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Thermal Render vs Standard Render: What's the Difference?

If you are replacing external render and have come across thermal or insulating render for the first time, this page gives you a straightforward, accurate comparison.

STANDARD RENDER

What Standard Render Does

Standard external render — sand and cement, monocouche, acrylic — performs two functions: it weatherproofs external walls and provides a decorative finish. What it does not do is insulate. Heat moves freely through standard render because sand, cement and polymer systems do not resist heat conduction to any meaningful degree.

  • Sand and cement — strong and durable but rigid, making it prone to cracking. Relatively impermeable — can trap moisture in older solid-wall buildings.
  • Monocouche — a through-coloured, pre-mixed system applied in a single coat. More flexible than sand/cement but still provides no insulation. Often mistakenly referred to as K-Render
  • Acrylic/Silicone render — flexible and crack-resistant. Highly impermeable — problematic on solid-wall properties where breathability matters.
THERMOSILICONE RENDER

What ThermoSilicone Does Differently

ThermoSilicone is Proofshield's complete external insulating render system. Its insulating performance comes from two sources:

  • ProofTherm base coat — uses expanded perlite (thermal conductivity 0.058 W/mK) instead of sand. Perlite's honeycomb microstructure of air bubbles creates an uninterrupted thermal barrier across the full wall face.
  • ThermoSilicone finish coat — silicone-based decorative coat containing ceramic microspheres that further disrupt the path of heat transfer through the wall.

The system is also vapour permeable — unlike acrylic render, it allows moisture to move through the wall, preventing the accumulation that causes damp in solid-wall buildings.

PERFORMANCE DATA

Measured R-Value Improvement

Standard external render systems have no measurable R-Value improvement over an unrendered wall. ThermoSilicone at the standard 20mm base coat depth increases the thermal resistance of a single-skin masonry wall by 310%.

PERFORMANCE DATA

Thermal Render vs Standard Render : Full Comparison

DOES THERMAL RENDER COST MORE?

The Price Question — Answered Honestly

No. Most of the cost of any job is actually the labour and ancillaries and things such as scaffolding. As the accredited installation partner for Proofshield in the South East, our material costs allow us to provide fully insulating render and plaster systems at the same price as regular systems.

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WHICH IS RIGHT FOR YOUR PROPERTY?

Choosing the Right System

ThermoSilicone is the right choice if:

  • Your property has solid walls — pre-1920s construction with no cavity
  • You want to reduce heat loss and heating bills
  • You have experienced condensation damp or mould and want to address the thermal cause
  • You want a 15-year manufacturer warranty rather than a standard builder's guarantee
  • You want a breathable system that will not trap moisture in the wall

Standard render may be sufficient if:

  • Your property has cavity walls with existing insulation and adequate thermal performance
  • The render is purely cosmetic and thermal improvement is not a priority
  • You are rendering a new-build extension where breathability and thermal performance are not concerns
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FAQ

Frequently Asked Questions

No. ThermoSilicone is priced at the same level as a standard render system. There is no cost premium for the thermal insulation performance

Perlite is a volcanic mineral. When expanded under heat, it develops a honeycomb microstructure of micro air-bubbles that gives it excellent thermal insulation properties. Its thermal conductivity is 0.058 W/mK. Used as the primary aggregate in ProofTherm base coat, it replaces sand and creates an effective thermal barrier in the wall.

At a standard 20mm base coat depth, ThermoSilicone increases the R-Value (thermal resistance) of a single-skin masonry wall from 0.18 to 0.738 m2K/W — an improvement of 310%. At 30mm the improvement is 406%, and at 50mm it is 597%. Source: CIBSE Guide A, Section 3.

ThermoSilicone is particularly effective on solid-wall properties where external walls have no existing insulation. It is suitable for most residential and commercial properties. We confirm suitability at the free survey.