How To Install Styrofoam Insulation

Rigid Foam Insulation for Existing Outside Walls

Scope

In this retrofit wall assembly, the air control layer is applied straight over the existing wall capsule so covered by at least ii layers of insulating sheathing held in place by vertical furring strips. The vertical furring strips too provide the means of attachment for the outside siding.

There are two possible locations for the water control layer for this retrofit wall assembly – at the outer face of the insulating sheathing or betwixt the insulating capsule and the existing exterior wall.

Insulate the walls of an existing home by removing the existing cladding and installing rigid foam insulating sheathing to upgrade the major building enclosure functions of the wall – h2o control, air control, vapor control, and thermal control, as follows:

• Remove existing wall cladding and trim.
• Prepare the wall sheathing for air/water control membrane.
• Remove windows and doors every bit needed to let flashing of openings and air control transitions into openings.
• Install a continuous air/water control layer to the original sheathing or to the insulation sheathing.
• Transition the wall air/water command membrane to adjacent assemblies.
• Install flashings and air control transitions.
• Re-install windows and doors or install new windows and doors in properly flashed openings.
• Install insulating sheathing in accordance with code to satisfy the high R-value functioning target for the assembly and for adequate condensation command.
• Install furring strips over insulating sheathing and attach to structure (structural sheathing and/or framing) through insulating sheathing. Install furring strips in a vertical orientation only.
• Install wall cladding and trim, by attaching to the furring strips.

Run into the Compliance Tab for related codes and standards requirements, and criteria to come across national programs such as DOE'south Null Energy Ready Dwelling program, Free energy STAR Certified Homes, and EPA Indoor airPLUS.

Clarification

One method for increasing the insulation level of the walls in existing homes is to remove the outside cladding and install rigid foam insulation, possibly new house wrap, and new exterior cladding over the walls. This stride not only increases the wall R-value, information technology can too greatly improve the functioning of the walls to control the movement of air, vapor, and water through the walls.

Some advantages to this retrofit approach include minimizing the impact of the wall retrofit on the interior finishes of the existing business firm, supporting continuity of the water and air command layers, reducing thermal bridging or heat transfer through wall framing, and lowering the gamble of water damage and condensation within the existing wall structure.

In Figures 1 and 2, the wall siding is represented as lap siding, which could be wood, vinyl, or fiber cement lap siding. Other types of siding that can exist attached using the vertical furring strips may be used as well, provided the weight of the siding is less than 10 lb/sf.

Taped insulating capsule may serve every bit a layer to control water, air, and oestrus loss.  However, house wrap or a paint-on membrane could as well be applied to the original capsule before the insulating sheathing is installed.

The insulating sheathing is held in identify by vertical furring strips, along with other attachments per manufacturer's instructions. The vertical furring strips also provide the means of attachment for the exterior siding and provide a ventilation gap under the siding.

The business firm wrap should be overlapped and taped at all seams and fastened with fasteners per the manufacturer's instructions. (See Effigy two.) If more than one layer of foam is used, the exterior layer of the foam is the water control layer and all seams in that layer should exist taped with appropriate foam-uniform tape. The outside foam layer should be foil-faced polyisocyanurate or XPS and the layer should be at least 1 inch thick. EPS should not exist used every bit the outer layer simply EPS Type II could be used as the inner layer. If the exterior of the rigid foam serves as the h2o control layer, the air control layer would yet exist house wrap or paint-on membrane that is installed betwixt the existing firm sheathing and the rigid foam.

The location of the water control layer has implications for how the h2o control part is handled at transitions and interruptions. For example, in window installations, if the water control layer is over the existing sheathing, the windows are installed inside the existing wall framing. If the water command layer is at the face of the insulating capsule, the windows are installed within the insulating capsule layer of the wall, in order to integrate the window flashing into the h2o control layer.

