Advances in Materials

Buildings account for nearly one-third of overall energy consumption in today’s world energy status, in which a considerable part is used for indoor conditioning. Building cooling loads consist of heat gains through opaque external surfaces and fenestration areas of the building and internal heat gains. Ensuring the effective thermal insulation in regions, where the cooling requirement of building with respect to heating requirement is dominant, is very important from the aspect of energy economy. Architectural and physical properties of building, such as thermal mass, structural material and its shape, are the most important parameters, which influence the space-cooling load. Another parameter is local climate. Different effective techniques such as free cooling, natural ventilation, thermal mass and night cooling can be used in order to reduce the cooling load. Therefore, a significant energy saving (more than 50% as compared to an existing building) can be achieved. On the other hand, thermal insulation is applied for reducing of heat loss or/and gain in buildings through the envelope. Yearly building cooling load and the peak cooling demand of building can be reduced significantly in the thermally insulated buildings located in hot dry and hot humid regions. Therefore, reducing energy use for space cooling in buildings is a key measure to energy conservation and environmental protection. The main objective is to reveal the influence of the building thermal insulation on the annual energy consumption of the cooling system especially in hot and humid regions. Thus, Energy efficiency enhancement of buildings components and technologies is a key priority, given the essential need for carbon neutrality and climate change mitigation around the world.

Exterior wall insulation is considered as the most effective technology for protecting buildings against continual ambient fluctuations. The selection of appropriate insulating materials is one of the primary methods for lowering a building’s energy usage. The thermal performance of insulating materials can directly influence the shape of the building energy consumption and efficiently reduce internal and external heat transfers from building envelopes, assisting in the provision of more desired indoor thermal comfort provision for occupants. This information about advances in HVAC insulation technology will be useful to professionals in the design and execution of exterior wall thermal insulation under various climate conditions to achieve the desired energy savings, emission reductions, and cost savings.

Types of Insulation Materials

The insulation materials are classified into three main categories, as indicated in Figure 1, depending on material composition, material technology, and material sustainability index.

Fiberglass

Fiberglass is one of the most common building insulation materials and is often used for air conditioning insulation. This substance is made of glass fibers, blown or spun to form insulation. It’s also worth mentioning that fiberglass can be used as loose-fill insulation, which makes it a viable option for attics and crawlspaces. Essentially — any small space that is difficult to reach. When fiberglass is made out of blankets or rolls and has a facing, it can act as a vapour barrier. These vapour barriers prevent water vapour from getting into the walls of your home. In many cases, facings are constructed out of kraft paper or foil-kraft paper.

• Advantage: Most common, non-flammable, resistant to moisture damage, and effectively blocks heat flow.
• Limitations: It can be highly irritating to your skin and lungs if you come in direct contact with it.

Cellulose

The cellulose is found in more eco-friendly type of thermal insulation. This type of insulation material contains up to 85% of recycled materials that are shredded and fiberized to become insulation (Figure 2). Cellulose is often made into loose-fill insulation and can fit into compact spaces.

• Advantage: Environmentally friendly as it is made from organic, recycled paper and cardboard.
• Disadvantage: While it is treated to be resistant to moisture and pests, its insulating ability decreases significantly when it absorbs moisture. As a result, cellulose insulation needs to be replaced about every five years.

Rock Wool (Also Called Mineral Wool)

There are two types of mineral wool: slag wool and rock wool. Rock wool is composed of natural materials such as basalt or diabase. Mineral wools are types of insulation materials that are often formed into batts insulation.

• Advantage: Fire resistant since it is able to withstand extremely high temperatures, as well as noise resistant. Comparable to fiberglass.
• Disadvantage: Rock wool is more expensive and not as common as other insulating materials.

Spray Foam

There are two varieties of spray foam to choose from – open-cell foam and closed-cell foam. This type of thermal insulation is constructed of chemicals that create a foam-like material and are ideal for unfinished walls. As the name suggests, sprayed foam insulation is often sprayed or injected into an area that expands and solidifies.

There are various pros and cons associated with these insulation products. Like loose-fill insulation, it can be helpful to know that spray foam insulation is ideal for hard-to-reach areas such as attics and crawl spaces. Hopefully, the advantages and disadvantages listed below will help you determine if spray foam is the best insulation material for your specific needs.

• Advantage: Sprayed/foamed materials are excellent for enclosing and insulating existing walls, abnormally shaped areas, or working around obstructions. They are also energy efficient.
• Disadvantage: Liquid polyurethane foam isn’t very thick and contracts with age, pulling away from the framing.

