BUSI401 CHAPTER 6 Flashcards
_____ OR ______ elevators are typically installed for mid- to high-rise residential and commercial buildings. These elevators offer the fast and smooth service required to quickly move larger volumes of building occupants within the building.
CABLE-DRIVEN OR TRACTION ELEVATORS are typically installed for mid- to high-rise residential and commercial buildings. These elevators offer the fast and smooth service required to quickly move larger volumes of building occupants within the building.
Cable/traction elevators offer fast, smooth acceleration and can travel at speeds up to up to ____ feet per minute — in comparison to a maximum speed of ____ feet per minute for hydraulic elevators.
Cable/traction elevators offer fast, smooth acceleration and can travel at speeds up to up to 2,000 feet per minute — in comparison to a maximum speed of 200 feet per minute for hydraulic.
Rule of Thumb for Elevator Speed
A rule-of-thumb for elevator speed is that it should be no slower than twice the elevator rise from top to bottom landing, e.g., for a rise of 150 feet, the speed of the elevator should be 300 fpm.
HVAC FUNCTIONS
A modern HVAC system has multiple functions, which may include some or all of the following:
• Heating
• Cooling
• Humidifying and dehumidifying air
• Ventilation or provision of fresh air
• Filtering of dust and odours
• Distribution of fresh air, warm or cool, to all building zones
• Pressurization for even distribution of fresh air, heat, and cooling throughout the building
HVAC design considerations
A building’s HVAC system must consider the following factors:
• The peak heating and cooling loads
• Ventilation requirements
• Zones
• Lifecycle costs
Heating and cooling loads influenced by _ _ _ _
Heating and cooling loads refer to the thermal energy that must be supplied or removed from a building to meet the building’s design needs.’ The heating and cooling loads are influenced by a combination of factors including the local climate, nature and number of building occupants, desired interior temperatures and humidity, rate of air exchange, interior floor layout, lighting systems, office equipment, type and extent of window glazing, and orientation of the building.
For example, heat from the lighting system can add significantly to the cooling requirements of a building. The lighting designer and HVAC designer must coordinate their efforts, especially in areas requiring high intensity lighting.
NOTE ONLY
To calculate a structure’s heat load, the engineer must determine the amount of heat transmission (loss) through all materials exposed to unheated areas (outside). The engineer also determines the amount of energy needed to heat air entering the building through cracks in the structure, open doors, open windows, and through air intakes.
NOTE ONLY
To calculate a structure’s heat load, the engineer must determine the amount of heat transmission (loss) through all materials exposed to unheated areas (outside). The engineer also determines the amount of energy needed to heat air entering the building through cracks in the structure, open doors, open windows, and through air intakes.
Explain Thermal Energy Storage
Thermal energy storage (TES) allows excess thermal energy to be collected for later use, hours, days or many months later, at individual building, multiuser building, district, town or even regional scale depending on the specific technology. As examples: energy demand can be balanced between day time and night time; summer heat from solar collectors can be stored inter-seasonally for use in winter; and cold obtained from winter air can be provided for summer air conditioning. Storage mediums include: water or ice-slush tanks ranging from small to massive, masses of native earth or bedrock accessed with heat exchangers in clusters of small-diameter boreholes (sometimes quite deep); deep aquifers contained between impermeable strata; shallow, lined pits filled with gravel and water and top-insulated; and eutectic, phase-change materials.
Sick Building Syndrome
With building envelopes becoming tighter for energy efficiency, there is potential for insufficient fresh air in the building and a build-up of interior pollutants. Without enough fresh air entering the building, the CO, levels increase and occupant health issues may arise, sometimes characterized as “sick building” syndrome.
STACK EFFECT
The “stack effect” is when warm air moves upward in a building.
STACK EFFECT /2
The “stack effect” is when warm air moves upward in a building. This happens in summer and winter, but is most pronounced in the winter because indoor-outdoor temperature differences are the greatest. Warm air rises because it’s lighter than cold air. So when indoor air is warmer than the outdoor air, it escapes out of the upper levels of the building, through open windows, ventilation openings, or penetrations and cracks in the building envelope. The rising warm air reduces the pressure in the base of the building, forcing cold air to infiltrate through open doors, windows, or other openings. The stack effect basically causes air infiltration on the lower portion of a building and exfiltration on the upper part.
COMMON INDOOR POLLUTANTS
COMMON INDOOR POLLUTANTS
• radon;
• formaldehyde;
• asbestos;
• organics;
• mercury;
• carbon monoxide;
• fluorocarbons; and
• cigarette smoke and pet dander in multifamily applications.
Three Modes of Air Exchange
- *There are three major modes of air exchange:
1. Forced ventilation through a HVAC system
2. Natural ventilation through windows, doors, and louvers
3. Uncontrolled air infiltration through unintentional openings**
TRUE or FALSE?
