Estimating infiltration with and without interior foyer doors

[Allgreatmen]

I've got a restaurant chain customer with stores in AZ that uses in their standard design a foyer with internal double doors. The foyer area includes seating for people who are waiting for a table in the restaurant. The internal doors of the foyer separate these people from the hostess station and dining room. The issue for the customer is the store operators always remove the internal double doors right after a new restaurant opens.

The customer has asked us to estimate the net annual energy saved for a restaurant if the internal doors remain in place versus if they are removed.

Are there resources out there that can help me with these infiltration calcs? I am not being paid to do a field investigation of actual pressure differences, so I figure the answer will depend a lot on my assumptions. I am planning on assuming the dining area is positively pressurized (per design), even though in reality that is not always the case.

 

[imok2]

Some of this information is from 2003 ASHRAE Applications Handbook:

Infiltration is a considerable factor in many restaurant applications because of short occupancy and frequent door use. It is increased by the need for large quantities of makeup air, which should be provided mechanically to replace air exhausted through
hoods and for smoke removal. Systems for hood exhaust makeup should concentrate on exhausting nonconditioned and minimally heated makeup air. Wherever possible, vestibules or revolving doors should be installed to reduce infiltration. Vestibules/Revolving Doors. The traffic into and out of buildings is a major source of infiltration and exfiltration. The problem is aggravated in the winter-time for north-facing entry doors. Double-entry swinging doors, entry vestibules, or revolving doors can reduce the infiltration of cold north winds and heat. There is no doubt that removing the doors will have an impact on the energy use!!
This PDF may be of interest: http:

http://edis.ifas.ufl.edu/EH171

 

[russmech]

Estimating infiltration through doors is most likely an impossible task. You're right about you're assumptions, that's most likely all your going to have.

I would start by assuming either a CFM/Sq Ft of door or an Air Change (A/C) rate for one hour blocks of time throughout the day; Example: 10 A/C's during the peak time hours, then taper down to say 4 A/C's or less during low use times. With an airflow rate, your design OA temp, your inside air temp known, you can get a BTUH load for the day/month/year.

For sizing vestibule equipment in the northern climates, I use either 10 CFM/Sq Ft of door or 10 A/C's. That is probably the highest you should go as that assumes a recovery rate, not steady state.

Don't you wish ASHRAE would publish a real world, rule of thumb manual along with their theoretical voo-doo?

 

[DouginMB]

If the building is pressurized, I assume about 1-2 ACH. Anything more and you're putting way too much air into a transient space. Although it might be a waiting area, there's no need to go nuts with the AC.

 

[Allgreatmen]

Thanks all for your help!