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style="FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT: normal; TEXT-DECORATION: none">Conventionally,
</DIV><FONT size=3 face=Calibri>ERV ducting uses metal round pipes and flex
ducts for delivering supply fresh air and return air. However, as noted in
earlier messages, I am planning an exterior wall and roof mounted insulation,
leaving the framing cavities available for other purposes. I expect there
may be good reasons why this is not a good idea. However, I do not know
them. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>Heating to be achieved with direct air supplied
wood stove and passive solar. Immediately we are not installing active
dehumidification. However, we are contemplating some form of desiccant
where desiccant can be recharged by solar or wood during the summer months,
therefore, giving benefit for latent heat recovery of ERV in addition to
sensible heat recovery of HRV. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>On the plus side, these frame cavities reach to
all parts of the house and exist without extra construction. They provide a much
larger area when compared to round ducts. 50si for 8” round duct. A
2x6 stud cavity with 1.5 inch subtracted from width for band joist between
floors leaves a 4”x 22.5”=92si, a 2x10 joist cavity is 14x9=126si, much larger
than the 8” round duct. The air speed of a given flow that significantly affects
sound is louder with smaller cross section area. I know that the shape of
stud and joist cavities is not as efficient. However, I would think that
the additional size would make up for the shape. Air grilles could be
balanced to get the appropriate air to all the spaces served. With an ERV,
our temperature differences are not as great as ducts intended for air
conditioning and heating. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT face=Calibri><FONT size=3>Looking in our <EM><STRONG>Virginia
Residential Code</STRONG></EM> which is for the most part based on the
<EM><STRONG>International Residential Code</STRONG> says the following:
</EM></FONT></FONT></DIV>
<DIV><FONT size=3 face=Calibri><EM></EM></FONT> </DIV>
<DIV><FONT face=Calibri><FONT size=3><EM>Use of gypsum products to construct
return ducts or plenums is permitted, provided that the air temperature does not
exceed 125F and exposed surfaces not subject to condensation.</EM>
</FONT></FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>I could line the framing cavity with gypsum
drywall and call it a duct for returns. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri><EM>Stud wall cavities and spaces between solid
floor joist to be used as air plenums shall comply with:</EM></FONT></DIV>
<DIV><FONT size=3 face=Calibri><EM></EM></FONT> </DIV>
<DIV><FONT size=3 face=Calibri><EM>These cavities or spaces shall<STRONG>
not</STRONG> be used a plenum for supply air. </EM></FONT></DIV>
<DIV><EM><FONT size=3>Stud cavities shall not convey air from more than one
floor level.</FONT></EM></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>These rules pretty much kills the concept.
However, I want to know why. All air ducts pass air through assemblies
that create some vulnerability to flame spread. If cavities were lined
with gypsum and air sealed, they should be fire protected. The supply air
is where the need is greatest to get to all the different spaces with easy
access to top or bottom grille as is best for functioning. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>I guess I could make a sheet metal box for stud
cavities and use conventional round ducts in joist space to comply with
code. </FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>Achieving cost affective solutions is critical to
finding acceptance in the market. Wherever we can, we need to look for
ways of achieving the functionality with lower cost and materials.
</FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>I look forward to hearing from list participants.
</FONT></DIV>
<DIV><FONT size=3 face=Calibri></FONT> </DIV>
<DIV><FONT size=3 face=Calibri>Eli </FONT></DIV>
<DIV><FONT size=3 face=Calibri><A
href="http://www.conservationarchitect.net">www.conservationarchitect.net</A>
</FONT></DIV>
<DIV><EM><FONT size=3 face=Calibri></FONT></EM> </DIV>
<DIV><EM><FONT size=3 face=Calibri></FONT></EM> </DIV>
<DIV><FONT size=3 face=Calibri><EM></EM></FONT> </DIV>
<DIV><FONT size=3 face=Calibri><EM>Stud cavities shall not convey air from more
than one floor level.
</EM></FONT></DIV></DIV></DIV></DIV></DIV></DIV></BODY></HTML>