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The basement slab is wrapped in a blanket of insulation including R-27 of closed-cell spray foam under the slab and R-22 ICF blocks wrapping the slab edges.

The basement slab is wrapped in a blanket of insulation including R-27 of closed-cell spray foam under the slab and R-22 ICF blocks wrapping the slab edges.

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The floor slab is completely insulated with ICF foundation walls and R-20 (3 inches) of closed-cell foam that is sprayed directly onto the ground before pouring the slab.

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ICF foundation walls wrap the floor slab in R-22 of insulation while the entire space under the slab is covered with 4.3 inches of closed-cell spray foam.

ICF foundation walls wrap the floor slab in R-22 of insulation while the entire space under the slab is covered with 4.3 inches of closed-cell spray foam.

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Between the ICF foundation walls, the builder sprayed closed-cell spray foam directly onto the gravel base to provide a vapor barrier and continuous layer of insulation under the slab.

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The foundation walls are ICF block providing two continuous layers (R-23) of insulation around the slab, which will sit on an additional 4 inches (R-20) of low-VOC EPS foam.

The foundation walls are ICF block providing two continuous layers (R-23) of insulation around the slab, which will sit on an additional 4 inches (R-20) of low-VOC EPS foam.

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Brick veneer framed wall supported by a concrete slab-on-grade foundation with a turn-down footing insulated on its top surface, showing anchorage of the wall to the foundation for seismic resistance

Brick veneer framed wall supported by a concrete slab-on-grade foundation with a turn-down footing insulated on its top surface, showing anchorage of the wall to the foundation for seismic resistance

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Right - Additional potential locations for slab-on-grade insulation include (a) under the slab and outside the perimeter with optional underground moisture block, (b) under the whole foundation, or (c) on top of the slab.

Right - Additional potential locations for slab-on-grade insulation include (a) under the slab and outside the perimeter with optional underground moisture block, (b) under the whole foundation, or (c) on top of the slab.

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The builder laid down a 4-inch base of aggregate rock, then covered that with a plastic vapor barrier that is taped at all seams and around all penetrations before installing the rigid foam under-slab insulation.

The builder laid down a 4-inch base of aggregate rock, then covered that with a plastic vapor barrier that is taped at all seams and around all penetrations before installing the rigid foam under-slab insulation.

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Right – Workers lay radiant floor loops over the concrete reinforcement which is laid over a heavy vapor barrier installed over the sub-slab insulation before the slab is poured.

Right – Workers lay radiant floor loops over the concrete reinforcement which is laid over a heavy vapor barrier installed over the sub-slab insulation before the slab is poured.

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Steel angles for supporting brick veneer are offset from the concrete floor slabs of a multistory building with bracket supports to reduce thermal bridging and provide space to install insulation between the steel angles and the slab edges

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Brick veneer is supported by a concrete stem wall thermally separated from the slab-on-grade foundation with turn-down footing which is also insulated on top; anchorage for seismic resistance is also shown

Brick veneer is supported by a concrete stem wall thermally separated from the slab-on-grade foundation with turn-down footing which is also insulated on top; anchorage for seismic resistance is also shown

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Pest protection measures include a termite shield under the rim joist and extending out on either side of the stem wall, insect screening under the furring air gap, and brick veneer to protect slab-edge insulation.

Pest protection measures include a termite shield under the rim joist and extending out on either side of the stem wall, insect screening under the furring air gap, and brick veneer to protect slab-edge insulation.

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Spray foam insulation extends down the foundation wall to the slab, which has been retrofitted by cutting the slab to install drainage mat against the wall and a new perimeter footing drain, along with rigid foam plastic above the slab.

Spray foam insulation extends down the foundation wall to the slab, which has been retrofitted by cutting the slab to install drainage mat against the wall and a new perimeter footing drain, along with rigid foam plastic above the slab.

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This raised-slab poured concrete foundation includes flood-resistant features such as a sloped grade, capillary break under the slab (gravel or sand), vapor retarder under the slab (rigid insulation), and capillary break at the top of the foundation wall

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An externally insulated slab-on-grade is pest-protected by a metal termite shield under sill plate, metal-flashing-wrapped foam under siding, a removable inspection strip of PVC-covered foam, and 2 feet of gravel next to the foundation.

An externally insulated slab-on-grade is pest-protected by a metal termite shield under sill plate, metal-flashing-wrapped foam under siding, a removable inspection strip of PVC-covered foam, and 2 feet of gravel next to the foundation.

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Capillary break beneath all slabs (e.g., slab on grade, basement slab) except crawlspace slabs using either: ≥ 6 mil polyethylene sheeting lapped 6-12 in., or ≥ 1 in. extruded polystyrene insulation with taped joints

Capillary break beneath all slabs (e.g., slab on grade, basement slab) except crawlspace slabs using either: ≥ 6 mil polyethylene sheeting lapped 6-12 in., or ≥ 1 in. extruded polystyrene insulation with taped joints

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This Texas homes uses a slab foundation including a 4-in.-thick post-tensioned monolithic slab with turned-down edges poured over a 6-mil polyethylene vapor barrier and capillary break; slab edge insulation is not used due to termite risk.

This Texas homes uses a slab foundation including a 4-in.-thick post-tensioned monolithic slab with turned-down edges poured over a 6-mil polyethylene vapor barrier and capillary break; slab edge insulation is not used due to termite risk.

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Monolithic slab with a grade beam

Monolithic slab with a grade beam

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Slab independent of foundation wall

Slab independent of foundation wall

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Easy access

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Water Management of Existing Basement Floor

Guide

Guide describing how to retrofit an existing basement floor or slab to reduce moisture issues.

Passive House Underslab Foam & Vapor Barrier: Karuna Video #6

Video

Video describing the under slab and vapor barrier used on a passive house.

Seismic and Thermal Resistance in Slab-on-Grade Foundations with Turned-Down Footings (Monolithic Slabs)

Guide

Guide describing how to construct and retrofit homes built on slab-on-grade foundations in earthquake-prone areas to withstand seismic forces by properly installing wall-to-foundation connections.

Thermal Bridges Redux, BSI-062

Reference

Article describing thermal bridging, construction practices that encourage thermal bridging, and solving thermal bridging through continuous exterior insulation.

Good water management practices like sloping grade away from house, and installing gutters, perimeter drain pipe, a capillary break, and free-draining soils or drainage mat protect the foundation from water saturation.

Good water management practices like sloping grade away from house, and installing gutters, perimeter drain pipe, a capillary break, and free-draining soils or drainage mat protect the foundation from water saturation.

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Rigid foam wraps the exterior of the foundation slab.

Rigid foam wraps the exterior of the foundation slab.

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Water intrusion

Water intrusion

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Pouring the slab

Pouring the slab

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Right – Rigid foam is attached to the exterior of this foundation wall.

Right – Rigid foam is attached to the exterior of this foundation wall.

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Properly installed vapor barrier

Properly installed vapor barrier

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