows for a much more efficient operation Installation is pricier and more complicated due to the need for excavation and installation of underground piping. Impacted by soil type, moisture content Horizontal or vertical Produced by the Office of Public Affairs and Communications. Authors: Linda Kurtos, Director, Office of Sustainability Photography: Barbara Johnston & Matt Cashore  Packaged Roof-top Unit Same Cycle as DX Split system but all in one unit. Heating coil Make air inside cold and air outside warmer Common for all commercial building types Heating coil can be any of the system Electric Hot water/steam Refrigerant HVAC Distribution Systems Decentralized / Unitary system System that serves one room or zone Smaller scale system Limited controls Centralized system System that serves larger zones and multiple rooms Larger scale system Air Handler Equipment Higher degree of controls Centralized Air Distribution System DISTRIBUTION Provides Conditioned Air Distribution to multi-zones Utilized Water system Heating Coils: Central Heating plant (hot water coils) Cooling Coils: Central Cooling Plant (chilled water coils) Spaces/sub-zones are provided by additional equipment Centralized Air Distribution System Air Distribution Air Handler: Interior or Exterior Air Handler: central source for air distribution. Heating Coils Cooling Coils Filtration and Purification Humidification/Dehumidification Centralized Air Distribution System Central Plant Equipment Heating Equipment: Steam Boilers Hot Water Boiler Heat Pumps Heat Pump chillers Cooling Equipment: Chiller (air or water-cooled) Cooling tower Heat Pump chillers Distribution Equipment Pumps, Air Separators, Expansion Tanks Water Quality- filters and chemical treatment (glycol- if needed)) Centralized Air Distribution System- Constant Air Volume Advantages Lower initial cost Less control complexity Disadvantages Less efficient when setbacks can be used Does not maintain comfort as effectively for all spaces Shorter life span of equipment due to continuous use. More difficult to meet current energy code Centralized Air Distribution System- Variable Air Volume Advantages Can be more energy efficient Can provide better zone comfort Disadvantages More equipment to maintain Higher initial cost More complex controls required Higher maintenance and operation cost risk Additional Equipment Variable Air Volume (VAV) Can serve one room or multiple rooms within a zone Damper or fan powered Reheat coils to achieve proper temperature Ventilation Air Distribution Ductwork refers to the system of ducts (metal or synthetic tubes) used to transport air to or from a space. Properly installed and well-maintained air ducts are a key component of indoor air quality and home comfort.” Air Distribution Ductwork Ductwork Material Metal Fabric Air Distribution Ductwork Ductwork – Shapes Round Flat Oval Rectangular Flexible Shapes impacts air flow; Increase surface area increases friction Air Distribution Ductwork Ductwork – Shapes Round Flat Oval Rectangular Flexible Air Friction Loss:.060 -.10 Low energy compared to water (inches of water column per 100 ft) Air Distribution Consideration Building construction Steel frame with beams Pre-cast concrete Clearances above ceiling Noise sensitivity Insulation Routing Air Distribution Main Duct Purposes Supply: air travels from your heating and cooling system, through your ductwork and out of the supply vents. Can be mixed with fresh air and return air. Return: air that returns to the HVAC system from the area that is being cooled or heated. Air flows through return grilles and through the HVAC's ductwork for filtering and recycling or removal from the building. Exhaust: air that is deliberately removed from the building envelope and rejected to the environment. Exhaust fans draw air out of the buildings from strategic locations where low quality, moist or polluted air is likely to accumulate. Air Distribution - Supply Supply Air Provide new conditioned area to the room or space. Purge Supply air is mixed with return air contaminants and fresh air at the Primary unit (RTU or AHU). and replenish with fresh air Fresh air is required for human and space code requirements (flushing) Air Flow Distribution Multiple methods to distribute air. Must meet