- First, consider a new building built to current building codes. That hypothetical building we'll call code-built construction. The heat load for such a structure is, by definition, 100% of the thermal load for a building of the same design and floor plan.
- Next, consider a building that is uses 20% less energy, or 80% of the energy consumed by the code-built home. In this climate, that 20% threshold is required for Energy Star designation. Thus, we'll define Energy Star Construction as a building that uses 80% of the fuel required by a Code-Built building.
- Near-ZEB Construction is a building that uses 70% less than the code-built home, so it requires only 30% of the energy of the typical code-built home.
- ZERO Energy Buildings, or ZEB's, make all of the energy required for the building load. Without Near-ZEB engineering, planing, and design, getting to ZERO will be very difficult, or very expensive.
Q: But isn't Near-ZEB performance expensive?
A: NO! Not for new construction.
What does Near-ZEB construction look like? Usually, near-ZEB performance means thicker walls and higher performing windows and doors with lower U-values (higher R-value). It also means careful attention to all the little details of air movement, and air barrier integrity to achieve low infiltration values. How thick the walls need to be depends on the type of insulation being used, and the design heat load of the building.
"5-10-20-40-80" (note that each number is twice the preceding number).
- 5 = 0.05 air changes per hour at 50 Pascals (VERY tight)
- 10 = R-10 Windows & Doors. (That's a U-value of 0.10, so pretty high performance!)
- 20 = R-20 on all below grade surfaces, including basement floors
- 40 = R-40 above grade (pretty high -- 2 x 6 and R-19 fiberglass actually performs at roughly R-11)
- 80 = R-80 in the attic & roof.