E17: Air Economizers During Favorable Outdoor Conditions – Above Green

Requirement Summary

This measure can be claimed if the air handling units in the HVAC system use air economizers. Critical areas with special needs for indoor air quality, such as Operation Theatres (OT) and/or the Intensive Care Units (ICU) in hospitals, are exempt from this requirement. By default, the base case system does not have air economizers.

Intention

Cooling energy can be reduced in buildings if outside air conditions are suitable to cool the building with little or no need for mechanical cooling.

Approach/Methodologies

The effectiveness of air economizers is highly dependent on the outside air temperature and humidity levels, which are measured through an outdoor sensor in the economizer system. When the conditions are suitable, the outside air damper is opened fully and the cooling compressors are turned down or shut off.

Potential Technologies/Strategies

Decision on the inclusion of air economizers should be based on analysis of outdoor air temperature and humidity in comparison to the desired indoor temperatures. While this measure has potential to reduce cooling energy significantly in some locations, increased capital and operating costs are possible if the system is not designed and maintained properly. Air economizers should typically be avoided in following circumstances:

Especially corrosive climates, such as near an ocean
Hot and humid weather
Scarcity of sufficiently trained maintenance staff

Relationship to Other Measures

When weather conditions are appropriate, an air economizer will reduce the need for mechanical cooling. Therefore, the savings from cooling efficiency improvement measures will be reduced.

Assumptions

EDGE software uses monthly average outdoor air temperatures based on the project location to estimate the suitability of an air economizer for the project. If more accurate monthly average outdoor temperatures are available, they can be entered in the “Key Assumptions for the Base Case” section of the design tab.

Compliance Guidance

To demonstrate compliance, the design team must describe the specified system and provide documentation to support the claims.

Design Stage

Post-Construction Stage

At the design stage, the following must be used to demonstrate compliance:

Manufacturer’s data sheet for the air economizer specified; and
System schematics showing the location, brand and model of the air economizer.

At the post-construction stage, the following must be used to demonstrate compliance:

Updated system schematics;
Photographs of the installed economizer;
Purchase receipts and delivery notes for the economizers; and
Manufacturer’s data sheet for the economizers purchased.