Thread: Insulation in Basement walls

New construction home has 2x6 framing along the exterior wall of a walk-out/daylight 3/4 basement. The basement is unheated space of the home. Instead of putting insulation under the floor, the builder installed R-13 fiberglass batt insulation in the walls.

Couple of questions/concerns:

1. Is R-13 insulation on the exterior wall adequate? Is builder NOT required to install insulation under the floor as well?
2. The batt insulation installed in the exterior walls is exposed, not sheathed. Is this allowed?

Thanks.

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Robert;

First off, what I am talking about here is part of the NJ Energy code. Check with your local building department for your requirements.

402.2.6 Basement walls- Walls associated with conditioned basements shall be insulated from top of the basement wall down 10 feet below grade or to the basement floor, whichever is less. Walls associated with unconditioned basements shall meet this requirement unless the floor overhead is insulated in accordance with sections 402.1.1 and 402.2.5.

The thickness of the insulation should match what is required in the framed exterior walls.

Here in NJ, in order to entice builders to installed better HVAC equipment, the basement insulation is NOT required if ALL heating systems are 90 % (85% for boilers).

I have attached a technical bulletin from NJ for your reading enjoyment. Page 6 is your easiest reading.

Robert,
R-13 is typically used in 2x4 exterior walls not 2x6 walls (R-19 batts are used for that). Builders up here in MI are not required to insulate the basement floor (although it's good practice). The batt insulation should be 1) faced and/or have vapor barrior installed on the interior warm side and 2) be covered with drywall (although I suppose OSB would be acceptable as well (but down the road when the owners renovate the lower level they will probably put drywall on...so might as well put it on now). Hope this helps.

Bob