ASHRAE STD 90.1 IP
Energy Standard for Buildings Except Low-Rise Residential Buildings
|Publication Date:||31 March 2021|
When cost-effective, demand control ventilation (DCV) should be required for occupied spaces, considering the required outdoor air for ventilation based on number of people in the space, varying space sizes, use of energy recovery equipment, and climate zone. The current requirement has a threshold based only on space size and space occupancy. This proposal seeks to more effectively align DCV requirements with all other relevant variables to produce a cost-effective solution.
The single-threshold parameters are replaced by a table where the floor area threshold requirement is based on climate zone and occupant outdoor airflow rates per 1000 ft2 (100 m2) determined in accordance with ASHRAE Standard 62.1. The requirements are grouped by occupant outdoor airflow component ranges (cfm/1000 ft2 [L/s/100 m2]) based on default parameters in Standard 62.1. While the exact value for a particular space type varies, the three groups in the table generally correspond to (a) retail, break rooms, or bank lobbies; (b) classrooms or conference rooms; and (c) lecture halls, theatre, or assembly.
The exhaust air energy recovery exception was removed and replaced with higher floorarea thresholds in the table. The exception for design outdoor airflow less than 750 cfm was also removed, as this factor is accounted for in the cost-effectiveness analysis. One new exception was added to account for spaces that are not allowed to reduce outdoor airflow per the requirements in ASHRAE Standard 170, other applicable codes, or accreditation standards.
The net effect of these changes will increase the cost of construction. Because an economizer or motorized dampers are already required by this section, the cost to add a sensor and wiring is expected to be $300 or less per unit. A present value allowance of $63 is added to the cost to allow for replacement of up to 50% of sensor elements halfway through the measure life. The square footage thresholds in the table result in cost effectiveness for a 15-year life control measure based on a calculated discounted payback of less than 11.8 years.
Note: In this addendum, changes to the current standard are indicated in the text by underlining (for additions) and
strikethrough (for deletions) unless the instructions specifically mention some other means of indicating the changes.