I think it would not be a great idea to paint the inside of the bus with SolarFlex. It dries to a somewhat latexy slightly textured finish (like reptile eggs?). I think it would hold dust and dirt. While my exterior roof isn't exactly dirty (except where the stupid birds are roosting in the tree... ick). It isn't what I would call clean either.
I only have two coats of SolarFlex on my roof. With only box fans running (I added pleated Filtrete brand dust filters to make them into air cleaners so my air movement is low even on HIGH) and parked under shade of a tree. Exterior temp says 85 (weatherunderground.com). Interior thermometer sitting on a roof rib at the peak of the bow is showing 83.7. My ceiling is the same temp anywhere you touch it. It seems to stay warmer in the winter (my thermometer has a magnet glued to the back. I stick the thing all over the ceiling). So in winter, I do not have a cold ceiling and in the heat so far, I do not have a hot ceiling. The only insulation is the stock fiberglass batts from BlueBird...measures 2" of rather dense stuff... looks more like the stuff they put in ovens and ranges than the house batts). I rolled the SolarFlex down to the tops (eyebrow awnings) of the side windows. Front & rear was stopped 1/2" past the roof panel rivet line on top of the bus.
You can buy a tan
and a light tan tinted SolarFlex
. Tinted a colour would hide the dirt a bit unlike white which makes it stand out. You would have to contact Henry's to find a retailer. I've only seen the white. Home Depot carries the Henry's but not the 286 or 288. And it's not on their website either. You may check with the Pro Desk to see if your store can special order it. Took 5 gallons to cover the roof with 2 coats (40 ft bus). I would think the sides would need at least three coats to look good. The dark navy blue on the roof shadows thru in some spots on my roof.
BEFORE you go and paint the sidewalls of your bus, roll out a test panel on some scrap. Leave it out and see how it dirties up. For the side, I would use a smooth foam roller (not the fuzzy ones like recommended for roof application). After I rolled the bus roof (1 coat) my daughter (the one with the house... it's white and needs a paint job) stood in the bus and exclaimed how cool it was over the previous day. Then wanted to know if she could paint her stuccoed house with the stuff. Her thoughts were SolarFlex would have sealed up the fine cracks in the siding and kept the heat down in the hot NM summers. We told her to watch how the roof looked over the next couple of months before going out to buy the stuff to paint her house. She watched and changed her mind. the roof when from bright white to a slightly dirty white from all the dust storms and general dirt in the air. Looks fine from the ground, but if you look at it really close up, it looks a little grubby.