We received a LEED review comment regarding Warehouse ventilation to comply
with ASHRAE 62.1-2004.
Generally depending on the warehouse storage, MEP team recommends 5-8 Air
Changes per Hour by thumb rule for exhaust and air intake is assumed by
infiltration by windows, open doors etc.. But this number I haven't find in
ASHRAE, please give me reference.
ASHRAE 62.1-2004, Table 6-1 for warehouse category says to have 0.06
cfm/ft2, is this number defines to intake or Exhaust? If it is exhaust, it
is too small as volume of warehouse will be high.
Please share your ideas to comply with the requirements.
Thanks & Regards,
Ashraf
Ashraf,
ASHRAE 62.1 is concerned with people, who need ventilation (supply /
intake). For typical buildings, you may not need separate exhaust fans,
because that amount can probably exfiltrate through cracks. Supply and
exhaust fans can be used in tandem if the building is fairly tight (no
leaks).
Your MEP team's 5-8 air changes per hour is for cooling, not ventilation.
Any building with which has that much infiltration is closer to a tent than
a building! (It's not closed up.)
James V. Dirkes II, P.E., LEED AP
Hello James,
I accept that ASHRAE 62.1 is concerned with people, the same we explained to
LEED Reviewer team, this is the comment we received,
However, since the project uses ventilator fans it is considered a
mechanically ventilated space. Additionally, the LEED-NC v2.2 IEQp1 CIR
ruling dated 10/8/2008 states that unless the mechanically ventilated
warehouse has no human occupancy except for maintenance and repairs it must
meet the requirements of ASHRAE Standard 62.1-2004. The narrative states
that the warehouse will be occupied for the loading and unloading of goods;
therefore, the warehouse is regularly occupied.
Provide calculations for the warehouse space demonstrating that the space
complies with the minimum requirements of ASHRAE Standard 62.1-2004.
I am not having any idea how to convince the team.
Thanks & Regards,
Ashraf
Ashraf,
It seems that all you need to do is demonstrate that your ventilation system
complies with Table 6-1. Are you introducing at least .06 cfm/sq.ft of
outdoor air with the mechanical ventilation system?
If so, just document it! If not, you're in trouble and will need to provide
a ventilation system.
James V. Dirkes II, P.E., LEED AP
James,
If we introduce 0.06 cfm.sqft, of outdoor air, if it complies with ASHRAE
requirements, then we can do that. Normally all warehouses here will be
having ventilators to exhaust air which is assumed that air intake by
infiltration.
Also project is located in DUBAI, UAE. Climate here is very hot and humid;
if I introduce outdoor air it will affect the storage materials in the
warehouse.
Did you know where can I find the exhaust rates, such as Toilets, Generator
Room, pump room in ASHRAE?
Thanks & Regards,
Ashraf
?Toilet room minimum exhaust rates are shown in Table 6-4 or Standard 62.1-2004 (sub-notes D and E.)
A side note: Eight (8) air changes per hour translates to 2.67 cfm/sq.ft. if we a assume ceiling height of 20 ft. This definitely sounds like a recommendation for cooling and not just ventilation.
Larry O. Degelman, P.E.
Dear Ashraf,
Think about it. If you exhaust X cfm, where does the infiltration come
from? Outdoors! So you are already introducing hot humid Dubai air into
the building. A (supply) ventilation system does the same thing as an
exhaust-with-infiltration system; it pushes instead of pulls. As long as
the fans actually move the same amount of air, the end result is similar.
(The actual mixing within the space is generally better, though, for a
supply system.)
ASHRAE 62 is not confident that the infiltration actually occurs (the
building can be constructed very tightly), so they generally want you to
have a supply system . As I think about it, I don't think they require an
exhaust fan, but id the air is introduced, there must be adequate leaks,
louvers or exhaust capacity to let it out.
0.06 cfm / sq.ft. is not much. For a 30ft tall warehouse. 0.5 cfm/sq.ft.
results in 1 AC/hr., so 0.06 cfm/sq.ft. is around .12 AC/hr (if the
building is 30 feet tall). This amount of air certainly won't affect your
indoor environment noticeably if your exhaust system is 5-8 air changes!
It's possible that LEED will buy an explanation which discusses why you can
be confident that the exhaust fans are providing good ventilation because:
. They are properly spaced around the floor area
. Operate continuously whenever people are present
. Move the correct amount of air because there are louvers or other
means to make sure the air can get into the building
Good luck! It sounds as though you really have good ventilation, but need
to make LEED confident about how you are doing it.
James V. Dirkes II, P.E., LEED AP
Hello
Does anyone know if there is any recommendation for ventilation levels
of (large) rooms lodging the water reservoirs for the fire columns in a
residential building?
Thanks
FMS
The requirements of ASHRAE 62.1-2004 and 2007 are setup in both a
per-person rate to account for respiration-induced IAQ contaminants as
well as per-area rate to account for room contents (furniture,
materials, etc) induced IAQ contaminants. The warehouse only has to
cover the per-area rate since it is assumed to be non-regularly occupied
or have such a low occupant density that it does not impact the overall
need for outdoor air. I'm not certain what the reviewer's specific
comments were, but my guess is they did not see what they were expecting
to see for ventilation. They will not generally comment if the
ventilation rate exceeds ASHRAE requirements by a large amount, however.
There may be other reasons to have a high ACH for warehouses: the
materials stored, etc. 5-8 ACH is excessively high for cooling needs
also and you'd probably be better off air conditioning at that point
(haven't analyzed it specifically, but fan power consumption is related
to volume in a cubic function, meaning each 10% increase in supply
volume requires 33% more power. Warehouses typically have either a
positive pressure design or a negative pressure design - yours using
exhaust fans is a negative pressure design. For Dubai, a positive
pressure design using supply fans with exhaust louvers (instead of the
opposite) would likely make more sense: less energy to keep the warm air
out than to cool it down once it gets in.
Since the project is in Dubai, don't forget the mandatory Chapter 4
rules in ASHRAE 62.1 on outdoor air cleaning. If the outdoor air does
not pass the U.S. EPA air quality standards, then outdoor air quality
must be addressed on any outdoor air used for ventilation purposes.
Particulate will likely be a significant problem. This does tie in to
other LEED credits, particularly EQ Credit 5 (LEED-NC and LEED-CS
projects) which requires MERV 13 filters on all outdoor air intakes.
You may want to take a step back from the review comments and
re-evaluate design intent for the warehouse. Asking questions like
"what will be stored in the warehouse?" and "how often will it be
accessed for inbound/outbound shipping and putaway?" will help you
figure out what the space needs for ventilation and temperature control.
Then, you can factor in the ASHRAE requirements and bump up the areas
where your design intent does not reach the levels necessary. Good luck
on the review!
Jeremy R. Poling, PE, LEED AP+BDC
Hello Ashraf,
?
If you are reffering to a storage rooms,chemical Minimum exhaust rate is 1.5 cfm/ft2 as per ASHRAE 62.1-2007, Table 6-4.
Hope this helps.
Cheers,Sasa
?
Hi Jeremy,
In the Gulf region, sand trap louvres are being used at intake side. The sand trap louvre is designed to separate large particles at low air
velocities,minimizing excessive dust loading of conventional
filters.Think of it as a pre-filter for AHU.
Thanks,Sasa