![]() Support: to ensure strength and rigidity providing structural support against internal and external loads and forces.These functions can be divided into 3 categories: ![]() Improving the building envelope of houses is one of the best ways to get better energy efficiency.Ī building envelope serves many functions. In general, reflective surfaces can improve the building’s energy efficiency, reduce urban islands of heat, and contribute to the cooling of the planet.įor information on the importance the International Energy Agency (IEA) places on energy efficient building envelopes, see their Technology Roadmap.Figure 1. The effectiveness of cool roofs, however, varies depending on the type of roof, the insulation used, and the climate. Such cool roofs have the ability to reflect both visible and infra-red light. The simplest way to do this is to specify a white or light color roof. This will prevent heat build up in attics or air conditioned spaces where it can result in condensation. ![]() In warm climates as much heat as possible needs to deflect off the roof. Such energy balance can be achieved with double or triple glazed well insulated windows combined with architectural shading. In warm climates where cooling is needed, windows need to keep out the sun’s heat (low G-value) and, ideally, enable the building to shed heat. In cold climates, windows specified in heated buildings should retain heat (low U-value) while admitting solar radiation (high G-value). The trick is to maximize window performance while achieving energy balance. Appropriate sizing, orientation, and glazing are the primary ways to balance heat and light flow. Windows should let in as much light as possible, maximizing heat gain in winter, but minimizing it in summer. A proper air and vapor membrane will prevent future moisture and mold from forming inside insulation. Regardless of the energy that it saves, insulation installed without any moisture protection is unacceptable. Depending on the membrane, both resist water penetration, keeping exterior moisture from leaking in, even with wind-driven rain. Vapor barriers allow any moisture that finds itself within the building to escape through diffusion. Air barriers resist air movement, and therefore the movement of moisture by increasing air tightness. One solution is the use of vapor retarders such as air and vapor membranes. Modern techniques of insulating walls, floors, and roofs reduce energy loss, but it is difficult for moisture to evaporate, resulting in condensation and eventual damage. Ironically, insulation can be both beneficial and detrimental. For example, office and service-sector buildings need less insulation than residential buildings since they have a higher internal thermal load due to the density of people, and the use of electrical equipment and artificial light. ![]() While proper insulation mitigates heat loss in winter and keeps it out in summer, the type and amount of insulation should be governed by the building’s use. Walls, roofs, and floors represent the largest external areas of buildings, and they are also the routes by which heat escapes the building envelope. The challenge is to design a building with an envelope that reduces energy consumption without compromising occupants’ needs. While emphasis is placed on the building envelope’s role in energy-efficiency, it shouldn’t overshadow its other purposes, to protect the building’s occupants and give them shelter, privacy, fire protection, and comfort. Whether one chooses to call it the building envelope, shell, or enclosure, the boundary between a building’s conditioned interior and the outdoors plays a critical part in how much energy the building will require for heating and cooling, as well as comfort levels, lighting, and ventilation. Several European Union countries have adopted policies that mandate the construction of net-zero energy buildings these policies will be enforced by the end of the decade. The new construction phase offers the best and most practical opportunity to incorporate passive heating and cooling designs that take advantage of energy efficient building materials. Recently, the focus has been on the building envelope. With a 150% predicted increase by 2050 for cooling alone, it’s hardly surprising that the question of how to design energy efficient buildings is echoing around the planet. Space heating and cooling accounts for over 30% of global energy consumption.
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