Why is the roof black?

[jay93]

I don’t notice it being any warmer because it’s black.

One thing I do hate is the finish on the roof. Not sure what they use to seal the carbon fiber but it seems to be highly sensitive to bird droppings and other environmental fallout.

I am very vigilant about keeping my car clean yet I have already had the finish eaten into in two spots. I now put a cost of spray wax on it every time I wash.

 

[Anonymous]

I am very vigilant about keeping my car clean yet I have already had the finish eaten into in two spots. I now put a cost of spray wax on it every time I wash.

I use a UV protectant spray on mine after every wash - i think the clear-coat on the CF is somewhat susceptible to UV and chemical (bird-dropping) damage. So far no damage to mine. I use Wolfgang Concours Series WG-9200 Deep Gloss Spritz Sealant

 

[alohart]

Instead, I bought some inexpensive silver chrome vinyl film to install myself. I had hoped that the roof was flat enough that I would not have to heat and stretch a large piece of vinyl film to avoid wrinkles along the edges. Unfortunately, that wasn't the case, so my installation looks terrible. However, it does reduce cabin heating noticeably when strong sunlight shines on the roof. I will probably remove the film as winter approaches, but probably won't pay to have it wrapped professionally because our i3 isn't driven much (only ~11k miles in 6 years) and is parked out of the sun in our apartment parking garage.

I removed the silver chrome vinyl film from the roof of our i3 today. If I had had an infrared thermometer and there were no COVID-19 restrictions, I would have parked our i3 with its reflective roof and a stock i3 in the noontime summer sun and measured the temperatures of each i3's headliners after being parked in the sun for various periods. That would have quantified the temperature difference. However, it didn't happen, so I'm left with only a subjective feeling that I could feel less heat radiating down into the cabin after wrapping the roof with reflective film.

Because I drive so infrequently and the autumn sun angle is so much lower, heat radiating into the cabin from the roof is less important than the ugly appearance of my flawed vinyl film installation, so I removed the vinyl film today. The roof looks so much better and is really clean In the future, I'll just let the A/C work a bit harder to deal with the radiating heat.

 

[Anonymous]

I live in the Dallas area, where summer temps can be in the 100F range. I find that good UV window tint (courtesy of the previous owner) and a reflective windshield sun screen keep the car from turning into an easy-bake oven. I think a lot more heat transfers in through the glass than through the roof.

 

[jadnashuanh]

I bought the BMW car cover way back when... It makes huge difference in the interior temperature when the sun is out. https://www.shopbmwusa.com/product/4656/BMW-I-CLIMATE-COVER

In reality, it only takes less than a minute to put it on, if you want to fold it when taking it off, it takes longer, but I just throw it in the back.

 

[Anonymous]

I looked at that BMW i Climate Cover, liked everything about it but the price :shock:

 

[jadnashuanh]

I looked at that BMW i Climate Cover, liked everything about it but the price :shock:

You can find it discounted, but yes, it was not inexpensive, but what from BMW is 'cheap'? My experience is that it keeps the interior probably 20-30 degrees cooler when on, and, with the large front windscreen, those take up a lot of space when you store them.

FWIW, the little window in the thing is a German thing, I think, to let you place your parking disk. Don't know if they still do this, but when I lived there long ago, in timed parking places, you had to put a card on the windshield with the time you left (it had a clock face on it). Enforcement then used that to decide if you'd overstayed your 'free' parking window. If you happened to set it ahead, thinking you'd sneak buy, and they happened to walk by noting that it's ahead of the current time, they could interpret it that you'd been there 24-hours or more and ticket you.

 

[Anonymous]

My experience is that it keeps the interior probably 20-30 degrees cooler when on,

Yeah, If my car sat in an open parking lot all day, totally worth the investment, but with a shaded driveway, and only an hour a day at the gym where the car sits in the sun, my accordion fold inside window screen does the job.

Many public and private/company parking lots require some sort of displayed parking permit /sticker or tag, so a view-port in the cover to allow them to be seen makes sense.

 

[Arm]

The i3 has a lot more glass than most other cars. That's what contributes to the vehicle's a/c not seeming to be as effective as other vehicles.

What makes you think the a/c is marginal? Mine works as well as the ones in my other cars.

We test drove the i3 on a 107 degree day, the car had been sitting in the sun all day, and it took over 30 minutes to cool off the interior. Our smart sat in the sun in our driveway not 4 miles away for the same time and it was cooled off in the 15 minutes it took to drive there. Ditto our Infiniti...... To me that indicates that the a/c could use some help.

BTW, this is typical summer heat where I live, not every single day, but quite common nonetheless. A car designed for city use, ie running errands ought to be able to cool the vehicle between stops and shops. Perhaps they should have Northern and Southern versions?

Maybe when charge points are more widespread people will just keep the a/c running in Precondition mode when parked and plugged in. That way the car would be cool when they came out and that way they could waste more energy than an ICE defeating the purpose of going EV. And why not when power is often free.....?

 

[PBNB]

Some interesting articles have been produced referring to Heat Island effect. There is a point where the black is more advantageous if you look at the entire year and heating and cooling costs. There are white roofing materials that can help reduce operating costs in hotter climates.

I would think that some of this research can apply to the roof of a car as well.

It would depend on the heat island rating for each area and if there is more days when the temp is higher than say 70 degree F., perhaps a white roof will help keep the temp down so you use less AC. If you are more Northerly, it may be that the black roof will help attract heat and potentially lower the heating demands.

I think it really depends on where you live and how the annual temps affect your comfort.

The other issue that we have is that BMW made our roofs out of exotic materials (carbon fibre) and the resins used to put the layers together may be exposed or clear-coated. If you are going to paint the roof, it may effect the resins and promote de-lamination of the materials. I would suggest a white wrap as a way to get white up there and preserve the resins. I could be wrong here but that is what my carbon road bike experience has shown me.

 

[richs]

The other issue that we have is that BMW made our roofs out of exotic materials (carbon fibre) and the resins used to put the layers together may be exposed or clear-coated.

Apparently, this doesn't apply if your car has a moonroof. I hadn't really thought about the roof material until I gently knocked on it. It's painted sheet metal in my 2017 i3. I looked at another i3 (without a moonroof) at the charger recently and finally understand what this old thread was all about.

But I have a black i3, so it's still black. :lol:

 

[jadnashuanh]

fwiw, the reason why the moonroof wasn't available for the first couple of years is that the DOT rules require it to have metal supports. The rest of the world was getting them with the CFRP roofs which are actually stronger. I wasn't aware that they made the entire roof out of metal for the US...that would make it less strong, IMHO. In reality, BMW had said in their original press release for the US that the moonroof would be standard, and personally, I preferred it not be, so for me at least, that was a good thing when they lost their request from the DOT or NHTSA, whichever! Similar hassle with the laser highbeams...it appears that recently they may have allowed the anti-dazzle functionality the original ones had maybe 4-5 years ago in the rest of the world on other models.