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An Overview of the Basic Types of Roof Insulation

Types of Roof Insulation
Nowadays, you have umpteen choices when it comes to roof insulation materials. This post provides a brief overview about the basic types of roof insulation and the materials used for this purpose.
Sonia Nair
Last Updated: Mar 1, 2018
Choose a roof insulation according to the type of the roof, local climate, local laws, the price and R-value of the product, and its impact on the environment as well as the health of the inhabitants.
A well-insulated roof keeps the home warm during winters and cool during summers. By installing a roof insulation, you could reduce your electric bills and save energy. The effectiveness of the insulation material is counted in R-value. The higher the R-value, the greater the efficiency of the product. This figure indicates the thermal resistance of the material. In other words, the ability of the material to resist transfer of heat through it. Usually, heat travels from hotter to cooler areas. During hot weather, the roof insulation traps heat from outside and prevents it from entering the interiors. On the other hand, it traps the inner heat during cold weather, and keeps the interiors warm.

Various materials are used for insulating roofs, attics, and lofts. They include fiberglass, rock wool, natural wool, plastic fiber, polyurethane foam, nitrogen-based urea-formaldehyde (UF) foam, cementitious foam, natural fibers, and straw panels. These materials are available in different types that can be installed in different ways.
Roof Insulation Types
Blankets: Rolls and Batts
Blanket insulation comes as flexible rolls and batts made of natural, plastic, or mineral fibers. They can be easily fitted in between studs, joists, and beams. Though most of these products fit well into the standard spacing of studs, joists, and beams; they have to be trimmed and shaped in case of obstructions or other fixtures. In some cases, the spacing may not be standard, and the material needs to be sized properly before installation.
This type of insulation is available with facings that act as vapor barriers. The R-value may vary with the type of insulation material, and its thickness. This is the most common and widely used type of roof insulation.
Fiberglass roof insulation
As the name rightly suggests, this insulation is nothing other than small granules or fibers that can be used to fill spaces. Materials like cellulose, fiberglass, mineral wool, cork granules, vermiculite, etc., are used for this purpose. They are ideal for insulating existing structures and those locations, where other materials cannot be installed. They can also be used as top-up materials for an existing insulation.
The main advantage of a loose-fill insulation is that it can fill even the small spaces where sheets and panels may not fit. While some of these materials have to be poured, others need to be blown in using pneumatic equipment. Before installing this insulation, seal the cracks and crevices in the ceiling and isolate heat sources.
Foam Insulation
Foam Roof Insulation
This insulation is available as liquid foam that can be sprayed, injected, or poured. Polyurethane, polyisocyanurate, and cementitious foam are some of the commonly used materials. The materials are mixed with foaming agents, before use. When the materials come in contact with each other, they merge and expand. This foam is sprayed on to roof tiles, concrete slabs, wall cavities, enclosed walls, and unfinished attic floors. In some types, the liquid foam expands and hardens, once it is sprayed.
The advantage of this spray foam insulation is that the material fills small spaces, cracks, and crevices. While open-cell foam is not very strong and do not resist water, the closed-cell type is water-resistant and tough. Foam insulation is also available as panels or boards made of polystyrene, polyurethane, and polyisocyanurate. While rigid foam boards are widely used for insulating roofs, there are speculations about the safety of spray foam insulation for roofs.
Rigid Fiber Boards
Fiber wool insulation
Usually, these firm boards are made of fiberglass or mineral wool, and are widely used for insulating roofs. The main advantage of this type of roof insulation is that it can withstand high temperatures. It is mainly used for insulating air ducts and has a greater R-value. This insulation is also available with a reflective foil facing to inhibit heat flow.
Structural Insulated Panels
These prefabricated insulation panels are sturdy, lightweight, and easy to install. They have high R-values and greater energy savings. Each panel has a thick foam board fixed in between two structural facing materials like oriented strand boards. The foam board is glued to the outer sheathings, and the panel is pressed for a better bonding. Different materials are used for making structural insulated panels (SIPs). Even customized panels are made according to the requirements of customers. This insulation is mainly used in new constructions and unfinished roofs.
Radiant Barriers, Reflective Insulation
Unlike other types of roof insulation that hinder transfer of heat through conduction and convection, a radiant barrier reduces radiant heat. Radiant barriers have reflective materials that reflect heat, and are usually used in attics. When installed under the roof, the radiant barrier along with the reflective insulation prevents transfer of heat from the roof to the attic. For best results, the insulation must be perpendicular to the flow of radiant energy. The reflective material must face the inner surface of the attic. Dust accumulation may affect the functioning of the reflective surfaces.
Radiant barriers roof insulation
Radiant barriers come with reflective material like aluminum foil. Foil-faced wood products are very popular as radiant barriers. Aluminum foil with backings like kraft paper or plastic film, is used as reflective insulation that is usually installed in between roof rafters and floor joists.
Roof Insulation Materials
Fiberglass comes in the form of rolls or sheets to be installed on the loft of the roof. You may also get precut rigid fiberglass boards, which are available in a wide range of R-values, according to the needs of the customers. Nowadays, fiberglass is also available as loose fibers, which have to be mixed with adhesives and blown into the area. Some manufacturers have introduced a different version, which uses two types of glass to form a blown variety that can curl naturally.
There is no need of adhesive as the fibers stick together when they curl. It has been observed that, this new entrant is more safe to work with, and is also environment-friendly.
Cellulose Fibers come in many forms, and comprise recycled paper treated with fire retardants. In case of roof insulation, cellulose is the second most popular choice after fiberglass; and is believed to be more efficient than the other. The stabilized form of cellulose is mainly used to insulate roofs. Even though the quality of the product may vary with individual brands, cellulose is one of the cheapest roof insulation materials and is also easy to install.
Foam insulation comes in different types. Polyurethane is the most commonly used type of foam insulation. Almost all types of foam insulation have fire resistant properties. Other types of roof insulation materials include sheep wool, recycled denim, soya fiber, cotton, hemp, and straw. The manufacturing process of recycled denim involves mixing of denim and cotton, which are later treated with fire resistant materials. Recycled denim is available in rolls, so as to facilitate easy installation. Among the other natural fibers used for roof insulation, the most expensive is sheep wool, which is also one of the best materials for insulation. Natural fibers have an additional advantage of being environment friendly.
In short, roof insulation comes in different types, made of different materials. It is better to go for materials with higher R-values for better efficiency. With a wide range of choices, it may get difficult to choose the right material. So consult experts and choose the one that is best suited for your roof.
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