WeatherTech LoE Glass™ is specially coated to admit light but reflect heat, keeping it outside in the summer and holding it inside in the winter. Its higher R (thermal resistance) value means greater insulating performance than ordinary thermal glass. Ordinary thermal glass has an R (Thermal Resist) factor of 2.1. A thermal unit with WeatherTech LoE Glass™ (withArgon) has an R factor of 4.2. Plus, WeatherTech LoE Glass™ glass reduces the amount of UV light by up to 1/3 of other coatings, protecting furniture and floorings.