Mold on inside of plywood sheathing
I recently purchased a super insulated house in the Concord, NH area. The house is 3 years old. From my investigation and discussions with the previous owner the wall system is double stud insulated with 3 layers of 3.5″ Roxul Comfortbatt. The sheathing is Huber Zipwall with taped joints. The siding is cement board clapboards nailed directly to the sheathing. The inside is drywall and I’m told gasketed at joints and electrical outlets. there is no interior vapor barrier and the paint appears to just be regular latex. We use the HRV and we keep it pretty dry in the winter, around 35-30% humidity, sometimes 25%.
根据我在此网站上完成的阅读，我了解到双螺柱墙系统可能会在胶合板护套的内部引起凝结问题。我在今年八月进行了一些调查，可以肯定的是，我注意到胶合板内部的一些黑色霉菌斑点。胶合板和绝缘材料感到干燥，但肯定有一些孢子黑色的霉菌。
After a long winded background, my question is: do I have a minor or major problem here? Do I need to rip the siding and sheathing off and put a rain screen on? or is a little bit of mold okay if the sheathing is drying out each summer and it’s sealed in by the drywall? No one in my family has complained about mold allergy reactions but it still makes me nervous. Thoughts?
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答复
Sounds like construction moisture that is now gone. Post pictures, have someone check it out. Have the builder come by and see what he has to say.
Where is the mold, north side a botom of walls?
Tell us more and more pictures...
我们在我附近有一个发霉的木屋...一家模具拆除公司来了...做得很好，现在的房子很好...它在5年以内的无热量中发霉，主要是在成品的酒窖墙壁上和地毯。地毯被扔掉，清洁了墙壁。完毕。
Rain screens are great but that retrofit will be expensive as all get out. I would think tens of thousands of dollars.
You do not have plywood, it is OSB a better version of OSB... Actual plywood is a better product IMO than OSB which is the least expensive sheathing and why used. Zipwall is a great improvement of OSB. I still have concerns if it gets hit with moisture from and on the back side. The new idea is to place the sheathing in between insulation so it does not condense water out of moist air.
帖子图片...您可能没有问题，这可能是在新框架中干燥期间发生的事情。帖子图片。
Cement board siding might not be the best choice to apply over a build like yours. Expensive choice too. I wouldn't build what you bought.
I see many holes in the story. For starters there's no mention of humidity measurements during the spring, summer and fall month's. Only winter.
Mold is good, right? It helps you identify a problem.
Your answer for a "properly" constructed "tested" double wall system may be right here....
http://www.buildingscience.com/documents/information-sheets/high-r-value-wall-assemblies
http://www.buildingscience.com/documents/information-sheets/high-r-value-wall-assemblies/high-r-wall-04-double-stud-wall-construction
:)
Aaron,
I agree with the other comments. We need more information.
但是，如果您的家人中没有人生病，并且在我看来，旧的霉菌斑点是无害的，那么旧的霉菌是无害的。
Thanks everyone - I'll make get back into the wall and take some photos. Hopefully the mold is from the moist construction environment as I was told the house was dry-walled in late fall and not finished and moved into until March which means that it went through at least one winter with high indoor humidity.
为了回答有关春夏湿度的问题，我们不会运行很多交流电，因此湿度通常是外面的。我也只运行HRV进行淋浴。整个夏天，读数平均为60％和70％。
Another piece of info is that the previous owner told me the blower door came in around 1.25 ACH
我想我会密切关注它，看看模具是否增加并开始腐烂护套。显然，我真的不想改装雨屏。如果问题变得更糟，我还有其他选择吗？不幸的是，由于房屋的完成，我目前无法改造建筑科学所暗示的。
也许这可以帮助您了解房屋内部的霉菌，以及为什么需要控制湿度。马丁，您可能还想看看这个旁注。
60%到70% rh很高,“我认为”马丁将agree.
http://www.absoluteresourceassociates.com/standard%20OF%20Care%2012_13.pdf
Surface Mold and Other Biological Growth
The following conditions are necessary and sufficient for mold and other biological growth to occur on surfaces:
mold spores must be present
必须有营养基础（大多数表面含有营养）
温度范围在40（4.4°C）和100°F（37.7°C）之间
相对湿度与70％以上的表面相邻[2]
http://www.buildingscience.com/documents/digests/bsd-012-moisture-control-for-new-residential-buildings?topic=resources/more-topics/mold
Richard - thank you for the information. I understand why mold grows and I know why its on my sheathing. My concern is whether or not I have a BIG problem or a moderate problem. ie, should I plan on ripping out siding soon or simply keep an eye on things over the next couple of years. The responses regarding construction moisture make the most sense to me and hopefully that was the culprit. Especially given that the zipboard is dry right now at the end of the summer. Knowing that this is an issue, next summer I will make a point to run the AC or a dehumidifier a little more often (which pains me to waste the energy on)
Also - FYI my estimate of 60% to 70% was for the dead of summer. I would estimate that the typical humidity through spring and early summer and then fall averaged 50%. Currently, its 30-40% in my home and like I said, its 25% to 30% in the winter.
您需要在淋浴和沐浴后至少20分钟去除浴水水分。
您的湿度与也不使用AC的任何人一样。
Your humidity is fine.
Run your bath fans longer. Buy digital timer switches and get all to always use them. You have an HRV.... a bit different... use it on high for and after shower use.... Use it.
我的赌注一切都很好。
您没有指定是否打开北侧，以及它是否仅在墙壁的底部。请发布更多信息！
您需要连续运行HRV，全年，24/7，浴缸开关从低至高点增加几分钟。仅凭您观察到的原因，仅此一项就可以降低您的湿度水平，并且在您的房屋中降低内部湿度水平至关重要。
壁板应安装在雨屏上。造成这种情况的原因有很多，但是一种是减少壁板背面的水分积累，这可能在正确的条件下导致护套腐烂。第二个原因是在您所看到的时促进内部水分的干燥。随着时间的流逝，我将其放在要工作的事情列表中。
我在该地区，如果您愿意的话可以看房子。
Bob,
您写道：“您需要连续运行HRV，全年24/7，而浴室的开关可以使跑步模式从低至高点增加几分钟。仅此单单就可以降低您的湿度水平。”
Your advice is not quite right. While operating an HRV during the winter months will lower indoor humidity levels, it won't help during the summer.
康科德（Concord），在夏季，NH会变得炎热潮湿。如果您在炎热，潮湿的天气中以24/7的速度操作HRV，您将提高室内湿度水平，而不会降低它们。您操作通风风扇的越多，您的房屋就会越潮湿。
高湿度比不不太常见的NH中部ar the coast, although we do get high humidity on occasion. If the house is conditioned by air source heat pumps (mini splits), they will reduce the humidity as part of either the cooling or drying modes.
我担心的是房主决定通过偶尔使用通风设备而不是作为建筑系统不可或缺的一部分来最大程度地减少电气使用。当我意识到它们通常被关闭并且很少使用时，我停止使用定时浴风扇排气系统来支持HRV。