Hello Forum,
We are planning to install many large windows in our new build (approx. 300sqm (3,230 sq ft) ground floor + upper floor).
The southwest side will consist of 80-90% glass (window front on the ground floor + large windows on the upper floor). We also have many windows on the north side (but no full window front).
Friends are advising us to reduce the size of many windows because they claim it will lead to heat loss (in winter) and high heating costs.
I’m not very knowledgeable on this yet – I’m currently researching topics like the heat transfer coefficient, etc. But with a well-insulated new build, triple glazing, a heat pump, and a photovoltaic system, I thought heating costs would stay reasonable and not get out of control.
I would appreciate your opinions and experiences. What do you think? What is your advice?
(It has actually been important to us to have many large windows for light, views, etc.).
Thank you for your help and advice.
Best regards
We are planning to install many large windows in our new build (approx. 300sqm (3,230 sq ft) ground floor + upper floor).
The southwest side will consist of 80-90% glass (window front on the ground floor + large windows on the upper floor). We also have many windows on the north side (but no full window front).
Friends are advising us to reduce the size of many windows because they claim it will lead to heat loss (in winter) and high heating costs.
I’m not very knowledgeable on this yet – I’m currently researching topics like the heat transfer coefficient, etc. But with a well-insulated new build, triple glazing, a heat pump, and a photovoltaic system, I thought heating costs would stay reasonable and not get out of control.
I would appreciate your opinions and experiences. What do you think? What is your advice?
(It has actually been important to us to have many large windows for light, views, etc.).
Thank you for your help and advice.
Best regards
I am less concerned about heat losses than about heat gains in summer. So it’s better to ensure effective shading options (such as Venetian blinds).
However, even a good modern window only offers about half the protection against heat loss (or even less) compared to average, standard-compliant masonry with external insulation (EIFS) or wood frame panel walls (0.6 vs. 0.24 W/m²K).
Additional disadvantages of large window fronts:
- Limits on furniture arrangement.
- If you can look outside, people can also look in from the outside.
- Provides less noise protection (or requires special sound-insulating glazing, which in turn reduces thermal insulation or becomes very expensive if both are desired).
- Offers less protection against break-ins.
- Provides less protection against debris blown around in storms.
- Usually does not look as good as expected during the planning phase.
Smaller but well-placed windows can achieve the same benefits, sometimes even adding attractive accents to the interior design, and fit more practically into a normal, lived-in home (which is not a showroom or catalog photo set).
However, even a good modern window only offers about half the protection against heat loss (or even less) compared to average, standard-compliant masonry with external insulation (EIFS) or wood frame panel walls (0.6 vs. 0.24 W/m²K).
Additional disadvantages of large window fronts:
- Limits on furniture arrangement.
- If you can look outside, people can also look in from the outside.
- Provides less noise protection (or requires special sound-insulating glazing, which in turn reduces thermal insulation or becomes very expensive if both are desired).
- Offers less protection against break-ins.
- Provides less protection against debris blown around in storms.
- Usually does not look as good as expected during the planning phase.
Smaller but well-placed windows can achieve the same benefits, sometimes even adding attractive accents to the interior design, and fit more practically into a normal, lived-in home (which is not a showroom or catalog photo set).
N
nordanney27 Jan 2025 21:27SuoTam99 schrieb:
But with a well-insulated new build, triple-glazed windows, heat pump, photovoltaic system The only factor affecting energy consumption is the insulation. Windows simply insulate significantly less.
However, they also let heat in – like today, when my heating was off for almost the entire day. So please remember to consider shading for the summer.
Aside from that, I find the question about heating costs unnecessary for a house that will cost seven figures.
Whether heating costs increase by 25€ per month is negligible.
That’s the scale we are talking about.
P.S. For such a special house with a lot of glass, professional external heating system planning is essential. That way, you have a well-functioning house in winter.
I have always liked large window areas, and of course, there are always recurring opinions about cleaning and so on. People who have large windows tend to like them, while those who don’t simply don’t, although in our case, people really enjoy them without usually mentioning any of the common caveats.
Beautiful things are not always practical or come without consequences that you should be aware of.
This time, I was a bit uncertain about overheating because I don’t like overheated rooms, so we installed an air conditioning system to avoid this problem. In hindsight, it wasn’t absolutely necessary for our build, but it was still a great decision for us, especially since with the photovoltaic system we basically have no operating costs, and we occasionally use it for targeted heating.
Shading is very important; we have external venetian blinds (Raffstore) on the south and west sides, and I would strongly recommend that to you. We don’t have roof overhangs.
I would also recommend insulating the house thoroughly, meaning the roof, walls, and facade. Your energy consultant will tell you where to do more or less insulation; I would go for maximum insulation, for example, including insulated roofing.
Even in winter, from about 9 a.m., the sun often makes the house pleasantly warm, which we really like. We have very few windows on the north side, actually only where we need natural light for the room, but this also depends on the location of the house.
