This Is Part-6-B Of Our Multi-Part Article Discusses Insulation Requirements In Newly-Built Exterior Walls.   TIP: For any existing exterior walls (in an existing home) — if they are Altered — New Construction Building Codes Apply.  If existing walls are Not Altered — they are Not required to meet current building codes.   Our Entire Article Details How To Lower Heating (& cooling) Costs.

Al’s Plumbing — in Plano, TX provides Full-Service Plumbing; maintenance, repairs, and replacements for every plumbing component in your home.  Al’s sells and installs gas and electric water heaters.  Al’s is near your home in; Plano, TX; Allen, TX; Frisco, TX; and McKinney, Texas.  We service all homes in southern Collin County, TX, and northeastern Dallas County, TX with no additional travel charges.

Call Al’s Today To Discuss Any Concerns Or Problems You Have With Your Home’s Plumbing. 

We will arrange an appointment at your convenience.

Part-6-B: Insulation Requirements For

Newly-Constructed OR Altered Exterior Walls & Ceilings

Such As Room Additions To Existing Homes.

& Newly-Built Homes In TEXAS.

Click Below To Read Our Article About Adding Insulation To An Existing Home:

AlsPlumbing.com — Adding Insulation To An Existing Home

Image Source: Shutterstock

Shown: Second Floor Being Added To An Existing Home

** TIPS: Building & Mechanicals Permits **

• When Renovating Or Building An Addition To An Existing Home — Check With Your City To Know Which Permit(s) Is Required Before Starting Work.
• Permits trigger inspections by the City — to ensure the work is code-compliant and safe.
• Permits vary by City, and always include Mechanical Permits for; Plumbing, Electrical, and Heating/Cooling equipment.
• If Unpermitted Work was done — the City will likely require the drywall removed so inspections can occur.  Some Cities require unpermitted work to be demolished.
• When Selling The Home — it’s illegal to conceal unpermitted work from the buyer.   The City goes after the current owner if unpermitted work was done.

• A Permit must be issued Before work begins — and all work must be Building-Code-Compliant.
• City Inspections are required during the work.
• If you begin work before a permit is issued — the City will issue a “Stop Work” order — until required permits are issued.
• TIP: A permit is seldom required for Interior Cosmetic Work.
• Interior Cosmetic Work fixes or updates the appearance of the interior of an existing home — without altering the home, or adding or removing square footage.

• A requirement for both remodels (that require a permit) and new construction is a Rescheck Report.
• This report ensures compliance with Local, State, & Federal Energy Codes.
• Rescheck Is Required Throughout Texas.

Source: https://www.austintexas.gov/page/work-exempt-building-permits

Source: https://www.austintexas.gov/permittingatx/projects/interior-remodel/define

Source: https://scotthomeinspection.com/what-texas-cities-require-rescheck-reports-for-building-permit-submission/

Building-Code-Related Insulation Requirements For Altered Exterior Walls

(When Making Changes To Existing Walls In An Existing Home.)

• Existing Building Components that are altered — must comply with New Construction Building Codes.
• Any altered exterior walls must meet current building codes.  Insulation Rrequirements include “R-13+5” —  R-13 (BATT insulation inside the wall) + R-5 Insulated Foam Sheathing.

• TIP: Unaltered portions of an existing building are not required to comply with new construction insulation requirements.

Source: https://basc.pnnl.gov/code-compliance/sealing-and-insulating-existing-exterior-walls-code-compliance-brief

To Skip This Section About Knob & Tube Electrical Wiring — Scroll Down To The Next Triple Lines.

If Your Home Was Built Before 1950-1955 — It had Knob & Tube Electrical Wiring. 

 Electrical Code Prohibits Connecting New Wires To Any Knob & Tube Circuit.

A Licensed Electrician Knows This — A Handyman Likely Wouldn’t.  DIY & Handymen Often Connect New Wires To K&T — Not Knowing Of The Dangers.

Image Source: Shutterstock

When Built — Most Homes Built Before 1950–1955 Had Knob & Tube (K&N) Electrical Wiring.

K&T Wiring Is Rated For (up to) 60-Amp Electrical Demand.

TIP: Many Older Homes Have Updated Electrical Wiring.  An Electrical Inspection Can Determine This.

K&T wiring is insulated with cloth (that was soaked in oil) or rubber around single wires.  In later years, the 2 wires were inside another layer of cloth insulation.  When K&T wiring carries more than 60 Amps AND/OR home insulation was added against it — K&T wiring Gets Too Hot and can easily set the cloth insulation and house on fire.

