WALL INSULATION

Properly sealed, moisture-protected, and insulated walls would definitely help you increase comfort in your home, reduce noise coming from outside, and make savings in your energy costs. However, walls need special attention when insulation is considered as they make up to the majority of the building envelope facing the outer air.
There are somepoints to be considered for an effective wall insulation. They are:

Walls should be constructed in an airtight way. If there are any air leaks in the wall that appeared during construction they should be blocked. Air sealing reduces heat flow from air and prevents water vapor in the air from entering the wall. In a 100-squarefoot wall, one cup of water can diffuse through drywall without a vapor barrier in a year, but 50 cups can enter through a ½-inch, round hole. In fact, sealing air leaks is 10 to 100 times as important as installing a vapor barrier.
Walls should be completely covered with the insulation material. To maximize insulation coverage and reduce heat transfer, no gaps or compressed insulation should be left, and the wall should be continuously insulated.

Walls should be moisture proof – as much as they can be. To maintain this exterior rain drainage system, continuous air barrier, and vapor barrier located on the appropriate side of the wall can be used. Air sealing and moisture control make insulation more effective. It is a myth that installing vapour barriers is the most important step for controlling moisture in walls. Vapour barriers only block moisture due to diffusion, while most moisture enters walls either through fluid capillary action or as water vapour through air leaks. Causes of rain leaks through exterior walls include improper installation of siding materials; poor-quality flashing, weatherstripping, or caulking around joints in the building exterior (such as windows, doors, and bottom plates); and wind-driven rain that penetrates the exterior finish. To enhance protection against rain penetration, your installer create a drainage plane within the wall system of the home. The following steps should be followed for moisture control:

TYPE OF INSULATION TO BE USED

The wide variety of insulation materials often makes it difficult to determine the most cost-effective products and techniques.
Fiberglass and rock wool batts—Generally, batt insulation is the least expensive wall insulation material but requires careful installation for effective performance.
Cellulose insulation, made from recycled newsprint, comes primarily in loose-fill form. It can be installed in walls using a dry-pack process or a moist-spray technique. It generally costs more than batt insulation, but it offers reduced air leakage through the wall cavity plus improved sound deadening.
Fiberglass and rock wool loose-fill insulation provide full coverage with a “Blow-in Blanket” System (BIBS) that involves blowing insulation into open stud cavities behind a net.
Rigid foam insulationhas a higher R-value per unit surface area than fiberglass or cellulose and stops air leaks, but it is considerably more expensive. It is manufactured in sheet-good dimensions and is often used as the outer layer of insulation.
Foam-in-place insulationcan be blown into walls and reduces air leakage. Some types use carbon dioxide in the manufacturing process rather than more environmentally harmful gases such as pentane or hydrochlorofluorocarbons.

TIPS FOR AN EFFECTIVE INSULATION
1. Review the plans and specifications and identify all walls (including bandjoists) between conditioned (heated and cooled) spaces and unconditioned spaces (exterior, attics, crawl spaces, garages, and mechanical rooms).
2. Use diagonal corner bracing on exterior walls to substitute for corner plywood sheathing and allow continuous insulated sheathing.
3. Use foam sheathing for insulating headers to reduce framing heat loss.
4. Seal all air leaks through walls before insulating, including under the bottom plate, band joist areas between floors, electrical boxes, and all electrical, plumbing, and HVAC penetrations.
5. Use caulk and backer rod or non-expanding spray foam, not insulation, to seal around window and door jambs.
6. If fixtures such as stairs or shower/tub enclosures cover exterior walls and do not allow easy installation of insulation after the sheathing is attached, insulate behind these components in advance using R-13 or R-19 batts and cover with a weatherproof barrier (½-inch drywausing  plastic or other sheet material
7. Face-staple batts because side stapling creates channels for air flow and compresses the insulation, thus reducing the R-value.
8. Obtain full coverage of batt or blown wall insulation. Cut batt insulation to fit snugly into non-standard stud spaces and to completely fill cavity.
9. Slit batt insulation to fit around the back and front side of electrical wiring and plumbing without compressing or tearing the insulation.
10. Notch out batt insulation around electrical boxes and use scraps to insulate behind the box.
11. Once the interior drywall is in place, seal all penetrations with durable caulking.