Module 5- Building Envelope.pptx

STRAND Energy-Star Training The Envelope – Home as a System © 2023 STRAND Dallas I Texas 972 620 8204 House: As a Stand-Alone System © 2023 STRAND Although separate from each other – your insulation, heating and cooling system, windows, doors, ventilation, and exterior walls, foundation and s...

STRAND Energy-Star Training The Envelope – Home as a System © 2023 STRAND Dallas I Texas 972 620 8204 House: As a Stand-Alone System © 2023 STRAND Although separate from each other – your insulation, heating and cooling system, windows, doors, ventilation, and exterior walls, foundation and siding make your house operate as a multi-component system, where all the components are interactive. Because your house operates as a multi-component system – sometimes energy retrofits to one component of your home can affect other components of your home in unintended ways. Before starting to improve the efficiency of your home with one retrofit, it is a good idea to get advice to ensure that your investment in home energy improvements meets your expectations and that you will not be causing new issues while resolving old ones. Planning your retrofits within a house-as-a-system approach will also allow you to create a long-term home energy improvement plan and will provide guidance on the recommended order in which to complete energy retrofits. Dallas I Texas 972 620 8204 Average Temperatures © 2023 STRAND Dallas I Texas 972 620 8204 •Heating degree-days are a measure of how much heating is needed to maintain a comfortable indoor temperature during the winter. •Cooling degree-days are a measure of how much cooling is needed to maintain a comfortable indoor temperature during the summer. •Heating degree-days are directly related to heating costs, with higher degree-days requiring more fuel to heat a home. © 2023 STRAND Dallas I Texas 972 620 8204 •Cooling degree-days are calculated by totaling up daily degree-day values for days when the average temperature was above the cooling balance point of 780F. •Heating degree-days and cooling degreedays can be used to calculate building heat flows and energy consumption. •Heating degree-days can also be used to compare the energy efficiency of different buildings or heating systems. •The concept of degree-days was first introduced in the 1940s as a way to measure energy consumption for heating and cooling. •The use of degree-days is becoming increasingly important as climate change leads to more extreme temperatures and greater energy demand for heating and cooling. © 2023 STRAND Dallas I Texas 972 620 8204 Energy Conversion and Humidity for Home Comfort •Humidity affects the heat capacity of air and is measured by relative humidity (rh). •High humidity reduces sweat evaporation, decreasing summer comfort. •Warmer air can hold more moisture than cooler air, affecting humidity levels. •Indoor humidity is affected by outdoor humidity, moisture generated in the home, and ventilation. •Condensation on surfaces can occur when humid air meets cool objects, promoting microbial growth. •Air circulation is important for both © 2023 STRAND summer and winter comfort. • Dallas I Texas 972 620 8204 •Heat loss and gain through the building shell are the largest energy demands on residential buildings. •Building structures are classified as planer or skeletal design, depending on whether they are supported by columns and beams or by panels, and many buildings combine these two structural styles. •Masonry materials are preferred for foundations because they resist rot and corrosion, and foundations should sit on and be surrounded by dry ground. •Mobile homes are factory-built woodframed buildings attached to a steel trailer or chassis, and air leaks and insulation flaws are commonly found in joints and holes in force&air distribution systems, torn or missing belly paper, and plumbing penetrations. © 2023 STRAND 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 Why High Performance? • Save homeowner on utilities • Protect family health • Home Durability • Increased Comfort level • Limit pollutant and allergen infiltration • Meet Current Energy Code Certification Paths. © 2023 STRAND Dallas I Texas 972 620 8204 Energy Consumption Models © 2023 STRAND Dallas I Texas 972 620 8204 House: Building Thermal Envelope A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noise transfer © 2023 STRAND Dallas I Texas 972 620 8204 •Defining the thermal boundary around the conditioned space, where insulation and an air barrier are located, depends on the building's spaces' use and practical considerations such as access and cost of materials. •Thermal boundary decisions involve choosing where to insulate, based on the ease and cost of air sealing and insulating the floor or foundation walls, among other factors, and whether to include unoccupied basements and crawl spaces within the thermal boundary. •Visual inspection is necessary to learn about a building's construction and identify its conditioned, unconditioned, and unintentionally conditioned areas to determine remedies for energy and maintenance flaws in the building shell.Assessing Building Insulation and Air © 2023 STRAND Dallas I Texas Barrier 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 •Glass has special qualities, absorbing or reflecting only 10% to 20% of incident solar radiation and transmitting around 80% to 90% of incident solar radiation. •Low-e (low emissivity) glass decreases the glass's emittance and has a greater thermal resistance than uncoated glass because of this low emittance. •Air temperature is usually the primary factor determining comfort, while the temperature of walls, ceilings, floors, and furnishings, called radiant temperature, is also very important. Understanding Heating and Cooling Degree-Days © 2023 STRAND Dallas I Texas 972 620 8204