Tremco Roofing and Building Maintenance DivisionTitle 24 White Paper

August 11, 2010

 

Roofing and Building Maintenance Division

Title 24 White Paper

What Is Title 24?

California 's energy standards for buildings is known as Title 24. The Energy Efficiency Standards for Residential and Nonresidential Buildings is the official name of Part 6 of the California Energy Commission’s Title 24. It was established in 1978 in response to a legislative mandate to reduce California 's energy consumption[1]. The standards are updated periodically to allow consideration and possible incorporation of new energy efficiency technologies and methods.

New standards were adopted by the Commission in 2001 as mandated by Assembly Bill 970 to reduce California 's electricity demand. In the current standard there are no mandatory requirements to install Cool Roofs, but credits are offered through the overall envelope approach and the whole building performance method. Recent changes to the law have made it clear that, by October 2005, most new low-slope ( roofs with a slope less than 2:12 ) new nonresidential building roofs and re-roofing projects over air-conditioned spaces will use a Cool Roof.

What Is A Cool Roof?

Figure 1. Application of Tremco’s High Build Reflective Roof Coating


The term Cool Roof refers to the outer layer or exterior surface of the roof (Figure 1). However, not every reflective roof can be called a “Cool Roof”. Under Title 24 qualifying Cool Roofing materials must be certified and labeled by the Cool Roof Rating Council (CRRC). A Cool Roof is defined by the CRRC as a roof that will provide a minimum reflectance of 0.70 and a minimum emittance of 0.75

[2]

. The certification and labeling requirements for Cool Roofs are specified in Section 10-113.

 

How Does Title 24 Work?

The principle concept of Title 24 is the energy budget. Each building gets an energy budget based on climate zone and building components. Each type of component, such as windows, HVAC and roofs, receives a baseline value which contribute to the budget. Individual components may exceed their baseline values, however, a building must meet the budget or no building permit will be issued. The 2005 Title 24 baseline budget for low-sloped non-residential buildings assumes that the standard building budget includes a Cool Roof component.

How Do You Interpret The Code?

There are two separate approached an architect can take to assure energy code compliance:

  1. Prescriptive Method:You must demonstrate that the building complies with Title 24, and then demonstrate that the building complies with all of the relevant prescriptive requirements in the Tier 1 Prescriptive List. This means that the roof meet minimum reflectance and minimum emittance requirements

  2. Performance Method: An energy consultant makes an energy simulation with a computer program supplied by the California Energy Commission. The whole building complies if the total energy is less than that of the standard design (which includes a Cool Roof). The proposed design may or may not have a Cool Roof as long as total energy use is less than the standard design. Tradeoffs can include lighting, water heating, HVAC, windows, doors and walls to offset the lack of a Cool Roof.

How Does The Sun Affect A Roof Surface?

Like our skin, the UV rays and heat from the sun can damage and result in premature aging to a roof system. These rays can cause temperatures to easily reach 170 ° in the heat of the day on a black roof. The theory is that when the roof system heats up its components - asphalt, polymers, etc.— react over time and can cause the roof system to crack, become brittle and age. Comparatively a white reflective roof surface will only reaches 110° in the heat of the day, 60° cooler than a black roof. Hence the name “Cool Roof”.

There are two properties that help a roofing material stay cool. The first, reflectance, is how well it reflects sunlight. Lighter colored materials have better reflectance, which keeps heat from entering the building. The second property is emittance, the roofing material’s ability to release absorbed heat quickly. Half of the sun’s heat arrives as invisible radiation. So, high reflectivity and emittance are important properties for a roofing product in preventing heat absorbance and temperature buildup on roof surfaces.[3]

Over the long term reflective roof surfaces reduce the extreme heating and cooling process of a roofing system extending its operating life. In addition, many reflective roof coatings can seal the existing waterproofing layer and give the existing roof added service life.


 

There are three significant benefits of cooler roof temperature:

  1. Reduced energy use for building cooling improves the comfort of building occupants and lowers a building’s cooling costs.

