We’re building a new home (SW Virginia) with 2×6 studs on 24 inch centers. We had hoped to use 1.5 to 2 inches of EPS rigid foam to the exterior of the sheathing, then 3/4 inch x 4 inch plywood furring strips, then LP Smartside lap siding. We knew we had to use the 76 series Smartside product for the 24 inch centers. Then I discovered that LP’s installation instructions specify 1.5 inch x 3.5 inch furring strips for foam greater than 1 inch in thickness, so I guess that would basically mean a 2 x 4 stud for every 2×6 stud in the wall. This is more material/expense than we had bargained for, and perhaps also more increase in wall thickness than we want for window installation, etc. Due to some ambiguity in their instructions, I called LP support just to verify this, and yes, that’s what we need to do to be warranty-compliant. (However, their instructions also seem to indicate that you need 16 inch centers if fastening to furring strips over foam. The rep told me that 24 inch centers are fine in this scenario as long as you use the 76 series.) I asked him if we could fasten the siding through the foam and furring strip with long nails or screws biting into the underlying 2×6 studs. (Wanted to keep the furring strips so we’d still have a rainscreen air gap behind the siding.) He said that sounded like a possibility but I would need to talk to some of their higher up tech people and get a warranty variance in writing to protect myself. And then you’d have the expense of all those long fasteners and not sure how that would add up vs the thicker furring strips? So I’m kind of confused about which route to take. Here’s what I see my options to be:
1) Install according to LPs specs and use a lot more lumber. Would the improved thermal performance of the wall be worth all this?
2) Install according to original plans and hope I never need to use warranty. Anybody have experience fastening Smartside lap paneling to 3/4 inch furring strips?
3) Switch to 1 inch of polyisocyanurate for a similar r value boost, and forget about the rainscreen gap. (For 1 inch of foam or less, LP says you can nail directly through the foam to the studs.)
4) Try to fasten siding through furring strips and foam with long nails or screws. Anybody tried this? Any ballpark ideas on expense of longer fasteners vs just using 2×4 furring strips?
We’re kind of stuck and don’t have a lot of experience to guide us. Any thoughts would be greatly appreciated.
The 2017 edition of the NFPA 70® National Electrical Code® (NEC) contains a new Article 840, Part VI requirement addressing premise powering of communications equipment over communications cable. This requirement only applies when the power supplied is greater than 60W (i.e., it does not apply to IEEE 802.3 Type 1 (15W), Type 2 (30W), and Type 3 (60W) PoE implementations). In this case, the maximum current that may be carried by a cable conductor is determined by the conductor gage (AWG) size, number of 4-pair cables in a bundle, and the mechanical temperature rating of the cable as provided in Table 725.144 of the NEC and excerpted below. Note that this table is based on an ambient temperature of 30° C (86° F).
As an example, the maximum ampacity of one 24 AWG category 5e conductor, mechanically rated to 60° C and contained within a bundle of 62-91 cables, is 400 mA (800 mA per pair). Since the IEEE P802.3bt Type 4 90W application specifies a supported current of 948mA per pair, this example product and installation configuration would not be compliant to the NEC requirements for support of this application. To overcome this restriction, the NEC provides a provision to use a limited power or LP-rated cable jacket to support increased ampacity. Another alternative allowed by the NEC is to use cables having larger diameter conductors and/or a higher temperature rating to reach the desired ampacity capability.
Siemon recommends the use of its shielded category 6A and category 7A cables (having 23 AWG and 22 AWG sized conductors, respectively) for support of 60W and higher power applications because these cables offer the same application support capability as LP-rated cables with the added benefits of greater heat dissipation, power efficiency, bandwidth, and noise immunity. Note that these cables are mechanically rated to 75° C (167° F) and, according to the NEC table (refer to the cells highlighted in yellow), are suitable for support of at least 500 mA per conductor/ 1 A per pair current levels in bundle configurations of up to 192 cables in 30° C (86° F) ambient temperature environments. Siemon has developed bundling recommendations for a much broader range of ambient temperatures. Following these bundling guidelines ensures that an -LP rated cable is not required to support greater than 60W applications within the environments for which Siemon cables are rated.