[bldg-sim] Modeling buildings with natural ventilation forAppendix G

[Gerald Pde]

Mike,
Thanks for your post. I think the only issue with this
method and which Jason Glazer has correctly pointed
out, is that it does not address how the heat from the
space is actually removed. This method will only
determine the conducive environment assuming there are
appropriate windows and window placement.

The other issue which might go in hand with this
calculation(and to avoid complex simulations)is to
determine in steady state conditions, if the zone in
question overheats during the upper threshold hours.
If it doesn't, then all the other hours should be
fine.

Any thoughts?
Gerald


--- Mike Tillou <miket at etcgrp.com> wrote:

> Gerald,
> 
> That sounds like a good method to me.  You might
> also look to see if you
> have any HVAC systems that could also be shut down
> (ie: pumps, chiller,
> etc..) that would be operating at the same time as
> your flagged values.
> I think this is exactly the kind of analysis I had
> in mind when I wrote
> my post about using the exception calculation.
> 
> The other important thing in my mind is also
> justifying the thermal
> conditions you use as your constraints.  Have you
> looked at what ASHRAE
> 55 says about acceptable temeprature ranges? 
> 
> It might be useful (for a reviewer) to document
> that, for example, free
> cooling could be used as high as 80F (per ASHRAE 55)
> but you choose to
> only pursue energy savings up to 75F.  In my mind
> this demonstrates a
> thourough understanding of the situation and an
> acceptance on the
> modelers part that you aren't going to achieve
> perfect results. 
> 
> I might also pull out any stray hours when it might
> not be practical to
> switch from mech cooling to NV.       
> 
> Mike
> 
> 
> Michael Tillou, PE
> ETC Group - Energy Engineering for a Sustainable
> Future
> Ph:413-458-9870
> 
> 
> -----Original Message-----
> From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> On Behalf Of Gerald
> Pde
> Sent: Wednesday, February 07, 2007 3:39 PM
> To: bldg-sim at gard.com
> Subject: [bldg-sim] Modeling buildings with natural
> ventilation
> forAppendix G
> 
> 
> Following up with these discussions, I wonder if
> this
> would this be an acceptable way to estimate natural
> ventilation in Appendix-G,
> 
> 1) I first determine the hourly values for dry bulb,
> humidity ratio and wind speed of the location of my
> project. 
> 
> 2) Secondly, I assume certain environmental/comfort
> criteria that would be conducive to naturally
> ventilate. In my case I assumed a temperature range
> of
> 55 F to 75 F ;a humidity ratio range of 48 Grains to
> 85 Grains; and wind speed between 1 to 15 m/sec.
> Thus bracketing a
> temperature range between 55 and 75 and limiting
> relative humidity to
> 60%. For these ranges, I can naturally ventilate and
> hence the HVAC
> equipment can be shut down. Also since these
> conditions are evaluated
> hourly, I assumed a time buffer where the building
> occupants take a
> slightly longer response time if the conditions
> drift from the comfort
> range.
> 
> 3) I evaluate these conditions hourly and flaged (1
> or
> 0) each and every hour when these conditions are
> met.
> 
> 4) Finally, I then took an hourly output of fan
> energy
> from DOE-2 hourly report and match them up with the
> natural ventilation FLAG and then calculate the
> total
> fan energy reduction when the HVAC system is shut
> off
> when the NV conditions are met. These results can be
> then averaged out annually. 
> 
> The fan power reductions in % can also be translated
> in terms heating energy reductions during the winter
> time but it was not significant for the location I
> was simulating for. I
> found the greatest fan energy saving to be during
> the shoulder periods
> of April, May and October. In total, it was about a
> 9% total HVAC (fans,
> pumps and heating and cooling) energy reductions and
> a 14% fan energy
> reduction which was not a huge amount when it came
> to total energy
> reductions and factoring 
> all end use components.
> 
> Let me know if anyone has any thoughts or comments
> and critically if
> this is an acceptable way to estimate NV savings in
> Appendix-G.
> 
> Thanks.
> Gerald
> 
> 
> 
> --- Michael Rosenberg
> <Michael.Rosenberg at state.or.us>
> wrote:
> 
> > That makes sense to me. You might get a little
