Interior Guides
1. Installing the panels
We encourage a process called dry stacking which speeds up the workflow when it comes time to glue panels. Essentially, you perform a mock set-up of your InSoFast walls by stacking the panels without any adhesive or finished mechanical attachment. You can troubleshoot all of the more complicated steps such as cutting panels to fit around pipes and windows and then arrange them in the order they need to be installed later.This will avoid having to cut and adjust panels with glue on them.
We recommend that you stack the panels with what is called a running bond or stagger joint. Here is how.
- Start your installation with a full panel in the bottom corner of your wall. This not only makes it easier to set up an even alignment, it also gives you the option of working in two directions along your walls. After the first panel is set in place, continue adding consecutive panels side-by-side until the row is complete.
Off set or stack bond pattern
- To create the second row, attach the freshly cut 32” section in the corner you started directly above the first full panel. Eliminate waste by using the remaining 16“ section to start the second row of the adjacent wall.
- Continue adding panels along the second row until complete. You can repeat the same process of staggering cut and uncut panels for each new row.
The interlock pattern uses the same concept as brick-laying. By offsetting the edges of each row of panels, you'll create a structurally locked wall that bolsters the InSoFast panels' ability to self-level.
Begin by cutting the second row of panels
- After placing the first row of panels, use a knife or saw to cut a new panel along the demarcated channel line into a 16“ and 32” section.
- To create the second row, attach the freshly cut 32” section in the corner you started directly above the first full panel. Eliminate waste by using the remaining 16“ section to start the second row of the adjacent wall.
- Continue adding panels along the second row until complete. You can repeat the same process of staggering cut and uncut panels for each new row.
This video will show how the panels interlock reduces waste and how to adjust the panel's layout to work around existing conditions.
When working with existing conditions like metal electrical conduit the height of the panel can be cut to account for where the panel's raceway and conduit will meet.
The blue chalk line is the top of the panel marked to indicate the height measured from the floor to adjust for the raceway's location. We cut off 1 1/2" from the bottom of the panel so to align the conduit to the raceway.
Ed presses the panel to the electrical box to indicate the foam needed to be removed from the panel.
Remove the foam with a razor knife or saw.
Cut and trim the panel until it fits. Apply these techniques to all difficult cuts.
Simple Templates for Complicated Cuts
Basic how to handle bumps or projection that can't be removed.
After pre-cutting and fitting all the panels with a dry stack, a dry run, (why mess with glue when cutting and fitting panels) to determine the layout, Ed and Dean are ready to adhere the panels to the wall. Watch them do it in less than 10 minutes.
Masonry Adhesives
Thin set masonry adhesives can be used over masonry brick or block walls. The adhesives have a high build and can be used over rough and out of plumb walls with great results. Up to a 3/4" bead of adhesive is applied to the dovetailed ribs on the back of the panels. Enough adhesive must be used to create that cast in place bond.
The most common method to apply the thin set mortar is with a mortar pointing bag.
Compatible adhesive/base coat data sheet for technical data and information sheet.
- Sto Primer/Adhesive 80100 is an acrylic-based material used as an adhesive. It is a two-component product to be combined with Portland cement.
- Senergy Alpha Base Coat Alpha Base Coat is a 100% acrylic adhesive and base coat that is field-mixed with Type I or Type II Portland cement. It has a very creamy texture that spreads easily.
- Dryvit Genesis High-performance, fiber-reinforced, dry mix, polymer-modified, cementitious adhesive and base coat specifically formulated for use with Dryvit system.
How to handle Inside and Outside Corners
| Inside Corners Corners that form an inside angle |
Outside Corners Corners that protrude into a room |
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We recommend starting an InSoFast project on an inside corner.
Turning Corners cutting and gluing panels. Cut the panels a 1/4" less than the actual measurement, this will relieve any pressure in the corner that my force panels to pop out.
Scribing the measurement onto the panel for easy cutting.
Cutting the panel a 1/4" shy will also allow for an easy fit for the tongue and groove of the panels edges. Some basement applications of poured in place concrete have rounded corners, trim the panel's edge to keep the panel flat and tight to the wall.
Add a bead of adhesive to the cut edge of the panel to secure the outside edge to the wall.
Install the first panel flush with the corner edge of the concrete wall making sure to place a solid-backing bead of adhesive near the edge of the cut. On the cut-off piece or second panel run two beads of adhesive. The first bead, running approximately 1" from the edge, will bond the foam of the InSoFast panels together at the corner.
Turning the corner, the next panel should fit snug against the first panel. The second bead, running approximately 3" from the edge of the panel, will bond the foam of the InSoFast panel to the concrete. Securing drywall to a foam corner.
Important: some steps of this process will involve applying adhesive directly to a panel's foam surface. We strongly recommend using PL Premium 3X Stronger Construction Adhesive for this purpose. This glue has been tested to work with the EPS foam.
Inside Corners
Cut the first panel about ¼" less than the actual measurement needed so that the panel is not tight to the corner. Turning the corner, the next panel should fit snug against the first panel.
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Outside Corners
Corners that protrude into a room These corners need a metal corner bead attached to them. If necessary, mark and cut the first panel flush with the corner. You will use the cut off piece, or a new panel, to wrap around the other side of the corner. Install the first panel flush with the corner edge of the concrete wall making sure to place a solid-backing bead of adhesive near the edge of the cut. On the cut-off piece or second panel run two beads of adhesive. The first bead, running approximately 1" from the edge, will bond the foam of the InSoFast panels together at the corner. The second bead, running approximately 3" from the edge of the panel, will bond the foam of the InSoFast panel to the concrete.
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Corners that form an inside angle
Gluing The Panels
When starting a panel or going around corners or opening we recommend that you add additional adhesive on the edges of the panels. This will secure the panel edges and give you a tighter finished wall. Add an extra bead of glue 1/2" back from edge of the panel around all corners and openings like windows and doors. Keeping the glue 1/2" back keeps it off your hands and from oozing out around the edges.
Related Documents
- Use a metal corner angle (3" x 3", 25ga sheet metal) to wrap outside corners. Generally available in the roofing/flashing section of home improvement stores or drywall supply yards.
- Place a bead of adhesive approximately 1-2" from each side of the corner. Press 25 ga. sheet metal angle into adhesive.
- Sheet Metal Corner Angles for Drywall (PDF, 206kb)
Frame all openings to ensure there is a sturdy attachment surface for drywall or trim in case the InSoFast studs do not perfectly meet the edges.
