Lightning rod cable in SIP Roof gap & Moisture in ridge
Background: New Jersey Timber frame house built 30 years ago with SIP panels for wall and roof (Roof panels: 5-5/16’ WoodClad Winter Panel with R-value of 26). Cathedral ceiling with SIP panel interior made of T&G boards.
Roof was redone 20 years ago (traditional underlayment & shingles). The house was bought 10 years ago, and I assumed there was no specific issues found with the SIP roof panels during the re-roofing. From original construction pictures there was nothing specific done to the roof to accommodate SIP roof panels as recommended by several blogs on this web site, the Winter Panel Complete Guide to Building, and Joseph Lstiburek: taping the joints, vapor permeable underlayment, venting the ridge and the overall roof.
Leak issue: Within the past 3 years, we experienced 3 to 4 times, a small leak in the same location (ridge); few drips on the floor below, increased dark marks on the interior T&G (see first picture). Leak was observed in February, October, and most recently early July, every time after a severe storm with strong wind. The leak is situated in the middle of 2 lightning rods (20 feet apart), and originally my roofer, thinking the leak might originate from the lightning rods and cable, reseal them. For 10 months, it seemed to work. After the most recent big storm and leak, the roofer took apart the ridge cap at the location of the leak (see second and third picture): the picture shows the lightning rod cable apparently pushed into the SIP panel gap, with little or any insulation filling the gap. The roofer also identified that only the bottom of the nails were corroded at the location – which could lead to identify the issue not as water penetration but rather as moisture infiltration or exfiltration.
Temporary solution: The roofer proposed to fill the gap between the panels at the location of the ridge with insulation foam and replace the cap. This solution – for the time being – made sense and was recently implemented. The original proposal was to install a vent ridge (more on this later).
After reading many Green Building Advisors blogs on SIP panel roofing, I am only pretending to barely grasp the most current recommendations and would like to see if I could get confirmation that I am on the right track for the next steps.
Lightning rod cable: Should I assume that this cable might be part of the problem as it provides a colder surface just at the ridge panel gap and induce more condensation of the moisture? As there was no observation of moisture issues during the coldest days of the year, should I assume the issue is mostly moisture infiltration. Would a good insulation of the gap resolve this problem without having to move the cable from the ridge?
Next Step: Overall Ridge Gap Insulation and venting.
The SIP panels R-value of 26 is not up to current building code (barely half of what is expected) and is an issue that I might consider addressing in a future re-roof. However, before re-roofing I am considering insulating the SIP panel ridge gap properly on the overall ridge length and install a ridge vent – making sure also the roofer install a vapor permeable underlayment on top of the gap. Does that make sense?
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