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Fresh air and energy savings
Outdoor air delivery monitoring ensures that the ventilation system, whether natural or mechanical, provides enough fresh air to occupants. The credit requires carbon dioxide (CO2) and outdoor airflow monitors that signal when fresh air is needed according to minimum set points defined by ASHRAE 62.1-2007. Typical ventilation design (without monitors) tends to encourage increased ventilation that may result in increased energy use and added cost for conditioning increased amounts of outside air. However, the addition of sensors and monitors allows ventilation to be delivered on demand only when required, potentially saving a lot of energy during unoccupied hours in spaces with varying occupancy.
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12 Comments
Non-Densely Occupied Spaces Served by Existing AHU
If you have non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person)." served by an existing 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., how should the outdoor airflow measurement be handled?
There is no baseline for when an alarm should occur on the ventilation air since not all spaces are within the LEED scope and no minimum ventilation rate has been calculated via 62.1.
On our specific project, there are 10 floors served by multiple 100% outside air units. We are doing work on a very small portion of multiple floors. The units are not within our scope of work. Short of adding an alarm to each valve providing airflow to each renovated space, which would get very costly very quickly, what would qualify for this credit?
We have no problem meeting the CO2Carbon dioxide sensor portion of this credit.
What you have going for you is that the units are providing 100% outside air. That is much easier to monitor than minimum OSA fans. However, you would likely need an airflow station and alarm (or control wiring to a BMS) at each OSA entrance in order to satisfy the credit.
Demand Control Ventilation
I have a small TI project with 14 small rooms (<100sf, 4 or less people per room) and it seems ridiculous to have to buy expensive C02 stats that will save minimal energy and won't affect the OSA to the space. I have CO2Carbon dioxide stats and DCV in the larger conference rooms.
Title-24 (containing the Mechanical Code in California) has exceptions to the need to have C02 sensors in small rooms with a design occupancy higher than 25 people/ 1000 SF (Spaces with an area less than 150 SF, or a design occupancy of less than 10 people are exempt).
Why doesn't LEED allow this type of exception. Do they?
Quote from the Non-Res Compliance Manual code:
"The fourth exception recognizes the fact that DCV devices may not be cost effective in small spaces such as a 15 ft X 10 ft conference room or space with only a few occupants at design conditions."
Your argument is reasonable, though LEED has no exception for densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person). with less than 10 people. You can attempt the credit selecting alternative compliance path on the LEED credit form. Acceptance of this approach depends on the GBCI reviewer's discretion and how strong a case you make. Alternatively, you can submit a project 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 but note that the GBCI website states, "... the credit language nor the minimum achievement thresholds can be changed through the Project CIR process." It is hard to say whether you will have success with either of these approaches.
Automated control
I notice the credit language here requires an alarm when CO2Carbon dioxide levels are more than 10% above desired. We're installed our system to be automated, immediately kicking up air intake when the level increases. I believe this fulfills the intent of the credit, but may not match the language exactly. Has anyone experienced this before, or have an idea what we should expect from the reviewers? Thanks very much!
Max, I believe this would qualify—"alarm" doesn't have to mean bells and whistles going off.
Outdoor Air delivery monitoring with increased ventilation rate
How does the alarming system work if the project is attempting IEQ credit 2, wherein 30% extra fresh air is provided? Does the set point then change to the designed fresh air quantity & then trigger alarm if the quantity deflects by +/- 15%?
The credit language ccalls for the set point to be the "Design values." So if your design has higher ventilation rates, that would be the relevant threshold.
Outdoor Air Delivery Monitoring System installed post-occupancy
Our building owner is having a building-wide outdoor air delivery monitoring system installed throughout the building (not just in the LEED-tenant area of our project) but it won't be installed in our tenant space until about 3-months post occupancy.
Can this still count?
I think you would have to submit as an alternative compliance path and hope for a positive response from the reviewer. Seems to me like it meets the intent.
Not sure if this is practical, but could you delay your final application until three months post-occupancy and document it in the regular fashion?
Do I understand correctly that if we have outdoor air delivery monitoring on each of 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. in the building then there is no need to separately monitor the air flow to the CI space we are fitting out?
If the base building 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. is monitored and you know for example it has 15% outside air. Then you can assume the amount of air delivered to your CI space also has 15% outside air. You may want to monitor or at least balance the airflow to your space to ensure that it is adequate.
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