Almost ready to build!! Flaws in my plans for ventilation?

thebearingedge · Post by **thebearingedge** » Mon Oct 08, 2007 6:31 am

Hi Everyone!

My partner and I have begun design of our 252 sq.ft tracking room (21' by 12' interior with 10' ceiling). The tracking room will be standing inside of an existing building.

I'm trying to design every part of the building at the same time in order to minimize hang-ups but figuring out ventilation is proving to be the hardest to research online and it's slowing our progress.

So far, wall and door construction are just about figured out..

We want to exchange the air inside the tracking room (approx. 2520 cu.ft) but not install a full blown AC ($$$!). We'll be turning on/off a portable AC every-so-often.

My plan right now is to install a plenum at two different points on the roof of the structure. One for intake and one for exhaust. Will a single 270 cfm exhaust fan with a 10.38" diameter pull enough air to ventilate our space?
According to raw numbers:

a 270 cfm fan should be able to draw 2520 cu.ft of air every 9-10 min.

Am I forgetting something? Will this work? Should I use an additional fan or move the exhaust one to the intake position? Would it be acoustically beneficial to use intake fans and not exhaust fans?
I was looking at this design but will not have a "chiller room" involved, just the surrounding building.
http://www.johnlsayers.com/phpBB2/viewtopic.php?t=644
Assume that the existing structure (approx. 7125 cu.ft) around the tracking room is sufficiently ventilated with outside air.

I greatly appreciate any and all input!

thebearingedge · Post by **thebearingedge** » Thu Oct 11, 2007 4:22 am

rod gervais · Post by **rod gervais** » Thu Oct 11, 2007 4:28 am

edge,

you don't include (with your profile) where you are located - and this changes the answer - so perhaps you should begin with by following the requirements included under the "read this before you post" thread.

Read this first and then get back to us.

Rod

thebearingedge · Post by **thebearingedge** » Thu Oct 11, 2007 5:00 am

sorry rod. not the best first impression i've ever made

will do

rod gervais · Post by **rod gervais** » Thu Oct 11, 2007 9:50 am

Edge,

OK. No problems......

This is why we ask for that info (among other reasons) in the States we have rules that don't exist everywhere else in the world.

This fresh air issue is one of those cases.

The requirement under the code is that you have a door - operable window - or other means of a direct connect between any occupied room and the outside world.

And they do mean direct communication betwee the 2.

You can use an adjorning space (room) BUT - in that case - you cannot have a means of seperating the 2 rooms.

You need an opening that is a minimum of 25s.f. - which must remain open at all times...........

You get away from that requirements through the use of the chiller room because (as I note in my book) the chiller room is dedicated to the room it is providing air to - this it is (for all intent and purposee) an extended part of that room and can (and will be) used for no other purpose.........

The same cannot be said in your current situation.

The only other option you have is to provide air through mechanical means - which MUST come on when the space is occupied (so you can tie it into your lighting switch etc., etc..............).

The way you present this - you will be pulling air from your attic and between the building walls - that is a no no.

If i have this pictured wrong please let me know.........

Rod

thebearingedge · Post by **thebearingedge** » Thu Oct 11, 2007 4:45 pm

Basically we are building the tracking room inside of a larger building that has a huge 8' x 2.5' sun roof/window on the ceiling (to the roof) next to a 3' wide circular hole leading to the roof. This is why I assumed that the existing room can be considered open and ventilated. Like I said, these openings are to the outside air or sky.

Existing building: 26' x 19' x 15' tall interior dimensions
Tracking room: 23' 14' x 11' tall exterior dimensions
So I wouldn't say that air is coming from an attic.
In fact, with the exception of using it as a path from the tracking room to the control room or exits to the street, the existing room will always be empty, with openings in the ceiling to the outside world totaling around 25 sq ft

Thanks again for examining my situation.

thebearingedge · Post by **thebearingedge** » Thu Oct 11, 2007 4:52 pm

rod gervais wrote:
The only other option you have is to provide air through mechanical means - which MUST come on when the space is occupied (so you can tie it into your lighting switch etc., etc..............).

This I'm sure can work out. I just need to know how much are my fan has to be spec'd to move to provide 2500 cu.ft of fresh air at an acceptable rate.

Thank you!

rod gervais · Post by **rod gervais** » Thu Oct 11, 2007 11:14 pm

how did you arrive at 2500 cubic feet of fresh air needed to meet your requirements?

Although I understand your explanation - the code doesn't recognize it as being acceptable.

The code reads as follows:

"1203.4.1.1 Adjoining Spaces. When rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 20 square feet (1.86 sm). The minimum openable area to the outdoors shall be based on the total area being ventilated"

That just about says it all...........

Rod

thebearingedge · Post by **thebearingedge** » Fri Oct 12, 2007 1:12 am

Hi Rod:

rod gervais wrote:how did you arrive at 2500 cubic feet of fresh air needed to meet your requirements?

Simply that the volume of the tracking room is 2500 and that to be "ventilated", that volume must be replaced over some repeating interval of time... I don't know how many times per hour.

rod gervais wrote:Although I understand your explanation - the code doesn't recognize it as being acceptable.

The code reads as follows:

"1203.4.1.1 Adjoining Spaces. When rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 20 square feet (1.86 sm). The minimum openable area to the outdoors shall be based on the total area being ventilated"
That just about says it all...........

It's clear to me now... I must have only been reading what I wanted to see at first.

Anyhow, this, I believe is doable:

rod gervais wrote:The only other option you have is to provide air through mechanical means - which MUST come on when the space is occupied (so you can tie it into your lighting switch etc., etc..............).

Which sort of leads me back to my original question about the fan... I think... not so sure when that's the question to ask!

I also remember reading your posts about how certain HVAC configurations do a poor job of dehumidifying spaces because they aren't on long enough. Is this because the increasingly humid air inside the building/room is not sufficiently replaced before the system shuts off?

Thank you for your time!!