FUNDAMENTALS OF SPF FOR THE INDEPENDENT BUILDING ENVELOPE INSPECTOR CHAPTER 2 DESIGN, APPLICATION AND WORKMANSHIP FOR THE BUILDING ENVELOPE

Transcription

1 FUNDAMENTALS OF SPF FOR THE INDEPENDENT BUILDING ENVELOPE INSPECTOR CHAPTER 2 DESIGN, APPLICATION AND WORKMANSHIP FOR THE BUILDING ENVELOPE

2 CONTENTS PAGE INTRODUCTION... 3 SPRAY POLYURETHANE FOAM IN THE BUILDING ENVELOPE... 3 DESIGN CONSIDERATIONS... 3 GENERAL CONSIDERATIONS... 3 DETERMINING INSULATION THICKNESS... 3 SELECTION OF PRIMER... 4 SELECTION OF A VAPOR RETARDER... 4 SELECTION OF THE SPRAY POLYURETHANE FOAM SYSTEM... 5 SELECTION OF A THERMAL BARRIER... 5 APPLICATION AND WORKMANSHIP... 5 APPLICATION OF PRODUCTS... 5 SUBSTRATE CONSIDERATION AND PREPARATION... 6 PRIMER APPLICATION... 6 MASKING... 7 APPLICATION OF INTERIOR POLYURETHANE FOAM... 8 CLEAN UP... 9 DETAIL DRAWINGS SUMMARY These course materials have been prepared and reviewed by the SPFA Accreditation Committee and accepted for use in connection with the SPFA Spray Polyurethane Foam Accreditation Program on the basis of established industry criteria. The course materials are offered for educational and training purposes only and without any representation or warranty, express or implied, by SPFA as to the quality of performance of the products used or services rendered by an individual or company completing the training program. SPFA and its members specifically disclaim any and all liability for any losses, damages, injuries or damages to persons or property arising out of or resulting from the use or reliance upon these course materials by any party. SPFA neither endorses nor guarantees the proprietary products or services of any particular company or individual that may be mentioned or featured in these materials. Spray Polyurethane Foam Alliance 4400 Fair Lakes Court, Suite 105 Fairfax, VA

3 INTRODUCTION In this chapter we will discuss the use of polyurethane foam in the Building Envelope. We will start off with design considerations. Since polyurethane foam can be used in a wide variety of applications, it can perform varied functions such as air and moisture control, structural reinforcement, and thermal insulation. The application and workmanship section will address substrate considerations and preparation, primers, vapor retarders, masking, application techniques, details and clean up. SPRAY POLYURETHANE FOAM IN THE BUILDING ENVELOPE The physical properties of SPF allow it to perform multiple functions (control of heat, air and moisture) within building assemblies and ancillary equipment. SPF becomes the preferred material of choice for insulating homes, commercial buildings, roofs, storage tanks, cold storage facilities, ducts, pipes and more. SPF can provide a complete, seamless building envelope creating a more comfortable indoor environment for the life of the structure. It seals cracks and seams giving added protection. SPF can form a seamless bond with building components to create a structurally sound, uniform, air infiltration barrier system. Its superior thermal properties perform in even the most extreme hot or cold climates. DESIGN CONSIDERATIONS GENERAL CONSIDERATIONS The performance of a spray applied polyurethane foam insulation system can be affected by all the component parts of a structure, as well as the atmospheric conditions inside and outside the structure. Structural design, specification review, contractor and material selection, coupled with the compatibility and positioning of the various structural components are necessary to produce a successful building envelope insulation system. Spray polyurethane foam can be successfully applied to most surfaces. However, the following practices should be observed. DETERMINING INSULATION THICKNESS The following method should be considered when determining insulation thickness: SPFA 3

