Yes — it gets hot. Anyone who has sat under a clear polycarbonate roof on a Gauteng summer afternoon knows exactly what this feels like. The light comes through beautifully, but so does the heat. Within an hour, the space underneath feels more like a greenhouse than a covered outdoor area.
The honest answer to whether polycarbonate roofing gets hot is: it depends. Not on some vague collection of factors — on three specific things that are all decisions made before the sheet is ordered. The sheet type, the colour, and the ventilation of the space below. Get these right and a polycarbonate roof is comfortable year-round in South Africa's climate. Get them wrong and you create a space that is genuinely unusable for three months of every year.
At Allrich Trading, we supply polycarbonate sheets across Johannesburg, Cape Town, and Durban for roofing, cladding, and glazing applications across South Africa. Here is what actually determines how hot it gets under a polycarbonate roof — and what to specify before you order.
Why Polycarbonate Roofs Get Hot
Polycarbonate is a thermoplastic material — it transmits light exceptionally well, which is why it is used for roofing applications in the first place. The same properties that make it optically clear also allow solar energy to pass through the sheet and into the space below.
Standard clear polycarbonate transmits approximately 88% of visible light. It also transmits a significant portion of the solar energy spectrum — including the infrared radiation that creates heat. This solar energy enters the space, warms the surfaces below, and is then partially trapped — unable to escape as efficiently as it entered. The result is heat accumulation that, in South Africa's climate, can be significant.
This is not a flaw in the material. It is a physics reality that applies to any transparent or translucent roofing material. Glass does the same thing — which is why greenhouses work. The question is not whether polycarbonate transmits heat — it does — but how much, and what can be done to reduce it.
The Three Factors That Determine How Hot It Gets
1. Sheet Type — Solid vs Multiwall vs Corrugated
Not all polycarbonate sheets perform the same way thermally. The construction of the sheet itself significantly affects how much heat builds up in the space below.
Solid polycarbonate sheets — a single solid layer of polycarbonate — offer minimal thermal insulation. They transmit light and heat efficiently in both directions. Under South African summer conditions, a solid clear polycarbonate roof produces the most heat accumulation of any polycarbonate sheet type. They are the right choice for applications where maximum light transmission matters more than thermal comfort — skylights in cooler spaces, agricultural covers, and applications with excellent ventilation.
Multiwall polycarbonate sheets — twin wall, triple wall, and multi-wall hollow construction — perform significantly better thermally than solid sheets. The hollow channels within the sheet create air gaps that act as insulation layers, slowing the transfer of heat from the outer surface to the inner surface. A twin wall polycarbonate sheet reduces heat transmission compared to solid sheet of equivalent thickness. Triple wall and multi-wall grades reduce it further.
For covered outdoor areas in South Africa — patios, carports, pergolas, and entertainment areas — multiwall polycarbonate is the correct specification if thermal comfort matters. The light transmission is slightly lower than solid sheet, but the reduction in heat build-up is significant and immediately noticeable.
Corrugated polycarbonate sheets — the familiar wavy profile used extensively in South African roofing — perform similarly to solid flat sheets in terms of heat transmission. The profile adds structural strength without adding thermal insulation. Standard corrugated clear polycarbonate produces similar heat levels to solid sheet under the same conditions.
2. Colour and Tint — The Single Biggest Variable
This is the factor most buyers underestimate. The colour of the polycarbonate sheet has a larger effect on heat build-up than almost any other variable — and it is an entirely free choice made at the time of ordering.
Clear polycarbonate transmits the most light and the most heat. Maximum brightness, maximum heat accumulation. Best suited to applications where light is the priority and either heat is not a concern or ventilation is excellent.
Bronze and grey tinted polycarbonate reduces solar heat gain significantly compared to clear. The tint absorbs a portion of the solar energy before it can pass through the sheet — reducing the heat that enters the space below. In South Africa's summer climate, bronze or grey tinted multiwall polycarbonate produces a noticeably more comfortable space than clear sheet under the same conditions.
Opal and diffused white polycarbonate scatters light rather than transmitting it directly. It reduces glare and softens the light quality in the space below — and it also reduces heat transmission compared to clear sheet. Opal polycarbonate is widely used in South Africa for covered outdoor areas where a softer, more diffused light quality is preferred.
