[lloyd99]

I have been thinking of getting window tint on my 2021 X7 M50i - partly to visually darken the windows and partly to help keep the vehicle cooler in the warmer summer months. I have seen a lot of posts about using Xpel, Llumar IRX, etc on the windows and moonroof to help address the lackluster cooling capabilities during the hot summer months.

This week, the temperature has gotten cooler here in Pittsburgh, PA. This afternoon, when I returned to my X7 after a lunch meeting, it was warmer in the vehicle (from the sun). It was nice to step into a vehicle that wasn't freezing cold - like it was outside. Then it hit me - Yikes - if I apply window tint to help prevent solar heat transmission during the hot summer months, I suppose it will also block it during the winter months (when I might actually want it). For those of you with tint who live in colder winter climates, can you confirm your X7 does not "warm up" via the sun due to the tint blocking of the sun in the colder winter months? And if so, do you miss that "benefit"? Thanks in advance!

[BMWMN1971]

My understanding is that window tinting will keep heat from going into the vehicle when it is too hot outside but will keep heat inside the vehicle when it is too cold outside. That’s what I know about office buildings so I assume it does the same in cars.

[BMW5and7]

You don't need feedback from others. This is physics and no-one can argue about the fact that the answer is yes... In winters, that car will not warm up as much as it would if it did not have tint.

Of course, with tint in winter, the car will not get warm as most of the IR will be reflected and won't get into your car cabin.

And, no, tint does NOT keep heat inside your car. The car does not have sun or solar rays leaving it that the tint can block it and keep it in. The car looses heat via conduction and convection through windows when cabin is hot, and the tint is way to thin and has ZERO impact on keeping the cabin heat inside the cabin. In summary, tint has negative benefits during winter, or at best, has no positive impact.

The only benefits of tint during winter:
1. Keeps blocking harmful UV rays.
2. It can reduce glare to some degree just like summer months.

Some installers "falsely" make claims that tint adds insulation. This is 100% wrong and misleading. Insulation is a function of thickness and thermal conductivity of the material. If one was to do the calculations, the added insulation of tint is literally not measurable and too small to even be calculated just because of how thin the tint is. The negative impacts of reflecting IR outweighs greatly the small negligible possibility the tint insulates the windows. The overall impact is negative as far as adding/retaining heat inside the car.

[blutob2]

Originally Posted by BMW5and7

You don't need feedback from others. This is physics and no-one can argue about the fact that the answer is yes... In winters, that car will not warm up as much as it would if it did not have tint.

Of course, with tint in winter, the car will not get warm as most of the IR will be reflected and won't get into your car cabin.

And, no, tint does NOT keep heat inside your car. The car does not have sun or solar rays leaving it that the tint can block it and keep it in. The car looses heat via conduction and convection through windows when cabin is hot, and the tint is way to thin and has ZERO impact on keeping the cabin heat inside the cabin. In summary, tint has negative benefits during winter, or at best, has no positive impact.

The only benefits of tint during winter:
1. Keeps blocking harmful UV rays.
2. It can reduce glare to some degree just like summer months.

Some installers "falsely" make claims that tint adds insulation. This is 100% wrong and misleading. Insulation is a function of thickness and thermal conductivity of the material. If one was to do the calculations, the added insulation of tint is literally not measurable and too small to even be calculated just because of how thin the tint is. The negative impacts of reflecting IR outweighs greatly the small negligible possibility the tint insulates the windows. The overall impact is negative as far as adding/retaining heat inside the car.

Yup agreed. Just like tinting my home windows. I benefited during the summer but lost all the natural heat during the winter. It made a huge difference but I was more worried about reducing the heat in the summer than winter. Anyways, same effect in the cars.

[streborx]

I have a Weathertech sunshade windshield screen for my G550 (there isn't one available for the X7). This sun shield is highly reflective silver on one side and black on the other side. According to Weathertech's claims, the reflective side drops the dash temperature to 110F from 170F without it, while the absorbing side increases the dash temperature to 50F from 32F without it. I haven't done my own testing, but it does have some benefit in heat transfer control. The shield is about 1/4" thick so maybe there's a slight insulative benefit also. But the above analysis is correct -- heat gain is radiative and heat loss is conductive.