Framing Materials
You can use pressure-treated lumber, western cedar, or cellular PVC for the framing material. You want to make sure to limit the contact between natural wood and the moisture in concrete. Alternatively an opening like a window or an exterior facing corner a sheet metal utility angle can be used to frame around an opening.
Related Documents
To attach the framing to concrete, you can use the same methods you've selected for the InSoFast panels. We recommend Tapcon concrete screws, Perma-Grip nails, or PL Premium adhesive. According to Loctite, the bond strength between pressure-treated lumber and concrete can withstand hundreds of pounds of pull-off and shear loading.
Important: EX 2.5 panels are easier to frame than UX 2.0 panels because they are the same depth as commonly available framing lumber. UX 2.0 panels will require additional advanced carpentry techniques in order to cut the framing to fit. For this reason, we recommend DIYers choose EX 2.5 for their projects. For more information on the benefits of EX 2.5, read 4 Reasons to Choose EX For Your Basement Project.
Installation
Install the framing around windows, doors and openings before adding InSoFast to your walls. Make sure the framing is at least 2" wide for attachment purposes. The depth should be as deep as the InSoFast panels, in order to run flush across the wall. Depending on the panel used, this application requires 2" (UX) or 2-½" (EX) framing or furring materials. This can be an uncommon size for such materials and may require extra work.
When running the InSoFast panels, cut as necessary to fit around the frames. To figure out where to cut, place a full panel directly over the framing and press hard so as to leave an indent in the panel. Then cut along the indented line. It is okay to cut the panel ½" shy of being tight as you can fill the gap with spray foam later.
Finishing
Add an extension jamb and trim.
An extension jamb is a piece of wood or framing material that extends from the window past the edge of the framing. It will cover the concrete and can be used as part of the finishing trim around a window. The extension jambs can be glued or nailed to the opening.
Extension jambs should overhang your frame and panels by at least the width of your drywall - minimum ½"
Attach a minimum of ½" drywall to your walls by screwing to the InSoFast studs. Around the edge of windows, doors and openings, screw the drywall to the previously installed frames
See Also
 Wood Extension Jamb and Trim (PDF, 26.6kb)This is a typical option for basement windows where there is no room for a sub jamb. If you have a basement window with very little room for extension jambs, consider using stairway skirt boards. They have a thin profile with a finished edge. This board can be glued directly to the concrete. If you wish to have backing to nail the trim, wrap the entire opening with 2" wood furring attached directly to the concrete. The InSoFast panels will butt up to the wood furring. |
 Wood Extension Jamb and Trim with Solid-Backing (PDF, 37.6kb)This is a great option if you are installing a new egress window, or you have a window with room for a sub jamb as well as an extension jamb. If you do not have room for the sub jamb, fasten 2" wood furring around the opening directly to the concrete. This will look like a picture frame around the window. Butt the InSoFast panels to the wood furring. |
 Drywall Return over Wood Framing (PDF, 36.3kb)Use this option if you want to have a drywall return back to the window. Wrap opening with 2" or 1" sub jamb. If you are challenged for room, wrap the entire opening with 2" wood furring attached directly to the concrete. This provides a nailing surface for the drywall corner bead. The InSoFast panels will butt up to the wood furring. Adhere moisture resistant drywall or cement board to the concrete. |
 Drywall Return over InSoFast UX Panels (PDF, 37.6kb)If you have room, you can do insulated returns with the InSoFast panels. Adhere the 3" galvanized sheet metal angle to the InSoFast panels. This provides easy attachment for drywall and corner bead. |
8ft-high ceilings make for a very easy InSoFast installation. Because each panel is 2ft high, you won't need any modifications at the top of the wall. In fact, this is the case for any ceiling height evenly divisible by two. 6ft ceilings, 10ft ceilings, 24ft ceilings: no modification.
But what do you do with an uneven ceiling height? You have to cut the panels. Think of InSoFast panels as a carpentry shortcut for insulation and framing. It doesn't have to be a masterpiece, it just has to work. The panels are designed to lock together in a tight pattern, but you shouldn't feel discouraged from breaking this pattern if it makes more sense in your installation.
Cut, carve, and reshape the panels as much as your walls require. Any gaps, cracks or imperfections can be sealed later with expanding foam.
Cutting panels to fit
Measuring
Once you've reached the final row at the top of your wall, measure the distance between the ceiling (or joists) and the top-most "tongue" edge of the previous row of panels.
Here we turn the panel upside down to mark the size of the cut 12 1/4" so we cut the panel short or shy 1/4" to (12") to accommodate for the tongue and groove interlock..
Note: Cutting the panels to fit between floor joists is time consuming and may leave an uninsulated air pocket. For information on how to properly insulate this area see our page: Technical > Interior Guides > Rim Joists
Measuring it by the "tongue" edge will give you a little extra space to be able to move the panel into place. Gaps and cracks should be sealed with an expanding foam later.
Pro Tip: You can get a good measurement by turning the panel upside-down and pressing its top-most edge against the ceiling. Make a mark directly on the panel where it meets the "tongue" edge of the previous row. When you flip the panel right-side up again, the mark will denote the height at which it should be cut in order to fit the imperfect space. See the video above for a visual demo.
Cutting
Use the measurement to cut the last row of panels horizontally. You will likely need a hand saw or power tool to slice through the embedded studs.
If your scraps do not have a way of interlocking with the "tongue" edge of the previous row, you can use a razor blade to remove the tongue. By removing the tongue, you will have a more even block surface to fill-in with a scrap panel. Gaps and cracks should be sealed with an expanding foam later.
Installing
Install the "bottom half" of the newly cut panel in the final row. The bottom half will still include the interlocking "groove" edge that meets the "tongue" edge of the previous row.
Because your cut was made to the "tongue" edge, you should have a little extra room to place the panel. Gaps and cracks should be sealed with an expanding foam later.
You can add a bead of adhesive to the panel before you place it at the top of the wall.
Using scraps
Don't discard any scraps made from cuts until you've completely finished your installation. InSoFast scraps are highly re-usable
- From Ceiling to Floor:
If you made cuts to meet an imperfect ceiling height, use the other half of the cut pieces as the first row of a new wall. This section is considered the "top half" of the cut panel. Its cut edge will sit on the floor, while its top edge will meet the next row of panels. The top should have an intact interlocking "tongue" edge. - Scraps without interlocking edges:
If most of your walls are complete and most of your fresh panels have been used or cut, you can use scraps to meet the imperfect ceiling height. You will essentially follow the same procedure for measuring and cutting as listed above with variations dependent on availability of panel interlocks.