The Photos Below Show What Knob & Tube Electrical Wiring Looks Like.

Image Source: YouTube Embedded Video Link

A Safety Alert

You Can’t Add Insulation To A Home With Knob & Tube Electrical Wiring (that’s in use).  K&T wiring must be able to dissipate heat.  If you have any type of insulation against it, it will get hotter than it was designed for — and history has shown a pattern of electrical fires after insulation was added to homes with K&T wiring.

TIP: Most homeowners insurance companies won’t insure a home with K&T wiring.

If Your Home Has K&T Wiring — Contact Your Insurance Company To Ensure They Know That.   Otherwise, ff you have an electrical fire, they will likely deny your claim.

To Learn Complete Details About Knob & Tube Electrical Wiring – Click The Link Below For Our Separate Article:

AlsPlumbing.com Does Your Home Have Knob & Tube Electrical Wiring?/does-your-home-have-knob-tube-wiring/

This 2-1/2 Minute Video Describes Knob & Tube Wiring.

Image Source: YouTube Embedded Video Link

 End Of The Section About Knob & Tube Electrical Wiring

Does Your TEXAS Home Has WALL Insulation – Based On Year Built?

Image Source: Shutterstock

All Of Texas Is In Climate Zones (CZ) 2–4.

Click Here To See A U.S. Climate Zones Map: U.S Climate Zones Map

(If Link Doesn’t Work — Copy This Into Your Browser:) https://www.greenbuildingadvisor.com/article/climate-zone-map-including-canada

TEXAS Wall Insulation Requirements Over The Years:

Before 1960: Unlikely:  Your walls & attic are likely not insulated — unless a previous homeowner had it done.  Before 1950, homes were built with Knob & Tube wiring, so can’t be insulated.

1960-1964:    Some:  There’s a 1-in-4 (25%) chance the walls are insulated.

1965-1970:    YES–2″: U.S. Building Code required 2″ thick batt insulation.  Its R-Value ranged from R-4.5 — R-6.   TIP: These walls are a candidate for more insulation.

1971-1990:   YES–3″: – Your walls have a 3″ / R-11 fiberglass batt in them.   TIP: Adding more wall insulation isn’t cost-effective.

2006-2011: YES–3.5″: – For Climate Zone (CZ) 3 (include DFW) Walls have 3.5″ / R-13 fiberglass batt in them.  TIP: More batt insulation won’t fit inside a 2×4 wall.

2012-2020: YES–3.5″ + 1″ Foam Sheathing.  CZ-3–CZ-8  3.5″/R-13 Fiberglass Batt Insulation (inside the wall) & 1″/R-5 Foam Sheathing on the outside.

TIP: As of Jan 2023, Texas is using the 2015 International Energy Conservation Code (IECC).

TIP: Many Texas Cities Have Adopted The 2021 IECC.  Check with your City to know which IECC applies.

2021 IECC: YES: 3.5″ + 2” Foam Sheathing. CZ-3–CZ-8   3.5″/R-13 Fiberglass Batt Insulation (inside the wall) & 2“/R-10 Foam Sheathing on the outside.

Source: https://thehtrc.com/2020/insulation-requirements-2021-iecc

Source: https://basc.pnnl.gov/information/2009-2021-iecc-and-irc-minimum-insulation-requirements-new-homes

Image Source: Pixabay.com

All Of Texas Is WithIn Climate Zones (CZ) 2–4.

Image Source: Shutterstock

Climate Zones 5-8 Extend Through Northern Alaska    

Walls: 5-1/2“/R-20 Batt Insulation (inside the wall – with 2x6 exterior walls) + 1″ Foam Sheathing & Taped

OR

 Walls: 3-1/2″/ R-13 (inside the wall – with 2×4 exterior walls) & 2” Foam Sheathing 

Click Below To See A Chart Showing Wall Insulation Requirements Of The 2021 IECC:

2021 IECC Wall Insulation Requirements — All Climate Zones

(If Link Doesn’t Work — Copy This Into Your Browser:) https://www.jm.com/en/blog/2021/march/insulation-updates-to-the-2021-residential-iecc/

Click Here To See A U.S. Climate Zones Map: U.S Climate Zones Map

(If Link Doesn’t Work — Copy This Into Your Browser:) https://www.greenbuildingadvisor.com/article/climate-zone-map-including-canada

How “R-13+5” Insulation Requirements Are Typically Accomplished

 For Newly Constructed 2×4 Exterior Walls

R-13/3-1/2″ Fiberglass Batt Insulation Inside The Wall PLUS R-5/1″ Foam Board Sheathing + All Seams Taped.

