What is ACH

18 years ago

Can someone make me understand that what exactly ACH means. Like during a design stage we always hear about certain areas to have certain specific ACH. Example - For an operation theatre, almost 15 ACH is needed. How should i take it.

On the other hand if i go by usual design procedures, i understand that against a certain cooling load i will have to provide certain CFM to the area, maintain a positive pressure in the area, induction of 100 % fresh air to the area (achieved by exhausting out all the air from the room instead of mixing it with the return of AHU. Now how can I verify / ensure that the area i have designed has got the required ACH as mandated by the codes. Thanks.

Sort by:Oldest

Comments (2)

udarrell_2007
18 years ago
Usually: ACH; is Air Changes per Hour.
THE LINK is, Ways to check delivered CFM airflow.
Can also be the air infiltration ACH, or fractions thereof. - udarrell

Here is a link that might be useful: Air Side of Air Conditioning
energy_rater_la
18 years ago
"i understand that against a certain cooling load i will have to provide certain CFM to the area, maintain a positive pressure in the area, induction of 100 % fresh air to the area"

100% fresh air sounds high to me. very high!
I usually use a 4 to 6" duct with a barometric damper
to introduce fresh air.
12"x12" filter back grill (usually in soffit..or patio/porch..) to clean the air before it enters the house.
I duct it to the return air.
We have to dehumidify here.

Ideally, we want several things
positive pressure
CLEAN air crossing the coil
COOL air entering the living space.

I've seen some crazy things...fresh air to supply
no filter @ fresh air intake.
Even ERV mounted on roof rafters...hottest place
to get make up air...

Everyone has their way of doing things,
but I have found this to work well and for a
minimal cost in my hot humid climate.

Best of luck!
Related Professionals
Selma General Contractors · Panama City General Contractors · Gaithersburg General Contractors · South Sioux City General Contractors · Middletown General Contractors · Carlsbad General Contractors · Cowansville General Contractors · Tulsa Home Remodeling · Modesto Home Remodeling · San Francisco Home Remodeling · El Paso Home Remodeling · Tulsa Bathroom Remodelers · Wheeling Bathroom Remodelers · Phoenix Bathroom Remodelers · Pueblo Bathroom Remodelers