rigid foam sheathing

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Wall Sheathing Options

Choosing between OSB, plywood, fiberboard, rigid foam, diagonal boards, and fiberglass-faced gypsum panels

Posted on Nov 20 2015 by Martin Holladay
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For the past 30 years, the majority of new homes in the U.S. have been built with wood-framed walls sheathed with oriented strand board (OSB). Most builders are so comfortable with OSB wall sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. that they never consider using an alternative material.

In fact, a wide range of materials can be used to sheathe a wood-framed wall. In addition to OSB, builders can choose plywood, fiberboard, rigid foam, diagonal boards, and fiberglass-faced gypsum panels. If you’re a dyed-in-the-wool OSB user, it might be time to consider some of the available alternatives to OSB.


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Image Credits:

  1. Image #1: Lunenburgfirehouse.blogspot.com

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Deep-Energy Retrofits

Posted on Jul 28 2009 by Alex Wilson

Starting in the 1970s, following the first energy crisis, major weatherization programs were launched to tighten up American homes. The Weatherization Assistance Program of the U.S. Department of Energy, which focuses on low-income homes, has weatherized some 6.2 million dwellings, reducing energy consumption by an average of 32%, since its inception in 1976. State and local programs and private weatherization companies have weatherized tens of millions of additional homes.


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An Old House Gets a Superinsulation Retrofit

Arlington, MA

Apr 5 2009 By Rob Wotzak | 22 comments

General Specs and Team

Location: Arlington, MA
Bedrooms: 6
Bathrooms: 3
Living Space : 3000 sqf
Cost (USD/sq. ft.): $33/sqf

Completed: March 2009

Builder/contractor: Synergy Companies Construction, LLC
Energy consultant: Building Science Corporation

Construction

Basement: ceiling insulated with 4" to 8" of low-density spray polyurethane foam (IcyneneOpen-cell, low-density spray foam insulation that can be used in wall, floor, and roof assemblies. It has an R-value of about 3.6 per inch and a vapor permeability of about 10 perms at 5 inches thick.)
Walls: existing cellulose-filled 2x4 studs; 4-in. of foil-faced polyisocyanurate foam outside of sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. (R-39)

Windows: fiberglass frame, double-pane, argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled, low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. (U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. : 0.33, SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1.: 0.29, Pella Impervia)
Roof: rafter bays filled with low-density spray foam (Icynene); 6-in. foil-faced polyisocyanurate foam outside sheathing; seams staggered and taped (R-59 total)

Further resources

Mass. Dept. of Energy Resources (DOER) and NSTAR plan to use information gathered from this insulation retrofit to help Massachusetts residents greatly improve the energy efficiency of their homes.

A detailed journal of the project and a complete list of sponsors can be found at Alex Cheimets' blog: superinsulating.blogspot.com

Energy

Heating/cooling: oil-fired steam boiler in each unit
Water heating: main boiler in unit 1; on-demand gas water heater in unit 2 (200,000 Btu, Rheem)
Annual energy use: To come

  • Currently: 1,200–1,400 gals. heating oil combined
  • Projected: 450 gal. heating oil
    • All lighting converted to CFLs in unit 2
    • Aggressive insulation strategies

    Water Efficiency

    • Low-flow toilets and showerheads

    Indoor Air Quality

    • (2) HRVs (Fantech)
    • CO sensors on every floor
    • Basement ceiling is foamed/sealed to isolate moisture from living areas
    • Interior basement access doors converted to exterior insulated doors with weather seals

    Green Materials and Resource Efficiency

    • Extra materials donated or reused on other projects
    • Retained as much of the original structure as possible

    A vintage home gets a 21st-century energy overhaul

    What started out as a relatively straightforward re-siding project on this 80-year-old duplex in Arlington, Mass., ultimately evolved into part of an ambitious superinsulation pilot program for the Massachusetts Department of Energy Resources (DOER) and the regional utility company, NSTAR.

    Lessons Learned

    Once the ball got rolling, Alex quickly realized that compromises were necessary to keep the project moving— particularly in material choices. If he had had his way, he would have taken more time to evaluate the sustainability and resource efficiency of everything that went into the home.

    Exterior retrofits make sense
    It depends on the conditions of the particular home, but the consensus seems to be that exterior insulation is the smartest way to boost energy efficiency of existing homes. Other than what Alex describes as a "week of hell" during the basement and attic demolition, the interior remained reasonably undisturbed during the entire process. The place was drafty and cold at times, but that's hardly unexpected when tearing into a house in the middle of a New England winter.

    Overachieving doesn't always pay off
    Building Science Corp. had specified 4-in. rigid insulation on the roof, but when Alex found out that 6-in. foam was available, he told Synergy, and they decided to go for it. A box of broken, 10-in. screws, a new set of impact drivers, and a week's worth of frustration later, they wonder if it was worth it. In the end, the roof worked out well, but the extra effort and cost were hard to justify.


    —Rob Wotzak is associate editor at GreenBuildingAdvisor.com

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    Image Credits:

    1. Alex Cheimets

    Energy-Efficient Framing, a.k.a. Advanced Framing

    Use Less Material and Build a Better House

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    Image Credits:

    1. Chuck Lockhart/Fine Homebuilding #174
    2. Rob Yagid/Fine Homebuilding #197
    3. Daniel S. Morrison/Fine Homebuilding #174
    4. Code Check Building 2nd Edition
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