Treated 2x4 sleepers with one layer 1 1/2" rigid insulation

The toughest details are those that have to match up with someone else's work, or those done — even done well — when energy was really cheap. These details are a collection of some common — and tough — dovetails of existing work with retrofits or additions. Bear in mind that green remodeling means creating a new operating regime that is better, not worse, than the one that may well have been working just fine before. Integration of energy efficiency, moisture management, and indoor air quality is much more important and challenging in remodeling than in new construction.

Basement and slab-on-grade floors can be retrofit to improve thermal performance but not without managing moisture along the way. There are a host of ways to do this, but headroom and clearance at exterior doors often limit the options. This detail (and its neighbors) assumes that standing or bulk water are not part of the deal; if either is, refer to these details: 9-00030 through 9-00033.

Manage the moisture in an old house

Existing foundation walls (and basement floors) are sometimes wet, usually damp, and seldom dry. Rarely do they have perimeter drainage systems, capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. breaks between masonry and wood (or soil) or insulation. To raise the performance of existing foundation and basement floors, you have to make them manage moisture BETTER than they currently do because you are going to insulate and air seal them, significantly decreasing their drying potential.

Insulating any existing slab — be it a basement floor or slab on grade — means managing moisture as well as heat flow. Ensure that surface and ground water are being managed on the outside of the home, and then assess the extent of moisture wicking up through the slab. The moisture profile of the slab will dictate which technique to use.

Learn more in the Green Building Encyclopedia:

Water management
Enclosure Overview
Foundation Drains
Foundations

DRAWING DETAIL

Download: PDF | DWG

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