What is Class 1 insulation?

Providing a Grade I installation is important to delivering a quality, energy-efficient home. A Grade I designation means that the home insulation is properly installed and without any moderate or substantial defects. While Grade I installation should be the norm in the residential building industry, there are instances where it is not. The result of a sub-par installation is a home that doesn't perform to its potential'which unfortunately reflects poorly on builders, installers and insulation manufacturers alike.

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What are the RESNET grading criteria?

The Residential Energy Services Network (RESNET) has outlined standards that define an insulation installation grading system for use by HERS raters in evaluating installation quality. When inspecting insulation, HERS raters are primarily looking for any missing insulation (voids), gaps or compression.

Summary of RESNET Grading Criteria:

Grade I ' Minor Defects

Occasional very small gaps are allowed. Voids can't extend from the interior to the exterior (i.e. the full width of a wall cavity). The product is installed according to manufacturer's specification and cut to fit around electrical junction boxes and is split around wires and pipes. Compression or incomplete fill amounting to 2% or less, if the empty spaces are less than 30% of the intended fill thickness, are acceptable for Grade I.

Grade II ' Moderate Defects

Can have minor compression and up to 2% missing insulation. Can also have moderate to frequent gaps around wiring, electrical outlets, plumbing and other intrusions. It's important to note that the grading system treats and assesses missing insulation differently than compressed insulation.

Grade III ' Substantial Defects

Has substantial gaps and voids with missing insulation comprising more than 2% of total area. Installations not complying with the minimum installation requirements and Grade I or Grade II requirements above are a Grade III installation.

To read the full text from the RESNET Manual, click here and refer to Appendix A, pages A-11 through A-16.

Resources to get you a Grade I Installation

On this website we offer detailed instructions, as well as videos and visual guides, including:

• Preparing for installation. Our page on installation considerations will help you prepare for installation, giving you an overview of what needs to happen before installation can begin.
• Proper installation techniques. These pages are mobile optimized to make them easy to use on a jobsite. In them, we provide location-specific installation images in a simple 'do this, not that' format.
  • Attic insulation and ceiling insulation
  • Wall and knee wall insulation
  • Floor insulation
• Downloadable guides. If you'd prefer PDF guides to print or download, we offer the same installation guidance in our downloadable pictorial guide. We also have a Spanish version of the guide.
• Video series on proper batt installation. On our YouTube channel we have playlists with our three part installation video series, available in both English and Spanish.
• Video clips on proper batt installation. If you don't want the full videos and instead just want shorter clips, this playlist addresses a few specific areas that demand particular attention.
• 25 point checklist for inspecting insulation. This can serve as a useful punch list to make sure the install was done right.

Also, the RESNET Manual specifically states that the following NAIMA publications may be used as references for proper installation:

• Recommendations for Installing Mineral Fiber Insulation in Residential and Other Light-Frame Construction
• Recommendations for Installation in Residential and Other Light-Frame Construction: Fiber Glass Loose Fill Insulation

Ready to Start Installing?

View our Tutorials to Begin Download this page as a PDF

Scope Scope Images Scope

Install insulation without misalignments, compressions, gaps, or voids along the thermal envelope of the house.

All ceiling, wall, floor, and slab insulation should achieve Grade I level insulation installation criteria as defined by the Residential Energy Services Network (RESNET). 

See the Compliance Tab for links to related codes and standards and voluntary federal energy-efficiency program requirements.

Description Description

Gaps, voids, and compressions that cause the insulation to lose contact with the surface it is intended to insulate can cause cold spots in walls, ceilings, and floors. These cold spots may encourage the formation of condensation in the wall cavity, floors, or ceilings. 

The Residential Energy Services Network (RESNET) grades insulation installation quality in its Home Energy Rating System Standards, with Grade 1 being the best installation (RESNET ).

Grade 1 Installation requires that insulation material should uniformly fill wall cavities, filling each cavity from side to side and top to bottom, without substantial gaps or voids around obstructions. Batt insulation should be cut to fit around any wiring or piping installed in the wall cavities.

Blown insulation, such as loose fiberglass, cellulose, or mineral wool fibers, flows easily around obstructions, such as wiring and piping, to provide complete coverage in the cavities. To install blown insulation, the open cavities are first covered with a netting that is stapled to the stud faces. A slit is cut in the netting in each cavity and the insulation is installed with a hose inserted through the slit. The installer can easily see where the insulation is going to ensure that each cavity is completely filled without voids.

