I have a very small elevator lobby, which has a little mini-split unit without outside air. It is the main entrance for an apartment building, and every time it is occupied, there will be an open door letting in large quantities of outside air. Tenants can literally only go from the elevator lobby to their own apartment due to lockouts in the elevator controls. Once they are there, the elevator returns to the first floor waiting for the next occupant. By the VRP compliance calculator in the IEQp1 Appendix, it would require 6 CFM of outside air to comply with IEQp1 and IEQ C2. I'm arguing for allowing this on two grounds:
1. IEQc2 Case 2 Option 2 Naturally Ventilated Spaces requires compliance for "at least 90% of occupied spaces". This space is about 0.4% of the building's floor area. All other spaces comply with mechanical ventilation +30%. Thus the requirement for "at least 90% of occupied spaces" is met.
2. Although the opening is not a window, the opening will be opened absolutely every single time the space is occupied, since people enter the space to get on the elevator or exit the elevator and leave the building. There are no chairs, waiting areas, or other reasons a person would be in the space for any time. (there will be, hopefully, a handsome LEED plaque which they may admire) A resident will almost always enter the front door, and walk right into the open elevator. A resident leaving the elevator will walk out the elevator door and leave the space. Such occupancy will always be brief, on average a few seconds. Thus the space will always be well ventilated whenever the space is occupied.
Do you think they'll buy this?
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 20, 2015 - 8:30 am
Could you define it as a vestibule? Does it qualify as semi-heated? In my opinion it is not a regularly occupied space. I don't see any IEQ reasons to either ventilate it (naturally or otherwise) or to provide views, etc.
Lawrence Lile
Chief EngineerLile Engineering, LLC
76 thumbs up
January 20, 2015 - 9:50 am
I'm with you, but the LEED reviewer doesn't agree. It is definitely heated. The LEED reviewer has already rejected us on a preliminary review, saying in her opinion the space does need ventilation. It has to be treated as a corridor or similar space. So there's no arguing our way out of it.
Argument 1 above, allows us to argue that the LEED standard requires 90% of the spaces to comply, and this is 0.4% of the space, therefore it doesn't have to. Argument 2 requires me to prove there is more than 6 CFM of ventilation when the door is open. I don't have a copy of the CIBSE standard, nor do I look forward to spending x number of hours figuring it out after buying it ... I wish there was a simple way to show that more than 6 CFM of air will pass throught he doorway every time it is opened. This actually seems quite reasonable, but I've got no numbers.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 20, 2015 - 10:48 am
If you declare it naturally ventilated, the ventilation openings (window, door, vent) must have openable area > 4% of the net occupiable floor area. Furthermore the door must be no further than 8 m (25ft) from the breathing zone.
Still, I would double read and refer to the definition of "occupiable space" in standard 62.1. The standard really is aiming at occupied spaces.
Lawrence Lile
Chief EngineerLile Engineering, LLC
76 thumbs up
January 20, 2015 - 11:52 am
Yep, Jean, we are good to go with the opening > 4% and the other rules in ASHRAE 62. I've developed a little spreadsheet that helps automate this calculation and will certainly turn that in. The problem I'm seeing is a little technical:
What I am stuck on is the 30% increased ventilation requirement to comply with IEQc2. In the IEQp1 Natural Ventilation template VRP Compliance Calculator, the area for documenting IEQc2 compliance requires me to input Voz. (the Voz number I need here is 6 cfm -just a puff).
The LEED reference manual, under IEQ c2 Implementation - Naturally Ventilated Spaces, p 447 in my edition directs us to use a "Macroscopic, Multizone, Analytic model ....such as ... ASHRAE 62.1-2007 Section 6.2".
Section 6.2 is for mechanically ventilated spaces. Is this a misprint in the manual? I just don't understand how to use a procedure for mechanically ventilated spaces to do anything with a naturally ventilated space. Nor do I see how to calculate Voz (I certainly know how to do this with mechanical ventilation per 6.2.2.3) in a naturally ventilated space, as required by the IEQp1 template. Voz depends on Ez, which is found in table 6-2, once again not applicable to ventilating through an open window. Since this is a prerequisite, and the reviewer has already flagged it, we've got one chance to get this right.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 20, 2015 - 12:12 pm
For increased ventilation credit you have to fullfill
1) Macroscopic, Multizone, Analytic model
If you read carefully, you will see that the simulation predicted ventilation rates don't have to match or exceed the 62.1 tables for mechanical ventilation. That is a myth. You have to proove that is is "sufficient" however, and that means that the credit intent to improve the IEQ of the space needs to be quantitively shown. How and what the benchmarks are, is actually open ended. This makes the simulation route really hard to do properly. You need to investigate a couple of worstcase days (wind, no wind, cold, hot) and normally at least provide a quantitive THERMAL comfort analysis. That should get you through, but IMHO you will find that DRAFT RISK as a measure of comfort (see ASHRAE 55) is the downfall of most naturally ventilated schemes and should be drawn into the criteria.
Lawrence Lile
Chief EngineerLile Engineering, LLC
76 thumbs up
January 20, 2015 - 12:42 pm
... or, argue that in an entrance lobby, everyone who is entering or leaving the building is dressed to go outside in whatever weather, and will also not be uncomfortable because they remain in the space a matter of seconds.
I'm pretty much in the dark as to how to do the thermal analysis you are alluding to, accounting for wind and so on. I can certainly use tables in ASHRAE 55 for a mechanically ventilated office, however figuring out how much air speed is in the space on a cold windy day with the door open isn't something I am familiar with.
Lawrence Lile
Chief EngineerLile Engineering, LLC
76 thumbs up
January 20, 2015 - 1:13 pm
So far, I'm planning to give it a shot with the arguments posted above, and also argue it is unreasonable to expect people who are dressed for the outside weather, and are in a space for a few seconds, will be uncomfortable. I'll post these arguments in Alternative Compliance. Although this building meets, as far as I can tell, the letter of the requirements for IEQc2, the amount of effort required to actually prove that is insurmountable. Thanks for your help so far, Jean, however I'm throwing up the white flag.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 20, 2015 - 2:04 pm
I think you are absolutely right. This is not an occupied space as per the 62.1 definition. It's not a hotel lobby. There are no seating arrangements or anything keeping people from staying in this space. 62.1 has zone types that are typically unoccupied for the case that they are occupied. But if they are not occupied, then they should not be considered. there are many verification clarification requests on the ashrae site to back that up.