请求对翻新双壁设计的评论
大家好，
我在设计阶段的全屋改造of a 1964 ranch in Evergreen, Colorado (high and dry, Zone 5B, but right on the edge of Zone 7) and would appreciate any comments on a proposed wall design. The existing home’s walls are 2x4s with 1/2″ fiberboard and plywood siding on the exterior and 1/2″ gyp on the interior. Cavity insulation is old rockwool batts. What I’d like to do is remove the drywall and rockwool, fill the existing cavities with blown-in cellulose, sheath the interior of the existing walls with 1″ XPS, frame a new 2×3 wall, 1″ off the interior surface of the XPS and insulate that wall (and the space between the new 2x3s and XPS) with mineral wool batts. I’ve attached (I hope) a sketch of what I’m proposing. I’d like to leave the existing fiberboard and siding in place. The XPS would be the air barrier, taped at all seams, floor and ceiling air barrier and to the new window bucks/gussets.
After reading Martin’s Sept. 17, 2010 post “Are Dew Point Calculations Really Necessary,” I used the suggested simple method to calculate the temperature of the inside surface of the XPS, as I would think this is the critical condensing surface. The materials outboard of the XPS have significantly higher vapor permeability. Using the average of Dec., Jan., and Feb. mean temps as the exterior temp (about 28 degrees, in our case) and 70 degrees and 35% as the interior temp and relative humidity, I calculated that the interior surface of the XPS is about 54 degrees. The dew point for 70 degree air at 35% humidity is about 40 degrees, so my wall is above the dew point. No problem, right? Just to be conservative, I did the same calcs with the average low temps for Dec., Jan., and Feb., (about 13 degrees F) and got a temperature on the inside of the XPS of 47.6. Still above the dew point. Then to be really conservative, I ran the calcs at an exterior temp of 1 degree F (the design temp for Heat Loss Calculations at my location). Temp of inside face of XPS at 1 degree outside: 43. Still above the dew point. So, this is good, right?
我喜欢墙设计的是从房屋内部的内部构建它的便利性，它给我带来了2×3（实际上是2×4，因为螺柱是从空气屏障中站立的）追逐MEP物品，在保护空气屏障的同时。我需要考虑任何缺点吗？
我基本上是在自学这些东西，并在我继续前进时弄清楚，但是这将是一个发表评论的好论坛。改建将不会获得被动房屋认证，但是这些原则大量了解了设计。
感谢您在此网站上提供的所有重要信息。我期待您的答复。干杯。
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Replies
杰森，
Your plan will work. It's your house, and you should proceed as you prefer.
My own preference on this type of retrofit is to work from the exterior, not the interior. The main reason: a continuous layer of exterior insulation deals with rim joist areas and partition intersections. If you are working from the interior, it is much more difficult to insulate these areas.
从外部工作也为您提供了更好的空气密封机会。
杰森，
看来您对此有很多很好的思考。我必须同意马丁的观点，在这种情况下：最好在外部工作。考虑在外部添加4英寸扩展的软木隔离或矿物质羊毛。可以在您的胶合板/纤维板层上涂上高质量的膜WRB，以充当WRB和空气密封层。然后添加软木或MW该板条拧紧穿过板条 - 绝缘 - WRB，并进入框架。您的壁板挂在板条上。
这个系统：
消除墙壁上的所有热桥梁。（您仍然会有屋顶和基础桥梁。
从长远来看，单个空气飞机的性能会更好，因为您现有的框架中的所有电气都必须在每个服务点都穿透XPS气势屏障。
外部空气屏障可以直接连接到基础的外观，无论是平板还是爬行。没有内部过渡可以解决。
Cork & MW maintain a good level of permeability from your existing sheathing outwards.
Both Cork & MW will resist fire vs exterior foam.
An exterior layer of cork & MW are better at sound isolation.
Windows can go in a "buck" and can be "innies" (which perform better thermally as you know from PH training?)
I think that working on a single exterior plane will be less complex in air barrier and the number of layers and "builds" Less complexity usually comes with a lower overall cost and will probably be completed faster. Couple that with superior thermal performance by thermal bridge elimination and it really looks like a better option.
祝你好运！
Martin and Albert,
Thanks for the quick replies. Based on your responses, I'm going to take a much closer look at exterior insulation possibilities.
这房子是一个瘦（60'x21'）牧场，我们将重建整个屋顶结构：卸下现有的4:12臀部屋顶，并用2:12的棚屋屋顶代替。这使鳞片以两种方式倾向于内壁：1）它消除了内部的任何隔离墙，这意味着我可以确保在房屋周围一直保持连续的空气屏障。2）新的2x3墙将由打捞和重新燃烧的2x6天花板和屋顶框架成员建造。几天，有一个指甲拉杆，我的赛道锯和桌子锯，我得到了一大堆免费的木材。笔直，干，1号或更高。此外，整个轮辋托梁都在全高地下室中暴露出来，我正计划闪烁和巴特。我认识到它比刚性刚性更不连续，但是有了仔细的细节，我敢肯定，我可以正确处理。实际上，我打算在隔离边缘区域之前使用Rissan胶带所有角落和缝隙。
But, on the other hand, reframing the roof allows me to make the air barrier continuous over the top plates of the existing walls. Additionally, there is one interesting condition to the house that I could take advantage of...In over 50 percent of the perimeter of the house, they held the floor and wall framing back from the outside edge of the foundation wall, so as to provide a brick ledge. There is 4 inches of the top of the 8" foundation wall exposed. That ledge would provide for ease of placement of any exterior insulation and would keep the new siding very close to the plane of the outside of the foundation wall.
安装舷外隔热材料的主要关注点是通过4-1/2英寸的矿物羊毛和纤维板撞击。我挂了数千平方英尺的GYP墙板，我比我想念的更频繁地错过了螺柱。我只能想象要确保足够的固定而无需跑步就可以检查每个螺栓的闪光灯，这是指数级的。有人有这个经验吗？我在想吗？大概。
Decisions, decisions.
Cheers,
Jason