Printable Instructions
2. Installing electric, windows, drywall and other finishes.
Making Cut-outs for New Outlet Boxes
Professional Tool for Cut-outs
Hot knives are clean and professional cutting tools and one of the many options for cutting out for electrical boxes, but a razor knife will work just as well if you are not a professional installer.
Start by pressing the outlet box against the foam of the panel to create a mark. Cut out the foam approximately 1/4" - 1/2" larger on all sides than the impression. While a tight-fitting electrical box would look nice, it is better to have extra room to seal around the outlet box with expanding foam.
Cut out the foam with a snap-off blade knife. Continue to cut out to the nearest horizontal or vertical chase. The vertical chases are centered directly between the InSoFast studs and are indicated by a line on the front side of the panel. The horizontal chases are located at the top of each panel.
Electrical wiring chases are one of the many features built into the InSoFast panel. They run vertically at 16″ on center and horizontally at 24″ on center in the panels. This grid-work provides easy access to pull the wiring to any location. The chases also address the necessary separation from the drywall that's required by electrical code.
Running or Pulling wires.
Romex® type wiring is simple to install. Individual runs can be pushed or slid through the horizontal or vertical chase ways up to 12' from box to box or up into the floor system.
If you have any difficulties sliding the wire through the chase way, bend over the end of the Romex® wiring. The use of a fish tape is generally not required unless pulling multiple wires at one time. If you wish to eliminate the fish tape, slide one wire through and then tape the multiple wires on. Metal flex conduit, MC Flex, or AC Flex installs in the same manner as Romex wiring.
It is okay to over cut the InSoFast Panel.
To make things easier and give you extra room to work with the wiring, cut the opening up to the horizontal chase way. Once the electrical work is completed the foam can be pieced back into place and air sealed with spray foam. Alternately if homeruns or larger openings are needed the foam can be cut back to the studs and completely removed.
Save the cut foam to use later after the electrical work is completed.
Installing Outlet Boxes
Electrical Box Configurations
You can use any code approved plastic, metal, or fiberglass electrical boxes.
Types of Wiring
InSoFast panels are designed for use with standard Romex® (NM sheathed wire), MC Flex, AC Flex, or rigid metal conduit.
InSoFast wiring chases are located 1¼" below the surface of the panel (National Electric Code - NEC Article 330-4d and 300-41a) and are designed to keep the wiring safely within the panel without the use of protective metal plates. The chases are spaced 16" o.c. vertically and 24" o.c. horizontally. This offers the same protection as a wire running through the center of a 2x4 wall.
Secure electrical boxes directly to the concrete wall with adhesive or a mechanical fastener, anchors or screws (for masonry walls). Once securely fastened to the wall, fill the extra space around the box with expanding foam. The foam air and water seals the electrical. All of our recommendations are based on National Codes requirements. Please check with your local building departments for local amendments.
Allied Moulded Products, Inc.
Offer nonmetallic electrical boxes and enclosures in to fit our 2" thick panel for residential, commercial and industrial markets.
Brand: fiberglass BOX Single gang electrical box for use with nonmetallic sheathed cable.
- Mounting Description: Metal ears
- Box Type: Wall - Switch/Receptacle
- Box Features: Metal ears, Speed "K" nonmetallic clamps
- Installation Type: Old Work
- Height:3-1/4 in
- Width:2-3/8 in
- Depth:2-1/2 in
- Volume:14 cu. in.
- Number of Gangs:1
When working with existing electrical wiring various extension rings can be used to add additional wiring capacity to the electrical box. This extension ring features a keyhole design, this extension can be used to add additional wiring capacity to almost any box.
Rigid Metal Conduit
When working with existing conditions like metal electrical conduit the height of the panel can be cut to account for where the panel's raceway and conduit will meet.
The blue chalk line is the top of the panel marked to indicate the height measured from the floor to adjust for the raceway's location. We cut off 1 1/2" from the bottom of the panel so to align the conduit to the raceway.
Ed presses the panel to the electrical box to indicate the foam needed to be removed from the panel.
Remove the foam with a razor knife or saw.
If you are planning on using rigid metal conduit, install the ½" metal conduit at the same height all the way around the project. Use box offsets so that the conduit is setting tight against the concrete wall.
4"Square Boxes: Use with lighting fixtures, switches, receptacles, and in other applications where multiple conductor runs are split into two or more directions.
Square Metal Electrical Box Cover or mud ring.
You can cut the InSoFast panels as needed to align the horizontal chase way with the metal conduit. The cut off portion can be used at the top of the wall. This method utilizes the tongue and grooves to their best potential.
E3802.1 Installation and support requirements
InSoFast wiring methods shall be installed and supported in accordance with Table E3802.1.
INSTALLATION REQUIREMENTS |
| Where run parallel with the framing member or furring strip, the wiring shall be not less than 11/4 inches from the edge of a furring strip or a framing member such as a joist, rafter or stud or shall be physically protected. (InSoFast panels raceways satisfy the required protection of 1¼”) |
| Bored holes in framing members for wiring shall be located not less than 11/4 inches from the edge of the framing member or shall be protected with a minimum 0.0625-inch steel plate or sleeve, a listed steel plate or other physical protection.( Raceways that are running through InSoFast studs do not require steel plates because they meet the 1 ¼” depth requirement) |
| Where installed in grooves, to be covered by wallboard, siding, paneling, carpeting, or similar finish, wiring methods shall be protected by 0.0625-inch-thick steel plate, sleeve, or equivalent, a listed steel plate or by not less than 11/4-inch free space for the full length of the groove in which the cable or raceway is installed.(InSoFast panels are engineered with a groove that forms a raceway with the required protection or “free space” of 1 ¼” along the full length of the groove) |
| Securely fastened bushings or grommets shall be provided to protect wiring run through openings in metal framing members. (InSoFast panels have no metal or sharp edges) |
| The maximum number of 90-degree bends shall not exceed four between junction boxes.(This does not apply to NM or Romex® wiring) |
| Bushings shall be provided where entering a box, fitting or enclosure unless the box or fitting is designed to afford equivalent protection. (does not apply to NM or Romex® wiring) |
| Ends of raceways shall be reamed to remove rough edges. (Raceways of InSoFast panels have no metal or sharp edges ) |
| Maximum allowable on center support spacing for the wiring method in feet. (The raceways of InSoFast panels provide continuous confinement and support for wiring) |
| Maximum support distance in inches from box or other terminations. (NM or Romex® wiring must be secured in place within 8” of boxes without cable clamps. Securing wiring with expanding foam adhesive (Great Stuff®) satisfies this requirement) |
Before you start your project you should plan out how you intend to run the electrical wiring. Use the built-in wiring chases as a guideline. If there is pre-existing electric running along your walls that does not match up with the InSoFast chases, you have a few options:
- Measure the distance of your channels to the floors and corners. Cut the first row of panels to adjust for this distance so that the built-in channels will line up.