[Saejin]

I’ve spent two winters in CO with our 2023 X7 that has tint on all glass, including sunroof.

And I’ve spent two previous winters in CO with our 2022 X7 that had tint on all glass except for the sunroof.

As I understand it, experienced it, and based on the previous comments, the tint on the X7 will prevent it from warming up during the winter to the same levels as an X7 without tint.

However, this is so negligible and the benefit of tint during the summer months outweighs the negative impacts in the winter.

I almost always remote start my X7 especially when the temps are at their extremes hot and cold. This alone negates the impact tint has in the winter. I always step into a warm X7.

[BMW5and7]

Originally Posted by Saejin

As I understand it, experienced it, and based on the previous comments, the tint on the X7 will prevent it from warming up during the winter to the same levels as an X7 without tint.

However, this is so negligible and the benefit of tint during the summer months outweighs the negative impacts in the winter.

This doesn’t make sense, at least based no physics.

During summer: Solar irradiance on a clear day, around noon, is ~1000 W/m2. Around 55% of this energy is already heat (infrared). The reason that tint works is because it blocks 70-98% of the energy that would have passed through the factory windows. The reason tint works is because a good portion of that is NOT filtered by naked factory windows and tint is blocking it. I think we all agree up to this point

During Winter, the same is true. The difference is that during harsh winter sun irradiance is about 300-500 W/m2 under the same conditions above. Still 55% of that is heat and normally part of it would pass through your windows causing your cabin to gain some thermal energy (heat) that you really need in winter. With tint, you no long allow majority of it to pass. Hence, it’s not negligible at all. In fact, it about 40% of that energy that your cabin gains during summer. The overall impact of tint in winter may not be as dramatic as a hot cabin in summer when there is no tint, but you can’t say it’s negligible. Two identical cars would have measurable and noticeable difference in their cabin temperature in winter if one has tint and one doesn’t and both parked somewhere on a clear but very cold day. The only time when tint has no negative impact is when it’s too cloudy during a winter day.

I agree though that the negative impact during winter is not even close to the benefits during Summer. For those driving EVs though, tint during winter during a road trip would cause the car to consume a lot more energy for heating than no tint.

[BMWMN1971]

Originally Posted by BMW5and7

This doesn’t make sense, at least based no physics.

During summer: Solar irradiance on a clear day, around noon, is ~1000 W/m2. Around 55% of this energy is already heat (infrared). The reason that tint works is because it blocks 70-98% of the energy that would have passed through the factory windows. The reason tint works is because a good portion of that is NOT filtered by naked factory windows and tint is blocking it. I think we all agree up to this point

During Winter, the same is true. The difference is that during harsh winter sun irradiance is about 300-500 W/m2 under the same conditions above. Still 55% of that is heat and normally part of it would pass through your windows causing your cabin to gain some thermal energy (heat) that you really need in winter. With tint, you no long allow majority of it to pass. Hence, it’s not negligible at all. In fact, it about 40% of that energy that your cabin gains during summer. The overall impact of tint in winter may not be as dramatic as a hot cabin in summer when there is no tint, but you can’t say it’s negligible. Two identical cars would have measurable and noticeable difference in their cabin temperature in winter if one has tint and one doesn’t and both parked somewhere on a clear but very cold day. The only time when tint has no negative impact is when it’s too cloudy during a winter day.

I agree though that the negative impact during winter is not even close to the benefits during Summer. For those driving EVs though, tint during winter during a road trip would cause the car to consume a lot more energy for heating than no tint.

You should probably call 3M and tell them their claim on this product is wrong according to you.

“3M™ Low-E Window Films help provide increased insulation performance by retaining heat during the winter and cool air during the summer, so you can increase tenant comfort year round.”

https://www.3m.com/3M/en_US/building-window-solutions-us/solutions/comfort/#:~:text=3M™%20Low%2DE%20Window,increase%20tenant% 20comfort%20year%20round.

[blutob2]

Originally Posted by BMWMN1971

You should probably call 3M and tell them their claim on this product is wrong according to you.

“3M™ Low-E Window Films help provide increased insulation performance by retaining heat during the winter and cool air during the summer, so you can increase tenant comfort year round.”

https://www.3m.com/3M/en_US/building...20year%20round.

But doesn't it already have to be warm for it to retain the heat...You're arguing insulation which is different from tint blocking UV and the natural heat.

