Installing insulation board over cedar siding on unsheathed & uninsulated (filled with brick) walls of 1890s farm house
Hi. I’ve been trying to read up on the best way to add insulation to the walls of an 1890s farmhouse but I haven’t come across a similar situation/reply.
The farmouse has balloon framing with plaster interior and cedar siding exterior that was then wrapped in aluminum siding 40 years ago. The walls have brick nogging in them (all bays completely filled with low grade brick and unfinished mortar joints). As an fyi, the wall studs are 4.75″ x 2″. As you can see this wall has a very minimal R value. Since we are looking to replace our 36 windows I thought it would be a good time to replace the siding, rather than paint the aluminum.
The plan is to remove the aluminum siding, leave the cedar siding in place (since that is essentially the sheathing) and then add housewrap along with the thickest layer of EPS foam allowed by the siding company. We were looking at a cementicious siding product but that cannot be installed over existing siding and the cost to remove all of the cedar siding and resheath the entire house is cost prohibitive for us. Our search has led us to Royal’s Celect siding product and currently they indicate a maximum insulation board thickness of 1″ over existing siding. I’m trying to get them to approve 2″ insulation board by using thicker/longer fasteners but I haven’t heard back yet.
I was on GBA’s calculator page for figuring out the maximum insulation board requirements and nothing relates to my situation. If I had the money I would tear off all of the siding, remove the brick nogging and insulate the stud cavities and resheath the house, etc…, but I cannot afford to do that. So my loaded question is: given my situation, am I doing this the best way to increase R value without compromising moisture problems (based upon GBA’s recommendation that insulation board needs to be thicker) or would you recommend a better solution? Thank you.
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