reflective paint on roof?

[wanderwheels]

My 2017 Montana sits out in the full sun in southern New Mexico. It has what appears to be a white rubber roof. I am thinking of painting it with a silver reflective paint to deflect a little of the sun. Two questions: Will the paint react adversely with the roof coating? Is it worth the bother?

[Mikendebbie]

I work in the commercial construction industry. I am not a roofer -but I have dealt with roofing of all types. I have never seen a reflective coating applied to a membrane roof of any type (rubber, EPDM or TPO). Generally the white color of the membrane functions as the reflective surface and meets energy code requirements for new construction. Maybe there is a roofer in the forum that can confirm or deny my assumptions.

Commercial building owners are always looking for cost effective ways to save energy. I have a feeling that if there was a super-duper reflective coating for new roof membranes that substantially increased the reflectivity and energy saving performance of a roof - I would know about it, and we would be routinely installing it everywhere...but I have not seen it being done that way in my 40 yrs in the biz.

I think the best we RVers can do is wash the roof 1-2 times a year to keep it clean and allow it to reflect what it can.

[Mikendebbie]

I got a PM from "bshgto" with some really good questions concerning my previous post about roof coatings. His questions prompted me to do a little googling on the subject.

To clarify my background - I work for a commercial general contractor whose primary business is new construction...therefore I don't see reflective coatings applied over brand-new roofs. However - if you try googling "reflective coatings for TPO roofs" - you will find many options available on the market. I think these coatings are used to treat older roofs. I have never been involved in roofing maintenance and repair programs, so I am not familiar with the world of roof coatings...but they are out there.

TPO is sort of a plastic+rubber-mix membrane. EPDM is a rubber membrane. There is also a PVC plastic membrane roof - but TPO membranes have become the most commonly used product in the past 15 yrs of my experience.

I googled "study of reflectivity of colored TPO roofs" to see if I could find something to compare and contrast the reflective qualities of white TPO vs. gray or cream - since some RV manufacturers use colored TPO. I am sure if I spent enough time I would find the answers for gray or cream vs white. Most studies I came across compare white membranes to black membranes, and the end results show that white reflects better than a dark roof. I would assume that a gray colored membrane or a cream colored membrane would yield slightly different results from a white membrane - but the differences would be minor as compared to (say) a black or dark roof. I found one study that ran the numbers out on a 10,000 sf single story building for white roof vs. black roof in 25 northern cities. For example in Nashville TN - the white roof saved $257/yr over black for cooling costs. My 3921FB Montana has ~361 sf of TPO roof on it...if I ratio the numbers down to my unit - I can expect to save $9/yr. in cooling costs...hmmmm? That is getting way too far off in the weeds for me. I think gray or cream TPO color will be close.

I live in TX and travel mostly in the South - so reflecting heat is good for me. For cold weather up north - a white heat-reflecting roof might not be the best choice - but I don't know that I have ever seen a dark roof on an RV.

I also mentioned washing the roof once or twice a year in my previous post - because I had read about it in this and other forums. I decided to go actually read the Keystone Owner's Manual for roof maintenance info. On page 80 it says "periodic washing" is a good thing. The TPO membrane on the Montana is "Superflex" by Alpha Systems. If you go to the Alpha Systems Inc website (alphasystemsinc.com) and click on "Product Care" then "Roof Membrane Cleaning Instructions" - it says this...

Periodic cleaning (three to four times per year) is the primary maintenance required. Alpha Systems recommends using a non-abrasive household cleaner, such as Dawn dish soap or SpicN-Span,and a medium-bristled scrub brush. Do not use any harsh or highly-abrasive products during routine cleaning. When finished cleaning, remember to thoroughly rinse the roof and sidewalls in order to remove any soap residue and to prevent streaking.

Washing the RV roof is not something I enjoy anymore. Frankly I'm scared up there. It's taller than any RV I have ever had...I think I can see both the Dallas and Houston skylines from up there! I have always been a "do-it-yourself" kind of guy - but I probably need to pay somebody to get up there and wash the roof.

I could not find a technical data sheet on "Superflex TPO" on the Alpha Systems website. I assume we have a 45 mil thick TPO membrane fully glued/adhered to the "plywood" RV roof deck. I see 60 mil membranes as the most commonly used thickness used on commercial buildings, and I see lots of 45 mil roofs - especially when lower cost is the owner's goal. I rarely see 80 mil membranes used due to the extra cost over 60 mil. TPO has been in use in the US since 1992 and has proven to be reliable. It is generally the "go-to" roof for most commercial applications. Frankly, after doing a few searches and reading up on this stuff I think we have a good product on our RVs.

[waynemoore]

Great write up. Thanks

[BuilderBob]

Be care full what you put on your Roof do not use any thing that is a petroleum product it will destroy the TPO or EPDM roofing. And you will be paying for a new roof!

Bob & Carol
Washington St
2017 HC HM352RL 2008 Dodge 3500 DRW CC LB 4x4

Happy Trails

[bigred715]

Our trailer is under cover, so I wash once at start of summer and once in the fall. Use Dawn and small scrub brush on my hands and knees.

[Texan]

I would think white would reflect as well as silver. You don't want to do anything to void your warranty. Your roof is probably the most expensive thing you can replace on your rv. The sun will do more damage to your decals and exterior gel-coat than the sun to your roof. Mikendebbie has obviously done a lot of research and given some great advise on just washing the roof. Nothing scientific here on prolonging your roof short of installing a roof over top of your rv which is not doable for those who move around a lot.