- Carve a custom groove into the panels to add the necessary space for the wiring.
- Re-run your electric to follow the channels.
Some projects may require the consultation of a certified electrician.
Pulling wires around corners or changing directions from wall to ceiling with InSoFast is simple. Once the wall/surfaces is up and the adhesive is set you can cut out and replace the insulation easily. This corner technique will also work at junctions at frame walls. You can even update an pull wires through InSoFast after the wallboard or gypsum panels are on the wall.
It is okay to over cut the InSoFast Panel.
To make things easier and give you extra room to work with the wiring, cut the opening up to the horizontal chase way. Once the electrical work is completed the foam can be pieced back into place and air sealed with spray foam. Alternately if homeruns or larger openings are needed the foam can be cut back to the studs and completely removed.
Save the cut foam to use later after the electrical work is completed.
Installing Outlet Boxes
Secure electrical boxes directly to the concrete wall with adhesive or a mechanical fastener, anchors or screws (for masonry walls). Once securely fastened to the wall, fill the extra space around the box with expanding foam. The foam air and water seals the electrical. All of our recommendations are based on National Codes requirements. Please check with your local building departments for local amendments.
Fitting around Pipes
The easiest way to work around pipes and other obstructions along your wall is to simply carve the InSoFast around it and fill the gap with spray foam.
When the spray foam has set, use a knife to shave off the excess.Below are a few options and ideas for how to finish around obstructions that stick out past the InSoFast panels.
Cut the InSoFast panels approximately ¼" inch shy of the pipe's perimeter.
Any time you cut an InSoFast panel you should put an extra bead of adhesive on the foam near the cut in order to solid-back the panel to the wall.
Fill in the gap with expanding spray foam after you've finished your installation to seal around the pipe.
Pro Tip:InSoFast panels come in big cardboard boxes which can be utilized in several practical ways throughout your installation process. In order to make the right cuts around a pipe, we recommend using with a piece of the cardboard box to make a template of the necessary shape. Once you have the right template, simply trace it over the InSoFast panel and make your final cuts. Simple Templates for Complicated Cuts Video
Building out the wall
If your floor plan allows for it, you can conceal the pipe inside an intersecting wall such as a bathroom plumbing wall or partition wall. Be sure to provide an access cover for the cleanout. Please read our intersecting wall guide at Technical > Interior Guides > Attaching Intersecting Walls for information.
Bringing out the entire wall by screwing furring strips to the InSoFast studs is another option. While this option works well, it will have a greater impact on your final floor space.
One DIY-er in Vermont had a very tricky set of pipes in his basement so he decided to cover over all of them with this method. Luckily, he had enough clearance behind the pipes to fit InSoFast EX 2.5 panels. You can read about his project here: Explore > Featured Projects > Frozen Walls and Plumbing Obstacles.
Running Pipes through the Electrical Channels
While this may sound like an ideal way of hiding ugly pipes in your home, we typically discourage running pipes behind the panels as this may result in freezing and bursting.
Covering pipes behind the insulation separates them from the warm conditioned space and exposes them solely to exterior temperatures. Even if you have never had problems before, this method can actually create the conditions that allow them to freeze.
However, you may be able to successfully install piping, such as PEX, behind the panels if you are in a climate zone that does not experience freezing ground temperatures.
You can also mitigate the potential of frozen pipes by insulating your walls on both the interior and exterior sides. Insulating only on the exterior side would not only be more budget-friendly, it may also be more effective.
InSoFast panels have no food value and the panels are considered a 2" or 2 1/2" thick insulated vapor/AIR barrier that will not to support mold growth. So here are the top 6 areas to make sure you air seal.
- The TOP of the wall.
- Along the floor line.
- Inside corners.
- Around any window openings.
- Openings like air registers.
- All service openings like electrical boxes.
Drywall and Other Finishes
Drywall is installed over InSoFast panels in the same exact way it is installed over traditional framing. Simply attach drywall to the InSoFast studs using all-purpose coarse drywall screws. Type W Bugle Head Screws attach single layer gypsum panels to InSoFast framing. Screws provide greater holding power than wallboard nails, minimize popping and help prevent damage to the panels.
Follow the standards set forth by the drywall industry that the screw be at least a #6 x 1-5/8'' long Phillips Drive Coarse Thread Drywall Screw for the Flat Panel UX2.0 and a #6 x 2'' long Phillips Drive Coarse Thread Drywall Screw Flat Panel EXi 2.5. At a minimum the screw length should be long enough to pierce through the InSoFast stud 1/2" so the tapered point is all the way through the stud.
This picture demonstrates the variety of fasteners that will work with the stud and not crack or split for a secure and positive attachment for the finishes.
Installing the Drywall
Depth Stop for Drywall
Drywall Screw Setters with your drill. They control the depth of the screw when driving in drywall, particle board and plywood.
Interior applications to attach drywall we recommend a coarser thread bugle head drywall screw. The length of the screw long enough that the sharp point is all the way through the stud.
You should nail base and trim boards into the studs using trim nailer or hand nails.
Things to keep in mind:
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- Allow 24-hours for the PL Premium 3X Stronger Construction Adhesive to fully cure before attaching any finishes.
- When installing InSoFast in a corner, be sure to solidly back the panel’s edges that don’t end in studs. See (Corners, Intersecting Walls) for more details.
Other links to get you started:
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- Drywall Material Calculator: https://www.inchcalculator.com/drywall-calculator
- Drywall Material Calculator: https://www.homedepot.com/account/view/calculator/drywall
- Drywall Installation Cost Calculator: https://www.homewyse.com/services/cost_to_install_drywall.html
- Alternate Finished: https://www.insofast.com/explore/stone-and-stucco.html
Drywall Fire Code and Alternatives
Important: InSoFast panels are manufactured using a flame retardant foam and are classified as rigid foam plastic insulation. They fall into the same class as pink, blue and yellow insulation boards which are required by code to be covered by ½” drywall or any other approved 15-minute thermal barrier (IBC 2603.4). If choosing an alternative to drywall it is important to check with your local building code official to make sure it meets your local requirements.