Foam Boards

Foam boards are another type of thermal insulation material made into common household insulators. This material is ideal for unfinished walls, such as foundation and basement walls. There are many reasons why a homeowner might consider installing foam board insulation. For example, this particular product is available in a wide variety of thicknesses and customizations, making it an ideal choice for many different applications. Foam boards can also be equipped with facings to create a vapour barrier.

• Advantage: Can insulate almost any area of your home.
• Disadvantage: Can be costly when installed on finished/existing walls.

Natural Fibers

Natural fibers — such as sheep’s wool, cotton, and straw — can be used as a type of thermal insulation for your home. However, these materials must first undergo a chemical treatment before being used as insulation.

• Advantage: Compromised of recycled natural materials.
• Disadvantage: Natural fiber materials must first undergo a chemical treatment before being used as insulation.

Aerogel

Aerogel is a translucent synthetic substance with a huge internal surface area, high porosity, and low density. Commonly, aerogel is synthesized by the sol-gel method, which creates a highly porous nanostructure, reducing conduction and convection heat transfers through the material. Synthetic materials exhibit the lowest thermal conductivity, refractive index, sound speed, and dielectric constant of any solid evaluated. These characteristics are attributed to their unique microstructure, which comprises particle diameters of 1–20 nm, pore widths of 2–50 nm, and porosity of up to 90%.

Vacuum Insulation Board

Vacuum insulation board is a novel environmentally friendly, high-efficiency insulation material with thermal conductivity of one-fifth to one-tenth of that of traditional insulation materials. Vacuum insulations are gradually being employed in several applications, such as construction, refrigerators, cold storage, pipeline insulation, cold chain logistics, etc., due to their excellent properties. Vacuum insulation materials, on the other hand, can be used to replace vacuum glasses in building windows for improved thermal insulation. The results demonstrate that the insulating material with a vacuum pressure of 10 pa in the interlayer can provide a better insulation effect, but at a much higher cost. Vacuum insulation products that employ getters ensure that the material properties remain unchanged after long-term usage, which improves the service life of vacuum insulation materials. A vacuum insulation board is an excellent insulation material; however, it is essential to ensure the structure of the insulation board is stable since its elements are insulated by vacuum. Reducing manufacturing cost and prolonging service life have always been major
research topics.

Additional Ways to Increase HVAC Energy Savings

Seal Windows and Doors

When we increase air sealing efforts, we can prevent air from seeping out. This way, HVAC system won’t have to work as hard to keep indoor space warm or cool. These simple measures can improve HVAC system’s energy efficiency, potentially helping us to waste less energy and save money on HVAC energy bills.

Upgrade Your Thermostat

We can control smart thermostat straight from using mobile phone remotely, which makes it easy to save energy while away from home. Although a new thermostat can help to control heating or cooling the indoor air in built atmosphere, it’s important to realize that smart thermostat can have so many more benefits besides this.

Install a High-Quality and Right Capacity HVAC System

Insulation isn’t the only way to save on your energy costs but having the right capacity of air conditioning system for home or workplace is a must to meet residential and commercial HVAC needs.

Conclusion

Insulation materials play an essential role in building energy efficiency, and all insulation materials have a number of specific characteristics. The main characteristics of insulation materials can be summarized as thermal conductivity, which is the most crucial factor since it influences the thermal insulation effect of materials. Using materials with lower thermal conductivity can help reduce the thickness of the external wall insulation layer while still providing the same energy saving.

At the end of the life cycle, recycling rates should also be improved. Besides, efforts should be continued to develop materials with lower thermal conductivity while also focusing on sustainability aspects. From the literature, it has been found that some sustainable materials have the same thermal insulation effect as traditional thermal insulation materials, indicating that it is essential to investigate how to improve the durability and suitability of sustainable insulation materials so that they can be widely used in buildings.

Dr. (Prof.) D.B. Jani received Ph.D. in Thermal Science (Mechanical Engineering) from Indian Institute of Technology (IIT) Roorkee. Currently he is a recognized Ph.D. Supervisor at Gujarat Technological University (GTU). He has published more than 180 Research Articles in reputed International Conferences and Journals. He has also published 5 reputed books in the area of thermal engineering. Presently, he is an Associate Professor at GEC, Dahod, Gujarat Technological University, GTU, Ahmedabad (Education Department, State of Gujarat, India). His area of research is Desiccant cooling, ANN, TRNSYS, and Exergy.