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<font size="-1"><font face="Arial">Chris -<br>
<br>
We generally study these building envelope moisture-control issues with
WUFI - a program that uses the hygroscopic properties of component
materials along with moisture and temperature environment variables to
determine if there is potential damage from moisture and condensation.
<br>
</font></font>
<pre class="moz-signature" cols="72">Dave Bryan
AIA, LEED
AmerINDIAN Architecture
Suite 100, 475 Cleveland Avenue North
Saint Paul, Minnesota, 55104 USA
651-644-1586 phone
651-644-7172 fax
<a class="moz-txt-link-abbreviated" href="mailto:dbryan@amerindian.com">dbryan@amerindian.com</a>
<a class="moz-txt-link-abbreviated" href="http://www.amerindian.com">www.amerindian.com</a>
<a class="moz-txt-link-rfc2396E" href="http://www.amerindian.com/"><http://www.amerindian.com/></a>
</pre>
<br>
<br>
Chris Yates wrote:
<blockquote cite="mid:49356E4B.4080703@zed-uk.com" type="cite">Hi
<br>
<br>
I've been looking at the problem of condensation in heritage buildings.
I'm concluding that - especially in winter - best practice would be to
mechanically ventilate to a positive pressure (i.e. supply more than
extract).
<br>
<br>
My rationale is thus:
<br>
- The external air is heated, lowering it's RH.
<br>
- The positive pressure ensures this air with a more favourable (drier)
psychrometric is continually pushed from the inside out.
<br>
<br>
Doors and windows need to be reasonably well sealed for this to work.
Obviously, this is no guarantee against condensation build-up. Can
anybody see any error in my rationale? I would be grateful to hear of
alternative methods of control that have been successful.
<br>
<br>
Most commercially available building simulation codes can't model this:
<br>
- I'm uncertain as to what E+ can do at present.
<br>
- IES-VE can't
<br>
- ESP-r can but is very anachronistic (thar be dragons!)
<br>
<br>
Can any of the 1D Transient FEA packages model this positive
ventilation scenario? e.g. 1d-HAM, MOIST, WUFI
<br>
<br>
Best regards
<br>
<br>
Chris Yates
<br>
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