A lot of energy can be lost through the attic bays, making the home uncomfortable and increasing energy costs.
The mere presence of insulation isn’t enough to achieve the required R-value in the attic. Insulation has to be installed correctly in order to realize its full R-value. Insulation with gaps, insufficient depth, and insufficient density within the attic bays will deliver a lower R-value than what's stamped on the batts or written on the attic card. For instance, the nominal R-value of the attic insulation may be 38, but if it’s installed incorrectly, its actual R-value may be 30. A lower R-value means energy loss for homeowners.
Several common mistakes can lead to a low R-value in attic bays and subsequent energy loss through the attic. An insulator may inadvertently leave some areas of the attic entirely uninsulated, so that the ceiling drywall is visible between trusses. Batts may be installed with gaps, leaving portions of the attic bays uninsulated. Or, the attic may be left with areas where the insulation layer isn't sufficiently deep or dense.
When an HVAC system is heating the home, poorly insulated attic bays act as "cold spots," where heat from the living space can transfer up through the attic and out of the home by convection. When an HVAC system is cooling the home, poorly insulated attic bays act as "hot spots," where heat from the sun can transfer down into the living space through the attic by radiation. In addition to making the home uncomfortable, energy loss through attic bays increases the homeowner’s energy bills. As heat transfers through the attic, the HVAC system has to produce more heating or cooling to maintain the homeowner’s desired temperature.
Cause 1:
Architectural features
Insulation is often left out of attic areas that are difficult to access. The more complex the home’s architecture, the more challenging it is to insulate the attic. For instance, to build a raised roof section, framers sheathe the main roof and then frame the raised section onto it. If framers forget to cut a hole in the roof sheathing, the insulator won’t be able to access the raised section to insulate it. Common architectural features that make the attic difficult to insulate are:
- Sloped ceilings
- Raised ceilings followed by dropped hallways
- Changes in ceiling height or roofing dimension
- Transitions from mechanical to conventional trusses
- Gables, bays, and bows that are framed in
- Gabes, bays, and bows with low ceilings
- Areas not visible from the attic access
Solution
Plan out the attic job to assure quality and keep construction on schedule. Be familiar with the roof framing, and mentally walk the pathway an insulator will have to take to insulate the attic. Provide access to each attic area. Some areas are difficult to reach after drywall is installed; install batts in these areas before the drywall stage. When planning, it’s important to know the thermal boundary of the home, so the insulator doesn’t miss any areas that should be insulated. If the attic contains several areas where a batt will have to be installed before the drywall stage, it may save time to insulate the entire attic with batts, instead of using a combination of batts and blown insulation. Consult with the insulator.
Give the insulator the tools needed for a successful installation. Have the framer position continuous braces (rat runs) in a way that allows the insulator to walk on them through the attic, instead of balancing on the truss chords. Also, provide work lights for the insulator, so remote areas of the attic are visible.
Cause 2:
Production problems
A scheduling conflict, lack of control, or lack of diligence can cause insulators to leave a home before the attic job is finished. An insulation job is often managed as piecework, with crews coming and going. These crews may not have the authority to take responsibility for the insulation job. An attic crew may work for a few hours, break for lunch, and then forget to finish the job. An insulator may work in the attic until 5:00 p.m. and then leave the site, whether or not the job is complete. Or, an insulator may be called away in the middle of the job to work in another home and then be prevented from returning to finish insulating the attic.
Solution
Before signing off on the attic insulation, check for gaps, insufficient depth, and insufficient density. Some site supervisors may hesitate to check for quality when insulators are onsite. Often, the insulation foreman is more experienced than the site supervisor; it may seem awkward to check the work of a more experienced professional. However, it’s important to find practical ways to discuss the insulation job in order to ensure quality and understand the approaches used by trades. If a site supervisor thoroughly checks the attics of a few homes in a project and discusses them with the insulation foreman, the right expectations will be set, and the insulators will likely meet them in successive homes.
Cause 3:
Trade interference
Trades may have to move insulation after it’s installed. For instance, an HVAC contractor may have to shift insulation out of the way in an attic to find a vent or diffuser when commissioning and balancing the HVAC system. After blown insulation is moved out of place, it's impossible to return it to its original state. The result is poor coverage in the affected attic bays. This problem isn’t limited to blown insulation. For example, an HVAC contractor may move batts and fail to properly replace them.
Solution
Be aware of any activities that occur in the attic after it’s been insulated. Make sure that blown insulation isn't moved after installation. If an insulator has to move blown insulation for some reason, reinsulate the affected attic bays with blown insulation or batts. If batts are moved, make sure they're replaced. In most cases, planning ahead and providing proper access can prevent successive trades from having to move insulation. At the attic hatch, provide a framed step-off point and a walkout to any mechanical equipment, so that trades, as well as inspectors, service technicians, and homeowners can walk into and through the attic without putting their feet down into the insulation.
Cause 4:
Insufficient end dams
Before the attic is insulated, a crew installs baffles, end dams, and depth gauges in the attic. This crew usually has very little guidance. If the crew doesn’t install end dams everywhere they’re needed or installs end dams that are too low, blown insulation may be applied unevenly at areas like slopes, hatches, and garage wall separations.
Solution
Make sure end dams of sufficient height are installed at all areas where blown insulation needs to be contained, such as at slopes, hatches, and garage wall separations, before installing drywall. Keep in mind that blown cellulose isn’t as dense as blown fiberglass. Cellulose has to be blown at a greater depth than fiberglass, so higher end dams are needed. For instance, if an 8.5" end dam is needed for fiberglass, then a 10" end dam may be needed for cellulose. An alternative to using end dams to contain blown insulation in sloped areas of the attic is to use batts or spray foam insulation instead.
