Zone 3 re-siding – exterior insulation options
Hi everyone – my name is Loren. I’ve learned a ton about energy improvements for an older home from this website – thank you for creating such a valuable resource!
I’m seeking guidance and advice on alternatives for adding insulation and improving air/vapor sealing to my home while some walls are being re-sided. Some details:
• 1964 construction, Climate zone 3 (Atlanta), 2 stories (2,330 SF), 600 SF basement w/adjacent
crawlspace. Graded “leaky” in energy assessment done 5 years ago (CFM50 = 5050 N = 17.2
ACH natural .71)
• 2×4 stud walls – drywall, fiberglass batts in cavities, Celotex blackboard sheathing
• Front and side walls of 2nd floor are cedar siding, rest of exterior cladding is brick.
• Current windows are all original wood, single pane
• Ventilated attic (ridge vent), no attic ductwork
• Recently replaced HVAC – variable-speed heat pump/condensing furnace. Even with the featured
humidity control of the variable speed compressor the unit still went into “overcooling mode to lower
humidity levels this past summer.
• Wife and I both have some respiratory sensitivities – improvements in air quality from envelope
sealing are valued.
Current project underway:
• Extend 2nd floor front balcony (and roofline) rom 3’ to 7’.
• Replace siding with Hardie fiber cement board
• Update 48” French door in one BR, replace double windows in other BR off of balcony w/matching
French door, install larger window (bathroom) between the French doors.
Unplanned add-ons as project evolved:
• New standing seam metal roof
• Replacement windows (4) on 2nd floor end walls
Tentative plan for improving the walls (formulated from advice here):
• Remove Celotex sheathing
• Replace old FG batts in wall voids with mineral wool batts
• Re-sheath with OSB (tape seams)
• Apply WRB
• Flash windows
• Install 1” of foil-faced Polyiso foam to exterior walls (tape seams)
• Install fiber cement siding
I’m not set on any material or approach on the walls – and I’m willing to invest more for incremental performance where it makes sens from a cost/benefit standpoint. I also want to ensure the siding contractor my GC is considering will handle the install properly – so, I need to explain what we want accomplished in terms a professional tradesperson understands.
What are thoughts and opinions on a plan for insulating the 2nd floor walls?
Thanks – and I truly appreciate your help!
PS – After the current project I see myself using a “cut and cobble” approach to sealing the rest of the walls in the house (behind brick exterior) over time as rooms get rehabbed and re-windowed (https://www.energyvanguard.com/blog/how-to-fix-a-leaky-underinsulated-exterior-wall). And I still need to seal up the attic.