What is heat mirror

Heat Mirror is a film suspended inside double insulating glass. It is a three layer system with two independent air spaces, but has the advantage of weighing the same as a double glazing unit.

Diagram
The film is transparent to visible light, and at the same time it reflects remote infra-red radiation and harmful Ultra Violent radiation. Put simply, Heat Mirror reflects radiation back to the source; towards the outside in the summer, when you want the room to stay cool, and towards the inside in winter when you want the room to remain warm.

How does Heat Mirror compare with other types of insulated glazing?
The table below shows the benefits of Heat Mirror over standard glazing systems, allowing glazing units to be thinner, lighter and more efficient than standard systems.

		Thickness mm	Weight Kg/m²	U value Wm^-2K^-1
Double Glass	Float 4mm-16Air-Float 4mm	24.5	20	2.8
	LowE1.1 4mm-16Ar-Float 4mm	24.5	20	1.14
Heat Mirror	LowE1.1 4mm-12Ar-TC88-12Ar-Float 4mm	32.5	20	0.78
	LowE1.1 4mm-10Kr-TC88-10Kr-Float 4mm	28.5	20	0.62
	LowE1.1 4mm-12Ar-SC75-12Ar-Float 4mm	32.5	20	0.75
	LowE1.1 4mm-10Kr-SC75-10Kr-Float 4mm	28.5	20	0.58
Triple Glass	LowE1.1 4mm-10Ar-Float 4mm-10Ar-Float 4mm	32.5	30	0.82

Key:
LowE Low energy coated glass 4mm thick
Float 4mm clear float glass thickness 4mm
10Ar 10mm gap Argon filled
10Kr 10mm gap Krypton filled
SC75 TC88 Heat Mirror films

For an even more efficient glazing unit a double Heat Mirror unit is available which has a unbelievably low heat co-efficient U=0.4 Wm-2K-1, with a thickness of around 40mm and the weight of a standard glazing unit.

Types of Heat Mirror TM Films Used

Heat Mirror TC 88
high insulation (coating on both sides of film)
1. heat transfer coefficient U=1.20 Wm-2K-1 compared to U=1.48 Wm-2K-1 for HM 88 (valid for clear glass, 2 x 1/8 inches (3.175 mm), air filling and total insulating glass thickness of 1 (25.4)
2. excellent transparency lower reflectance than HM 88
3. high visible light transmittance
4. colour neutral (colourless) film
Examples:
Residential buildings in particular windows with a north or east orientation
Commercial buildings any projects needing improved insulation of windows and minimum reflectance such as: storefronts, restaurants, airports, schools, hospitals, museums, renovations of historic buildings.

Heat Mirror SC 75
1. excellent reduction of IR transmittance with minimum reflectance and high light transmittance
2. less reflective than HM 66 with similar shading coefficient
Examples:
Residential buildings house fronts with an increased need for control of heat gain and good insulation windows with a south or west orientation
Commercial buildings all type of projects where increased reflectance is undesirable but low heat gain is necessary

Heat Mirror 66
1. strongly reduced heat gain, also with reduced light transmittance but sufficiently low reflectance
2. good insulating performance with low reflectance and reduced heat gain
Examples:
Residential buildings with a high degree of glazing and south and west oriented facades
All types of applications with need of low heat gain but minimum reflectance such as: schools, hospitals, museums, libraries, vertical portions of conservatories, smaller skylights

Heat Mirror 55, 44, 33
1. moderately to high reflective surfaces, moderate to low visible light transmittance
2. vertical and sloped glazing for commercial projects with maximum protection against heat gain where moderate to high protection against light transmittance is welcome
Examples:
Office and administrative building
Sloped glazing needing good visible light transmittance (roofs, conservatories)
Skylights, atriums, conservatories

Did you know that tilting a glazing unit dramatically affects its insulating efficiency?
Installing a glazing unit in a horizontal position compared to a vertical position reduces its insulating performance by 33% for Argon filled and by 29% for Krypton filled units. Heat Mirror, by comparison only suffers from a 7-10% decrease in performance. This reduction in efficiency is due to the mechanism of heat exchange between air and gas flows.

A final interesting fact
The annual energy lost through a window with a U value 1.2 Wm-2K-1 is 134KWh compared with only 64KWh for a Heat Mirror window with a U value of 0.55 Wm-2K-1.This represents an energy saving of more than half!