Space exclusion from ASHRAE 62.1-2007

Take a look at Table 6.2 in the standard. That covers minimum exhaust spaces. Also, check normative Appendix E, Health Care.

I think you'll find most space types are covered.

Electrical equipment rooms have zero Rp and a small Ra rates.

Storage rooms and elevator machine rooms are included in Table 6.1 with zero Rp and double the small Ra rate of electrical equipment rooms.

Telephone closet are interesting. They have zero Ra and Rp ventilation requirements in Table 6.1, and are not included in Table 6.2 as exhaust spaces. Closets would fall under the same requirement. They seem to disappear.

Definitions for equipment rooms, closets and storage rooms are not included in ASHRAE 62.1. This is a problem, LEED-wise.

Unfortunately, you have to use your judgement defining what a space type is. This is where a LEED reviewer can chose to challenge you.

If you providing exhaust and claiming an equivalence per Table 6.2 you can defeat a review claim to provide ventilation but you will have to prove the proper exhaust is provided. Be prepared to include a definition for the class of air in an exhaust space. If the class of air is Class 1 then you'll likely get stuck with using an equivalent ventilation rate from Table 6.1.

I have always found it odd that LEED reviewers only question ventilation for Table 6.1 spaces and never question exhaust Table 6.2 requirements.

I also find it odd that, at least on my projects, reviewers never question the inclusion of restrooms and other exhaust spaces where the designer is providing ventilation air as part a multizone ventilation design: e.g. the same system providing OA to offices and restrooms. This does impact the amount of OA required but I generally see engineers exclude the ventilated exhaust space as if they did not exist. That isn't the right way to do it.

Hello Hernando. Would a kitchen in a hotel count as a regularly occupied space that has to be conditioned?

A kitchen is regularly occupied. It is an exhaust space per ASHRAE 62.1-2007 and is covered in Table 6-4 (0.7 CFM/SF or 3.5 L/sec/Sq. Meter).

Commercial Kitchens are listed as Class 2 air spaces. This means you can use makeup air from Class 1 space to condition the kitchen. This works just like a restroom exhaust and makeup system.

The exhaust rate is high. You might provide fresh air from your ventilation system to work around issues related to finding sufficient space for makeup ducts. It is okay to use a combination of makeup air and fresh ventilation air to meet the overall exhaust requirement.

Class 2 can be reused as return air to Class 1 spaces if it meets the requirements of 5.17.2 "Re-Designation" in ASHRAE 62.1 (90% dilution with OA). Be sure to read all of Section 5.17.

Also be aware of Table 5-2 which classifies air as Class 4 for grease hoods and Class 3 for other exhaust hood. It is likely you will fully exhaust all hoods rather than try to reuse the Class 3 air. Class 4 air cannot be reused/recirculated per the standard.

Thank You Hernando. The warming pantry is being exhausted per NYC Mechanical code. I understand that typically you would upload the ASHRAE VRP spreadsheet for regularly occupied spaces for each AHU. How is this typically documented for kitchens?

I should also say that if you decide to provide supply air to a space like a kitchen and it is part of a multi-zone system you have to include the kitchen as a space using the ASHRAE, LEED, or similar, calculation tool.

The best way to model this is as a space with 0.0 for the people rate (Rp) and 0.0 for the area rate (Ra). This will account for the loss of OA distributed to other spaces (Offices, etc.).

The LEED reviewers do no like spaces with 0 Rp and Ra because they think you are cheating the credit. This is only because the LEED tools completely ignore exhaust spaces. For a situation where an exhaust space is provided by normal supply air it is absolutely necessary to understand that the space is ventilated at a very high rate; exhaust @ 0.7 CFM/SF.

If you do not include normal supply air to an exhaust space the ventilation calculations will not be correct. Ignoring this makes the calculations assume that all of the supply OA goes down specific ducts in the distribution system and not down other duct runs. This is obviously not the way it works.

Jesus,

I would typically document this by not providing it for small spaes (restrooms, janitorial) as part of the submittal because it is not asked for, and it confuses the reviewers.

For a larger kitchen I would provide a special hand calulation upload with all of the exhaust requirements documented, not just the kitchen. Once you document one exhaust you should document them all.

Hernando,

In my opinion, zero value of Ra and Rp for class 2 space is not acceptable if class 2 space is under same AHU with class 1 spaces.
Once we set amount of OA for AHU, it will be mixed with RA to be SA.
The space set with zero value also has SA flow include any amount of OA.
So, this will occur underventilation of other spaces connected under same AHU with the zero valued space.
For the exhaust room;class2, it is better that ventilation rate should be same as other spaces:class1, not to make them underventilated.

Regards,

SangHoon,

Yes, but you should use zero for Ra and Rp. There is no fresh air requirement in ASHRAE 62.1 for class 2 spaces that are covered as exhaust spaces. This is the same case as using makeup air from class 1 spaces to exhaust rooms, such as restrooms. You do not provide, and are not required to provide, OA to such spaces. You are providing "used" air from a class 1 space.

And, no, setting the Ra and Rp in a mutizone system will not under-ventilate the other spaces served by an AHU. The floor area of the space will reduce the overall efficiency. Essentially, the space is treated as wasted OA that cannot be delivered to the exhaust room.