When installing this retrofit wall assembly, it is recommended that multiple layers of insulating sheathing be applied to the exterior of the existing wall. For instance, rather than installing one two-inch layer of rigid foam, 2 i-inch layers are installed. This creates a vapor impermeable layer on the exterior of the existing wall. If there is a wetting event (due east.yard., a plumbing leak) that causes the existing wall structure to go wet, it is important that the wall is able to dry out to the inside. To permit drying to the within, any new or existing application of closed-cell spray cream in the wall cavities should exist limited to a thickness of no more than 1 inch. For other types of spray cream insulation, the vapor permeance of the installed thickness must be at least 1.0 perm. Open up-cell spray foam insulation meets this criteria for typical framed wall crenel depths. This may non be the example for some medium-density spray foams.

It is appropriate to avoid use of an interior vapor bulwark and vapor impermeable wall coverings such every bit non-latex paint and vinyl wallpapers with this retrofit wall approach because these limit the drying potential to the interior. These types of wall coverings may contribute to problems if the interior infinite has loftier humidity, at that place is a history of water leakage in the wall, or the exterior wall has gotten wet during construction.

Figure 1. Insulating sheathing is installed on exterior of an existing framed wall with water control between existing sheathing and insulating sheathing. (Source: Mass Save Dep Energy Retrofit Guide.)

Figure 2. Insulating capsule is installed over existing wall sheathing in a wall retrofit to meliorate insulation, air, and water control. The h2o control layer is at confront of insulating sheathing, which is foil faced and has taped seams. (Source: Mass Save Dep Energy Retrofit Guide.)

How to Install Rigid Foam Board Insulation at Exterior Wall

1. Remove the existing wall cladding and trim, and audit the structural integrity of the wall. Check the wall framing for whatsoever deficiencies, rot, insect damage, etc.  Based on the findings of the inspection, revise the wall assembly plans and review specific detailing equally needed. Go on just afterward needed repairs are performed. Encounter or exceed the minimum requirements of the electric current adopted edifice and energy codes.
2. Prepare the wall capsule to receive the air/water control membrane or house wrap, if one is going to be used. Appropriate preparation of the wall sheathing volition depend upon the nature of the existing sheathing and the air command strategy pursued. If using a canvass good (house wrap) as the air/water control layer, all protruding fasteners must be removed to avoid punctures or tears in the membrane. Gaps or voids in the sheathing layer may demand to be filled in. Use a primer for self-adhered membranes if recommended past the membrane manufacturer if installing membrane.
3. Remove windows and doors and trim to allow for proper flashing of the window and door openings, and to permit the installation of air control transition membranes.
4. Install a continuous air control membrane (house wrap or pigment-on membrane) over the existing capsule as shown in Figure 1. Connect the air control membrane to the air command layer of next assemblies in a tight and durable style. Seal all penetrations against air and water leaks. This layer may besides serve as the water control layer, or the surface of the rigid cream tin can serve as the water command layer if all seams are sealed, as shown in Effigy 2.
5. Install flashings and air control transitions. Transition the air control at the meridian and bottom margins of the exterior wall into the window and door rough openings and air seal all penetrations through the wall. Flash window and door rough openings as well as all wall penetrations.
6. Re-install windows and doors or install new windows and doors in properly flashed openings. If the water control layer is over the existing sheathing, the windows are installed within the existing wall framing whereas if the h2o control layer is at the face of the insulating sheathing, the windows are installed within the insulating sheathing layer of the wall. This is to ensure the window flashing is properly integrated into the h2o command layer. Air seal the window and door units to the air command transition membranes at the interior perimeter of the window and door units.
7. Install insulating sheathing over the air/water command membrane. Butt joints tight. When installing multiple layers, offset seams in two directions. If the surface of the rigid cream will serve every bit the h2o control layer, then the exterior layer of rigid cream cannot be EPS, it must be foil-faced polyisocyanurate or XPS and all seams of the exterior foam layer must be taped. Until furring strips are installed, insulating sheathing pieces can be held in identify with cap nails or screws with roofing washers.
8. Install furring strips over insulating sheathing and attach furring strips to the wall structure (structural sheathing and/or framing) through the insulating sheathing. Install furring strips in a vertical orientation but. It is of import to install furring strips in a vertical, not horizontal, orientation to allow drainage behind the cladding/trim and to prevent h2o from dwelling within the organization. 1x4 furring is recommended. The furring demand not exist preservative treated for moisture protection. The spacing of fasteners through the furring strips must be such that the cladding load is distributed to no more than 10 lb per fastener.
9. Attach cladding and trim to the vertical furring strips.

