Installation standards and practices
As mentioned in Chap. 7, general work practices applicable to all work involving SVFs such as fiberglass (rock wool and slag wool) have been established by U. S. Occupational Safety and Health Administration (OSHA). Excerpts of the guidelines are as follows11:
1. Minimize dust generation.
■ Keep the material in its packaging as long as practicable and if possible.
■ Tools that generate the least amount of dust should be used. If power tools are to be used, they should be equipped with appropriate dust-collection systems as necessary.
■ Keep work areas clean and free of scrap SVF material.
■ Do not use compressed air for cleanup unless there is no other effective method. If compressed air must be used, proper procedures and control measures must be implemented. Other workers in the immediate area must be removed or similarly protected.
■ Where repair or maintenance of equipment that is either insulated with SVF or covered with settled SVF dust is necessary, clean the equipment first with a HEPA vacuum or equivalent (where possible), or wipe the surface clean with a wet rag to remove excess dust and loose fibers. If compressed air must be used, proper procedures and control measures must be implemented. Other workers in the immediate area must be removed or similarly protected.
■ Avoid unnecessary handling of scrap materials by placing them in waste disposal containers and by keeping equipment as close to working areas as possible that prevents release of fibers.
■ Unless other proper procedures and control measures have been implemented, dust-collection systems should be used in manufacturing and fabrication settings where appropriate and feasible.
■ Exhausted air containing SVFs should be filtered prior to recirculation into interior workspaces.
■ If ventilation systems are used to capture SVFs, they should be checked and maintained regularly.
3. Wear appropriate clothing.
■ Loose-fitting, long-sleeved and long-legged clothing is recommended to prevent irritation. A head cover is also recommended, especially when working with material overhead. Gloves are also recommended. Skin irritation cannot occur if there is no contact with the skin. Do not tape sleeves or pants at wrists or ankles.
■ Remove SVF dust from the work clothes before leaving work to reduce potential for skin irritation.
4. Wear appropriate personal protective equipment.
■ To minimize upper respiratory tract irritation, measures should be taken to control the exposure. Such measures will be dictated by the work environment and may include appropriate respiratory protective equipment. See OSHA’s respiratory protection standard.
■ When appropriate, eye protection should be worn whenever SVF products are being handled.
■ Personal protective equipment should be fitted properly and worn when required.
5. Removal of fibers from the skin and eyes.
■ If fibers accumulate on the skin, do not rub or scratch. Never remove fibers from the skin by blowing with compressed air.
■ If fibers are seen penetrating the skin, they may be removed by applying and then removing adhesive tape so that the fibers adhere to the tape and are pulled out of the skin.
■ SVFs may be deposited in the eye. If this should happen, do not rub the eyes. Flush them with water or eyewash solution (if available). Consult a physician if the irritation persists.
Insulation should be installed just before the interior finish is applied. In addition to the removal of all construction debris from the spaces to be insulated, the following checklist should be completed. (If any part of this work is done following the installation of the insulation, the vapor retarder may be damaged, and gaps may be made in the insulation.)
1. Sidewalls, floors, roofs, and ceilings have been framed.
2. Roofing is finished and doors, windows, subflooring, and sheathing are in place.
3. Plumbing, heating, ventilating, and air-conditioning work has
been completely roughed in.
4. Cabling and wiring (including telephone and other low-voltage
wiring) have been completely roughed in.
Stapling methods. There are three commonly accepted methods of installing faced insulation in wood framing members. These are referred to as inset stapling, face stapling, and pressure fit. (Faced blanket insulations typically provide a stapling flange for attaching the insulation to the framing members; Fig. 8.11.)
It is important to note that wherever batts or rolls of any type are too short to fill a stud cavity, a piece should be cut to size to fill the gap. When insulation is too long, it should be cut to fit properly, not doubled over or compressed. For standard wall heights, use precut batts rather than continuous rolls. This will tend to expedite the installation process. Rolls should be used where length requirements permit. If cutting is necessary, the best knife has been found to be one with a serrated blade. Utility knifes are more common.
It is easiest to cut kraft-faced batts with the paper face down. Cutting from the paper side can rip the paper and ruin its efficiency as a vapor barrier. To cut insulation properly, lay the blanket on a board with the kraft or foil facing down. Place a straight edge or 2 X 4-in piece of lumber over the area of insulation to be cut. Press the straight edge down hard, and cut with the knife. Blades should be replaced periodically because they tend to dull during use.
