Double stud wall, Maine

There are many ways to get to a well-insulated, tight wall system. One popular option is double-stud wall framing, where you have a (typically) 2×4 structural wall and then an inner 2×4 wall, separated by an airspace, which gives you lots of room to insulate.
Other options include an insulated 2×6 framing wall with rigid foam (to stop thermal bridging), or advanced materials like Structural Insulated Panels (SIPs).

The most important advice we have doesn’t even pertain to solar… it’s about the house itself. Build it better!

While building codes have gotten tougher around energy efficiency, we still think that a code-built home is far below the minimum insulation/air-tightness that any reasonable person would want. It really doesn’t cost that much more money to build a tighter, better-insulated home, and the effort to do so will result in huge savings down the road, in terms of energy bills you don’t need to pay and carbon pollution you’ll keep out of the atmosphere.

There are lots of nuances to this, but we’re generally fans of building at least to a “Pretty Good House” standard:

  • Well-insulated (R20+) basement or slab
  • R30-40+ wall system, such as 2×6 walls with dense pack cellulose for thermal resistance and 2 inch of rigid foam to eliminate thermal bridging (even better to do a double-stud wall system!)
  • R60+ attic insulation
  • Better than average air sealing (easier said than done, as many trades on a jobsite need to have air sealing literacy for this to be successful. For example, choices in the framing process matter in terms of air sealing, and electricians/plumbers can screw up a really good air sealing job!)
  • High-end double-hung windows, or triple-glazed windows
  • Mechanical ventilation (without this it’ll be hard to breathe in your tight new house!)

For context, a home built to this standard may command a 30% cost premium over a barely-meets-code build home, but will use roughly ½ as much energy.

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