Deep Energy Retrofit of 100 year old house – GreenBuildingAdvisor

We are starting a DER (Deep Energy Retrofit) on our old 2200 sq ft. house . It was built out of an old church by my Wife‘s daddy. In the early 80’s we moved it to its current location, in South East Alabama, about 90 miles North of the Florida Coast, Warm Humid Zone 3A from one of your links.

Framed with 2×4″ rough cut heart pine, no rat sills on block pier foundation and a vented crawl space and attic.

Main house:  Starting from the inside to out:

3/4” pine paneling in two rooms, 1/2” sheet rock on all others. 

We insulated it with R13 fiberglass faced insulation as there was not any insulation in the house at all. 

¾” lathes on the outside 30 lb felt then 1980s masonite siding. 

Currently the masonite siding has deteriorated as you might have suspected.

Under the floor vented crawl space R13 fiberglass faced under some rooms but it is falling down and looks bad. In the vented attic R19 fiberglass faced.

Addition:  A master suite was added a few years later. ½” sheetrock 2×6 walls 2’ on center, visqueen plastic on all walls, ceiling and under floor, R19 fiberglass unfaced, ½’ blue foam board, then smooth masonite lap siding. Foam has since developed wide gaps.

Will add Zip Sheathing, some thickness of insulation board, 1×4’ for rain screen,  Hardie or vinyl siding.

Question 1: Should I cut out the visqueen in the wall, ceiling and under floor?

The plan is to remove all masonite siding and the 30 lb felt and 12” of ¾” lath boards at top center and bottom of the walls. All old builders grade Croft windows will be removed for replacement with better vinyl windows.

I want to woodblock then Boracare and air seal the rat sill areas. Pull the Kraft faced fiberglass and remove the kraft facing and reinstall making sure to fill with fiberglass to the full 4” stud bays. Foam seal all outlets in all wall. 

Question 2: Also in the two rooms with pine siding do I need to seal the TG joints, and all around the edges to air seal since we are working from the outside? Or leave edges open so it could dry to the inside? Same question for the sheetrock in all other rooms?

We will then reinstall the ¾” lath boards to strengthen the walls, box the whole wall area edges with ¾’ to better air seal the Zip sheathing, tape and seal the zip, assure a 5 degree slop on the window sills, zip stretch tape sills and zip tape all sides add head flashing.

Question 3: I want to add some insulation to the outside, can I use 1” of Rockwool or poly-iso in my climate zone or do I need thicker? 1×4” rain screen vertical boards on outside of insulation. Hoping to use Hardie lap siding 7” reveal, or insulated vinyl siding.

We will spread plastic in the crawl space covering all ground, block in all between piers and seal all vents. A dehumidifier will be run with some exhaust air until we can completely encapsulate the crawlspace next year.

We are not doing any roof work, except adding hurricane clips on top plate to rafters and strapping studs to the sill plate. Then the third year we will address the roof and attic making it an unvented area. Adding some thickness of exterior insulation. Extend the overhang from the current 10” to 20”.

Question 4: Does this seem to be good Building Science. Am I even on the right track?

I have been following Green Building Advisor, Finehome Building and Joseph Lstiburek (Understanding Ventilation in Hot Humid Climates) for a good while planning this Deep Energy Retrofit. 

Any comments would be greatly appreciated. Good or Bad.