Inset stapling. When using the inset stapling method, place the insulation in the cavity, and check to be sure that it completely fills the cavity, top to bottom. It is recommended that a single batt be used in sidewalls. However, when insulating with 47- or 48-in batts, make sure the two pieces are butted snugly together. Gently press the insulation at the sides into the framing cavity, usually about 3/4
Figure 8.11 Stapling flange. (NAIMA)
in, until the outside edge of the flange is flush with the face of the framing. When inset stapling insulation between inclined or vertical framing members, as in cathedral ceilings or walls, start stapling at the top and work down. Use enough staples to hold the insulation firmly in place, and avoid gaps and “fishmouths” between flanges and framing12 (Fig. 8.12).
Face stapling. Place the insulation between the framing members, and check to be sure that the blanket fits the cavity at both ends. With facing material flush with the face of the framing, the flanges will overlap the framing. Staple the flanges to the face of the framing using enough staples to hold the insulation firmly in place, and avoid gaps and fishmouths. The flange of the faced insulation placed in the next cavity will overlap the previously stapled flange12 (Fig. 8.13).
Both methods are used widely and can provide acceptable performance. Inset stapling is usually preferred by the wall finish trades because it allows adhesive application of wall board. Another problem occurs when stapling over the face of the framing; the layers of paper can get bunched up. This makes it harder for the gypsum wallboard crew to find places to nail, and often results in more nail pops.
Figure 8.12 Inset stapling. (NAIMA)
Pressure fit. To install faced products by pressure fit, gently place the insulation into the cavity space between the framing members. The insulation facing must be flush with the face of the stud and fit snugly at the sides and ends.12
Unfaced insulation. Many insulation subcontractors prefer unfaced batts for most applications because they are faster to install. Similar to the pressure-fit technique, gently place the insulation into the cavity space between framing members. It is important that insulation be correctly sized for the cavity, and fit snugly at the sides and ends.
Sidewalls. First of all, verify with the local building code all requirements regarding insulation materials, ventilation clearances, and firestops. Make sure that any openings between floors are fire-stopped with fireproof caulk, unfaced fiberglass, or rock wool. Plumbing and wiring chases, flue chases, hearths, and chimneys all need fire stops.
Measure the ceilings and walls to determine the square footage, and divide by the number of square feet in a package. The coverage of each package of insulation varies according to manufacturer, livable, and width. Some installers prefer the 16M-wide batts rather than the typical 15M-wide batts. These wider batts are made for walls framed with metal studs, but when used with wood framing, the extra inch of width makes a good, snug fit between studs.
In order to avoid incidental compression during packaging, it is wise to fluff up the batts, making sure that each is expanded to its full thickness. Running a thin putty knife between the fiberglass and the stud also fluffs and aligns the batt after it is in place. Full – length batts, which are typically cut to 93" for an 8-ft wall, can be used in empty stud bays where there are no electrical or plumbing obstacles.
An all-too-common practice by installers when encountering obstacles within the stud cavity is to omit the insulation, or incorrectly compress the batt. This may be marginally sufficient when the electrical wiring is located close to the inside wall surface. When the wiring is in the center of the cavity, either a shallow cut in the insulation may be used to allow the wiring to pass through the insulation or it may be split lengthwise and the wiring sandwiched within (Figs. 8.14 and 8.15).
The splitting technique also works for insulating behind vertical runs of plumbing, and not only insulates copper pipes but also
Figure 8.14 Splitting technique. (NAIMA)
Figure 8.15 Splitting technique. CNAIMA)
helps to reduce noise from PVC waste stacks. To guard against pipes freezing, insulation should never be placed between piping and the warm side of the wall.
Junction boxes for wall switches and convenience outlets at outside walls should be insulated between the rear of the box and the sheathing. Place insulation behind the junction box, and if necessary, cut insulation to fit snugly around it. If installing kraft-faced batt insulation, use the outside of the box as a guide to slice the paper carefully, which lessens the chance of ripping it.
Some installers prefer using 4-ft batt lengths because they are easier to maneuver around wiring and plumbing in the bays. If batts are stacked in a bay, make sure that the butt joint between
the batts is tight. The batts should fit snugly in the bay and should fill the width of the stud from the sheathing inward.