Securing Drywall at Outside and Inside Corners
*Please note that although this is a video about installing drywall in a shipping container the metal corner utility angle will work for this application too.
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- Use a metal corner angle (3" x 3", 25ga sheet metal) to wrap outside corners. Generally available in the roofing/flashing section of home improvement stores or drywall supply yards.
- Place beads of adhesive on the back side of the metal angle and press it against the corner. If necessary, hold the angle in place with duct tape.
- Hang drywall by screwing all-purpose drywall screws into the InSoFast studs and into the sheet metal corner angle. Install a second metal corner angle over the drywall using all-purpose drywall screws.
Place a bead of adhesive approximately 1" from each side of the corner. Press 2" x 2" - 25 ga. sheet metal angle into adhesive. Attach drywall by screwing into the metal corner angle. Nail into intersecting stud. Attach drywall by screwing into the metal corner angle.
Stem or Partition Walls
Partition walls can be adhesively or mechanically (screwed) to the InSoFast panels stud.
Attaching a stud wall to the concrete base wall through the InSoFast panel with a long TAPCON Fastener.
*Please note that although this is a video about installing drywall in a shipping container the metal corner utility angle will work for this application too.
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- Use a metal corner angle (3" x 3", 25ga sheet metal) to wrap outside corners. Generally available in the roofing/flashing section of home improvement stores or drywall supply yards.
- Place beads of adhesive on the back side of the metal angle and press it against the corner. If necessary, hold the angle in place with duct tape.
- Hang drywall by screwing all-purpose drywall screws into the InSoFast studs and into the sheet metal corner angle. Install a second metal corner angle over the drywall using all-purpose drywall screws.
Place a bead of adhesive approximately 1" from each side of the corner. Press 2" x 2" - 25 ga. sheet metal angle into adhesive. Attach drywall by screwing into the metal corner angle. Nail into intersecting stud. Attach drywall by screwing into the metal corner angle.
Stem or Partition Walls
Partition walls can be adhesively or mechanically (screwed) to the InSoFast panels stud.
Attaching a stud wall to the concrete base wall through the InSoFast panel with a long TAPCON Fastener.
Mounting heavy items, such as cabinets, shelving, or a mounting bracket for a flat screen TV, to an InSoFast wall is easy. With a conventional framed wall it is impossible to mount something heavy, like cabinets, between the framing members. With InSoFast panels, heavy objects can be fastened anywhere on the wall. Simply screw to the attachment studs of the InSoFast panel using cabinet screws or fasteners for wood.
Alternatively the drywall is backed solid with the rigid foam of the InSoFast panel, there is no need to locate a "stud" when fastening through the foam directly into the concrete which serves as a continuous solid structural backing behind the entire wall. Use standard concrete screws or anchors of proper size and capacity.
Taping and finishing the drywall and trim to the InSoFast walls.
Attaching the trim using nails.
Our studs are 16” on center that is the most secure way to fasten the trim. A trick that a finish carpenter would use is “X” nailing the trim at a sharp angle in 2 different directions. This way the trim would be held in position by opposing nails.
Attaching the trim using drywall compound as an adhesive.
A plasterer by trade and would prefer the no nail method by using drywall compound to adhere the trim to the wall. That stuff sticks to everything. The bonus with this method it eliminates the need for caulking and filling the nail holes with wood putty.
Apply of 1/2" bead of drywall compound to the backside of the PVC trim.
Roll the trim up and into place gently squeeze out the extra drywall compound.
Tool off excess compound with your finger let the compound cure then with a damp sponge wipe off , then let it dry before painting.
Basically InSoFast is insulation and framing so there are very few limits to what you can use to cover and finish your project. If you can attach it to wood or steel framing you can attach it to InSoFast. Have fun and send us pictures.
Important: InSoFast panels are manufactured using a flame retardant foam and are classified as rigid foam plastic insulation. They fall into the same class as pink, blue and yellow insulation boards which are required by code to be covered by ½” drywall or any other approved 15-minute thermal barrier (IBC 2603.4). If choosing an alternative to drywall it is important to check with your local building code official to make sure it meets your local requirements.
Nail Guns
Nail guns work well into the InSoFast stud. Always test your settings into scrap finish material and the stud before beginning on your wall. The stud is made of plastic make sure it is 55 degrees or above so not to crack the plastic when setting the nails.
This picture demonstrates the variety of fasteners that will work with the stud and not crack or split for a secure and positive attachment for the finishes.
There are numerous types of finishes that are designed for or can applied in moist basement environments. The following is a short list of examples and links to more information.
- Hardie Panels are decorative fiber cement boards that come in a variety of colors and textures.
- Magnesium Oxide (MgO) Board, a technologically advanced board with several superior features including mold-resistance and waterproofing.
- DensArmor Fiberglass Panels, a high performance gypsum panel wrapped in fiberglass for exceptional mold-resistance.
- Southern Wood Specialities offers kiln dried rough cut yellow pine ideal for rustic great rooms, “man caves”, game rooms, and cabins.
3. Other installation questions floors, ceilings, bowed walls, framed walls and other conditions.
Optional Floor Prep and Vapor Barriers
In older homes it is good practice to apply a concrete sealer to block moisture or install a vapor barrier on the concrete floor prior to installing the InSoFast panels.
If you have new construction with a vapor barrier already installed underneath the concrete slab, it is not necessary to put another vapor barrier on top of the concrete floor.
Using InSoFast on Both Walls and Floors
Install the InSoFast panels on the wall first. This minimizes the chance of water getting on top of the subflooring in the event the wall leaks.
Installation Methods
There are four basic installation methods: floating, glue down, screwed down, and fully adhered. The floating method is recommended for carpet, laminate, and wood floors. This is a simpler, quicker installation that makes the concrete floor feel softer and more comfortable. The glue down method can be used for carpet, laminate, and wood floors. The screw down method can be used for any flooring type. The fully adhered method is recommended for tiled area to create a solid base that eliminates movement.
- Floating Installation
- The floating method places the panels directly on the concrete without any adhesive. Interlock the panels together with the tongue and grooved edges in a running bond or staggered pattern.
