Best Tint to Keep Cool in Home

[Guest scottym]

Scotty,

Heat Reduction and Solar Energy Reduction are two totally different things. You can have a flame that is the same temperature as a forest fire, however, each is emitting far different amounts of energy. Window Films do not cool to a certain temperature, but rather, they reject a certain amount of solar energy.

Solar Heat Gain Coefficient or SHGC is an NFRC recognized measurment in the glass industry. The formula for the Window Film measurement "Total Solar Energy Rejected" is similar in that you can arrive at the same measurement with the following formula. "1-TSER=SHGC"

Most parameter sheets available to the general public will be film specs based on 1/8" clear monlithic glass.

There are a lot of Bronze Llumar Films, I picked twwo. Here is the performance data for glass that is similar to your windows:

Llumar DR 35

SHGC= .51

TSER= 49%

SC= .59

Llumar N1035 Bronze

SHGC= .45

TSER= 55%

SC= .52

vclimber,

I like your analogy it's helpful considering I was only recently introduced to window films. Like you say window films don't cool. A more appropriate description would be a filter (reflect or absorb) the energy coming through my window. My AC is responsible for removing the remaingin energy that results in summertime heat. My comment was really criticizing vendors that provide VLT and TSER without the SC figure.

With respect to vendors quoting 1/8" single pane glass and occasionally generic dual-pane is this a sufficient figure of merit to compare film performance and can this spec be extrapolated to other types of glass a customer may be using?

In other words, is it fair to compare the 1/8" single pane glass performance of vendor A to vendor B and conclude that since vendor A had better 1/8" single pane specs we can use these specs to conclude 1/4" and dual pane glass of varying size will perform "comparably". Comparably meaning vendor A not only performs better then B for different glass types, it also performs predictably without knowing more than the 1/8" and/or generic dual-pane spec?

Lastly, I was comparing the Lumar N-10XXB series to the 3M NV series using numbers off the 3M sample card. I know they are different types of film but the 3M rep made some impressive claims regarding the NV series heat reduction capability when compared using a BTU meter.

I came up with a different number than you for SHGC since I interpolated between the 1/4" and 1/8" dual pane clear figures to arrive at the figure I use for my 3/8" thick windows.

3M Scotchtint NightVision

NV-45 NV-35 NV-25

VLT 22% 31% 40%

SHGC 38% 28% 17%

Llumar (1/8" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 35% 50%

SHGC 55% 42% 28%

Llumar (1/4" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SHGC 47% 36% 23%

Scott's Windows are Andersen dual-pane clear casement, Argon filled, organically sealed, 3/8" total thickness. Approximately 3/16" per pane since the gas filled gap is all but negligible. Since this vendor was kind enough to provide the 1/8" and 1/4" numbers I attempted to work out a reasonable estimate of how my glass should perform.

Llumar (3/8" Dual-Pane Clear*)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SHGC 51% 39% 26%

[*Calculated]

In short, I came up with SHGC=.39 for the N-1035B. Where did your SHGC=.45 number come from?

Regards,

ScottyM

[Guest vclimber]

With respect to vendors quoting 1/8" single pane glass and occasionally generic dual-pane is this a sufficient figure of merit to compare film performance and can this spec be extrapolated to other types of glass a customer may be using?

Relatively so. We use it as a base standard of comparison since all parameter sheets start here. The numbers will probably vary slightly depending on the type of film as the glass type changes.

In other words, is it fair to compare the 1/8" single pane glass performance of vendor A to vendor B and conclude that since vendor A had better 1/8" single pane specs we can use these specs to conclude 1/4" and dual pane glass of varying size will perform "comparably". Comparably meaning vendor A not only performs better then B for different glass types, it also performs predictably without knowing more than the 1/8" and/or generic dual-pane spec?

Good question. Not necessarily. The 1st thing that comes to mind are low E2 windows. I would have to ressearch but I think you will see a lack of predictability itwh this particular glass. The best thing to do is requests parameters based on your glass type (or as close as you can get to it), most manufacturers have that infrmation and can make it available to their dealers.

Lastly, I was comparing the Lumar N-10XXB series to the 3M NV series using numbers off the 3M sample card. I know they are different types of film but the 3M rep made some impressive claims regarding the NV series heat reduction capability when compared using a BTU meter.

Scotty, keep in mind that performance sometimes needs to be tempered with what is aesthetically acceptable for the given application. In other words, the highest energy rejecting films are not necessarily the best choice for say a residential application where reflective films violate local CC&R's. Or the optics of the higher performing film may simply look terrible compared to others films. Keep that in mind too.

I came up with a different number than you for SHGC since I interpolated between the 1/4" and 1/8" dual pane clear figures to arrive at the figure I use for my 3/8" thick windows.