Special cutting of insulation may be required for less than standard width or length cavities or for insulating around window and door framing, stud corners, and band joists and between chimneys and framing.
Ceiling joists below an attic. When ceiling insulation is installed at the same time as wall insulation, it can be installed from below. Batts or rolls, faced or unfaced, are installed between ceiling joists and butted together. Faced batts should be stapled to joists unless the manufacturer recommends pressure-fit applications.
It is particularly important that clearance for air movement from vent openings be maintained. This should be a minimum of 1 in of unblocked free airspace between the roof sheathing and the insulation. (Verify the amount of airspace required with all applicable building codes.) The insulation should extend far enough to cover the tops of the exterior walls but should not block the flow of air from the eave vents. To make sure that the eave vents (also referred to as soffit vents) are not blocked, attic vents or baffles should be installed to provide unrestricted airflow from the soffit to the attic if prohibited by insulation placement. It is important also for the insulation to cover the top plate. Use baffles if necessary to keep the insulation from blocking the passage of air (Fig. 8.16).
Vapor retarders are not a standard recommendation for attics. Exceptions may include very cold climates or isolated cases where there is high humidity in the house during the winter. An attic vapor barrier is not required by building codes, as long as the attic is sufficiently ventilated. If used, proper orientation of the vapor retarder is consistent with other locations in the home. For example, if the vapor retarder faces the inside of the room in sidewall installation, it also will face the inside of the room from the ceiling. Penetration of the vapor retarder by recessed lights, attic openings, and vents can provide paths for conditioned air and moisture to escape into the attic.12
Bridging or cross-bracing of ceiling or floor joists is insulated by splitting a batt vertically at the center and packing one half into the lower opening and the other half into the upper opening. Another method is to butt the insulation to the bridging and then fill the bridging space with scrap or loose insulation.12
After the ceiling gypsum wallboard has been installed, temporary flooring should be laid across the joists to provide some foot-
ing. It is easiest to place the insulation blanket at the outer edge of the attic space and work toward the center. This allows for more headroom in the center of the space, where cutting and fitting can be performed. Stapling is not required if insulation is laid in over finished ceilings.
If the joist cavities are completely filled and the required R-value has not been achieved, insulation in long runs perpendicular to the direction of the joists should then be placed. Leftover pieces can be used for small spaces.
Insulation should be kept 3 in away from recessed lighting fixtures unless the fixture has an IC rating. (The IC label, for insulation contact, can be found on the inside of the fixture.) A type IC insulated ceiling fixture is designed for direct contact with insulation. If insulation is placed over an unrated fixture, it may cause the fixture to overheat and perhaps start a fire. Insulation always should be installed at least 3 in away from the recessed fixture’s wiring compartment or ballast or any metal chimneys, gas water heater flues, or other heat-producing devices.
Attic rooms. Attics that are used as living spaces are to be insulated as other habitable rooms are. Attic framing can be a little difficult to work with, so rafters and collar beams should be insulated with separate pieces of fiberglass insulation. Trying to fit a continuous length of insulation where collar beams and rafters meet may result in gaps or compression of the insulation.
When selecting and installing insulation for the rafter portion, 1 in of ventilation space should be provided between the insulation
and the roof sheathing. Eave vents and baffles that run along the entire ceiling cavity will ensure proper airflow.
The framing member size of the rafter will determine the batt selection. For example, 2" X 10" joists will require R-30C high-den – sity insulation that measures 8V4", and will automatically provide the required ventilation space when installed properly.
Verify that the exterior thermal envelope is insulated. This will require insulation in knee walls, end walls, dormers, and any other surface that encompasses the conditioned space. As soon as the insulation has been installed, finish the walls and ceiling with an approved interior finish, such as gypsum wallboard.12 See Fig. 8.17 for proper attic insulation locations.
Cathedral ceilings. The “rules” for cathedral ceilings are similar to those applied to attic rooms. A ventilation baffle should be installed at the eave of every joist to make sure that the ventilation space is not blocked by insulation. Baffles used in cathedral ceilings to maintain an air passage to the ridge should not extend farther than the wall plate and should not block soffit vents, because any obstructions in the soffit will disrupt airflow. As mentioned earlier, fixture ratings, vapor retarder orientation, and proper placement must be respected.
