Standard 90.1-1999, Energy Standard for Buildings Except Low-Rise Residential Buildings
NOTE: All documents linked from this page are in 
PDF-format.
(These descriptions may not be complete and are provided for information only.)
Addendum a (Clarification to 5.2.1.2, Substantial Contact.)
Addendum d (Clarifies what F-factors should be used for trade-offs in the calculation procedures for slab-on-grade insulation in 5.3.1.5, Slab-on-Grade Floor Insulation. Appendix A, Section A6.)
Addendum e (Clarifies that the calculation procedures in Section A9 can also be used for determining heat capacity of assemblies not covered in Tables A6 and A7.)
Addendum f (Revises Appendix B to change the unheated slab-on-grade floor criteria for residential spaces.)
Addendum g (Revises Appendix B to change the heated slab-on-grade floor values in Tables 19 through 26.)
Addendum j (Changes to 6.2.1, Mechanical Equipment Efficiency, and corresponding Tables 6.2.1C, H, I & J.)
Addendum k (Exceptions to 6.2.3.1.1, General, have been reworded for clarity and consistency.)
Addendum n (Change to the Exceptions to 6.2.3.2.4, Shutoff Damper Controls relates to gravity dampers and makes the statement consistent with the requirements of 6.1.3 (n), Simplified Approach Option for HVAC Systems.)
Addendum o (Change to 6.2.3.2.5, Zone Isolation, clarifies how zones may be grouped and removes the detailed performance requirements.)
Addendum q (Deletes 6.2.3.5, Enclosed Parking Garage Ventilation, in its entirety.)
Addendum r (Revises Exception to 6.3.1 (b) with regard to economizers.)
Addendum s (Exception to 6.3.1.4, Economizer Heating System Impact, was added to ensure that code officials would allow economizer operation where reheat was allowed.)
Addendum t (Change to 6.2.5.3.1, General, and 6.2.5.3.2, Air System Balancing, relates to system balancing and removes the exception to 6.2.5.3.1.)
Addendum u (Change to Table 6.2.1B, Electrically Operated Unitary and Applied Heat Pumps-Minimum Efficiency Requirements, adds the heat pump minimum efficiency ratings using the ISO procedure that are equivalent to the current requirements.)
Addendum v (In 9.2.1.1, Automatic Lighting Shutoff, the term 'occupant intervention' is vague and needed clarification.)
Addendum w (Change to 9.3.1.2, Space-by-Space Method of Calculating Interior Lighting Power Allowance, clarifies the intended use of this additional interior lighting allowance.)
Addendum y (Clarifies the definition of 'General Low Bay' and 'General High Bay' under the heading of Industrial Buildings, Table 9.3.1.2, Lighting Power Densities Using the Space-by-Space Method.)
Addendum z (Change to 9.3.2, Exterior Building Lighting Power, and Table 9.3.2, Lighting Power Limits for Building Exteriors, clarifies the language and intent of exterior building lighting power.)
Addendum aa (Change to 8.2.1.1, Feeders, and 8.2.1.2, Branch Circuits, specifies that connection load is not always the sizing method used in electrical design.)
Addendum ab (Change to 9.3, Prescriptive Path, and Table 9.3.1.2, Space-by-Space Method of Calculating Interior Lighting Power Allowance, clarifies that the additional power allowances apply to any lighted area that meets the criteria.)
Addendum ac (Change to 7.2.1, Sizing of Systems, provides additional wording to the designer for more flexibility in determining the load of the system.)
Addendum ad (Numerous changes including Tables 6.2.1A, 6.2.1B, 6.2.4.2B, and 6.1.3; 6.2.3.1, 6.2.4.1, 6.2.5.1 & 6.2.5.2.)
Addendum af (Changes to 4.1.2.2, strengthens the standard, eliminates the possibility of loopholes.)
Addendum ag (Changes to 5.2.2.1, 5.2.2.2, A8, Tables A-17, A-17 and A-19. Revise U-factor requirements for glazed wall systems in vertical fenestration to require compliance with NFRA certification programs.)
Addendum ah (Change to 9.3.1.1, allow building area lighting power allowance method to be used for all buildings.)
Addendum ai (Change to 9.3.1.1, adding footnote to Table 9.3.1.1 to indicate specific building types apply.)
Addendum ak (Appendix B, Tables B-1 to B-26 (SI only): Revises all U-factors in SI edition to be consistent with the IP edition.)
Addendum al (In Section 3 modifies the definition of pump system energy demand. Also, change to 6.3.2.1, 'mechanical refrigeration' to 'mechanical cooling', and 6.2.5.3, deleted certain requirements for system balancing.)
Addendum am (Changes to subsections of 4.1 and exceptions, rewritten version of Section 4 makes clear the different treatments given to additions and alterations to existing buildings.)
Addendum an (Change to 11.4.2, coordinates subsection 11.4.2 with 4.1.2.1 and 4.1.2.2.)
Addendum ao (Changes to the entire Section 5. No changes to the requirements. The revision simply restructures to make it easier to read and use.)
Addendum ap (Wording change to 11.4.3(e) and (f), this clarifies the rules for air and water economizers for budget building design.)