Stardust Homes

Article by jekky

Thermal Insulation Thermal insulation in buildings is an important factor to achieving thermal comfort for its occupants Insulation reduces unwanted heat loss or gain and can decrease the energy demands of heating and cooling systems It does not necessarily deal with issues of adequate ventilation and may or may not affect the level of sound insulation In a narrow sense insulation can just refer to the insulation materials employed to slow heat loss such as cellulose glass wool rock wool polystyrene urethane foam vermiculite and earth or soil But it can also involve a range of designs and techniques to address the main modes of heat transfer conduction radiation and convection materials The effectiveness of insulation is commonly evaluated by its R value However an R value does not take into account the quality of construction or local environmental factors for each building Construction quality issues include inadequate vapour barriers and problems with draft proofing In addition the properties and density of the insulation material itself is critical For example according to Leah Twings Quality Compliance Manager of Textrafine Insulation fiberglass insulation materials made from short strands of glass layered over each other is not as durable as insulation made from long entangled strands of glass Planning How much insulation a house should have depends on building design climate energy costs budget and personal preference Regional climates make for different requirements Building codes specify only the bare minimum insulating beyond what code requires is often recommended The insulation strategy of a building needs to be based on a careful consideration of the mode of energy transfer and the direction and intensity in which it moves This may alter throughout the day and from season to season It is important to choose an appropriate design the correct combination of materials and building techniques to suit the particular situation In the USA An initial estimate of insulation needs in the United States can be determined by the US Department of Energy s ZIP code insulation calculator International Russia In Russia the luxury of cheap gas has led to poorly insulated overheated and inefficient consumers of energy The Russian Center for Energy Efficiency found that Russian buildings are either over or under heated often consume up to 50 percent more heat and hot water than needed Fifty three percent of all carbon dioxide CO2 emissions in Russia are produced through heating and generating electricity for buildings However Green House Gas GHG emissions from the Soviet Bloc are still below their 1990 levels the corresponding number of credits that could be sold under the Kyoto Treaty are called Hot Air Climate Cold climates Cross section of home insulation In cold conditions the main aim is to reduce heat flow out of the building The components of the building envelope windows doors roofs walls and air infiltration barriers are all important sources of heat loss in an otherwise well insulated home windows will then become an important source of heat transfer The resistance to conducted heat loss for standard glazing corresponds to an R value of about 0 17W m2 Ko compared to 2 4W m2 Ko for glasswool batts Losses can be reduced by good weatherisation bulk insulation and minimising the amount of non insulative particularly non solar facing glazing Indoor thermal radiation can also be retarded with spectrally selective low e low emissivity glazing Some insulated glazing systems can double to triple R values Hot climates In hot conditions the greatest source of heat energy is solar radiation This can enter buildings directly through windows or it can heat the building shell to a higher temperature than the ambient increasing the heat transfer through the building envelope The Solar Heat Gain Co efficient SGHC a measure of solar heat transmittance of standard single glazing can be around 78 85 Solar gain can be reduced by adequate shading from the sun light coloured roofing spectrally selective heat reflective paints and coatings and various types of insulation for the rest of the envelope Specially coated glazing can reduce SHGC to around 10 Radiant barriers are highly effective for attic spaces in hot climates In this application they are much more effective in hot climates than cold climates For downward heat flow convection is weak and radiation dominates heat transfer across an air space Radiant barriers must face an adequate air gap to be effective If refrigerative air conditioning is employed in a hot humid climate then it is particularly important to seal the building envelope Dehumidification of humid air infiltration can waste significant energy On the other hand some building designs are based on effective cross ventilation instead of refrigerative air conditioning to provide convective cooling from prevailing breezes Orientation Passive Solar Design Main article Passive solar design Optimal placement of building elements e g windows doors heaters can play a significant role in insulation by considering the impact of solar radiation on the building and the prevailing breezes See Passive Solar Design Reflective laminates can help reduce passive solar heat in pole barns garages and metal buildings Construction See insulated glass for discussion of windows Building envelope The thermal envelope defines the conditioned or living space in a house The attic or basement may or may not be included in this area Reducing airflow from inside to outside can help to reduce convective heat transfer significantly Ensuring low convective heat transfer also requires attention to building construction weatherization and the correct installation of insulative materials The less natural airflow into a building the more mechanical ventilation will be required to support human comfort High humidity can be a significant issue associated with lack of airflow causing condensation rotting construction materials and encouraging microbial growth such as mould and bacteria Moisture can also drastically reduce the effectiveness of insulation by creating a thermal bridge see below Air exchange systems can be actively or passively incorporated to address these problems Thermal bridge Thermal bridges are points in the building envelope that allow heat conduction to occur Since heat flows through the path of least resistance thermal bridges can contribute to poor energy performance A thermal bridge is created when materials create a continuous path across a temperature difference in which the heat flow is not interrupted by thermal insulation Common building materials that are poor insulators include glass and metal A building design may have limited capacity for insulation in some areas of the structure A common construction design is based on stud walls in which thermal bridges are common in wood or steel studs and joists