Context:

Siding replacement in small house in wooded mountain area of Western North Carolina – Climate Zone 4 (About 100” average yearly rain).

Current siding is board & batten wood (overall thickness: 1.5”) over house wrap and OSB installed on 2×6 frame. The existing siding need repairs to replace rotted wood in various areas as well as a complete paint job, Additionally, IR measurements/pictures show a lack of insulation in all exterior corners as well as thermal bridging of the studs.

Consequently, we are considering a complete replacement of the board & batten siding with a material providing minimum maintenance requirements (same profile), and additional rigid insulation on top of the house wrap. This would provide us with the capability to check and correct the OSB/House wrap installation if needed, a better overall insulation, and minimum overall maintenance requirements.

The considerations for this new siding are as follows:

·      The choice and durability of material colors,
·       Additional rigid insulation (stand alone or integrated into siding like insulated vinyl),
.       A good rainscreen,
·        Consideration of the overall 1.5” thickness of the existing siding and minimization of impact on doors and windows flashing
·      Cost of materials and labor.

We are considering the following 2 options:

·         insulated board & batten vinyl siding (we have a good prior experience with insulated vinyl siding),

·         rigid insulation with board & batten PVC siding such as Celect from Royal.

Question 1: Do we need an additional rainscreen with insulated vinyl siding or vinyl / PVC siding installed on top of rigid insulation?

Martin Holladay and Peter Yost have pointed out that regular vinyl siding would not need a rainscreen. Martin states that: “vinyl siding does not require a rainscreen installation unless it is installed on top of rigid foam that is more than 2 inches thick”. Peter states that “even without any dedicated airspace furring strips might provide, there is plenty of space for bulk water to drain between the (vinyl) siding and the WRB and for air to move quite freely behind the cladding”

Like standard vinyl, insulated vinyl siding or PVC siding requires at least 1/32” between the head of the fastener and the nailing hem of the panel, so they are rather “hung” like Peter Yost said. However, the space behind regular siding is filled with foam in the case of insulated vinyl siding and the space behind PVC siding is only about 1/8”. As such, can we reach the same conclusion with those sidings than with regular vinyl siding? The manufacturers appear to be answering positively.

Question 2: If a rainscreen is needed, would furring strips be the most efficient and if so, what would be the minimum thickness?

As the siding would be vertical, the furring strips would be horizontal and would need to be notched – which seems rather time consuming. What would be the recommended spacing on the notches? Any other options?

Question 3: Choice between insulated vinyl and 1” rigid foam insulation with PVC siding.

Martin Holladay has stated that insulated vinyl is a bad solution as the insulation is not really pushed against the existing sheathing because of the “hung” factor (I am only paraphrasing as I cannot find the right quote). Insulated vinyl will only provide 3/8” of insulation and about R2.5 of insulation. As such, it is likely that 1” rigid foam insulation (R-6) with PVC or would be better that insulated vinyl siding – not only due to the added R value but also due to a better installation. When we consider the added material and installation costs (for 20 square of wall surface, the rigid insulation will likely amount to an additional $1,500 of materials), would this still be the preferred choice?

Thank you.