Cause 5:
Insufficient number of depth gauges
Before the attic is insulated, a crew installs baffles, end dams, and depth gauges. This crew usually has very little guidance. If the crew doesn’t install a sufficient number of depth gauges, blown insulation may be applied unevenly in the attic bays.
The crew also has to install a sufficient number of depth gauges at changes in ceiling height that create steps and slopes in the attic. For instance, if the ceiling height changes from 8' to 10', the height change creates a 2' step in the attic. If depth gauges aren’t installed on both levels of the step, insulation may not be blown to the correct depth. Some attics slope to create a sloped ceiling below. If depth gauges aren’t placed frequently throughout the slope, the insulation depth may be inconsistent in the sloped area. Depth gauges are printed on only one side. If the insulator can't see the printed side, it may be difficult to blow insulation to the correct depth.
Solution
Place all depth gauges so they’re facing the insulators as they walk through the attic. Depth gauges near the attic hatch should be oriented so that the insulator, inspector, and site supervisor can read them as they enter the attic.
At steps in ceiling height, place depth gauges at both levels of the step before drywall is installed. At slopes, place depth gauges at intermediate levels of the slope. The industry guideline for depth gauges is to install one depth gauge every 200 square feet, but using more depth gauges can help to ensure proper depth in stepped and sloped areas.
Cause 6:
Uneven application
A common mistake is trying to blow insulation over trusses or ceiling joists, instead of between them. The trusses or joists interrupt the arc of blown insulation as it falls from the hose. Another common mistake is walking the minimal distance into the attic and beginning to blow, hoping the insulation will somehow reach all areas of the attic. Both mistakes result in uneven coverage in the attic bays.
Solution
Make sure the insulator blows parallel to the trusses or ceiling joists. Also, make sure the insulator walks all the way into remote areas of the attic, as well as around and behind framing obstructions, to install insulation in the attic bays.
Before signing off on the attic insulation, check for gaps, insufficient depth, and insufficient density. Some site supervisors may hesitate to check for quality when insulators are onsite. Often, the insulation foreman is more experienced than the site supervisor; it may seem awkward to check the work of a more experienced professional. However, it’s important to find practical ways to discuss the insulation job in order to ensure quality and understand the approaches used by trades. If a site supervisor thoroughly checks the attics of a few homes in a project and discusses them with the insulation foreman, the right expectations will be set, and the insulators will likely meet them in successive homes.
Cause 7:
Low level in hopper
The insulator operating the hose to install blown insulation has no control over the amount of insulation entering the hopper. If the team member supplying the hopper doesn’t keep pace with the insulator operating the hose, the amount of insulation supplied to the hose will vary. This will cause the insulation to be over-fluffed (contain too much air), and as a result, have low density in some areas of the attic. In addition, if insulators don’t have a sufficient number of insulation bags onsite, they may intentionally over-fluff the insulation to stretch it over the attic area; the result is low density in the attic bays.
If insulation is blown at a low density, it won’t achieve the required R-value. When cellulose is blown at low density, it eventually settles, making it clear that the blown density was low. Although fiberglass doesn’t tend to settle, blowing fiberglass at low density also results in a lower actual R-value.
Solution
Make sure the insulator has brought the correct number of bags to the job. Before installation, check the insulator’s bag count, using the coverage chart. A coverage chart provides an insulator with the bag count, density, and thickness needed for a desired R-value over a given attic area. During installation, confirm that the correct number of bags is being blown into the attic bays.
Blowing insulation takes at least two people. The team member monitoring the hopper has to keep the insulation to a certain level in the hopper, so the hose can supply the right density. Check the hopper at least once during the attic job. If the picker inside the hopper is visible, the insulation level is too low. The insulator should follow the blower instructions, as well as the blowing chart for the insulation. A site supervisor can mention to the insulation foreman that the hopper level will be checked occasionally in order to ensure that the insulation layer will be sufficiently dense.
Cause 8:
Gaps in batt coverage
Four common mistakes can lead to gaps in batt coverage. If the roof trusses or ceiling joists aren’t parallel and evenly spaced, the insulator won’t be able to install batts correctly. If the insulator uses wall batts instead of attic batts, the batts won't have the dimensions needed to fill the attic bays. If the batts sit too high in the attic bays, they won’t be in full contact with the drywall when it's installed. And, if 4' batts aren't touching end-to-end, there will be gaps between them.
Solution
Make sure the trusses or ceiling joists are parallel and uniformly spaced. Also, be sure to insulate with attic batts. Attic batts are deeper than wall batts. They’re also slightly wider; they expand over the attic framing just enough to touch each other, providing better coverage.
Install an attic batt by pushing it up about 1" past the bottom truss chords or ceiling joists on either side. Then, pull the batt down so that its edges are flush with the framing; this creates friction on both sides of the batt to help it expand. Attic batts should hang slightly between the trusses or ceiling joists, creating a 1" belly, so the batts will be in total contact with the drywall when it's installed. If the batts are faced, make sure the facing isn’t wrinkled; wrinkles will cause the batts to sit too high in the attic bays. If using 4' batts, make sure they’re touching closely end-to-end. Also, confirm that the facing overlaps 1/2".
ProTip!Consider using the crossed batt method, where a second layer of batts is installed on top of and perpendicular to the first layer. Because the second layer is installed on top of the attic framing, the batts are in almost continuous contact for a higher attic R-value.
