Designing for Infiltration through a Constantly open door

[jedwards]

What are the effects from keeping the front doors to a store open during the summer cooling months while trying to condition the space? (5000 sq ft) I am running into problems finding exact formulas for calculating wind and external pressures vs. internal building pressure through the open doorway. There are a number of factors to take into consideration.
The first being whether keeping the front entrance to a store wide open would violate energy code...specifically ASHRAE 90.1 The second, after calculating a velocity pressure from local wind data (19mph), how to determine the minimum velocity of air (or maybe static pressure) leaving the space through the doorway which will overcome the outside wind pressure. Also what amount, or will it even be substantial, of air will be lossed through exfiltration through the walls and other cracks as the pressure of the space is increased. I have already determined the vapor pressure difference from the outdoor vs indoor conditions to determine that effect into the space.
From other posts, I have seen data that suggests velocites thru the doorway (double doors as a matter of fact) of 50 to 60 fpm--that's a lot of air to be exhausted. Still, infiltration thru an opening this size will undoubtedly be significant.
Any help is appreciated. Thanks.

 

[ChasBean1]

Trying to match a 19 mph head wind at an open door would be nuts. The space would need to be about 35,000 cfm positive. If someone leaves the door propped open, the pressure inside/outside will be the same. Best bet is to keep the OA (make-up) airflow higher than the total exhaust airflow. That should keep the right flow direction during most times. If the rest of the building is tight, a gust of wind at the open door should be mostly deflected and not in-filtered.

 

[lilliput1]

You will not be able to maintain design indoor temperature & humidity for cooling. Use heated,ventilated only entrance vestibule. Povide partition & door to cooled space. Pressurize space to prevent infiltration (effective on summer only).

 

[wilg]

Chasbean1 has calculated the 35,000 cfm
by using a 7' x 3' door....
1 mph = 88 feet per minute (5,280/60)
the 19 mph that jedwards has mentioned in his question
gives us:
19 x 88 = 1,672 fpm (feet per minute)
a 7x3 door is 21 square feet
21 square feet x 1,672 fpm = 35,112 cubic feet per minute
using the equation
H = (V /4005) squared
where:
V = velocity in feet per minute
H = velocity pressure in inches water gauge
then
(1,672/4005) squared = 0.174 inwg of pressure
or 0.174/27.72 = 0.006277 psi
or 0.006277 x (21 sqft x 144) = 18.98 lbs of force on the
door, if you consider the door as a simple hatch,
since it's hinged on must use integral calculus
to work out the exact force on the door.
Chasbean1 and lilliput1 are both correct,
either shut the door or use a vestibule.

 

[jedwards]

As a side note...this is not my design by choice as you could guess, but rather a situation the building owner wants to do and so we're researching it for him. My first solution was, of course...uhh, shut the door.
Thanks for the info everybody.