A | B | C | D | E | F | G | H | CH | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
 |
| Part of a series on |
| Sustainable energy |
|---|
 |
Building insulation is material used in a building (specifically the building envelope) to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation (e.g. for vibrations caused by industrial applications). Often an insulation material will be chosen for its ability to perform several of these functions at once.
Since prehistoric times, humans have created thermal insulation with materials such as animal fur and plants. With the agricultural development, earth, stone, and cave shelters arose. In the 19th century, people started to produce insulated panels and other artificial materials. Now, insulation is divided into two main categories: bulk insulation and reflective insulation. Buildings typically use a combination.
Insulation is an important economic and environmental investment for buildings. By installing insulation, buildings use less energy for heating and cooling and occupants experience less thermal variability. Retrofitting buildings with further insulation is an important climate change mitigation tactic,[1][2] especially when buildings are heated by oil, natural gas, or coal-based electricity. Local and national governments and utilities often have a mix of incentives and regulations to encourage insulation efforts on new and renovated buildings as part of efficiency programs in order to reduce grid energy use and its related environmental impacts and infrastructure costs.
Insulation
The definition of thermal insulation
Thermal insulation usually refers to the use of appropriate insulation materials and design adaptations for buildings to slow the transfer of heat through the enclosure to reduce heat loss and gain.[3] The transfer of heat is caused by the temperature difference between indoors and outdoors.[3] Heat may be transferred either by conduction, convection, or radiation. The rate of transmission is closely related to the propagating medium.[3] Heat is lost or gained by transmission through the ceilings, walls, floors, windows, and doors. This heat reduction and acquisition are usually unwelcome. It not only increases the load on the HVAC system resulting in more energy wastes but also reduces the thermal comfort of people in the building. Thermal insulation in buildings is an important factor in achieving thermal comfort for its occupants.[4] 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, polyurethane foam, vermiculite, perlite, wood fiber, plant fiber (cannabis, flax, cotton, cork, etc.), recycled cotton denim, straw, animal fiber (sheep's wool), cement, and earth or soil, reflective insulation (also known as a radiant barrier) but it can also involve a range of designs and techniques to address the main modes of heat transfer - conduction, radiation, and convection materials.
Most of the materials in the above list only retain a large amount of air or other gases between the molecules of the material. The gas conducts heat much less than the solids. These materials can form gas cavities, which can be used to insulate heat with low heat transfer efficiency. This situation also occurs in the fur of animals and birds feathers, animal hair can employ the low thermal conductivity of small pockets of gas, so as to achieve the purpose of reducing heat loss.
The effectiveness of reflective insulation (radiant barrier) is commonly evaluated by the reflectivity (emittance) of the surface with airspace facing to the heat source.
The effectiveness of bulk insulation is commonly evaluated by its R-value, of which there are two – metric (SI) (with unit K⋅W−1⋅m2) and US customary (with unit °F⋅ft2⋅h/BTU), the former being 0.176 times the latter numerically, or the reciprocal quantity the thermal conductivity or U-value W⋅K−1⋅m−2. For example, in the US the insulation standard for attics, is recommended to be at least R-38 US units, (equivalent to R-6.7 or a U value of 0.15 in SI units).[5] The equivalent standard in the UK are technically comparable, the approved document L would normally require an average U value over the roof area of 0.11 to 0.18 depending on the age of the property and the type of roof construction. Newer buildings have to meet a higher standard than those built under previous versions of the regulations. It is important to realise a single R-value or U-value does not take into account the quality of construction or local environmental factors for each building. Construction quality issues can include inadequate vapor barriers and problems with draft-proofing. In addition, the properties and density of the insulation material itself are critical. Most countries have some regime of either inspections or certification of approved installers to make sure that good standards are maintained.
History of thermal insulation
The history of thermal insulation is not so long compared with other materials, but human beings have been aware of the importance of insulation for a long time.[6] In the prehistoric time, human beings began their activity of making shelters against wild animals and heavy weather, human beings started their exploration of thermal insulation.[6][7] Prehistoric peoples built their dwellings by using the materials of animal skins, fur, and plant materials like reed, flax, and straw, these materials were first used as clothing materials, because their dwellings were temporary, they were more likely to use the materials they used in clothing, which were easy to obtain and process.[6] The materials of animal furs and plant products can hold a large amount of air between molecules which can create an air cavity to reduce the heat exchange.
