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Baseline for outdoor air ventilation
This prerequisite establishes a baseline for providing a minimum amount of outdoor air to buildings in order to maintain good indoor air quality and keep occupants comfortable and healthy. This prerequisite references ASHRAE 62.1-2007 (with errata but without addenda) and is often more stringent than local building codes, although it is not likely to entail any added costs.
Two cases, both may be needed
The compliance paths for mechanically ventilated and naturally ventilated spaces, Case 1 and Case 2, are somewhat different and you may need to follow both paths for the same building. Naturally ventilated spaces must follow the distinct requirements set out in Case 2, even if other spaces in the same building are mechanically ventilated and are following Case 1. Mixed-...
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16 Comments
Ventilation for storage an mechanical rooms
Dear experts,
We are working on a university building wich has 2 underground floors, with mechanical and storage rooms in them, all these rooms are adjacent to the stairs. There are no means to provide natural ventilation to these rooms and they are not regularly occupied, only for inspections or maintenance. ASHRAE 62.1 - 2007, table 6-1, states "storage rooms" with it associated building component ventilation requirement, but in ASHRAE 62.1 - 2010, table 6-1, the definition is "occupiable storage rooms" and there is no occupancy category for unoccupied storage or mechanical rooms.
It doesn´t make sense to have a mechanical ventilation system operating continously in this rooms, considering the minimum 15 minutes occupation, the investment on duct work and air handler units, and the energy consumption of the system.
Are we forced to implement a mechanical ventilation system in these spaces? Should it be acceptable to implement louvers (dimentioned to comply with natural ventilation) in the partitions adjacent to the stairs to ventilate the rooms throught them, even tho the stairs don´t have mechanical or natural ventilation on these underground floors?
Thanks!
Rodrigo, this 62.1-2007 interpretation should be helpful. http://ashrae.org/File%20Library/docLib/Public/20100203_ic_621200717.pdf
It provides clarification regarding storage rooms.
Storage Rooms as a Critical Zone Using 62MZ Spreadsheet
I have received review comments from a LEED Review Team questioning the results of the 62MZ spreadsheet which identified a Storage Room as the "Critical Zone". The reviewer requests that I revise 62MZ spreadsheet indicating the "correct" critical zone. I have reviewed the imput cells in the spreadsheet and find no mistakes in the input values. The Storage Room which turned out to be the "critical zones" are large storage rooms within a relatively small air handling system. The outdoor air for Storage Rooms from Table 6-1 requires OA ONLY based on Area Outdoor Air Rate(0.12cfm/sq.ft.). No OA is required for occupants since space is normally unoccupied. Anyone else run across this or similar circumstance?? How do I effectively respond to reviewer given these circumstances?? I think providing a response that essentially tells the reviewer to read and understand ASHRAE 62.1-2007 and how results are determined when using 62MZcalc spreadsheet may not be well received.
Sometimes LEED review teams will question something that's not typical, even if the documentation is correct. Usually a conference room or other high density space will be the critical zone for a multi-zone system.
IAQ procedure
Has anyone had any experience with GBCI allowing the use of the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. procedure rather than the ventilation rate procedure?
We are designing a school with 58 classrooms and are utilizing air purification units that lower the amount of outside air needed and increase the efficiency of the system. This method is allowed by ASHRAE 62.1 through the IAQ procedure and is preferable to our project as we are located in the southeast where humidity is a problem. We can provide documentation that the indoor air quality levels are acceptable.
Thanks for your comments.
Chad, could you provide more information on the air purification units specified?
We have been wondering the same thing, Chad. We are located in Texas, where humidity is also (usually) a problem, and our project team has data that shows schools that used the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. Procedures are outperforming schools that used the Ventilation Rate Procedure in terms of indoor air quality. Results were measured by monitoring test scores and asthma inhaler use - the school using the IAQ Procedure had significantly reduced inhaler use and significantly higher test scores than the school using the Ventilation Procedure.
The ASHRAE 62.1-2007 User's Manual, p. 6-43, actually states, "The IAQP may also be used to achieve better air quality than the VRP (lower contaminant levels and/or higher perceived acceptabilty) with or withiout increasing first cost or maintenance cost." Yet LEED 2009 prescribes the Ventilation Rate Procedure, and the draft LEED 2012 prerequisite specifically prohibits using the IAQ Procedure.
Does anyone know the reason for this? Why does LEED prohibit using the IAQ Procedure?
