Staircase Walls

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Climate

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier that is fully aligned with insulation is to be provided at exterior surface of walls in all climate zones and at interior surface of walls for Climate Zones 4-8. All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls, with the exception of adiabatic walls in multifamily dwellings.

DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Infiltration (ACH50):  Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol.

climate zone map

International Energy Conservation Code (IECC) Climate Regions

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Description

Staircases and staircase landings are often located along exterior walls or walls adjoining unconditioned spaces like garages or attics. Insulating and air blocking of the exterior wall below the stairs is sometimes overlooked. When the insulation in the exterior wall cavities is not fully aligned with (touching) the interior wall sheathing (drywall), the insulation’s effectiveness is reduced. After filling the wall cavities with insulation, the walls should be covered with a rigid air barrier material such as rigid foam insulation, OSB, or drywall that is taped at any seams and sealed to the bottom plate, top plate, and framing at the edges with caulk. The insulation should fill the cavity and be fully aligned with the rigid sheathing.

Staircases may be prefabricated or custom site-built. Prefabricated stairs are often used when the stairs will be covered with carpet, although they can be ordered with hardwood and custom finishes. Custom staircases are sometimes built when the stair treads will be hardwood.

Prefabricated stairs come with the stair treads and risers already attached to the stringer boards. The most common varieties are the notched stringer stair and the routed stringer stair. The notched staircase uses three stringers that are cut out or notched to hold the stair step treads and risers. Routed stringer stairs use two stringer boards that are not notched. The routed stringer differs from the notched stair by utilizing two visible skirt boards as its structural support stringers. Each stringer is usually a solid finished piece of wood, typically 12 inches high and 1.25 inches thick, that is routed to hold the treads and risers. The steps are nailed and glued to the stringers. Because these stringer boards extend above and below the sides of the steps, they serve as the finish boards as well.

These materials may be installed by insulators, framers, or drywallers. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site.

Prefabricated notched stringer staircase

Figure 1 - A prefabricated notched stringer staircase comes with the stair step treads and risers already fastened to the three notched stringer boards. Reference

Prefabricated routed stringer staircase

Figure 2 - A prefabricated routed stringer staircase comes with the stair step treads and risers already fastened to the two routed stringer boards, which also serve as the finish boards. Reference

How to Install a Prefabricated Routed Stringer Staircase

  1. If a prefabricated routed stringer staircase is used, insulate the wall, then attach the bottom end of the stringers to the floor and the top end to the second floor or landing. Fasten the staircase through the stringer boards to the exterior wall studs. Install drywall cut at a diagonal to fit from the top of the stringer/finish board to the ceiling. Apply caulk or joint compound to the seam between the top of the finish board and the drywall. Cover the seam with trim.
  2. Below the stairs, apply caulk to the exterior wall framing and to the bottom edge of the stringer board, then install rigid foam, drywall, or another sheet good from the bottom of the stringer/finish board to the bottom plate of the wall. Caulk or tape any seams.

Air sealing behind a staircaseReference

 

 

How to Install a Site-Built or Prefabricated Notched Stringer Staircase on an Exterior Wall

  1. Attach a spacer board to the outer side of the outside notched stringer boards. Attach the spacer board flush with the bottom edge of the stringer board. The spacer board should be thick enough to allow room to slide the drywall between the stringer and the exterior wall studs. If you want to install a finish board along the steps, use a wider spacer (e.g., a 2x4) that will accommodate the thickness of both the drywall and the finish board.
  2. Attach the stringers at the base floor and the second floor or landing. Insulate the wall. Attach the stringer board to the exterior wall studs through the spacer board. The spacer board will give you room to slide the drywall between the riser and the exterior wall studs. 

Caulk the drywall to the spacer board behind the stringer boardReference

  3.  Cut drywall to fit from the top of the spacer board to the ceiling. Apply caulk or joint compound along the top of the spacer (or bottom edge of the drywall). Slide the drywall behind the stringer    board so it is resting on the spacer board and fasten it to the exterior wall studs. Install a finish board next to the drywall if desired.

  4.  Below the stairs, apply caulk to the exterior wall framing and the bottom edge of the spacer board then install rigid foam, drywall, or another sheet good from the bottom of the stringer board to the bottom plate of the wall. Caulk or tape any seams.