Later, human beings' long life spans and the development of agriculture determined that they needed a fixed place of residence, earth-sheltered houses, stone houses, and cave dwellings began to emerge.[6][7] The high density of these materials can cause a time lag effect in thermal transfer, which can make the inside temperature change slowly. This effect keep inside of the buildings warm in winter and cool in summer, also because of the materials like earth or stone is easy to get, this design is really popular in many places like Russia, Iceland, Greenland.[6]
Organic materials were the first available to build a shelter for people to protect themselves from bad weather conditions and to help keep them warm.[7] But organic materials like animal and plant fiber cannot exist for a long time, so these natural materials cannot satisfy people's long-term need for thermal insulation. So, people began to search for substitutes which are more durable.[7][8] In the 19th century, people were no longer satisfied with using natural materials for thermal insulation, they processed the organic materials and produced the first insulated panels.[7] At the same time, more and more artificial materials start to emerge, and a large range of artificial thermal insulation materials were developed, e.g. rock wool, fiberglass, foam glass, and hollow bricks.[8]
Significance of thermal insulation
Thermal insulation can play a significant role in buildings, great demands of thermal comfort result in a large amount of energy consumed for full-heating for all rooms.[9] Around 40% of energy consumption can be attributed to the building, mainly consumed by heating or cooling. Sufficient thermal insulation is the fundamental task that ensures a healthy indoor environment and against structure damages. It is also a key factor in dealing with high energy consumption, it can reduce the heat flow through the building envelope. Good thermal insulation can also bring the following benefits to the building:
- Preventing building damage caused by the formation of moisture on the inside of the building envelope.[9] Thermal insulation makes sure that the temperatures of room surface don't fall below a critical level, which avoids condensation and the formation of mould.[9] According to the Building Damage reports, 12.7% and 14% of building damage was caused by mould problems.[10] If there is no sufficient thermal insulation in the building, high relative humidity inside the building will lead to condensation and finally result in mould problems.[10]
- Producing a comfortable thermal environment for people living in the building.[9] Good thermal insulation allows sufficiently high temperatures inside the building during the winter, and it also achieves the same level of thermal comfort by offering relatively low air temperature in the summer.[11]
- Reducing unwanted heating or cooling energy input. Thermal insulation reduces the heat exchange through the building envelope, which allows the heating and cooling machines to achieve the same indoor air temperature with less energy input.[12]
Planning and examples
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 often set minimum standards for fire safety and energy efficiency, which can be voluntarily exceeded within the context of sustainable architecture for green certifications such as LEED.
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.
United States
The thermal insulation requirements in the USA follow the ASHRAE 90.1 which is the U.S. energy standard for all commercial and some residential buildings.[13] ASHRAE 90.1 standard considers multiple perspectives such as prescriptive, building envelope types and energy cost budget. And the standard has some mandatory thermal insulation requirements.[13] All thermal insulation requirements in ASHRAE 90.1 are divided by the climate zone, it means that the amount of insulation needed for a building is determined by which climate zone the building locates. The thermal insulation requirements are shown as R-value and continuous insulation R-value as the second index.[13] The requirements for different types of walls (wood framed walls, steel framed walls, and mass walls) are shown in the table.[14]
| Wood Framed walls | Steel Framed walls | Mass walls | ||||
|---|---|---|---|---|---|---|
| zone | Non-residential | Residential | Non-Residential | Residential | Non-Residential | Residential |
| 1 | 13 | 13 | 13 | 13 | NR | 5.7 |
| 2 | 13 | 13 | 13 | 13+7.5 | 5.7 | 7.6 |
| 3 | 13 | 13 | 13+3.8 | 13+7.5 | 7.6 | 9.5 |
| 4 | 13 | 13+3.8 | 13+7.5 | 13+7.5 | 9.5 | 11.4 |
| 5 | 13+3.8 | 13+7.5 | 13+3.8 | 13+7.5 | 11.4 | 13.3 |
| 6 | 13+7.5 | 13+7.5 | 13+7.5 | 13+7.5 | 13.3 | 15.2 |
| 7 | 13+7.5 | 13+7.5 | 13+7.5 | 13+15.6 | 15.2 | 15.2 |
| 8 | 13+15.6 | 13+15.6 | 13+7.5 | 13+18.8 | 15.2 | 25.0 |
To determine whether you should add insulation, you first need to find out how much insulation you already have in your home and where. A qualified home energy auditor will include an insulation check as a routine part of a whole-house energy audit.[15] However, you can sometimes perform a self-assessment in certain areas of the home, such as attics. Here, a visual inspection, along with use of a ruler, can give you a sense of whether you may benefit from additional insulation.[16] Residential energy audits are often initiated due homeowners being alerted by a gradual increase in their utility bills which often reflects the buildings attic as being poorly insulated.[17]
An initial estimate of insulation needs in the United States can be determined by the US Department of Energy's ZIP code insulation calculator.
