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!
roookeee schrieb:
depending on how practical it feelsAlso here: Carry a folding ruler with you and measure everything you see—wherever you are. Door widths can be tricky too: Take a laundry basket and try walking straight through with it. Or a crate of beer. Do you have enough space between the door frame and your ankles? In our rental apartment, we have a patio door that is 1.20 m (4 feet) wide—I wouldn’t want to do without it anymore. You might also want to reconsider making utility room doors narrower if you need space for storage boxes there.
I’ve learned to pay attention to many such seemingly minor details, and I’m very grateful for that 🙂
-LotteS- schrieb:
Also here too: Always carry a tape measure and measure everything you see—wherever you are. Door widths are another thing: Take a laundry basket and try walking straight through. Or a crate of beer. We have a patio door in our rental with a width of 1.20m (4 feet), and I wouldn’t want to do without it anymore. It’s worth reconsidering making utility room doors narrower if storage boxes need to fit there.
I’ve learned to pay attention to many of these seemingly small details here, and I’m very grateful for that 🙂 That’s true, we’ve already rushed through all sorts of houses like crazy people, measuring rooms and checking how a space with X m² (X sq ft) feels as a kitchen to get a better sense of what “works.” We’re positioning every little item precisely and seeing if, for example, the drying rack won’t be in the way where it’s finally placed 🙂 We should do the same for windows, but unfortunately, we don’t know many people with new builds where we could try this out. At least one person comes to mind, but they have something like fully glazed open galleries in a city villa—hopefully, they also have “normal” windows. I’m adding it to the list!
roookeee schrieb:
We still have an "architect consultation" ahead of us. I’m not sure yet who exactly will be talking with us; I might ask. Maybe we’ll also post the floor plans here, depending on how motivated we are to deal with the forum’s tone. In general contractor (GC) contracts, the "architect consultation" usually refers to a coordination meeting with the person responsible for preparing the building permit / planning permission documents. This person is sometimes a licensed architect, but often a draftsman. Genuine creative input is rarely part of these meetings. The critical feedback here has helped many forum members progress and build resilience against the tone used.
roookeee schrieb:
We don’t want floor-to-ceiling windows upstairs and must follow the development plan requiring one-and-a-half stories with a roof pitch between 40 and 60°, so we would likely have to rely heavily on roof windows [...] A dormer would cost about 15k, excluding windows. Roof windows are especially relevant for rooms located in the middle of the eaves, while rooms with gable-end exterior walls are more cost-effectively lit through those walls. The lower part of floor-to-ceiling windows can be fitted with frosted glass. Dormers (often called “cross-gables”) can usually be built on up to one third of the length of the eaves and provide standing height, which makes a significant difference. I would choose a roof pitch closer to 40° rather than 60° because this allows for some knee wall within the restriction of not having a full additional story. At 60° pitch, roof structures have to be kept minimal and roof windows become the only option. Most standard plan catalogs are well optimized in this regard, whereas custom designs often struggle trying to improve on this.
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11ant schrieb:
In general contractors’ context, the “architect” meeting usually refers to a coordination meeting with the person responsible for preparing the building permit application, who are sometimes architects but often simply draftspeople. Genuine creativity is rarely part of this process. The criticism here has already helped many questioners and toughened them up against the tone used. We have also asked here before about other topics and received help; surely we will come back soon with the floor plan. It’s somehow unfortunate that one can expect so little from an average general contractor, but unfortunately this has become very clear to us through many conversations with different contractors on other topics. You really have to try to know everything, preferably better than they do—that’s why this thread exists.
11ant schrieb:
Roof windows are especially important for rooms with a central eaves position; rooms with side-gable exterior walls are better lit through those. The lower part of floor-to-ceiling windows can be fitted with frosted glass. Maybe we are unusual, but floor-to-ceiling windows on the upper floor are really not an option for us. Subjectively, they feel intrusive (even with frosted glass, silhouettes, and similar treatments, they still feel exposed), they are annoying to clean (you can’t imagine the hassle unless you like rearranging furniture every time you clean), and we find the resulting low window sills unattractive. As I said, this is just our taste; there are many advantages to them, especially regarding the price.
11ant schrieb:
Dormers (usually rather transverse gable dormers) can usually be built on up to about a third of the roof’s eaves length and provide standing height, which makes a significant difference. I would choose a roof pitch closer to 40° rather than 60°. I found the price quite steep, especially since 15k is for the “small” dormer, which only fits one “smaller” window per room (we didn’t ask in detail, so this is vague). Do you think it’s worth it? This would then replace the two other Velux windows, so effectively 9k more expensive without windows and blinds. We think we can live with the standing height as small people; I’m used to a 60cm (24 inches) clear knee wall from childhood and it doesn’t bother me much. We are planning a 45° roof with a 90cm (35 inches) clear knee wall, which I think is acceptable for that roof pitch. We definitely agree with you on the roof pitch.
ateliersiegel21 Sep 2023 08:37In rural Lower Bavaria, I noticed that farmers tend to keep the blinds half-closed all day in their new houses with large windows.
I once lived in a log house there and was worried that I might feel uncomfortable with the small windows. That was not a problem at all. I really liked the house.
I think a farmer is glad not to have to constantly look out at the surrounding landscape while inside the house. 🤨
My assumption is that it largely depends on your profession and where you spend your day – and, of course, on what there is to see outside.
But: no doubt about it, natural light is wonderful.
I once lived in a log house there and was worried that I might feel uncomfortable with the small windows. That was not a problem at all. I really liked the house.
I think a farmer is glad not to have to constantly look out at the surrounding landscape while inside the house. 🤨
My assumption is that it largely depends on your profession and where you spend your day – and, of course, on what there is to see outside.
But: no doubt about it, natural light is wonderful.
X
xMisterDx21 Sep 2023 09:11Sorry, but... you’re worried about having too little window area or not enough light, and then you plan to skip floor-to-ceiling windows on the upper floor? Those actually provide the most light.
For a floor-to-ceiling window, you would need to install a balustrade window twice as wide. However, this reduces the wall space where you could place cabinets, install shelves, or hang pictures...
For a floor-to-ceiling window, you would need to install a balustrade window twice as wide. However, this reduces the wall space where you could place cabinets, install shelves, or hang pictures...
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