4 1. Building and Energy Codes: Most code agencies require certain buildings to meet the energy conservation standards prescribed by the Model Energy Code (MEC), and more recently, the International Energy Code (IECC). See Chapter 2 for R-value requirements by climate zone. 2. Condensation Control: Condensation can occur inside a building envelope when the surface temperature of any component is lower than the dew point of the air that it contacts. Increased foam thickness and/or or the use of vapor retarders (over moisture-permeable insulations) are used to control this condensation. These materials must be selected based on the design dew point and the design exterior and interior temperature and humidity. In cold climates, a good rule-of-thumb is to apply enough insulation so that the inside surface of the vapor retarder material is never exposed to temperatures below about 45ºF. 3. Economic Thickness: Greater insulation thickness decreases heat and cooling costs and the cost of HVAC equipment. However, there is a diminishing return to adding thickness where the time weighted cost of additional insulation exceeds the expected energy savings. The economic thickness calculation determines the added incremental insulation thickness, which meets a specified return on investment from projected energy cost savings. Economic insulation thickness is discussed in Chapter Minimum Application Thickness: Spray polyurethane foam applications must be sprayed to a minimum thickness to conform to the substrate and to achieve proper foam cure. For most relatively smooth substrates the minimum practical thickness is one inch but corrugated or unusual substrate configurations may require greater thickness. For the purposes of achieving an air barrier, ½ thickness may suffice but at this thickness, spray foam will not perform as a vapor retarder. The best method to determine insulation thickness would be to determine the required thickness for each of the situations described above and choosing the one with the largest thickness. SELECTION OF PRIMER If a primer is required, it should be considered in accordance to the type of substrate to be sprayed, the intended end use of the wall assembly and the spray polyurethane foam and/or primer manufacturer. SELECTION OF A VAPOR RETARDER If a vapor retarder is required, its selection should be based on the following criteria: SPFA 4

5 1. Perm rating required (based on moisture vapor drive and perm ratings of other components). 2. Compatibility with adjoining materials. 3. Manufacturer s recommendation. SELECTION OF THE SPRAY POLYURETHANE FOAM SYSTEM The contractor, in the case of spray polyurethane foam applications, fabricates the product on site in accordance with manufacturer s instructions. The wide range of spray polyurethane foam systems are available in various densities, each exhibiting different temperature limitations, combustibility characteristics, etc. The use of these systems, in combination with each other or with other insulation products, offers a wide range of economical installations. From a fire safety standpoint, spray polyurethane foam can be used safely. It is important, however, that all persons associated with the design, fabrication, storage and installation must understand the materials and environments involved. There should be no open flames or welding torch use near unprotected foam. Polyurethane foam insulation is combustible and should be treated as such. Flame spread ratings provided for polyurethane products using small scale tests are not intended to reflect the hazards presented by this or any other materials under actual fire conditions. To avoid ignition and combustion, SPF must never be subjected to heat sources above F. In addition, to avoid degradation of the foam, ensure it is not exposed to continuous operating temperatures in excess of F. SELECTION OF A THERMAL BARRIER When polyurethane foam is spray applied to interior surfaces, it must be protected by a thermal barrier. (Refer to SPFA Guideline AY 126 and See Section 9 on Thermal Barriers.) APPLICATION AND WORKMANSHIP APPLICATION OF PRODUCTS The products intended for use in the building envelope insulation system must be applied within the manufacturer s guidelines for temperature, humidity, and other atmospheric conditions. In addition, they must be sequenced so as to take into consideration substrate preparation, proper cure times, and adhesion between passes. SPFA 5

6 SUBSTRATE CONSIDERATION AND PREPARATION Surface preparation guidelines for those substrates that are to be insulated and statements regarding the selection of materials related to the successful performance of the spray polyurethane foam insulation are outlined below. 1. Wood a. Wood substrates, including plywood, OSB and dimensional lumber, shall contain no more than 18% water, as measured in accordance with ASTM D-4449 and D b. Most untreated and unpainted wood surfaces need not be primed. Spray polyurethane foam can be applied directly to the dry wood. Priming may be beneficial in certain instances. See the spray polyurethane foam manufacturer for specific details. 2. Steel a. Primed: If the primed metal surface is free of loose scale, rust, weathered or chalking paint, it can be prepared using vacuum equipment, hand or power tools to remove loose dirt. Grease, oil or other surface contaminants can be cleaned using a power wash technique. b. Previously Painted: Clean the painted metal surface using hand or power tools to remove loose scale and dirt. Grease, oil or other surface contaminants can be cleaned using a power wash technique. c. Galvanized: When required, clean galvanized steel as recommended by the primer manufacturer. d. Unpainted Steel: Clean as recommended by primer manufacturer in order to prepare the steel surface for the primer. 3. Concrete and Masonry Concrete must be cured sufficiently (typically 28 days) so that no surface moisture is present. Loose dirt and any other contaminants must be removed. 4. Sheathing Board Most sheathing boards need not be primed prior to the application of sprayed in place polyurethane foam. 5. Primer / Vapor Retarder Preparation Prior to application of primer, vapor retarder or spray polyurethane foam, the surface must be cured, dry and free of loose dirt or any contaminants that may interfere with adhesion of any of the respective components.. PRIMER APPLICATION Generally, interior applications don t require a primer. (See manufacturer s specific instructions) Materials that should be primed include glass, aluminum, galvanized metal and some pre-finished metals. SPF generally adheres well to SPFA 6