- Glue Down Installation
- The glue down method bonds the panels in place with a 3/8" bead of PL Premium 3X Stronger Construction Adhesive along dove-tailed ribbing of each stud. One 28 oz. tube covers 50 s.f.
- Screw Down Installation
- Attach InSoFast panels to the concrete floor by installing concrete screws through the studs.
- Fully Adhered Installation
- For tile applications, the InSoFast panels are set in a bed of compatible thinset tile adhesive with a notched trowel as per manufacturer’s instructions.
Interior Partition Walls
Install InSoFast panels up to existing interior partition walls. Non-bearing interior partition walls can be framed directly on top of the subfloor or the InSoFast panel eliminating the need for a chemically treated bottom plate.
Installing Subflooring
Install subflooring with a gap for expansion following per manufacturer’s instructions. Fasten with standard coarse thread all-purpose construction screws. Heavier subfloor panels you may need to predrill a countersink hole. A pilot hole to allow for the screw to be countersunk a flat-head screw to seat flush with the work surface.
Alternatively higher quality speciality fasteners for cement board applications can also be used saving a labor step when countersinking screws into the InSoFast stud.
When panels are installed as a floating floor, it is important to layout the subflooring so that the long seam of the plywood does not line up with the seams in the InSoFast panels. The short seams of the plywood should land over the top of a stud.
Uneven Floors
Prior to installing panels, the low spots can be filled in with concrete patch or concrete floor leveler.
If you notice an area with excessive deflection after the subflooring has been installed, fill the void with adhesive or spray foam. Simply drill a hole through the subflooring and panel down to the void and inject PL Premium Construction Adhesive 3X or gap and crack spray foam. Using too much spray foam will cause a bulge in the floor. Avoid walking on this area until the adhesive or spray foam has set.
InSoFast panels provide a simple, easy way to insulate cold concrete floors. The attachment studs provide a secure surface to screw the subfloor.
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The Top 5 Things to Consider
- InSoFast panels alone can raise the floor by 2 - 2½ inches which will affect any existing door swings as well as the floor-to-ceiling height.
- A subflooring layer of at least ½-inch will be required overtop the InSoFast panels.
- Code requires staircase steps to be all the same height to prevent tripping hazards. Measure your final heights accordingly.
- Water seeks the lowest point in your home. In basement flooring applications, always make sure you have a working sump pump or backflow prevention system to keep sewage from getting trapped in places you don't want.
- Double check your local building codes to determine the allowable live load for construction. See the next section on calculating loads for more information
Calculating Loads
You will need to determine what loading (weight per square foot) is acceptable for your local building codes.
For the most part, live load and dead load values for floor systems are considered "distributed loads." The total weight is distributed or shared uniformly by the members in the floor system. InSoFast panels are uniform because they have 100% contact with the concrete and subflooring.
Our product testing determined that InSoFast panels can support 13 lbs per square inch of compressive resistance at 10% strain deformation. This equates to 1872 lbs per square foot for the design load, well within most residential construction specifications.
Table 3.4 is taken from the U.S. Department of Housing and Urban Development Office of Policy Development and Research's
Printable Guides
| Floor Installation Guide | |||
| Residential Structural Design Guide: 2nd Edition, depicting live load totals for residential construction. |
When install InSoFast panels in a ceiling application the goal is to provide as much contact between the studs and ceilings surface in order to maximize the holding power of the studs.
On the back of the panel, run a 3/8” bead of adhesive along dove-tailed ribbing of each stud. Add a bead of PL Premium 3x along the edge of the panel that will come in contact with the wall. The outer edge or where the first row of panels is placed.
One option is to install the wall panels before the ceiling panels just 2" short of the top. This allows the ceiling panels to slip in between and sit on top of the wall panels around the perimeter add shims to firmly support the edge of the panel until the adhesive sets..
The running bond pattern in not always required on the ceiling but is it recommended for a flatter truer job. Brace the panels firmly until all adhesives has cured. A common, “T” brace is often used. Alternatively a concrete fastener can be used to support the panels and eliminate the bracing requirement.
Mechanical Attachment
Install mechanical fasteners 12" o.c. (six per panel) into the recessed attachment points on the InSoFast stud.
Drywall Installation
Drywall is installed over InSoFast panels in the same way as traditional wood framing. Attach drywall to the InSoFast studs using standard coarse thread all-purpose drywall screws. The InSoFast panel provides solid backing for drywall around the perimeter. The ceiling drywall is locked in place when the drywall is applied to the walls.
As with all foam insulation products, a 15 minute thermal barrier, such as 1/2" drywall, is required.
Adhesive/Mechanical Attachment
Apply a 3/8" bead of PL Premium 3X Construction Adhesive on the backside of the studs which have the ribbed surfaces. Apply an additional bead of adhesive to the foam along any cuts.
Panels are mechanically locked in place when the adhesive sets in the hundreds of interlocking dovetails on the back of the stud.
Install one a mechanical fastener in the recessed attachment point per panel to hold in place until the adhesive has set.
Third party testing shows the ultimate strength of a single bead of adhesive is over 800 pounds per foot which is equal to concrete screws 6" o.c. However, it is up to your local building code official to determine if additional mechanical attachment is required. See product testing for more information.
PL Premium 3X Stronger Construction Adhesive is the only recommended adhesive for adhering the InSoFast panels. Other formulas and brands may not work as expected. One 28 oz. tube covers 50 s.f.
Details and Printable Instructions
| Ceiling Application, Hollow Core Plank | dxf | |
| InSoFast Ceiling Installation Instruction | ||
| ITW-Tapcon-Masonry-Fastening |
InSoFast Plus Method
Need a higher R-value? It’s easy to increase your R-Value beyond R-10 while maintaining the engineered benefits of the continuous InSoFast panels. Simply layer rigid foam insulation board over top of InSoFast panels, InSoFast PLUS. This saves money by utilizing locally obtained rigid foam to enhance the R-Value. Additionally, projects can be completed in a fraction of the amount of time because they start with a base of feature-rich, low-labor InSoFast panels.
