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Attic & Crawlspace Insulation

Wall insulation | Drywall | Finish carpentry | Paint | >>Attic and crawlspace insulation | Hard floor coverings

After the ceiling drywall is in place, the attic insulation can be installed. The crawlspace insulation is installed after the electrical, plumbing and HVAC are inspected, often called the 4-way inspection.

The process
Attic insulation is typically blown into the attic space with an insulation blower. Most insulation installers have a truck mounted blower. The insulation is fed into a hopper in the truck and blown into the attic via a 4" hose. Fiberglass and cellulose are probably the most popular insulation materials. Cellulose and fiberglass equal approximately 3 R value per inch of material. If an attic R-value of 36 is required, you would install the insulation to a depth of approximately 12". Most insulations contain fire retardant to inhibit combustion.

Insulation batts can be used in the attic space. However they are more labor intensive than blown in insulation. Blown in insulation is also able to fill in cracks and gaps that batts can't.
Care must be taken when installing attic insulation. The worker must walk on the ceiling rafters. The drywall will not support his weight and will be damaged if stepped on.

Venting the Attic
The attic space needs to be well vented. Otherwise in winter moisture has no way to escape. As warm air rises past the ceiling and insulation, it meets with cool air and causes condensation. The moisture condenses on the underside of the roof decking and drips back into the insulation. This leads to mold and mildew and rotting in the attic space.

Click on the image below to view enlarged attic diagram

Attic insulation ventilation
In the summer attics get very hot, sometimes over 140°. If heat isn't allowed to escape the effectiveness of the insulation is reduced, and the life expectancy of the roof components is reduced. Attic fans are an effective method of cooling attic spaces.
Roof, eaves and gable vents are installed to alleviate this problem. It is important that the eaves vents have baffles properly installed so that insulation blown-in insulation doesn't block the air flow from the eaves vents to the roof and gable vents. Insulation installers are responsible to install these baffles before blowing in insulation.

Notes to the Owner-Builder
Attic insulation is not a critical path task. There is ample room in the schedule to complete it. It usually takes less than a day to complete an average attic space. However it is recommended that it is installed as soon as possible after the Drywall lid (ceiling) is complete thus saving on heating and energy cost and making the work space more comfortable for subcontractors.
Insulation is priced by the square foot of and R value of the material. An insulation blower can be rented from rental centers and some home centers. Installing attic insulation is not a highly skilled trade, however, care must be taken when walking through the attic space.


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