Big south facing windows!

[NatalieMarie]

Hey everyone! We just moved into a house with huge south facing windows and sliding doors. I‎t warms up the house so much during the day if it’s sunny out- I‎t was 75 in here the other day despite I‎t being 40 degrees outside. However my Father in law mentioned that you lose a lot of heat out those windows at night. So what can I do to keep the heat in? Shutters, blinds, etc? I’m worried about I‎t getting pricey since the windows are huge. Unless I‎t would pay off in energy savings! Plus I don’t want i‎t ugly :) thanks for any advice.


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[GuitarStv]

Curtains and blinds are the way to go for your problem.  We use cellular shades that let a little light through in our south facing windows during the summer days, and pull thick curtains over them during the cold winter nights to limit heat loss.  It makes a noticeable difference keeping temperatures in the house more even.

[nereo]

Curtains for sure.
Also, do you konw what kind of windows those are?  Modern 'Low-E' windows have nano-coatings which reduce the amount of infrared (heat) loss in winter, and are much better than windows from decades past. Depends on how good the window is, but you might be pleasantly surprised how little heat you actually lose from them in winter.

And of course the #1 concern right now is that they are well sealed.  Check the interior and exterior caulk. re-caulk as necessary (fairly cheap and easy to do, but a bit time consuming).  If the window leaks air no amount of curtains, films or other mumbo-jumbo is going to do a lick of good.

[NatalieMarie]

Curtains for the top windows too? I feel like it would look funny?
Also do I get specific curtains that say insulated?

I don’t know on the windows. I wouldn’t say they are super new. My husband is a carpenter and puts in windows all the time, and he said the windows are “pretty good” and he is pretty picky about window quality and how they are installed. But I’ll mention re caulking to him. Thanks!


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[GardenBaker]

I would do curtains on the bottom windows and those roll type shades on the top with the long cords so you can raise and lower them as needed.

[HipGnosis]

Insulated curtains for sure.  I'm pretty sure there is a thread about them on here somewhere.

Also, window film that will reflect (most of?) the heat instead of letting it into the house.  Can be done DIY cheaply if you are careful.  It will also bock/reflect the UV light that fades things.  But you have to be sure to get the film with those properties (not just tint).  I use to work in the plastic film industry.  The window film dept. was so successful that they spun off into their own Co., but they specialized in security / hurricane films.

[ltt]

We do not use curtains for our south-facing windows, but rather a woven-type heavier wooden blind.  The valance extends the length of the window, and then we can pull open the blinds by hand, if needed (no cords).  They have worked out well over the years and look nice.  I would not do anything with the top part of your window.

[NatalieMarie]

Insulated curtains for sure.  I'm pretty sure there is a thread about them on here somewhere.

Also, window film that will reflect (most of?) the heat instead of letting it into the house.  Can be done DIY cheaply if you are careful.  It will also bock/reflect the UV light that fades things.  But you have to be sure to get the film with those properties (not just tint).  I use to work in the plastic film industry.  The window film dept. was so successful that they spun off into their own Co., but they specialized in security / hurricane films.

About the window film...I’m pretty sure I want the heat to come into the house, in the winter? Free heat, and all? In the summer, no.



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[NatalieMarie]

We do not use curtains for our south-facing windows, but rather a woven-type heavier wooden blind.  The valance extends the length of the window, and then we can pull open the blinds by hand, if needed (no cords).  They have worked out well over the years and look nice.  I would not do anything with the top part of your window.

I may go for blinds instead. Curtains seem like they’d be so bulky and ruin the  nice open look. But I’m not sure if blinds look good over sliding doors?


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[nereo]

Insulated curtains for sure.  I'm pretty sure there is a thread about them on here somewhere.

Also, window film that will reflect (most of?) the heat instead of letting it into the house.  Can be done DIY cheaply if you are careful.  It will also bock/reflect the UV light that fades things.  But you have to be sure to get the film with those properties (not just tint).  I use to work in the plastic film industry.  The window film dept. was so successful that they spun off into their own Co., but they specialized in security / hurricane films.

About the window film...I’m pretty sure I want the heat to come into the house, in the winter? Free heat, and all? In the summer, no.

It's a bit more complicated than that.
What films do is reflect back certain wavelengths of light (or frequencies), while allowing other wavelengths through.  The films which retain heat are opaque to infrared light (~700-1,000nm) and nearly transparent  to the visible light spectrum (approx 400-700nm). 

Conceptually what happens is this: The sun shines down and bakes us with a wide spectrum of light, from UV rays to short infrared. In the wintertime infrared is in short supply because of the angle of the sun.  You want visible light to enter unimpeded through your large windows and heat the floors inside (ideally they should be dark to absorb that light nad thick to have a large thermal mass).  Those floors slowly emit heat in the form of infrared wavelenghts, which you want to KEEP inside your house.  That's where the film comes in.  It blocks the infrared wavelenghts (to an infrared camera they would appear very dark) but they let almost all the visible light in.