  2. Lower power demand reduces demand on power plants during peak energy demand periods.

  3. Lower ambient air temperature decreases the Heat Island Effect,lowers city temperatures, and creates less smog.

 

ENERGY STAR® Rating System

The ENERGY STAR ® rating system has a different definition of a Cool Roof from that of the CRRC. Roof products that meet or exceed a 0.65 solar reflectance level, without compromising product quality and performance, qualify for the ENERGY STAR label[4]. The highest rated products are in the 0.85 range. Details are on the agency’s Web site, www.energystar.gov, which includes a complete list of products, including membranes and coatings that claim reflectivity measures ranging from a low of 0.70 to highs of 0.91 on a scale of 0 to 1.0.


Reflectance of Common Roof Surfaces[5]

Built-Up Roof with Dark Gravel

0.08 – 0.15

Built-Up Roof with White Gravel

0.30 – 0.50

Built-Up Roof with Smooth Asphalt Surface

0.04 – 0.05

Built-Up Roof with Smooth Surface and White Roof Coating

0.75 – 0.85

Built-Up Roof with Aluminum Coating

0.25 – 0.60

Single-Ply Membrane Black

0.04 – 0.05

Single-Ply Membrane White

0.70 – 0.78

Single-Ply Membrane Grey

0.15 – 0.20

Modified Bitumen with Mineral Surface Capsheet

0.10 – 0.20

Modified Bitumen with White Coating over a Mineral Surface

0.60 – 0.75

Unpainted Metal Roof

0.30 – 0.50

White Painted Metal Roof

0.60 – 0.70

Dark painted Metal Roof

0.05 – 0.08

Liquid Applied Coating Smooth Black

0.04 – 0.05

Liquid Applied Coating Smooth White

0.70 – 0.85

Liquid Applied Coating Smooth Off-White

0.40 – 0.60

 

Tremco Compliance with Title 24

Tremco offers a complete line of coatings and single ply membranes that are Energy Star certified and comply with Title 24 standards.

High Build Reflective Coating

· High solids, water based, heavy bodied elastomeric coating

· Initial Solar Reflectance: 0.83

· Initial Thermal Emittance: 0.83

Polarcote FR

· Intumescent, fire retardant, acrylic latex roof coating

· Initial Solar Reflectance: 0.83

· Initial Thermal Emittance: 0.84

TremFAST PIB

· A polyisobutylene single ply membrane for new construction, retrofit or recover

· Initial solar reflectance: 0.80

· Initial Thermal Emittance: 0.79

TremLite Coating

· 100% Acrylic elastomeric weatherproofing coating

· Initial Solar Reflectance: 0.82

· Initial Thermal Emittance: 0.87

TPA/TPA FB

· Tri-Polymer Alloy (TPA) Thermoplastic Single Ply Roof System

· Initial solar reflectance: 0.89

· Initial Thermal Emittance: 0.79

WallTite F

· Elastomeric, Fiber-reinforced Weatherproofing Coating

· Initial solar reflectance: 0.80

· Initial Thermal Emittance: 0.86

Tremco coatings One Coat Aluminum and Double Duty Aluminum do not meet Title 24 standards because the initial emittance values of all aluminum coatings are well below the 0.75 threshold.

For additional information about Tremco's products, visit our website at http://www.tremcoroofing.com or call (800) 562-2728.

Do Metal Roofs Comply?

Bare metal roofs do not meet the current requirements for a Cool Roof under Title 24. Uncoated metal roofing products tend to have low emissivity ratings. Consequently, metal roofs require a coating to satisfy the Cool Roof requirements of Title 24. Please note that the minimum coating thickness requirement does not apply to Painted metal roofing products. Tremco offers TremLite, a metal coating that meets both ENERGY STAR and Title 24 requirements.

What about Gravel Roofs?