The Beginning Of This YouTube Video Shows A Home Under Construction – That’s Covered With Foam Board Sheathing + Seams Taped.

Image Source: YouTube Embedded Video Link

Details About HOW “R-13+5” Insulation Requirements Are Typically Accomplished In New Construction

Image Source: Shutterstock

3-1/2″/R-13 Fiberglass Batt “Cavity” Insulation (Inside Exterior Walls).

PLUS

1″/R-5 Foam Board Sheathing As “Continuous” Insulation (Covering The Entire Outside Of Exterior Walls).

Shown: 1″ Thick / R-5 Foam Board Insulation (this product is various colors, based on manufacturer)

Image Source: Amazon.com Embedded Link

HOW Exterior Insulating Foam Board Sheathing Substantially Increases Exterior Walls R-Value.

Exterior walls insulating-value is typically expressed as the R-Value of the insulation inside the wall.  But there are many lumber wall studs inside walls.  At the studs, the R-Value drops to only    R-4.5.  Current building codes now require continuous insulation on the entire outdoor side of exterior walls.

• Adding R-5/1″ insulated sheathing to the exterior — raises the R-value of a 2×4 exterior wall (with R-13 insulation) — from R-10.7 TO R-17.
• This raises the R-Value to R-18 between wall studs.
• This raises the R-Value to R-9.5 AT the wall studs.

• 3-1/2″ fiberglass batt insulation R-Value = R-13.
• A 2 x 4 wall stud’s R-Value = R-4.5.
• AND Foam Board Sheathing Dramatically Reduces Air Leakage through exterior walls.  Seams between sheathing panels are taped.

Click Here To See A Thermal-Image Of An Exterior Wall Where It Meets The Ceiling:  Thermal Image Shows Cold Wall Studs In Exterior Wall

(If Link Doesn’t Work — Copy This Into Your Browser): https://twitter.com/thesignalpath/status/1373472144542330880

TIP: The wall studs appear purple — indicating that they’re notably colder than the Fiberglass Batt Insulation between the wall studs (which appears yellow).

Source: https://www.builderonline.com/building/building-enclosure/exterior-foam-insulation-problems-and-solutions_o

Source: https://www.ahfc.us/iceimages/manuals/building_manual_ap_1.pdf

Note: Foil-Faced (commonly called: “Polyso”) Foam Board Insulation Looks Similar To This (product shown is not polyso).

Image Source: Amazon.com

Polyisocyanurate (commonly known as: Polyso)

• Foil-Faced polyiso R-value = R-6.5 per 1″ inch
• Between the foil facings is a heat-set, closed-cell, polyurethane foam board.
• Polyso PERM Rating: .01 (extremely resistant to water-vapor movement).

• Polyso is a good choice for (vertical) Below Ground Installations — such as basement walls.
• Foil-Faced Polyso, installed on the outside of basement walls, minimizes water-vapor (within the ground) from passing through it & into the basement walls.
• Good drainage around building foundations is needed — to ensure polyso foam board panels are never immersed in water — as polyso absorbs & retains water.

TIP: Polyso Should Not Be Used (horizontally) Under A Concrete Slab

Because (installed horizontally) It Absorbs & Retains Moisture.

The major manufacturers (Owens-Corning & Celotex) of foil-faced polyso insulating foam board — both recommend its use below-grade for foundation WALLS.

In 1984, Dow Chemical buried polyso insulation samples (horizontally) for extended periods.

• When the samples were tested years later, foil-faced polyso absorbed an average of 5% (of its total volume) in water.
• Once wet — Polyso lost -40% of its R-value.
• Owens-Corning recommends that joints & edges of polyso be covered with aluminum tape for underground installations.

TIP: In a horizontal installation — the aluminum tape is likely to get wet and come loose.

A Better Suited Product For (horizontal) Under-Slab Installations is EPS Foam Board — Because EPS Retains Little Water (details below).