Ensuring Success

Refer to the current adopted building and energy codes for information on advisable levels of insulation for the different climate zones too equally the proper ratios of vapor and air impermeable and permeable insulation.

Remediate whatsoever hazardous weather condition that volition be afflicted (e.g., exposed or aggravated) past the planned piece of work. Follow applicable laws and industry procedures for mitigation of hazardous materials. Engage the services of a qualified professional person when needed.

Given the increased airtightness associated with this retrofit, combustion prophylactic testing and controlled mechanical ventilation upgrades are required to maintain acceptable indoor air quality.

Climate

The outside wall assembly should be designed for the specific hygrothermal region, rain exposure zone, and interior climate where the home is located.

The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) 2009, 12, 15, and 18. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC 2022. Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide.

Effigy 2. Climate Zone Map from IECC 2009, 12, 15, and 18. (Source: 2012 IECC)

Figure 2. Climate Zone Map from IECC 2022. (Source: 2021 IECC)

Cold Climates

The insulation levels should be based on the minimum requirements for vapor control in the electric current adopted edifice lawmaking and the minimum requirements for thermal control in the current energy lawmaking. Boosted insulation tin can be added higher up these minimums to create loftier R-Value exterior wall assemblies. The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, every bit listed in the 2009, 2022, 2022, 2022, and 2022 IECC and IRC, can be found in this tabular array.

High Current of air Zones

If your home is located in one of the designated loftier-air current zones shown in Figure 3 and Figure 4, ensure that siding is wind resistant to minimize the risk of damage to the rigid cream sheathing layer.

Figure 3. Ultimate Design Wind Speeds. (FEMA 2022).

Figure 4. Current of air Zones in the U.S. (FEMA 2022).

Rigid cream should not exist used as the sole capsule material in gable end walls in high-wind areas; information technology should exist supported by plywood or OSB. In the house shown in Figure 5, the vinyl siding at the gable end wall was installed over plastic foam insulation with no plywood or OSB forest sheathing behind it. The foam insulation and vinyl siding lone were not able to withstand wind pressures which caused the wall to fail assuasive wind-driven pelting to freely enter the attic and saturate the ceiling insulation, causing collapse of the ceiling.

Figure five. The vinyl siding at this gable end wall was installed over plastic foam insulation with no structural capsule backside it. (FEMA 757 2009).

Wildfire Decumbent Areas

With limited exceptions, International Edifice Code Section 2603.v.v, Vertical and lateral burn propagation, requires wall assemblies in Blazon I, Ii, III and IV construction using foam plastic insulation to pass the National Fire Protection Association (NFPA) 285 testing requirements. Despite stating "non-load bearing" in its title and scope, NFPA 285 applies to both non-load bearing and load-bearing walls. In that location are many polyiso, EPS, and XPS rigid foam products that have passed the NFPA 285 wall associates test for fire resistance; some fireproofing installation details may be required. Consult the manufacturers' instructions (Walls & Ceilings 2022).

Run into the Solution Center guide "Current of air and Disaster Resistant Siding" for more information.

The Compliance tab contains both programme and lawmaking information. Code language is excerpted and summarized below. For exact code linguistic communication, 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 discover broken links.

ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

Energy STAR Certified Homes requires that ceiling, wall, flooring, and slab insulation levels meet or exceed those specified in the 2009 International Energy Conservation Code (IECC) with some alternatives and exceptions, and achieve Class 1 installation per RESNET Standards (see 2009 and 2022 IECC Lawmaking Level Insulation – ENERGY STAR Requirements and Insulation Installation (RESNET Class ane). If the state or local residential edifice energy code requires higher insulation levels than those specified in the 2009 IECC, you must meet or exceed the locally mandated requirements. Some states have adopted the 2022 or 2022 IECC. Visit the U.South. DOE Edifice Energy Codes Program to see what code has been adopted in each state.

Rater Design Review Checklist

3. High-Functioning Insulation.
3.1 Specified ceiling, wall, floor, and slab insulation levels comply with one of the following options:
3.1.1 Meets or exceeds 2009 IECC levels^{iv, v, 6}OR;
3.1.two Achieves ≤ 133% of the total UA resulting from the U-factors in 2009 IECC Table 402.1.3, per guidance in Footnote 4d, AND specified abode infiltration does not exceed the following:^{5, 6}

• 3 ACH50 in CZs 1, 2
• 2.five ACH50 in CZs 3, 4
• 2 ACH50 in CZs 5, vi, 7
• 1.five ACH50 in CZ eight

Rater Field Checklist

Thermal Enclosure System
1. Loftier-Functioning Fenestration & Insulation.
1.iii All insulation achieves Grade I install. per ANSI / RESNET / ICC Std. 301. Alternatives in Footnote 4.^{four, 5}

Footnote 4) 2 alternatives are provided: a) Class II cavity insulation is permitted to exist used for assemblies that comprise a layer of continuous, air impermeable insulation ≥ R-three in Climate Zones 1 to 4, ≥ R-5 in Climate Zones five to 8; b) Grade II batts are permitted to exist used in floors if they fill up the full depth of the floor crenel, even when pinch occurs due to excess insulation, as long equally the R-value of the batts has been appropriately assessed based on manufacturer guidance and the but defect preventing the insulation from achieving Form I is the pinch caused by the excess insulation.

Foontote 5) Ensure compliance with this requirement using the version of ANSI / RESNET / ICC Std. 301 utilized by RESNET for HERS ratings.

2. Fully-Aligned Air Barriers.^half-dozen At each insulated location below, a complete air barrier is provided that is fully aligned every bit follows:
Ceilings: At interior or exterior horizontal surface of ceiling insulation in Climate Zones 1-three; at interior horizontal surface of ceiling insulation in Climate Zones four-eight. Too, at exterior vertical surface of ceiling insulation in all climate zones (e.yard., using a air current baffle that extends to the total height of the insulation in every bay or a tabbed baffle in each bay with a soffit vent that prevents wind washing in adjacent bays).⁷
Walls: At exterior vertical surface of wall insulation in all climate zones; too at interior vertical surface of wall insulation in Climate Zones 4-8.⁸
Floors: At exterior vertical surface of floor insulation in all climate zones and, if over unconditioned space, also at interior horizontal surface including supports to ensure alignment. Alternatives in Footnotes xi & 12.^{10, 11, 12}
two.7 All other floors adjoining unconditioned space (eastward.g., rim / band joists at outside wall or at porch roof)