3M Scotchtint NightVision

NV-45 NV-35 NV-25

VLT 22% 31% 40%

SHGC 38% 28% 17%

Llumar (1/8" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 35% 50%

SHGC 55% 42% 28%

Llumar (1/4" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SHGC 47% 36% 23%

Scott's Windows are Andersen dual-pane clear casement, Argon filled, organically sealed, 3/8" total thickness. Approximately 3/16" per pane since the gas filled gap is all but negligible. Since this vendor was kind enough to provide the 1/8" and 1/4" numbers I attempted to work out a reasonable estimate of how my glass should perform.

Llumar (3/8" Dual-Pane Clear*)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SHGC 51% 39% 26%

[*Calculated]

In short, I came up with SHGC=.39 for the N-1035B. Where did your SHGC=.45 number come from?

Regards,

ScottyM

I used Llumar's Performance chart for Dual Pane 1/4" clear glass. That was the closest I could find to your situation.

Here it is again:

Llumar N1035

TSER 55%

SHGC .45

SC .52

Llumar N1020

TSER 63%

SHGC .37

SC .43

3M NV-25 (Double Pane Clear, glass thickness unspecified)

TSER 57%

SHGC .43

SC .50

3M NV-35 (Double Pane Clear, glass thickness unspecified)

TSER 50%

SHGC .50

SC .58

Looks like the Llumar wins.

[Guest vclimber]

Lastly, I was comparing the Lumar N-10XXB series to the 3M NV series using numbers off the 3M sample card. I know they are different types of film but the 3M rep made some impressive claims regarding the NV series heat reduction capability when compared using a BTU meter.

Scotty,

Be careful. A BTU meter only tells 53% of the whole story...

Solar Energy:

3%UV

53% Infrared

44% Visable Light

BTU meters measure a small band of the near infrared (NIR) radiation that makes up a small part of the 53% of the solar energy that reaches earth. So when you see the needle drop on a BTU meter, you are seeing a narrow part of the NIR being filtered, not the whole TSER figure.

[Guest scottym]

Scotty,

Heat Reduction and Solar Energy Reduction are two totally different things. You can have a flame that is the same temperature as a forest fire, however, each is emitting far different amounts of energy. Window Films do not cool to a certain temperature, but rather, they reject a certain amount of solar energy.

Solar Heat Gain Coefficient or SHGC is an NFRC recognized measurment in the glass industry. The formula for the Window Film measurement "Total Solar Energy Rejected" is similar in that you can arrive at the same measurement with the following formula. "1-TSER=SHGC"

Most parameter sheets available to the general public will be film specs based on 1/8" clear monlithic glass.

There are a lot of Bronze Llumar Films, I picked twwo. Here is the performance data for glass that is similar to your windows:

Llumar N1035 Bronze

SHGC= .45

TSER= 55%

SC= .52

vclimber,

EDIT: I like your analogy it's helpful considering I was only recently introduced to window films. I agree that heat reduction and TSER are different. And therein lies the problem. Upon reflection my comments are driven by the confusion caused by quoting numbers like TSER and expecting a high correlation with heat reduction. This seems to be how the industry presents their films.

I understand a window window film does not cool. A more appropriate analogy would be a filter (energy can be reflected, absorbed or transmitted). My AC is responsible for removing the heat coming through my windows.

With respect to vendors quoting 1/8" single pane glass and occasionally generic dual-pane is this a sufficient figure of merit to compare film performance and can this spec be extrapolated to other types of glass a customer may be using? I believe the answer is yes if your not interested in heat reduction performance.

In other words, is it fair to compare the 1/8" single pane glass performance of vendor A to vendor B and conclude that since vendor A had better 1/8" single pane specs we can use these specs to conclude 1/4" and dual pane glass of varying size will perform "comparably". Comparably meaning vendor A not only performs better then B for different glass types, it also performs predictably without knowing more than the 1/8" and/or generic dual-pane spec?

Lastly, I was comparing the Lumar N-10XXB series to the 3M NV series using numbers off the 3M sample card. I know they are different types of film but the 3M rep made some impressive claims regarding the NV series heat reduction capability when compared using a BTU meter.

EDIT: I came up with a dramatically different heat reduction number based on data provided by Llumar for different types of glass. I interpolated between the 1/4" and 1/8" dual pane clear figures to arrive at the figure I use to estimate heat reduction for my 3/8" thick windows. It appears heat reduction varies widely across different glass given the same film.

EDIT: The spec I misunderstood to be SHGC is in fact Summertime Solar Heat Gain Reduction (SSHGR) as defined by Llumar which may be a measured versus a calculated value (dunno?).

