Take 10: Cool Roofs

Aug. 5, 2010

If I apply a cool roof coating to an existing roof, can I expense it or must it be capitalized? How about if the new coating is fabric reinforced?


Excellent question. This is a tax related question though and should be referred to you tax accountant.

I have a black 60 mil EPDM membrane roof 11 years old. Can it be painted white to reduce heat absorption into the building?


I presume the EPDM roof is fully adhered, if so yes.  The EPDM should be cleaned with the manufacturer’s recommended cleaner and primer; after which it can be coated with the EPDM membrane manufacturer’s acrylic coating.  Care should be taken in this decision as there is empirical experience in which doing so resulted in unintended consequences in the form of condensation.

Did you say Hypalon is no longer available? What do we do to repair existing Hypalon roof systems?


The major manufacturers of Hypalon are no longer in the business of providing hypalon roof systems.  I have been informed that Burke Industries can provide Hypalon membrane and roof systems.  An existing Hypalon roof can be repaired by appropriate cleaning (activator), and if possible heat welding new Hypalon in place.  I’ve also seen self-adhering white EPDM used.  You may also wish to check with Burke Industries.

If you know that the roof will have substantial sq. footage of PV solar panels, how would that affect the roof design so that everybody gets maximum efficiency?


If new construction, there are many concerns that need to be addressed: wind vortexes, foot traffic during and after construction, snow loading, etc.  This is a subject unto itself and subject to a great deal of thought.  I would suggest that you reference my paper in the proceedings of the (International Conference on Building Envelope and Systems Technology)  ICBEST Conference, Vancouver June 2010 entitled “The Roof – Platform for Energy Production”* which reviews all the design concerns one needs to undertake when incorporating items such as solar into roof systems.
*ICBEST Proceedings can be purchased from the NRC website or please feel free to contact me if you would like a copy of my paper, [email protected]

Can you make an existing mod-bit roof into a cool roof by using only a coating?


Yes, adding a coating that meets the reflectivity and emissivity requirements has the potential  to bring an exsiting modified bitumen roof into a cool roof.

Can you explain a "ballast" again?  I hope I spelled that correctly.


Ballast when taking about roofing is typically washed river rock, typically nominally in size from ¾” to 1 ½” (min), that is used to hold a roof membrane in place on a roof and prevent wind uplift.

We are looking at cool roof options on an office structure with a pitched roof. The structures have roof top units that need to be accessed.  I have heard that the various single ply membranes get dangerously slippy when wet. Comments?


Yes, you are correct. TPO membranes are especially slick when wet, covered in frost, snow and/or ice.  If access is needed a system to do so should be designed.

What’s an EIFS wall?


EIFS (Exterior Insulation Finish Systems):  An exterior wall system in which insulation is installed on the exterior side of the wall and covered with a modified plaster system.

Can you talk about the financial implications, i.e., are there some business cases we can look at to convince our C suite to include a cool roof.


There are so many variables that go into a decision like that to render an answer.  Information such as building location, building type, thermal insulation, roof system design, what heating  and cooling systems are needed.  I recommend that you discuss this with a qualified roof consultant.

Would you recommend removing all metal fasteners and using adhesives only for fastening membrane and insulation?


I suggest that when possible the first layer of insulation be mechanically fastened and the second layer and cover boards be attached in adhesive. I prefer fully adhered membranes over mechanically fastened ones eliminating fasteners all together.

Will spray-on foam adhesive for fully adhered system meet FM requirements in Florida?


It is my understanding that while manufacturers have achieved very high wind up lift rating with spray foam adhesive that it is still not accepted by FM at this time.

Is there one type of membrane that is better than others (PVC vs. TPO vs. EPDM)?


I have designed ballasted 45 EPDM roof systems that are still in place, continuing to serve after 25 years plus. With 90 mil EPDM and the improvements in accessories, a 30 yr min can be expected.  Some PVC roofs have a long-term track record as well.  The new TPO membranes in my mind are still in their infancy.

Can applying ballast to an existing black 60 EPDM roof provide energy savings?


Yes it may.  It would be important to have an engineer check that structural capacity of the roof deck and structure and have the roof system reviewed to be sure there would be no ill effects or unintended consequences.

Can you speak a little more about coatings as a cool roofing option?


Coatings can be a viable option for attaining a cool roof.  Proper preparation of the roof surface is important.  Coatings come in all grades and costs and I would recommend that you review the product data of the various coatings that can be googled.

Do bright roofs at/near airports interfere with pilots' vision?


Yes, and there have been several lawsuits in this regard and the ‘tarnishing’ of the roof surface to remove the glare.  The same concern exists when a reflective roof is placed adjacent to a higher building with windows.

Please reconcile the "high" thermal emittance property noted of cool roofs and reference to cool roof membranes having "low" emittance per the presented slide.


Cool roof surfaces have a high emissivity 70 -75% and have a low thermal absorption, where a brick has low emissivity and a high level of thermal absorption – just walk by a masonry  wall after dark after it’s been in the sun.  Sorry if this was confusing.

It seems like DOE is a little short sighted when it asks for a "cool roof" vs a roof designed for 20 to 30 years. Would you agree that cost savings means more than just saving energy on heating or cooling. Longevity is also very important when discussing the cost of a roof.


In MY opinion the EPA, LEED and now the federal government are very short sighted.  Having those who have little if no roofing knowledge and certainly no responsibility for their requirements mandate a roof color is doing more to achieve poor roof systems than all the poor contractors in the country.  In the Chicago area alone there was over $10,000,000 spent in the  replacing of roofs of less than 3 years old because of these actions.  Durable, long-term service life roofs should be the goal, not simply a cool roof surface.

Any suggestions for an addition of PV panels to an 8,000 sq ft residence that has a tile roof, located in San Diego. Owners are concerned about the aesthetics of the panels.


What I would do is thoroughly investigate the appropriate panels and present the panels superimposed in elevations or photos to the Owner for consideration.  They would also have to be mounted so that there is clearance below the panels so that leaf debris and another obstructions such as bird nests do not accumulate.
The not-in-my-backyard syndrome seems to apply here, and the owner would have to realize that there will be an aesthetic challenge, but through the proper research of the numerous products out in the market and proper design they can achieve their goals, both functionally and aesthetically.

How does a white EPDM or TPO cool roof age compared to a metal roof?


At this time it appears that a metal roof would have a greater service life than the other two.

Voice your opinion!

To join the conversation, and become an exclusive member of Buildings, create an account today!

Sponsored Recommendations

Decarbonization 2024: How Digital Tools Minimize Your Carbon Footprint

Discover the untapped potential of digital electricity infrastructure in revolutionizing building electrification and decarbonization, unlocking a sustainable future while reducing...

Building Security & Technology Series: Webinar 3 - Proptech

Date: May 22, 2024Time: 1:00 PM EDT / 12:00 PM CDT / 10:00 AM PDT / 5:00 PM GMT Duration: 1 Hour eachGold Sponsors: Genetec, ISS, PrometheusSilver Sponsors: Eagle Eye Networks...

Building Security & Technology Series: Webinar 4 - Lessons Learned

Date: May 29, 2024Time: 1:00 PM EDT / 12:00 PM CDT / 10:00 AM PDT / 5:00 PM GMTDuration: 1 Hour eachGold Sponsors: Genetec, ISS, PrometheusSilver Sponsors: Eagle Eye Networks,...