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  1. #1
    Join Date
    Aug 2005
    Posts
    828
    Looked at a warehouse for my church today, they want to use it as a "storefront/warehouse" church to attract young people to join. 15 cfm for potentially 100 people in a 3200 sq ft space is really going to jack up the tonnage requirements to provide cooling for this space, esp. since the use times are only a few hours a week. This is not really my speciality, but I'm just trying to provide them some advice to guide their decisions. Reading some stuff it sounds like demand controlled ventilation by CO2 sensing would work, but have no idea how expensive that type of system is, plus you would still need the maximum tonnage anyway. Anybody have experience with this situation?
    eventu rerum stolidi didicere magistro

  2. #2
    It needs to meet codes, when you start jamming a bunch of people into a small space it seems to become very expensive to provide proper ventilation, but thats the breaks, thats what it cost.And thats 15 per CFM, if they are not active,

  3. #3
    Join Date
    Apr 2002
    Posts
    11,808
    They may cut you a bit of a break if it is typically occupied for less than 3 hours at a time
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  4. #4
    Suck it up on first cost and save using demand control ventilation.

  5. #5
    Join Date
    Jun 2005
    Location
    Ohio
    Posts
    1,716
    Originally posted by panocha
    Suck it up on first cost and save using demand control ventilation.
    Amen.
    Jogas

  6. #6
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    1,948
    Demand controlled ventilation (DCV) will only help when the church is less than fully occupied. *IF* it is fully occupied at the outdoor design condition, DCV would be fully open and you would need the same tonnage as if you didn't have DCV at all. But DCV would save you a bunch of electricity during the week when the church isn't fully occupied.

    As Carnak said, if the time of occupancy is less than three hours and the space is nearly empty before and after, you can cut the ventilation to 1/2 the 15 cfm per person.

  7. #7
    Join Date
    Oct 2005
    Location
    IL
    Posts
    15

    DCV + ENTH

    Use CO2 sensors for Demand Controlled Ventilation to establish the minimum Outside Air but use Enthalpy sensors to override DCV for maximum Outside Air for free cooling.
    steve g

  8. #8
    Join Date
    Aug 2005
    Posts
    828
    Originally posted by panocha
    Suck it up on first cost and save using demand control ventilation.
    But this is leased space and the payback period for only using the system 3 hours per week would be astronomical.
    eventu rerum stolidi didicere magistro

  9. #9
    Join Date
    Aug 2005
    Posts
    828
    Originally posted by cxagent
    Demand controlled ventilation (DCV) will only help when the church is less than fully occupied. *IF* it is fully occupied at the outdoor design condition, DCV would be fully open and you would need the same tonnage as if you didn't have DCV at all. But DCV would save you a bunch of electricity during the week when the church isn't fully occupied.

    As Carnak said, if the time of occupancy is less than three hours and the space is nearly empty before and after, you can cut the ventilation to 1/2 the 15 cfm per person.
    Is this in any kind of manual (ashrae?) that I could use with the building inspectors. It sounds reasonable. Looking around the net I've found a reasonable argument that 3 cfm per person seated would maintain reasonable O2 and co2 levels, about 50% more for standing. Maybe add little more for praying and worshipping and we're at 7.5?

    What about diverting some of an existing unit that looks to be oversized for the front offices to maintain space temps during low occupancy periods (plus there is a unit heater) and adding a system just devoted to ventilation they can turn on when occupied?
    eventu rerum stolidi didicere magistro

  10. #10
    Join Date
    Apr 2002
    Posts
    11,808
    Look at ASHRAE 62, https://resourcecenter.ashrae.org/st...ent=311&page=1

    There are lots of interpretations in the appendix of this standard on how to work out the reduced ventialtion rates.

    There will be seminars on this standard during the AHR Expo (ASHRAE WINTER MEETING) in Chicago, from Jan23-25.

    You really need to check the mechanical code enforced in your area. Some codes defer to ASHRAE 62, others have their own ventilation rates set.





    [Edited by Carnak on 12-29-2005 at 09:19 AM]
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #11
    Originally posted by cxagent
    Demand controlled ventilation (DCV) will only help when the church is less than fully occupied. *IF* it is fully occupied at the outdoor design condition, DCV would be fully open and you would need the same tonnage as if you didn't have DCV at all. But DCV would save you a bunch of electricity during the week when the church isn't fully occupied.

    As Carnak said, if the time of occupancy is less than three hours and the space is nearly empty before and after, you can cut the ventilation to 1/2 the 15 cfm per person.
    I don't think you added anything new to the conversation. Save your keystrokes next time.

  12. #12
    Join Date
    Apr 2002
    Posts
    11,808
    Oh boy another a$$hole. talk about wasted keystrokes.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  13. #13
    Join Date
    Apr 2002
    Posts
    11,808
    Originally posted by panocha
    Originally posted by cxagent
    Demand controlled ventilation (DCV) will only help when the church is less than fully occupied. *IF* it is fully occupied at the outdoor design condition, DCV would be fully open and you would need the same tonnage as if you didn't have DCV at all. But DCV would save you a bunch of electricity during the week when the church isn't fully occupied.

    As Carnak said, if the time of occupancy is less than three hours and the space is nearly empty before and after, you can cut the ventilation to 1/2 the 15 cfm per person.
    I don't think you added anything new to the conversation. Save your keystrokes next time.
    Are you from Ohio pookie?
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

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