[GSBN] Straw-Bale Blower Door and Infrared Test Results

[Derek Roff]

Thank you, John.  I appreciate your response, and your additional 
information.  I continue to learn valuable information from you, and 
from this list.  My gratitude to all of you.

Happy Holidays,
Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu


--On Saturday, December 25, 2010 1:05 AM -0500 jfstraube 
<jfstraube at gmail.com> wrote:

> Glad to say something useful to you Derek.
> Point 1. Condensation hidden in walls can occur anytime any leakage
> occurs (over 0 ACH50) but the quantity of airflow needed to create
> widespread condensation is enough that it requires a leaky house,
> eg over around 3.   A local leak in a 0.6 ACH50 house will still
> cause icicles and rot, but over a very limited area in an otherwise
> nearly perfect house.
>
> Point 2. as houses leak more and more, the interior moisture
> production is diluted by cold dry outside air and so the RH drops.
> In normal occupancy houses of average 2500 sf and higher size,
> leakage rates of 5 or 6 result in RHs that are "dry", perhaps 25%
> or so, which prompts people to buy humidifiers. If they succeed in
> raising the RH, the high leakage rates can cause some serious
> interstitial wetting. As the leakage rates exceed say 12 or 15, the
> RHs are always so low, even with an additional humdifier that
> condensation does not occur very much, and the house is
> uncomfortably dry and drafty (this is a description of an old
> house).
>
> Point 3. cfm50/sf is a better metric of enclosure performance
> because it normalizes the results for complex and simple enclosure
> alike.  ACH only normalized for volume.  CFM50/sf  captures the
> shape and volume to area ratio of the building.  This really
> matters with large vs small houses as well as sprawling vs compact
> forms.  CFM50 total is a very good measure of total building
> performance, perhaps the best because it rewards small and simple
> buildings.  But CFM50/sf is the best measure of the enclosure
> performance (as opposed to building).  Hence I think both numbers
> are best: total for the whole building performance and CFM50/sf for
> enclosure tightness.
>
> Hope that explains my comments.
>
> On 2010-12-24, at 11:45 AM, Derek Roff wrote:
>
>> It's a great pleasure and education for me to read messages from
>> John Straube, and all the others who have posted recently.  John,
>> I would like to request clarification of a couple of points from
>> your posting below:
>>
>> "... houses over about 3 ACH at 50 tend to have a risk of
>> interstitial condensation. Rates over about 5 or 6 tend to be dry."
>>
>> Is this saying that houses between 3 and 5 ACH at 50 have problems,
>> but both above and below that, moisture problems are less likely?
>> That seems counterintuitive to me, hence I suspect that I don't
>> understand.
>>
>> I would also be grateful if you would say a bit more about why
>> "cfm50/sf is better [a better metric]".
>
> John Straube
> www.BuildingScience.com