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Hospital HVAC Design

Hospital HVAC Design

Hospital HVAC Design

Can anyone please advise me how to find a good source for learning fundamentals of hospital HVAC design?

Thanks in advance,

RE: Hospital HVAC Design

What state or province are you in?

RE: Hospital HVAC Design

in a nutshell:

all systems are constant volume reheat

no duct liner

solid double wall units

ducted returns

75 cfm differential for + and - spaces ..... use aia guidelines to determine what room requires

some states have their own guidelines ..... like florida

RE: Hospital HVAC Design

Oh no, respectfully, I disagree with the nutshell description.

First: CV reheat is a violation of ASHRAE 90.1. Reheat can be used only if recovered heat or part of a system reuiring a reheat process.

CV reheat was old school. we do VAV all the time, even for rooms requiring CV applications due to min ACH requirments. The VAV is great to maintain your isolation room pressurization especially during testing and balancing.

It is anything but a nutshell, you've got serious filtration requirements, invasive/non-invasive procudure rooms, nuclear medicine and lead lining, accelerators, ICU/recovery rooms, LDRP's, bone marrow transplants, morgues, biosafety lab hoods exhaust requirements, operating rooms with laminar flow diffusers, research labs, high supply low return/exhaust requirements, and on and on...

Then you've got a clientelle that is paranoid about contamination, triage, TB or AIDS patients, humidifications requirements, decontaminbation rooms, sterilization of equipment, coordination with medical planner and use careful reading of materail safety data sheets. You need steam year around in hospitals, programs that change with populations age and types of deseases evry 5 years, HVAC systems must accommodate future change in programs without disruption, etc...

Try to renovate an ER suite while maintaining full operation of ER and you'll learn something about serious utility phasing.

You need to read that VA guidleines at least 10 times to get just a grasp of what Hospital design is about AND be in a serious place with healthcare practice where you do nothing but hospitals.
A lot of people do MRI suites here and there and call themselves Hospital specialists.

And you've got some serious fast track projects, hospitals want an 9-month turn around on a project from NTP to occupation, every day is a high billing day in hospitals.

Good luck.

RE: Hospital HVAC Design

Don't forget, as atlas06 said, the code is the AIA healthcare design guidelines. Airhandling units must have 90% final filter downstream of the supply fan. Air intakes must be minimum 25' from exhaust. Also outdoor air intake must be mi nimum 3'-0" above the roof or minimum 6'-0" above the ground. The AIA healthcare guidelines list the design indoor range of conditions for different rooms. also minimum airchanges of supply or outdoor air for certain rooms. The minimum turndown volume for VAV systems should not be lower than the minimum. A ventilation shedule proving the AIA healtcare guideline ventilation are met would be required.

RE: Hospital HVAC Design


all new healthcare projects are cv reheat ..... vav boxes set to constant cfm

with vav you cannot maintain pressure relationships

better think thru that again

large healthcare is the vast majority of my work

RE: Hospital HVAC Design

So, how do you maintain a positive or negative pressure in a building in an isolation room when the door is open? with VAV, you can accomplish it, not with constant volume.
some boxes are 100% air of course, but with VAV, you can modulate your supply down and maintain the pressure requirements.

If you have an OR suite, 6 plus OR's you would be wasting energy like hell when you only use one OR.

RE: Hospital HVAC Design

the door to the isolation room is closed in design

show me where cv reheat is in violation for healthcare

RE: Hospital HVAC Design

ASHRAE 90.1 does not allow CV reheat unless it is recovered heat.
The HHS does care about the design, it cares about the operation of teh system.
Aside from all that, with the exception of some specific rooms that  require min. ACH, the remainder of the building has similar operation to office buildings, a CV systems is a waste of energy.
We do this all the time, and I have seen several healthcare design firms' drawings, they all use the same approach. i.e VAV

RE: Hospital HVAC Design

OK mr. CME, you got doing a code research for you.
It looks like your company is too cheap to buy you a copy of ASHRAE 90.1, since you could not look it up.
Any way, see ASHRAE 90.1 6.5.2, the only reheat allowed for your hospital application is for rooms requiring min ACH, i.e. isolation rooms and the likes. You are not allowed to have CV reheat per 6.5.2 for the remainder of the hospital unless 75% of the heat is  recovered heat.

RE: Hospital HVAC Design


you are one arrogant person who recommends his own threads as helpful

you are incorrect in your statements

RE: Hospital HVAC Design

ashrae 90.1-2004 exception b

i would cringe on using vav regarding infection control

RE: Hospital HVAC Design

Never insult someone without getting the facts.
I did not give myself stars, I don't give a hoot about stars, besides, from what I know the system does not allow it. The problem comes from the web host, somehow it copies whatever stars were given to the first thread, I did notice that, as soon as I post a reply, before anyone reads it, the darn thing displays as many stars as were given prior to that post.

May be others have had this same issue, and I hope that they will attest to my statement. I am not in it in this forum for stars my friend, and I do understand you reaction, so I will not insult back, I will just beg on the web site host to please tell you that I did not give myself stars.

I have learned from this site, and I am giving back my knowledge to this site, I do not intend to take my knowledge to the grave.

Back to our discussion, no one says VAV for infectious rooms, those rooms require 12 ACH at all times regardless, what I am saying is that VAV allows you more leeway in dealing with building pressurization and air balancing and energy savings of course.

Now, let's hope that I will get any more stars.

RE: Hospital HVAC Design

Sorry cme, the damn site loves me, it just won't let me post anything without issuing me a few stars.

RE: Hospital HVAC Design


Once you get the stars for a post, then they will appear automatically on all your previous and succeeding posts, but your total star count remains unchanged.

The basic idea of these forums is to share what we know and learn what we don't. As working engineers, we all have expertise in some areas and may have only clues in other areas. That doesn't necessarily mean we are totally useless. You both displayed excellent knowledge and experience in past threads. Please stop flamewars and apologise each other, as gentlemensmileWe can get more by that.

RE: Hospital HVAC Design

12 ach isn't enough for isolation rooms ..... min 15 ach ..... and w/ 150 cfm differential ...... sealed walls/windows ..... and door w/ tight gasket

as far as insulting ...... the way you can across .... ok mr cme ..... that doesn't sound professional at all

RE: Hospital HVAC Design

Insults are interpreted differently, cultural differences I guess.

AIA recomends 10 ACH for Isolation rooms (page 130), some hospitals require 12 ACH, but I have never seen 15 ACH, that being said, some hospitals do require more stringent requirements than codes.

Now back to VAV systems: See AIA page 118.

RE: Hospital HVAC Design

The 2006 AIA Guidelines for Helth Care Facilities now require minimum 12 ACPH total air changes for isolation rooms and protective environment rooms. Isolation alcove or anterooms require minimum 10 total ACPH.

VAV systems are allowed but flow shall not be stagnant nor be less that the minimum tabulated in Table 2.1-2. Constant volume airflow is required for consistent ventilation in protected environment and isolation room. It is now not acceptable to have rooms with reversible airflow provision for switching between protective environment and negative isolation rooms.

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