> > additional savings due to
> > the fact that you are not adding heat from the fan
> > to the airstream with
> > natural ventilation, as you would with an
> > economizer.
> > 
> > Mike
> > 
> > Michael Rosenberg
> > Oregon Department of Energy
> > 625 Marion St. N.E.
> > Salem, OR 97301-3742
> > Phone : (503) 373-7809
> > Fax: (503) 373-7806
> > 
> > >>> "Jon McHugh" <Jon.McHugh at h-m-g.com> 12/21/06
> > 03:33PM >>>
> > Michael,
> > 
> > From the sound of this natural ventilation would
> > only save fan energy
> > as
> > compared to an air conditioner that has an
> > economizer, is this
> > correct?
> > There would not be any additional compressor
> > savings, is this correct?
> > 
> > Thanks,
> > 
> > Jon McHugh
> > 
> >  
> > 
> > -----Original Message-----
> > From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> > On Behalf Of
> > Michael
> > Rosenberg
> > Sent: Thursday, December 21, 2006 1:03 PM
> > To: bldg-sim at gard.com
> > Subject: [bldg-sim] Modeling buildings with
> natural
> > ventilation
> > forAppendix G
> > 
> > Marcus,
> > 
> > I am on the ASHRAE 90.1 ECB subcommittee. I do not
> > think at this point
> > that we are working on any additional methodology
> to
> > credit natural
> > ventilation. Addendum AG already changed the
> > following:
> > 
> > In the proposed building.
> > HVAC Fan Schedules. Schedules for HVAC fans that
> > provide outdoor air
> > for
> > ventilation shall run continuously whenever spaces
> > are occupied and
> > shall be cycled on and off to meet heating and
> > cooling loads during
> > unoccupied hours.
> > 
> > This implies that HVAC fans that are only meeting
> > thermal load may
> > cycle
> > on and off, and was meant to allow fan credit for
> > natural ventilation
> > system (as simple as operable windows). The
> proposed
> > building still
> > calls for cooling as a requirement, but the
> thought
> > is, that if model
> > simulates natural ventilation and the cooling load
> > is met that way,
> > the
> > fan and cooling coil will not operate to meet load
> > and the design will
> > be credited. The problem is that most LEED models
> > are done using DOE2,
> > which has severe limitations when it comes to
> > modeling natural
> > ventilation. It is my understanding that other
> > programs do a better
> > job
> > of this.
> > 
> > The subcommittee also thought that an exceptional
> > calculation method
> > might be used if the natural ventilation
> simulation
> > was be done in a
> > stand alone program and then an appropriate
> > infiltration schedule was
> > input into a program like DOE2, reducing the use
> of mechanical
> > cooling.
> > 
> > 
> > Mike
> > 
> > 
> > 
> > Michael Rosenberg
> > Oregon Department of Energy
> > 625 Marion St. N.E.
> > Salem, OR 97301-3742
> > Phone : (503) 373-7809
> > Fax: (503) 373-7806
> > 
> > >>> "Marcus Sheffer" <sheffer at sevengroup.com>
> > 12/21/06 11:58AM >>>
> > Mike,
> > 
> >  
> > 
> > The exception calculation method you describe is
> > absolutely correct.
> > 
> >  
> > 
> > Obtaining savings for natural ventilation within
> > LEED however is
> > another
> > story.  I am one of the certification reviewers
> and
> > also vice-chair of
> > the EA TAG.  My understanding is that to date the
> > USGBC has not
> > allowed
> > natural ventilation to fully count under EAc1 even
> > if submitted as an
> > exceptional calculation method.  The TAG is
> awaiting
> > the work of the
> > 90.1 subcommittee you mention to develop a uniform
> methodology.
> > 
> >  
> > 
> > Perhaps your submission will be the one to set the
> > precedent.  Thanks
> > to
> > all for helping to blaze the trail.
> > 
> >  
> > 
> > Marcus Sheffer
> > 
> > Energy Opportunities, Inc/a 7group Company
> > 
> > 1200 E Camping Area Road, Wellsville, PA  17365
> > 
> > 717-292-2636,  <mailto:sheffer at sevengroup.com>
> sheffer at sevengroup.com
> > 
> > www.sevengroup.com
> > 
> >  
> > 
> >   _____
> > 
> > From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> > On Behalf Of Mike
> > Tillou
> > Sent: Thursday, December 21, 2006 2:03 PM
> > To: bldg-sim at gard.com
> > Subject: [bldg-sim] Modeling buildings with
> natural
> > ventilation for
> > Appendix G
> > 
> >  
> > 
> > Not yet...I have a project with natural
> ventilation
> > using this method
> > that will be submitted for final review in Feb-Mar
> > 2007.
> > 
> >  
> > 
> > MMT
> > 
> > Michael Tillou, PE
