Hello everyone,
We are currently planning our floor layout and have come across differing recommendations regarding the amount of window area needed, depending on whether you:
Of course, we understand that calculating illuminance (lux) is much more complex than just a simple rule of thumb, but for budgeting purposes, we want to estimate a reasonable number of windows upfront to avoid being caught off guard later when we might need to add windows costing an additional $10,000–15,000.
So, we are wondering how a roughly 20m² (215 sq ft) room in a 1.5-story house could possibly meet a 20% window-to-floor area ratio. Even with two skylights (Velux) providing an effective window area of 1.16m² (12.5 sq ft) and a 160 x 140 cm (63 x 55 inches) double window (estimated at about 100 x 110 cm (39 x 43 inches) effective window area after accounting for frames, etc.), we only reach 17.3%! The same applies to the closed kitchen downstairs, where two windows each measuring 120 x 100 cm (47 x 39 inches), estimated at about 90 x 70 cm (35 x 28 inches) effective window area after frame deductions, wouldn’t even reach 10% – somehow it feels like we might be missing something here.
So the question is: how much window area (as a rule of thumb) should you really aim for? Where is the sweet spot so that you don’t have to install two floor-to-ceiling windows and 10 skylights in every room? As mentioned, we just want to understand whether 20-25% is a realistic guideline to aim for, or if it’s mostly marketing hype — especially since Velux tends to promote these figures heavily on their websites. We want to avoid building a dark, poorly lit home, and retrofitting windows later sounds like a real hassle.
Thanks a lot!
We are currently planning our floor layout and have come across differing recommendations regarding the amount of window area needed, depending on whether you:
- follow the national building code – according to information online, this would suggest having about 10-12% of the floor area as window area
- follow newer guidelines such as DIN EN 17037, which recommend 20-25% as a rough rule of thumb
Of course, we understand that calculating illuminance (lux) is much more complex than just a simple rule of thumb, but for budgeting purposes, we want to estimate a reasonable number of windows upfront to avoid being caught off guard later when we might need to add windows costing an additional $10,000–15,000.
So, we are wondering how a roughly 20m² (215 sq ft) room in a 1.5-story house could possibly meet a 20% window-to-floor area ratio. Even with two skylights (Velux) providing an effective window area of 1.16m² (12.5 sq ft) and a 160 x 140 cm (63 x 55 inches) double window (estimated at about 100 x 110 cm (39 x 43 inches) effective window area after accounting for frames, etc.), we only reach 17.3%! The same applies to the closed kitchen downstairs, where two windows each measuring 120 x 100 cm (47 x 39 inches), estimated at about 90 x 70 cm (35 x 28 inches) effective window area after frame deductions, wouldn’t even reach 10% – somehow it feels like we might be missing something here.
So the question is: how much window area (as a rule of thumb) should you really aim for? Where is the sweet spot so that you don’t have to install two floor-to-ceiling windows and 10 skylights in every room? As mentioned, we just want to understand whether 20-25% is a realistic guideline to aim for, or if it’s mostly marketing hype — especially since Velux tends to promote these figures heavily on their websites. We want to avoid building a dark, poorly lit home, and retrofitting windows later sounds like a real hassle.
Thanks a lot!
W
WilderSueden21 Sep 2023 09:16The lower section of the floor-to-ceiling windows doesn’t add much. It’s better to have 2sqm (21.5 sq ft) of windows placed horizontally rather than vertically.
X
xMisterDx21 Sep 2023 09:20Yes. Cola is well known to taste better from the bottle than from a glass.
W
WilderSueden21 Sep 2023 10:06It’s quite simple. If you remove the upper part of a floor-to-ceiling window, you get the appearance of a cave. Light enters at an angle, and if it comes in at a height of 30cm (12 inches), it doesn’t reach very far into the room. Aside from the fact that there are also objects placed in rooms
xMisterDx schrieb:
For a floor-to-ceiling window, you need to install a parapet window that is twice as wide. However, this reduces the wall space available for placing cabinets, installing shelves, or hanging pictures...In front of a parapet window, there is still space for a chest of drawers, a low shelf, a desk, or a bed.
xMisterDx schrieb:
Yes. It is well known that cola tastes better than from a glass. Technically, the vessel from which you drink does have a significant influence on the taste.
In that sense, it is a very good comparison. Windows are similar in this regard.
In the end, the first responsibility of any homebuilder always applies: Make a decision!
xMisterDx schrieb:
For a floor-to-ceiling window, you need to install a window with a sill height twice as wide. A narrower floor-to-ceiling window (about 80cm (31 inches) wide) is essentially the same as a poorly regarded window band – the only difference is that the light entering only illuminates a narrow strip inside the room, as @WilderSueden explained well.
It is better to choose a 160-200cm (63-79 inches) wide sill-height window, which can effectively and sustainably light a 3-4 meter (10-13 feet) wide room.
xMisterDx schrieb:
But that reduces the wall area where you can place cabinets, install shelves, or hang pictures… In front of a sill, you can nicely place a desk or shelving unit.
@roookeee good decision!
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