Commercial Energy Code

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ASHRAE 90.1

The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)     develops standards for energy efficiency in buildings. From these standards, they developed the ASHRAE 90.1 energy code for commercial buildings, which has become the code in many states throughout the country. ASHRAE 90.1 sets energy efficiency requirements for exterior and interior lighting, thermal envelope (insulation levels and maximum window areas), heating and cooling systems, and service water heating. In addition, the standard has guidelines for conducting an energy simulation of your building to show compliance.

The revision of ASHRAE 90.1 is now complete and is in the process of being codified.  In addition, an International Energy Conservation Code (IECC) has been developed for adoption.  The IECC includes both ASHRAE 90.1 revised and COMCheck as separate chapters.

Typical standards:                                                                                  

Lighting                                                                                            
To meet the lighting requirement, first determine the total wattage of lighting in the facility. Then, find the amount of lighting allowed using the various charts and tables in ASHRAE 90.1. If the amount of lighting does not exceed what is allowed, the building complies.

Exterior Lighting
Each aspect of exterior lighting has an allowance based on the type of lighting and the area or linear feet of surface. For example, customer parking lots receive an allowance of 0.18 watts per square foot. There are a number of exceptions to the exterior lighting requirement, including outdoor athletic facilities, public monuments, signs, retail storefronts, and exterior enclosed display windows.

Interior Lighting                                                                      
Typical allowances for indoor lighting are as follows:                          

Entire Buildings:
Offices -- 1.50 to 1.90 watts per square foot depending on the floor area
Retail -- 2.10 to 3.30 watts per square foot depending on the floor area
Schools -- 1.50 to 2.40 watts per square foot depending on the floor area and type of school

The interior lighting section also allows a designer to seek compliance using a space-specific method. Examples of requirements in watts per square foot are:

Room Location Watts per S.F.
Corridors 0.8
Fast Food Restaurants 1.3
Leisure Dining 2.5
Library Reading Area 1.9
Open Office Areas 1.8 to 2.1
Welding Shop 1.2
Barber Shop 2.0
Jail Cell 0.8
Emergency Room in Hospital 2.3
Retail (jewelry areas) 5.6
Tournament Badminton Facility 0.8
Recreational Ice Skating Rink 0.6

The code also allows credits by which you can increase lighting levels above code for areas that have natural day lighting with control over artificial lighting.

In addition to lighting, the energy code sets minimum numbers of lighting controls in buildings. The number of controls can be decreased if advanced control systems, such as occupancy controls or dimmable switches, are used.

Envelope                                                                                   
ASHRAE 90.1 sets maximum U-values (minimum R-values) for the components of a building between heated and unheated areas. The requirements are climate-specific and use "Alternative Component Package (ACP) Tables" for cities throughout the country. The tables show required insulation levels as well as maximum window areas depending on the building design.

Example                                                                                           
A commercial office building in Lexington, Kentucky with clear, double-paned metal windows with a U-value of 0.72 and no overhang above:

Ceilings -- U-0.056 (about R-19 continuous)
Floor over unheated space -- U-0.060 (about R-19 continuous)
Maximum window percentage -- 16% of total wall area
Framed walls -- U-.104 (about R-13 in steel-framed wall with R-3 continuous sheathing)

Heating and Cooling Systems                                                 
ASHRAE 90.1 has a lengthy set of requirements for the efficiency of heating and cooling systems. In general, they deal concern:

System sizing -- all systems must be sized using standard load calculation procedures.

Economizers -- in much of the country, air conditioning systems must be able to pull in outside air when comfortable to reduce use of compressors in the main cooling system.

Fan Power -- limited to 0.8 watts/ cfm for constant volume HVAC systems and 1.25 watts/ cfm for variable air volume systems.

Temperature Reset -- automatically adjust supply temperature in response to outdoor conditions to save energy.

Pumps and Fan Motors -- must adjust energy usage with flow rate.

Duct and Piping Insulation -- requirements based on difference in temperature between fluid and surrounding air.

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