Note that in the hot summer you want the reverse: you want to keep direct light OUT as to avoid your floors heating up and baking your entire house.  Generally this is done by having awnings over the windows so when the sun is overhead your interior floors are still in shade.

tl/dr: Films allow sunlight IN while reducing the amount of heat that escapes.

[Systems101]

Note that in the hot summer you want the reverse: you want to keep direct light OUT as to avoid your floors heating up and baking your entire house.  Generally this is done by having awnings over the windows so when the sun is overhead your interior floors are still in shade.

In some passively heated houses with the right circumstances [tall (often 2 story) ceilings and reasonable roof overhang (which the OP might have?)] there is another option: Hanging dark cloth "art" from the ceiling a few feet from the windows.  It will be struck by the sun in the winter (doing what you mentioned the floor does) and will be under the angle of what the sun will hit in the summer, thus not requiring any active behavior on the part of the homeowner to change between summer and winter...

I can't seem to find any good pictures (not having luck finding good keywords), but please note the hanging items are not one big panel behind the windows.  They are often installed at 45' angles or some such so there is no surface wider than about 2', and plenty of ability for air to move around between what may be different temperature regions.

[Watchmaker]

I don’t know on the windows. I wouldn’t say they are super new. My husband is a carpenter and puts in windows all the time, and he said the windows are “pretty good” and he is pretty picky about window quality and how they are installed. But I’ll mention re caulking to him. Thanks!

Do you know the brand of the windows?  Are they wooden frames, or vinyl?

If you go outside and look at the windows at an angle you should be able to tell if they have a Low E coating--there will be a slight color to the reflection (usually greenish, and the color may change at different angles).

If you've got Low E coatings that will significantly help with night time heat loss, and also help reduce summer overheating.  Although the second part depends on what type of Low E coating you have, as some are designed to allow as much heat through as possible (for passive solar heating) and some are designed to cut down the solar heat gain (to avoid summer overheating).

With that much glass, insulating blinds or curtains (I like cellular blinds) would be a good idea.  I bought these for my house: https://www.blinds.com/p/blindscom-economy-light-filtering-cellular-shades/530122

     

[NatalieMarie]

Insulated curtains for sure.  I'm pretty sure there is a thread about them on here somewhere.

Also, window film that will reflect (most of?) the heat instead of letting it into the house.  Can be done DIY cheaply if you are careful.  It will also bock/reflect the UV light that fades things.  But you have to be sure to get the film with those properties (not just tint).  I use to work in the plastic film industry.  The window film dept. was so successful that they spun off into their own Co., but they specialized in security / hurricane films.

About the window film...I’m pretty sure I want the heat to come into the house, in the winter? Free heat, and all? In the summer, no.

It's a bit more complicated than that.
What films do is reflect back certain wavelengths of light (or frequencies), while allowing other wavelengths through.  The films which retain heat are opaque to infrared light (~700-1,000nm) and nearly transparent  to the visible light spectrum (approx 400-700nm). 

Conceptually what happens is this: The sun shines down and bakes us with a wide spectrum of light, from UV rays to short infrared. In the wintertime infrared is in short supply because of the angle of the sun.  You want visible light to enter unimpeded through your large windows and heat the floors inside (ideally they should be dark to absorb that light nad thick to have a large thermal mass).  Those floors slowly emit heat in the form of infrared wavelenghts, which you want to KEEP inside your house.  That's where the film comes in.  It blocks the infrared wavelenghts (to an infrared camera they would appear very dark) but they let almost all the visible light in.

Note that in the hot summer you want the reverse: you want to keep direct light OUT as to avoid your floors heating up and baking your entire house.  Generally this is done by having awnings over the windows so when the sun is overhead your interior floors are still in shade.

tl/dr: Films allow sunlight IN while reducing the amount of heat that escapes.

Fascinating! Very cool, I’ll have to look into this! Thanks so much for the thorough response :)


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[NatalieMarie]

Note that in the hot summer you want the reverse: you want to keep direct light OUT as to avoid your floors heating up and baking your entire house.  Generally this is done by having awnings over the windows so when the sun is overhead your interior floors are still in shade.

In some passively heated houses with the right circumstances [tall (often 2 story) ceilings and reasonable roof overhang (which the OP might have?)] there is another option: Hanging dark cloth "art" from the ceiling a few feet from the windows.  It will be struck by the sun in the winter (doing what you mentioned the floor does) and will be under the angle of what the sun will hit in the summer, thus not requiring any active behavior on the part of the homeowner to change between summer and winter...

I can't seem to find any good pictures (not having luck finding good keywords), but please note the hanging items are not one big panel behind the windows.  They are often installed at 45' angles or some such so there is no surface wider than about 2', and plenty of ability for air to move around between what may be different temperature regions.

The ceilings are quite high! Maybe 2 story? Maybe not quite?
That is really interesting. I’m having a hard time picturing it? But I’ll try to find more info.
I’d say about 3 foot of overhang, is that a lot?


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[NatalieMarie]

I don’t know on the windows. I wouldn’t say they are super new. My husband is a carpenter and puts in windows all the time, and he said the windows are “pretty good” and he is pretty picky about window quality and how they are installed. But I’ll mention re caulking to him. Thanks!

