Energy efficiency standards can be confusing. A good insulating structure has a low ‘U-value’.
Most manufacturers quote the U-value of their glazing units (defined as Ug) rather than the whole unit’s (Uw) energy efficiency. Besides the glazing however you have to consider the insulation of the window frame (defined as Uf) as well as thermal bridges at the glass edge and in the connecting area window to wall.
The Uw value refers to the whole window and is a true indication of the energy efficiency of a window or door unit – so this is what you should look for when comparing window & door products.
- Internorm window & door frames are densely packed with energy-efficient laminates so there are no air-filled spaces to lose heat through.
- The gap between panes is filled with argon and krypton gases. They have a much lower heat conductivity than air and thus also reduce the heat loss to the outside.
- This also means much larger windows and doors can be produced without compromising the energy efficiency of the whole unit.
ALL GOOD THINGS COME IN THREES
The fact that around 30% of the heat of a house can be lost via the windows is the reason for the increasing demand for high thermal insulation windows. However, it is not generally the glass that creates the thermal insulation properties.
INSULATING GAP BETWEEN PANES
With Internorm windows & doors, heating costs are saved through precious metal coatings that are applied in a wafer-thin layer to the surface of the glass and noble gases in the gaps between the inner and outer panes. The noble gases used are argon and krypton. They have a much lower heat conductivity than air and thus also reduce the heat loss to the outside.
The differences in the thermal insulation value Ug result from different coating structures and noble gases. Furthermore, the thermal insulation values are better with triple glazing than with double glazing.
TRIPLE-PANE HEAT PROTECTION GLAZING – bigger windows – no loss of heat
Compared to double glazing, the high insulation properties of the Internorm window systems with triple heat protection glazing allow an increase in glass area of up to 40% without any effect on the heating costs.
The use of this type of insulating glass significantly improves the energy balance and thus keeps the heating costs low. Furthermore, the special SOLAR+ coating allows solar energy gains and therefore additional heating free of charge.
Conversion case study:
Internorm windows used in former school conversion: St. Finian’s Schoolhouse, Kilquiggan, Co. Wicklow
Calculating the true U-value of a window
According to the European standard DIN EN ISO 10077-1, the insulation values of a window are calculated by splitting it into three zones: frame, glazing and glass composite edge. The components for the calculation are named accordingly: Uf (f for frame), Ug (g for glazing) and ψ (psi = glass composite edge). The values Uf and Ug are factored into the calculation with their respective area. By contrast, the glass edge psi is considered according to its length. From these components, the total thermal insulation value Uw (w for window) is calculated according to the following formula:
Uw = (Af • Uf + Ag • Ug + lg • ψg) / Aw (W/m²K) *see note
Uw: U-value of the window [m²]
Aw: area of the entire window, including the frame
Ag: visible glazing area [m²]
Ug: uninterrupted glass U-value [W/m²K]
Af: frame area [m²]
Uf: U-value of the frame [W/m²K]
lg: circumference of the glazing (length of the glass composite edge
ψg (psi): thermal bridge loss coefficient of the glass edge in W/mK
* Important note: The Uw value therefore refers to the whole window and is a true indication of the energy efficiency of a window or door unit – so this is what you should look for when comparing products.
TIP: Don’t just compare Ug values which are only for the glass component and are therefore misleading. A typical Internorm window unit has a thermal efficiency rating of (whole unit) Uw to 0,62 W/m²K (model HF 310) which is of Passive House standard.
How Internorm windows can help heat your home (and lower your carbon footprint).
HARNESSING SUNLIGHT & SOLAR ENERGY
From a physical perspective, wave radiation penetrates into the inside of a building through the window — visibly in the form of light waves and invisibly as energy and heat. The radiation transmission is measured as the luminous transmittance τv and the total energy transmission g-value. In addition to the U-value (thermal transmission coefficient), the latter in particular influences the energy assessment of the window. If the U-value and g-value are in the correct proportion, the window can even pay into the energy account, and for passive houses, for example, is an important component in the energy and heating concept.
Internorm SOLAR+ Glazing
The glazing can be used to control the insulating properties of the window and the quality of the relationship between the inside and outside. Internorm achieves the best insulating values with triple glazing as standard. But the window can do more: Thanks to the SOLAR+ coating it supplies heat.
The SOLAR+ triple insulating glass has an extremely high thermal insulation. It also has a total energy transmission value (g-value) that can otherwise only be achieved at this level with double glazing. Due to this special relationship between thermal insulation (U-value) and energy transmission (g-value), these glasses are perfectly suited for solar construction. In winter in particular, it utilises the weak solar irradiation optimally and keeps the heat gained in the building. The high g-value allows the gain in passive solar energy to be optimised even if the construction site is not optimal or the glazing is not precisely south-facing.
The SOLAR+ triple glazing has an energy transmission that is 20% higher than standard triple glazing. This also increases the solar energy gain by 20%. Free additional heating thanks to the glazing!
THE BENEFIT FOR CLIMATE PROTECTION
Efficient energy usage is one of the most important measures against climate change. Thanks to the energy-saving triple-pane technology and the innovative special SOLAR+ coating, climate protection windows from Internorm achieve optimal solar gains and guarantee maximum thermal insulation. This reduces the emissions of CO2 and SO2.
MORE LIGHT, MORE BRILLIANCE: SOLAR+
The high light transmission produces a more welcoming brightness inside: an important advantage, particularly in the dark winter months.