Floors. Floor insulation limits all three modes of heat loss. A warmer floor reduces the temperature difference that drives convection. Floor insulation also directly impedes conduction and radiation to the colder air below the floor. Like walls, floor cavities should be completely filled with insulation without gaps or voids.
(1) Between collar beams. (2) Between rafters.
(3) Knee walls. (4) Ceilings with cold spaces above. (5) Dormer walls. (6) Dormer ceilings.
Figure 8.17 Attic rooms. (.NAIMA)
The most efficient use of floor insulation requires contact with the subfloor and both joists.
Given the deeper joist members commonly used in the longer spans of engineered wood systems, the amount of floor insulation required by some codes can be less than the space available. For example, an R-19 batt is 6V4" thick. A floor framed with 2 X 8s is about 772" deep, whereas a 2 X 10 floor is 972M. To avoid a gap in this situation, the batt must be pushed up into the cavity. This is easily achieved with the proper intermittent supports.
The easiest and most effective method of holding insulation in place is to use straight, rigid wire insulation hangers (preferably galvanized) with pointed ends. The hangers are made for joist spac – ings of 12, 16, 18, 20, and 24", and may be used against wood, metal, or concrete. The hangers, which are slightly longer than the joist spacing, are placed by hand between the joists and bowed upward into the insulation, causing the insulation to press gently against the subflooring. Spacing of hangers is as required to prevent sagging of the insulation, preferably 12" apart and not more than 6" from ends of batts and rolls (Fig. 8.18).
When insulating floors where the insulation is less than the thickness of the joists and the method of installation does not hold the insulation up against the subflooring, it will be necessary to insulate the headers or band joists at outside walls. This is so because there will be an airspace between the top of the insulation and the subfloor that will allow heat to be lost at outside walls. Therefore, it is recommended that the insulation be pushed up to the subfloor.
Although floor framing is typically 16 or 24" on-center bays, historical home designs may vary. Therefore, a number of insulation hanger systems are available:
1. Metal rods, or spring rods, or “tiger claws” are available through insulation distributors. They are easy to use, but compress the insulation in the middle.
2. Wood lath provides a sturdy support for insulation.
Figure 8.18 Insulation hangers. (NAIMA)
3. Plastic mesh should be attached to the bottom of the framing. Draping the mesh over the joists leads to compression that reduces insulating value.
4. Polypropylene twine resists rot, mildew, rodents, and other dangers. The twine needs to be stapled every 12 to 18".
5. Plastic straps are typically a thin strap made of recycled plastic. The ends are wider for easy stapling. The strap can attach to the joist bottom or lift a batt up into the cavity without compressing it.
6. Galvanized wire, nylon mesh, or galvanized screen (chicken wire is also suitable) will hold the insulation in place. After the insulation has been pushed into place, the mesh or screen is stapled or nailed to the joist faces.
7. Galvanized, malleable wire may be laced around nails protruding from the faces of the joists, or the wire may be stapled to the joists. Wire and nail spacings are as required to prevent sagging of the insulation.
Buying a thicker batt may be a better option than trying to lift a thinner batt into the proper position. Material costs will climb slightly, but labor should be the same. Attaching the insulation support to the bottom of the floor joist will be easier. It also could lead to a higher-quality job, because there is less chance for compression or gaps.
If insulating over an unheated area, the vapor retarder should be in substantial contact with the subfloor. Where the header is parallel with the floor joists, it may be necessary to adhere insulation to the header or fill the joist area with insulation. If you insulate above an unheated crawl space or basement, you also will need to insulate any ducts or pipes running through this space. Otherwise, pipes could freeze and burst during cold weather in northern climates.
Cantilevered overhang areas must not be overlooked. If the underside of the cantilever has been closed, insulation must be installed by sliding batts into place from the room below (Fig. 8.19).
For homes where the underside of the floor is exposed and readily accessible, such as homes on pilings or certain garage areas, the insulation should be covered with a suitable exterior material to protect it from high winds and physical abuse.
Heated crawl space. More common in northern climates, heated crawl spaces help protect water pipes from freezing while also elim-
Figure 8.19 Cantilevered overhang. (NAIMA)
inating the need for under-floor insulation. The first step is to measure and cut small pieces of insulation and fit them snugly into the band joist between the floor joists. (Before installing the insulation, check for any air leakage at the foundation sill joint, and caulk or seal this joint as needed.) Use R-13 blanket insulation as a minimum on structures with 2 X 4" sill plates, and R-19 with 6M-wide sill plates. If the fiberglass has a facing or vapor retarder, be sure that the insulation is installed with the vapor retarder toward the heated space (only in cold climates). The insulation can be stapled by the paper or foil facing or fastened with wire fasteners. (Verify with local practice and building codes for proper vapor retarder placement.)
