Rating System

LEED BD+C: New Construction, LEED BD+C: New Construction, LEED BD+C: New Construction, LEED BD+C: New Construction, LEED BD+C: Schools, LEED BD+C: Schools, LEED ID+C: Commercial Interiors, LEED ID+C: Commercial Interiors, LEED BD+C: Core and Shell, LEED BD+C: Core and Shell

Rating System Version

v2 - LEED 2.0, v2 - LEED 2.2, v2 - LEED 2.2, v3 - LEED 2009, v2 - Schools 2007, v3 - LEED 2009, v2 - LEED 2.0, v3 - LEED 2009, v2 - LEED 2.0, v3 - LEED 2009

Inquiry

Activated Carbon Filters for Low-Cost Demand Control Ventilation and Energy Efficiency This CIR proposes an innovation design credit for a suite of design features and a design procedure that will reduce the cost of demand controlled ventilation (DCV). The procedure is based on a combination of: scrubbing the air with activated charcoal (AC) filters to reduce the number of critical rooms in a building that will require CO2 sensors; using air-to-air heat recovery for the building air: using time-of--day control of ventilation for the building zones. The proposed design procedure will enable selecting the minimum number of CO2 sensors to control the amount of delivered outside air. This will reduce the initial cost as well as the annual cost of maintaining their calibration. The new Pacific Garden Mission building in Chicago will house an average of 800 homeless people on any given night. The design calls for using activated carbon filters in the main air handling unit for the entire building to help control the peculiarly strong body odors of the guests and to reduce the required outside air and associated energy use. Three "hot boxes" will also be used to disinfect by 180oF+ heat all the clothes of the incoming guests as part of the thorough laundry process. The activated carbon filters are capable of reducing these outdoor air rates by over 70%. This was determined by applying the Indoor Air Quality procedure described in Section 6.2 of ASHRAE Standard 62-1999 Ventilation for Acceptable Indoor Air Quality1 To be conservative, we will assume that only a 50% reduction in outside air will be feasible because additional outdoor air may be necessary to control body odors by dilution. Besides reducing the cost of conditioning the ventilation air an additional benefit of the activated carbon filters will be to help reduce the number of CO2 sensors needed in the building for effective and affordable demand control ventilation. By reducing the required outside air by 50% the number of "critical rooms" is reduced. We define "critical rooms" as the rooms having a required minimum fraction of outside air, say 0.50, as calculated using the Ventilation Rate Procedure for multiple spaces and the Indoor Air Quality Procedure in ASHRAE 62,2-20012. The rationale for not installing CO2 sensors in rooms with outdoor air fractions below a specific number, say 0.50, is: 1. if regularly occupied rooms with outdoor air fractions above 0.50 are getting sufficient outside air, the rooms with lower fractions should automatically get sufficient outside air. 2. one air handling unit serves the entire PGM building. Therefore, a small number of CO2 sensors can control the outdoor air fraction throughout the building. (The air handler is equipped with multiple fans--their redundancy makes it acceptable to serve a building this size, approx. 118,580sf net interior floor area with one air handler.) 3. The design will also include air-to-air heat recovery at the main air handling unit using either run-around-coils or heat pipes. 4. For major parts of the day CO2 sensor control of the supply and outside air quantities for particular space will be overridden by direct time-of-day control by the central EMS. The building program is arranged so that during the daytime the lower two floors will be occupied and conditioned for occupancy. The upper two floors are dormitories that will be unoccupied and their environment will be kept at unoccupied settings, including just enough supply air to slightly pressurize these floors relative to the outside. Conversely during the evening hours, the lower two floors will be unoccupied and their environment will be kept at unoccupied settings with the minimal required supply air to temper the space and control building pressurization. The central EMS will be used to control the supply air to these large blocks of the building. (This will also allow using a very low diversity factor to size the main air handling unit since it will be used to condition about 1/2 of the building at any one time.) 5. The limiting factor in determining the minimum acceptable amount of outside air may very well be the perception of odors by the occupants. This may require higher amounts of outside for dilution of odors than what would be called for by the CO2 sensor. This will be determined empirically after occupancy begins. In summary, the above design features and program requirements make it possible to reduce the number of CO2 sensors at this job by at least 50%. This will be documented in the summary table of the Ventilation Rate Procedure analysis. As such, the use of activated carbon filters makes demand controlled ventilation economically viable. Our first question is whether the above package of design features and approach is acceptable for reducing the number of required CO2 sensors and the cost of DCV and whether this would be considered an Innovation in Design and suitable for receiving a a LEED credit. Our second question is whether we can calculate the energy savings due to the activated carbon filters using the same analysis method approved for demand control ventilation. The % reduction due to the DCV would be calculated by subtracting saved energy from DCV in the numerator and using the Base Case energy cost without DCV in the denominator. Our preliminary energy modeling indicates annual savings of at least $10,000 per year or about 5% of the projected energy costs of the Current Design. These savings would be included under EA Credit 1 Optimize Energy Performance. We look forward to the USGBC\'s comments on this potential innovation in design and on the savings calculation method for the activated carbon filters. 1. ASHRAE 62.2-1999 Section 6.2 and Appendix E 2. ASHRAE 62.2-1999 Section 6.1.3.1 Ventilation Procedure for Multiple Spaces