Module 2 - Energy Fundamentals.pptx

Energy Fundamentals © 2023 STRAND Dallas I Texas 972 620 8204 Energy Fundamentals © 2023 STRAND Dallas I Texas 972 620 8204 Principles of Energy for Residential Buildings •Energy principles are essential for understanding energy flows in residential buildings. •Buildings use energy for tem...

Energy Fundamentals © 2023 STRAND Dallas I Texas 972 620 8204 Energy Fundamentals © 2023 STRAND Dallas I Texas 972 620 8204 Principles of Energy for Residential Buildings •Energy principles are essential for understanding energy flows in residential buildings. •Buildings use energy for temperature control, lighting, hot water, appliances, and entertainment. •Energy is a measurable quantity of heat, work, or light. More than 99% of the energy we use comes from the sun. •Two laws of thermodynamics govern the behavior of heat in our universe: energy is neither created nor destroyed, and heat moves from high temperature regions to low temperature regions. © 2023 STRAND Dallas I Texas 972 620 8204 Energy Transformation, Heat Flow, and Comfort •Energy is transformed or converted from one form to another and is not created nor destroyed. •Potential energy is energy in a stable state that can be used for work or heat, while kinetic energy is the energy of motion. •Energy transport is the intentional movement of energy from one place to another, and it is more convenient to convert potential energy to kinetic energy at a central location like a power station or boiler room. •Heat travels from areas of high temperature to areas of lower temperature in three ways: conduction, convection, and radiation. •Air temperature, relative humidity, radiant temperature, and air movement are the © 2023factors STRAND that determine comfort in both Dallas I Texas four 972 620 8204 Energy and Building Construction •HOME Ideal buildings maximize heat retention during the winter and minimize heat gains during the summer to reduce heating and cooling needs. •Energy-efficient design, planning, and construction are the best ways to achieve energy efficiency in a new building, while modifications called weatherization are performed in existing buildings. •Making decisions about a building's weatherization is the job of an energy auditor who takes measurements, estimates costs, develops energy savings projections, and performs physical inspections of buildings to © 2023 STRAND decide which retrofits to recommend. Dallas I Texas 972 620 8204 •Concrete and steel are the main structural materials in many larger multifamily buildings, and steel skeletons are common for high rises. •High-rises have relatively higher internal heat gains from people, lights, appliances, and other heat sources, making cooling a dominant energy cost. •Airtightness and solar reflectance are very important to minimizing multifamily shellrelated energy consumption, and weathertightness and airtightness are important for preventing building deterioration. •Protecting the very heat-conductive steel framework from condensation in both the heating and cooling seasons is vitally important for durability in masonry and heavy timber construction.Construction and Air Leakage in Multifamily Buildings •Concrete and steel construction is common © 2023 STRAND Dallas I Texas in large high-rise residential buildings. 972 620 8204 •Thermal bridging between metal, concrete, and glass speeds up heat loss and solar heat gains. •Air intake and exhaust vents are necessary for heating, cooling, and ventilation systems. •Horizontal cavities and vertical shafts in multifamily buildings are conduits for air leakage and mixing of indoor and outdoor air. •These conduits include suspended ceilings, supply ducts, building cavities, elevator shafts, plumbing shafts, chimneys, and stairwells. •Heat flows through the building shell by two mechanisms: transmission and air leakage. •Heat transmission through the building shell depends on thermal resistance and surface area. © 2023 STRAND Dallas I Texas •Air leakage in cubic feet of air per minute 972 620 8204 Heat Flow in Buildings Conduction When two surfaces at different temperatures are in direct contact, heat will naturally flow from the warmer material to the cooler, until a balance is reached. The rate at which this heat transfer occurs depends on the temperature difference between the two surfaces and on the thermal resistance (R-value) of the material. Convection Warm air naturally rises within a space, and colder air falls. These movements of warm and cold air are known as convection currents, which sometimes move in circles called convective loops. Radiation Warm objects give off waves of heat, which can travel across an open space and be absorbed by cooler objects. The most common example of this is the sun, which radiates heat across space to warm the Earth. Even our own bodies radiate a certain amount of heat. Typical insulation materials do not reduce radiation heat loss unless they contain a radiant barrier (such as reflective foil). © 2023 STRAND Dallas I Texas 972 620 8204 Heat Flow in Buildings © 2023 STRAND Dallas I Texas 972 620 8204 •Heat transmission and air leakage occur through four independent pathways: floors and foundations, walls, roofs and ceilings, and fenestration (windows and doors). •Windows are a special concern because of low thermal resistance and significant surface area. •Doors have less associated energy loss overall because their combined surface area is relatively small. •Minimizing air leakage in multifamily buildings can reduce energy consumption and improve indoor air quality. © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND Dallas I Texas 972 620 8204 Understanding Thermal Conductivity and Building Inspections for Energy Efficiency •The k-value measures the amount of heat that flows through a material with a 1-inch thickness and a 10°F temperature difference between its two sides. •Thermal bridging occurs when highly conductive materials touch each other, causing rapid heat flow and resulting in cold interior surfaces during winter and hot interior surfaces during summer. •Using less-conductive gaskets called thermal breaks between conductive materials reduces rapid heat flow. •The thermal resistance of building-shell components, such as walls and roof assemblies, is an area-weighted average of the different materials in their crosssections. © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND •Stack effect occurs when warm air rises and leaves the home through holes near the ceiling, while cold air enters near the floor to replace it. •Air leakage occurs through penetrations in the building shell's interior and exterior skin, which can result in energy waste and discomfort. •A continuous and effective air barrier should border and touch the insulation to prevent migrating air from convecting heat from the insulation's surface, intruding into the insulation, or carrying heat around it. •Windows are often a major source of energy problems, with their low thermal resistance and high solar transmittance affecting comfort more directly than other building components. •Building inspections and diagnoses by trained energy auditors are necessary before proposing retrofits for energy Dallas I Texas conservation, health and safety, and 972 620 8204 Driving Forces of Air Movement Wind Stack Effect © 2023 STRAND Dallas I Texas 972 620 8204 Moisture Flow in Buildings Moisture Flows in two states: Vapor and Liquid There are four types of flows: 1. Bulk – Liquid flow 2. Diffusion – Vapor/Liquid Flow 3. Capillary – Liquid Wicking 4. Infiltration - Vapor © 2023 STRAND Dallas I Texas 972 620 8204