Do you know the brand of the windows?  Are they wooden frames, or vinyl?

If you go outside and look at the windows at an angle you should be able to tell if they have a Low E coating--there will be a slight color to the reflection (usually greenish, and the color may change at different angles).

If you've got Low E coatings that will significantly help with night time heat loss, and also help reduce summer overheating.  Although the second part depends on what type of Low E coating you have, as some are designed to allow as much heat through as possible (for passive solar heating) and some are designed to cut down the solar heat gain (to avoid summer overheating).

With that much glass, insulating blinds or curtains (I like cellular blinds) would be a good idea.  I bought these for my house: https://www.blinds.com/p/blindscom-economy-light-filtering-cellular-shades/530122

   

Not sure on brand but they are wood. When the sun come up I’ll look for the coating! Thanks for the blinds link.


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[Rural]

We're passively heated with windows very like the ones in your picture (less fancy in our case, but similar amounts of glass). The low-e coating is quite fabulous at keeping in the heat that the sun provides in winter, and in summer our overhang keeps the sun out completely. The overhang is 22" in our case but the wall is only a slightly tall single story high. We designed our place for passive heat specifically - also concrete floor and earth sheltered for thermal mass. But your place, from the little we know, may also have been designed for some of this, especially with that wide overhang you mentioned. Check for the low-e coating, and see if you get the sun shining in in the summer.


I have nothing on my windows, for what it's worth. Gain far more than we lose, and the closer we get to winter solstice, the more passive heat. As we pass the solstice, the sun heats a little less of the floor every day, but for longer each day. All this works great until we get snowstorms. :)

[Gone_fishing]

Cellular blinds from amazon? You can order custom sizes.
Custom Cordless Single Cell Shades, 24W x 38H, Ivory Beige, Any size from 21" to 72" wide and 24" to 72" high Available https://www.amazon.com/dp/B00LRZNKYK/ref=cm_sw_r_cp_tai_7BYdAbX74P344

[Watchmaker]

Not sure on brand but they are wood. When the sun come up I’ll look for the coating! Thanks for the blinds link.

Low E coatings would be the default for virtually all wood window manufacturers for over a decade, so it sounds like you likely do have low E.

--edited for privacy--

[thenewguy]

It's a bit more complicated than that.
What films do is reflect back certain wavelengths of light (or frequencies), while allowing other wavelengths through.  The films which retain heat are opaque to infrared light (~700-1,000nm) and nearly transparent  to the visible light spectrum (approx 400-700nm). 

Conceptually what happens is this: The sun shines down and bakes us with a wide spectrum of light, from UV rays to short infrared. In the wintertime infrared is in short supply because of the angle of the sun.  You want visible light to enter unimpeded through your large windows and heat the floors inside (ideally they should be dark to absorb that light nad thick to have a large thermal mass).  Those floors slowly emit heat in the form of infrared wavelenghts, which you want to KEEP inside your house.  That's where the film comes in.  It blocks the infrared wavelenghts (to an infrared camera they would appear very dark) but they let almost all the visible light in.

Note that in the hot summer you want the reverse: you want to keep direct light OUT as to avoid your floors heating up and baking your entire house.  Generally this is done by having awnings over the windows so when the sun is overhead your interior floors are still in shade.

tl/dr: Films allow sunlight IN while reducing the amount of heat that escapes.

If I'm understanding correctly, it would be beneficial to apply this type of film to any window... not just those facing south and/or with sun exposure. Although the greatest summertime benefit would be from windows in direct sunlight. Is that accurate?

On another note - most of the windows in my house seem to already have a low-e coating, but there are a couple doors with large windows that don't seem to have the same green reflected hue. There's also a large frosted glass window in the bathroom... is it a safe bet that this window does not have a low-e coating?

[Goldielocks]

We're passively heated with windows very like the ones in your picture (less fancy in our case, but similar amounts of glass). The low-e coating is quite fabulous at keeping in the heat that the sun provides in winter, and in summer our overhang keeps the sun out completely. The overhang is 22" in our case but the wall is only a slightly tall single story high. We designed our place for passive heat specifically - also concrete floor and earth sheltered for thermal mass. But your place, from the little we know, may also have been designed for some of this, especially with that wide overhang you mentioned. Check for the low-e coating, and see if you get the sun shining in in the summer.


I have nothing on my windows, for what it's worth. Gain far more than we lose, and the closer we get to winter solstice, the more passive heat. As we pass the solstice, the sun heats a little less of the floor every day, but for longer each day. All this works great until we get snowstorms. :)

+1
I was going to point out that the solution is not to cover your windows, but to ensure that you have thermal mass inside to warm up in the day, and release heat slowly at night.   Use fans to circulate the heat to the interior in the day, and stop them at night.   Most solar walls are designed to not have fabric coverings for night.  Low e glass (UV protect?), double pane, is used, with an overhang to help prevent summer overheat.

Do you have any problems with being cold at night?