Editing Thermal insulation (section)

==Applications==

===Clothing and natural animal insulation in birds and mammals===
{{Main|Clothing insulation}}
Gases possess poor [[thermal conduction]] properties compared to liquids and solids and thus make good insulation material if they can be trapped. In order to further augment the effectiveness of a gas (such as air), it may be disrupted into small cells, which cannot effectively transfer heat by [[natural convection]]. Convection involves a larger bulk flow of gas driven by buoyancy and temperature differences, and it does not work well in small cells where there is little density difference to drive it, and the high surface-to-volume ratios of the small cells retards gas flow in them by means of viscous [[drag (physics)|drag]].

In order to accomplish small gas cell formation in man-made thermal insulation, glass and polymer materials can be used to trap air in a foam-like structure. This principle is used industrially in building and piping insulation such as ([[glass wool]]), [[cellulose]], [[rock wool]], [[polystyrene]] foam (styrofoam), [[polyurethane|urethane foam]], [[vermiculite]], [[perlite]], and [[cork (material)|cork]]. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers and fleece.

The air-trapping property is also the insulation principle employed by [[homeothermic]] animals to stay warm, for example [[down feather]]s, and insulating hair such as natural sheep's [[wool]]. In both cases the primary insulating material is air, and the polymer used for trapping the air is natural [[keratin]] protein.

===Buildings===
{{main|Building insulation}}
[[File:Hallway insulation.jpg|thumb|right|Common insulation applications in [[apartment]] [[building]] in [[Ontario]], Canada.]]
[[File:06 Thermal insulation retrofit works on a department store building with mineral wool and Aluthermo aluminium composite mat.jpg|thumb|right|Thermal insulation retrofit works on a department store building in [[Poland]]]]
Maintaining acceptable temperatures in buildings (by heating and cooling) uses a large proportion of [[global energy consumption]]. Building insulations also commonly use the principle of small trapped air-cells as explained above, e.g. fiberglass (specifically [[glass wool]]), [[cellulose]], [[rock wool]], [[polystyrene]] foam, [[polyurethane|urethane foam]], [[vermiculite]], [[perlite]], [[cork (material)|cork]], etc.  For a period of time, [[asbestos]] was also used, however, it caused health problems. 

[[Window insulation film]] can be applied in [[weatherization]] applications to reduce incoming thermal radiation in summer and loss in winter.

When well insulated, a [[building]] is:
* energy efficient and cheaper to keep warm in the winter, or cool in the summer. [[Efficient energy use|Energy efficiency]] will lead to a reduced [[carbon footprint]].
* more comfortable because there is uniform temperatures throughout the space. There is less temperature gradient both vertically (between ankle height and head height) and horizontally from exterior walls, ceilings and windows to the interior walls, thus producing a more comfortable occupant environment when outside temperatures are extremely cold or hot.

In industry, energy has to be expended to raise, lower, or maintain the temperature of objects or process fluids.  If these are not insulated, this increases the energy requirements of a process, and therefore the cost and environmental impact.

===Mechanical systems===
{{main|Pipe insulation}}
[[File:Water Boiler Supply and Return Piping.jpg|thumb|Insulated hot water supply and return hydronic piping on a gas-fired boiler]]
[[File:Coloured ceramic thermal barrier coating on exhaust component.jpg|thumb|Thermal insulation applied to exhaust component by means of plasma spraying]]
Space heating and cooling systems distribute heat throughout buildings by means of pipes or ductwork. Insulating these pipes using pipe insulation reduces energy into unoccupied rooms and prevents [[condensation]] from occurring on cold and chilled pipework.

Pipe insulation is also used on water supply pipework to help delay pipe freezing for an acceptable length of time.

Mechanical insulation is commonly installed in industrial and commercial facilities.

