[Bldg-sim] Condensation in heritage buildings - best practice

David Bryan DBryan at AmerIndian.com
Tue Dec 2 10:49:30 PST 2008


Chris -

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. 

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 

dbryan at amerindian.com 
www.amerindian.com 

<http://www.amerindian.com/>



Chris Yates wrote:
> Hi
>
> 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).
>
> My rationale is thus:
> - The external air is heated, lowering it's RH.
> - The positive pressure ensures this air with a more favourable 
> (drier) psychrometric is continually pushed from the inside out.
>
> 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.
>
> Most commercially available building simulation codes can't model this:
> - I'm uncertain as to what E+ can do at present.
> - IES-VE can't
> - ESP-r can but is very anachronistic (thar be dragons!)
>
> Can any of the 1D Transient FEA packages model this positive 
> ventilation scenario? e.g. 1d-HAM, MOIST, WUFI
>
> Best regards
>
> Chris Yates
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