Your existing windows can be one of the most crucial sources of heat transfer in your home, letting in unwanted heat enter during summer and desirable warmth escape during winter.
Understanding U-values makes it easier to compare single glazing, conventional double glazing and vacuum insulated glazing.
U-Values measure the rate of convective heat loss in Winter or heat gain in Summer to help homeowners compare the thermal performance of single glazing against the various double glazing profiles in the market.
The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value.
The U-Value of glass and double glazing is determined by the formula W/m²K
W/m²K is the rate of heat flow (in Watts) through 1m² of glass surface area for every degree (K) difference in temperature between the inside and the outside of your home.
The basic calculation is:
Heat flow (W) = U-value (W/m²·K) × area (m²) × temperature difference (K)
For example, if the outside temperature is 5°C and the indoor temperature is 20°C, the difference is 15°C
The same difference applies on a hot day when the outside temperature is 35°C and the indoor temperature is 20°C.
VacGlaze™ comprises two panes of toughened safety glass separated by a vacuum insulated gap. The vacuum extracts almost all air from between the glass panes, reducing heat transfer through the glazing.
VacGlaze™ Vacuum Insulated Double Glazing has a U-Value of 0.7 (0.7 watts/m² K)
Exterior Glazing
Clear Toughened Safety Glass
Thermal Gap
0.2mm Vacuum Insulated Gap (Air Extracted)
Interior Glazing
Clear Toughened Safety Glass with Low-E
For comparison, standard 4 mm single glazing has a typical U-value of approximately 5.8 W/m²·K.
The following explanation provides the easiest way to interpret U-Values.
Glass with a U-Value of 0.7 will transfer heat at about 29% of the rate of glass with a U-Value of 2.4.
Glass with a U-Value of 0.7 will transfer heat at about 12% of the rate of glass with a U-Value of 5.8.
This highlights why lower U-Values are key for maintaining a more comfortable indoor environment.
Single Glazing with a U-Value of 5.8 will transfer 5.8 Watts of heat per m² of glass for
every degree of temperature difference between the outside and inside.
VacGlaze™ with a U-Value of 0.7 will transfer 0.7 Watts of heat per m² of double glazing for every degree of temperature difference between the outside and inside.
The temperature difference is 15 degrees where:
Winter: Outside temperature is 5°C and inside temperature is 20°C.
Summer: Outside temperature is 35°C and inside temperature is 20°C.
Single Glazing compared to VacGlaze™ Vacuum Insulated Double Glazing:
Standard single glazing: 5.8 Watts x 15 degrees = Heat loss of 87 Watts
VacGlaze™ double glazing: 0.7 Watts x 15 degrees = Heat loss of 10.5 Watts
Single glazed glass will transfer about 87 Watts of heat per m² glass while VacGlaze™ will only transfer 10.5 Watts of heat per m² where there is a temperature difference of 15 degrees in Summer or Winter.
This means that VacGlaze™ Vacuum Insulated Double Glazing will reduce heat transfer by approximmately 88% compared to standard single glazing.
Under these stated conditions, VacGlaze™ Vacuum Insulated Double Glazing reduces heat transfer by approximately 88% compared with standard single glaze.
Ultimately, the results will speak for themselves … helping reduce unwanted heat loss during winter while limiting unwanted heat entering your home during summer.
VacGlaze™ Vacuum Insulated Double Glazing is made to replace the current, inefficient single glass in your existing aluminium or timber frames and transform your windows & doors into an energy efficient system for lifelong comfort and energy efficiency savings.
Feel free to call 1300 766 743 to learn more about VacGlaze™ Double Glazing or to ask any questions about replacing the single glass in your existing windows and doors with double glazing.
Free — No Obligation
Request a FREE
Measure & Quote
Or call us directly
1300 766 743Mon–Fri 9am–5pm
