How well does the glass roof reflect heat?

[sleepydoc]

I’ve posted this before but it’s worth repeating. The MY sunroof is very good at blocking IR radiation but one needs to realize there are 2 ways to block radiation: reflection and absorption. The MY sunroof seems to absorb quite a bit of the IR radiation which is significant because it causes the glass to heat up and essentially become a radiator. The best way to prove this to yourself is to put your hand on the glass on a sunny day.

You can mitigate this by either putting a film that helps reflect IR radiation or a sunscreen on the inside. The screen will block the radiant effect of the glass as well as create an insulating layer of air between the glass and the screen.

The sunroof makes a wonderfully open interior but even with coatings glass is a horrible insulator. This is why most companies provide some sort of shade or screen for sunroofs in cars.

 

[RPM51]

It's been 100-109 here for weeks. Zero issues with feeling any heat from the glass roof on our new MYP. Just drove 1700 miles across the southern US in full sun (100* plus). No issues with heat. The windshield driving into the afternoon sun is a different story. That's where the heat is coming from on ours. You can tint the windshield to help, but we get so many rock breakages here with all the construction and cement and gravel trucks, it would just be a waste of $250 when the windshield inevitably gets broken and needs to be replaced (and re-tinted). Not to mention the polarized glasses issue is annoying.

We only have the front two windows ceramic tinted 35%. Completely fixed that heat issue.

104* yesterday, full sun driving for 6+ hours. Climate was set on 71* (auto) and it used 5 fan speed all day with 4 of us in the car. Worked fine for us. No "need" to spend a ton of money tinting all the other stuff that is already tinted unless you just want it even darker than it already is.

 

[JDEWD250]

I still don't get it. Does the car detect and wake up to cool the car if it gets above a certain temperature?

PS: I don't have MYLR yet which is why I am trying to understand this thread.

We have the same build, but I have tow package too.

The ac will come on at a specified (by you) temp and keep the cabin from overheating, unfortunately I do not have mine yet, but I do not believe I will use it all the time, perhaps a half hour before I intend to leave I will set it for a temperature of my liking so the car is ready to go when I am

 

[boulder.dude]

Roof heating up is mainly a problem when parked in direct sun on a hot day. Painful to the touch on the outside or the inside. When driving, the wind (even on a hot day) cools the roof down.

On my next summer road trip I’m contemplating bringing a lightweight white comforter to throw on the roof for the SC stops!

 

[Tonedog77]

extremely well

 

[Megabrode]

I added a front and rear mesh shade to my Model 3 to cut down on the heat generated into the cabin. Inexpensive modification I found on Amazon.
Works well, don't even notice it is there.

A roof mesh screen also works for me. Without it, my bald pate defintiely feels the summer heat. Compared to tint, the advantages of mesh are cost ($80 @ Amazon) and you can remove it in cool weather. Folded, it fits perfectly in the hide-away shelf in the trunk. It's a tad tricky to install the first time, easy after that. At some point I may get a screen for the hatch window.

 

[cbdream99]

I am in Texas, it works fine, I don’t feel the heat on my bald head, of course if you touch the roof, you will feel the heat. After I tinted the windshield, I don’t feel I need more tint on the glass roof

 

[RPM51]

I am in Texas, it works fine, I don’t feel the heat on my bald head, of course if you touch the roof, you will feel the heat. After I tinted the windshield, I don’t feel I need more tint on the glass roof

Same. I don’t understand why people are touching the roof anyway. It’s 103 full sun here right now. 6’4” and I don’t feel ANY roof heat sitting in the car. None. However, if you put your hand in front of the untinted windshield you can feel heat coming in.

 

[Madmacs]

I’m 6’5” and the roof gets HOT and my head starts sweating. Not as bad as the windshield, but I’m definitely putting some ceramic light tint on the roof to keep the sun from baking my brains while I drive.

 

[sleepydoc]

A roof mesh screen also works for me. Without it, my bald pate defintiely feels the summer heat. Compared to tint, the advantages of mesh are cost ($80 @ Amazon) and you can remove it in cool weather. Folded, it fits perfectly in the hide-away shelf in the trunk. It's a tad tricky to install the first time, easy after that. At some point I may get a screen for the hatch window.

The mesh actually provides some benefit in cold weather, too. You don’t notice it as much but you’re losing heat through the glass, making the heat pump work harder to heat the cabin.