Added R-Value with InSoFast PLUS
You can use any panel UX 2.0, or EX 2.5 panels to develop an InSoFast PLUS for a complete R-Value wall assembly - giving you the ability to go from R-8.5 to R-21+.
| PLUS System** | UX 2.0 PLUS (Complete assembly*) | EX 2.5 PLUS (Complete assembly*) |
| InSoFast PLUS ½” Rigid Foam @ R-2.5 | R-11.0 (R-13.58) | R-12.5 (R-15.08) |
| InSoFast PLUS ¾” Rigid Foam @ R-3.75 | R-12.25 (R-14.83) | R-13.75 (R-16.33) |
| InSoFast PLUS 1″ Rigid Foam @ R-5.0 | R-13.5 (R-16.08) | R-15.0 (R-17.58) |
| InSoFast PLUS 1½” Rigid Foam @ R-7.5 | R-16.0 (R-18.58) | R-17.5 (R-20.08) |
| InSoFast PLUS 2″ Rigid Foam @ R-10 | R-18.5 (R-21.08) | R-20.0 (R-22.58) |
Why is works so well to meet R-Value requirements.
- Embedded studs provide a continuous insulation (CI) barrier, eliminating thermal bridging.
- Add any amount of rigid foam over the InSoFast base panels to achieve any desired R-Value.
- Solid attachment can be achieved simply with adhesives. If preferred, they can be drilled or nailed.
- Interlocking panels bridge over wall deviations to help level and plumb the wall.
- Ventilated air channels control over moisture that can enter exposed masonry to allow for quicker drying.
- Pre-engineered electrical raceways enable the insulation shield to stay complete and intact.
- It is insulation framing in a one step process that has the building science built-in.
Find your local State R-Value Code Requirements
Increasing R-Values by adding Insulation
The pictured assembly above achieves an R-17 wall in a shipping container.
Three compliance paths towards energy efficiency:
Building Codes (IRC, IBC, IFC…) are primarily prescriptive in nature, the energy codes are geared more towards performance and effectiveness. To address these difference Code writing bodies have created 3 means of complying with the newer energy codes:
- Prescriptive – you follow the code to the letter (no energy trade-offs – i.e. better windows thicker roof insulation doesn’t mean you can skimp somewhere else)
- Performance – insulation trade off option – i.e. architect uses ResCheck to show compliance (for example exterior continuous insulation in favor of adding more insulation for the roof.) InSoFast believes that with containers a balanced approach to all exterior surfaces. (i.e. refrigerator roof is not thicker than the walls.)
- The HERS Path- where one has to meet or be less than a target HERS score where you can use higher efficient appliances to comply (Only available in newer codes 2015 / 2018 )
InSoFast PLUS in Action
At an award-winning project in North Dakota, the developer wanted additional insulation without sacrificing interior space. They chose InSoFast to be directly install onto the masonry wall with an additional 1" rigid insulation board placed on top to increase the R-Value to meet the local energy code requirements. It was a labor-saver for this fast track retrofit project.
The InSoFast panels were installed first so the studs would be securely fastened to the concrete substrate. The 1" rigid foam was installed over top with the InSoFast stud locations marked on the floor and ceiling prior to adding the drywall. To attach the drywall, they used all-purpose 2" drywall screws to penetrate through the drywall and rigid foam into the InSoFast studs.
Importance of Continuous Insulation
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard 90.1 defines continuous insulation (CI) as insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.
In cavity insulation systems, traditional stud framing can account for at least 25% of wall space. When the studs are uninsulated, there is enough thermal bridging to drop the R-Value from 19 to 12.5 - nearly a 35% loss, which can render any additional layers of insulation useless.
Building codes have higher requirements for cavity insulation to make up for the uninsulated studs or framing members. That is why basement wall code reads 10/13 in many climate zones. It can be R-10 continuous insulated sheathing on the interior or exterior of the home or R-13 cavity insulation along the interior of the basement wall.
Changing Energy Codes
New building codes are increasing R-Values minimums every 3-5 years so that new houses are will not be obsolete or un-affordable 30 years from now due to escalating energy prices. The projected codes for 2030 demand R-Values up to R-30 and the push toward net-zero housing is becoming a reality. While these codes are well-intentioned, they don't always figure a return on investment into the calculation.
To prepare for rising costs and changing energy environments, you may need to exceed your current local energy codes. See the links at the bottom of this page for information on Climate Zones and changes to the International Energy Conservation Codes (IECC).
Related Information
- InSoFast Panel R-Value Report, Stork Twin City Testing
- Find your local State R-Value Code Requirements
- Chapter 4 Section 402 Building Thermal Envelop 2015 IECC requirements
- Chapter 4 Section 402 Building Thermal Envelop 2018 IECC requirements
- An InSoFast PLUS Project receives the ABC's Award for Excellence in Construction
- Temperature Dependence of R-values
“Just because you can, doesn’t mean you should!”
Rubble Stone Wall
It is important to inspect the walls you want to cover before you order InSoFast. InSoFast panels are not suitable for every project. It is up to you to decide if you have the skills necessary to tackle leveling a wall using these advanced techniques. A wall must be repaired and stabilized structurally. InSoFast panels are designed to be applied to structurally sound walls.
1. Begin with a Dry Stack
Dry stack your wall with InSoFast panels. Whether you are working in a basement or a shipping container projects the goal and methods are similar. The goal is to mimic the intended final installation but without physically attaching the panels. Once the walls are set up, one option is to shim the panels using 4" deck or drywall screws and a straight edge. Screw through the panel's stud until the screw comes in contact with solid wall. Then, slowly continue screwing so that the panels are ratcheted outward and become plumb or vertically even with your straight edge.
At this point, the unique position of each panel and its screw shims is critical. They need to be placed in these exact positions again during the final installation. So mark number or label your panels this will aid you in reconstructing your wall later.
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Walls are rarely as level as you'd hope they are. Contractors installing InSoFast against the extremely uneven stone wall pictured below used spray foam to attach the panels.
Temporary wood braces.
2. Carve out the back of the panel to fit. It is easier than chiseling concrete.
3. Liquid Shim with spray foam.
The set screws serve as a guide for the amount and type of adhesive you will apply during the actual installation. Determine a method for deconstructing the walls. We find that simply removing the panels in reverse order is most beneficial to the workflow.
Where the set screw protrudes less than ⅜" from the back of the panel, apply PL Premium 3X Stronger adhesive to the dovetailed stud. PL Premium adhesive is designed to be able to span gaps this size and smaller.
Where the set screw protrudes more than ⅜" from the back of the panel, apply a generous bead of spray foam adhesive. The spray foam adhesive is only used in areas that have a gap of ⅜" up to a maximum of 1". Beyond that, the volume of spray foam needed may be cost-prohibitive.
4. Straight Walls Brace the walls. Until the glues sets.
Allow at least 24 hours for the adhesives to cure before finishing with drywall. The design of the InSoFast UX's tightly interlocking edges helps maintain a plumb finish.