I wouldn’t try to put windows everywhere just for the sake of it because, as mentioned, you still need wall space for furniture and other things.
You could post your plan or pictures here, and then maybe more can be said, including information about the plot and orientation.
The photovoltaic system provides little heating support in winter, but if the house is well insulated, you won’t need much anyway. We have a KfW 40 standard or better, and I would recommend that to you as well — then nothing problematic will happen.
Beautiful things are not always practical or come without consequences that you should be aware of.
This time, I was a bit uncertain about overheating because I don’t like overheated rooms, so we installed an air conditioning system to avoid this problem. In hindsight, it wasn’t absolutely necessary for our build, but it was still a great decision for us, especially since with the photovoltaic system we basically have no operating costs, and we occasionally use it for targeted heating.
Shading is very important; we have external venetian blinds (Raffstore) on the south and west sides, and I would strongly recommend that to you. We don’t have roof overhangs.
I would also recommend insulating the house thoroughly, meaning the roof, walls, and facade. Your energy consultant will tell you where to do more or less insulation; I would go for maximum insulation, for example, including insulated roofing.
Even in winter, from about 9 a.m., the sun often makes the house pleasantly warm, which we really like. We have very few windows on the north side, actually only where we need natural light for the room, but this also depends on the location of the house.
I wouldn’t try to put windows everywhere just for the sake of it because, as mentioned, you still need wall space for furniture and other things.
You could post your plan or pictures here, and then maybe more can be said, including information about the plot and orientation.
The photovoltaic system provides little heating support in winter, but if the house is well insulated, you won’t need much anyway. We have a KfW 40 standard or better, and I would recommend that to you as well — then nothing problematic will happen.
W
wiltshire27 Jan 2025 22:59Tolentino schrieb:
I wouldn’t worry so much about heat loss as about heat gain in the summer.Yes. In a well-insulated house, it’s hard to get rid of heat — many people forget that. Besides external blinds, there are options like reflective coatings, roof overhangs, patio sails, and awnings...
Only doing nothing would be foolish.
Tolentino schrieb:
Additional disadvantages of large window fronts:All the "disadvantages" are manageable. In large houses with spacious rooms, the arrangement of furniture is quite different from floor area–optimized houses. Large window fronts rarely interfere there.
Visibility into the house depends on the location and exterior design — it can be controlled. Choose your plot carefully...
Protection against burglars and storms — glass obviously has inherent but manageable drawbacks here.
And regarding appearance: anyone building a house in the seven-figure range should choose an appropriate architect. I know several exceptionally well-designed glass façades.
The only definite disadvantage remains the higher cost for a good solution. But: if you can solve a problem with available money, then you should solve it with money. If you can’t solve a problem with money, you shouldn’t even try.
nordanney schrieb:
Apart from that, I consider the question of heating costs irrelevant for a house that will cost seven figures. Whether heating costs are 25€ more per month is negligible."Watch after the pennies, and the pounds will watch after themselves." On that note: some people don’t want to discuss ecological issues at home — the fact that building a new single-family house is already an ecological disaster comes up less often in couple discussions than the more tangible ecological footprint from consumption behavior.
nordanney schrieb:
P.S. For such a special house with lots of glass, external professional heating system planning is essential. Then you’ll have a well-functioning house in winter.Absolutely yes! SuoTam99 schrieb:
Our acquaintances are now advising us to reduce the size of many windows because they claim it will cause heat loss (in winter) and lead to high heating costs.Are your acquaintances advising you in the sense of “giving advice,” or are they guessing based on “I don’t really know, but my half-knowledge tells me that...” Get clear about your own preferences and then about the implementation options. Then no one needs to give you unsolicited “advice” from outside.
Experience: We have large windows — you could even call it window fronts — a suitable roof overhang that keeps some of the sun out in high summer, and we live quite comfortably in the house. Not everyone’s cup of tea — but certainly not wrong either.
Now a 2-meter (6.6-foot) deep balcony makes sense.
Windows are great. I couldn’t afford them. Or rather, I can’t afford a very expensive house where window areas are part of the design.
However, in my personal opinion, a solid wall section can positively complement a large window area.
Regarding insulation: yes, some efficiency is probably lost. But with 300 square meters (3,229 square feet), a lot of heat loss occurs due to the additional, unnecessary surface area anyway, so in the case of windows it really amounts to peanuts. The window cleaner will cost more and will need to put in more effort.
Windows are great. I couldn’t afford them. Or rather, I can’t afford a very expensive house where window areas are part of the design.
However, in my personal opinion, a solid wall section can positively complement a large window area.
Regarding insulation: yes, some efficiency is probably lost. But with 300 square meters (3,229 square feet), a lot of heat loss occurs due to the additional, unnecessary surface area anyway, so in the case of windows it really amounts to peanuts. The window cleaner will cost more and will need to put in more effort.
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