7 dry wood, brick, concrete and other porous substrates. However, if you have any concerns about adhesion to the substrate, priming is a good practice. When required, the primer shall be applied to the prepared substrate in accordance with the manufacturer s guidelines. The primer shall be allowed to cure prior to application of spray polyurethane foam or other products. Substrate primers (if required): The primer to be applied must be specifically selected for the given substrate to be primed and must be compatible with the spray polyurethane foam formulation selected. Examples include the following: 1. Wood: Chlorinated rubber, modified alkyds, others. 2. Steel: Modified alkyds, epoxy, acrylics, others. 3. Galvanized: Vinyl copolymer, wash primer, modified alkyds, others. MASKING Masking, as it pertains to our industry, refers to the covering or protection of substrates and fixtures that should not be over-sprayed during the application of SPF. Typical masking materials would include masking tape, duct tape, masking paper, polyethylene film (Visqueen or poly ) as well as red rosin paper. Generally, correct masking only requires a little common sense. If you don t want to clean it after, cover it before! When spraying ceilings, interior finished walls should be covered. Avoid situations where SPF will substantially cover the tape, resulting in cutting or sawing to remove the masking tape). Always cover windows and fixtures. Electrical outlet boxes should also be covered. Floors should be covered during wall or ceiling applications. During wall applications, a strip of red rosin paper will lay flat and straight against the base plate. One handy tool is the painter s masking tape dispenser: a simple hand held tool which combines a roll of masking tape and a roll of masking paper with a cut off blade, allowing you to pull a pre-taped length of paper off and cut to fit. Masking is a key preparation step. Cover the openings of all electrical boxes, including electrical switch and receptacle boxes, telephone boxes, stereo connections, cable TV, etc. Do not mask openings to the exterior of the building as they must be in contact with spray applied polyurethane foam to create a proper air seal. Be sure to mark each masked unit with a protruding stick or wire end so that you can locate it once the areas has been sprayed. Cover window openings with polyfilm or other protective material. This will prevent spray polyurethane foam over spray and reduce cleanup time. Mask beyond window casing to the rough framing AFTER this opening is insulated and airsealed. SPFA 7

8 Polyethylene can be secured with tape, or if the surface isn t critical, staples or spray adhesive. There is also a product called liquid mask which can be brush roller or spray applied and can be peeled off. Some surfaces and stud faces can be greased or sprayed with a light oil to facilitate clean up. Also, always remember to cover other trades equipment and tools. A good rule of thumb is if it does not get sprayed, cover it. Another important consideration is to close the building down to other trades during application of spray foam. Work closely with the construction manager to integrate this into the construction schedule. APPLICATION OF INTERIOR POLYURETHANE FOAM Before starting to spray, make sure that all electric, plumbing and HVAC inspections have been performed and that all hot work (welding, cutting, torch work) is complete. Closed-cell SPF is typically applied in pass thicknesses of ½ to 1½ inches to achieve the desired physical properties (less than ½ inches may not heat up sufficiently to fully react and cure; greater than 1½ inches may generate too much heat and char). Always follow the manufacturer s recommendations for minimum and maximum pass thickness. Open-cell SPF may be applied in thicknesses greater than 6 inches per pass. Again, always follow the manufacturer s recommendations for pass thickness limits. When spraying within stud cavities, most foam mechanics picture frame the studs. To do this, spray diagonally at the juncture of the stud and the substrate. Bring the spray edge out on the substrate along the stud about 2/3 of your spray pattern width. This will eliminate voids next to the studs. Also, ensure SPF is applied between the outlet boxes and exterior sheathing. CAUTION: If there is a space or gap between the stud and the exterior substrate, take care not to spray too much foam into the crack. The expanding foam can push out the stud resulting in a bowed wall. Next, spray in the area between the studs to the required thickness. Check your work regularly with a sharp rigid wire probe to ensure that you are applying the correct thickness. Cathedral and flat ceilings are sprayed in the same manner as the walls. If the designer, local code official or shingle manufacturer requires venting, make sure vents or chutes are installed prior to application. If recessed light fixtures are installed, do not spray polyurethane foam directly to the fixture; follow the fixture manufacturer s recommendations for insulating and/or venting the fixture. Some fixture types require that a gypsum board box be built around them prior to spray application. SPFA 8