[BMWMN1971]

Originally Posted by blutob2

But doesn't it already have to be warm for it to retain the heat...You're arguing insulation which is different from tint blocking UV and the natural heat.

I am saying that if you drive the car in the winter and have the indoor temperature let’s say at 72F, having the correct window tint will allow you to keep that heat that is already inside the cabin inside and not lose it quickly. I fully understand that if you have a tint that blocks heat from coming in it will still do the same in the winter but if the cabin is warm the tint will also help to keep that heat in.

[BMW5and7]

Originally Posted by BMWMN1971

You should probably call 3M and tell them their claim on this product is wrong according to you.

“3M™ Low-E Window Films help provide increased insulation performance by retaining heat during the winter and cool air during the summer, so you can increase tenant comfort year round.”

https://www.3m.com/3M/en_US/building...20year%20round.

Don’t worry, I don’t need to call them. I have first-hand experience with the R&D cycle of this product. The claim is true and it doesn’t interfere with what I said. That’s the problem when you only read what marketing docs or companies write, versus knowing exactly how it works and all the details behind it. The claim is true, almost any layer or material helps to insulate one controlled volume from another; so the claim is true, the film does help to retain heat. However, by how much? Let’s say by a value of X. On the other hand, how much heat is blocked from the outside? It’s an order of magnitude higher than X : ). So, in total, the impact is negative. Does the film help retain heat inside? YES!. Does the film also blocks more heat to come from outside into the cabin? Yes. The different is all what matters. Listen, am here trying to help, I have no personal interest in any of that. Am here to help.

[BMW5and7]

Originally Posted by blutob2

But doesn't it already have to be warm for it to retain the heat...You're arguing insulation which is different from tint blocking UV and the natural heat.

Exactly. The problem is, people forget that almost any material on this plant is basically an insulation. But how good is that material? It is only as good by how thick that material is even if it’s the best insulated on the plant. The claim is true, but what is it’s insulation value? Does it retain 0.001% of heat inside? Yes for sure and hence the claim is right. But at the same time, people forget that it rejects nearly 95% of the heat coming form outside. Great… retains “X” kWh of thermal energy inside, but then blocks an additional thousands of “X” kWh that would have passed to the cabin from outside. It’s like, oh, but this product, it saves you $10 per year, but it will cost you $100 per year in maintenance. That is exactly what tint does during winter if you just convert $ to kWh or thermal energy for this hypothetical example. It blocks waaay more thermal energy than the energy it retains inside.

[blutob2]

Originally Posted by BMWMN1971

I am saying that if you drive the car in the winter and have the indoor temperature let’s say at 72F, having the correct window tint will allow you to keep that heat that is already inside the cabin inside and not lose it quickly. I fully understand that if you have a tint that blocks heat from coming in it will still do the same in the winter but if the cabin is warm the tint will also help to keep that heat in.

Yup but the OP only mentioned it parked. They were wondering in the winter months, if they went to the car then would it be warmer inside. I'm all about answering the question...because I can care less when the car is actually running and providing heating or cooling

But my next trip to ND, I'll test setting mine at 72, then turning it off but I can already guarantee you from previous experience, it's a pretty rapid heat loss

[blutob2]

Originally Posted by BMW5and7

Exactly. The problem is, people forget that almost any material on this plant is basically an insulation. But how good is that material? It is only as good by how thick that material is even if it’s the best insulated on the plant. The claim is true, but what is it’s insulation value? Does it retain 0.001% of heat inside? Yes for sure and hence the claim is right. But at the same time, people forget that it rejects nearly 95% of the heat coming form outside. Great… retains “X” kWh of thermal energy inside, but then blocks an additional thousands of “X” kWh that would have passed to the cabin from outside. It’s like, oh, but this product, it saves you $10 per year, but it will cost you $100 per year in maintenance. That is exactly what tint does during winter if you just convert $ to kWh or thermal energy for this hypothetical example. It blocks waaay more thermal energy than the energy it retains inside.

Yup and once again, I point to my home window tint post...I would rather have tint and benefit during the summer months because electric AC is WAY more expensive than gas heating in my area.