Sources:

• https://inspectapedia.com/Energy/Polyisocyanurate_Slab_Insulation.php
• https://www.greenbuildingadvisor.com/question/polyiso-under-slab-between-2-polyethylene-layers
• https://www.finehomebuilding.com/forum/polyisocyanurate-under-concrete-slab

Best For (horizontal) At-Grade (slab) OR Below-Ground (basement) Installations — EPS.

Expanded Polystyrene Foam Board (Commonly Known As: EPS)

Image Source: Amazon.com

Note: EPS Foam Board Insulation Looks Similar To This (the actual product shown is not insulation).

Expanded Polystyrene Foam Board (Commonly Known As: EPS) (R-4 per 1″).  It’s often called: “Styrofoam” (which is actually a brand name).

Common PERM Rating: 2-6 — per 1″ of thickness (somewhat resistant to water-vapor movement).

During EPS board manufacturing — beads of foam are fused together with pressurized heat or steam.

After the fusing – EPS still has air-voids between the foam beads.  Water-vapor easily passes through the air-voids.

EPS sheathing is commonly used for below-ground installations.

These Test Results Demonstrate WHY EPS Sheathing (described just above) Is Well Suited For Below-Ground Installations

In 2008, Stork Twin City Testing (an accredited independent testing laboratory) examined sheets of EPS & XPS removed (from a side-by-side installation) after 15 years in service on a (below-ground) basement foundation in St. Paul, Minnesota.

After Having Just Been Removed:

• XPS had 18.9% moisture content by volume.
• EPS had 4.8%. 

After 30 Days Of Drying:

• XPS had 15.7% moisture content by volume.
• EPS had  0.7% (7/10’s of 1%).

In 2012, The U.S. Department of Energy’s (DOE) Oak Ridge National Laboratory reported:

• “All samples of XPS insulation gained much more moisture (than EPS) during 15 years of contact with soil moisture.”
• The resulting XPS Energy Savings Performance loss was -10% for a basement and -44% for a slab-on-grade installation
• A Much Better Suited Product For Under-Slab Installations is EPS Foam Board — Because EPS Won’t Retain Much Water (details above).

Source:  https://www.insulfoam.com/the-dirt-on-below-grade-insulation/

Perm Rating Defined

A “Perm Rating: is a standardized measure of Water Vapor Permeability.  The higher the Perm Rating number, the more easily Water Vapor passes through a material.

• A VERY Low Perm Rating means the material is considered a Vapor-Barrier.
• Under the drywall — the most common material used for a Vapor Barrier — is a 6-mil Polyethylene plastic sheet.  Perm Rating = 0.06. (1 mil = 1/1,000th of 1″).

• A Low Perm Rating means the material is considered a Vapor Retarder.  XPS & EPS foam are considered Vapor-Retarders.
• XPS Foam Board Sheathing Perm Rating = 1.1 for a 1″ / R-5 Panel.
• EPS Foam Board Sheathing Perm Rating = 3.5 for a 1″ / R-4 Panel.

Water-Vapor Permeability Of Foam Board + Several Other Building Materials

NOTE: The Higher the perm rating — the More Easily Water-Vapor Passes Through the material. ** 10

•      0 perm   Glass — Water-Vapor can’t pass through glass.

•  2.5 perm   3/8″ drywall + 2 coats of latex paint.

• 2–5 perm  EPS foam sheathing (perm increases — as the thickness of the sheets increases).
• 1.10 perm  Most (if not all) 1″/R-5 XPS Foam Sheathing 
  0.1 perm   Plyso Sheathing with a Foil-Face.

• 10.0 perm  1/4″ Plywood Sheathing
•   2.0 perm  1/4″ Oriented Stand Board (OSB) Sheathing   Note: The more resin used in OSB — the lower its water-vapor permeability. *10

•   5.0-50.0   House Wraps (like Tyvek).  Note: House Wraps provide one-way vapor movement — from indoors to outdoors.

•   .40 perm  Brick Veneer
• <1.0 perm  3-Coat Stucco finish
•   .10 perm   Wood Siding
•  .40 perm   Vinyl Siding

TIP: Outdoor Finish Surfaces Are Not Waterproof — And Would Allow Water or Water-Vapor Into Exterior Walls Without A Weather-Restrictive Surface Below. 

End Of  Section About Types Of Foam Board Panels (sheathing).

To Skip This Section About Basement Walls — Scroll Down To The Next Double Lines.

On A Side Note: Unfinished & Finished Basement Walls

Basement Walls can be insulation on the; Outside, Inside, or Both Sides.

