Ventilation Requirements

[cmic]

Hey All,

I am new to this forum and have been impressed so far.

I have a question concering ventilation requirements for comercial buildings. I work in a Canadian company that builds portable offices that have an HVAC system built in. the company desinging the HVAC for us has included a user operated damper that allows from 0% to roughly 50% fresh air and they claim that you can run the system at 0% with no issues. They are aware that the offices can be occupied by 1 to 6 people. If it is relevant, the offices are water tight.

Now for the question; is there a minimum volume of fresh air required for occupied spaces and what is the applicable code or standard (preferably Canadian)? How do you handle the case when you do not know the occupancy?

I am concerned that the users will close the damper to max the heat and end up with poor/dangerous air quality .

Chris

[Terence McCann]

Hey All,

I am new to this forum and have been impressed so far.

I have a question concering ventilation requirements for comercial buildings. I work in a Canadian company that builds portable offices that have an HVAC system built in. the company designing the HVAC for us has included a user operated damper that allows from 0% to roughly 50% fresh air and they claim that you can run the system at 0% with no issues. They are aware that the offices can be occupied by 1 to 6 people. If it is relevant, the offices are water tight.

Now for the question; is there a minimum volume of fresh air required for occupied spaces and what is the applicable code or standard (preferably Canadian)? How do you handle the case when you do not know the occupancy?

I am concerned that the users will close the damper to max the heat and end up with poor/dangerous air quality .

Chris

Who is the HVAC firm that is designing these units for you? They should be able to tell you what the fresh air requirement are (or at least I hope they could). For your own information I'd poke around

http://www.ashrae.org/ to see what you can turn up.

I've never seen a outdoor air damper that can be accessed by Joe Officeworker. In any case I can't see why this should be something that they can access and adjust.

Trane makes a detector that will modulate the outdoor air dampers based on CO2. One big problem is overcrowding the workspace and then running into these type of problems.

In the summer you can't open the outdoor air dampers 50% and expect the HVAC unit to remove humidity and maintain a comfortable indoor air temperature. The situation is only exacerbated with overcrowding.

[Bain]

Hey All,

I am new to this forum and have been impressed so far.

I have a question concering ventilation requirements for comercial buildings. I work in a Canadian company that builds portable offices that have an HVAC system built in. the company designing the HVAC for us has included a user operated damper that allows from 0% to roughly 50% fresh air and they claim that you can run the system at 0% with no issues. They are aware that the offices can be occupied by 1 to 6 people. If it is relevant, the offices are water tight.

Now for the question; is there a minimum volume of fresh air required for occupied spaces and what is the applicable code or standard (preferably Canadian)? How do you handle the case when you do not know the occupancy?

I am concerned that the users will close the damper to max the heat and end up with poor/dangerous air quality .

Chris

Who is the HVAC firm that is designing these units for you? They should be able to tell you what the fresh air requirement are (or at least I hope they could). For your own information I'd poke around

http://www.ashrae.org/ to see what you can turn up.

I've never seen a outdoor air damper that can be accessed by Joe Officeworker. In any case I can't see why this should be something that they can access and adjust.

Trane makes a detector that will modulate the outdoor air dampers based on CO2. One big problem is overcrowding the workspace and then running into these type of problems.

In the summer you can't open the outdoor air dampers 50% and expect the HVAC unit to remove humidity and maintain a comfortable indoor air temperature. The situation is only exacerbated with overcrowding.

Terry,

I've seen several smallish office buildings--with a few +/- 200 sq. ft. meeting rooms--that had permanent return ducts that continually drew and conditioned air from the exterior. These set-ups always look screwy to me.

How does the installer compensate for the excessive heat and humidity you mentioned? By oversizing the system?

[Darren]

I don't know about Canada, but here in the US, table 403.3 of the IMC clearly defines the requirements for 'Required Outdoor Ventilation Air".

[cmic]

Thanks for all the input.

Some background info:

The company doing the HVAC is not an HVAC firm but a company that specializes in outfitting portable/temporary shelters (tents, offices, controlled storage containers. We are doing the assembly and finishing of the offices.

The offices in question range from 40 sqft to 360 sqft. Many of these offices are setup as "in field" workshops and often need ventilation for the activities (soldering, grinding, welding, gluing...). This is why the user has damper control. It has been considered to have an independent system for this ventilation but space, weight and power are all limited.

I have found a reference in the Canadian building code that calls for 10L/second/person but I do not know the number of occupants in most cases. I was hoping there was a minimum based on sqft.

I guess I will use a conservative max ocupancy and have them put a limiter on the damper to ensure there is sufficient fresh air for worst case.

Thanks again,

Chris