To run continuously over structural members, continuous insulation requires certain installation procedures
|Photo courtesy of Johns Manville|
Continuous insulation (CI) is a quick and easy way to improve thermal performance in buildings. Continuous insulation covers entire surfaces, providing R-value where cavity insulation cannot.
CI is normally made possible using rigid foam insulating materials. These materials can be fixed to either the inside or outside of the exterior walls, which has the advantage of being a continuous sheet of insulation rather than needing to have breaks for studs or other wall fittings. “Noncontinuous insulation would be any insulation that is either interrupted by structural or framing members⎯such as fiberglass or mineral wool batts or spray foam⎯or insulation that is compressed over structural members, such as compressed fiberglass blankets in pre-engineered metal buildings,” says Francis “J.R.” Babineau, PE, building scientist,
Johns Manville, Denver.
For those states following ASHRAE 90.1-2007 and IECC 2009, continuous insulation is no longer simply a value-added option⎯it is a requirement. Here’s information on how to install it correctly.
CI Installation Instructions
CI is easier to install than cavity insulation because cutting the insulation to fit in between the walls is unnecessary. Instead, the material can be cut so that it fits tightly together and is then fixed directly to the wall. The wall can then be finished using various techniques.
CI materials vary. Differences in their installation methods and steps come into play depending on where the air barrier and water-resistive barrier are in the overall system, and in how thick the CI is. Sidebar A lists basic steps according to Babineau that apply to almost all board-type CI products (foam or mineral fiber boards) over exterior sheathing. Sidebar B lists basic steps provided by Auburndale, Fla.-based Fi-Foil Co. for its clip-and-pin wall system installation for commercial and industrial facilities.
A common CI installation issue is not correctly integrating the drainage layer either behind the CI or in front of it. “A mistake that can crop up with metal buildings is using continuous Z-channels to attach claddings,” says Babineau. “Z-channels are also metal and end up creating another thermal bridge.”
Bill Lippy, president of Fi-Foil, believes a common installation mistake is when contractors compress the insulation. “This can be prevented by using a non-compressible insulation or stand-offs that separate the metal, or a system to allow the insulation to fall below the purlins,” he says.
|Photo courtesy of Dow Building Solutions|
Installing rigid CI over metal framing isn’t as well-known as other methods of insulation, and Emelie Balmes, commercial market manager for metal buildings, Dow Building Solutions, Midland, Mich., believes there are a few misconceptions her customers have. “First, we often see takeoffs,” she says. “It is important to get the right amount of rigid board square footage to do the job without having to reorder, for example, 10 extra boards, which can be costly to ship.”
Also, while costs for rigid insulation tend to come in slightly higher than fiberglass batts, that changes when incorporating labor costs. Builders often overlook the overall cost of the insulation and installation combined. Balmes says codes are now requiring a liner-faced (non-CI) material that have the batts rolled out and then criss cross over with another layer of batts. “This could be an expensive labor option compared to simply screwing in a rigid insulation over framing and taping the board joints,” she says. “The reality is the cost of installing the rigid insulation is less than criss crossing the batts.”
Tools and Practice
Tools for installing most continuous insulation include scissors, a T-square, a knife long enough to cut the material, a screw gun or impact driver (for going into concrete with fasteners with wide plastic plates), seam tape, high-quality sealant, and possibly a hand-squeegee for smoothing tape joints.
Balmes believes the key to successfully using these tools it to practice setting on a piece of CI board before actually installing it. “The last thing you want to happen is to force the fasteners into the facer of the rigid board and tear the facer,” she says. Babineau agrees that mock-up wall sections are very important so installers can get a chance to practice with and see how CI will integrate with the other layers in the building envelope.
Use caution when working with CI pins, the ends are very sharp. Safety glasses and other applicable safety measures should be used when installing the systems. Refer to standard and local safety requirements. Refer to ASTM C-727, Standard Practice for Installation and Use of Reflective Insulation in Building Constructions, for other installation considerations.
Sidebar: CI Installation Over Exterior Sheathing
Begin installation after structural steel, exterior framing, and bracing and structural sheathing is complete.
• Install Foil-Faced Foam Sheathing horizontally (preferred) over exterior sheathing staggering joints relative to exterior sheathing. The reflective side of the board should be oriented to the exterior, and the non-reflective white side should be oriented to the interior.
• Use maximum board lengths to minimize number of joints. Locate joints square to framing members. Center end joints over framing. Provide additional framing as necessary. Stagger each course at least one stud space to minimize continuous vertical seams.
• Boards may be installed vertically if less seam sealing results.
• Butt board edges together tightly, and carefully fit around openings and penetrations.
• Fasten insulation boards to the exterior face of the stud framing using recommended fasteners with lengths prescribed by manufacturers’ instruction.
• Fasteners must be long enough that at least three full threads are visible inside the wall framing.
• Space fasteners 16 inches on-center at the board perimeter, or consistent with framing spacing, but not greater than 24 inches on-center. Space fasteners 24 inches on-center in the field, or consistent with framing spacing.
• One fastener/plate can bridge between a maximum of two adjoining board edges.
• Drive fasteners so the stress plate is tight and flush with the board surface, but do not countersink.
• Install exterior cladding ties as applicable.
• To create an air/water-resistive barrier, tape all seams, edge and end joints, and thru-wall penetrations with recommended flashing tape.
• Install flashing shingle style with a minimum 4-inch overlap, and follow the tape manufacturer’s application instructions.
• Seal fastener penetrations by applying a minimum 4-inch by 4-inch piece of tape over each plate, smoothing tape edges to create an airtight seal between the tape and the insulation board.
• Create continuous air/water barrier at roof and foundation wall interface using peel-and-stick membrane, or other approved barrier, following manufacturer’s application instructions.
• Seal penetrations and panel defects with recommended sealant in accordance with the manufacturer’s instructions.
• Repair any boards damaged during installation. Patch holes less than 1 inch across with flashing tape.
• Patch holes greater than 1 inch across with matching board material and then seal with flashing tape.
• As applicable, the wall is now ready for stud cavity insulation and exterior veneer.
• Install approved cladding systems as soon as possible, preferably within 60 days.
Installation steps provided by Johns Manville, Denver
Sidebar: Clip-and-Pin Wall System Installation
• Install beam and purlin clips every 18 inches on purlins and side beams.
• Pop a chalk line on the floor of the side wall bay. Install angle clips 12 inches apart with tap cons or install 2- by 4-inch pressure-treated wood to the floor for attaching the bottom of the insulation.
• Run the insulation across the purlins from top to bottom. Attach the insulation at the top and pull taut to the bottom. Line up the insulation edge with the edge of the support beam and secure using clips from the first run of insulation.
• Overlap the second run 2 inches. Use a second washer on the outside clip and pin to attached the adjoining insulation. After all the sections are complete, secure the sides next to the supporting beam.
• Cut to a neat fit around obstructions and at the top and bottom.
• Tape the top seam using Fi-Foil white, black or foil tape. Use tape tab at each seam. Use button-cap nails and washers at seams between side purlins if beams are too far apart for tape to hold sections of insulation together. Use double-sided tape at beams.
Installation steps provided by Fi-Foil Co., Auburndale, Fla.
|Photo courtesy of Dow Building Solutions|