Bright white residential roofing

Discussion in 'Off Topic' started by Wolfshoes, Aug 9, 2015.

  1. Wolfshoes

    Wolfshoes Member

    My parents residential retirement community (where they snowbird) near Phoenix AZ maintains their housing exteriors as a group. Recently the roofing shingles were removed and replaced with new color roofing shingles. I am surprised that in the desert southwest a major development would reinstall common roofing shingles and not take the opportunity to go with a reflective cool roof option.

    I could suggest what they could have done for about the same amount of money in material and what they would have gained from a economy reflective roof.

    One of the most bang for the buck options in the cool roof arsenal is hot installed modified bitumen with 2 coats of white elastomeric roof coating. Here is a picture of where this system was installed on a commercial storage building one year ago in Illinois.

    View attachment 58642

    materials used:

    The water based coating material applied at closer to 150 ft per gal on a recoat or original coat. Label coverage is 250-350 sq ft per gal. This may be about right for the second coat. Over all this adds up to about $80 per 100 sq ft; about the same for materials as a mid range three tab shingle system.

    What do you gain (according to my measurements):

    Using a indoor digital thermometer with a wireless outside remote sensor as a test instrument installed 1 inch below the metal roof deck with a roof layer described above installed over it; temperature measurements were taken. The roof tested was the same age and construction as the one pictured, but was covered years ago and painted with a common aluminum fortified roofing coating that was now a flat medium grey. This medium grey roof could be considered a common average roof for test purposes. The roof is in the process of being coated with the modern white roof coating described above. Degrees tested are in fahrenheit.

    Blistering hot late July day in northern Illinois: 85 degrees
    temperature under grey roof underside 105 degrees
    adjacent area temperature after 1 coat of white coating 100 degrees
    ( two coats would be better but with weathering may represent a more accurate measurement of long term gain)

    therefore solar temperature rise under grey roof 20 degrees
    temperature rise under adjacent white roof 15 degrees
    temperature reduced under white roof 5 degrees
    therefore temperature rise reduced 25%

    It may not sound like much, but the 5 degree reduction could be millions of btu's of heat not making it into the structure over the long term. Closer to the roof providing shade.

    In order to maintain a acceptable residential appearance it could be suggested that roll seams be vertical instead of horizontal. Walking on the roof in the future may require foot covers since the roof is more prone to scuff and mark. Washing the roof is best done without standing on the roof since hoses could mark the roof. Areas subject the leaf or tree sap staining may best be coated with the 20 year oil based (Seal Best brand) version which may allow for a more aggressive power washing in the future. The 20 year version is not as bright a white with a more oil based typical yellow tint.

    It also happens that my parents installed solar panels a couple years ago that that had to be removed for the shingle work. In addition to the cost of removal (think lift equipment and manpower), the reinstall can take as long as the original install of solar panels since the mounting holes have been covered by new shingles. By preinstalling the reflective roof described above there would be no shingle replacement (or solar panel removal) since the roof deck will be recoated and not replaced (nearly as often perhaps almost never) in the future.

    The reflective roof or cool roofs in general offer additional benefits in reducing the urban heat island effect and can act as a global warming offset. Reflective roofs are not recommended in northern states based on all year energy usage but after taking into account the heat island and global warming offset, this recommendation may change in the future.

    As for me; my opinion is if shingles are coming off and the structure is below the arctic circle, its time to consider a reflective roof since the difference is not that drastic and the effect of melting snow on the roof would not be that drastic. Installing the material myself over the years, it is also my opinion that with installation tweaks, a Santa's Village bright white roof can have and maintain an acceptable appearance in residential use.

  2. Wolfshoes

    Wolfshoes Member

    Posted picture to thread white roof coating 002.jpg
  3. 2old2learn

    2old2learn Member

    What would be really nice is a spray coating that is temperature sensitive and could color shift based on temperature. The hotter the roof temperature, the whiter it gets and the cooler the roof temperature, the darker it gets.
  4. jaguar

    jaguar Well-Known Member

    I need to do something about the tin roof here since our summers are like in Arizona. But usually there is next to nothing available for such a purpose in this country. I will look around.
  5. 2old2learn

    2old2learn Member

    An interesting observation that I have made regarding the color of roof coatings is that in southern Europe most of the older, say 100 to 1,000 years old, structures predominately have the orangeish reddish colorations . It might be advisable to do some studies involving those colors too. The builders of the past still have lessons we could learn from them. In the fall of 77, I spent the night in a shepherds hut up in the mountains of north central Spain that was ages old and have eaten in restaurants that were over milenia in age with the signatures of Kings and Queens on the walls of the Who's Who of the great houses of Europe including Christopher Columbus. I've seen mountain ranges that mimic the Eastern range of the Rockies that had been terraced from their bases to their mountain tops for as far as the eyes could see in both directions and then used the stone to build self standing stone fence walls to create a network of sheep pens that looked like miniature large cities. Most likely all by hand, using woven baskets, sharpened sticks, and fire and water. At least a 1,000 years old.
  6. KCvale

    KCvale Motorized Bicycle Vendor

    Hot weather roofing materials...

    I have lived in the Phoenix area for ~50 years and worked for my Dad's roofing company for 8 of them back in the late 70's and early 80's.

    The roof of your your house (unless it's it's a flat roof which we do here as it doesn't snow) is half the Look of your home.

    White rolled roofing on a $200K home makes it a $150K 'trailer park' home.
    'Trashy' as it were.

    Clay tile roofed home homes on the other hand look great and with their air buffer between the outer curved hard surface and the waterproof deck actually provide better thermal insulation and extent the length of the life of the underlying waterproofing to 20 years.

    If you are talking a mobile home with a corrugated tin roof then a foam coating with white reflective paint is a huge plus, but not something you want to want to use on a real house with a sloped roof in my opinion.
  7. 2old2learn

    2old2learn Member

    When I lived in Europe I couldn't help but notice the reddish earth colored clay tiles on so many of the homes that were often several hundred up to several thousand years old. I was living in Madrid, Spain and traveling out from there and have wondered if the ancients had already determined the best materials and the best colors for a Mediterranean climate.
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Well, easy really, you seal the deck waterproof with no regard to looks, and then add a layer of air buffering material that sheds most all the rain that hits the roof.

    A very creative man might find a way to capture all the rain water for future use.
  9. Wolfshoes

    Wolfshoes Member

    I have another bang for the buck roofing find that is even better yet. It helps everybody, the environment; and saves you money. This is a system developed and used in Bermuda.

    This system offers a decorative shape; if you believe the rain will rinse it off a shape or texture efficiently enough.

    The bitumen or usual membrane layer is not used. Instead a shaped styrene is installed like roofing tiles as a backup water shield. The BIG benefit if this is its ability to keep nearly 100% of solar radiation out of the house roof deck instead of 25% by using a membrane.

    Highly reflective white elastomeric coating is used with a fabric layer sandwiched in the paint. By using a coating without an anti fungal additive like in Bermuda, the rainwater is clean enough to drink.

    With our state government reps cracking open the alka seltzer; wondering how they are going to reduce power plant emissions by 30%, less need for air conditioning could help.