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Spray foam is another option that readily fills areas around obstructions in wall cavities, and it has the advantage of providing both air sealing and insulation. The foam completely fills the open wall cavities and is trimmed flush with the stud faces before installing dry wall. Spray foam insulation is made of petroleum, soy, or castor oil-based polyurethane and is available in open-cell, low-density products or closed-cell, high-density products. Both insulate and air seal; high-density products can also provide a vapor barrier. Another option is sprayed-on cellulose or mineral wool that is mixed with adhesive and water then sprayed into the open cavities and allowed to dry before drywalling.

Additional information about insulation, including descriptions of the many types of insulation available, their R-values, applications and advantages and disadvantages of each kind, and installation guidance can be found in the Building America Best Practices Series Volume 17: Insulation, A Guide for Contractors to Share with Homeowners.  

How to Install Insulation to RESNET-Defined Grade I 

1. Install insulation without misalignments, compressions, gaps, or voids in all wall cavities along the thermal barrier of the house. Figure 1 shows proper installation of batt insulation without gaps or voids. Figure 2 shows incorrect installation; the insulation was not cut to fit around wiring so the insulation will not be in full contact with the drywall along the length of the wall cavities.

2. Install wall insulation so that it is enclosed on all six sides in each wall cavity. It should completely fill the wall cavities as shown with the blown fiberglass insulation in Figure 3, the blown cellulose in Figure 4, and the spray foam in Figure 5. It should be in substantial contact with the sheathing material on at least one side (interior or exterior) of the cavity.

3. Faced batt insulation should be stapled to the surface of framing (Figure 6). Side-stapling is permitted, provided the tabs are stapled neatly (no buckling), the batt is only compressed at the edges of each cavity to the depth of the tab itself, and the batt meets the other requirements of Grade I.

4. Install slab edge insulation for slab-on-grade floors if the floor surface is less than 12 inches below grade and if required by code in your climate zone. Slab insulation should extend to the top of the slab to provide a complete thermal break (Figure 7). If the insulation is installed between the exterior wall and the edge of the interior slab, the insulation may be cut at a 45-degree angle away from the exterior wall, allowing the poured slab concrete to cover and protect the top edge of the insulation.
   Insulating the slab edge will keep the floor warmer and reduce the potential for condensation and elevated relative humidity by allowing the inside surface temperature of the slab perimeter to more closely track the home's interior temperature. If the slab is monolithic with a grade beam (Figure 7), the insulation is installed on the exterior of the slab edge/grade beam and continues vertically to the bottom of the grade beam. Use insulation material that is appropriate for ground contact such as XPS, rigid fiberglass, or rigid rock wool and use insect controls appropriate for the region. The above-ground portion of the rigid foam should be protected from UV and impact damage with coated fiber cement board.

   
   
   When the slab is independent from the perimeter foundation wall, insulation may be installed either on the exterior of the foundation wall or between the foundation wall and the slab (Figure 8), which provides more protection for the insulation from the elements. When the insulation is between the foundation wall and the slab, it forms a bond break and it should also extend horizontally under the slab either at the perimeter or under the entire slab.

5. Where an insulated wall separates a garage, patio, porch, or other unconditioned space from the conditioned space of the house, install slab insulation to provide a thermal break between the conditioned and unconditioned slab. Where specific details cannot meet this ENERGY STAR Ver. 3, Rev 11. requirement, provide the detail to EPA to request an exemption prior to the home's qualification. 

Success Ensuring Success

Home energy raters are required to inspect and probe in, around, or through the insulation and/or vapor retarder in several places to see whether insulation is installed to RESNET Grade 1 standards. During inspection, insulation and vapor retarders may be cut or pulled away so raters can see installation details. The raters should replace or repair the vapor retarder and insulation as necessary. During inspection (typically before drywall is installed), if the exterior sheathing is visible from the building interior through gaps in the cavity insulation material, it is not considered a Grade I installation.

Typical R-values for common insulation materials are summarized in this table, which also identifies the vapor retarder classification for each insulation.

