FOAMULAR R-1 1/4 in. Fanfold XPS Underlayment

Lightweight, moisture-resistant XPS fanfold underlayment designed for re-siding and sheathing applications. The 1/4 in. thick, 4 ft. x 50 ft. board delivers R-1 thermal performance and folds for fast coverage and easy handling.

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Key Features:

• Moisture-Resistant XPS: Retains R-value even after exposure to water.
• Easy Handling & Install: Fanfold design cuts and scores simply; no special tools required.
• Re-Siding Ready: Ideal as underlayment/sheathing for re-siding projects.
• Durable Performance: Strong, lightweight board with long-term thermal retention.
• Low-Emitting & Certified: GREENGUARD certified; formaldehyde-free blowing agent with reduced GWP.

Please check the Product Data Sheet Here

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Specifications Table:

Specification	Details
Insulation Type	Foam Board Insulation (XPS)
Insulation R-Value	R-1
Thickness	0.25 in (1/4 in.)
Width	48 in. (4 ft.)
Length	50 ft.
Coverage Area	200 sq. ft.
Edge Profile	Square Edge
Faced or Unfaced	Unfaced
Compatible Install Surface	Concrete, Plywood, Wood
Interior/Exterior	Interior; commonly used for re-siding underlayment
Number of Pieces	1
Pack Size	1
Product Weight	13.2 lb
Sheathing Type	XPS
Insulation Features	Formaldehyde Free; GREENGUARD Certified; Low water absorption; High R-value retention
Warranty	Limited Lifetime

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Frequently Asked Questions (FAQ):

Q: What are the dimensions and coverage?
A: Each fanfold measures 1/4 in. thick, 4 ft. wide, and 50 ft. long, covering 200 sq. ft.

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Q: Where can I use this product?
A: Commonly used as re-siding underlayment or insulating sheathing over wood, plywood, or concrete surfaces.

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Q: Is it faced?
A: No, this product is unfaced XPS foam board.

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Q: How moisture resistant is it?
A: XPS construction provides low water absorption to help maintain R-value in wet conditions.

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Q: Do I need special tools to install?
A: No. It scores, snaps, and cuts easily with standard utility knives.

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Streamlined Sheathing with a Sleek, Modern Edge

This fanfold insulation creates a crisp, continuous plane behind new siding, elevating exteriors with a polished, tailored finish. I love its subtle flexibility—the panels fold effortlessly to glide across large walls, minimizing seams and visual clutter. Pair it with fiber-cement or cedar cladding to achieve a refined envelope and improved comfort. It’s a quiet luxury—performance you feel, with a look that’s impeccably composed.

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Upgrade your re-siding project with FOAMULAR fanfold insulation for faster installs, lasting R-value, and a cleaner finish—add it to your cart today.

Installation