WALLS GO UP AND AIR SEALING BEGINS

The structural framing is nearing completion and roof trusses are soon to be installed. The Ashtree Passive House uses a Larsen-Truss wall assembly based on conventionally framed 2"x6" construction. The house is sheathed in 1/2" OSB which will act as the air barrier and vapor control layer in the middle of the wall.  In preparation for the trusses, air sealing along the top plate is already in place. Enerform is using Siga Wigluv tape to seal joints and corners. 

First floor walls of the house

First floor walls of the house

House and garage walls with second story flooring in place

House and garage walls with second story flooring in place

Second story walls go up   

Second story walls go up 

 

A challenging corner is taped to prevent air leakage

A challenging corner is taped to prevent air leakage

The top plate being air sealed before trusses are installed

The top plate being air sealed before trusses are installed

READY FOR FRAMING

Flatwork is done and the house is ready for framing. In this picture, the finished concrete floor (light gray) can be seen before it is covered with a protective layer for the remainder of the project. Prior to backfilling, the exposed EPS foam along the foundation perimeter was coated in Mel-Rol waterproofing - a product that does not break down EPS. Roof drains and perimeter drains were installed as well.  Next, 2x6 structural walls will be assembled which will later receive sheathing and 8" TJI's to create a deep insulation cavity. 

INSULATED FOUNDATION COMPLETE

With the insulation, vapor barrier and rebar in place, the footings and slab were poured on the Ashtree Passive House. The slab is a thickened-edge design that allowed for a monolithic pour, seen in picture 1. Once the perimeter forms were removed, 6" of EPS foam was glued to the exposed concrete edge to complete the foundation insulation (picture 2). The EPS geofoam provides R-26 insulation below the slab and was used to create thermal breaks between the garage and exterior retaining walls (picture 3). The thermal breaks prevent cold diffusion through the uninsulated garage and retaining wall concrete, which helps keep the house warmer and lowers the energy demand for the home.

Monolithic pour over EPS and Stegowrap vapor barrier

Monolithic pour over EPS and Stegowrap vapor barrier

Gluing EPS foam to foundation perimeter

Gluing EPS foam to foundation perimeter

Thermal break between the house (right), patio (top) and unconditioned garage (left)

Thermal break between the house (right), patio (top) and unconditioned garage (left)

STRUCTURAL GEOFOAM INSULATION LAID UNDER FOUNDATION

The footprint of the Ashtree Passive House has been excavated and filled with eight inches of compacted non-frost susceptible fill. Local firm, MTI tested the compaction of fill to ensure bearing capacity before the first blocks of EPS geofoam were installed. Shown in the picture are the perimeter and interior footing channels put in place before 4'x8' sheets of EPS insulation are installed below the slab. This system encapsulates the foundation in six inches of insulation which will minimize heat transfer to the ground and keep the polished concrete floors warm underfoot . 

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BREAKING GROUND ON THE ASHTREE PASSIVE HOUSE

We are happy to announce ground breaking on the Ashtree Passive House in Boise, Idaho. Excess dirt will be moved from the lot before excavation begins. In the coming weeks we will install a slab foundation over six inches of EPS foam, on top of eight inches of non-frost susceptible fill. These improved construction techniques are the initial steps in building what will be Idaho's first PHIUS+ certified building.