which are typically fastened with metal Notable areas that most commonly lack sufficient insulation are the corners of buildings and areas where insulation has been removed or displaced to make room for system infrastructure such as electrical boxes outlets and light switches plumbing fire alarm equipment etc Thermal bridges can also be created by uncoordinated construction for example by closing off parts of external walls before they are fully insulated The existence of inaccessible voids within the wall cavity which are devoid of insulation can be a source of thermal bridging Some forms of insulation transfer heat more readily when wet and can therefore also form a thermal bridge in this state The heat conduction can be minimized by any of the following reducing the cross sectional area of the bridges increasing the bridge length or decreasing the number of thermal bridges Materials Main article Building insulation materials see Thermal insulation There are essentially two types of building insulation Bulk Insulation and Reflective Insulation Most buildings use a combination of both types to make up a total building insulation system The type of insulation used is matched to create maximum resistance to each of the three forms of building heat transfer Conduction Convection and Radiation Conductive and convective insulators Bulk insulation Bulk insulators block conductive heat transfer and convective flow either into or out of a building The denser a material is the better it will conduct heat Because air has such low density air is a very poor conductor and therefore makes a good insulator Insulation to resist conductive heat transfer uses air spaces between fibers inside foam or plastic bubbles and in building cavities like the attic This is beneficial in an actively cooled or heated building but can be a liability in a passively cooled building adequate provisions for cooling by ventilation or radiation are needed Radiant heat barriers Main article Radiant barrier Radiant barriers work in conjunction with an air space to reduce radiant heat transfer across the air space Radiant or reflective insulation reflects heat instead of either absorbing it or letting it pass through Radiant barriers are often seen used in reducing downward heat flow because 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 losses in cool climates However much greater insulation can be achieved through the addition of bulk insulators see above Some radiant barriers are spectrally selective and will preferentially reduce the flow of infra red radiation in comparison to other wavelengths For instance low emissivity low e windows will transmit light and short wave infra red energy into a building but reflect back the long wave infra red radiation generated by interior furnishings Similarly special heat reflective paints are able to reflect more heat than visible light or vice versa Thermal emissivity values probably best reflect the effectiveness of radiant barriers Some manufacturers quote an equivalent R value for these products but these figures can be difficult to interpret or even misleading since R value testing measures total heat loss in a laboratory setting and does not control the type of heat loss responsible for the net result radiation conduction convection film of dirt or moisture can alter the emissivity and hence the performance of radiant barriers Installation of insulation Main article Installing building insulation Insulating buildings during construction is much easier than retrofitting as generally the insulation is hidden and parts of the building need to be deconstructed to reach them Home energy audit A home energy audit is a service where the energy efficiency of a house is evaluated by a person using professional equipment such as blower doors and infra red cameras with the aim to suggest the best ways to improve energy efficiency in heating and cooling the house This kind of service can often be facilitated by Public utility companies or their energy conservation department Independent private sector companies such as energy services company insulation contractor or air sealing specialist US State energy office The examples and perspective in this article may not represent a worldwide view of the subject Please improve this article and discuss the issue on the talk page Utility companies are usually eager to provide this service as well as loans and other incentives to insulate They also often provide incentives to switch for example if you are an oil customer considering switching to natural gas It is possible to obtain simple energy audits without the blower tests from some utilities and US state agencies for free An example is the Energy Trust of Oregon program which provides simplified energy audits and compact fluorescents to homeowners at no cost Where to look for insulation recommendations Local building inspector office Local or state building codes US Department of Energy U S A Home Energy Rating Schemes Australia Green Building Insulation USA Websites for any of the above See also Energy portal Thermal insulation R value insulation includes a list of insulations with R values Installing building insulation Thermal mass Eco friendly Insulation Materials Building insulation materials Window insulation film Wool insulation Mineral wool Packing firestopping Greensulate Design Cool roof Green roof Passive house Zero energy building Superinsulation Low energy building Passive solar design Passive solar building design Construction Building construction Building Envelope Weatherization Other Condensation HVAC Ventilation References BSD 011 Thermal Control in Buildings Your Home Technical Manual 1 6a Insulation Overview http knowledge allianz com en globalissues energy_co2 energy_efficiency green_buildings_climate html Insulating and heating your home efficiently 160 Directgov Environment and greener living Reduce Your Heating Bills This Winter Overlooked Sources of Heat Loss in the Home Your Home Technical Manual 1 8a Glazing Overview a b http www wers net documents Rehau_NFRC_Dec_2007 pdf http www ecopink com au pdf Pink_Batts pdf At latitudes less than 45 degrees winter insolation rarely falls below 1kWh m2 day and may rise above 7kWh m2 day during summer Source www gaisma com In comparison the power output of an average domestic bar radiator is about 1kW Therefore the amount of thermal radiation falling upon a 200m2 house could vary between 200 1400 home heaters operating continuously for one hour Re radiation of heat into the roof space during summer can cause sol air temperatures to reach 60Co a b Comparative Evaluation of the Impact of Roofing Systems on Residential Cooling Energy Demand in Florida Windows Energy Ratings Scheme WERS http www gjames com au brochure glassperformance pdf Florida Solar Energy Center BERC Airtightness DOE Building Technologies Program Building Envelope V E Framing Design of Low C