functional purpose of space and coordinated with building system  Air Distribution Basic Flow Patterns If unable to meet ideal air distribution, then amount of air is increased to address improper distribution Air Distribution Noise Criteria Noise is produced by the air diffuser and ductwork Method to evaluate noise level is the Noise Criteria (NC) Single measure with aggregates several frequency levels Typical NC ratings Quiet Rooms: 15-30 rating Offices: 35-50 NC rating Factory: 45-50 NC rating Oversized ductwork tends to be quiet Undersized ductwork will be noisy  Air Distribution Noise Criteria Avoiding 90 degree turns and installation of air flow vanes can help reduce air turbulence and air noise. SMACNA: establishes best practice for fabrication, configuration and installation Air Distribution - Return Distribution Devices Grille Location: away from supply air (short circuit) to maximize convection and air mixing and distribution Can be ducted from room or through a plenum Air Distribution - Return Plenum A larger zone that air collected is gathered prior to primary ducted system Utilize entire area above ceiling or within chase. Chase Vertical void (intentionally or unintentionally) that is used as a means to route building infrastructure. Air Distribution - Exhaust Removes air borne particulates, or high humidity air from room or space directly to the exterior. (removal of unwanted air) Rooms Kitchens Restrooms Garages Laundry Room Decontamination rooms Air Distribution Exhaust Removes air borne particulates or high humidity air from room or space directly to the exterior. Residential and Commercial Kitchens Restrooms Garages Laundry Room Air Distribution - Exhaust Make-up air unit Provides additional air to replace removed air from space. Without mark-up air, the room would become severely under pressurized. Make-up air can be conditioned or unconditioned Air Distribution Pressure Supply-Return-Exhaust Air Distribution directly impacts building pressure. If Outside Air (incoming) (cfm) is greater than Exhaust Air then under positive pressure. If Outside Air (incoming)(cfm) is less than Exhaust Air then under negative pressure. Supply Air + Outside Air = Total Volume of Air Air Distribution Positive Pressure Positive Pressure reduces infiltration. Exterior conditions (moisture and temperature difference) from potential conduction from exterior envelop. From adjacent rooms or spaces that may have contaminants or particulates Air Distribution Negative Pressure Negative Pressure. Reduces infiltration into other rooms or spaces Controls odor Allows air within space to be Typical Locations returned Restrooms Infection control High Humidity Rooms Trash rooms Garages Hospital Triage Rooms Air Distribution – Fresh Air Outdoor air is directly entered into the building’s air distribution. The amount of fresh air is based on Room Use No. of Occupants Outdoor conditions Air Distribution Measurement Unit: cubic feet per minute (CFM) Air flow and how it is distributed will impact: Considerations Air Noise Room Use Aesthetics Room Occupants Pressure Heating and Cooling Loads Primary Equipment RTUs and AHUs Location Central location to the area/zone which it serves. Adjacent to building core (stairs, elevator, restrooms) and away for noise sensitive rooms. Design is based on requirement to meet thermal comfort conditions. Ductwork, piping and air distribution directly impacted by location of equipment Air Distribution Primary Ductwork  Air Distribution Ductwork Primary Ductwork: Duct Mains allow air to flow from air handling unit to zones or spaces. Initial larger sizes are reduced as air is supplied to separate zones or spaces Branch Ductwork: Secondary ductwork allows air to flow from Primary Ductwork to specific zone or room Distributes conditioned air within room Air Distribution Secondary Ductwork Ductwork that branches from the primary duct main. Increase length increases static pressure, can limit distance from the main duct. Always install a balancing damper to regulate amount of air to each diffuser. Limit last branch to no greater than 4’-0” from the end of the main. Branches to be similar is size from the same duct run to allow proper air flow. Air Distribution Secondary Ductwork- Flex Allows for flexibility of