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I have thought about that if I am ever going to build a single floor house this is what I would do. I would make the whole roof out of glass (like a greenhouse). This glass roof would be made out of double glass with as much as 20 cm between the two. In this space I imagine that there would be a very dark curtain, which would stop sunlight in the case where the temperature inside the house gets too high (I am living in Scandinavia so this would just be the case for a few months per year). It would be possible to control the ventilation in the space between the glasses by opening sections of the roof.

The positive effects of this would be:

  • Watching the stars from bed at night
  • Feeling like one is outside the whole day if the curtains are away
  • Less need for lighting

A part of the reason for doing this is that light is a precious thing in Scandinavia during the winter.

What am I missing here? Why have I never heard about such a house (bad research?)?

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6  
If it's worth doing, it's worth overdoing. Check out Smart Glass. –  Tester101 Sep 22 '11 at 18:44
    
Might suck if you live in a snowy area, you'd have to shovel the roof to see out. –  Tester101 Sep 22 '11 at 18:48
    
@Tester101 Thanks for the link. The picture there certainly looks good, I would though still consider this to be glass windows in the roof, but it is close to what I mean. With regards to snow, it takes quite think snow to stop the light, so it can still brighten up the dark autumns and winters even with a few cms of snow on top. –  David Sep 22 '11 at 19:19
8  
You will no longer be able to throw stones. –  Freiheit Sep 23 '11 at 15:10
1  
One word, hail... –  Fiasco Labs Feb 7 '13 at 21:23
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6 Answers 6

up vote 13 down vote accepted

You lose more heat through ceilings than through other surfaces (because the warm air is touching it, and because of good convection currents).

The insulation value of glass is very low. To put it in USA terms, a single pane of glass is R-1, while many house walls are R-20 and ceilings R-30. I've seen superinsulated roofs at R-60. Even triple-pane glass is only R-3; inert gases inside help, but over time they leak; you probably can't have a good seal if you want to run a curtain through them.

During the day, insolation will warm your house through the ceiling (probably too much, even in your part of the world), but at night when you're only losing heat, you'll really feel it. You'll use a lot of energy to stay warm.

At the same time, it would be very expensive. Windows are generally an expensive feature in a house. Sloped windows should be tempered for safety, which makes them even more expensive. And you're talking about a huge area.

Roofs in particular get beat up pretty hard; standard roofs (asphalt shingles) around here last about 20 years.

Meanwhile, you lose the opportunity to put photo-voltaic panels on your roof.

However, you can get a lot of what you're looking for with a much less ambitious approach.

  • Small solar tubes bring in a huge amount of light for their size.

  • A skylight over your bed can let you stargaze in comfort. Put your bed up high for a wide viewing angle.

  • Spend more time outdoors.

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+1 for spending time :) –  Herr K Sep 27 '11 at 18:12
    
Heat gain in the summer will be excessive (we have to take extra measures with greenhouses due to this) and heat loss in winter will also be quite high per the reasons Jay talks about. Go with the solar tubes, I love my illuminated throne. Bathroom used to be a dark hole, in the summer, we rarely have to turn on lights from early morning to late night. The lumen output from a 17" is pretty phenomonal. –  Fiasco Labs May 19 '13 at 15:38
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I once lived in a glass-roofed home. I still miss it. I loved falling asleep looking at the stars and the moon and the treetops. The sunshine was wonderful, too. And on the rare occasions when we had snow it was amazing! Diffuse white igloo light- fabulous! Oh but it was impractical...too cold in winter, too hot in summer. And that was on the mild west coast of Canada where the weather is really very moderate. I did occasionally have cause to wonder about safety, too, when it got stormy. The other issue was cleaning the roof...quite inconvenient and yet necessary. So, please, if you see a way past these issues, do let us know. I still pine for that roof!!

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I say why not build an entire roof out of glass. Here is a loft in New York City that did just that...

http://www.tabakistribeca.com/sales/158_chambers_PH_1685000/pics.htm

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well, perhaps a semantic argument, but I'd call that a large sky light. Still, it's impressive! –  DA01 Feb 3 '12 at 23:38
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As The Evil Greebo states, it's certainly done in many commercial buildings. A great example is the Mall of America, which has a central atrium that has a glass roof.

This glass roof provides enough heat gain in the winter to heat the entire building (with the aid of all the body heat being generated as well...):

Despite Minnesota's cold winters, only the mall's entrances and some below ground areas are heated. Heat is allowed in through skylights above Nickelodeon Universe.

http://en.wikipedia.org/wiki/Mall_of_America

All that said, even though the MoA roof is, overall, flat, the panes of glass are all peaked to handle rain and snow run-off. I don't think you'll find a way to easily build a flat glass roof without a major support grid of some sorts, as the glass itself won't be able to carry the load.

As for never hearing about a house that does this, I'm not sure. Lots of turn-of-the century large houses had glass greenhouses/solariums. An example:

James J Hill House

http://www.mnhs.org/places/sites/jjhh/

And on the more modern residential scale, there's all sorts of greenhouse systems, sunlights, etc.

I think the main reason you don't see a full-glass roof aside from cost is that I imagine it's impractical. Sunlight is important, but a full roof would be a glaring amount of sunlight. You'd have to wear sunscreen and sunglasses in doors all day. Kind of makes watching TV difficult. ;)

Plus, in many climates, the heat gain in the summer and/or heat loss in the winter would be impractical.

I'd suggest building a 3/4 season porch/greenhouse. That gives you the option to sleep there when you want, but you're not committed to a full roof on the entire house.

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Greenhouses have glass roofs. However, they also have steeply pitched roofs to shed snow loads; this means more material use and a challenge when building it. And heating in the winter is VERY expensive. So it is technically feasible, but probably impractical for a living space.

Putting a curtain between the layers is asking for trouble. Sooner or later it'll break, and then you'll have to get access.

However, you don't need a whole glass roof to do what you want. Skylights and large windows can provide most of the same benefits. I have a room in my house with windows along two walls, plus four large skylights in a vaulted roof. I can see the stars through the skylights, I can feel the outside through the large windows, and because the windows face south and west I get good light in there when the sun is up. It does get quite hot in the afternoon, but opening the skylights helps with that. You'd be surprised how much of a difference just a few skylights make.

You could also have a small deck where you can lie out in your sleeping bag. ;)

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Can you do it? Certainly. Commercial buildings have glass roofs all the time.

I expect you'll pay an extremely higher price for such a roof, however, at every stage. The architect fees alone will be a not to pretty penny since this is non standard.

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