Climate Climate

The amounts of insulation that must be installed in various building components are specified by code and vary by climate. The U.S. Department of Energy Building Energy Code Program identifies the building codes currently in force for each state.

For more information on the insulation levels required in the and International Energy Conservation Code (IECC), which are specified by climate zone, see the and IECC Code Level Insulation ' ENERGY STAR Requirements and  IECC Code Level Insulation ' DOE Zero Energy Ready Home Requirements.

The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) , 12, 15, and 18. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC . Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide. 

Training Right and Wrong Images Presentations Author(s) Rashkin Organization(s) DOE Description Presentation describing an overview of Zero Energy REady Home performance, requirements, and building methods. Author(s) Cottrell Organization(s) North American Insulation Manufacturers Association Description One liner: presentation describing criteria for different insulation installation grades. Videos Author(s) Advanced Energy Organization(s) Advanced Energy Description Brian Coble, Director of High Performance Homes for Advanced Energy provides best practices on "Proper Installation of Insulation" as he walks viewers through an ENERGY STAR Home and points out every area of a home that must be insulated to meet RESNET Grade 1 Insulation Installation Requirements... Author(s) Advanced Energy Organization(s) Advanced Energy Description Brian Coble, Director of High Performance Homes for Advanced Energy provides best practices on "Proper Installation of Insulation" as he walks viewers through an ENERGY STAR Home and points out every area of a home that must be insulated to meet RESNET Grade 1 Insulation Installation Requirements... Author(s) Advanced Energy Organization(s) Advanced Energy Description Brian Coble, Director of High Performance Homes for Advanced Energy provides best practices on "Proper Installation of Insulation" as he walks viewers through an ENERGY STAR Home and points out every area of a home that must be insulated to meet RESNET Grade 1 Insulation Installation Requirements... Description Video describing how to properly install the OPTIMA insulation system. Description Video describing how to properly install insulation. Compliance

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

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More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies Author(s) Pacific Northwest National Laboratory Organization(s) PNNL Description Case study describing a new home builder that strives to address health, safety, and durability issues in a hot and humid climate. Author(s) Pacific Northwest National Laboratory Organization(s) PNNL Description Case study describing a builder in Georgia that designs energy-efficient homes for a green community, yielding homes with HERS scores as lowas 59 and electric bills as low as $50 a month. Author(s) Pacific Northwest National Laboratory Organization(s) PNNL Description Case study describing a new construction building project of 20 luxury homes in northern New Jersey that were more energy efficient than ENERGY STAR and met the 50% energy savings requirements of the federal tax credit for new homes. References and Resources* Author(s) U.S. Environmental Protection Agency, ENERGY STAR Organization(s) EPA Description Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist. Author(s) Baechler Michael C, Gilbride Theresa L, Hefty Marye G, Cole Pam C, Williamson Jennifer, Love Pat M Organization(s) Pacific Northwest National Laboratory, PNNL, Oak Ridge National Laboratory, ORNL, U.S. Department of Energy, DOE Description Report providing builders in marine climates with guidance for building homes that have whole-house energy savings of 40% over the Building America benchmark with no added overall costs for consumers. Author(s) Baechler Michael C, Adams Karen T, Hefty Marye G, Gilbride Theresa L, Love Pat M Organization(s) Pacific Northwest National Laboratory, PNNL, Oak Ridge National Laboratory, ORNL, U.S. Department of Energy, DOE Description Document providing descriptions of the many insulation options available to homeowners, along with guidance on where, when, and how to install insulation throughout your house. Author(s) Building Science Corporation Organization(s) BSC Description Information sheet about insulating slabs. Author(s) North America Insulation Manufacturers Association, Insulation Institute Organization(s) NAIMA Description Website providing builders with information about meeting RESNET Grade 1 criteria when installing insulation. Author(s) Cottrell Charles Organization(s) Residential Energy Services Network, RESNET, North American Insulation Manufacturers Association, NAIMA Description Presentation describing RESNET grading criteria for insulation installation. Author(s) RESNET Organization(s) RESNET Description RESNET standards aimed to ensure that accurate and consistent home energy ratings are performed by accredited home energy rating providers through their raters nationwide. Author(s) Bailes Organization(s) Energy Vanguard Description Article describing RESNET's insulation grading levels. *For non-dated media, such as websites, the date listed is the date accessed. Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

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