Design Topics
December 2004

This month’s client bulletin is an authorized reprint of an article submitted to the BOMA Newsletter of November 2004 and was prepared by Whiteaker & Wadsworth Inc., roofing and coatings consultants.

2005 Title 24- “Cool Roofing”

Cool Roofing is the New Standard

Title 24 is the California energy code regulating the efficiency requirements for California buildings. As of October 1 st, 2005 , the new Title 24 standards will go into effect.

One important change is the use of “Cool Roofing” as a standard component of the building envelope. This means that if Cool Roofing is not specified as part of the building design, another energy saving building component must be improved to make up for the loss of energy efficiency inherent in a Cool Roof. Engineering calculations must demonstrate that the proposed building envelope heat gain and loss or the building’s overall energy costs will not exceed a Title 24 standard building design which incorporates Cool Roofing.

In other words, “Cool Roofing” is the default roofing material for all low slope new construction buildings. This is also true for Re-Roofing projects.

Dr. Lisa Gartland of PositivEnergy, in a recent article entitled Cool Roofs and Title 24, the California Energy Code, said “ A cool roof must be used if more than half the roof or more than 2,000 square feet of an existing roof is being replaced, recovered, or recoated. If cool roofing is not used for re-roofing, the building envelope must be improved in some other way to compensate for the lost (energy) efficiency opportunity, and calculations must be made to justify the effectiveness of these measures.”

A simple reroof project or repair must use Cool Roofing or an additional energy project must be financed, justified and performed in conjunction with a non-cool roof installation.

What is a Cool Roof?

Since we are talking about energy efficiency we are describing products that have been tested and certified to meet standards of reflectivity and emissivity. The certifying organization is the Cool Roof Rating Council. To be considered “Cool” a material must have a solar reflectance of 0.70 or higher and thermal emittance of 0.75 or higher.

There are some exceptions for tile and a few highly reflective metal surfaced products but the emphasis is on white or very light colored materials.

The standard California low slope roof system has been a BUR (built up roof) membrane consisting of one base sheet, two ply sheets set in hot asphalt, and a mineral surfaced cap

sheet also adhered in hot asphalt. The cap sheet surface is a light gray in color and provides a reflectivity of only 0.25 or so. Unless this standard product is modified to include a Cool Roof coating or surfacing material it will not meet the title 24 requirements.

There are currently two major Cool Roof product categories. Single Ply thermoplastics and fluid applied roof coating systems.

Single-ply sheet membranes primarily fall into the PVC or TPO families. They are typically white in color and easily meet the Cool Roofing requirements. They are often applied in conjunction with insulation or a separator sheet using screws and plates. They may be installed in new construction, recover, or complete tear-off applications. Since thermoplastics are a relatively new product class, it is important to research the track record and testing data of a particular manufacturer. A customized roof specification prepared by a competent roofing expert may be a wise move for commercial property. Flashing details are critical with these systems as there is only one layer of membrane providing waterproofing.

Fluid applied systems are installed in a variety of ways depending on conditions. Polyurethane foam and coatings dominate new construction projects. Re-roofing systems include coatings reinforced with a polyester mat, coatings alone, or foam and coating. It is important to have a roof review prior to bid to insure that a detailed plan is developed. If a coating only system is desired it is necessary to reinforce penetrations, waterways and install the product at the manufacturer’s recommended rates.

Will it affect my roofing budget?

In the new construction arena there will definitely be some cost impact. It will probably raise the price of a current BUR cap sheet roof by 70-80 cents per foot to add a Cool Roof coating over the cap sheet surface. BUR manufacturers are probably working to develop less expensive options but they haven’t hit the marketplace in force.

Reroof applications using high quality acrylic systems are currently almost always the best value. Besides the energy savings to the particular building, they are typically less expensive to apply than other systems. Fully reinforced coating systems, foam and coatings, as well as the single ply families are already comparable in price to a conventional built up roof with a tear-off. There should be no real cost impact unless a Cool Roof is not desired.

One caveat: Not all roofers or manufacturers are experienced with Cool Roofing applications. This is especially true with coating systems over existing roofs. It is essential to determine the existing conditions and specify the appropriate solution.

These systems have a great track record with quality-oriented manufacturers, certified contractors, and third party inspection.

Whiteaker & Wadsworth, Inc. is a consulting firm specializing in commercial roofing and waterproofing. Any questions regarding budgeting, systems, qualified contractors etc. may be directed to Bruce Whiteaker brucewhit@earthlink.net.