Doors and Windows - Windows - Building a home and need expert opinions
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Scott_Free
09-01-05, 03:37 PM
Hi,
We are in the process of building a new home, and personally I like to research every aspect on things I purchase, and I have been reading up on windows and doors as much as I can and have a few questions that I was hoping the experts can help me with.
We are looking to get black exterior windows that meet R2000 standards, and we are undecided if we want the interior of the winodow to also be black (the window frame). More then likely we are leaning towards vinyl, unless I hear something to turn me off.
From what I understand the R-rating is the important number for picking an energy efficient window. The U rating just being R = 1/U. Now we are building an R2000 home and I am sure will be limited to what types of windows we can actually choose from (meeting next week with the builder). I have read/heard lots about double pane vs triple pane, etc. I understand that Low-E glass is a must with an argon(or similar gas in between panes), and a low conductive spacer.
I had one gentlemen tell me that there really is no difference between triple pane and double pane windows, since you can only have 2 low-e panes of glass in a window. Thus making the third pane simply a piece of glass.
After all that here are my questions:
1) Please correct me where I have misinformation.
2) When looking at efficient windows should I only concern myself with the R rating?
3) Is there a differnece between double and triple pane windows other then a 3rd piece of glass?
4) Are there any hidden costs or things I should be aware of?
All of your help is greatly appreciated as I am a noob when it comes to these types of things and am trying to learn enough to make educated decisions.
Thanks in advance.
Scott
We are in the process of building a new home, and personally I like to research every aspect on things I purchase, and I have been reading up on windows and doors as much as I can and have a few questions that I was hoping the experts can help me with.
We are looking to get black exterior windows that meet R2000 standards, and we are undecided if we want the interior of the winodow to also be black (the window frame). More then likely we are leaning towards vinyl, unless I hear something to turn me off.
From what I understand the R-rating is the important number for picking an energy efficient window. The U rating just being R = 1/U. Now we are building an R2000 home and I am sure will be limited to what types of windows we can actually choose from (meeting next week with the builder). I have read/heard lots about double pane vs triple pane, etc. I understand that Low-E glass is a must with an argon(or similar gas in between panes), and a low conductive spacer.
I had one gentlemen tell me that there really is no difference between triple pane and double pane windows, since you can only have 2 low-e panes of glass in a window. Thus making the third pane simply a piece of glass.
After all that here are my questions:
1) Please correct me where I have misinformation.
2) When looking at efficient windows should I only concern myself with the R rating?
3) Is there a differnece between double and triple pane windows other then a 3rd piece of glass?
4) Are there any hidden costs or things I should be aware of?
All of your help is greatly appreciated as I am a noob when it comes to these types of things and am trying to learn enough to make educated decisions.
Thanks in advance.
Scott
Concretemasonry
09-01-05, 04:11 PM
Just a minor technical correction - based on my past exprience, but some of the laws of physics may have been repealed since I did some calculations.
An R-value is the insulating value of a building material, usually per inch of thickness. If all layers are continuous, then you just add to get the total R-value of an assembly. This does not work for stud walls.
The U-value is usually thought of as the heat loss of a wall (not an individual material). A wall usually consists of several layers (usually continuous except for Fiberglas/wood or steel). The R-value of the wall is the total of the R-values for the different layers PLUS the R-value (or insulating value) of the air film on both sides of the wall (usually .85). The U-value is then the reciprocal of the total wall R-value (including the films). The additional heat loss through the studs or joists is a separate reduction in the R-value of a layer that is addressed in the ASHRAE standards.
The air film makes little difference on the fictitious R-19 wall you see (only about 5%), but it does make a difference when comparing wall sections with lower R-values like windows. Anybody selling insulation should be asked whether it is for the material or for the wall or roof section. Something with a R-5 could really be a R-6 depending on how it is stated (about 16%).
Just make sure you are comparing apples with apples.
Not a major item, but worth considering.
Dick
An R-value is the insulating value of a building material, usually per inch of thickness. If all layers are continuous, then you just add to get the total R-value of an assembly. This does not work for stud walls.
