After Weatherization

Posted on June 19, 2014
Posted By: Rick Barnett
 

The largest part of residential energy consumption (generally considered around 40%) maintains interior comfort regardless of the weather. Energy used to create this comfort is a function of how well inside is separated from outside. The separation zone, or "thermal shell", is the insulating layer around conditioned interior space.

Programs to conserve energy began in the 1970's with public assistance programs "weatherizing" accessible walls and ceilings of leaky older homes. This approach to thermal shell improvement became part of community, government and utility efficiency programs across the country.

The 1980 USDOE report, "Low Energy Futures for the United States" (DOE/PE-0020), didn't mention weatherization in a glimpse of future buildings. Rather, the report states: "improved design and construction incorporating passive solar, superinsulation, and double envelope construction can greatly reduce energy requirements" (page 25).

The lofty goals of "superinsulation and double envelope construction" are still being researched. In practice, the conventional thermal shell is still created by placing fiberglass insulation into walls and the ceiling, leaving an unconditioned attic just inches above the living space. Contractors since the 1970's have used this technique for weatherizing most framed buildings.

BPA's "Conservation Program Options (1983)" described the agency's "Regionwide Residential Weatherization Program", including fiberglass wall insulation as a new element.

Weatherization was still the model for the 1998 "Energy Savers" pamphlet, a joint effort of Owens Corning, Honeywell, and USDOE (DOE/GO-10098-584). The "Insulation and Weatherization" section (p.4-9) outlined sources of air leakage, and how to install fiberglass insulation.

Weatherization became further integrated into US efficiency programs through significant ARRA funding, guided by "Recovery through Retrofit", an October, 2009 report from the President's Council on Environmental Quality". The report's Executive Summary states that efficiency funding would encourage "nationwide weatherization of homes" (page 1). To this day, US efficiency programs generally include weatherization.

In contrast to unchanged weatherization techniques, today's efficiency programs also include leading edge technology with efficient HVAC, controls/thermostats, intelligent efficiency and smarter buildings. Thermal shell improvements appear as an anomaly in an industry filled with technology and data.

A step toward better thermal shells was recently announced by DuPont, with a new "house wrap" that provides a continuous insulating layer to the home. Called "Tyvek ThermaWrap R5.0", DuPont casts this as "Weatherization and Insulation in One". The continuity over the framing is an improvement over fiberglass, which only limits heat loss between the framing materials. While an insulating house wrap can buffer heat loss from walls, it does not affect heat loss through the ceiling.

Fortunately, a more effective "next step" for the thermal shell has been demonstrated with "rigid wrap" retrofits. This technique thoroughly seals the structural shell, including the roof, with commercially available rigid insulation reaching above R-40. A quality job merges the thermal shell and structural shell, offering unmatched performance by eliminating thermal defects.

USDOE's efficiency research includes rigid wrap technology. "Exterior Rigid Insulation Best Practices" is a valuable technical resource. And information about the leading edge of high performance construction is at http://energy.gov/eere/buildings/building-america-research-teams.

Wasted energy for residential space conditioning can be eliminated if, instead of looking at the thermal shell as a place to consider some improvement, the goal becomes doing the best possible job in one step.

This "best job" is described in my recent article, "Thermal Optimization". By optimizing, comfort is maintained with the least amount of energy. If utilities expanded their demand-side programs to include thermal optimization, the custom rigid wrap business would quickly develop production-style techniques and drive cost down.

Although contractors are aware of rigid wrap, homeowners rarely include this when allocating project dollars. Even with efficiency incentives, thermal shell improvement is a minor, code-driven part of an owner-financed retrofit.

Thermal Optimization can change this with affordable utility financing, connected to a long term agreement to supply the home's meter with electricity. By financing quality thermal retrofits, a utility can secure customers while providing better service.

Weatherization has helped many. But it's time to leave this well-used technique behind, and effectively prepare our homes for the 21st century with Thermal Optimization.
 

 
 
Authored By:
Rick Barnett has a B.A. in psychology (UCSB) and an Interdisciplinary Master’s in Environmental Management (Oregon State University, 1981).  Before becoming a builder, Rick introduced the Oregon waste hauler industry to recycling in 1976, and over the next few years convinced many to offer recycling as a service.  Oregon has been a national leader in recycling ever since.Rick started Green Builder in 1996, and was recognized in 1998 by Sustainable
 

Other Posts by: Rick Barnett

Efficiency Gap - March 07, 2016
Energy Asset - January 21, 2016
After Weatherization - September 25, 2015
Energy Customers - April 08, 2015
 
 

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