When insulating an attic what should be insulated

Building codes require such membranes on the lower part of the roof in new houses. These membranes do not stop ice dams, but they prevent the water from leaking through the roof sheathing and into the house. Ice damming can still occur and possibly damage shingles and gutters.

The preferred solution for most houses is to keep house heat out of the attic by air sealing and insulating. Renovations or repairs provide an opportunity to ensure a well-insulated attic ceiling and walls with an effective air and vapour barrier. A popular renovation activity is to convert an existing unfinished attic into a new living space.

Depending on the depth of the rafter space, it may be difficult to achieve the recommended high attic RSI values. If you choose to finish your attic, check for local code requirements and then consider the following steps:.

Figure Extending the rafters provides space for insulation and ventilation. Where headroom is sufficient, constructing a dropped ceiling to hold insulation is an excellent way of thermally upgrading a cathedral ceiling or flat roof, especially when planned as part of a renovation.

The following are several options:. Although it is not necessary to remove the interior finish and expose the rafters and tops of the walls when constructing a new ceiling, it is a good idea.

This will allow you to perform air sealing, check the state of the insulation and verify if there is a vapour barrier. Insulation can also be added on top of an existing ceiling or roof. This option is most suitable for cathedral ceilings and flat roofs when major exterior alterations, such as a new roof, are required.

Air sealing, installing new insulation, sheathing, roofing surface and replacing eavestroughs, soffits and fascia plus disposal will cost several thousand dollars. You will almost certainly need the services of a qualified contractor. One method involves installing rigid board insulation on top of the existing roof see Figure The higher RSI value of rigid insulation means a smaller increase in the roof thickness, although several layers of insulation may be needed to meet the desired RSI level.

Alternatively, a layer of closed-cell spray foam or low-permeability rigid board can be installed with the joints taped to prevent air leakage. This step is not necessary if an air barrier is already in place. It is important to insulate i. This prevents heated air from escaping around the insulation. Line up the edges of the blocking material with the inside finish of the exterior wall and thoroughly caulk all seams. Another approach is to hire a spray foam contractor familiar with air sealing to block these critical areas.

Another method is to build up the existing roof or to frame a new roof and fill it with batt insulation or loose-fill insulation, which is blown in. Ensure that the air and vapour barrier is tightly sealed. The new space or roof frame may add to the structural loading of the entire assembly, so this must be done following local code requirements. This approach is best done with new trusses or by installing cross members called purlins that span the length of the roof.

Once the purlins are in place, the new rafters are installed, followed by the proper installation of the insulation to avoid air movement and thermal bridging. Leave enough clear space above the insulation and above the new roof rafter to allow for ventilation. You will not receive a reply. For enquiries, contact us. Figure Types of attics Larger image. Figure Some attics are easier to work in than others Larger image. Figure Keep combustibles away from a masonry chimney Larger image. Figure Keep combustibles away from an insulated metal chimney Larger image Text Version Figure Keep combustibles away from an insulated metal chimney Storm collar only clamped, not sealed 75 mm 3 in.

Figure Keep insulation away from a recessed light fixture by creating a barrier Larger image Text Version Figure Keep insulation away from a recessed light fixture by creating a barrier Minimum Figure Sealing the plumbing stack Larger image Text Version Figure Sealing the plumbing stack Plumbing stack Pipe clamp Heavy polyethylene strip overlap, caulk with acoustical sealant and staple to the ceiling.

See Figure for the special case of recessed lighting electrical boxes Larger image Text Version Figure Sealing an electrical box Note: See Figure for the special case of recessed lighting electrical boxes. Caulk along gaps at the top of the interior walls Fill holes around electrical wires with caulking Heavy polyethylene sheet caulk with acoustical sealant and staple to the ceiling Electrical box. Figure Sealing a light fixture on the ceiling Larger image. Figure Installation of polyethylene sheets over attic joists.

Rigid foam board at the eaves to maintain ventilation space. Figure Foam board laid between the joists and caulked as an air and vapour barrier Larger image. Install polyethylene between the joists Where obstructions, such as a truss roof, make the previous method too difficult, install a polyethylene air barrier or low-permeable foam insulation board between the joists.

Spray foam between the joists Spray foam contractors can install closed-cell foam between the joists to air seal and add insulation at the same time to the ceiling. Spray foam under the roof This approach involves installing closed-cell spray foam directly under the roof surface, right down to the junction of the ceiling and exterior walls.

Batt or blanket insulation Fit batt insulation into place between the ceiling joists snugly, without compression.

Additional installation tips: Butt batt ends together as snugly as possible. Batts should cover the top plate of the exterior wall but not block the venting. Use baffles between each rafter space to prevent it from being blocked see Figure Insulate above and below cross bracing, splitting or cutting the batt to accommodate the cross bracing as illustrated in Figure Alternatively, cut one batt into a series of wedges and then fit a wedge under each brace.

In either approach, do not compress the insulation. The first layer of batts should be thick enough to completely fill to the top of the joist space. The second layer can then run perpendicular across the joists to block any heat flow through and around the joists see Figure Ensure that there are no gaps between the two layers of insulation. Fill any awkward spaces or gaps with pieces of batt or with loose fill.

Apply blanket insulation in the same way as batts. It may be pre-cut with a knife or cut on the spot. Start at one end of the attic and unroll the blanket Loose-fill insulation Loose-fill insulation can be poured by hand or blown in on top of the air and vapour barrier to a depth greater than the height of the joists. This task can be done by the homeowner using rented equipment or by a qualified contractor.