There are severe limitations on the use of aggregate as a finished surface for roof membranes. Flood and gravel or ballast surfacing does not typically meet the reflectivity and emissivity requirements of Title 24.

What About Re-Roofing?

 


Figure 2. Tremco’s TremPly ® Elastomeric Single Ply Roof Membrane

 

Title 24 requires that a re-roofing project of an existing building have a Cool Roof. An exception applies for restoring existing roofs that have a rock or gravel surfaces, provided that new aggregate is installed, no layers are torn off and no insulation boards be installed.Californiabuilding code allows for existing roofs to be recovered (retrofitted) only once, however, any retrofits must meet the Cool Roof definition. A Cool Roof is required if the re-roofing covers more than 50 percent of the roof, or 2,000square feet(Figure 2). Thus, using Tremco’s BURmastic or ECOlastic products as restorative top pours is possible however, be sure to closely follow the provisions of this code to assure acceptance during the permit application process.

 

What Buildings are Affected?

 

Title 24 requires nonresidential buildings in the following Uniform Building Code Occupancy Groups to comply: UBC Groups A, B, E, F, H, M, R (limited), and S. These buildings include (but are not limited to):

 


 

 

· Apartment buildings with four or more habitable stories

 

· Assembly and conference areas

 

· Churches

 

· Commercial or industrial warehouses

 

· Grocery stores

 

· Hotels and Motel

 

· Industrial work buildings

 

· Offices

 

· Restaurants

 

· Retail and wholesale stores

 

· Schools

 

· Theaters

 


 

 

Are Any Buildings Exempt?

 

The Standards do not apply to UBC Groups I and U. These groups include buildings such as hospitals, daycare, nursing homes, prisons, private garages and agricultural buildings. In addition, the Standards do not apply to buildings that fall outside the jurisdiction of California building codes, such as mobile structures. The final exception to the Standards is qualified historic buildings, as defined in the State Historic Building Code (Title 24, Part 8, Exception to Section 100(a)).

 

What Are The Insulation Requirements?

 

Climate Zones R-value
1, 16 19
3 - 5 19
6 - 9 11
2, 10 - 13 19
14, 15 19

 

 

 


Figure 3. California Climate Zones

 

R-19 for all zones except zones 6 thru 9, which require R-11 (Figure 3) [6]. Hotels in certain zones must have R-30; see the actual code for these areas.

 

2004CaliforniaRebate Programs

 

Pacific Gas and Electric Company (PG&E), Southern California Edison (SCE), & San Diego Gas & Electric Company (SDG&E) and Sacramento Municipal Utility District (SMUD) offer rebates of 10 cents per square foot. Contact these groups directly for details on the application process.

 

National Cool Roof Programs

 


Program

Reflectance

Emissivity

ENERGY STAR

0.65

N/A

CBC – Title 24

0.70

0.75

LEED*

ENERGY STAR

0.90

 

* The USGBC has revised the requirements for the Heat Island Reduction credit in the LEED NC 2.2 Version. These changes are available on the USGBC website.

 

Precautions

 

· Dirt will decrease reflectance of a Cool Roof system in the first year by about 20%, as reported by Lawrence Berkeley National Laboratory studies

 

· Regular power washing of the roof may be required to maintain the Cool Roof reflectance.

 

· Aggressively power washing a Cool Roof coating may damage the coating.

 

· While power washing a roof, collection of the sediment may be required by local governments with strict storm water sediment restrictions.

 

· Be certain that applying a coating does not change the fire rating of the assembly.

 

Title 24 2005 Cool Roofing Section[7]

 

In order to qualify for compliance credit as a Cool Roof or meet the requirements of Section 143 (a) 1 or 149 (b) 1 B, a Cool Roof shall be certified and labeled according to the requirements of Section 10-113 and meet conditions 1 or 2 and, for liquid applied roofing products, 3 below.

 

1. Any roofing product with an initial thermal emittance greater than or equal to 0.75 when tested in accordance with CRRC-1 shall have a minimum initial solar reflectance of 0.70 when tested in accordance with CRRC-1.