For Unfinished Basement: Since 2012, the International Residential Code (IRC) requires R-5 on the exterior of basement walls — starting in Climate Zone 3.

The R-Value requirement increases further north.

For A Finished Basement:

• Since 2006 the IRC requires insulation ALSO be installed on the inside of basement walls — IF the basement will be finished.
• With Foil-Faced Polyso (vapor-barrier) OR EPS (vapor retarder) on the outside of basement walls & + XPS OR EPS (vapor retarders) on the inside of basement walls — any water-vapor (that got past the outside sheeting) – will also pass through XPS OR EPS foam board panels.  This ensures the finished basement’s walls stay dry inside.

• TIP: Local Building Codes may exceed the IRC codes.  TIP:  Always build to the higher code requirement.

• TIP: Finished basement walls should not include polyethylene sheeting under the drywall. **
• Polyethylene is a Vapor-Barrer that can trap moisture (coming from outdoors through the basement walls) — inside the finished basement walls. **
• Trapping that moisture will lead to mold and/or rot. **

Sources:

• A. Source: https://www.finehomebuilding.com/project-guides/insulation/three-ways-to-insulate-a-basement-wall
• B. ** Source: https://www.jm.com/content/dam/jm/global/en/building-insulation/Files/

Will Polyso (Perm Rating 1.1) Foam Board on the outside of exterior basement walls Trap Moisture Inside Finished Basement Walls?   

NO — With Either XPS or EPS foam Under The Drywall On The Inside Of The Walls.

Perm Rating Defined

A “Perm Rating: is a standardized measure of Water Vapor Permeability.  The higher the Perm Rating number, the more easily Water Vapor passes through a material.

• A VERY Low Perm Rating means the material is considered a Vapor-Barrier.
• Under the drywall — the most common product used for a Vapor Barrier — is a 6-mil Polyethylene plastic sheet.  Perm Rating = 0.06. 1 mil = 1/1000th of 1″.

• A Low Perm Rating means the material is considered a Vapor Retarder.  XPS & EPS foam are considered Vapor-Retarders.
• XPS Foam Board Sheathing Perm Rating = 1.1 for a 1″ / R-5 Panel.
• EPS Foam Board Sheathing Perm Rating = 3.5 for a 1″ / R-4 Panel.

Water-Vapor Permeability Of Foam Board (+ several other building materials) 

NOTE: The Higher the perm rating — the More Easily Water-Vapor Passes Through the material. ** 10

•      0 perm   Glass — Water-Vapor can’t pass through glass.

•  2.5 perm   3/8″ drywall + 2 coats of latex paint.

• 2–5 perm  EPS foam board sheathing (perm increases — as the thickness of the sheets increases).
• 1.10 perm  Most (if not all) 1″/R-5 XPS Foam Sheathing 
  0.1 perm   Plyso Sheathing with a Foil-Face.

• 10.0 perm  1/4″ Plywood Sheathing
•   2.0 perm  1/4″ Oriented Stand Board (OSB) Sheathing   Note: The more resin used in OSB — the lower its water-vapor permeability. *10

•   5.0-50.0   House Wraps (like Tyvek).  Note: House Wraps provide one-way vapor movement — from indoors to outdoors.

•   .40 perm  Brick Veneer
• <1.0 perm  3-Coat Stucco finish
•   .10 perm   Wood Siding
•  .40 perm   Vinyl Siding

TIP: Exterior Finish Surfaces Are Not Waterproof. 

That’s Why A Weather-Restrictive Surface (like housewrap or foam sheathing) Is Installed To Exterior Walls Under The Finish Surface. 

This was Part-6-B of our multi-part article detailing how to lower heating (& cooling) costs.

This Was Part-6-B Of Our Multi-Part Article Discusses Insulation Requirments In Newly-Built (OR Altered Existing Exterior Walls.  The Entire Article Details How To Lower Heating (& cooling) Costs.

Al’s Plumbing — in Plano, TX provides Full-Service Plumbing; maintenance, repairs, and replacements for every plumbing component in your home.  Al’s sells and installs gas and electric water heaters.  Al’s is near your home in; Plano, TX; Allen, TX; Frisco, TX; and McKinney, Texas.  We service all homes in southern Collin County, TX, and northeastern Dallas County, TX with no additional travel charges.

Call Al’s Today To Discuss Any Concerns Or Problems You Have With Your Home’s Plumbing. 

We will arrange an appointment at your convenience.