Uncontrolled infiltration is undesirable and contemporary envelope design attempts to reduce this to zero.
Answer
TRUE
**True of False?
For many buildings, forced ventilation is the only significant form of ventilation.**
**ANSWER
TRUE**
_ _ _ _ _ _ specifies the amount of ventilation required based on type of use and estimated maximum occupancy for a given area.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) specifies the amount of ventilation required based on type of use and estimated maximum occupancy for a given area.
ZONES
In commercial buildings it is difficult to maintain all interior space at the same temperature, given variations in number of occupants, heating loads from equipment and lighting, and exposure of interior space to window glazing.
A corner office may require the greatest heating and cooling since it is exposed to windows on two sides. HVAC engineers will typically identify zones or discrete areas of interior space where heating and cooling loads will be different and require different distribution of HVAC ducting and related systems.
It is not uncommon for buildings to require simultaneous heating and cooling, where there is minimal inter-zone heat and cooling transfer.
Common HVAC design distintciton?
A common HVAC design distinction is interior zones versus perimeter zones. Interior zones have little exposure to the outside environment while perimeter zones adjacent to window glazing experience the highest amount of solar gain and heat loss. Interior zones are often defined by interior partition walls.
Common HVAC design distintciton?
A large open office area may only require one HVAC zone. Interior space with many demised partitions for offices, conference rooms, and other uses may require several different HVAC zones. Therefore, the interior office design for a tenant or occupant will have a big impact on HVAC design and in turn the cost of the HVAC installation.
NOTE ONLY
Commercial HVAC systems can be classified according to the heating/ cooling medium used. For example, HVAC systems can be:
• Strictly air-based: air is the heating and cooling medium
• Strictly water-based: piped water is the heating and cooling medium
• Water-to-air: central system distributes chilled or heated water to terminal units (fan-coils) in specific zones
• A combination of water and air systems: these distribute chilled and hot water and conditioned air from a central system to individual rooms or zones
In small commercial buildings, the most common system is air-based with ducting to distribute warm or cool air. As buildings become larger, it becomes less practical and more expensive to “push” conditioned air from a central system through very long ducting runs. Ducting also requires a considerable volume of interior space for vertical and horizontal ductwork — meaning a potential loss in rentable area. For these reasons water-to-air systems are common for large commercial buildings.
NOTE ONLY
Commercial HVAC systems can be classified according to the heating/ cooling medium used. For example, HVAC systems can be:
• Strictly air-based: air is the heating and cooling medium
• Strictly water-based: piped water is the heating and cooling medium
• Water-to-air: central system distributes chilled or heated water to terminal units (fan-coils) in specific zones
• A combination of water and air systems: these distribute chilled and hot water and conditioned air from a central system to individual rooms or zones
In small commercial buildings, the most common system is air-based with ducting to distribute warm or cool air. As buildings become larger, it becomes less practical and more expensive to “push” conditioned air from a central system through very long ducting runs. Ducting also requires a considerable volume of interior space for vertical and horizontal ductwork — meaning a potential loss in rentable area. For these reasons water-to-air systems are common for large commercial buildings.
HVAC small commercial vs large commercial?
In small commercial buildings, the most common system is air-based with ducting to distribute warm or cool air. As buildings become larger, it becomes less practical and more expensive to “push” conditioned air from a central system through very long ducting runs. Ducting also requires a considerable volume of interior space for vertical and horizontal ductwork — meaning a potential loss in rentable area. For these reasons water-to-air systems are common for large commercial buildings.
Systems can also be classified by the means of delivery:
Systems can also be classified by the means of delivery:
- Central systems have all HVAC equipment centrally based, such as in the basement.
- Package systems or unitary systems have all components assembled as a package and commonly lifted into place on the building roof.
- Other systems may involve new technology such as geothermal heating combined with heat pumps for specific zones.
HVAC Primary & Secondary Systems
Heating/cooling systems can be divided into primary and secondary systems. Primary plants produce the heating or cooling. Secondary systems comprise the duct-work, piping, pumps, fans, and auxiliary heating systems that distribute, regulate, and boost the heating/cooling produced by the primary system.
HVAC Primary Heating Sources
Primary heating plants are typically categorized by the fuel source, such as oil, natural gas, solar, or geothermal. The availability, cost, and efficiency of each heating source will change over time. Oil-fired heating systems were very common over the past 60 years, but are now rarely found in newer buildings due to the lower cost of natural gas. Electricity is commonly used for heating in residential buildings, but is rarely used in commercial buildings as a primary heat source given the very high cost relative to oil and gas.
Forced Air Furnance
list 3 things
Forced Air Furnaces
Gas and oil fired furnaces heat air and circulate the heated air by forced convection using fans. Commercial furnaces are rated according to their heating capacity in BTUs or British Thermal Units produced per hour. A gas furnace for a larger commercial building may be rated at 1,000,000+ BTUs/hr.
