Maximising Heat Retention with Low-E Roof Glazing
researching thermal efficiency for a year-round glass room
While solar-control glass is famous for keeping heat out, Low-Emissivity (Low-E) coatings are the unsung heroes of heat retention. These microscopic metallic layers are designed to reflect long-wave infrared energy—the kind of heat generated by your indoor heaters—back into the room. For anyone planning to use their glass room in the cooler months, understanding the 'U-value' benefits of Low-E glass is essential.
How Low-E technology works
Low-E glass has a transparent coating that allows short-wave solar radiation (light and some heat) to pass through, but reflects long-wave heat back to its source. In a glass room, this means the warmth from your infrared heaters stays inside for longer rather than escaping through the roof panes.
- Reduces the rate of heat loss
- Lowers the 'cold spot' feeling near glass
- Improves the energy efficiency of the space
The difference in U-values
The U-value measures how much heat is lost through a material. Standard single-pane toughened glass has a relatively high U-value. Adding a Low-E coating, especially when used in double-glazed units within a glass room, significantly lowers this value, making the environment much easier to keep warm.
Note that verandas (open-sided) benefit less from Low-E than enclosed glass rooms because air movement is the primary heat loss factor there.
Low-E vs Solar Control
It is common to confuse the two. Solar control stops heat from the sun entering; Low-E stops heat from your home leaving. For the best year-round performance, many specifications include both: a solar-control layer on the outer face and a Low-E layer on the inner face.
- Solar Control: Best for south-facing summer comfort
- Low-E: Best for evening and winter warmth
- Combined: The gold standard for glass rooms
Maintaining the coating
In modern glass manufacturing, the Low-E coating is usually 'hard-coat' or 'soft-coat' and is protected within the laminate or the internal face of a double-glazed unit. This means it cannot be scratched off during normal cleaning and will maintain its thermal performance for the life of the glass.
Deciding between the two: common questions
Is Low-E glass necessary for an open veranda?
Not usually. Because an open veranda has constant airflow, the thermal retention of the glass makes very little difference to the ambient temperature.
Does the coating make the glass look dark?
No, modern Low-E coatings are virtually invisible and do not noticeably affect the clarity or colour of the natural light entering the room.
Can I retro-fit a Low-E coating?
No, these are factory-applied during the glass making process and cannot be added to existing glass once it has been installed.
Which side of the glass is the coating on?
It is typically applied to the internal surface (the side facing into the room) to reflect heat back into the living space.
In short
Low-E coatings are essential for enclosed glass rooms, working to reflect heat back into the space and significantly improving thermal comfort during the winter months.
What to do next
Ask our specialists about the best glass specification for your year-round glass room.
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