[BMW5and7]

Originally Posted by BMWMN1971

I am saying that if you drive the car in the winter and have the indoor temperature let’s say at 72F, having the correct window tint will allow you to keep that heat that is already inside the cabin inside and not lose it quickly. I fully understand that if you have a tint that blocks heat from coming in it will still do the same in the winter but if the cabin is warm the tint will also help to keep that heat in.

True but you are only seeing part of it. It helps to retain some of the heat, but it blocks an order of magnitude of that heat to pass through windows that would have otherwise helped to add even more heat to the cabin. Hence, the overall impact is negative. What you said only works (and is barely measurable) at night or very cloudy days (and even then, this benefit is not even measurable). If you understand how insulation materials work, you would know that a material that is as thin as tint has in theory and mathematically a negligible heat retention value. In a court, you can win a case claiming a fraction of a kWh was retained though. But, it does not change the fact that is has no real impact whatsoever, and then during the day when sun is up, the overall impact is negative when the positive thermal energy that would have passed through the windows is much greater (which now is blocked with tint).

I myself have tint, and I live in an area that temperature can reach -20 degF. I am not arguing about how great tint is here, and the discussion above is silly, but it’s the fact that we are arguing about physics 101 is what triggered me to respond here.

[XM Label]

I got tint because I like the way it looks and it prevents people from looking in at a stop light or in a traffic jam. I don’t worry about temps in summer or winter. Temps can be controlled using preconditioning function which can be activated through app on phone very easily!!!!!!!!

[lloyd99]

Thank you everyone for your feedback and thoughts, I appreciate it!

[BMW5and7]

Originally Posted by BMWXMBlack

I got tint because I like the way it looks and it prevents people from looking in at a stop light or in a traffic jam. I don’t worry about temps in summer or winter. Temps can be controlled using preconditioning function which can be activated through app on phone very easily!!!!!!!!

It’s great to see how different people appreciate tint based on different priorities. In my case, i.e., I got it to fully block UV and also sun rays from hitting my face, arms, etc. I also chose a very light color as all I wanted is to block the harmful sun rays that causes damage as well as heat. I never cared about the cabin temperature… I just never like the feeling of the sun hitting me or family on road trips. A good tint does a great job in only allowing the “light” component to pass through and blocks nearly everything else.

[XM Label]

Originally Posted by BMW5and7

It’s great to see how different people appreciate tint based on different priorities. In my case, i.e., I got it to fully block UV and also sun rays from hitting my face, arms, etc. I also chose a very light color as all I wanted is to block the harmful sun rays that causes damage as well as heat. I never cared about the cabin temperature… I just never like the feeling of the sun hitting me or family on road trips. A good tint does a great job in only allowing the “light” component to pass through and blocks nearly everything else.

This is also very important!

[Saejin]

Originally Posted by lloyd99

Thank you everyone for your feedback and thoughts, I appreciate it!

nice try...even though we answered your question, we're going to keep debating and discussing this to the end of days.

[lloyd99]

Originally Posted by Saejin

nice try...even though we answered your question, we're going to keep debating and discussing this to the end of days.

Saejin HaHa. Yes, I did get the answer to my question. I didn't mean to start a big debate! Like BMW5and7 said, it was interesting to see how different people appreciate tint based on different priorities. It's been chilly here in Pittsburgh the past few days, and there was something nice about walking from the cold temp, entering my X7, and having it already (naturally) warm without any thoughts of having to precondition in advance. So I guess tint is three steps forward (darker window look, easier to cool in the hot summer, and UV ray protection) and just one step backwards (loss of natural warmth in the winter).

[Saejin]

Originally Posted by lloyd99

Saejin HaHa. Yes, I did get the answer to my question. I didn't mean to start a big debate! Like BMW5and7 said, it was interesting to see how different people appreciate tint based on different priorities. It's been chilly here in Pittsburgh the past few days, and there was something nice about walking from the cold temp, entering my X7, and having it already (naturally) warm without any thoughts of having to precondition in advance. So I guess tint is three steps forward (darker window look, easier to cool in the hot summer, and UV ray protection) and just one step backwards (loss of natural warmth in the winter).

Got another option for you that I just thought of. I tinted my sunroof as well, so it blocks out alot of that warmth you would get.

So, if you just tinted your side glass and then in the winter, left the sunroof shade open, it might be enough to warm things up.