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While the spray foam cured, they held the panels in place with temporary 2x4s. The interlocks that connect each panel create a self-leveling structure in the finished walls.
Note: EX 2.5 panels are designed with a tighter interlock than the UX 2.0 panels, which greatly aids the plumbness of a finished wall. For this reason, we recommend opting for EX panels when faced with highly uneven walls.
Long and boring technical video
Printable Guide
Rim Joists can Leak more than Windows
For many homes, the rim joist is one of the major sources of heat loss and air infiltration. The rim joist area above the foundation can cause more air leakage into the home than all the windows combined. The DIY project of sealing the rim joist is one of the best things that can be done to make the home more energy efficient. It is important to also seal and insulate the top of the concrete wall where the sill plate sits. It's the simplest and least expensive basement area to insulate, and will bring the highest return on your investment.
Rim Joists let in more than Air
Spiders, bugs, and even mice find the rim joist an attractive place to enter the home. The wooden rim or band joist area is where the house's wooden structure rests on the concrete foundation. This area is notorious for gaps and cracks.
Health Issues can Start in the Basement
A house breathes from the basement up. Typically three quarters of the air infiltration comes from the basement. The air entering or exiting the rim joist area can contain high levels of moisture, increasing the likelihood of mold growth and rot in this area. So if there are mold problems in the basement, this can affect the air quality throughout the house.
Caution: After sealing your rim joist area and eliminating air infiltration into the basement, it is important to check the combustion appliances for proper makeup air. Make sure that the appliances are not back drafting to prevent carbon monoxide poisoning.
Building Codes Related to Rim Joist Installation
If you are not planning on finishing the basement or drywalling the ceiling, building codes require that all exposed rigid foam products and spray foam products be covered with a 15 minute thermal barrier, unless it has a fire rating such as Thermax fire rated insulation board. The 15 minute thermal barrier can be achieved by covering with 1-1/2" mineral fiber or ½" drywall glued to the foam board. Check with the local building official.
How To: Seal and Insulate Using Rigid Foam Board Insulation
A do-it-yourself friendly method for sealing and insulating the rim joist or band joist area is to use rigid foam up against the rim joist. This method can be hundreds of dollar less than the cost of using the commercially applied spray foam. Just cut the foam board slightly smaller than the area to be sealed and finish up with expanding spray foam. This is an effective method for air sealing this area while still being easy on the pocket book.
In cold, humid, or mixed climates, the foam board thickness needs to be 2" thick to stop the condensation in the rim joist area. If the foam board is properly sealed, additional fiberglass insulation can be added to obtain a higher r-value. Because the air infiltration has been stopped, the fiberglass should not have mold problems. More moderate climates may use 1" foam board, but please check with the local building official.
Installation Tips
Rigid foam board is easily cut with a long snap off blade utility knife. Figure on leaving a gap of ¼" - ½" all the way around. Make sure to taper the cut around the edges so that there is plenty of room to get the expanding foam around the edges. Dry fit the rigid foam board pieces.
Prior to placing the foam board in place, run a bead of expanding foam along the bottom of the rim joist cavity. Place the foam board against the rim joist and seal around the remaining edges with the spray foam. If there are problems with the board staying in place, a bead of foam board adhesive can be placed on the back side of the panel. Make sure to seal around any pipes or other penetrations with the expanding foam to provide an air seal.
Use caution with the expanding spray foam. It is impossible to remove from your hands or clothing. Use protective eyewear. If you are using the spray foam with the straw applicator, you may find it helpful to attach flexible vinyl tubing as an extension over the straw. Since the can has to be upside down to maintain flow, this makes working in the rim joist area easier.
It is best practice to install InSoFast panels right up to beginning of a rim joist and fully seal the remaining space according to its receding geometry. You can use scrap panels of InSoFast to fill in these spaces and seal any other gaps with spray foam.
How To: Seal and Insulate Using Spray Foam Insulation
How Spray Foam Works
Commercially applied spray foam is considered to be the best way to seal the rim joist area. The spray foam easily fills in and seals all the cracks and openings in the rim joist or band joist area. It is generally installed by a professional insulation contractor with the necessary mixing equipment.
The polyurethane spray foam is a two-part compound. Part A is isocyanate and a mixture of polyols and additives and Part B is the catalysts. The chemicals are heated and mixed at the job site as the foam is sprayed from a high-pressure gun.
Health and Safety Concerns
While spray foam is a great product, there can be some major concerns. An improperly installed spray foam job can result from not following the manufacturer's recommendations, including the mixing temperature, applying too thick of a layer, and not following proper ventilation practices.
It is important to note when dealing with chemical off-gassing of a two part spray foam system, all occupants must vacate the building or wear proper ventilation. According to manufacturers, the ingredients are harmful at the time of application, but when cured properly it is an inert material that should not have any dangerous off-gassing.
Do not exceed 2" of thickness in a single pass. If the spray foam is applied in a thicker layer, the chemicals may fail to cure properly and may continue to off-gas into the home.
Keeping Spray Foam Affordable
There are two way to reduce material costs. First install a layer of rigid foam insulation and cover over and seal with spray foam. Another option is to apply a 2" layer of spray foam followed with fiberglass insulation. The spray foam provides the necessary air barrier while eliminating condensation and the fiberglass boosts the insulation value.
Do-it-yourself spray foam kits can be purchased. Extreme care must be taken with spray foam. A respirator, full body suit, gloves, and eye protection are required.
Avoid Fiberglass Insulation
Fiberglass Doesn't Meet Current Codes for Rim Joist Insulation
Insulating the rim joist or band joist area with fiberglass insulation is no longer recommended by building professionals and does not meet current building codes for air sealing.
Because fiberglass easily allows air to travel through, it is a very poor choice for insulating the drafty rim joist area. It is almost impossible to get a proper air seal in this tight space. The recommendation is that fiberglass insulation be removed from the rim joist area and replaced with a more effective insulation and vapor barrier system.
More Fiberglass Equals More Mold
One of the main problems with fiberglass insulation is that it does not restrict air flow. Without a vapor barrier at the rim space, there is relatively warm, moist air passing through the fiberglass insulation, hitting cooler air, and then condensing at the rim joist.
Over time the fiberglass filters out the dust traveling through. When moisture is added, mold can spread throughout the fiberglass and spread to the wood due to the lack of vapor barrier. This condition is often worsened by adding more fiberglass insulation which almost ensures that the area will not dry out.