Three Common Types of Roof Insulation Materials


Heat rises into the peak of your roof. Roof insulation traps heat, saving you energy costs. Whether you have baseboard heaters, a wood stove, or a propane heating system, heating your home is costly during the chilly winter months. If your roof is not properly insulated, the heat will escape. You will constantly be turning up the thermostat, burning more energy, and writing large cheques to your utility company.

There are different methods to insulate your roof including polyisocyanurate, extruded polystyrene (XPS), and expanded polystyrene (EPS). The best type of insulation for your home is dependent on where your home is physically located. Climate zones in Australia, for example, are zoned numbers one through eight.

What Are R Zones?

Zone one is in northern Australia. As you near the Earth’s equator, the winters are warmer and humidity is increased in the summer. Middle Australia is zone four. Zone four has a hot dry summer and a cool winter. Finally, southern Australia reaches zones seven and eight, with cool and alpine temperatures.

Zones are used to determine the best roofing insulation choices all around the world. For example, the United States zones are reversed. As you move south, the zones become hotter.


Polyisocyanurate is the most used roofing insulation. Polyisocyanurate is cost-efficient and its R value starts at R-8, meaning that it insulates your roof in even the coldest temperatures. It is a cell foam that is created by heating synthetic materials and chemicals. As it cools, it forms into rigid panels. Over time, the R value degrades down to R-5.5. To maintain the integrity of your insulated roof (known as หลังคาติดฉนวนกันความร้อน in Thai), you should have a professional check your insulation annually.

Extruded Polystyrene (XPS)

XPS is a mid-grade material. It is slightly more expensive than expanded polystyrene (EPS) and less expensive than polyisocyanurate. XPS is designed for an R value of R-5 and characterised by its blue, green, and pink colours. It is a blended polystyrene polymer that is heated through a process called extrusion. As with polyisocyanurate, XPS also degrades over time.

Expanded Polystyrene (EPS)

EPS is used in different areas of your home including your roof, walls, and floors. EPS does not retain water over time and can be used in contact with the ground. It is the least expensive type of insulation because it has a small R value of 3.6 to 4.2.

It is a polystyrene polymer with a foaming agent mix. Insulators heat the material to expand and mould it to a specific form. Once it cools, it forms a closed-cell insulation material. EPS is used for common items such as coffee cups.

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