=== Passive radiative cooling surfaces ===
Thermal insulation has been found to improve the [[thermal emittance]] of [[passive radiative cooling]] surfaces by increasing the surface's ability to lower temperatures below ambient under direct solar intensity.<ref name=":0">{{Cite journal |last1=Leroy |first1=A. |last2=Bhatia |first2=B. |last3=Kelsall |first3=C.C. |last4=Castillejo-Cuberos |first4=A.M. |last5=Capua H. |first5=Di |last6=Zhang |first6=L. |last7=Guzman |first7=A.M. |last8=Wang |first8=E.N. |date=October 2019 |title=High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel |journal=Materials Science |volume=5 |issue=10 |pages=eaat9480 |doi=10.1126/sciadv.aat9480 |pmid=31692957 |pmc=6821464 |bibcode=2019SciA....5.9480L }}</ref> Different materials may be used for thermal insulation, including [[polyethylene]] [[Aerogel|aerogels]] that reduce solar absorption and parasitic heat gain which may improve the emitter's performance by over 20%.<ref name=":0" /> Other aerogels also exhibited strong thermal insulation performance for radiative cooling surfaces, including a [[silica-alumina]] [[Nanofiber|nanofibrous]] aerogel.<ref name=":27">{{Cite journal |last1=Li |first1=Tao |last2=Sun |first2=Haoyang |last3=Yang |first3=Meng |last4=Zhang |first4=Chentao |last5=Lv |first5=Sha |last6=Li |first6=Bin |last7=Chen |first7=Longhao |last8=Sun |first8=Dazhi |title=All-Ceramic, Compressible and Scalable Nanofibrous Aerogels for Subambient Daytime Radiative Cooling |url=https://www.sciencedirect.com/science/article/abs/pii/S138589472204997X |journal=Chemical Engineering Journal |year=2023 |volume=452 |page=139518 |doi=10.1016/j.cej.2022.139518 |bibcode=2023ChEnJ.45239518L |via=Elsevier Science Direct}}</ref>

=== Refrigeration ===
A [[refrigerator]] consists of a heat pump and a thermally insulated compartment.<ref name="bbc.co.uk">[https://web.archive.org/web/20090213114520/http://www.bbc.co.uk/bloom/actions/fridgefreezertips.shtml Keep your fridge-freezer clean and ice-free]. ''BBC''. 30 April 2008</ref>

===Spacecraft===
[[Image:Huygens thermal multilayer insulation.jpg|thumb|right|Thermal insulation on the [[Huygens probe]]]]
[[File:Aircraft cabin insulation in a B747-8.jpg|thumb|Cabin insulation of a [[Boeing 747-8]] airliner]]
Launch and re-entry place severe mechanical stresses on spacecraft, so the strength of an insulator is critically important; the failure of insulating tiles on the [[Space Shuttle Columbia|Space Shuttle ''Columbia'']] caused the shuttle airframe to overheat and break apart during reentry, killing the astronauts on board. Re-entry through the atmosphere generates very high temperatures due to compression of the air at high speeds. Insulators must meet demanding physical properties beyond their thermal transfer retardant properties. Examples of insulation used on spacecraft include reinforced [[carbon]]-carbon composite nose cone and [[silicon dioxide|silica]] fiber tiles of the [[Space Shuttle]]. See also [[Insulative paint]].

===Automotive===
{{main|Exhaust Heat Management}}
[[Internal combustion engine]]s produce a lot of heat during their combustion cycle. This can have a negative effect when it reaches various heat-sensitive components such as sensors, batteries, and starter motors. As a result, thermal insulation is necessary to prevent the heat from the exhaust from reaching these components.

High performance cars often use thermal insulation as a means to increase engine performance.

===Aerospace===
Aircraft engines such as turbojets use thermal barriers on components such as the combuster sections/afterburner for heat protection.<ref>{{cite web | url=https://patents.google.com/patent/US6361273B1/en | title=Heat shield for a gas turbine }}</ref><ref>{{cite web | url=https://www.jbc-tech.com/markets/heat-shielding/ | title=Heat Shielding }}</ref><ref>{{cite web | url=https://www.dbm-technologie.co.uk/.php?dbm=Aerospace-applications | title=Thermal acoustic insulation for the aeronautical and spatial market }}</ref>

===Greenhouse===
{{main|Greenhouse}}

Thermal insulation is integral to greenhouse design, enabling controlled environments for plant growth and energy efficiency. Common insulation techniques include the use of double-layer films and multi-wall polycarbonate panels, which trap air between layers to reduce heat transfer while maintaining sufficient light transmission for photosynthesis. These measures improve energy efficiency and support year-round crop production, significantly reducing heating costs.