Before adding insulation, nail enough depth indicators e. Maintain an even depth throughout the attic by levelling the insulation with a board or garden rake see Figure Fill all nooks and crannies. At the eaves, do not block the ventilation. Prevent insulation from disappearing into the eave space by installing a piece of rigid board insulation or a wood baffle before the work begins. Building-supply stores sell cardboard or foam plastic baffles that can be stapled between the rafters see Figure Be sure that the insulation extends out far enough to cover the top of the exterior wall.

If the loose fill is deeper than the joists, build insulation framework a crib around the attic hatch so that it can be filled to the edge see Figure The bags of insulation material will list how many square metres or square feet each bag should cover to provide the required RSI value.

Calculate the attic area to help determine the number of bags needed. If you are having a contractor do the work, calculate the RSI value that you want and check the bags of insulation to be used. They should indicate the area that one bag will cover at the selected insulating value. You and the contractor should then agree on the total number of bags to be used, the expected insulating value and the minimum settled depth of insulation throughout the attic, based on a specific density.

Remember to seal the attic hatch see Figure Seal and insulate up to party walls in attached housing see Part 5. Do not cover recessed light fixtures unless they are installed in approved covers. Figure Baffles can be used to maintain airflow through the soffit vents Larger image. Figure Fitting insulation around cross bracing Larger image. Figure The top layer of insulation runs perpendicular to the bottom layer Larger image.

Figure Installing loose-fill insulation. Pull up and dispose of any material that's compressed, water stained, or moldy—it's useless. Owners of houses built before take note: If what you see is lightweight, grainy, loose-looking insulation with shiny flecks, it could be vermiculite from a mine with asbestos deposits. Get it tested, and if necessary, call in a pro to remove and haul it away safely. The Department of Energy recommends these minimum R-values for unfinished, unconditioned attics.

The numbers are based on your house's location and climate zone. Most federal tax credits for weatherizing your house and boosting its energy efficiency expired in But your state's energy office or local utility may offer product rebates, discounts, or other financial incentives for insulating.

See a state-by-state directory of such programs here. Measure your attic's square footage. For loose fill, read labels; each bag lists the required depths for a range of R-values and the number of bags needed to cover 1, square feet at those depths.

For batts or rolls, calculate the number based on the width and length of the product you're using. In either case, get an extra bag or roll—you really don't want to run out when you're almost done putting it in.

Gaps in the attic or between the lower floors and the attic will let heated or cooled air escape to the great, unconditioned outdoors, making any insulation you add essentially useless.

Find a diagram of common air leaks here. Here's a quick primer on fixing draft-prone spots. Knock these to-dos off your list to ensure that your insulation will last for years and keep conditioned air where it belongs: inside your house. Covering up the soffit vents with loose fill or batts, which can happen if you stuff insulation along the eaves, is a huge no-no. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams, and the material will block that flow.

For the same reason, insulation shouldn't touch the roof's underside. Staple plastic or foam baffles to the roof sheathing, near the eaves, to keep the material away.

Though some batts come with a paper or foil facing that can act as a vapor barrier, Tom Silva prefers to use 6-mil polyethylene sheeting, cut to fit between the joists and with seams sealed by foil tape, to prevent moisture from seeping into insulation.

Whether using loose fill or batts, put the vapor barrier closest to the warm side of your installation, where hot, moist air would get in—facing the house's interior in cold climates beneath floor insulation and the attic's interior in hot climates on top of floor insulation. Some regions don't require a vapor barrier.

In an unfinished attic, the goal of insulation is to keep the rooms below cool in summer and warm in winter. That means insulating the attic floor only—not the walls—and having vents in the roof.

With a finished attic, insulation must help keep the attic areas comfortable. A finished attic should be insulated much like the rest of the house, with insulation in the walls and ceiling.

If your attic is already finished, it probably is at least partially insulated. Unfortunately, you will not be able to get into all the openings. The ceiling will probably be closed off to you unless you remove the drywall or other finish material. You may have better luck getting behind sidewalls also called knee walls.

There are two basic ways to insulate a finished attic. In this case, the area behind the knee wall will be uncomfortably hot or cold. If you want to keep the area behind the sidewalls from freezing in winter, apply insulation from the roofline all the way down to the floor.

Such ventilation keeps the roof cold in winter, which prevents ice dams that can damage your roof and even your house. Each type of insulation is a little different. Always buy an extra bag or roll of insulation to avoid running out mid-project. If your home was built before , and your current insulation looks grainy, feels loose, and has shiny flecks, it may contain asbestos. This type of insulation should only be removed by a professional. Take these steps to get the most out of your attic insulation.

Installing sufficient insulation on the floor of your unfinished attic is the most cost-effective way to insulate your attic. This method will provide a barrier to stop heat from escaping past your ceilings.

Use planks or plyboard to form a safe walking space. The platform should span across at least three floor joists for stability. Never step between the joists in your attic without a safe platform to bear your weight. Most builders or homeowners use polyethylene sheeting beneath loose-fill insulation. Blanket insulation typically has a foil or paper backing to block moisture. After you apply the first layer, no other barrier should be between layers of insulation.

In fact, moisture is likely to build between these layers if the barrier stays in place. Blanket insulation is the easiest material for this task. Cut two layers of blanket insulation to form a thick pad. Staple the pad to the hatch edges to keep it in place. Also, affix weather stripping around the hatch door for a tight seal. Place the blower machine outside, close to an attic window or vent access, and snake the attached hose into the attic.

Wrap hose couplers with duct tape after attaching to avoid couplers vibrating loose during the process. Your assistant will crumble the loose insulation into the hopper while you control the hose inside the attic. This method helps avoid blockages in the hose. Also, mark several trusses at the desired fill level for easier visibility as you work. The machine is too loud to allow communication between partners.

So have another means of communication available, like phones or walkie talkies.