水分控制困境：DIY步入式冷却器
I’m helping a great non-profit (www.nourishnc.org) create an 8’X8′ DIY walk-in cooler in an unconditioned warehouse. Plans include: 2×6 construction, R23 Roxul insul, wrapping the exterior of cube in Grace Ice and Water Shield, and a really nice, donated commercial refrigerator door. Interior is FRP (fiberglass reinforced panels) glued to 1/2″ OSB. Temperature of 35-40 deg F will be managed with a 12K BTU window a/c controlled by a “CoolBot”.http://storeitcold.com/
问题：
Presumed goal is to eliminate warm, moist air from infiltrating structure (thus, the Grace air barrier). But since interior holds perishable food, it needs the FRP for sanitation. Moisture barriers on both sides of these walls seems a really bad idea! So, do I place some sort of interior vents between the studs, and count on the a/c to dehumidify, or will adding vents just invite moisture into the structural elements?
I’m beginning to see why most commercial coolers are closed-cell foam with a stainless steel skin! In this case, cost was prohibitive. Need your thoughts!
Karl
Wilmington, NC
GBA Detail Library
由气候和房屋部分组织的一千个建筑细节的集合
答复
卡尔，
In this case, the direction of the vapor drive is from the warm, moist exterior toward the cool, dry interior. So the vapor barrier belongs on the exterior of the assembly. That's a good place to put your Ice & Water Shield. So far, so good.
If you do that, I wouldn't worry too much about the fiber-reinforced plastic (FRP) panels on the interior. I doubt whether they will cause any problems.
也就是说，使用SIPS或用螺柱上的刚性泡沫绝缘构建冷却器的最佳方法（而不是螺柱之间的Roxul绝缘材料）。泡沫绝缘材料不受水分问题的影响，您的计划（带有Roxul绝缘的螺柱墙）没有高R值，并且在螺柱上有热桥梁。
在安装FRP面板之前，您可以考虑在螺柱的内侧安装连续的刚性泡沫绝缘层。
感谢马丁。我的偏爱也是SIP，但无法使它们成为该项目的实现。我们确实选择了24英寸中心，单上板和两个扎根的角。令人惊讶的是（是否不是？），R25是冷却器的行业标准，R32用于冰柜。好奇地看到了这一过程随着时间的推移如何表现。
I would be in favor of vents through the FRP to allow the interior of the wall to dry, if you can get away with that from a sanitary/cleanability perspective. But given you that don't have to worry about things like rainwater getting in through poor window flashing, allowing the interior of the wall to dry isn't a high priority.
Polyiso在此应用程序中难道不太好吗？一开始，高的R值不足以看到R-Value的降低，箔脸的外观将提供VB，相对较低的成本。我记得读过一篇文章，乔·L（Joe L）写了关于酒窖结构（最佳温度和湿度略高）的文章，我记得他推荐了Polyiso。
乔纳森，
As I wrote in my answer, any type of rigid foam insulation (including polyiso) would make more sense for this application than mineral wool.
Agreed Martin. I was just wondering if it is the best of the foams. It has a higher r-value the XPS and EPS, especially at the temps used in this application, lower GWP than both and easy to get foil faced. I have not priced it out, so I am not sure how it compares on that front.
Our project was constrained by the need to obtain supplies locally when possible, and to minimize cost. We estimated 5" of EPS board in the floor, roof, and walls of our 8X8 cube would cost around $1500- triple the cost of the Roxul. I later found a business in Cleveland that offered me 10 used commercial panels for $1900, enough to build the entire cube. These assemble really fast via a locking mechanism, but my timing was off and the materials had already been purchased.
I'm continuing to ponder venting the interior walls/ceiling. Assuming I am able to tightly seal the exterior, the only air entrainment should be when the door is opened. In that case, condensation should only occur on the surface of the FRP, and should readily dry as the a/c dehumidifies the room. So maybe interior vents between the studs would be a bad idea after all! Opinions on this?