The U-value is usually thought of as the heat loss of a wall (not an individual material). A wall usually consists of several layers (usually continuous except for Fiberglas/wood or steel). The R-value of the wall is the total of the R-values for the different layers PLUS the R-value (or insulating value) of the air film on both sides of the wall (usually .85). The U-value is then the reciprocal of the total wall R-value (including the films). The additional heat loss through the studs or joists is a separate reduction in the R-value of a layer that is addressed in the ASHRAE standards.
The air film makes little difference on the fictitious R-19 wall you see (only about 5%), but it does make a difference when comparing wall sections with lower R-values like windows. Anybody selling insulation should be asked whether it is for the material or for the wall or roof section. Something with a R-5 could really be a R-6 depending on how it is stated (about 16%).
Just make sure you are comparing apples with apples.
Not a major item, but worth considering.
Dick
XSleeper
09-01-05, 05:11 PM
You absolutely should not go by the r-value when buying windows. As the cement guy said, R-value refers to insulating properties, while U-value refers to heat loss. That being said, windows are primarily heat LOSERS, which is why people are so concerned about getting the best performance.
On every window sold in the USA, there will be an NFRC sticker, which states 3 things: u-value, solar heat gain coefficient, and visible light transmittance. The most important one is the u-value. All you need to know when comparing windows is that the lower the u-value the better. The NFRC stickers allow people to compare apples to oranges; wood windows, vinyl windows, fiberglass windows, that is all taken into account when looking at the NFRC sticker. The only problem is that your window salesman can't tell you exact u-values in the showroom... whatever he says will be his best estimate based on whatever information he has in his order books.
Salesmen often try to tote the r-values of their windows, saying they have an "r-20" window (which simply isn't possible because a 2x4 wall is only r-11 or 13, and your window cannot be warmer than your wall, it's not possible.) Part of the frame of the window may be composed of materials that might be efficient, but MOST of the thermal loss will be through the glass. THAT's what's important.
So, getting the right glass is very important in whatever whind you choose, whether it be aluminum or vinyl clad wood, vinyl or fiberglass (which, by the way is the best choice of the three). Whoever told you that triple pane glass is not better than double pane glass has no idea what he's talking about. The spacer bar is very important, as the glass edge is the main place where thermal loss takes place. It sounds like you are knowledgable about demanding low-e argon (triple pane is usually krypton, which is more efficient in thin air spaces), and other new options that may not be available from all suppliers are Heat Mirror and Superglass Quad.
Since it's a new home, you will want to make sure the window installers don't just slap the windows in- they should use peel and stick membranes, which are the latest innovation in sealing windows- not only from air, but also from water infiltration. Other innovations are low expanding window and door foams, which generally do a better job of insulating and eliminating air infiltration than fiberglass.
Only other thing I might say is that I've never heard of a black vinyl window. I think it would probably melt. If you insist on black you will probably have to go with a painted aluminum clad, wood window. I've heard that fiberglass windows can also come in almost any color.
Hope that gets you started.
On every window sold in the USA, there will be an NFRC sticker, which states 3 things: u-value, solar heat gain coefficient, and visible light transmittance. The most important one is the u-value. All you need to know when comparing windows is that the lower the u-value the better. The NFRC stickers allow people to compare apples to oranges; wood windows, vinyl windows, fiberglass windows, that is all taken into account when looking at the NFRC sticker. The only problem is that your window salesman can't tell you exact u-values in the showroom... whatever he says will be his best estimate based on whatever information he has in his order books.
Salesmen often try to tote the r-values of their windows, saying they have an "r-20" window (which simply isn't possible because a 2x4 wall is only r-11 or 13, and your window cannot be warmer than your wall, it's not possible.) Part of the frame of the window may be composed of materials that might be efficient, but MOST of the thermal loss will be through the glass. THAT's what's important.