Russia
In Russia, the availability of abundant and cheap gas has led to poorly insulated, overheated, and inefficient consumption of energy. The Russian Center for Energy Efficiency found that Russian buildings are either over- or under-heated, and often consume up to 50 percent more heat and hot water than needed.[18][19] 53 percent of all carbon dioxide (CO2) emissions in Russia are produced through heating and generating electricity for buildings.[20] However, greenhouse gas emissions from the former Soviet Bloc are still below their 1990 levels.[citation needed]
Energy codes in the Soviet Union start to establish in 1955, norms and rules first mentioned the performance of the building envelope and heat losses, and they formed norms to regulate the energy characteristics of the building envelope.[21] And the most recent version of Russia energy code (SP 50.13330.2012) was published in 2003.[21] The energy codes of Russia were established by experts of government institutes or nongovernmental organization like ABOK. The energy code of Russia have been revised several times since 1955, the 1995 versions reduced energy depletion per square meter for heating by 20%, and the 2000 version reduced by 40%.[21] The code also has a mandatory requirement on thermal insulation of buildings accompany with some voluntary provisions, mainly focused on heat loss from the building shell.
Australia
The thermal insulation requirements of Australia follow the climate of the building location, the table below is the minimum insulation requirements based on climate, which is determined by the Building Code of Australia (BCA).[22] The building in Australia applies insulation in roofs, ceilings, external walls, and various components of the building (such as Veranda roofs in the hot climate, Bulkhead, Floors).[23] Bulkheads (wall section between ceilings which are in different heights) should have the same insulated level as the ceilings since they suffer the same temperature levels.[24] And the external walls of Australia's building should be insulated to decrease all kinds of heat transfer.[25] Besides the walls and ceilings, the Australia energy code also requires insulation for floors (not all floors).[25] Raised timber floors must have around 400mm soil clearance below the lowest timbers to provide sufficient space for insulation, and concrete slab such as suspended slabs and slab-on-ground should be insulated in the same way.
| Example locations | Minimum insulation level (total R-value (m2⋅K/W)) | |
|---|---|---|
| Roof/ceiling*[26] | Wall[26] | |
| Melbourne, Vic | 4.1 | 2.8 |
| Canberra, ACT | 4.1 | 2.8 |
| Hobart, Tas | 4.1 | 2.8 |
| Mt Gambier, SA | 4.1 | 2.8 |
| Ballarat, Vic | 4.1 | 2.8 |
| Thredbo, NSW | 6.3 | 3.8 |
| * These minimum insulation levels are higher if the roof has an upper surface absorbance value of more than 0.4.[27][page needed] | ||
China
China has various climatic characters, which are divided by geographical areas.[28] There are five climate zones in China to identify the building design include thermal insulation. (The very cold zone, cold zone, hot summer and cold winter zone, hot summer and warm winter zone and cold winter zone).[29]
Germany
Germany established its requirements of building energy efficiency in 1977, and the first energy code-the Energy Saving Ordinance (EnEV) which based on the building performance was introduced in 2002.[30] And the 2009 version of the Energy Saving Ordinance increased the minimum R-values of the thermal insulation of the building shell and introduced requirements for air-tightness tests.[31] The Energy Saving Ordinance (EnEV) 2013 clarified the requirement of thermal insulation of the ceiling. And it mentioned that if the ceiling was not fulfilled, thermal insulation will be needed in accessible ceilings over upper floor's heated rooms. [31]
Netherlands
The building decree (Bouwbesluit) of the Netherlands makes a clear distinction between home renovation or newly built houses. New builds count as completely new homes, but also new additions and extensions are considered to be new builds. Furthermore, renovations whereby at least 25% of the surface of the integral building is changed or enlarged is also considered to be a new build. Therefore, during thorough renovations, there's a chance that the new construction must meet the new building requirement for insulation of the Netherlands. If the renovation is of a smaller nature, the renovation directive applies. Examples of renovation are post-insulation of a cavity wall and post-insulation of a sloping roof against the roof boarding or under the tiles. Note that every renovation must meet the minimum Rc value of 1.3 W/(m2⋅K). If the current insulation has a higher insulation value (the legally obtained level), then this value counts as a lower limit.[32]
New Zealand
Insulation requirements for new houses and small buildings in New Zealand are set out in the Building Code and standard NZS 4128:2009.[33][34]