Small Space Ventilation

[carlosgw]

A small interior room that needs ventilation - say 50CFM. What methods would you consider to provide ventilation?

 

[LSA]

Without knowing too much about the specifics of the room, I would recommend using a small cabinet fan to take the exhaust to the nearest exhaust main or to the atmosphere.

 

[willard3]

If you take it out, you should put it back in.....what do you know about system balance?

There is really not adequate information for design.

 

[carlosgw]

You're right.
heating only, 0F outside air and 70F inside.
Exhaust is easy. I am assuming that drawing in air from adjacent spaces in not adequate ventilation.

 

[willard3]

If you just exhaust 50 cfm, it will come from somewhere.

If your syatem balance was equal SA and RA to start, you will now infiltrate 50 cfm of 0F air on a cold day with only an exhaust fan, or not if the building is tight.

50 cfm exhaust will make the room and building negative and you may take air from a space with worse problems than the room you are exhausting.

Still not enough information for design.......

 

[KenRad]

carlosgw,

What kind of room is this small room? If it is a bathroom, then transfer air from the adjacent space is permissible according to the International Mechanical Code (2000). This air must be exhausted from the building.

If this isn't a bathroom, then I'll assume you're talking about a 50 CFM outside ventilation air requirement based on occupancy for this room. In this case, drawing in air from an adjacent space might work, but remember that the ventilation requirement is based on outside air. So the amount of air that you transfer into this small room will depend on the fraction of outside air that is in the supply air to the adjacent space. For example, if the supply air in the adjacent space is 20% outside air, then you will have to transfer 250 CFM into your small room to satisfy the requirement.

As mentioned above, overall system balance and heating/cooling loads must be considered. Of course, whatever amount you exhaust will have to be brought into the building, either at the air handler or through infiltration. You need to study the entire system to determine the best solution.


---KenRad

 

[thermcool]

If you think the adjacent air is not adequately fresh why not use a fan that can basically suck the air rom outside and provide positive pressure inside. Positive pressure inside will exhaust the room air into the adjacent area.

it depends the ventilating requirements in the surrounding area also.

 

[thermcool]

If you think the adjacent air is not adequately fresh why not use a fan that can basically suck the air from outside and provide positive pressure inside. Positive pressure inside will exhaust the room air into the adjacent area.

it depends the ventilating requirements in the surrounding area also.

 

[Drazen]

if you call that room "small", most of us think that room is not intended as place of permanent occupation by building users.

that should mean the room is either toilet room or supplies storage or similar. in that case you generaly don't need fresh supply air, the simplest solution is to have exhaust (local or central, depending on main systems layout and configuration), and neighboring room should be positively pressuresized to provide air for that small room via door louvres (uni-directional type).

 

[carlosgw]

OK, a small one person office. No outside walls or roof. No central air system in the building. How would you supply the 20CFM outside air to the space?

 

[willard3]

When you say ventilation, do you mean cooling or do you mean outside air or a combination of both?

You can get split systems to turn the air over and cool....outside air is going to be a problem.

How small is a small office? 1 CFM/square foot with 8' ceilings will get the air changes up.