So, getting the right glass is very important in whatever whind you choose, whether it be aluminum or vinyl clad wood, vinyl or fiberglass (which, by the way is the best choice of the three). Whoever told you that triple pane glass is not better than double pane glass has no idea what he's talking about. The spacer bar is very important, as the glass edge is the main place where thermal loss takes place. It sounds like you are knowledgable about demanding low-e argon (triple pane is usually krypton, which is more efficient in thin air spaces), and other new options that may not be available from all suppliers are Heat Mirror and Superglass Quad.
Since it's a new home, you will want to make sure the window installers don't just slap the windows in- they should use peel and stick membranes, which are the latest innovation in sealing windows- not only from air, but also from water infiltration. Other innovations are low expanding window and door foams, which generally do a better job of insulating and eliminating air infiltration than fiberglass.
Only other thing I might say is that I've never heard of a black vinyl window. I think it would probably melt. If you insist on black you will probably have to go with a painted aluminum clad, wood window. I've heard that fiberglass windows can also come in almost any color.
Hope that gets you started.
Oberon
09-01-05, 05:17 PM
Hi Scott,
Many questions, so here goes...
First, the installation of the unit is of utmost importance, no matter what window you choose. I would venture to say that the installation is the single most important part of the window...in the sense that if the install is screwed up then the entire window is screwed up. The best window in the world will do you no good if it is installed incorrectly.
Next, a triple pane window - without LowE coating - is less energy efficient than a dual pane window with a LowE coating. But, a triple pane window that has LowE coated lites is more efficient than a dual pane.
There are three types of LowE coatings currently on the market (plus several minor derivatives). The first type is a pyrolytic or hardcoat and the other two are both "sputter" or softcoat. The primary difference between the two types of softcoat LowE coatings is that one is a high solar gain product and the other is a low solargain product. Both are better than the hardcoat.
Generally, you want your LowE coating on the inside surface of the exterior lite in a dual pane IGU, or insulating glass unit. This is referred to as surface #2 in the window industry. Surface #1 is the actual exterior of the exterior lite and surface #4 is the surface you actually touch inside your house. Surface #3 (by process of elimination), is the inside surface of the inner lite...I hope that that makes sense, because I will reference those numbers again before I am finished.
What a LowE coating does is to block heat from passing thru the glass. Heat always travels to cold unless acted upon by an outside force. What you want in your window (or any insulation) is to ensure that the outside heat in summer stays outside and the inside heat in winter stays inside. Forget cold, cold does not exist...there is heat and absense of heat...that is what you are dealing with when dealing with any sort of insulation.
Generally, the various LowE coatings do a rather good job of blocking heat flow. Specifically, a high solar gain LowE coating blocks "ordinary" heat from passing thru the glass, but it does little to stop direct solar-gain energy (or heat) from passing thru the glass. A low solar gain coating stops "ordinary" heat, but it also blocks a good bit of solar energy as well. If you get that coating in a tinted version, it blocks even more solar heat from passing thru the window and also blocks a good bit of sun glare as well. Depending on your climate, and also your personal preference, will help determine which type of LowE coating is right for you.
In a primarily cooling climate, then you absolutely want a low solar gain coating...this is a no-brainer. In a "equal" heating and cooling climate, then you still want a low solar gain coating. Studies have shown (extensively) that any solar energy or heat gain that you might realize in winter with a high solar gain coating is more than offset by the amount of heat you will gain in summer because of that same solar gain...and in winter, that gain will not equal the loss of heat when the sun isn't shining directly on the window. The low solar gain product also is better at blocking "ordinary" heat flow as well.
But, what about if you live somewhere in the great white north? Well, in that case, studies have shown that if you are someone who is really serious about energy conservation and you take all the right steps to maximize winter solar gain and minimize summer solar gain, then the high solar heat gain product will be more advantageous to you than the low solar gain product...but, if you are someone who would rather "install it and forget it", then the low solar gain product still would give better results, even in the north.
Remember the surface layer numbers? As mentioned, LowE coatings are generally installed on surface #2 of the IGU...except, when you want maximum benefit from using a high solar gain product, in which case installing the window with the coating on surface #3 is the way to go.
