The Building as a System PDF

THE BUILDING AS A SYSTEM  A building is … a structure consisting of roof, walls, windows and doors designed to protect occupants from weather  A building is also … a system consisting of a number of distinct parts or components. Each component may be a system itself comprised of...

THE BUILDING AS A SYSTEM  A building is … a structure consisting of roof, walls, windows and doors designed to protect occupants from weather  A building is also … a system consisting of a number of distinct parts or components. Each component may be a system itself comprised of many sub-systems. Components are linked in such a way that change in one component usually results in change in another. 3 MAJOR COMPONENTS THE BUILDING ENVELOPE THE MECHANICAL SYSTEMS THE OCCUPANTS THE BUILDING ENVELOPE Consists of ceilings, walls, windows, doors, exposed floors, basement floor & walls Role in terms of HVAC: separate indoor from outdoor environment control heat flow into and out of building control moisture and air flow Materials used and detailing of parts very important considerations of building envelope design THE MECHANICAL SYSTEMS controls heating, cooling, humidity, air movement (comfort factors) also includes any equipment that contributes to generation of heat and /or moisture – hot water heater, stove, fridge, lighting, washer & dryer, motors, etc.  THE OCCUPANTS manipulate the building enclosure contribute to heat and moisture gains determine the function and use of the building (what comfort levels are required)  3 MAJOR COMPONENTS & 3 FLOWS Building envelope, mechanical systems and occupants are linked not only to each other but also to 3 “flows” Air flow Heat flow Moisture flow  HEAT FLOW Heat flows continuously into and out of a structure. How it moves determines operating costs and occupant comfort levels. Heat flow is the driving force behind air flow and moisture flow as well. Heat flow continues until a balance is achieved.  Heat Losses Losses occur in 3 major ways 1. Through openings in the building envelope 2. By conduction, convection and radiation 3. By flue and exhaust fan losses All heated air eventually ends up outside of the building and must be replaced by an equal amount of air Heat Gains Heat gains come from 3 major sources 1. Solar gains 2. Internal gains 3. Heating system gains Solar can account for 10-20% of heating load in non-solar applications Internal gains include occupants, lighting, appliances, etc. Heating and cooling equipment contribute to heat gains  AIR FLOW is very important to maintain good air quality and control heat and moisture continuous changes occurs between the building and its surroundings by: 1. Ventilation 2. Air leakage  Ventilation Is a controlled air leakage Designed & planned for includes bathroom exhaust fans, dryer vents, mechanical ventilators etc.  Air Leakage unintentional or uncontrolled air change occurs as: Exfiltration air leaking out of the building Infiltration air leaking into the building also occurs wherever there is a pressure difference Stack Effect Flue Effect Ventilation Effect Wind Effect  Overall Air Flow Very difficult to determine because all 4 pressure conditions are constantly changing  MOISTURE FLOW like heat and air, moisture continuously flows in and around the building requires air and/or heat to move – if both air and/or heat is controlled then moisture is controlled. sources of moisture include showers, dishwashers, mechanical devices, occupants, etc. some moisture can be controlled by controlling occupant activities Resources www.ukfrs.com http://www.bpiexamacademy.com https://energy.ces.ncsu.edu