Green and blue tinted polycarbonate — available in some grades — provides similar solar heat reduction to bronze and grey tints while producing a distinctively coloured light in the space below.
The practical recommendation for most South African covered outdoor applications — where the goal is comfortable year-round use — is bronze or grey tinted twin wall polycarbonate. This combination reduces heat build-up significantly compared to clear solid sheet while maintaining good light transmission.
3. Ventilation — The Factor Nobody Mentions Until It Is Too Late
A polycarbonate roof over a fully enclosed space will always be hotter than the same roof over a well-ventilated space. This sounds obvious but it is frequently overlooked at the design stage.
Hot air rises. In a covered outdoor area — a patio or entertainment space — if there is no mechanism for hot air to escape from the top of the space, it accumulates. The temperature under the roof climbs steadily throughout the day as solar energy enters and cannot leave.
Simple ridge ventilation — a gap at the highest point of the roof structure — allows hot air to escape continuously as it rises, replacing it with cooler air from the sides of the space. This alone makes a significant difference to comfort under a polycarbonate roof in South Africa's summer conditions.
For enclosed spaces where ridge ventilation is not practical — insulated ceiling panels below the polycarbonate roof, reflective foil insulation, or mechanical ventilation all provide effective solutions.
South Africa's Climate Creates Specific Challenges
South Africa's climate varies significantly by region — and the challenge a polycarbonate roof faces in Johannesburg is different from the one it faces in Cape Town or Durban.
Gauteng — the highveld climate creates extreme summer heat and intense UV radiation. The combination of high temperatures and strong direct sun makes sheet type and colour selection particularly important. For Gauteng patios and entertainment areas, tinted multiwall polycarbonate with good ridge ventilation is the minimum specification for comfort in summer.
Cape Town and the Western Cape — the Mediterranean climate means hot, dry summers and wet winters. UV levels are high in summer. Tinted sheet reduces summer heat while maintaining light in the wetter winter months. Multiwall construction provides additional insulation against winter cold — a benefit that solid sheet does not offer.
KwaZulu-Natal — Durban's subtropical coastal climate adds humidity to the heat equation. Under a polycarbonate roof in Durban's summer, the combination of heat and humidity creates particularly uncomfortable conditions if ventilation is poor. Tinted multiwall sheet with good ventilation is essential for year-round comfort in KwaZulu-Natal's coastal environment.
What to Specify for Comfortable Year-Round Use
For most covered outdoor applications in South Africa — patios, carports, entertainment areas, pool covers, and garden rooms — the specification that produces the most comfortable year-round result is:
Sheet type: Twin wall or triple wall polycarbonate — not solid sheet Colour: Bronze or grey tint — not clear Ventilation: Ridge ventilation or open sides — not fully enclosed
This combination reduces solar heat gain, provides thermal insulation in both directions, maintains comfortable light levels, and produces a space that is usable in South Africa's summer heat rather than one that gets abandoned from November to February.
Allrich Trading supplies polycarbonate sheets across Johannesburg, Cape Town, and Durban — in solid, twin wall, and multiwall grades, in clear, bronze, grey, and opal tints, for roofing, cladding, and glazing applications across South Africa.
Frequently asked questions
Here are some common questions about our company.
Yes — polycarbonate transmits solar energy, which creates heat accumulation in the space below. How hot depends on the sheet type, tint colour, and ventilation. Tinted multiwall polycarbonate with good ventilation produces significantly more comfortable conditions than clear solid sheet under South Africa's summer sun.
Bronze and grey tinted polycarbonate sheets reduce solar heat gain more effectively than clear sheet. They absorb a portion of solar energy before it passes through — producing cooler conditions in the space below while maintaining good light transmission.
Yes. Twin wall and multiwall polycarbonate sheets have hollow air channels that act as insulation layers — slowing heat transfer from the outer surface to the inner surface. This produces noticeably cooler conditions compared to solid sheet of equivalent thickness under the same South African climate conditions.
Choose tinted multiwall polycarbonate sheet rather than clear solid sheet. Ensure good ventilation — ridge ventilation at the highest point of the roof structure allows hot air to escape continuously. For enclosed spaces, consider reflective foil insulation or mechanical ventilation in addition to the correct sheet specification.