I am going to stop this now, because it is long. But, I am going to continue in another post... :rolleyes:
Many questions, so here goes...
First, the installation of the unit is of utmost importance, no matter what window you choose. I would venture to say that the installation is the single most important part of the window...in the sense that if the install is screwed up then the entire window is screwed up. The best window in the world will do you no good if it is installed incorrectly.
Next, a triple pane window - without LowE coating - is less energy efficient than a dual pane window with a LowE coating. But, a triple pane window that has LowE coated lites is more efficient than a dual pane.
There are three types of LowE coatings currently on the market (plus several minor derivatives). The first type is a pyrolytic or hardcoat and the other two are both "sputter" or softcoat. The primary difference between the two types of softcoat LowE coatings is that one is a high solar gain product and the other is a low solargain product. Both are better than the hardcoat.
Generally, you want your LowE coating on the inside surface of the exterior lite in a dual pane IGU, or insulating glass unit. This is referred to as surface #2 in the window industry. Surface #1 is the actual exterior of the exterior lite and surface #4 is the surface you actually touch inside your house. Surface #3 (by process of elimination), is the inside surface of the inner lite...I hope that that makes sense, because I will reference those numbers again before I am finished.
What a LowE coating does is to block heat from passing thru the glass. Heat always travels to cold unless acted upon by an outside force. What you want in your window (or any insulation) is to ensure that the outside heat in summer stays outside and the inside heat in winter stays inside. Forget cold, cold does not exist...there is heat and absense of heat...that is what you are dealing with when dealing with any sort of insulation.
Generally, the various LowE coatings do a rather good job of blocking heat flow. Specifically, a high solar gain LowE coating blocks "ordinary" heat from passing thru the glass, but it does little to stop direct solar-gain energy (or heat) from passing thru the glass. A low solar gain coating stops "ordinary" heat, but it also blocks a good bit of solar energy as well. If you get that coating in a tinted version, it blocks even more solar heat from passing thru the window and also blocks a good bit of sun glare as well. Depending on your climate, and also your personal preference, will help determine which type of LowE coating is right for you.
In a primarily cooling climate, then you absolutely want a low solar gain coating...this is a no-brainer. In a "equal" heating and cooling climate, then you still want a low solar gain coating. Studies have shown (extensively) that any solar energy or heat gain that you might realize in winter with a high solar gain coating is more than offset by the amount of heat you will gain in summer because of that same solar gain...and in winter, that gain will not equal the loss of heat when the sun isn't shining directly on the window. The low solar gain product also is better at blocking "ordinary" heat flow as well.
But, what about if you live somewhere in the great white north? Well, in that case, studies have shown that if you are someone who is really serious about energy conservation and you take all the right steps to maximize winter solar gain and minimize summer solar gain, then the high solar heat gain product will be more advantageous to you than the low solar gain product...but, if you are someone who would rather "install it and forget it", then the low solar gain product still would give better results, even in the north.
Remember the surface layer numbers? As mentioned, LowE coatings are generally installed on surface #2 of the IGU...except, when you want maximum benefit from using a high solar gain product, in which case installing the window with the coating on surface #3 is the way to go.
I am going to stop this now, because it is long. But, I am going to continue in another post... :rolleyes:
Oberon
09-01-05, 05:34 PM
Hey XSleeper...looks like we were typing at the same time...and saying much the same thing, except that I am very verbose...and you got yours on first :D
Okay, the advantages of surface #2 versus surface #3. In a nutshell, LowE coatings block heat. If the LowE coating is on surface #2, and you are in a cooling climate or at least summer, then the exterior heat is blocked by the coating on the outer lite. This keeps the outside heat (for the most part) from penetrating into the IGU airspace. The IGU airspace then is closer to the inside temperature of the home and more comfortable for the folks living there.
In the winter, the LowE coating blocks the heat exiting the house, after it has penetrated into the space between the lites. This again allows that space to be closer to the inside temerature of the house and thus more comfortable.
