ᐅ Why is shading especially important in newly constructed houses?
Created on: 29 Aug 2016 13:33
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Grym
It is often argued that shading is especially important in new builds to prevent overheating in summer. But why is that exactly?
The insulation in a new building works both ways. Whether it’s cold or heat, the house takes much longer to adopt the outside temperature compared to an older house with poorer insulation.
Now, regarding the windows themselves. Shouldn’t solar energy pass through a less effective double-glazed window faster than through a modern triple-glazed window?
Why do many say that shading is PARTICULARLY important in new builds during summer? I would rather think the opposite: a new build is better insulated against heat from outside. Triple-glazed windows with a low U-value keep heat out better than old double-glazed windows.
The insulation in a new building works both ways. Whether it’s cold or heat, the house takes much longer to adopt the outside temperature compared to an older house with poorer insulation.
Now, regarding the windows themselves. Shouldn’t solar energy pass through a less effective double-glazed window faster than through a modern triple-glazed window?
Why do many say that shading is PARTICULARLY important in new builds during summer? I would rather think the opposite: a new build is better insulated against heat from outside. Triple-glazed windows with a low U-value keep heat out better than old double-glazed windows.
Let’s revisit the topic of solar radiation. There is a value called the g-value. It is 0.8 for single-glazed windows, 0.63 for double-glazed windows, and 0.55 for triple-glazed windows. Triple glazing allows the least amount of solar radiation (both summer and winter) to enter, but the difference is quite small—about 12.7% less energy input from radiation.
(By the way, the g-value indicates the percentage of radiation that passes through the glass and enters the building.)
If you increase the window size by 100%, but triple glazing only reduces the energy input per area by 12.7%, it becomes clear why shading is more important in new buildings. Essentially, it’s just that there is more south- and west-facing window area.
So, should you simply cover all south and west windows completely with shutters and then enjoy the light from the east-facing windows, which still provide more light than old buildings with tiny windows?
(By the way, the g-value indicates the percentage of radiation that passes through the glass and enters the building.)
If you increase the window size by 100%, but triple glazing only reduces the energy input per area by 12.7%, it becomes clear why shading is more important in new buildings. Essentially, it’s just that there is more south- and west-facing window area.
So, should you simply cover all south and west windows completely with shutters and then enjoy the light from the east-facing windows, which still provide more light than old buildings with tiny windows?
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Bieber081530 Aug 2016 06:53Knallkörper schrieb:
No, the conductive one Both are correct if we consider the complete heat transfer from inside to outside (indoor air – boundary layer – wall – boundary layer – outdoor air).
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Peanuts7430 Aug 2016 07:02RobsonMKK schrieb:
Did you ventilate over the weekend? If there’s no wind and the temperature inside and outside is the same, then Sebastian is right... practice beats the textbookNo practice beats physics or the textbook, as long as it is applied correctly.
Another issue could be that heat is absorbed through the windows and stored in the walls, so it is not released as quickly during ventilation.
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Sebastian7930 Aug 2016 07:21That's exactly the problem – and also the practice.
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Peanuts7430 Aug 2016 07:32Sebastian79 schrieb:
That’s the problem – and the reality.Yes, but this can also be explained physically if you consider ALL factors.
It’s not that the temperature should physically only be 24 degrees Celsius (75°F), but then, magically, in practice it turns out to be 27 degrees Celsius (81°F). If that happens, simply not everything has been taken into account.
Whether someone is willing to do the work or if anyone can be found who calculates every single detail is another matter.
This is where practitioners rightly come in, who from experience can estimate what exactly needs to be done...
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Knallkörper30 Aug 2016 07:40Peanuts74 schrieb:
No practical experience can override physics or the textbook, as long as it is applied correctly.
Another possible issue could be that heat is "captured" through the windows and stored in the walls, so it is not released as quickly when ventilating.Well... yes and no. We were discussing insulation, not heat storage capacity. Materials with a low U-value usually have low heat storage capacity. So the argument actually points in the opposite direction.
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