Drywall is installed above the spacer board and drywall or another sheet good is installed below the spacer board to provide an air barrier on the exterior wall below the stepsReference

Ensuring Success

The site supervisor should visually inspect the exterior wall underneath staircases or staircase landings located on exterior walls during construction to confirm that the wall cavity is insulated and that a rigid air barrier material is installed on the interior surface of the exterior wall in contact with the cavity insulation. Blower door testing conducted as part of whole-house energy performance testing may help indicate if there are air leaks at staircases. High-performance branding programs and the 2009 and 2012 IECC require that builders meet specified insulation levels and infiltration rates. See the “compliance” tab for these specified infiltration rates.

Scope

Staircase walls

Fully Aligned Air Barriers

  1. Install insulation without misalignments, compressions, gaps, or voids in all exterior wall cavities underneath all staircases.
  2. Install a rigid air barrier to prevent insulation from sagging and create a continuous thermal barrier.
  3. Seal all seams, gaps, and holes of the air barrier with caulk or foam.

ENERGY STAR Notes:

ENERGY STAR highly recommends using a rigid air barrier, but it is not a requirement.

An air barrier is defined as any durable solid material that blocks air flow between conditioned space and unconditioned space, including necessary sealing to block excessive air flow at edges and seams and adequate support to resist positive and negative pressures without displacement or damage. ENERGY STAR recommends, but does not require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness >= 5.5 inches or 1.5 inches, respectively, to qualify as an air barrier unless the manufacturer indicates otherwise. If flexible air barriers such as house wrap are used, they shall be fully sealed at all seams and edges and supported using fasteners with caps or heads >= 1 inch in diameter unless otherwise indicated by the manufacturer. Flexible air barriers shall not be made of kraft paper, paper-based products, or other materials that are easily torn. If polyethylene is used, its thickness shall be >= 6 mil.

ENERGY STAR highly recommends, but does not require, inclusion of an interior air barrier at band joists in Climate Zone 4 through 8.

All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls, with the exception of adiabatic walls in multifamily dwellings. All insulated ceiling surfaces, regardless of slope (e.g., cathedral ceilings, tray ceilings, conditioned attic roof decks, flat ceilings, sloped ceilings), must meet the requirements for ceilings.

Training

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Compliance

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier shall be provided that is fully aligned with the insulation at exterior surface of walls in all climate zones; and also at interior surface of walls for Climate Zones 4-8. All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls, with the exception of adiabatic walls in multifamily dwellings.

      
DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Certified under ENERGY STAR Qualified Homes Version 3. Infiltration (ACH50): Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol.

ASTM E1677-11

Standard Specification for Air Barrier (AB) Material or System for Low-Rise Framed Building Walls. This specification covers minimum performances and specification criteria for an air barrier material or system for framed, opaque walls of low-rise buildings. The provisions are intended to allow the user to design the wall performance criteria and increase air barrier specifications for a particular climate location, function, or design.

2009 IECC

Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.*

2009 IRC

Table N1102.4.2 Air Barrier and Insulation Inspection Component Criteria, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.* 

2012 IECC

Exterior insulation for framed walls is in substantial contact and continuous alignment with the air barrier.* Table R402.4.1.1 Air Barrier and Insulation Installation, Air barrier and thermal barrier: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed. Air permeable insulation is not used as a sealing material.*

2012 IRC

Exterior insulation for framed walls is in substantial contact and continuous alignment with the air barrier.* Table N1102.4.1.1 Air Barrier and Insulation Installation, Air barrier and thermal barrier: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed.  Air permeable insulation is not used as a sealing material.*

*Due to copyright restrictions, exact code text is not provided. For specific code text, refer to the applicable code.

More Info.

Case Studies

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References and Resources*

  1. Author(s): DOE
    Organization(s): DOE
    Publication Date: June 2013

    Standard requirements for DOE's Challenge Home national program certification.

  2. Author(s): EPA
    Organization(s): EPA
    Publication Date: June 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

  3. Author(s): EPA
    Organization(s): EPA
    Publication Date: October 2011

    Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.

Last Updated: 08/15/2013

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