Same. I don’t understand why people are touching the roof anyway. It’s 103 full sun here right now. 6’4” and I don’t feel ANY roof heat sitting in the car. None. However, if you put your hand in front of the untinted windshield you can feel heat coming in.

The significance is that the hot glass contributes to heating up the air in the cabin making the A/C work harder.

 

[Megabrode]

Good point about a mesh roof shade conserving heat in the winter. That said, I'm willing to sacrifice a little range for the increased light and sense of space you get from the bare roof.

 

[mstatkus]

I was in 106 degrees in Phoenix in a M3 rented on Turo and it did amazing.
My Y has been fine but it’s only seen about 98. Being able to tap on climate before we jump into the car was great specially in AZ haha.

 

[Corndart]

Stock MYP, no additional tint/film on any glass in the car. I'm 6'2" and drove in during the hottest part of the day , 10:30am -> 4PM, in 95-104f heat yesterday, temperature set to 72f. No issues with radiant heat coming from the roof, sides or front glass, aircon kept the cabin nice and cool. Whatever Tesla is doing to reject heat and IR seems to work just fine without needing additional help.

 

[RPM51]

I guess they updated the coating or something because some of the comments about sweating and baking heads just don't make any sense for my car. My MYP is brand new and built June 2022, you can look directly at the overhead sun through it (I can’t do this with my sunglasses), and no perceptible heat comes through while sitting or driving. Because of this topic, I went out and felt the metal clip on my garage door opener that is exposed to the sun about 1.5” directly under the glass. It was perfectly cool to the touch at 105 outside temperature (with sunlight directly on it). The black headrests felt no warmer than the shaded portions of the seat. The interior roof glass was barely warm to the touch (car sitting in direct sun for an hour). My last cars sunroof would cause the black leather headrests and steering wheel to get super hot and it was annoying without closing the shade. My new MYP is not doing this at all.

From the exterior you cannot see through the rear hatch or roof on my car. It is 100% completely blacked out. I parked next to a model 3 and noticed mine was definitely darker. From reading posts complaining about this issue before I purchased my car I thought I would need a roof sunshade since I have two little kids riding in the back every day. I even had one in my amazon cart ready to purchase. Now, after owning the car in extremely hot temperatures and full sun for the past month. 100-110 degrees everyday. I can't imagine needing to add more roof tint than what it came with or needing any sort of shade cover. AC typically runs auto on only 5-6 in 100+ weather. My prior car only a couple years old was struggling on max ac in these temps with no full glass roof.

I would suggest anyone buying a brand new one to see for themselves. It is a non-issue for us in extreme heat (with kids in carseats staring out of the roof every day). The factory coating is excellent on ours.

The only addition to our car is 35% ceramic xpel prime xr black on the front two door windows since they were un-tinted. This completely cut out the heat on my left arm while driving.

 

[Corndart]

I guess they updated the coating or something because some of the comments about sweating and baking heads just don't make any sense for my car. My MYP is brand new and built June 2022, you can look directly at the overhead sun through it (I can’t do this with my sunglasses), and no perceptible heat comes through while sitting or driving. Because of this topic, I went out and felt the metal clip on my garage door opener that is exposed to the sun about 1.5” directly under the glass. It was perfectly cool to the touch at 105 outside temperature (with sunlight directly on it). The black headrests felt no warmer than the shaded portions of the seat. The interior roof glass was barely warm to the touch (car sitting in direct sun for an hour). My last cars sunroof would cause the black leather headrests and steering wheel to get super hot and it was annoying without closing the shade. My new MYP is not doing this at all.

From the exterior you cannot see through the rear hatch or roof on my car. It is 100% completely blacked out. I parked next to a model 3 and noticed mine was definitely darker. From reading posts complaining about this issue before I purchased my car I thought I would need a roof sunshade since I have two little kids riding in the back every day. I even had one in my amazon cart ready to purchase. Now, after owning the car in extremely hot temperatures and full sun for the past month. 100-110 degrees everyday. I can't imagine needing to add more roof tint than what it came with or needing any sort of shade cover. AC typically runs auto on only 5-6 in 100+ weather. My prior car only a couple years old was struggling on max ac in these temps with no full glass roof.

I would suggest anyone buying a brand new one to see for themselves. It is a non-issue for us in extreme heat (with kids in carseats staring out of the roof every day). The factory coating is excellent on ours.