> > ETC Group, Inc - Energy Engineering for a
> > Sustainable Future
> > Ph:413-458-9870
> > 
> > -----Original Message-----
> > From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> > On Behalf Of Peter
> > Alspach
> > Sent: Tuesday, December 19, 2006 1:34 PM
> > To: bldg-sim at gard.com
> > Subject: [bldg-sim] Modeling buildings with
> natural
> > ventilation for
> > Appendix G
> > 
> > Mike,
> > 
> >  
> > 
> > Have you succeeded in getting a naturally
> ventilated
> > building through
> > the USGBC with this method?
> > 
> >  
> > 
> > If so, I am sure all would be glad to hear it.
> > 
> >  
> > 
> > Peter
> > 
> >  
> > 
> > 
> >   _____
> > 
> > 
> > From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> > On Behalf Of Mike
> > Tillou
> > Sent: Tuesday, December 19, 2006 7:18 AM
> > To: bldg-sim at gard.com
> > Subject: [bldg-sim] Modeling buildings with
> natural
> > ventilation for
> > Appendix G
> > 
> > Ramana,
> > 
> >  
> > 
> > The ASHRAE 90.1 ECB sub-committee is working on a
> > methodology for
> > simulating natural ventilation within the
> framework
> > of Appendix G but
> > I
> > don't think its finished yet.  In the meantime
> here
> > is what I would
> > recommend.
> > 
> >  
> > 
> > Appendix G / 90.1 ECB allows you to use an
> exception calculation
> > method
> > to simulate hybrid systems or unique efficiency
> > measures to
> > demonstrate
> > above-standard performance.  I think this would
> > certainly apply in
> > your
> > case.   
> > 
> >  
> > 
> > Here's what I have done on projects requiring an
> > exception calculation
> > method.
> > 
> > 1. Establish your energy cost budget and your
> design
> > energy case
> > following the Appendix G guidelines.
> > 
> > 2. Create a second model using the Design Energy
> > Case as the baseline
> > and make the necessary modifications to simulate
> > radiant heating / no
> > cooling via natural ventilation.
> > 
> > 3. Report the energy savings from your exception
> > calculation as a line
> > item at the end of your LEED EA-1 summary table
> > (similar to how
> > renewable energy is reported).
> > 
> > 4.  Include a seperate summary table  for the
> > exception calculation
> > showing the energy end-use breakdown and how you
> > arrived at the cost
> > savings.
> > Show
> > both the baseline and proposed energy use.  
> > 
> > 5. Make sure the savings are reasonable and
> prudent
> > for the system you
> > are proposing.
> > 
> > 6. Document any changes to the model especially
> > changes to schedules
> > that were necessary to properly simulate your
> > system.
> > 
> > 7. Make it easy for someone to review your
> > assumptions and the
> > methodology you used to estimate the savings
> > 
> >  
> > 
> > I hope this helps.  Good luck.
> > 
> >  
> > 
> > Mike
> > 
> >  
> > 
> > Michael Tillou, PE
> > ETC Group, Inc - Energy Engineering for a
> > Sustainable Future
> > Ph:413-458-9870
> > 
> > -----Original Message-----
> > From: bldg-sim at gard.com [mailto:bldg-sim at gard.com]
> > On Behalf Of Ramana
> > Koti
> > Sent: Monday, December 18, 2006 4:53 PM
> > To: bldg-sim at gard.com
> > Subject: [bldg-sim] Modeling buildings with
> natural
> > ventilation for
> > Appendix G
> > 
> > Dear all,
> > 
> > Is ignoring natural ventilation in both proposed
> and
> > baseline designs
> > an
> > accepted/fair way of modeling based on Appendix G
> > (ASHRAE 90.1-2004)?
> > 
> > Part of the proposed design has (radiant heating +
> > natural
> > ventilation)
> > with no cooling which was modeled as a radiant
> slab,
> > no cooling,
> > natural
> > ventilation ignored.
> > 
> > But the Baseline HVAC system based on Appendix G
> is
> > System 5: Packaged
> > VAV w/Reheat. (Natural ventilation can be modeled
> > based on Air Change
> > method or Sherman Grimsrud method though I do not
> > know how to do it).
> > 
> > I cannot decide how to make the baseline and
> > proposed comparable with
> > respect to Natural Ventilation (in a manner
> > acceptable to LEED
> > review),
> > suggestions will be appreciated.
> > 
> > Thanks,
> > 
> > Ramana Koti, Sustainable Building Analyst LEED AP
> > 
> > ELEMENTS | a division of berkebile nelson
> immenschuh
> > mcdowell
> > architects
> > 106 W. 14th Street Suite 200
> > Kansas City, Missouri 64105
> > 
> > p 816.783.1635 f 816.783.1501
> > www.bnim.com| elements.bnim.com
> > 
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