We working on a industrial building where there is an unconditioned dining area for factory workers.
This dining area is provided with roof mounted exhaust fans. All exhaust make up is fresh air, that comes through windows and the louvers on the walls. Make up fresh air coming through windows and louvers are well above the ASHRAE minimum ventilation requirements, if make up air flow rate is assumed to be equal to the exhaust air.
However LEED review team says that this won't qualify for mechanical ventilation. Pls note their comment below.
" For spaces that only receive outside air indirectly as a result of makeup air pulled from openings in the building envelope, the project must meet the natural ventilation requirements. Note that the mechanical ventilation compliance path is only applicable to spaces that receive outside air directly from mechanical supply units."
Is this comment correct?
If yes, can we assume the amount of fresh air come through the windows is equal to exhaust air flow rate? or do we have to show the proximity to the windows?
kindly advise..!!
Hernando Miranda
OwnerSoltierra LLC
344 thumbs up
March 19, 2013 - 11:42 am
The reviewer seems to believe your makeup air is not all fresh air. From the ASHRAE 62.1-2007 definitions:
"air, makeup: any combination of outdoor and transfer air intended to replace exhaust air and exfiltration."
If the louvers are not "transferring" air from a space that is mechanically ventilated and it is indeed "fresh" outdoor air you need to explain that. Don't use the word makeup air.
If you are using air transferred from another space it is "used" air, and no longer fresh. Read ASHRAE 62.1-2007, Section 5.17, which describes the four classes of air "leaving" a space the air was used in, and also what you can do with air you are reusing a second time for ventilation. Table 6-1 identifies the class of air (air class) exiting specific space types.
Note that Class 1 air can be recirculated or transferred to any space. Class 2, and 3 air cannot be recirculated or transferred to a class 1 space. Class 4 air cannot be reused and must be 100% exhausted.
Chinthaka Jagodaarachchi
1 thumbs up
March 19, 2013 - 12:42 pm
Hi Miranda,
Thanks for your detail answer.
After the preliminary submission, review team ask us to clarify how would exhaust fans provide fresh air to this particular area. in responding, we submitted a narrative along with a sketch explaining that this particular area draws only fresh air as make up air from the windows of the building.
Review team has now requested mid review clarification with the comment that I posted with my first comment. if you go through that comment carefully, it is clear the reviewer knows that make up air is fresh air. And he claims that the mechanical ventilation compliance path is only applicable to spaces that receive outside air DIRECTLY from mechanical SUPPLY units. Further he claims that if makeup air is pulled from openings on the envelop, the project must meet the natural ventilation requirements.
Is there any clause in ASHRAE that says mechanical ventilation compliance path is only applicable to spaces that receive outside air DIRECTLY from mechanical SUPPLY units?
if not how we should reply? we have already explained the review team that the make up air is 100% fresh air in responding to clarification sort during preliminary submission. thanks.
Hernando Miranda
OwnerSoltierra LLC
344 thumbs up
March 19, 2013 - 1:27 pm
The reviewers should not call fresh air makeup air. ASHRAE 62.1 is very specific that makeup air is air that has been previously used in a space and might be reused to provide ventilation.
Tell the reviewers you have a 100% OA condition. Windows are being used in lieu of ductwork to provide the air. Call your fans ventilation fans and not exhaust fans. Because you have fans you are not providing natural ventilation. You are providing mechanical ventilation. You should only call a fan an exhaust fan if it is listed as a exhaust space in ASHRAE 62.1, Table 6-4. A dining space is not listed in Table 6-4 but it is listed in Table 6-1.
Now that you have explained to the reviewers that you do not have a natural ventilation condition, and that your fans should be ventilation fans and not exhaust fans to meet ASHRAE 62.1 requirements, you can use the 100% OA option in the LEED template to determine if the ventilation provided meets Table 6.1 requirements.
Hernando Miranda
OwnerSoltierra LLC
344 thumbs up
March 19, 2013 - 1:45 pm
By the way, the reviewer responses are generally pre-written comments provided by an entity (the USGBC's LEED Department) that does not do actual LEED reviews. The reviewers are forced to provide certain comments to maintain "consistency" across reviews.
The reviewers might be forced look for natural ventilation as part of the response. ASHRAE 62.1 does not describe a calculation method for stack flow ventilation, which is what exhaust in a ceiling with windows and louvers would be. EQ Credit 2 also does address stack flow ventilation using CIBSE AM 10 but it does not address fan-assisted stack flow ventilation.
In other words, there is no natural ventilation calculation method provided by ASHRAE or the alternative CIBSE for fan-assisted ventilation conditions. You might want to think about this and decide whether to explain this to make sure the reviewers do not try to use natural ventilation as reason or denying the credit because natural ventilation calculations were not used.
Kathryn West
LEED AP BD+C, O+M, Green Globes ProfessionalJLL
154 thumbs up
June 25, 2013 - 11:48 am
what ended up happening with this?