3. Reduced Thermal Bridging.
3.four At above-grade walls separating conditioned from unconditioned space, 1 of the following options used (rim / band joists exempted):¹⁶
three.4.1 Continuous rigid insulation, insulated siding, or combination of the 2 is: ≥ R-three in CZ 1-4; ≥ R-5 in CZ five-8 OR;^{17, 18, nineteen}
3.4.2 Structural Insulated Panels OR; Insulated Concrete Forms OR; Double-wall framing OR;^17,20
iii.4.3 Advanced framing, including all of the Items beneath:²¹
3.iv.3a Corners insulated ≥ R-6 to edge²², AND;
iii.4.3b Headers above windows & doors insulated ≥ R-3 for 2x4 framing or equivalent cavity width, and ≥ R-5 for all other assemblies (e.1000., with 2x6 framing)²³, AND;
3.4.3c Framing limited at all windows & doors to one pair of king studs, plus i pair of jack studs per window opening to back up the header and sill, AND;
iii.iv.3d Interior / exterior wall intersections insulated to aforementioned R-value every bit residual of exterior wall,²⁴AND;
3.4.3e Minimum stud spacing of xvi in. o.c. for 2x4 framing in all Climate Zones and, in CZ 6-eight, 24 in. o.c. for 2x6 framing.²⁵

iv. Air Sealing (Unless otherwise noted beneath, "sealed" indicates the utilise of caulk, foam, or equivalent cloth).
4.one Ducts, flues, shafts, plumbing, piping, wiring, frazzle fans, & other penetrations to unconditioned space sealed, with blocking / flashing every bit needed.

Footnote six) For purposes of this Checklist, an air bulwark is defined as whatsoever durable solid material that blocks air flow betwixt conditioned infinite and unconditioned space, including necessary sealing to block excessive air menstruum at edges and seams and adequate support to resist positive and negative pressures without deportation or damage. EPA recommends, just does non require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness ≥ 5.5 in. or 1.5 in., respectively, to qualify as an air barrier unless the manufacturer indicates otherwise. If flexible air barriers such as business firm wrap are used, they shall be fully sealed at all seams and edges and supported using fasteners with caps or heads ≥ 1 in. diameter unless otherwise indicated by the manufacturer. Flexible air barriers shall not be made of kraft newspaper, paper-based products, or other materials that are easily torn. If polyethylene is used, its thickness shall be ≥ 6 mil.

Footnote viii) All insulated vertical surfaces are considered walls (e.g., above and below class exterior walls, knee walls) and must encounter the air barrier requirements for walls. The following exceptions apply: air barriers recommended, but non required, in adiabatic walls in multifamily dwellings; and, in Climate Zones four through 8, an air barrier at the interior vertical surface of insulation is recommended merely not required in basement walls or crawlspace walls. For the purpose of these exceptions, a basement or crawlspace is a space for which ≥ xl% of the total gross wall expanse is below-class.

Water Management Organisation Architect Requirements

ii Water-Managed Wall Assembly.
two.ane Flashing at lesser of exterior walls with weep holes included for masonry veneer and cry screed for stucco cladding systems, or equivalent drainage system.^nine
two.ii Fully sealed continuous drainage plane behind outside cladding that laps over flashing in Item two.ane and fully sealed at all penetrations. Additional bail-break drainage plane layer provided behind all stucco and not-structural masonry cladding wall assemblies.^{9, 10}
2.3 Window and door openings fully flashed.¹¹

Footnote nine) These Items not required for existing structural masonry walls (east.k., in a home undergoing a gut rehabilitation). Notation this exemption does not extend to existing wall assemblies with masonry veneers.

Footnote 10) Any of the post-obit systems may exist used: a monolithic weather-resistant barrier (i.due east., house wrap) shingled at horizontal joints and sealed or taped at all joints; weather resistant sheathings (e.chiliad., faced rigid insulation) fully taped at all butt joints; lapped shingle-way building paper or felts; or other water-resistive barrier recognized by ICC-ES or other accredited agency.

Footnote 11) Apply pan flashing over the rough sill framing, inclusive of the corners of the sill framing; side flashing that extends over pan flashing; and meridian flashing that extends over side flashing or equivalent details for structural masonry walls or structural concrete walls.

Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in in your country.

DOE Nothing Energy Ready Home (Revision 07)

The DOE Aught Energy Ready Dwelling house Program is a voluntary high-performance home labeling program for new homes operated by the U.S. Department of Energy. Builders and remodelers who are conducting retrofits are welcome to seek certification for existing homes through this voluntary plan.