diffuser/grille location. Limit Flexible duct to distances no greater than 6’-0”. Limit sags within flexible duct Avoid crimped run that prevent proper air-flow. Air Distribution Dampers Dampers allow for a means to regulate air flow Balancing damper: regulates air flow into space Fire damper: closes ducts and prevents fire from transferring through the duct Smoke damper: closes ductwork to prevent smoke from being distributed through the ductwork to other parts of the building Air Distribution Primary Ductwork Avoid runs through stairs, elevators, fire or smoke walls. In certain condition, may also need horizontal fire damper in vertical chase Ductwork will provide a means to compromise integrity of fire-rated wall construction. Air Distribution Sizing Factors that impact overall sizing Occupant Room Use Building Use Exterior Envelop Lighting Equipment Outdoor Conditions Building Code 403.3 Outdoor Airflow Rate Ventilation systems shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with this section. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3. Ventilation rates for occupancies not represented in Table 403.3 shall be those for a listed occupancy classification that is most similar in terms of occupant density, activities and building construction; or shall be determined by an approved engineering analysis. INDIANA: International Mechanical Code Building Code 403.3 Outdoor Airflow Rate The ventilation system shall be designed to supply the required rate of ventilation air continuously during the period the building is occupied, except as otherwise stated in other provisions of the code. With the exception of smoking lounges, the ventilation rates in Table 403.3 are based on the absence of smoking in occupiable spaces. Where smoking is anticipated in a space other than a smoking lounge, the ventilation system serving the space shall be designed to provide ventilation over and above that required by Table 403.3 in accordance with accepted engineering practice. INDIANA: International Mechanical Code Building Code Minimum Ventilation Rates are based on: Occupancy Classifications Occupancy Density Airflow Rates People outdoor airflow rate Area outdoor air flow rate Exhaust airflow rate INDIANA: International Mechanical Code Air Distribution CFM and ACH Cubic Feet per Minute Amount of air volume moving through ductwork. Air Changes Per Hour the number of times the air within a volume is changes within an hour Specialty room or spaces may dictate air changes per hour. (i.e. hospital and vehicle garages)  Air Distribution CFM and ACH Shall not be less than the calculated values utilizing Table 6-1. Room Use: Classroom (7th grade) Room Size: 900 s.f. Occupants: 30 Total Fresh Air Required in Zone Vbz = (10 x 30) + (0.12 x 900) Vbz = 300 + 108 = 408 cfm AHRAE Standard 62.1-2007 Fresh Air = cfm/person + cfm/ft2 Breathing Zone Outdoor Airflows Air Distribution CFM and ACH Air Changes Per Hour the number of times the air within a volume is changes within an hour 10’-0” Air Changes per Hour: 4 Total cfm = 3000 x 4 = 12000 cfh 15’-0” 20’-0” 60 minutes Volume of Space 200 cfm 15’-0” x 20’-0” x 10’-0” = 3000 cf (width) x (length) x (height) Air Distribution Sizing Criteria Air velocity Pressure Volume of Air Determines duct free area Actual size (W x H) can vary Duct sizes determine total pressure and fan size Air Distribution Ductwork Conventions Nomenclature- Plan View: Horizontal x Vertical (inches) Clearances: ductwork size plus 2” for insulation Last branch to be 4’-0” from end of main duct Use of Flex ductwork: maximum length 6’-0” Maximum Height: Distance from bottom of structure to bottom of finished ceiling less 6” – 12”. Must allow for ceiling support, lights and ceiling mounted devices.  