Frequently Asked Questions

Is GreenGuard “Green”?

Do your products have recycled content?

What is extruded polystyrene?

Does your XPS foam rot?

What about mold, mildew, and insects? 

Wood is a good insulator. Why would I want foam on the outside of my building?

What is the difference between regular insulation (batts or blown fill) and foam boards? 

Does your foam have sound resistance properties?

Some GreenGuard siding underlayments have a reflective surface and claim a higher R-Value. How does this work?

Should the reflective surface be placed to the outside or the inside?

Can fanfold siding underlayment be used in place of building wrap?

Why do you need building wrap?

If I use spray foam insulation on the inside of my wall cavity, why do I need building wrap?

Is it OK to install the building wrap upside down, sideways, or with the printing facing the wall?

What kind of building wrap should be used behind fiber cement siding?

If I have a brick wall, why do I have to worry about water?

I understand that foam sheathing insulates better than wood, but foam sheathing does not have structural properties. How can I use foam sheathing in place of wood sheathing and maintain structural stability?



Where can I buy GreenGuard products?

GreenGuard products are sold through building material distributors and dealers in the U.S. and Canada. To find a source near you, please 
Click Here to submit an inquiry and a representative will contact you.

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Is GreenGuard “Green”?

Yes, GreenGuard is green in more than color. GreenGuard products help reduce energy consumption and improve the durability of the structure. Plus GreenGuard XPS insulation contains up to 30% post-industrial recycled content. Click Here to see the full GreenGuard Green Building story.

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What is Extruded Polystyrene?

GreenGuard insulation is extruded polystyrene (commonly referred to as XPS), a foam insulation material manufactured by an extrusion process. Plastic resin pellets are fed into an extruder, blended with a blowing agent, and extruded through a die into the shape of the insulation board. The result is a board with consistent closed-cell construction that is rigid, sturdy, does not crumble, does not absorb water, and has an R-Value of 5.0 per inch of thickness. For more information, Click Here to view the Extruded Polystyrene Foam Association website.

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Do your products have recycled content?

Yes. GreenGuard insulation board contains up to 30% post-industrial recycled materials, while GreenGuard building wraps contain up to 5%.

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Some GreenGuard siding underlayments have a reflective surface and claim a higher R-Value. How does this work?

Reflective surfaces reflect (do not emit) radiant heat. For example, our 3/8” thick siding underlayment has an R-Value of 1.5. With a reflective surface, the effective R-Value of that product can be as high as 3.6, when installed using a ½” uniform, parallel dead air space on the reflective side. This follows the “ASHRAE Handbook of Fundamentals” basic principles of reflective insulation properties. With the air space partially achieved, the effective R-Value is something between the 1.5 of the foam and the maximum 3.6. Be aware that some manufacturers may make misleading claims of very high R-Values achieved with reflective surfaces. For information on reflective surface thermal performance, 
Click Here
 to visit the Reflective Insulation Manufacturers Association website

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Should the reflective surface be placed to the outside or the inside?

Since reflective surfaces are designed to reflect radiant heat, it is common practice to install the radiant surface to the predominantly warm side of the wall. In an extremely cold climate, that would mean installing with the reflective surface inward. In a hot climate, it would be installed with the radiant surface outward. In climates that are more balanced, it may be installed either way, depending on whether the objective is to reduce heat loss in winter or reduce heat gain in summer.

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Does your XPS foam rot?

No, XPS foam does not rot. XPS foam is designed to be used behind walls and below grade, not as an exterior finish. It will eventually deteriorate with prolonged exposure to the sun, so it needs to be covered with a cladding.

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What about mold, mildew, and insects?
GreenGuard extruded polystyrene (XPS) foam insulation and building wraps are made of synthetic materials that are generally recognized as not providing a food source for insects, fungus, mold, or mildew. GreenGuard building materials should always be properly installed and stored.

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Wood is a good insulator. Why would I want foam on the outside of my building?

Contrary to common conception, wood is not such a good insulator, at least when measured against other insulating materials. A 2 x 4 wall stud (3½” across) covered by 7/16” thick OSB sheathing has a total R-Value of about 4.0. In comparison, XPS sheathing only ½” thick has an R-Value of 3.0, and 1” thick XPS insulation board has an R-Value of 5.0. By replacing or covering wood sheathing with XPS insulation, you create a “thermal break.” That is, you break the transfer path of heat and cold through the wood framing and sheathing.