3M Scotchtint NightVision

NV-45 NV-35 NV-25

VLT 22% 31% 40%

SHGC 38% 28% 17%

Llumar (1/8" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 35% 50%

SSHGR 55% 42% 28%

SHGC 34% 44% 54%

Llumar (1/4" Dual-Pane Clear)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SSHGR 47% 36% 23%

SHGC 37% 45% 53%

Scott's Windows are Andersen dual-pane clear casement, Argon filled, organically sealed, 3/8" total thickness. Approximately 3/16" per pane since the gas filled gap is all but negligible. Since this vendor was kind enough to provide the 1/8" and 1/4" numbers I attempted to work out a reasonable estimate of how my glass should perform.

Llumar (3/8" Dual-Pane Clear*)

N-1020B N-1035B N-1050B

VLT 19% 34% 48%

SSHGR 51% 39% 26%

SHGC 36% 45% 53%

[*Calculated]

In short, I came up with SSHGR=.39 for the N-1035B.

Regards,

ScottyM

I noticed the SHGC/TSER values are not much different for the two thicknesses of dual pane glass. If TSER and VLT were my figures of merit to judge films then I would say the window thickness for dual-pane does not matter much. However, like I said earlier, TSER is not useful to me since it includes all wavelengths of light (meaning those which do not result in heat but account for energy). Llumar provides the "Summer Solar Heat Gain Reduction" number which I don't know if is standardized by the NFRC. This seems to be a good figure of merit to compare films where heat reduction and VLT are important to a customer.

I though maybe specs like luminous efficacy and shade coefficient may also be useful for shopping film based on my needs. The SC seems to be nothing more than the SHGC(tinted glass)/SHGC(clear glass) and may give an indication of shade percentage of the tint and allows us to factor out effects of the natural glass tint-guess this could be useful for comparing tints. The Luminous Efficacy seems to be VLT/SC or a measure of the films attenuation of transmitted light (without being applied to glass). It appears that SC and luminous efficacy are useful when comparing films but not useful for shopping for the best heat reduction film.

If I understand these figures, (and I'm sure I've misunderstood some), the only meaningful measure of heat reduction performance as it applies to my windows is through vendor provided data like Llumars SSHGR.

If only their was a way to calculate heat reduction (not TSER) so films can be compared on the basis of how they will perform in my home instead of how they will perform compared to each other????

End of Rant.

Scott

[Guest vclimber]

Here is your formula.

Solar Heat Reduction=(SHGC of Clear Glass-SHGC of glass with film applied)/SHGC of Clear Glass

Example:

Your clear glass hass a heat gain of 85% SHGC=.85

Filmed Glass is SHGC= .45

(.85-.45)/.85=47% Solar Heat Reduction or the percent by which incoming solar heat energy is reduced by the addition of a filtering material.

[Guest cactustint]

If only their was a way to calculate heat reduction (not TSER) so films can be compared on the basis of how they will perform in my home instead of how they will perform compared to each other????

End of Rant.

Scott

only a thermometer will tell

shgc changes .01 per 1/8th inch of glass thckness for dual clear

[Guest vclimber]

shgc changes .01 per 1/8th inch of glass thckness for dual clear

Good to know, thanks cactus.

[Guest scottym]

Lastly, I was comparing the Lumar N-10XXB series to the 3M NV series using numbers off the 3M sample card. I know they are different types of film but the 3M rep made some impressive claims regarding the NV series heat reduction capability when compared using a BTU meter.

Scotty,

Be careful. A BTU meter only tells 53% of the whole story...

Solar Energy:

3%UV

53% Infrared

44% Visable Light

BTU meters measure a small band of the near infrared (NIR) radiation that makes up a small part of the 53% of the solar energy that reaches earth. So when you see the needle drop on a BTU meter, you are seeing a narrow part of the NIR being filtered, not the whole TSER figure.

I've also read some other posts that suggest that BTU meters may be nearly as spectrally selective as the film being measured

But you do touch upon the issue most important to me--my electric bill. It's those Infrared wavelengths that contain energy that is converted to heat. Why should I worry about the other 47% if it's not heating my house?

Don't hesitate to club me over the head if I'm off base, it helps me learn.

[Guest cactustint]

really nutting

I just compair 1/8 glass and 1/4 glass on chart

light = heat too

btu meter only sees to 1050 nanos

[Guest scottym]

light = heat too

btu meter only sees to 1050 nanos

I take it you mean some of the visible light spectrum betweeen IR and UV contains significant energy and the meter is limited to 1050 nm. Yeah, I was missing part of vclimber's point about 44% of energy being within visible spectrum. Toss the BTU meter. The question that interests me is how much of that 44% is converted to heat.

Still I can't accept that TSER is the right spec to compare films if your interest is keeping your home cool since 100% of solar energy that crosses my window sill cannot be converted to heat.