Just found this credit interpretation ruling, which was published in 2007. However, please note, according to the CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide database, this ruling does NOT apply to LEED 2009 rating systems:
"LEED Interpretation
MPR/Prerequisite/Credit: IEQp1: Minimum Indoor Air Quality Performance
Posting Date: 5/15/2007
ID Number: 5053
Primary Rating System: New Construction v2.2
The CIR is inquiring if the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. Procedure, as described in Section 6.3 ASHRAE Standard 62.1-2004, can be used in place of the Ventilation Rate Procedure of the same Standard to document compliance with the requirements of this prerequisite. The Ventilation Rate Procedure methodology found in Section 6.2 of ASHRAE 62.1-2004 is the required approach in EQp1, since it is prescriptive and therefore more straightforward to apply. The Ventilation Rate Procedure is based on contaminant sources and source strengths that are typical for common space types listed in the Standard. The Indoor Air Quality (IAQ) Procedure methodology found in Section 6.3 of ASHRAE 62.1-2004 and proposed by this project team is performance-based and relies on identification of contaminants of concern, sources for those contaminants, concentration targets, and perceived acceptability targets. The project-specific nature of the IAQ procedure methodology makes it less commonly used and more difficult for USGBC to evaluate. Therefore USGBC cannot allow its use to show compliance with LEED NC v2.2 EQp1. Please note that the intent behind this prerequisite is to encourage designers to take the most stringent and conservative prescriptive approach to providing fresh air. The language of the prerequisite asks designers to compare the rates recommended under Ventilation Rate Procedure with that required by their local code and to pick the most stringent. As for the project team's legitimate concern with energy efficiency, the "additive" Ventilation Rate Procedure adopted in the ASHRAE Standard 62.1-2004 reflects concerns for energy consumption with elevated ventilation rates. The recommended rate under the Ventilation Rate Procedure in ASHRAE Standard 62.1-2004, in many important occupancy types and projects can result in lower ventilation rates than those required by the earlier version of the Standard - Standard 62.1-2001."
Infiltration, or Separate fresh air duct ?
Dear all,
I have an office room located inside a gymnasium space. The gymnasium is conditioned by an 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., while the office room has an FCU.
For the office room, fresh air is not provided separately through a dedicated fresh air duct. Instead, the exhaust rate in the office is higher than the supply, causing a negative pressure in the office, and consequently air will flow from the ventilated gymnasium towards the office through infiltration/cracks.
If this infiltrated air is proven to include the minimum amount of fresh air required for the office space, is this scenario acceptable, or a separate fresh air duct is required in this case? Please note that I have around 16 cases similar to this one!
Many thanks!
George, this is not permitted. You will need to provide a separate fresh air duct. The reasoning is that infiltration is uncontrolled and is not filtered.
Outdoor air flow and primary supply air flow
Dear all,
I have a 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. system for my school, with each 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. feeding around 25 zones (classrooms and offices).
Each zone has a maximum primary air flow and an outdoor air intake flow (specified as per ASHRAE standard 62.1).
Taking the example of 1 zone:
The minimum ASHRAE required outdoor air intake flow is 800CFM, and the Design zone primary air flow is 2000CFM. If the cooling load in this zone drops, being a VAV, the supply primary air flow may get down to 1000CFM. However, since the fresh air and the recirculated air are being mixed in the AHU, the fresh outdoor air intake flow for out zone will drop down proportionally to 400CFM, which no longer complies with ASHRAE requirements!
How do you deal with this issue? Do you think that the fresh air minimum requirement must correspond to the minimum design primary air flow? In this way, if the zone load increased, the design primary air flow will induce a lot more fresh air than required by ASHRAE.
Thanks for your help!
This is one of the weak points of 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. systems. In order to guarantee proper ventilation at all conditions, the amount of outdoor air that needs to be brought in at the air-handling unit can be significantly higher than what's required if you just sum up the ventilation rate required for each zone. This is why decoupled ventilation systems are now preferred, especially for schools. A dedicated outdoor air system handles delivers only what is needed for ventilation to each zone, typically at neutral air temperature. Space sensible cooling and heating is provided by a recirculating VAV system (dual-duct), fan coil units, radiant panels, chilled beams, etc.
Documentation requirements?
Does GBCI really require the template filled out? We have a spreadsheet exactly like your sample documentation documenting compliance, etc. This is for a school with over 150 spaces, and we'd just as soon not have to go enter 150 individual line items into the LEED template. Do they accept this means of documentation as an alternative compliance path, or are we forced to spend hours uploading this duplicative info into the templates?
Before LEED v3.0, we would submit our own spreadsheets with ventilation calculations and they were usually approved or we were given minor comments on adjustments to make during the review process. I think it is unreasonable to expect teams to completely duplicate this work on projects with a lot of ventilation zones. I would submit your spreadsheet, include a detailed narrative, and at least see what the review comments are. The worst outcome would be that they reject this approach and you then have to fill out the template. Please let us know what you end up doing and what the outcome is.
Dear Tommy & Roger,
Any reviews from the USGBC regarding submitting one's own spreadsheet?
Thanks!
We contacted GBCI and their help forum said we could submit our own spreadsheets. We did so in our design review response (after they initially rejected the submission w/o the info in the template). But with a copy of the email and clarification on the spreadsheets, they accepted it! Saved many, many hours of copying the same information into the template!
Here is the actual response we received (of course with the caveat that the following text represents staff opinion of a particular issue, and does not set any precedent, etc, etc:
The project team is inquiring as to whether or not providing a supplemental spreadsheet that contains the Ventilation Rate Procedure calculations for each zone under each outside air unit in lieu of completing the table on the LEED prerequisite Form is an acceptable alternative compliance path. This approach to the prerequisite is acceptable, so long as the supplemental calculations include all of the required information outlined in the LEED Prerequisite Form. Note that the form itself must contain all other required information, save the table calculations, in order to demonstrate prerequisite compliance.
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