ASHRAE 62-2001 8

[317069]

ASHRAE 62-2001, table 2 says 20 cfm/person in conference room, while table 6.1 says 6 cfm/person and both are for the same occupancy (50 persne/1000 sq.feet)
which one we have to use?

 

[MintJulep]

Maybe you should read beyond the tables. It's explained in the text.

 

[KiwiMace]

Neither. That standard is out of date and has been superseded several times over.

 

[Wilbur55]

Because the ventilation requirements for humans change every three years. It's nice to know that the ASHRAE standard is keeping pace with human evolution. The amount of fresh air needed by humans twenty years ago simply wouldn't do for today's the new and improved model.

 

[MintJulep]

Because the ventilation requirements for humans change every three years.

Because the materials used in building construction change, and the things that they out gas change.

Because our understanding of what is in the air we breath and how it affects us has improved.

Because building envelopes are tighter than 20 years ago, so the air brought in by the ventilation system is actually the only air brought in.

Because energy costs have increased and there is increased importance in providing the ventilation that is needed, but not more than needed.

Because the current ventilation standards have (at least some) basis in physiology, while the older standards were purely guesses or "this is what we've always done and it's been mostly ok".

 

[cdxx139]

Wilbur, maybe the indoor VOC levels have increased in 20 years. Maybe OA CO2 levels have increased in 20 years. Maybe laboratory testing has gotten better in 20 years?

Maybe it was wrong 20 years ago? Maybe its wrong now? And maybe it will still be wrong 20 years from now.

Its the best info we have with what we got.




knowledge is power

 

[317069]

Standards always are based on studies and the best knowledge at their time, they create it in labs and researches centers not in Time Horton cafe.
Table 2 is part of ASHRAE 62- 2001 while table 6.1 is not a part of standard but it says it revise air requirements of the procedure 6.1 which is the base of table 2,
so, this is like "summer and winter same time at the same place"
This conflict is in the same edition of the standard and there is NO 20 years between table2 and table 6.1.
any body have an idea how much the percentage of the sick buildings between the current time and 30 years ago with respect to the difference in buildings number.

 

[Hasni2]

I use HAP for load calculations and it says, for conference room you need to have 10 liters / second per person. Obviously it looks contradictory with what you have referred to, but most of the HVAC designers use this software and systems are running perfectly without any complaints.
Further I have a request to make, fellow professionals while responding to a query must try to be specific and talk more in a technical way than just guessing and speculating scenarios. Just a request. Thanks

 

[Drazen]

I understand criticism after Wilbur's comment, still there is a feeling that things change too often.

It is well known that knowledge base changes too quickly as well with increased interest in IAQ and green building, especially with increased understanding that those two concepts are found in conflict (some of the most advertised green materials have terrible VOC figures).

If I recall well, there was 2007 revision of 62.1 and now there is 2012 revision. Over the fact that designers are bit destabilized this way - we certainly do not memorize tables but we do get feeling of figures after increased use, so too frequent change of basic figures can easily cause errors - I am wondering how it will work in wider time range. Building sometimes need recommissioning, there are sometimes reconstructions and modifications of existing buildings, recertifications and with such pace of changes commissioning without capital investments will be very hard to achieve, which will eventually lead to avoidance on part of investors.

 

[KiwiMace]

It's not how much fresh air we need as humans, it's what is the minimum quantity of fresh air that we can stand.
i.e. before the following equation becomes true.
(healthcare costs + (downtime x salary level)) > cost of conditioned air

ASHRAE 62.x is a "continuous maintenance" standard, which means they release addenda as they think of them and compile a new version every three years.

 

[DRWeig]

62-XXXX is also filled with requirements that cannot be measured by any means available to a commissioning agent or mechanical inspector in an actual installation.

Kiwi, Mint, Drazen, Cdxx, and Wilbur all have very sound points, listen to them.

My opinion on the whole evolution of 62 follows. Feel free to skip it.

62 has morphed from a ventilation standard into a health standard over the years. Health standards should be issued by the AMA, NIH, OSHA, or somebody else who has lots of research doctors and scientists. ASHRAE, last time I looked, has only engineers.

ASHRAE standards should, in turn, specify the ventilation rates needed to comply with the medical standards and how to verify said ventilation rates at commissioning and inspection time.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[Drazen]

Current European norm is much worse. CR 1752 even avoids to provide any table, but gives generic procedure that more resembles scientific procedure than engineering work.

The concept is that designer should take all elements into account for each and every room on each and every project - all materials, all internal sources, precise determination of MET activities, 24 hour activity schedule (which should give cummulative intoxication load similar to cooling load calculation procedure)... completely useless for real-life design application except for large non-standard industrial processes.

Design should make the whole scientific elaboration to reach input for ventilation design. I would not have any trouble with that if adequate fees were provided to cover extra engineering work, that work should be 2 or 3 times more comprehensive than whole ventilation design work.

Even worse, sort of changes that looks minor in scope of whole building construction, like change of decision on carpeting, wallpapers etc. should easily make whole ventilation system obsolete in terms of this standard.

Desire to achieve formal preciseness is in direct conflict with real life here. The only reasonable approach would be to establish tolerances wide enough that would allow use of average levels at least for usual applications like offices, schools, libraries etc.

I believe normative bodies are reluctant to use such averaging approach for fear of getting into conflict with energy efficiency populists - every Watt of energy lost, every milligram of CO2 unnecessary released into atmosphere .. is "crime against planet earth", so everything needs to be perfect on paper without care how would it look like in reality.

In first days of energy efficiency talk I hoped it will give more weight to HVAC designers, but once politicians took over, many populist abuses took place and now I fear wide reluctance will grow in public over time, creating counter-effects. This may be something specific to monster-large EU bureaucracy.

 

[urgross]

Wilbur,

Maybe the CO2 calculations were made on a weight basis when coming up with outdoor air requirements. If you believe the US medical community, the US is in the midst, and apparently growing midst, of an obesity crisis. Bariatrics is definitely a growing field, pun intended.

 

[ChasBean1]

317069, 6 cfm per person with a contingency for square footage.

Drazen, I love your post. That is a 10 out of 10. Nice job.

 

[cry22]

My two cents remark.

5 CFM per person was the norm for years until the mid-eighties when the lawyers got into the action with the sick building syndrome frivolous lawsuits. So it went to 20 CFM/person in ASHRAE 62-1989 overnight with no study whatsoever.
Then the popularity fo VAV made it that we were close to 100% OA applications in winter for most systems, and we got into extensive freeze protection of heating coils, etc.
The green movement has brought it down, if it weren't for the lawyers, we would probably still be at 5 CFM/person.

 

[317069]

chasBean:
what did you mean by "contingency for square footage'?
do I have to add cfm/sq.ft to the cfm/personq?

cry22:
is there a proof that ASHRAE went up to 20 cfm without studies or reserches? I mean why 20, not 25 or 18

 

[ChasBean1]

317609, yes. Sorry but I have the table at my desk at work and not here. So it would be 6 cfm per person PLUS X cfm per 100 square feet. I'll be back to work Wed., will try to remember to re-post.