What does "Energy Glass" and what difference have they, from the windows I have in my house? 

The term "Energy Glass" used in recent years as a free translation of the term "Energy efficient glass" to identify the class of glazing, which have characteristics that hinder the transfer of heat from one side to the other, thereby helping energy saving.
The glass they have revolutionized the technology of insulating materials because show surprisingly higher thermal performance than all hitherto known types of glass. 220% improvement in heat insulation than the common double glazing and 400% compared with ordinary (single) glass!
For two thousand years (from the production of raw translucent glass so far) man uses the "window" in the building openings (windows, etc.) to and daylight to enter inside and to protect their occupants from weather conditions ( wind, rain, heat, cold), dust, noise, etc. The basic principle remained the same despite the dramatic improvement in the quality of glass, particularly in the last 100 years. There are also few, even today, buildings (houses, shops, etc.), especially in small towns and villages that have their openings just single glazing.
Revolution in thermal insulation performance of the glass was the invention of the "double" glazing which began to spread in the early 70s. In Greece the effective widespread use beginning in the early 80s. We find so several buildings (mostly apartments) which then constructed to have "double glazing" ie two windows glued together circumferentially, with a gap therebetween so as to form a "balloon". The performance of the "double" those panes in terms thermal insulation, compared to the performance of previously placed side single glazing was improved by 200%.     
From about the same time, the glass production companies began to market low-emission glass (Low-emissivity or Low-E), with particularly high transfer inhibiting potential of heat from one side to the other through a microscopically finest coatings metals (silver oxide, etc.) which enapethetan the surface of the glazing. It was the one the generation Energy Glass or Glass Low-E.
Today most companies producing feature AssesSment Energy Glass 3 the generation with even more improved insulating capabilities (over 400% compared with ordinary single glazing and 200% compared with ordinary double glazing).
A similar type of glazing we have installed in our house, is the difference in the insulating ability of, compared to that of modern "Energy Glass" Low - E the 3rd rd generation.

What does the Energy Glazing four seasons? 

The "Energy Glass" have in principle the "capacity" to hinder the emission of heat from the warmer to the cooler side (hence called low-emissivity glass (Low-E). Our ability helps to "keep" heat our house in the winter and in the summer through the heat of the external environment outside, saving energy (for heating or air conditioning of the space, respectively).
This property of "Energy Glass' works with all weather conditions (sunny or cloudy), all times (day and night), all days of the year (winter - summer), if not exposed directly to sunlight.
From the moment that the glass sheets are exposed to solar radiation things change. Simple Energy Glass not designed to 'block' the entrance of solar light which penetrates a window when the "beats" the sun. The piece is then emitted solar energy penetrates the glass unhindered, enters our space is absorbed by objects and retransmitted them in the form of infrared radiation (ie heat). When this heat trying to escape would fall on to our energy glazing, which is an excellent insulator infrared.This has created an excellent conservatory which very soon will either bring us distress, or will force us to pay handsomely to the account of the air conditioner ... ...
So the glass manufacturing companies created a category Energy Glass with additional coatings, capable of controlling the entry of solar light in the building. These energy glasses, beyond their ability to impede the transfer of heat from the warmer to the colder side, and have the ability to prevent the access of direct sunlight to the interior of buildings and constitute the class of glass solar control ( Solar Control ) best known in the market as Glass Four Seasons in that work and in the summer when the hot sun "hits" windows.     
Clearly if the sun does not "see" the windows, either because they are Vorina, either because it's beneath porches, canopies, awnings, trees, etc., ordinary Energy Glass enough. The placement of Solar Control glass or four seasons, only makes sense as long as it is openings in which "falls" onto the sun passes through and heats the interior of buildings.
 Unlike the Nordic countries where the heat of solar radiation can be enjoyable or even slightly annoying, the southern countries suffer from it, especially during the summer months. Think about how difficult it is to klimatisoume a summer space when the sun enters from windows, doors and curtain walls.

Finally, because the energy glazing can be considered "green" product; :

First the glass is a fully recyclable material and is composed of 60% quartz sand, 18% by soda, 13% dolomite and small amounts of limestone, sulphurous salts and natural metal oxides, ALL natural and recyclable materials.
Moreover, we certainty but then we say that the glass is that the most powerful ally in the effort of carbon dioxide emission reduction  CO2  and one to produce 1 square meter once emitted 25kg while using the saved 91kg per year for life. !!

Why choose energy efficient windows
Putting energy glass offers the following advantages : 

• Multiply the insulation
• It improves comfort of space
• Disappear dew
• Reduces the necessary power equipment heating / cooling
• Is increased up to 200% the thermal insulation, compared with ordinary double glazing
• By saving energy (oil / current) reduction of emissions of greenhouse gases