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Chris-<br>
<br>
One thing to keep in mind regarding eQUEST/DOE-2's "natural
ventilation" model, is that it is based on the Sherman-Grimsrud
method, which was specifically developed for estimating envelope
infiltration in smaller (1-3 story), single-family structures.
Below is a link to a copy of the original report outlining the
method. The report gives some good background on other infiltration
models, and the context in which the model was developed (incl.
comparison to measurements). As described in the report and the
DOE-2 help manuals, you will find that many of the model inputs are
specifically relevant to small houses. Finally, in the authors own
words (p. 4), "this report introduces an infiltration model that
sacrifices accuracy for versatility and simplicity." Therefore, in
my opinion, using this model, especially for larger structures, has
a good potential for giving misleading results. <br>
<br>
gundog.lbl.gov/dirpubs/10852_ShermanGrimsrud.pdf<br>
<br>
Unfortunately, DOE-2's "S-G_NV" method is the only NV model <u>readily</u>
available in eQUEST. By readily available, I mean you can select it
and enter inputs within the detailed or other BDL interface, and
many of the inputs have defaults. However, just based on my
experience in estimating the inputs for three of the DOE-2
"nonresidential" infiltration methods (AIR-CHANGE+AIR-CHANGES/HR,
AIR-CHANGE+INF-FLOW/AREA, and CRACK), these models can be quite
sensitive to inputs, including those in the SITE-PARAMETERS, and
finding estimates of these inputs for large buildings in literature
is difficult, if they even exist at all. I have not had the
opportunity to compare the S-G_NV model with another NV model for
larger buildings (such as CFD), but I would guess that if they are
close, it would be mostly luck that you picked the correct S-G_NV
inputs.<br>
<br>
I have modeled a couple nonresidential buildings that attempt to use
a NV strategy to offset mechanical cooling needs. However, to be
conservative, I often only accounted for an expanded comfort range
(similar to what Timothy described) rather than trying to use the
DOE-2's S-G_NV method. Although I think some buildings are
well-designed to take advantage of NV, in my mind, unless you have
some sort of mechanical controls to open windows, all bets are off.
Not that there aren't some real potential energy savings with
well-designed NV strategy, its just that the methods for estimating
the impacts w/ eQUEST/DOE-2 are not sophisticated enough. Anyone
out there have any evidence or comparative modeling that indicates
otherwise? <br>
<br>
After doing a lot of thinking about modeling NV, one idea for a
"work-around" that accounts for NV using eQUEST, is using custom
LOADS (infiltration) / SYSTEMS (availability) schedules and other
inputs based on pre-processing of weather and building geometry data
(may require some iterative runs...). <a moz-do-not-send="true"
href="www.pnl.gov/main/publications/external/...reports/PNNL-18898.pdf">I
would guess that the majority of NV impacts are from wind-driven
infiltration through windows. Along these lines, below is a link
</a>to a PNNL paper that describes how to develop E+ "wind-driven"
infiltration model inputs (basically the same as DOE-2 "AIR-CHANGE"
method) using local wind pressure coefficients and a design
infiltration rate (leakage @ 75Pa). For combination wind+stack
driven air flow through windows, the model would likely have to get
more complicated, but pre-processing to calculate DOE-2 inputs gives
you a lot of flexibility in what you account for...<br>
<br>
I have not actually had the opportunity to develop this kind of
method yet, but I hope to get a project where the design (and
budget) justifies this level of analysis. With any type of
work-around, I would plan to do some sort of validation with another
model, such as CFD, or a calibration exercise, but these approaches
for validating NV open other cans of worms... <br>
<br>
Anyone have any experience with validating the NV model (or your
own) that exists in the one of the available building energy
simulation programs? Any other ideas for "work-arounds"? Has
anyone gotten feedback from reviewing bodies (GCBI, utilities, code
reviewers) on the use of DOE-2's "S-G_NV" method?<br>
<br>
<a class="moz-txt-link-abbreviated"
href="http://www.pnl.gov/main/publications/external/...reports/PNNL-18898.pdf">www.pnl.gov/main/publications/external/...reports/PNNL-18898.pdf</a><br>
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<pre class="moz-signature" cols="72">David Reddy
360 Analytics
Building Energy Analysis Consultants
mail: 12354 16th Ave NE, Seattle, WA 98125
office: 206.420.7918
mobile: 206.406.9856
web: <a class="moz-txt-link-abbreviated" href="http://www.360-Analytics.com">www.360-Analytics.com</a></pre>
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