Air Distribution Air Volume in Room Started from furthest point 200 cfm 200 cfm in run Add each 800 cfm 600 cfm 400 cfm 200 cfm amount of each Branch duct 200 cfm 200 cfm  Air Distribution Duct Routing Office Office Air Handler 500 cfm 500 cfm Equipment Meeting Office Office 2000 Roomcfm 500 cfm 500 cfm Lecture Hall 1000 cfm Classroom 1500 cfm  Air Distribution Total Air Volume Office Office Air Handler 6500 cfm 500 cfm 500 cfm Equipment 4000 cfm 3000 cfm 2000 cfm 3500 cfm 2500 cfm 2500 cfm Meeting Office Office 2000 Roomcfm 500 cfm 500 cfm Lecture Hall 1000 cfm 1500 cfm Classroom 1500 cfm Air Distribution Above Ceiling Zones Conflicts with other HVAC components Conflicts with other Disciplines Structure Plumbing Fire Protection Electrical IT Data Air Distribution - Sizing Factors that impact overall sizing Occupant Room Use Building Use Exterior Envelop Lighting Equipment Outdoor Conditions Conduction Exterior Envelop British Thermal Unit – BTU: Amount of heat required to raise the temperature of 1 lb of water by 1 degree F. Conductance: The number of BTU’s per hour that pass through 1 sq ft of homogeneous material of a given thickness when the temperature differential is 1 degree F. (BTUH is BTU per hour) Exterior Envelop Resistance: Number of hours needed for 1 BTU to pass through 1 sq ft of material or assembly of a given thickness when the temperature differential is 1 degree F. The reciprocal of coefficient of heat transmission Refers to R-Value Coefficient of heat transmission The overall rate of flow through any combination of materials, including airspaces and air layers on the interior and exterior of a building assembly. Reciprocal of the sum of all the resistances Refers to U-Value  Compensate for excess heat gain or loss with passive design solutions or use mechanical heating and cooling Thermal Loads systems External and External heat loss factors Air temperature Internal Wind External heat gain factors A building must resist Air temperature Sunlight loss of heat to the outside during cold Internal heat gain factors People weather and heat gain Lights during the summer Equipment  Heat Gain and Loss from Building Envelop To determine size of heating/cooling equipment for a building, room or space must determine the Heat Loss Heat is lost in two basic ways: Through the building envelope Through Air infiltration Process to determine Heating and Cooling Loads Code Requirement: Based on Energy Code (ASHRAE 90.1) 5 ̊̊̊̊ F difference between heating 1. Establish Building Location and cooling set points. 2. Design Temperatures: Winter and Summer Thermal Comfort 3. Determine Building Loads DB: 74 ̊ F RH: 50% - 55% 4. Building Orientation 5. Number of Occupants Additional Use can have specific requirements Operating Room Museum 6. Exterior Envelop Meat Packaging facility 7. Establish required cooling load Outdoors conditions Interior Calculations 8. Establish required heating load Winter: -10 F Winter condition: 70 F Summer: 90 F Summer condition: 75 F Determining Heating and Cooling Load Block Load: calculates heating and cooling loads for the entire conditioned space. CAUTION: Room by Room Load: calculates heating and cooling Cannot use Rules of load calculation for individual rooms. thumb when sizing HVAC systems Both options should yield similar results in cooling and heating totals. especially for new building due to exterior If you are considering a zoned system, or are looking to design or verify ductwork, room-by-room envelope, building use calculations are more accurate to calculate the CFM required in each room. and client expectations.  Rules of Thumb (not exact, but will provide ROUGH Estimate) The 1.7X rule This rule of thumb states that the MAXIMUM heating capacity required for your comfort cooling application is 1.7 x the cooling load. For example, if the cooling required is 30 tons (360,000 BTUs), then the MAXIMUM heating capacity required is approximately 612,000 BTUs (1.7 x 360,000). This assumes no lighting, no people, no internal heat gain, and a -10 deg F ambient design temperature. The heating requirement could be more, though it is extremely rare. 400 sq ft per ton This rule states that the square foot of a building/zone divided by 300 = approximate tons of cooling. For example, for a 24,000 s.f., then estimated tonnage needed is 24,000 ÷ 400 = 60 tons. This is a ROUGH estimate on how much comfort cooling a commercial building needs. The cooling requirements depend on many factors (insulation, population density, window type, internal equipment, lighting, etc), so use this rule of thumb carefully. 