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Basic Performance Factors of Insulating Double Glass Windows - Garoufalis Glass™
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Basic Performance Factors of Insulating Double Glass Windows - Garoufalis Glass™
Tuesday 18 Feb 2020
In the following article of our Glass Expert, we will clarify the most basic concepts that we must check before deciding which energy double glass we will choose to place in our frames, in order to achieve the maximum Thermal Insulation & Solar Control of our building.

U-VALUE & G-VALUE 

 

It can normally be reckoned that around 35% of the heat in a house will escape through the windows. Just how great actual heat losses are depends among other things on the window model, whether there are one, two or three panes in the cassette, on the type of glass used and the nature of the gas between the panes. At the same time the incoming solar heat often contributes to the high cost of cooling a property during the summer months. The balance between warm and cold, summer and winter is helped by having energy-efficient windows.

 

 

What is g-value?

The g-value is a measure of how much solar heat (infrared radiation) is allowed in through a particular part of a building. A low g-value indicates that a window lets through a low percentage of the solar heat. The g-value can be improved by having the outer glass pane coated with an IR-reflecting surface which reflects some of the radiant heat. The aim of this is partly to reduce the costs of cooling the property, and partly to improve the indoor environment in properties without comfort cooling. Untreated insulating glass has a g-value of approximately 1.3.

 

 

What is U-value?

The U-value is a measure of how much heat escapes via the windows, walls and roof for example. The U-value is often measured for the whole window structure with the combination of glass, frame and sash. The lower the U-value, the better the insulating capacity of the window. The U-value can be improved by the glass panes being coated with a metal-based surface which reflects long-wave radiation back into the room. A U-value of 1.0 means a heat flow of 1 Watt/square metre surface area for every degree which separates the outdoor temperature and the indoor temperature (W/m² °C, previously termed the k-value). A new insulating glass pane has a U-value ranging from 2.7 down to 0.4.

 

What does the U-value mean in practice?

In an ordinary private house it is estimated that there are 30 m² of window glass. The property owner chooses between insulating glass with a U-value of 1.2 and a glass with a U-value of 1.6. What is the difference in the heating costs per annum?

In theory a difference in U-value of 0.1 units corresponds to c. 9 kWh/m2 glass per annum. The difference between 1.6 and 1.2 is 0.4 units.

Thus the saving is (difference in U-value) x (additional consumption) x (area of glass) = 4 x 9 kWh/m² x 30 m² = 1,080 kWh/annum. With an energy cost of 0.13 €/kWh the difference is 140 €/annum. 

A school with 300 m² glass consequently saves approximately 1.400 €/annum, based on a U-value of between 1.6 and 1.2 for the window glass.

 

What is the U-value of Garoufalis Glass™?

Garoufalis Glass Co. Insulate triple glazing has a U-value of 0.70 , Garoufalis Glass Co. Insulate double glazing has a U-value of 1.00


What is the TL (Transmittance Light) value?

The TL value is a measure of the percentage of natural light that eventually passes through the energy glazing relative to the fact that there was no material interference such as if the window was open. The higher the TL, the more transparent the energy glass we have chosen. The ideal TL to ensure maximum thermal insulation & solar control & the four seasons, ranges up to 60% through a certified Energy Double Glass product-Garoufalis Glass ™ that combines 4 seasons soft glass energy glass & Argon gas within the gap.


In all the above, choosing windows for our building, we always include the quality of construction of an Energy Double Glass as well as all the Authentic Certifications (CE) for its proper gluing. The company Garoufalis Glass, officially & responsibly declares that it is the only company in Achaia, which: 



 

  • Only "Cold" Thio Adhesives are used for the second and final stage of sealing
  • The glass panes are cleaned exclusively by the automatic washing machine of our company
  • The first sealing step, Butyl, is always applied.
  • The introduction of a special noble Argon gas, in the gap of the double glazing, is done exclusively through an automatic machine
  • The energy-coated side of the glass is always placed inside the double glazing and on the outside of the double glazing system.

The climatic conditions of Greece prohibit the use of hot thiol glue, since there is an immediate and extensive risk of peeling of the double glazing and their destruction due to high temperatures during the summer months. For the issue of the correct construction of double glazing, see the corresponding article of our Glass Expert.

Article:

Garoufalis P. Efthimis

* Economist, BSc Economics University of Patras

* Specialization in Energy Double Glazing Topics

* Specialization in performance studies of Thermal Insulation / Sound Reduction through Glazing.

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