[Bldg-sim] Infiltration & PRM

[Fred Porter]

Anyone;
I'm looking for verification of "official" treatment of infiltration in
PRM models or other baseline/comparison method definitions. I can't find
air leakage or infiltration mentioned specifically in App G, Chapter 11,
or related sections of the UM, generally meaning these should be the
same in both (low, except in public entry areas, assuming mandatory
provisions are met and perform). A perusal of LEED 2.2 EAc1 section in
the ref guide was not fruitful. T24 and an old CIR contained the only
specific references I could find. Am I missing anything? ASHRAE
interpretations? LEED 2.1 ref guide EAc1 "protocol?" The Canadian
MNECB/CBIP? 
 
Thanks for any insight;
Fred W. Porter
AEC
 
Title 24
Modeling Rules for Proposed Design:
Infiltration shall either be modeled as "ON" or "OFF", for each zone,
according to the
following:
· "OFF" if fans are ON and zone supply air quantity (including transfer
air) is
greater than zone exhaust air quantity.
· "ON" if fans are OFF.
When infiltration is "ON", the reference method calculates the
infiltration rate as
0.038 cfm per square foot of gross exterior partition (walls and
windows) area for the
zone. 

Modeling Rules for Standard Design
(All):
ACMs shall model infiltration for the standard design exactly the same
as the
proposed design.
 
CIRs
 7/9/2007 -  Ruling
This CIR seeks to use reduced infiltration rates from a superior
building envelope as a variable in the energy cost budget calculation
for optimizing energy efficiency. 

The ASHRAE modeling protocol does not allow the infiltration rate to be
changed between the budget and the design case. The CIR ruling of
3/11/2003 for EAc1.2 provides some guidelines on how a case might be
made for advanced air sealing. The methodology proposed for this project
does not address all the issues raised in that ruling and would be
insufficient to grant an exception to the modeling protocol.
 
 3/11/2003 -  Ruling
Advanced air sealing is a strategy that can lead to measurable energy
savings, particularly in cold climates. Although this measure is outside
the scope of ASHRAE 90.1 modeling protocol, you may be able to make a
case for the significance of this strategy in improving energy
performance. However, this will require clear and thorough documentation
in order to be considered under the requirements of this credit. 

The following guidelines are provided to help strengthen your approach:


(1) Provide manufacturer's air leakage test results that use the same
testing protocol as that by which ASHRAE identified the baseline for
window air leakage. 

(2) Use a typical infiltration rate as a baseline, and reduce it by the
amount of improvement you can document or estimate from the air sealing
strategies employed. Do not use zero infiltration in the model, as this
is not a realistic assumption. A zero infiltration strategy would
over-emphasize the percentage of overall energy use reduction
represented by infiltration improvements. 

(3) Include required fresh air ventilation rates (per ASHRAE 62) in
both the proposed and baseline model results. 

(4) Provide clear documentation of air sealing strategies and blower
door test results, corrected for wind and temperature effects, to
clarify anticipated air sealing performance. 

(5) Provide documentation which clarifies the percentage of energy
savings attributed to the air sealing strategy, as opposed to other
energy performance measures incorporated into the building.
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