Building insulation
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.
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.
), 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.
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.
[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.
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.
[13] ASHRAE 90.1 standard considers multiple perspectives such as prescriptive, building envelope types and energy cost budget.
In Russia, the availability of abundant and cheap gas has led to poorly insulated, overheated, and inefficient consumption of energy.
[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.
[U-Value must be under 0.24 W/(m2⋅K)][31] The building decree (Bouwbesluit) of the Netherlands makes a clear distinction between home renovation or newly built houses.
[34] Insulation requirements are specified in the Building regulations and in England and Wales the technical content is published as Approved Documents Document L defines thermal requirements, and while setting minimum standards can allow for the U values for elements such as roofs and walls to be traded off against other factors such as the type of heating system in a whole building energy use assessment.
The standards have been revised several times in recent years, requiring more efficient use of energy as the UK moves towards a low-carbon economy.
Losses can be reduced by good weatherisation, bulk insulation, and minimising the amount of non-insulative (particularly non-solar facing) glazing.
[40] The common materials that used to produce Core panels are fumed and precipitated silica, open-cell polyurethane (PU), and different types of fiberglass.
[42] But the difficulties in processing and low productivity limit the development of Aerogels,[41] the cost price of this material still remains at a high level.
[44][45] Typically, aerogels have low transmission and appear hazy, even amongst those considered transparent, which is why they have generally been reserved to wall insulation applications.
[46] Eldho Abraham, a researcher at the University of Colorado Boulder, recently demonstrated the capabilities of aerogels by designing a silanized cellulose aerogel (SiCellA) which offers near 99% visible transmission in addition to thermal conductivities which effectively reject or retain heat depending on the interior environment, akin to heating/cooling alterations.
This opens the door not only to aerogels, but also more general wood-based materials implementation in an effort to assist sustainable design alternatives with compounding energy saving effects.
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.
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.
In hot dry climate regions like Egypt and Africa, thermal comfort in the summer is the main question, nearly half of energy consumption in urban area is depleted by air conditioning systems to satisfy peoples' demand for thermal comfort, many developing countries in hot dry climate region suffer a shortage of electricity in the summer due to the increasing use of cooling machines.
[58] Ensuring low convective heat transfer also requires attention to building construction (weatherization) and the correct installation of insulative materials.
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.
Thermal bridges can also be created by uncoordinated construction, for example by closing off parts of external walls before they are fully insulated.
Depending on the country there are different regulations as to which type of insulation is the best alternative for buildings, considering energy efficiency and environmental factors.
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.
Insulation to resist conductive heat transfer uses air spaces between fibers, inside foam or plastic bubbles and in building cavities like the attic.
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).