9 CAUTION: Be careful when spraying near fixtures with small overhead clearances. The expanding foam can force the fixture down requiring unwanted re-work to align the ceiling with the fixture. Ceilings are generally sprayed thicker than walls, so you may want to use multiple applications of the picture-frame technique as you build to full thickness. Do not apply foam within three inches (3 ) of chimney or flues. CLEAN UP Quick and easy clean will result if the job is masked correctly. After removing the application equipment, clean the stud faces and saw or scarf off any SPF that is past the stud face. A hand saw, saber-saw, foam scarfer or curry comb can be utilized. Unmask from top to bottom, removing masking from ceiling or ceiling fixtures, then walls, windows and wall fixtures. After the high work is complete, ladders and scaffolding can be removed. Next, the floor masking can be rolled up with all the debris into a bundle and disposed of. If a covering was not used, the floor should be scraped and swept. CAUTION: Unless the foam scraps have been properly fire tested, they should never be used as filler materials or additional insulation within a building. SPF scraps should be removed from the building and disposed of according to the manufacturer s guidelines and/or federal, state and local regulatory agencies. Use of SPF scraps as a filler or additional insulation could present a fire hazard in some situations, To meet building code requirements, SPF products are fire tested as an installed material or assembly -- a solid block of material with a single, flat, exposed surface. SPF scraps have a much higher ratio of surface area to volume, and may be more combustible than a solid block of foam. Check over the job for any finished surfaces that may have been oversprayed. Overspray can be removed from some surfaces with a solvent rag, razor blade, very fine steel wood or a combination of these. Always leave the site at least as clean as it was when you arrived. SPFA 9

10 DETAIL DRAWINGS FIGURE 5.1a Detail of stud wall with full-foam thickness (Photo courtesy of Building Science Corporation) FIGURE 5.1b Photo of open-cell spray foam installation spraying (L) and shaving (R) (Photo courtesy of Airtight Systems) SPFA 10

11 FIGURE 5.2a Detail of stud wall with partial (2 ) closed-cell foam thickness. (Diagram courtesy of Building Science Corporation, Westford, MA) FIGURE 5.2b Photo of installation 2 closed-cell foam in wall and band joist ((Left photo courtesy of Air Tight Systems; Right photo courtesy of Steve Easley and Associates) SPFA 11

12 FIGURE 5.3a Diagram of stud wall with hybrid insulation (Diagram courtesy of Building Science Corporation) FIGURE 5.3b Photo of installation hybrid insulation: closed-cell foam and cellulose (Photo courtesy of Building Science Corporation) SPFA 12

13 FIGURE 5.4a Diagram of Cathedralized Ceiling: open or closed-cell spray foam (Diagram courtesy of Building Science Corporation) FIGURE 5.4b Photo of installation cathedral ceiling (Photo courtesy of Airtight Systems) SPFA 13

14 FIGURE 5.5a Diagram of Insulated Attic: open or closed-cell spray foam (Diagram courtesy of Building Science Corporation) FIGURE 5.5b Photo of Insulated Attic: open or closed-cell spray foam (Diagram courtesy of Building Science Corporation) SPFA 14

15 FIGURE 5.6a - Diagram of basement wall with interior spray foam insulation (closed-cell) (Diagram courtesy Building Science Corporation) 5.6b - Interior Finished Basement Wall (Photo courtesy Airtight Systems) SPFA 15

16 SUMMARY Building Envelope o Spray polyurethane foam can perform multiple functions in a building envelope, over a wide range of exterior temperatures o Open-cell and closed-cell spray foams provide insulation and can seal against air leakage o Closed-cell foams can also provide an integral code-approved vapor retarder and can improve structural strength of the building. Design Considerations o Before application, always consider the following when determining insulation application thickness: Applicable building and energy codes, condensation control, economic (cost-effective) thickness, manufacturer s recommendations/limitations, o The need for primers and vapor retarders must be considered before application. o Fire protection during installation is important to protect the safety of all on the jobsite. o Fire protection after installation, including thermal and ignition barriers, is equally important to protect occupants. Application and Workmanship o Substrate surfaces must be prepared in advance to assure adhesion and proper reaction of the foam. o Interior application, especially in new construction, generally does not require a primer. Surfaces in existing homes should be properly evaluated to determine if a primer is needed. o Always mask areas where spray foam should not be applied. This includes windows (or any finished surfaces), stud faces and outlet boxes. o Be sure all electrical and plumbing inspections have been completed before application of SPF. o Picture-framing is a spraying technique used to avoid gaps near the studs. o Cleanup is critical, including removal of any overspray, shaving to facilitate drywall installation, and disposal of all scraps and waste. Detail Drawings o Proper application of SPF is needed to assure performance as an insulation, air-barrier and vapor retarder REV.7/27/11 SPFA 16