Page 32 - Green Builder Remodeling Field Report 2021

REVISION HOUSE SCOTTSDALE PROJECT

TEN STEPS TO A

R-37 WALL

10 Every wall is a system. To achieve R-37 performance on
9 the newer, 6-inch walls required a careful layering of dif-
ferent insulations and materials, including, (from outside
to inside):
1. Sherwin-Williams Emerald Rain Refresh exterior paint
8
2. Two coats of stucco
3. LathNet rainscreen stucco lath by Mortar Net
4. DuPont DrainWrap and flashing weatherization system
5. DuPont Thermax (ci) 1.55” R-10 Fastened with TruFast
self-sealing fasteners
6. ½-inch OSB
7. 2 inches of DuPont Froth-Pak, Low GWP closed cell
spray foam, R-12.2
1 8. 3.5 inches of blown fiberglass, R-15.75.
2 3 9. ½-inch Gypsum wallboard
4 5 10. Sherwin Williams SuperPaint with air purifying
6 7
technology

framed portion of the Scottsdale house walls to R-17. should provide optimal performance even on the hottest days.
Steel beams, on the other hand, have no insulating value, The flat roof area consists of several layers, including an
and transfer heat very efficiently. That’s bad news for energy OSB roof deck, sealed with Barrett Black Pearl waterproof-
efficiency. To halt that unwanted heated transfer, we put ing. Over this water proofing is a 4-inch layer of DuPont
three inches of Thermax in between the upper and lower R-20 XPS Styrofoam, plus another 3 inches of closed cell
flanges on the outside of the steel beam (shown). This pro- spray foam; for a total of R-39 above the roof deck. Spray
vided an R-18 insulating value which, combined with the addi- foam over flat roofs is very popular here because you simply
tional R-10 exterior insulation (over the exterior sheathing), shape the foam to provide slope to the drainage scuppers.
gave this part of the wall a total of R-28 for the majority of Finally, spray-on light-colored roofing membrane covers the
the steel beam areas. whole flat roof assembly, reflecting 93% of the sun’s radiant
In parts of the home, where old 2x4 walls could be fully energy. The underside of this roof will be insulated with an
replaced with 2x6-inch framing, we still applied rigid foam on additional R-15 to R-20.
the outside. That meant that wall cavities could be insulated to All of this insulation may seem a bit extreme, but the goal is
R-27.75. Add the R-10 Exterior insulation, and you have a well- to get as close to Zero Net energy as possible. The local util-
insulated wall with R-37.75 performance. ity has set limits on the amount of solar they will allow to be
installed on homes. We need to reduce electric demand as
EXTERIOR ROOF INSULATION much as possible, so many other efficiency aspects link back
The ReVISION house roof includes both hip and flat-style to the building shell: the size of the HVAC equipment, heat
elevations. Perhaps even more than walls, these roofs need to pump water heating, LED lighting, Energy Star appliances and
be armored against Arizona’s scorching heat. The good news pool pumps.
is that almost any amount of exterior foam has been shown My utility has demand charges and higher rates for using
to have big impact on heat resistance. Experiments from the electricity during peak load times from three to eight p.m. So
California Energy commission, for example, revealed that just all the home systems have been carefully designed, allowing it
one inch of foam board installed above the roof deck over a to “coast” through those peak times, when the solar system
VENTED attic reduces attic temperatures from 130 to ambient doesn’t produce power.
outdoor temperatures. The bottom line: By making the Scottsdale ReVISION House
The Scottsdale house, in contrast, includes unvented, but as energy efficient as possible, starting with the outer walls
heavily insulated attics. The bottom side of hip roof areas has and roof, we’ll be able to keep down both the up-front costs
R-48 of insulation, and another one inch of Thermax R-6 poly- and operational costs required to cool it with expensive solar
Iso insulation is installed over the top of the roof deck. This and high-priced peak energy costs. GB

32 GREEN BUILDER REMODELING FIELD REPORT