Building insulation is any object in the building used for isolation for any purpose. Although most of the insulation is in buildings for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation (eg for vibrations caused by industrial applications). Often the insulating material will be chosen because of its ability to perform several of these functions at once.
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Thermal insulation
Thermal insulation in buildings is an important factor for achieving thermal comfort for the inhabitants. Isolation reduces unwanted heat loss or gain and can decrease the energy requirements of the heating and cooling systems. It does not always deal with adequate ventilation problems and may or may not affect sound insulation levels. In narrow isolation can only refer to the insulation materials used to slow heat loss, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam, vermiculite, perlite, wood fiber, plant fibers (cannabis, hemp, cotton, cork, etc. ), recycled cotton denim, crop straw, animal fiber (sheep wool), cement, and soil or soil, Reflective Insulation (also known as Radiant Barrier) but can also involve a variety of designs and techniques to overcome the main mode of heat transfer - conduction , radiation and convection materials. Many of the materials on this list relate to heat conduction and convection by simply trapping large amounts of air (or other gases) in a way that produces materials that use low thermal conductivity from a small bag of gas, rather than a much higher conductivity than a typical solid. (The same gas trap principle is used in animal fur, down feathers, and in insulating cloth containing air).
The effectiveness of Reflective Isolation (Radiant Barrier) is generally evaluated by the Reflectivity (Emittance) of the surface with the air space facing the heat source.
The effectiveness of bulk isolation is generally evaluated by the R-values, which have two-metric (SI) and US custom, the first being 0.176 times the latter. For the attic, it is recommended at least should be R-38 (US metric, R-6.7). However, the R value does not take into account the quality of construction or local environmental factors for each building. Construction quality issues include inadequate steam barriers, and problems with draft-inspections. In addition, the nature and density of the insulating material itself is very important.
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Planning
How much isolation a home should have depends on building design, climate, energy costs, budgets, and personal preferences. The regional climate makes the need different. Building codes only set a minimum; isolating beyond what requires code is often recommended.
The building insulation strategy needs to be based on careful consideration of the energy transfer mode and the direction and intensity at which it moves. It can change throughout the day and from season to season. It is important to choose the right design, the right combination of materials and building techniques to suit a particular situation.
In USA
To determine whether you should add isolation, you should first find out how much insulation you already have at home and where. A qualified home energy auditor will include an insulation check as part of a routine whole-house energy audit. However, sometimes you can do your own judgment in a certain area of ​​the house, like an attic. Here, visual inspection, along with ruler use, can give you a sense of whether you can benefit from additional insulation.
The initial estimate of insulation requirements in the United States can be determined by the calculator of ZIP code of the US Department of Energy.
Russian
In Russia, the availability of abundant and inexpensive gas has resulted in inadequate energy consumption, overheating and inefficiency. The Russian Energy Efficiency Center finds that Russian buildings are either too hot or underheated, and often consume up to 50 percent more heat and hot water than is needed. 53 percent of carbon dioxide (CO 2 ) emissions in Russia are generated through heating and power generation for buildings. However, greenhouse gas emissions from former Soviet blocs are still below their 1990 levels.
Climate
Cold climate
In cold conditions, the main purpose is to reduce heat flow out of the building. The components of the building envelope - windows, doors, roofs, walls, and obstacles of air infiltration - are all important sources of heat loss; in a well-insulated home, windows will be an important source of heat transfer. Resistance to heat loss made for standard glass corresponds to an R value of about 0.17 m 2 K o /W (compared to 2-4 m 2 K o /W for batt wool glass). Losses can be reduced with good weather, bulk insulation, and minimize the amount of non-insulative glass (especially non-solar facing). Indoor heat radiation can also be a spectral selective glass loss (low-e, low-emissivity). Some isolated glass systems can multiply into three R values. Hot climate
In hot conditions, the largest source of heat energy is solar radiation. It can enter the building directly through the window or it can heat the building's skin to a higher temperature than the ambient, increasing heat transfer through the building envelope. The Solar Heat Gain Co-efficient (SHGC) (solar thermal transmittance size) of standard single glazing can be about 78-85%. Solar gain can be reduced by sufficient shading from the sun, light-colored roofs, paints and coatings that are selectively spectral (heat-reflective) and various types of insulation for the rest of the envelope. Specially coated glazing can reduce SHGC to about 10%. Radiation barriers are very effective for attic spaces in hot climates. In this application, they are much more effective in hot climates than cold climates. For heat flow down, weak convection and radiation dominate heat transfer in the air. A radiant beam must face an adequate air gap to be effective.
If the cooling air conditioner is used in a hot and humid climate, then it is important to close the building envelope. Dehumidification of moist air infiltration can waste significant energy. On the other hand, some building designs are based on effective cross ventilation as a substitute for air conditioner cooling to provide convective cooling of prevailing winds.
Orientation - passive solar design
Optimal placement of building elements (eg windows, doors, heaters) can play an important role in isolation by considering the impact of solar radiation on existing buildings and winds. Reflective laminates can help reduce passive solar heat in barns, garages, and metal buildings.