@boulder.dude also had a good point, while moving, it's effectively a non-issue IME. Any vehicle left in the sun will heat up quickly, pre-conditioning the interior temps is the mitigation. Same experience with AC as you @RPM51 , fan level was moderate and able to keep up with interior heat while driving. While parked, the fan notched up a little but wasn't "full tilt" either.

Its possible due to Tesla's "running change" philosophy something is different between earlier MY's and current.

 

[Daniel L]

I’ve posted this before but it’s worth repeating. The MY sunroof is very good at blocking IR radiation but one needs to realize there are 2 ways to block radiation: reflection and absorption. The MY sunroof seems to absorb quite a bit of the IR radiation which is significant because it causes the glass to heat up and essentially become a radiator. The best way to prove this to yourself is to put your hand on the glass on a sunny day.

You can mitigate this by either putting a film that helps reflect IR radiation or a sunscreen on the inside. The screen will block the radiant effect of the glass as well as create an insulating layer of air between the glass and the screen.

The sunroof makes a wonderfully open interior but even with coatings glass is a horrible insulator. This is why most companies provide some sort of shade or screen for sunroofs in cars.

Agree with this although I gave up on the roof shade recently - it keeps the car 5 degrees cooler (135 instead of 140) on a hot day and prevents my head from feeling slightly warm for the first two minutes of driving but it's ugly and saggy.

 

[Reggae_Jesus]

while I work my car sits in the parking lot with no shade. I got the sun shade with the blackout screen and all my windows ceramic tint as dark as they let me. When I get to my car around 3 in the evening it's warm at the most.

 

[Tman458]

I have tint and clear UV film on the windshield. 100 plus outside, warm but tolerable inside. The windshield film made the biggest impact. Stock roof glass

 

[Curious Nomad]

Regarding the Cabin Overheat Protection I would suggerst using it

I truly don't understand why you guys want to have ur AC on to keep cabin below a certain temperature when you are not even in the car. I am sure I am missing something when reading this thread.

I mean when you guys had ICE cars did you leave your car running all day while you were in the office.

Please someone help me understand or educate me on this...

The Model Y has a large PC sitting in the interior which can easily exceed 150 degrees on a hot day. Would you turn on your PC at home if it was 150 degrees? The car uses a Heat pump which is so much easier on the battery than A/C to maintain the cabin at 105 degrees. It actually kicks on around 110-120 degrees but then maintains the cabin at 100F. It will draw the battery down up tp 1%/hour in my experience when parked. That said, I use it and think the small price in lost battery % is worth keeping the computer screen cooler. I live in Las Vegas and with temperatures around 105 the car will rapidly heat up to 125F in the cabin within 15 minutes of being parked. I normally leave the cabin overheat protection off in my garage and it typically gets up to 110 degrees both in the garage and the cabin so I shut off the overheat protection to prevent excessive battery draw as well as wear on the heat pump. That said several times I forgot to turn the Cabin overheat protection on when my wife went out shopping and noticed temperatures over 135 degrees when she was parked, but fortunately I was able to cool it down with the APP remotely. It would be nice to be able to turn on Overheat protection with the App, but that is so far not available. We do have a full sun shade on the overhead window and all around the interior of the car which I think helps minimize cabin temperatures when parked.

 

[cenwesi]

Regarding the Cabin Overheat Protection I would suggerst using it

The Model Y has a large PC sitting in the interior which can easily exceed 150 degrees on a hot day. Would you turn on your PC at home if it was 150 degrees? The car uses a Heat pump which is so much easier on the battery than A/C to maintain the cabin at 105 degrees. It actually kicks on around 110-120 degrees but then maintains the cabin at 100F. It will draw the battery down up tp 1%/hour in my experience when parked. That said, I use it and think the small price in lost battery % is worth keeping the computer screen cooler. I live in Las Vegas and with temperatures around 105 the car will rapidly heat up to 125F in the cabin within 15 minutes of being parked. I normally leave the cabin overheat protection off in my garage and it typically gets up to 110 degrees both in the garage and the cabin so I shut off the overheat protection to prevent excessive battery draw as well as wear on the heat pump. That said several times I forgot to turn the Cabin overheat protection on when my wife went out shopping and noticed temperatures over 135 degrees when she was parked, but fortunately I was able to cool it down with the APP remotely. It would be nice to be able to turn on Overheat protection with the App, but that is so far not available. We do have a full sun shade on the overhead window and all around the interior of the car which I think helps minimize cabin temperatures when parked.

Thanks everyone for explaining it to me. It all makes sense now.