What do I have to consider to consider replacing the windows at home?
There are two different factors independent of each other to be taken into account to decide whether or not to replace the frames of the house.
The first factor is the consumption, the second is comfort.
if a wall very well may have made a transmittance of 0.15 W / mqK (watts per square meter per degree of difference between internal and external), a window frame varies between about 0.8 and 2.
A double glazing old instead has transmittance 2.7 and in the case of single glass climb to 5.4 approx.
We immediately recognize what the values of heat loss can be much higher than those that pass through walls. (5.4 vs. 0.15 = 36 times as much!)
Keep in mind that consumption is directly proportional to the transmittance of the elements that make up the envelope (and this independently of the building is good or bad block).
So if you have old windows is generally worthwhile to replace or change the glass.
The investment pays for itself?
It depends on which window you have and if there are incentives (eg, deductions 55% or 36%)
Example of calculation of the payback time of 1 square meter of window replacement:
1) How much power does a window in a year?
1 square meter x 5.4 W / mqK = 5.4 W / K
Degree days in my village: and: 2500GG
2500GG x 24 x 5.4 W / K = 324.000Wh / a = 324kWh / a
2) how to produce and what it costs me that I must replenish that energy lost?
Suppose heat boiler and with a system average efficient.
Cost of natural gas 1mc € 0.7 = 10kWh
Efficiency of the heating system: 78%
324kWh / y / x 0.78 € 0.07 / kWh = € 29.08 / a
Annual consumption per square meter of glass: 29 € approx.
Have you ever experienced the feeling of cold that you try stopping in front of a cold glass? The glass facades are still good as the cold element casing. But the glasses are needed to let in light and sunshine in the house and make it more comfortable and if the glass is good, you can also place them in front of the dining table without causing congestion guests.
In particular, high performance windows are unable to contain over 17 º C surface temperature of the glass and kept within 3 ° C
the temperature difference between glass and air inside does not engender disturbing air movements that accentuate the unease and feeling cold and usually must be compensated with classic radiators under the dock.
SO: install windows performance (Uw = 1.0 WMQ / K) improves the comfort of the rooms and allows a better and freer use of space.
PS: the central and southern Italy usually do not need triple glazing on the south side, because there is also associated with reduced dispersions lower solar gains.
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