Energy -Efficient Buildings

Energy as an issue for building design is wide spread and deep in scope .

Pre-Design: Site Selection, Building Size, and Transportation Options

Decisions made prior to the start of design, site selection, and building size, in particular, can be major determinants of energy use and environmental impact in residents buildings as well as site selection shapes transportation energy use. A building site were many or most daily tasks can be accomplished without the automobile starts off with an energy advantage.

*Reduced expenditures for transportation, including a possible reduction in the number of vehicles per household, translating into an economic advantage, which makes housing more affordable. Building size correlates with energy use, therefor making bigger buildings typically use more energy and require more resources to construct.

Occupant Behavior and Lifestyle

Building size typically correlates to demand for power, lifestyle choices and the plug loads associated with them greatly affect energy consumption. A plug load is any electrical device plugged into a wall outlet, which includes;

1. A computer

2. Television

3. Home Theater System

4. Refrigerator

5. Washing Machine

6. DVD Player

7.Cordless Phone

8.Battery Charger

9. Video Game Console

10. Other near-essential appliances and discretionary gadgets.

Not only do these devices use electricity, many of them continue to use it even after being turned off . As the energy associated with heating, cooling, and lighting is reduced through design, the importance of plug loads increases.

Design of Low-Energy- Use Residential Buildings

To reduce energy use and environmental impacts to very low levels in residential building design, there are several objectives that apply across the board. These elements incorporate renewable energy.

Energy goals in residential design include these 5 elements:

1. Use of climate- responsive design incorporating passive techniques to reduce the energy use associated with space heating, cooling, and water heating.

2. Use of buildings envelope design that creates a good thermal boundary between interior and exterior through air sealing, insulation, elimination of thermal bridging selection of exterior finish material, and location and use of appropriate high- performance windows and glass.

3. Provision of controlled ventilation

4. Use of properly sized equipment for heating and cooling and selection of energy-efficient equipment and appliances.

5. Maximum use of renewable energy to meet the remaining demands of power.

*Site Response

Include these site factors

1. Topography

2. Landscape elements

3. Adjacent buildings

4. Micro climates

Which will affect passive design strategies for low-rise residential buildings.

*A site on the south side of the hill may have excellent opportunities to use solar energy for space heating, water heating, and electricity generation.

* A site on the north side of a hill may have limited access to sun during winter, the season when it is most needed for space heating.

Building Envelope Response

Orientation- Air conditioning was common in residences, greater care was devoted in building orientation.The widespread inclusion of air- conditioning in new homes assumes energy to run the equipment will be available at a relatively low cost. Increased global demand for energy has led to price increases for oil and natural gas and construction of new coal power plants in many parts of the world.

*From an energy-performance perspective, in all climates of North America it is preferable to elongate residential and small commercial buildings an east-west axis. This increases the percentage of buildings walls that face North and south, providing access to the sun when desired for heating.

Response to the Sun- Central to every project is response to the sun. In skin-load dominated buildings, such as residences, direct sunlight should be admitted when exterior climate is cold and rejected hot. The precise time periods when each should occur varies with climate. Controlled admission and rejection of solar heat shapes building orientation, massing forms, and the location of windows. and skylights.

*Response to the sun also influences the orientation of roofs and placements of chimneys, vents, and equipment, as these decisions affect the performance of systems for solar water heating and electricity generation.

Air Barriers- A tight building envelope that creates a continuous thermal barrier from the foundation, up through opaque wall surfaces, around doors and windows, to the peak of the roof, will greatly reduce uncontrolled movement of air between interior and exterior. This increases the effectiveness of pass design strategies and reduces energy needed to supplement passive approaches.

*An air barrier also reduces the possibility of back drafting of combustion gases from furnaces and water heaters into occupied space.

*An air barrier is an important component in creating a tight building envelope. The challenge is to design an air -barrier system, made from materials and assemblies, that is continuous from foundation to roof.

* Limiting the ability of air to move through a building assembly, an air barrier will reduce convective loss or gain.

Insulation- Insulation limits the transfer of heat across wall and ceiling assemblies, below raised floors, in crawl spaces, and at the structural slab, basements, and foundations.

* Batt insulation typically comes in rolls and is made from fiberglass or other mineral fibers. It is available in widths based on standard wall, floor, and attic framing dimensions.

*Rigid Insulation is made from fibrous materials or plastic foams that are pressed or extruded into sheets or boards. Maybe used in combination with other insulation types,

*Reflective Insulation products often referred to as radiant barriers, work by reducing radiant-heat transfer. They are typically made from shiny metals low- emissivity (low-e) surface properties.

Thermal Bridging- Heat flows from hot to cold. Across a building assembly, heat will seek the path of least resistance . This path will be through elements that are more conductive surrounding materials. If a thermally conductive path is provided across a building assembly, rapid heat transfer can occur. Lower temperatures along the path can also result in condensation on the surface of the conductive material.

*Aluminium is the most conductive. Steel also has high conductivity , however any material, or series of materials in physical contact, that creates a path across a building assembly and is significantly more conductive than surrounding materials represents a thermal bridge.

*Metals used in a wall assembly present excellent opportunities for thermal bridging. Thermal bridges are also common at the still, corners, and roof-wall junctions of traditional wood-framing buildings.

*Wood framing around doors and windows reduces insulation material and presents a thermal bridge.

Windows and Glass- Technology has improved dramatically . Double-pane windows with insulated glazing units have become the norm. Double pane units that incorporate one or more polyester films are also available. These units can match or exceed the performance of triple-pane windows without the added weight of additional panes of glass.

* The three most important metrics when selecting windows and glass are U-value (or U-factor), solar heat again coefficient (SHGC), and visible transmittance.

*The National Fenestration Rating Council is a non-profit organization created by the windows, door, and skylight industry. This tested window, door, and skylight products carry a label provides the only reliable way to understand the energy performance.

* Solar heat gain coefficient is important in relation to heat gain, largely from direct solar radiation passing through the window assembly to the building interior. Solar radiation striking a window is transmitted to the interior, reflected back to the exterior, or absorbed by the window assembly and subsequently radiated to the interior and exterior.

*Visible transmittance (VT) indicates the percentage of visible light striking the window assembly that is transmitted to the interior. Available frame materials include aluminum, wood, vinyl, cladding, hybrid-composite, and fiberglass.

Ventilation- A low - energy- use building, with a tight thermal boundary, requires a ventilation system designed to assure that energy efficiency does not compromise indoor air quality. Pressurization pushes interior air into a house without a adequate means of exhaust, the building is pressurized.

*Back drafting is when air is flowing against its intended direction, often through a flue. Back drafting pulls contaminants intended to be exhausted back in to the house.

*Uncontrolled ventilation through infiltration leaks not only wastes energy but could have serious health impacts. Because indoor air grows more polluted from contaminated in a house, fresh air must be regularly supplied.

* Good whole -house ventilation brings in fresh air and exhaust indoor air in balance to avoid pressurization or depressurization, and conserves energy. A heat recovery ventilator (HRV) uses the heat and humidity in exhaust air to temper incoming air.

If Wanting More Information About Sustainable Building This Novel Fundamentals of Integrated Design For Sustainable Building Is Worth The Read!