嗨了。你可能还记得，我住在马里兰州的巴尔的摩，正在计划扩建我的房子。我住在一栋建于1938年的砖石承重房里。我认为这也是一个改造我的房子的机会，这将使房子成为一个完整的系统。我一直在考虑做一个“链锯改造”/PERSIST，除了没有链锯，因为我现有的屋顶没有悬挑或拱腹，只有山墙末端的窗户通风。在移除现有的屋顶(需要更换)后，我会将整个房子(现有的和增加的)(即，我所有的屋顶覆盖，2-wythe砖墙和砌体-也许AAC -增加)与一级(是的，perm<0.1)阻汽器(与Joe Lstiburek的“完美墙”和在潮湿的南方的蒸汽控制建议保持一致)，将小阁楼空间变成一个条件空间，然后把完全的外部绝缘材料(我想是矿棉，因为它具有良好的拒水性、防白蚁性和防气体性)放在顶部，然后用水垢形成雨屏缝隙，然后是覆层(现有屋顶的瓦，也许是南向的金属冷屋顶，墙壁用板条和灰泥——用砖在现有的房子上抹上“粗糙的灰泥”，以保持现有的外观)。对于屋顶的外部绝缘，你能在那里安装多少英寸的绝缘材料? I see Joe Lstiburek and Betsy Pettit point out that 6″ of polyisocyanurate (faced R 6.5) can get you to R-40, which passes the R-38 for code. I also see that the REMOTE manual uses 6″ of foam insulation. But I’m not thrilled by its gradual loss of R-value and that the pentane that is off-gassed might contribute to smog in my city. But I see that Martin in his blog writes that the PERSIST system has been used up to 8″ of external roof deck foam with a further 2″ thick sleepers. This would mean 10″ below the shingle nailing bed. And I can use R-4.2/inch mineral wool or rigid board fiberglass for 9″ and have the 1″ drainage gap and so pass code with the same 10″. I like to be able to see the underside of my roof sheathing from the attic space, and feel for moisture, as well as to keep mineral fibers as much out of the conditioned space as possible. Mineral wool would also give better vapor permeability compared to foam, to allow drying to the outside. If I found appropriate structural screws to go through the plywood/OSB and then 10” of drainage space and rigid board insulation, could this work? Are there such screws? Is there a limit to the above deck thickness for any other reasons? I would of course pass this by my structural engineer, but I am interested to know the experience in the green building community.