Non-Residential Reroof Construction Calculator
Download Calculator (Microsoft Excel Document)
Instructions for Use
Enter the Zone number that corresponds to you project location in the RED box. There is an example city for each zone number listed in the table. Refer to the Joint Appendices for the 2005 Building Energy Efficiency Standards for Residential and Nonresidential Buildings for a complete reference list of cities and zone numbers.
Enter building mass number from Table 2 in the corresponding RED box. Typically most metal or wood frame construction is considered light mass construction.
Enter the R-Value of the existing structure that is being considered for recover in the corresponding RED box.
Enter the reflectance of the roof system as listed from the CRRC website in the corresponding RED box. The CRRC listed reflectance values can be found online at www.coolroofs.org. If a product is not listed with CRRC then enter a value of 0.10. If the roof system has an emittance less than 0.75 then the
Reflectance Calculator (See Below) must be used to determine the proposed reflectance.
Reflectance Calculator Instructions
Step 4a: Enter the reflectance value for the proposed roof system from the CRRC website in the corresponding RED box.
Enter the emittance value for the proposed roof system from the CRRC website in the corresponding RED box.
The result will be the calculated proposed reflectance for the roof system. Use this value to enter into the RED box in Step 4.
Results are listed at the bottom right corner of the calculator. “Existing R-Value” is the current R-Value of the existing building. “Trade-Off R-Value” is the total R-Value of the assembly that needs to be obtained when using a roof system with a reflectance less than 0.70. “Additional R-Value” is the amount of R-Value that must be added to the existing structure to allow for the use of a membrane system with a reflectance less than 0.70.