Low power consumption


To analyze an investment opportunity with PVC insulated glass, we offer a study on the amount of heat saved, in comparison to classic wooden carpentry, following the assumptions: gas heating is considered, kL = 5.8 W/m2·ºK (in tables), window surface = 1m2 (conventional).

It is noted that other advantages of the carpentry (sound insulation, long life, easy maintenance, pleasant looks, ease of use) can not be quantified in these calculations.

Also there were not calculated the energy savings throughout the summer, when air conditioning in used for cooling the spaces (this consumption varies from 1 to 2.6 depending on the orientation and aim of the room).


Amount of energy saved when using REHAU PVC carpentry with insulating, double-glazed glass:


                                                  Δk · AF · Gt · 24

     ΔE = ---------------------------

                                        Hn · η


Δk = kL – kPVC = 5,8 W/m2·ºK – 1,4 W/m2·ºK = 4,4 W/m2·ºK;

kL – thermal coefficient of wood carpentry;

kPVC – thermal coefficient of PVC carpentry (kprofile REHAU =1,4 W/m2·ºK);

AF = 1m2 - window area (by convention)

GT = 4000 K·d - coefficient (in tables) of the number of cold days per year;

Hn = 8,82 kWh - coefficient of calories for natural gases

η = 0,75 - efficiency of modern thermal power station (yield high performance)

          Results  ΔE = 63,85 m3/an · m2

Approx. gas price = 0,215 EURO/m3

63, 85 m3 · 0,215 = 13,73 EURO/an·m2  SAVINGS!!!

If using a good quality insulating glass (Low E), the heat transfer coefficient of window kPVC decreases to 1,4 W/m2·ºK, and results:


Δk = 5,8 W/m2·ºK – 1,4 W/m2·ºK = 4,4 W/m2·ºK

Therefore ΔE = 63,85 m3/an · m2   

and the savings achieved are 13.73 Euro / year · m2 of surface for double-glazed windows!

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Tel: +40-754-097.712

e-mail: dorin@fensterdesign.eu