Wall section analysis in Philadelphia, PA

C. Furtaw · Post by **C. Furtaw** » Thu Jul 21, 2005 2:33 am -1100

I am new to WUFI sofware and as yet have not received my manual therefore I don't want to go too far on any analysis.
I would like to analyize the following:
Using a Sandstone from your database the wall section is the following:
4" to 6" Sandstone with mortar behind the 4" stone for stability. Their may be some air spaces behind the stone because of the random thickness.
15# felt (30 minute)
Tyvec
1/2" OSB
R 19 insulation
painted gyp board or Cherry paneling
The building is two storys high and is close to Philadelphia.
What types (how many) of analysis should I perorm to determine if there is any trapped moisture in any of the building components.

Hartwig M. Kuenzel · Thu Jul 21, 2005 11:20 pm -1100

Dear Mr. Furtaw

There are 2 possible moisture problems that you should check, interstitial condensation in winter and solar vapor drive in summer.

To assess interstitial condensation problems in winter, select a north orientation and start your simulation in October and continue for at least 2 years with the climate data for a cold year. If there is a problem it will probably be the water content of the OSB.

To assess inward vapor drive (summer condensation), select the orientation where wind driven rain load and solar radiation are the highest. Choose the climate data for a hot year of your location and start the calculation in April. Again do the simulation for at least 2 years. If the dynamic water content in any layer of your assembly is still rising after 2 years, repeat the simulation for at least 5 yaers. After the simulation you should check the water content and the RH of the OSB and the gypsum board, because these are the locations where a problem might occur. It is alway helpful to watch the film during the simulation in order to see where and when the peaks in RH and water content appear.

good luck with your simulations!

Hartwig M. Kuenzel

C. Furtaw · Post by **C. Furtaw** » Thu Jul 21, 2005 11:53 pm -1100

Hartwig,
Thanks for you rsponse, I'll let you know how I do.
Charles Furtaw

C. Furtaw · Post by **C. Furtaw** » Fri Jul 22, 2005 12:37 am -1100

At this point I have two new questions:
1. The material used in the actual building is a Mica-Schist but there is no database listing for this material so I am using the Worzeldorfer Sandstone. Since the Sandstone is not uniform in thickness I have included a 10 mm air layer behind the Sandstone. Is this correct?
2. The building wrap is Tyvec that has either 28 perms for commerical wrap or 58 perms for housing wrap. The data imput screen for a vapour barrier has the perms listed as .039 perm/inch. What number should I use for the permability data value?
Thanks,

C. Furtaw · Post by **C. Furtaw** » Fri Jul 22, 2005 12:47 am -1100

One last question (I think)
The batt insulation is R-19 and 6.5" thick. Shall I use the default value from the N.A. data base for the insulation and increase the thickness to 6.5"?
Thanks

C. Furtaw · Post by **C. Furtaw** » Fri Jul 22, 2005 3:04 am -1100

Hartwig,
I ran two analysis as you suggested and I assume that I have used the correct parameners. The results follow below:

OSB cold years water content 4.44 lb/cf to 8.58 lb/cf
OSB warm years water content 4.00 lb/cf to 6.66 lb/cf

Gyp Board cold years 0.15 to 0.39 lb/cf
Warm years 0.15 to 0.39lb/cf
The hunidity for the gyp board was about the same in both runs with a low of 40% RH and and a high of 60 % RH (all +/-)

With the reults above what can you tell me about the wall system and is it functioning properly?
Thanks,
C. Furtaw

Hartwig M. Kuenzel · Mon Jul 25, 2005 1:43 am -1100

Charles:

The water content in your OSB is below the critical limits for rot (appr. 11 lb/cf). However, there might be some mold growth if the water content exceeds 5-6 lb/cf for more than 4 weeks in summer when the temperature is high. In winter there won't be a problem because the OSB is too cold.

Hartwig

C. Furtaw · Post by **C. Furtaw** » Mon Jul 25, 2005 2:08 am -1100

Hartwig,
Thanks for the reply and I have a few questions.
1. Where did you find the critical limits for rot in the OSB at 11 lb/cf ?
2. What can be done to stop the water (moisture) migration to the OSB if possible. Also, is mold growth normal?
3. I also posted two other questions in the fourth and fifth posts in this forum that were not answered.
Thanks,
Charles

Manfred Kehrer · Tue Jul 26, 2005 8:40 pm -1100

C. Furtaw wrote: 3. I also posted two other questions in the fourth and fifth posts in this forum that were not answered.
Thanks,
Charles

Dear Mr. Furtaw,
the two unanswered posts you mentioned deal with some US specials so i think we Germans are not the best to consult. I will talk to Achilles to help you in this Forum.

You know you are the only WUFI® User of the US in this Forum at the time, because actually we will start this only now. But i´m confident that this will change and you will have WUFI® User from US to exchange experiences.

Best Regards,

Manfred

C. Furtaw · Post by **C. Furtaw** » Wed Jul 27, 2005 12:36 am -1100

Manfred,
Thanks for the reply and please ask Achilles to contact me.
I am pleased to be the first from the US to be a member of your forum.
Charles

WUFI