What is the best combination to renovate my 1950 modern home?
Our one story 2,000 sf modern home was built in the Boston area in 1950 with a thoughtful floor plan stretched east-west, with lots of glass facing south, and a small amount facing the other orientations. We plan to add a study, half bath, screened porch and bring the laundry up from the basement so that we can more easily “age in place” for twenty years. A few years ago we replaced the tar and gravel roof with a white TPO membrane on PIC roof sheathing. The original Hopes-type steel casement windows continue to grow mold despite quality storm windows and most of the cranks are broken. I plan to replace them with fiberglass windows, triple pane if possible. The 2×4 stud walls on the south, west and north sides support a mono-pitch 2×10 “cathedral ceiling” roof. Those walls are sheathed with 1x8s and covered with 1×4 T&G fir vertical siding. The east wall was built of exposed 8″ CMU. All rest on a 10″ CIP foundation without insulation. The basement has been dry for the 16 years we have lived here. There is a three foot tall crawl space under two bedrooms and a bathroom, and the master bedroom, bathroom and family room are SOG. The house was built with reasonable length roof overhangs above the south-facing windows. I plan to fill the rafter bays (unvented roof) with CCIPF, for R60-R65, including the new sheathing above. What I can’t decide is how much R-value and type of insulation to put in the walls and on the foundation. Due to some irregularities and numerous perforations, I plan to seal the rim joists with 3″ CCIPF. One source thinks it is possible to very carefully fill the 2×4 walls with CCIPF for R23. If the GWB and sheathing aren’t then blown out, should I then add 3″ PIC to the exterior to get to R42, or instead should I do the two layers of 2″ PIC outside dense-pack cellulose or OCIPF for R40? If the triple pane windows are just too expensive, should I similarly scale back the walls to R26-R30? After adding board insulation outside the sheathing, I plan to install vertical siding to maintain the original design of the house. What are people’s experience with fiber cement siding vertically? What would be the best air barrier/drainage plane to use? I can’t use vertical strapping under vertical siding, so I am considering using Home Slicker instead. I am concerned that this will be squishy to nail through the PIC, so I assume a layer of 3/4″ plywood would be needed outboard of PIC sheathing. Are there better solutions to vent vertical siding? On the CMU wall, I’m thinking of using EIFS, but should I pour Perlite in the voids and add insulation on the interior side? If so, how much? Do I need a vapor barrier there? Thanks in advance for your insights.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part