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Why do you need building wrap?

Building wrap is used in both residential and commercial applications for two primary functions: (1) as an air barrier or retarder and (2) as a secondary water barrier to block water that gets through the exterior cladding. Both functions work to improve the energy efficiency and durability of the structure.

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Is it OK to install the building wrap upside down, sideways, or with the printing facing the wall?

In the case of RainDrop® building wrap, the product must be installed with the correct side to the exterior and the drainage channels vertical, or at a slight angle from vertical, for the product to function properly. (Horizontal drainage channels do not really work.) Performance of flat wraps is not particularly affected by install direction, from a fabric perspective. However, installing wrap consistently indicates that you have followed guidelines to achieve a proper water-resistive barrier. Care should be taken to install the wrap in a shingling fashion (check local codes for overlap requirements). In addition, the appearance of the final job sends a message. You can guess what message a sloppy, inconsistent installation sends.

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If I have a brick wall, why do I have to worry about water?

Brick, like other exterior claddings, does a good job of deflecting hard rain. However, water soaks through brick. That is the reason you need air space between brick cladding and the wall sheathing and “weep holes” at the bottom of a brick wall. You also need a secondary weather barrier to protect the wall structure from water that gets behind the brick. The same is true for other claddings: wood, vinyl, fiber cement, stucco, and stone.

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Can fanfold siding underlayment be used in place of building wrap?

GreenGuard siding underlayments are in compliance with the ICC-ES “Acceptance Criteria for Foam Plastic Sheathing Panels Used as Weather–resistive Barriers” (AC71). This means that GreenGuard fanfold siding underlayments may be used in either new or retrofit construction applications without an additional water-resistive barrier (felt building paper or building wrap), when they are installed in strict accordance with the installation instructions. (These instructions are available in the Product Downloads.)

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Does your foam have sound resistance properties?

GreenGuard XPS foam is not designed as a sound control product. While it does reduce sound intrusion a small amount, that is not its purpose. To design a wall with true soundproofing, you should research the products and techniques for that specific purpose.

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What is the difference between regular insulation (batts or blown fill) and foam boards? 

Batt and blown fill insulations (fiberglass, cellulose, etc.) are a more economical way to achieve insulation in wall cavities than foam boards. A common batt insulation used in the 3½” thickness of the cavity in a 2’ x 4’ wall structure has an R-Value of either 11 or 13. The same thickness of XPS foam board would yield an R-Value of 17.5 to 18, but at a higher cost. However, the rigidity and consistency of the XPS foam board, as well as its resistance to water, make it an excellent product for the outside of the wall, where even in thicknesses of ½” it adds an insulating R-Value of 3.0.

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What kind of building wrap should be used behind fiber cement siding? 

Fiber cement siding, like wood or vinyl siding, is nailed tightly to the wall sheathing. If water gets through the siding, it has no place to go. The best type of wrap to use is a drainage wrap such as RainDrop®, with built-in drainage channels to move water away from the wall.

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If I use spray foam insulation on the inside of my wall cavity, why do I need building wrap?

Spray foam wall cavity insulation gives excellent R-Value, is consistent, and, if installed to do so, can be a barrier to air infiltration over parts of the wall. However, it does nothing to protect the wood sheathing. A building wrap is required to protect the exterior wall sheathing against water intrusion. In addition, the building wrap adds another barrier to air infiltration.

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I understand that foam sheathing insulates better than wood, but foam sheathing does not have structural properties. How can I use foam sheathing in place of wood sheathing and maintain structural stability?

XPS foam sheathing not only offers better insulation than wood sheathing, but it also provides water resistance. You can use GreenGuard XPS foam sheathing in place of wood sheathing by employing alternate bracing methods such as “let-in bracing” or steel strapping to achieve structural properties. Another alternative is to use wood sheathing in the corners to achieve structural properties and foam sheathing in the non-structural portions of the wall. This approach is done following the “prescriptive method” outlined in the codes. For general guidelines on your local seismic and wind zones, please download our PLYGOOD Ultra Wall Bracing Guide (Click Here to access Product Downloads). (You must check your local codes for final requirement.) Another simple option is to sheath the house completely in wood and install a layer of XPS insulation on the exterior as added insulation.

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