[BLDG-SIM] Infiltration: Standard versus Proposed Design

[K Emerson]

I would agree that infiltration is a guess at best and
go further in saying that it would be relatively easy
to stick a number in a base model that would represent
excessive infiltration in order to get unjustified
credit.  

Typical engineering practice these days is to maintain
a slight positive pressure during normal building
operation.  This aids in comfort by eliminating cold
drafts in winter climates and assisting in control of
moisture in wet ones.  Infiltration at worst should
thus only occur during unoccupied periods.  That said,
high-rise buildings often have enough stack effect
that this moderate positive pressure is overwhelmed on
the first floor with people opening doors, etc.  

It should be assumed that in new buildings, especially
those being considered for LEED credit, people will be
paying attention to the tightness of the shell during
construction.  

Keith Emerson


--- Brian Thornton <bthornton at glumac.com> wrote:
> Is it the sense of the group that infiltration can
> be predicted well enough
> in commercial buildings to take credit for energy
> savings in this area?  I
> considered this issue a few years ago, and the
> literature seemed to indicate
> that prediction was very poor, and that field work
> indicated that
> infiltration would vary substantially, in the same
> building under similar
> outside temperatures due to small differences such
> as a few windows or doors
> opended differently, and that it was in most cases
> unclear what the
> differences were due to.
>  
> Brian Thornton
> Glumac, bthornton at glumac.com
> 
> -----Original Message-----
> From: Marcus Sheffer [mailto:sheffer at paonline.com]
> Sent: Wednesday, May 19, 2004 9:00 AM
> To: BLDG-SIM at gard.com
> Subject: [BLDG-SIM] Infiltration: Standard versus
> Proposed Design
> 
> 
> Right now infiltration reduction is not an eligible
> item for energy cost
> reduction for LEED.  Infiltration rates must be the
> same in the proposed and
> budget buildings.
> 
> My understanding is that the Energy & Atmosphere
> Technical Advisory Group
> (EA TAG) of the USGBC is considering this issue with
> an eye toward
> developing a modeling protocol.
> 
> I am aware of at least two projects that have
> applied for savings in this
> area which have been put on hold (the LEED points
> were denied pending
> further input from the EA TAG).  
> 
> 
> As At 10:33 AM 05/19/2004, you wrote:
> 
> 
> Can infiltration be considered in comparing standard
> versus proposed design
> models using the ECB method and for LEED credits
> under "Optimize Energy
> Performance"?  Typically we use the same criteria in
> both models, but this
> is a particular case of a proposed double-wall
> building.  "10CFR435 Table
> 402.2.1. - Air Leakage for Fenestration & Doors
> Maximum Allowable
> Infiltration Rate" provides standard model
> information for federal
> buildings.  For example, the infiltration rate is
> 0.15 cfm/ft2 for fixed
> aluminum windows.  Can this be used for LEED
> standard design and can a lower
> rate be used for double wall buildings?
>  
> The CFR table does not account for Heating & Cooling
> Degree Days as with
> Table-B Building Envelope Requirements of STD90.  In
> my opinion, the peak
> design infiltration rate should be varied from
> maximum in winter to minimum
> in summer (typically zero for pressurized buildings)
> using a schedule.  The
> maximum, of say 0.15 cfm/ft2, would apply to a cold
> climate such as Chicago
> and it should be scaled down for warmer climates. 
> Since DOE2 does not allow
> infiltration rates on the basis of cfm/ft2 of wall
> or window area or cfm per
> lineal foot of window perimeter, we create a typical
> perimeter space and
> convert the window based infiltration rate to
> cfm/ft2 of space area or space
> air changes. We then look at the results in "REPORT-
> LS-C BUILDING PEAK LOAD
> COMPONENTS" of the DOE2 output to see if the
> infiltration load looks
> reasonable (relative to the other loads) for the
> location and type of
> building and make adjustments by trial and error. 
> Judgment and experience
> is considered more reliable than theoretical
> mathematical models.  The BEPS
> and BEPU reports in DOE2 should separate out the
> infiltration loads from the
> heating & cooling loads.  Any comments?
>  
> Thanks for the comments and suggestions to using
> different utilities in
> standard versus proposed design.  They were very
> helpful in making some
> decisions here.  Most of the responses seem to go
> directly to the person
> asking the question.
>  
> Varkie Thomas
> Skidmore, Owings & Merrill LLP
>  
>  
>  
> 
> 
> 
> 
> 
> 
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> 
> Marcus B. Sheffer                          energy &
> environmental consulting
> Energy Opportunities, Inc              717-292-2636
> 1200 E Camping Area Road            Fax:
> 717-292-0585     
> Wellsville, PA USA 17365-9783       
> sheffer at sevengroup.com
> a 7group company                        
> <http://www.sevengroup.com/>
> www.sevengroup.com
> 
> 
> 
> 
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