But, if you want maximum solar gain, you want that solar heat to penetrate into the IGU airspace and by placing the coating on surface #3, or the inner surface of the inner lite, you allow that to happen. Of course in summer that becomes a disadvantage.
Argon and krypton gases are both used for improving the insulating value of a window. As XSleeper said, argon is generally used in dual pane and krypton in triple pane. Krypton is substantially better than argon in the narrow airspace of a triple pane, in the wider airspace of a dual pane the values are not that much different and krypton is not worth the additional cost.
Also as was said earlier, ignore R value when looking at windows. U value is the meaningful figure. U value measures actual heat flow thru the window unit and R value measures resistance to heat flow. Doesn't sound like much difference, but the prior posts explained it very well. And while I wouldn't go so far as to call R value a "ficticious" number, I totally agree with concrete-man that it is not the best way to determine insulating values, whether in a wall or a window, or a combination of both. Personally, I would use the term "hypothetical", but that is just my opinion (actually Dick, I would consider it a major item - I think you made a great point). ;)
Like XSleeper, I also am not particularly familiar with black windows. You probably can get black, or something similar, in aluminum and maybe fiberglass, but never vinyl. I agree that it would possibly melt and at the very least distort the vinyl if it was black.
Scott, looks like you have your work cut out for you, and after reading these three replies if you don't have a bunch of questions I will eat my keyboard!
Good luck!
Okay, the advantages of surface #2 versus surface #3. In a nutshell, LowE coatings block heat. If the LowE coating is on surface #2, and you are in a cooling climate or at least summer, then the exterior heat is blocked by the coating on the outer lite. This keeps the outside heat (for the most part) from penetrating into the IGU airspace. The IGU airspace then is closer to the inside temperature of the home and more comfortable for the folks living there.
In the winter, the LowE coating blocks the heat exiting the house, after it has penetrated into the space between the lites. This again allows that space to be closer to the inside temerature of the house and thus more comfortable.
But, if you want maximum solar gain, you want that solar heat to penetrate into the IGU airspace and by placing the coating on surface #3, or the inner surface of the inner lite, you allow that to happen. Of course in summer that becomes a disadvantage.
Argon and krypton gases are both used for improving the insulating value of a window. As XSleeper said, argon is generally used in dual pane and krypton in triple pane. Krypton is substantially better than argon in the narrow airspace of a triple pane, in the wider airspace of a dual pane the values are not that much different and krypton is not worth the additional cost.
Also as was said earlier, ignore R value when looking at windows. U value is the meaningful figure. U value measures actual heat flow thru the window unit and R value measures resistance to heat flow. Doesn't sound like much difference, but the prior posts explained it very well. And while I wouldn't go so far as to call R value a "ficticious" number, I totally agree with concrete-man that it is not the best way to determine insulating values, whether in a wall or a window, or a combination of both. Personally, I would use the term "hypothetical", but that is just my opinion (actually Dick, I would consider it a major item - I think you made a great point). ;)
Like XSleeper, I also am not particularly familiar with black windows. You probably can get black, or something similar, in aluminum and maybe fiberglass, but never vinyl. I agree that it would possibly melt and at the very least distort the vinyl if it was black.
Scott, looks like you have your work cut out for you, and after reading these three replies if you don't have a bunch of questions I will eat my keyboard!
Good luck!
XSleeper
09-01-05, 05:35 PM
I always enjoy reading Oberon's posts because he knows so much more about glass than I do. I always learn something from him. :thumbup:
Oberon
09-01-05, 05:50 PM
Thanks XSleeper, I consider that a great compliment. I really enjoy your posts as well, because while I know something of glass, when it comes the the elements of the sash and frame and especially installation, I always learn from your posts as well!
Concretemasonry
09-01-05, 07:24 PM
A comment on window installation -
I frequently get involved in water penetration, but avoid mold if that is possible. I also inspect homes for purchase and inspect new homes. My views are slanted because of the type of problems I see. It is amazing how many Tyvek wrapped vinyl sided homes less than 10 years old have moisture problems to the extent of being knocked down.
