CPVC roofing tile

CPVC and Roofing - Construction's Newest Partner

Posted by TempRite® Engineered Materials EMEA Team on 07/21/2021

CPVC and Roofing: Construction's Newest Partner

TempRite® Engineered Materials specialises in compounds using CPVC (Chlorinated Polyvinyl Chloride) for the construction and roofing industries, among many more. CPVC is able to perform in heavy duty applications such as this thanks to its inherent resistance to threatening outdoor elements such as UV radiation and rising temperatures.

CPVC as a compound for roofing also benefits from superior dimensional stability, reducing the threat of long-term damage through thermal deformation. In addition, its ability to form panels with superior fire resistance enables structures to achieve high fire safety ratings, a common requirement in many countries, particularly those with hot climates or those that rely heavily on solar panel technology.

What to Consider When Specifying Roofing Material

Climate Change - Global temperature increases threaten a structure's integrity, particularly when manufacturers are used to delivering materials with particular standard operating temperatures.

Heat Resistance (HDT) - The Heat Deflection Temperature (or Heat Distortion Temperature) is the temperature at which an outdoor profile distorts or deforms under pressure. Not only is the product weakened, but it can also become physically deformed, i.e warping.

Deformation under Load - A material’s flexural modulus is the ratio of external load to material deformation. The lower the modulus, the more flexural deformation occurs at a given load. As temperature increases, modulus declines, leading to more deformation. TempRite CPVC maintains a higher modulus over a greater range of temperature.

Chart Showing Head Buildup Performance

Performance of TempRite CPVC in exterior cladding during temperature buildup,

compared to standard PVC

Dimensional Stability – TempRite CPVC has a coefficient of thermal expansion only about 65% that of PVC. This allows for better dimensional stability of parts as the temperature increases.

Fire Safety Rating - Especially important in solar panelling, a high fire safety rating of the roofing adds a layer of safety to structures, particularly as defective solar panels can ignite. Furthermore, in emergency situations, after power is cut from the home, solar panels can continue to generate power, even when a domestic fire has broken out.


It is always necessary to ensure compatibility of roofing panels with ancillary materials to avoid affecting the performance of the material.

UV Degradation - Arguably the most common threat to outdoor profiles UV can penetrate roofing materials, creating free radicals that degrade the roofing and reduce its effectiveness in protecting the structure below. CPVC is highly UV resistant, making it a natural choice for exterior applications.

How TempRite® CPVC Achieves Heat Resistance

Heat resistance is one of the principle requirements for a lasting outdoor roofing system and is one of TempRite CPVC’s core strengths.

CPVC vs PVC Molecules 
During the PVC chlorination to create CPVC, chlorine atoms occupy a large surface area of the polymer’s carbon chain. This stiffens the chain, giving the material a higher softening temperature.

Adding strength and stability at this early stage enables future compounds to benefit from superior heat resistance, even when combined with other materials and additives.

Achieving UV Resistance with TempRite CPVC

Much like heat resistance, CPVC’s UV resistance is a fundamental part of the compound’s properties. CPVC is formed by free radical chlorination; UV is used to activate the chlorine atoms, which subsequently attach to the PVC polymer chain. The chlorine atoms protect the polymer backbone and help prevent chain scission and polymer degradation.

UV and heat resistance are therefore fundamental to CPVC’s strength. In addition to this, titanium dioxide, a common additive in CPVC helps to defend the material UV penetration.

Rooftop Safety with CPVC

Safety considerations must be taken into account when designing rigid outdoor panelling for roofing, particularly when installed in conjunction with solar panelling.

CPVC achieves a high standard of fire protection because of its inability to sustain combustion under normal atmospheric conditions. It has a Limiting Oxygen Index (LOI) of 60, meaning there would have to be 60% oxygen in the air for CPVC to sustain combustion, where there is typically only 21%.

In comparison to rival polymers, CPVC has a much higher Flash Ignition Temperature (482°C/900°F) compared to Rigid PVC (399°C/750°F) and Polyethylene (343°C/650°F.) The Flash Ignition temperature is the temperature when there are enough free radicals in the atmosphere reacting with volatiles from the polymer, i.e the moment a material catches fire.

Should a malfunctioning solar panel ignite when installed on a roofing panel created with TempRite CPVC (such as PlastBlend’s Roofclix,) a barrier is formed. Rapid crosslinking from within the polymer forms a barrier, visible as a layer of char, preserving the layer of CPVC below.

It is this reaction, along with its reduced smoke propagation that allows roofing materials with CPVC to achieve exceptionally high fire ratings. For example, The RoofClix panelling system made in conjunction with TempRite CPVC has received the Broof (T1) classification in accordance with EN13501–5: 2016, a requirement in the roofing industry.

Solar panelling system installed on rooftop mounted with RoofClix panels

Solar panelling system installed on rooftop mounted with RoofClix panels

Creating Compounds for Roofing With CPVC

During the manufacturing process, CPVC allows for flexible augmentation of key characteristics that offer extra advantages to roofing. For example, heat stabilizers, UV stabilizers, impact modifiers, processing aids, lubricants and pigments.

It’s important to note that additive stabilizers may also have an effect on CPVC’s inherent heat and UV resistance, so a balance must be made between the desired effect and the fundamental advantages of the polymer.

Maintaining Strength With Design

As is often the case with plastic fencing and siding, roofing is also typically limited in terms of design and finish. This is because darker colours heat up more in direct sunlight, getting the material closer to or even beyond its Heat Distortion Temperature, affecting its performance and permanently warping its appearance through thermal expansion.

Radiant Heating
Radiant heating of various colours in direct sunlight

TempRite CPVC is capable of maintaining its strength outdoors in hot climates, even when darker colours are adopted for a specific aesthetic. Its high heat distortion temperature allows it to stand up to radiant heating, even when made into dark colors. The maximum radiant heating temperature of various colours shown here illustrates the palette of colours available to product designers who wish to expand their portfolio, even into darker shades and black panelling; a popular choice in modern designs.

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