Exhibit 1 Mandatory Requirements.
Showroom i, Detail ane) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
Exhibit 2, Particular 2) Ceiling, wall, flooring, and slab insulation shall encounter or exceed 2022 IECC levels and attain Grade 1 installation, per RESNET standards.

2009-2021 IECC and IRC Insulation Requirements Table

The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the 2009, 2022, 2022, 2018, and 2022 IECC and IRC, can be institute in this table.

2009, 2022, 2022, 2022,  and 2022 International Energy Conservation Code (IECC)

Department R401.three Certificate
Department R402.1.2 (402.ane.one in 2022 and 2009 IECC) Insulation and fenestration criteria and requirements by component
Tabular array R402.1.2 (402.ane.four in 2009 and 2022 and 402.i.iii in 2009 and 2022 IECC) Equivalent U-factors
Section R402.4 Air leakage (Mandatory)
Table R402.4.ane.i (402.iv.two in 2009 IECC) Air barrier and insulation installation

Retrofit:  2009, 2022, 2022, 2022,  and 2022 IECC

Section R101.four.3 (in 2009 and 2022). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing edifice to comply with this code. (Run across code for additional requirements and exceptions.)

Chapter 5 (in 2022, 2022, 2022). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.

2012 and 2009 International Residential Code (IRC)

Section R302.1 Outside walls
Table R302.ane Outside walls
Department R302.10 Flame spread index and smoke adult index for insulation
Section R316 Foam plastic
Section R403.3.4 Termite damage
Section R703 Exterior covering.
Section R703.11.2 Foam plastic sheathing
Section N1101.12.i (N1101.4 in 2009 IECC) Building thermal envelope insulation
Section N1101.12.4 (N1101.6 in 2009 IECC) Insulation product rating
Department N1101.16 (N1101.ix in 2009 IECC) Certificate (Mandatory)
Department and Table N1102.1.one (N1102.one in 2009 IECC) Insulation and fenestration criteria and requirements by component
Table N1102.1.one Insulation and fenestration requirements by component
Table N1102.1.three (N1102.1.2 in 2009 IECC) Equivalent U-factors
Section N1102.4 Air leakage (Mandatory)
Table N1102.iv.1.1 (N1102.4.2 in 2009 IECC) Air barrier and insulation installation/inspection

2015, 2018, and 2021 IRC

Section R302.1 Exterior walls
Table R302.one Exterior walls
Section R302.x Flame spread index and smoke developed alphabetize for insulation
Section R316 Cream plastic
Section R403.three.four Termite protection
Section R703 Exterior covering.
Department R703.xi.ii Cream plastic sheathing (Insulation over foam plastic sheathing in 2022 and 2022 IRC)
Section N1101.10.ane (R303.1.i) Edifice thermal envelope insulation
Section N1101.10.4 (R303.one.4) Insulation product rating
Section N1101.14 (R401.3) Certificate (Mandatory)
Section N1102.1.2 (R402.1.1) Insulation and fenestration criteria
Table N1102.1.ii (R402.one.1) Insulation and fenestration requirements by component
Tabular array N1102.one.4 (R402.1.4) Equivalent U-factors (R-value computation in 2022 and 2022 IRC)
Department N1102.4 (R402.4) Air leakage (Mandatory)
Table N1102.iv.ane.1 (R402.iv.ane.ane) Air barrier and insulation installation

Retrofit:  2009, 2022, 2022, 2022,  and 2022 IRC

Section R102.seven.ane Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this lawmaking, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their connected safe use.

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

References and Resources*

*For not-dated media, such as websites, the appointment listed is the appointment accessed.

Contributors to this Guide

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

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Source: https://basc.pnnl.gov/resource-guides/rigid-foam-insulation-existing-exterior-walls

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