1 ton of cooling is equivalent to 12,000 BTUs Rules of Thumb (not exact, but will provide ROUGH Estimate) 150 cfm per ton for make-up air (DOAS) If a portion of your building needs make-up air (100% outdoor air), the amount of cfm PER ton is about 150 cfm. For example, a 15,000 cfm make-up air unit with cooling, would require approximately 100 tons of cooling associated with make-up air unit. 0.1 tons/person in densely populated zones Used for estimating the cooling load for a densely populated area/space, (i.e. auditorium, gymnasium or church). For example, if an auditorium occupant load is 1400, the cooling load would be close to 140 tons (1400 x 0.1). If the space is well insulated, this rule of thumb reduces a bit to 0.08 tons per person. Make-up Air Unit = Direct Outside Air System (DOAS) Rules of Thumb (not exact, but will provide ROUGH Estimate) 50 heating BTUH per square foot (BTUH = 1.08 x CFM x deltaT), Heavily depends on insulation factors and heat generating equipment. In reality, most commercial buildings (offices, retail, schools) are probably closer to 25-35 BTUH per square foot, but warehouses or areas with more ventilation could require 50-75 BTUH per square ft. This also depends where in the country or world you are. In the the Midwest this is a good rule of thumb, If you are in southern California, or in the arctic circle, then this rule of thumb may not be appropriate..8-1.3 CFM per sq ft To determine how much cfm you need to deliver to a space. If the cooling load is relatively small, the system may require less cooling and may be closer to 1 cfm/sq ft. In spaces that are more density populated, like conference rooms, gymnasiums or auditoriums, the space may require closer to 2 cfm per sq ft. Determining Heating and Cooling Load Sensible Heat Equation BTUH = CFM x 1.08 x (EAT –LAT) CFM = BTUH/1.08 x (EAT – LAT) EAT = Indoor Design Temp (DB) LAT = Supply Air Design Temperature Sensible Heat is a change in temperature (DB) with no change in moisture. Indoor Air: 75 F Supply Air: 55 F Latent heat involves moisture 12,000 BTU = 1 ton Sensible Heat Transfer Determine people by occupant load 150 people x 230 BTU/HR = 34,500 BTU/HR 150 x 255 BTU/HR = 38,250 BTU/HR 150 x 635 BTU/HR =95,250 BTU/HR Just to overcome people heat gains only one needs at least 2.875 tons of cooling. 12,000 BTU = 1 ton Sensible Heat Transfer Power Receptacle: 125 -150 watts  Sensible Heat Transfer A: area SC: Shading coefficient U: established value based on material properties SCL: shade cooling load A: area TD is temperature difference between side Sensible Heat Transfer 125 Watt Sensible Heat Transfer (assume one office (2 person) 1.29 tons of cooling 12,000 BTU = 1 ton Sensible Heat Transfer (For sensible heat transfer) Also need to ADD required Fresh Air cfm Fresh Air Ventilation = 2 person x 7.5 = 15 cfm TOTAL CFM for Room = 732 cfm (assume 750 cfm) IMC Table 403.3 for Fresh Air requirement Heat Loss Exterior Envelop Building envelope: walls, roof, doors, windows, and floor/foundation All materials have properties which resist the transfer of heat: Concrete Masonry Unit 1.300 Face Brick.540 Glazing system.391 Gypsum Board.650 Air.025 All materials are unique in their conductivity (k). Conductivity (k): Amount of heat lost through 1 sq ft of 1 inch thickness with 1 degree F temp difference Resistance is measured in R-value Heat Transfer Exterior Envelop  Heat Transfer Exterior Envelop Fourier’s Law of Heat Transfer The rate of heat transfer approximately equal to the thermal transmittance (U-factor) multiplied by the area and multiplied by the change in temperature Heat Transfer Exterior Envelop Heat Transfer Exterior Envelop U-Factor R-Factor U-Factor: Thermal Transmittance R-Value: Thermal Resistance The higher the R-value the higher the resistance to heat transfer Typical Masonry Wall U-Factor: Thermal Conductivity R-value: Resistance (1/U) The lower the Conductance the Higher Resistance The greater the Resistance the less Conductance (transmission through material or system) Unique for each material Building Envelop includes summation of overall system Calculated R-value Typical Masonry Wall R-Factor: Thermal Resistance Unique for each material Building Envelop includes summation of overall system Exterior Wall Assembly (R-value) 4” Face Brick:.44 Air Space:.97 Insulation (2”): 12 14.338 R 8” CMU:.478 Windows:.45 If only U-values are known, then one must find R-value for each material and then add all R-value for wall assembly