Big Green: Natural Ventilation

[terry brennan]

Interesting problem.  First some questions:
 
*                     What is the ventilation requirement (in terms of cfm
or ACH)?
*                     Does the walkway go from building to building; from
outdoors to building or from outdoors to outdoors?
o        the answer is important because there will almost certainly be
pressure differences induced by buildings at either end
o        which means that the walkway may be accidentally ventilated by fan,
stack or wind forces acting on buildings (I've been in connecting walkways
with 25,000 cfm passing through them from one building to another)
o        plan to take advantage of the buildings at either end
*                     if the answer is there are no buildings at either end,
or we must keep fire doors closed at both ends, then the walkway ventilation
must stand alone in which case you must look at the wind and stack resources
you have at the site (as Peter Brooks suggests)
*                     I'd consider trying to catch wind and pressurize one
end and use a chimney at the other end to depressurize (like the Iranian
mosque systems); there are a number of ways to accomplish this; this is a
fairly simple situation so stack is easy to calculate and simple wind
effects fairly simple (augmented intakes, flow limiting devices and
Bournoulli exhaust outlets are way more complicated to model).  You could do
a simple CONTAM model or a more sophisticated cfd model using TMY2 data
*                     There's a bunch of hardware out there already
including simple systems intended for animal shelters, warehouses and some
pretty slick European stuff from their passive buildings work
*                     You will want someway to prevent over ventilation and
someway to augment ventilation when wind and stack forces are low
 
Terry Brennan
 
 
  _____  

From: biggreen-bounces at lists.biggreen.org
[mailto:biggreen-bounces at lists.biggreen.org] On Behalf Of BROOKS, PETER
Sent: Thursday, September 07, 2006 10:20 AM
To: Zoeteman, Mark R.; BigGreen
Subject: RE: Big Green: Natural Ventilation
 
Mark
An Architects solution would be to look at the site orientation, for sun and
wind patterns. Design a "solar chimney" based on solar heated hot air rising
and exhausting. This should be placed so the prevailing winds in warm
weather will supplement the effect. Provide make up air vent with damper to
close during colder weather. Orient the windows to provide solar gain to
warm the passage and some thermal mass to prevent drastic temp fluctuations.

Sounds easy, but it's not. 600 feet is a long passage, but it is a
transition space where people will not be for a long time. This is a good
project for fine tuning a natural ventilation system.
 
Peter Brooks AIA, LEED AP     
 
  _____  

From: biggreen-bounces at lists.biggreen.org
[mailto:biggreen-bounces at lists.biggreen.org] On Behalf Of Zoeteman, Mark R.
Sent: Thursday, September 07, 2006 8:24 AM
To: BigGreen
Subject: Big Green: Natural Ventilation
 
Is anyone aware of a method to introduce natural ventilation through a
structure passively? We want to ventilate a 600 foot long, 12 foot wide,
elevated enclosed walkway without adding complex motors and contols. Manual
operable windows are not an option as this is a municipal owned walkway and
maintenance staff is not available to open/close windows. Is their a
gravity-based damper arrangement that might work, introduce air low and
relieve high on opposite side? Location is northern climate, therefore
system would need to close during cold outdoor air temperatures.
Mark Zoeteman 
FTC&H, Inc. 
(616) 464-3739 
mrzoeteman at ftch.com 
 
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