Saving Energy

Greece is one of the countries with the highest energy consumption in relation to the volume and energy consumption of buildings reaching 35% of total energy consumption in the country..

Much of this consumption is in the way of construction of buildings. Over 80% of the existing buildings are un-insulated and are old and single glazed windows, so there are high heat losses in winter and overheating in summer. The implication of this over-consumption is not economic  and environmental. A particular concern are emissions of carbon dioxide (and other gases) from burning fossil fuels for heating and cooling in the building sector, which contribute to climate change seen by the intensity of greenhouse emissions in recent years.

The windows of the buildings contribute a large share in energy consumption for heating and cooling of space, because the windows transfer large amounts of energy. In winter, heat is lost from the inside out, while in summer heat from entering the hot outside. This process can be minimized by using properly constructed, energy efficient windows. A window to be energy efficient should be made of thermal insulation systems have double seals around the joints, perimeter sealing mechanism and double glazing or single glazing Energy-N with a special coating and gas inside.

An important indicator of the efficiency of a window (both of the glass and the frame) is thermal permeability, which is given by the manufacturers with the value (K or U) and expressed in W/m2 oC.Apart from thermal permeability and other properties affect the overall energy performance of a window or glass (air permeability, light transmission, emission factor, etc.), whereby the thermal and visual comfort that makes the window and the consequent energy saving.

Using energy efficient windows is mandatory for new buildings, Regulation Insulation in force since 1979. There is a range of types of glass and windows that can select one of the buildings, depending on use and size of the building and the value of each system. In each case the buyer should ask the manufacturer to inform him at least for thermal permeability the window will move.

Where the use of energy efficient windows is particularly useful is in old buildings, constructed before 1979, which generally have single-glazed windows and are generally high energy consumption. The Replacement of old windows with new energy efficient double glazed windows, although it has a cost, can be reversed by a large proportion of the poor efficiency of the building, with multiple benefits, other direct and other longer term. Some of the advantages of using energy efficient windows are:

• Saving energy: Avoiding leaks heat in winter and cool in summer, we consume less energy.
• Economy: Reducing energy consumption for heating and cooling limit costs for oil, electricity, gas or other fuels.
• Improved comfort: it better internal climate conditions, fewer movements near the window, the same room temperature and less outside noise.
• Environmental benefits: reducing CO2 emissions restrict emissionsat the local, national and global level.
• Other benefits: avoid condensation on the glass, improves visibilityand quality of windows

The comparison is made between aluminium, wood and synthetic frames with conventional single glazing with double glazing and insulating glass with low emission.

The formula for calculating the heat loss is:
Q=A* ΚF * Differential Temperature
Where:

• Α is the frame surface
• ΚF Thermo permeability coefficient frame
• Differential Temperature difference is the internal temperature (air-conditioned) and outdoor (N. Greece, winter)

Measurement Datas

• External Temperature: 4 oC
• Internal Temperature: 23 oC

So Differential Temperature=23-4=19 oC

A = 80 square meters apartment with six frames total surface 14m2

U-KF window depending on the type of window and glazing type are:

• Old fashioned wooden window frames with single glazing 4mm: Κholz 4,7 W/ m2 oC
• Without thermal break aluminum frames with double glazing Κalu 4,1 W/ m2 oC
• Thermal break aluminum frames anddouble glazing Κalutherm 2,8 W/ m2 oC
• PVC window frames with five compartments and double glazingsimple Κpvc 2,4 W/ m2 oC
• Thermal break aluminum frames with double Εnergy-N glazing simple Κalutherm-N 1,6 W/ m2 oC
• PVC window frames with five compartments and a double Εnergy-N glazing simple Κpvc-N 1,2 W/ m2 oC

Q=Heat Loss


• Wooden Frames Aluminium Aluminium without Thermal ThermalPVC five-chamber PVC Aluminium Thermal five wards
• Glazing 4mm 4-12-4mm 4-12-4mm 4-12-4mm Energy N + argon 5-12-4mm Energy N +argon 5-12-4mm
• A 14m2 14m2 14m2 14m2 14m2 14m2
• ΚF 4,7 W/ m2 oC 4,1 W/ m2 oC 2,8 W/ m2 oC 2,4 W/ m2 oC 1,6 W/ m2 oC 1,2 W/ m2 oC
• Differential Temperature 19 oC 19 oC 19 oC 19 oC 19 oC 19 oC
• Q 1250 W/ m2 oC 1090 W/ m2 oC 745 W/ m2 oC 638 W/ m2 oC 425 W/ m2 oC 319 W/ m2 oC

So if we have wooden frames with single glazing and replace with:
• thermal break aluminum frames with double glazing 4-12-4mm toreduce heat loss is achieved : 1250-745=505 W/ m2 oC that is 40%.
• PVC window frames with five compartments and double glazing 4-12-4mm to reduce heat loss is achieved: 1250-638=452 W/ m2 oC that is 41%.
• aluminum frames with thermal break with adouble Εnergy-N υάλωση 5-12-4mm reduce heat loss is achieved: 1250-425=825 W/ m2 oC corresponding to 66%.
• PVC window frames with five compartments and a double Εnergy-N glazing 5-12-4mm η reduce heat loss is achieved: 1250-319=931 W/ m2 oC corresponding to 74%.
and if we have no thermal break aluminum frames with doubleglazing and replace them with:
• thermal break aluminum frames withdouble glazing 4-12-4mm reduce heat loss is achieved : 1090-745=345 W/ m2 oC corresponding to 32%.
• PVC window frames with five compartments and double glazing 4-12-4mm reduce heat loss is achieved : 1090-638=612 W/ m2 oC corresponding to 49%.
• aluminum frames with thermal break with adouble Εnergy-N glazing 5-12-4mm reduce heat loss is achieved:1090-425=665 W/ m2 oC corresponding to 61%.
• PVC window frames with five compartments and a double Εnergy-N glazing 5-12-4mm reduce heat loss is achieved: 1090-319=771 W/ m2 oC corresponding to 71%.