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More fresh air means healthier buildings
More fresh air means healthier buildings. Building on EQp1: Minimum Indoor Air Quality Performance, this credit calls for exceeding by 30% the minimum outside air requirements set by ASHRAE 62.1-2004. This credit applies only to occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space. of the building unlike...
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11 Comments
30% over ASHRAE 62.1 or the more stringent local code?
You state above under "which code?," that only ASHRAE 62.1 applies to this credit and not the local code (as in EQp1). I'm requesting clarification because there is one sentence on page 312 of the 2.2 reference guide under "Mechanically Ventilated Buildings," that states "exceed minimum rates required by ASHRAE 62.1-2004 or the applicable local code, whichever is more stringent, by a minimum of 30%." In looking at the reference guide for LEED 2009, it looks like they have taken out the sentence that says 30% over local code and it clearly states 30% over ASHRAE. This makes me believe that the 30% over ASHRAE would suffice.
We are working on a project that is registered under NC 2.2 and it's in California where the local code,Title 24, is more stringent than ASHRAE 62.1-2004. We need clarity on whether the requirement for EQc2 is 30% over ASHRAE and/or local code or just 30% over ASHRAE. We’d like meet the 30% over ASHRAE to earn the credit, and not have to meet the 30% over Title 24 which would have a large impact on our energy efficiency.
Tom, I think you summarize things correctly. It's 30% above whatever is more stringent for v2.2, and 30% above ASHRAE for v2009. To my knowledge, you can apply the looser v2009 requirement to v2.2, however—that requirement has not been changed retroactively. However, has anyone had a different experience?
Increased Ventilation Calcs
We just received the following comments from the reviewer after providing calculations for the critical zones:
The LEED Submittal Template has been provided stating that the project has increased breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.12007) outdoor air ventilation rates to all occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space. by 30% above the minimum rates required by ASHRAE Standards 62.1-2004 as determined by EQp1.
However, two issues are pending:
1. It is unclear if all zones are receiving the outside air required since a mechanical schedule has not been provided.
2. A 30% increase in outside air for compliance of this credit must be provided at the zone level to ensure that breathing zone outside airflow is increased adequately. Note that a 30% increase of OA at the system level is not allowed since it does not guarantee a 30% increase at the zone level.
TECHNICAL ADVICE:
Please provide a mechanical schedule along with evidence that all zones are getting the required outside air, either by showing the critical zones or listing all zones.
Does anyone know if this means that we need to provide calculations for each zone? We did provide calculations for the critical zones. This has never been requested on previous projects.
Veronica - see my comment above. The reviewer gave clear steps for calculating the increase in OA required at the breating zone. I don't believe they want to see all the zones, but they want the OA requirement increased at the breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.12007), which in turn changes the ventilation efficiency Ev. My issue was there was no way to do this with the ASHRAE 62MZ, unless you have an unlocked spreadsheet. After some back and forth with my reviewer I was told to use the 62MZ spreadsheet but increase the system floor area by 30% to trick the spreadsheet into calculating the increased Vbz requirement. The reviewer later sent me the new LEED 2009 Retail sample form which has the proper calculation built into the form. I tried it out and it seems to work.
Increased Ventilation Calculation methodology
I recieved the following comments from a reviewer on how we should be calculating the 30% increase:
1. At the system level, the uncorrected outside air requirement for the system (Vou) must be multiplied by 130%.
2. For the critical zone, the outside air required at the breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.12007) (Vbz) must be multiplied by 130%.
3. For the critical zone, the zone ventilation efficiency (Ev) must be recalculated based on the revised values for Vou and critical zone Vbz).
4. At the system level, the total outside air intake required as a fraction of primary supply air must be recalculated using the new critical zone ventilation efficiency (Ev), and the new uncorrected outside air requirement for the system (Vou).
I have never seen this before, and have alway shown the percentage increase as a simple equation of (Provided OA-Required OA)/Required OA.
The only thing I can figure to do is manually adjust the Vbz number for the critical zone in the "Detailed Calculations" area which then adjusts Ev for the system and the total required OA Vot. Then multiply the new Vot by 130%. Does that make sense? Has anyone else had a reviewer ask for the calculation to be done this way? If so, where is the reference to it?
Nancy, the procedure described is correct. I think your interpretation is correct; different terminology is being used. You should focus on a 30% increase to Vbz values. For decoupled ventilation systems, the calculation is much more straightforward to demonstate. When dealing with a multiple-zone recircualting system (VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas.), the calculation becomes more challenging. I recommend having the project's mechanical engineer review the calculations.
Roger, I can see how this would result in better OA flow and is apparently the correct procedure - and yet this is not the procedure shown in the Reference Guide. In addition, the ASHRAE spreadsheet does not allow editing of the cells that would produce this calculation. How is it acceptable that design teams cannot rely on the guidance and examples provided?
Nancy, in the past, we've submitted stand-alone Excel spreadsheets documenting the ASHRAE 62 methodology in detail, rather than trying to show this within the letter template. The template is trickier to use with a building that has a lot of separate zones. Have you been using the 62 compliance spreadsheet developed by ASHRAE?
Yes we use the ASHRAE 62 compliance spreadsheet. We used it for the project referenced, however, in order to do the calculation they have asked for, we would need an unlocked ASHRAE 62 spreadsheet. We were ultimately told to increase the system floor area by 130% (and the zone popluation if not defaulted) to trick the spreadsheet into producing the correct cacluation. This means that separate forms are required for the prerequisite and the credit. We were also told that on V3 projects the ONLY form that has the correct calculation is the LEED-NC Retail. We were told to use the Retail sample form on our NC project and upload it separately. That worked mostly OK, but there is a bug in the form that will not allow use of actual occupants - only default. A mechanical engineer working on one of our projects told us he has been told by reviewers NOT to use the ASHRAE 62 spreadsheet on v3 projects, because the calculation is built into the form.
Increased ventilation with a constant volume system?
In a CV system the OA is distributed evenly & is proportional to the SA delivered to the space. The only way I can increase the OA to a given room is by increasing the SA delivered. Sometimes this is impractical - I am wondering if GBCI ever overlooks an OA deficiency in a given room when the total being delivered from the AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition) 2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork. exceeds 30%?
You can increase your fraction of OA for the entire system to raise your proportion of OA in a given room. Not a very energy efficient way of doing it, but it will meet the requirement.
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