Construction
See insulated glass for a discussion of windows.
Build envelopes
Thermal envelopes define a conditioned space or stay in a house. The attic or basement may or may not be included in this area. Reducing the flow of air from the inside out can help reduce convective heat transfer significantly.
Ensuring low convective heat transfer also requires attention to building construction (weather) and the installation of the correct insulator material.
Less natural airflow into the building, more mechanical ventilation will be needed to support human comfort. High humidity can be a significant problem associated with lack of airflow, causing condensation, decaying construction materials, and encouraging the growth of microbes such as fungi and bacteria. Humidity can also drastically reduce the effectiveness of insulation by making thermal bridges (see below). Air exchange systems can be actively or passively incorporated to address this problem.
Thermal bridge
The thermal bridge is the point in the building envelope that allows heat conduction to occur. Because heat flows through the least resistant pathways, thermal bridges can contribute to poor energy performance. Thermal bridges are created when the material creates a continuous path across the temperature difference, where the heat flow is not disturbed by thermal insulation. General building materials that are poor insulators include glass and metal.
The building design may have limited capacity for isolation in some structural areas. General construction designs are based on stud walls, where thermal bridges are common in timber or steel studs and beams, which are usually tied with metal. The most common areas of sufficient lack of insulation are building corners, and areas where isolation has been removed or moved to provide space for system infrastructure, such as electrical boxes (outlets and light switches), plumbing, fire alarm equipment, etc.
Thermal bridges can also be made with uncoordinated construction, for example by closing the external wall sections before being completely isolated. The existence of an inaccessible cavity inside a non insulating wall cavity can be a thermal connecting source.
Some form of heat transfer insulation is easier when wet, and therefore can also form thermal bridges in this country.
Heat conduction can be minimized by one of the following: reducing the cross-sectional area of ​​the bridge, increasing the length of the bridge, or reducing the number of thermal bridges.
One method of reducing the effects of thermal bridges is the installation of insulation boards (eg EPS XPS boards, wooden fiber boards, etc.) Above the exterior exterior wall. Another method is to use insulated wood framing for thermal breaks inside the walls.
Installation
Building insulation during construction is much easier than retrofit, because generally insulation is hidden, and parts of buildings need to be deconstructed to reach them.
Materials
There are basically two types of building insulation - bulk insulation and reflective insulation. Most buildings use a combination of both types to create a total building insulation system. The type of insulation used is matched to create maximum resistance for each of the three forms of heat transfer building - conduction, convection, and radiation.
Conductive and Convective Insulators
Bulk insulators block conductive heat transfer and convective flow either into or out of buildings. The more solid the material, the better it will heat up. Because the air has a low density, the air is a very bad conductor and therefore makes a good insulator. Isolation to resist conductive heat transfer using air space between the fibers, inside the foam or plastic bubbles and in building cavities such as attics. This is useful in buildings that are cooled or heated actively, but can be a responsibility in passively cooled buildings; sufficient provision for cooling with ventilation or radiation is required.
Heat radiation barriers
Radiation barriers work in conjunction with the air space to reduce radiant heat transfer throughout the airspace. Radiation or reflective isolation reflects heat, not absorb it or let it pass. Radiation barriers are often seen to be used in reducing heat flow downward, as upward heat flow tends to be dominated by convection. This means that for attics, ceilings, and roofs, they are most effective in hot climates. They also have a role in reducing heat loss in cold climates. However, much larger insulation can be achieved through the addition of bulk insulators (see above).
Some selective spectral radiation barriers and preferably decrease the flow of infrared radiation compared to other wavelengths. For example low-emissivity windows (low-e) will emit short-wave infrared energy and light into the building but reflect the long-wave infrared radiation generated by interior furnishings. Similarly, special heat-reflective paint is able to reflect more heat than visible light, or vice versa.
The value of thermal emissivity may best reflect the effectiveness of the radiation barrier. Some manufacturers cite 'equivalent' R values ​​for these products but these numbers can be difficult to interpret, or even mislead, because testing R values ​​measures total heat loss in laboratory settings and does not control the type of heat loss responsible for net outcomes (radiation, conduction, convection).
Dirt or moisture film may alter the emissivity and hence the performance of the radiation barriers.
Eco-friendly insulation
Eco-friendly insulation is a term used to isolate products with limited environmental impact. A generally accepted approach to determining whether an insulating product is or not, but in fact any eco-friendly product or service is to conduct a lifecycle assessment (LCA). A number of studies compared the environmental impact of insulating materials in their applications. Comparison shows that the most important is the insulation value of the product that meets the technical requirements for the application. Only in second order, the differentiation between the material becomes relevant. The report commissioned by the Belgian government to VITO is a good example for such a study. A valuable way to describe such a result is with a spider diagram.
See also
References
External links
- Tips for Choosing Roof Insulation
- "Information source on Isolation History". solarhousehistory.com.
Source of the article : Wikipedia
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