 

2. Any roofing product with a minimum initial thermal emittance i nitial less than 0.75 when tested in accordance with CRRC-1, including but not limited to roof products with metallic surfaces, shall have a minimum initial solar reflectance of 0.70 + 0.34 * (0.75 - i nitial ) when tested in accordance with CRRC-1.
(This provision is helpful for products with emittance values slightly lower than the required 0.75.)

 

3. Liquid applied roofing products coatings applied in the field as the top surface of a roof covering shall be applied at a minimum dry mil thickness of 20 mils across the entire roof surface, and meet the minimum performance requirements listed in TABLE 118-C.

 

 

EXCEPTION 1 to Section 118 (i) 3:

Aluminum-pigmented asphalt roof coatings shall meet the requirements of ASTM D2824 and be installed as specified by ASTM D3805.

 

(For the most part, aluminum pigmented coatings will be far below the emissivity requirements of 0.75 and therefore will not be acceptable for use.)

 

 

EXCEPTION 2 to Section 118 (i) 3

: Permeable Cement-based roof coatings shall be applied at a minimum dry mil thickness of 30 mils when installed over a cap sheet surface, 40 mils when installed over a metal surface, and 200 mils when installed over a rock or gravel surface(s) and at a minimum dry mil thickness of 30 mils over other surfaces. Cement-based roof coatings shall contain a minimum of 20% cement, and shall meet the requirements of ASTM D822.

 

Websites And Links

 

Use these sites to educate yourself about coatings, Cool Roofs, green roofing products, laws, and Heat Island Effect.

 

&H6>Associations&/H6>


ASTM International

www.astm.org

Cool Metal Roofing Coalition

www.coolmetalroofing.org

Cool Roof Rating Council

www.coolroofs.org

National Roofing Contractors Association

www.nrca.net

Roof Coatings Manufacturers Association

www.roofcoatings.org

Roof Consultants Institute

www.rci-online.org

United States Green Building Council

www.usgbc.org

Western States Roofing Contractor's Association

www.wsrca.com

&H6>&/H6> &H6>Government&/H6>


California Cool Roofs Information

www.consumerenergycenter.org/coolroof/

California Energy Code Title 24 Updates

http://www.energy.ca.gov/title24/2005standards/
index.html

California Energy Commission – Title 24

www.energy.ca.gov/title24/

ENERGY STAR Roof Products

www.energystar.gov

EPA Roofing Comparison Calculator

www.roofcalc.com

Lawrence Berkeley National Labs - Cool Roofing

eetd.lbl.gov/CoolRoofs/

PositivEnergy - Community Energy Conservation

www.pstvnrg.com

&H6>Publications&/H6>


Facilities Site

www.facilitiesnet.com

Metal Roofing

www.metalroofingmag.com

Professional Roofing

www.professionalroofing.net

RCI

www.rci-mercury.com

Roofing Contractor

www.roofingcontractor.com

Roofing Siding Insulation

www.rsimag.com

Western Roofing Insulation & Siding

www.westernroofing.net



[1] www.energy.ca.gov/title24/

[2] www.coolroofs.org/codes_and_programs.html

[3] Hashem Akbari and Sarah Bretz, Cool systems for hot cities, Professional Roofing, October 1998, www.professionalroofing.net/past/oct98/feature.asp

[4]ENERGY STAR® Program Requirements for Roof Products, www.energystar.gov

[5]Inclusion of Cool Roofs in Nonresidential Title 24 Prescriptive Requirements, California Energy Commission, August 2002, page 38. ww.energy.ca.gov

[6]2005 Building Energy Efficiency Standards For Residential And Nonresidential Buildings, California Energy Commission, September 2004, page 39. www.energystar.gov

[7]2005 Building Energy Efficiency Standards For Residential And Nonresidential Buildings,
page 81.

June 1, 2005

3735 Green Road

Beachwood , Ohio 44122

800.562.2728

         
 

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