On the two sides where the floor joists are perpendicular to the band joist, cut the insulation material to a snug fit, and gently push it into place between the floor joists. Be sure that it fits snugly against the band joist without being compressed. On the sides where the floor joists are parallel to the band joist, cut longer pieces of insulation (sections of 4 ft or less are easiest to work with). The insulation can be held in place with staples (if faced), tiger claws, thin wire, or fishing line criss-crossed around tacks or nails at 1-ft intervals.
Insulation for the crawl space walls should be cut long enough to cascade down the walls and extend 2 ft along the ground on the crawl space floor. Furring strips should then be installed to hold the insulation in place by nailing it to the sill. By not driving the nails completely through the furring strips the insulation is compressed as little as possible. After the insulation has been installed, a 6-mil polyethylene vapor retarder should be spread across the entire floor. The vapor retarder should be placed under the crawl – space wall insulation (Fig. 8.20). Rocks or bricks can be set on top of the crawl-space wall insulation that extends out on the floor in order to hold it in place.
Basement walls. If fiberglass blanket insulation is to be used for masonry or concrete basement walls, there are two methods that
Figure 8.20 Heated crawl space walls. (NAIMA)
can be adopted. Installing furring strips directly to the masonry wall will allow the use of R-3 or R-6 batt insulation applied directly to the wall (Fig. 8.21). A separate frame wall also could be built, usually of 2 X 4" or 2 X 6" wood framing. The top plate is nailed to the underside of the joists or to blocking between joists. Batt insulation is then installed as in typical sidewall applications.
The framed wall can be very advantageous for installing thicker insulation or if additional electrical wiring is to be run, as is common in most basement renovation projects. It is important to note that the band joists need to be insulated separately. Insulation is then installed as described earlier under “Sidewalls.”
It is important to note that the sealing of a basement may pose a threat of radon gas. If the home is in an area that is known to have soils containing radon, testing measures must be implemented. Venting measures and proper concrete slab construction will be mandatory if a significant concentration (greater than 4.0 pCiditer) is discovered.
As discussed in Chap. 7, mineral wool refers to three types of insulation made from raw materials that are spun into loose-fill or batt products:
1. Glass wool, or fiberglass, made from recycled glass or silicates
2. Rock wool, made from virgin basalt, an igneous rock
3. Slag wool, made from steel-mill slag
Rock and slag wool fall within a group of materials referred to as man-made vitreous fibers (MMVFs), reflecting the glassy, noncrys-
Figure 8.21 R-3 masonry wall insulation between furring strips.
talline nature of these materials. The mineral wool form of MMVFs was developed initially in the late 1800s by melting slag and spinning it into insulation for use in homes and industry. Over the past century mineral wool manufacturing has evolved into a large and diversified industry as more and more products have been developed.
Rock wool and slag wool each use different raw materials in their manufacture. Rock wool is made from natural minerals, primarily natural rock such as basalt or diabase. Slag wool is made primarily from iron ore blast furnace slag. Slag wool accounts for roughly 80 percent of the mineral wool industry, compared with 20 percent for rock wool.9 Rock wool is predominantly used in blanket insulation products.
Rock and slag wool insulations are produced by a centrifugal wheel process. Natural rocks or iron ore blast furnace slag are melted, and the hot, viscous material is spun into fiber by pouring a stream of molten material onto one or several rapidly spinning wheels. As droplets of the molten material are thrown from the wheel(s), fibers are generated. As the material fiberizes, its surface generally is coated with a binder and/or dedusting agent (e. g., mineral oil) to suppress dust and maintain shape. The fiber is then collected and formed into batts or blankets or baled for use in other products, such as acoustical ceiling tile and spray-applied fireproofing, insulating, and acoustical materials.13
The mechanics of rock wool blanket insulation are similar to those of fiberglass blanket insulation. The batt insulation has an R-val – ue of 3.6 per inch and is manufactured for standard joist and stud spacings. Unfaced batts are a good material for insulating around chimneys because the material does not support combustion. Small amounts of moisture have little effect on R-value.