The biggest scew-up I see in construction is window installation. This, coupled with the insane idea that Tyvek makes everything "bullet-proof" lead the list and are frequently combined in the same problems.
Now, there are a few builders that are subbing out the windows and doors to subcontractors that employ only Certified Window Installers. I point this out an example of how bad the installation problem is. These are builders that choose to not have their own people do the work, but turn it over to a sub at a slightly higher cost.
I personally took the two day installation class and found it very interesting and because of what was brought out when a group of people doing the same thing taught to each other while following the manufacturer's general instuctions. The class runs about $400 and I think it is sponsored and supported by the window manufacturers.
If you are building. you may look into whether there are certified installers in your area.
Dick
I frequently get involved in water penetration, but avoid mold if that is possible. I also inspect homes for purchase and inspect new homes. My views are slanted because of the type of problems I see. It is amazing how many Tyvek wrapped vinyl sided homes less than 10 years old have moisture problems to the extent of being knocked down.
The biggest scew-up I see in construction is window installation. This, coupled with the insane idea that Tyvek makes everything "bullet-proof" lead the list and are frequently combined in the same problems.
Now, there are a few builders that are subbing out the windows and doors to subcontractors that employ only Certified Window Installers. I point this out an example of how bad the installation problem is. These are builders that choose to not have their own people do the work, but turn it over to a sub at a slightly higher cost.
I personally took the two day installation class and found it very interesting and because of what was brought out when a group of people doing the same thing taught to each other while following the manufacturer's general instuctions. The class runs about $400 and I think it is sponsored and supported by the window manufacturers.
If you are building. you may look into whether there are certified installers in your area.
Dick
Scott_Free
09-01-05, 08:26 PM
Thanks for the info, I was hoping to tap into a resource like you guys and I am glad I did. As I mentioned the house we are having built is going to be R2000 compliant and I am sure that will resrict what windows we are even allowed to have installed.
Now that I am more clear on the ratings and the actual effects the glass (each piece and side) has I can ask some better questions when we meet with the builders next week.
The black windows I had only assumed were vinyl, and from what you are saying they will most likely be either wood or fiberglass. I do not think we want the painted wood look so fiberglass would be our first choice.
I am being told that have black vs white (or perhaps 1-2 other standard colors) will be about 5-10% more in cost. I was ready for this as it is the usual with anything out of the ordinary.
We do live in Canada (the great white north) and our temperatures vary a great deal from summer (95 F) to winter (-55F with the wind chill). So as you can imagine energy efficieny is a top concern with me.
With this info you have provided I will be able to get more info and a closer decision to what we are going to have installed. At that point I will be back with another bevy of questions. I especially appreciate the points you all made about installation, I will have to ensure to ask questions in that area.
Thanks again.
Scott
Now that I am more clear on the ratings and the actual effects the glass (each piece and side) has I can ask some better questions when we meet with the builders next week.
The black windows I had only assumed were vinyl, and from what you are saying they will most likely be either wood or fiberglass. I do not think we want the painted wood look so fiberglass would be our first choice.
I am being told that have black vs white (or perhaps 1-2 other standard colors) will be about 5-10% more in cost. I was ready for this as it is the usual with anything out of the ordinary.
We do live in Canada (the great white north) and our temperatures vary a great deal from summer (95 F) to winter (-55F with the wind chill). So as you can imagine energy efficieny is a top concern with me.
With this info you have provided I will be able to get more info and a closer decision to what we are going to have installed. At that point I will be back with another bevy of questions. I especially appreciate the points you all made about installation, I will have to ensure to ask questions in that area.
Thanks again.
Scott
XSleeper
09-01-05, 08:54 PM
Just to clarify, you should be able to get black as a color choice with any "aluminum clad exterior / wood interior" wood window. When I referred to having the color painted any color, I was referring to the colors the aluminum cladding is finished in (painted). Sorry for the confusion, I don't always type what my brain is thinking. ;)