Amid all the excitement of falling trees and my rising trailer inventory, I have actually been working on Sparta. The twelve volt circuits are all wired. There are three of them – one running aft, one midship and the other powering the forward cabin, better known as the observation lounge (that continues to crack me up). They are nearly balanced in terms of load and supply virtually all the lighting (interior and exterior), the various fans, the water pump and the belatedly installed water-storage tank warmers. What remains are 2 or 3 120v circuits to supply all the A/C outlets, keeping in mind GFI in kitchen/bath, the refrigerator and possible microwave (I’m still on the fence about that).
With the relatively brief task of 120v wiring looming, it is not too early to contemplate next steps – specifically insulation. Unlike 1957 when the choices were fiberglass, rockwool and shredded paper, now there are a plethora of insulation choices, each with their own merits. There remains the fiberglass option, which I have already installed below the subfloor, and then the following:
- Fiberglass Batts and Blankets. R-value: 3.0-4.0 per inch (R-13 for a 2-by-4-framed wall). Cheapest
- Rockwool Batts and Blankets. R-value: 4-5 per inch (R-15 for a 2-by-4-framed wall).
- Cotton Batts (aka “Blue Jeans”) .
- Loose-Fill Fiberglass.
- Polyisocyanurate SIPs.
- Foiled bubble-wrap (Reflectix)
- Open-Cell Polyurethane Spray Foam.
- Closed-Cell Polyurethane Spray Foam. Most expensive
Whoa! So many choices! And the cost varies dramatically, from $.30 per square foot for fiberglass batt to $3.00 psf for closed-cell Poly foam. I think we can rule out the latter, especially since professional installation is recommended. And cost isn’t the only consideration. Of course there is the R-factor to consider, with the higher number offering greater insulation values but also greater thickness (not much of an option for Sparta’s 2 inch wall baffles). The other key issue is how well the insulation breathes. If water gets in or condensation forms, some types of insulation are too impermeable and moisture has nowhere to go – creating the potential for accumulation and mold growth. Hmmm, more research required. In the meantime, here are a few electrical shots: