Wayland Passive House: The Airtight Insulated Shell
JLC follows the action as the Auburndale Builders crew applies airtight taped fabric and exterior rock wool insulation to a Passive House under construction in Wayland, Massachusetts.
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Ted Cushman/JLC
A framer nails reinforcing steel straps to 2x4 furring at the hip, applied over six inches of Roxul rockwool insulation.
Air bubbles out through plywood during a preliminary blower door…
Air bubbles out through plywood during a preliminary blower door test performed on a rainy day. Leakage exceeded Passive House allowable levels because of the air permeability of the building's plywood sheathing.
Mike Dutra/Auburndale Builders
An early blower door test of the Wayland house revealed that the…
An early blower door test of the Wayland house revealed that the structure's plywood sheathing leaked air. With rain soaking the plywood and positive air pressure applied inside the hose, major air leakage created obvious bubbles on the plywood skin.
Mike Dutra/Auburndale Builders
A view of the Siga Majcoat waterproof breathable membrane roof c…
A view of the Siga Majcoat waterproof breathable membrane roof covering, sealed with Siga Wigluv tape.
Mike Dutra/Auburndale Builders
The crew applied Siga Majcoat air-tight membrane to the entire r…
The crew applied Siga Majcoat air-tight membrane to the entire roof, including the octagon turret roof, and sealed all the joints with Siga Wigluv tape.
Mike Dutra/Auburndale Builders
The crew wrapped the entire house wall with Siga Majcoat waterpr…
The crew wrapped the entire house wall with Siga Majcoat waterproof, vapor-open fabric. Majcoat rolls were long enough to allow covering the entire perimeter with only two vertical tape joints.
Mike Dutra/Auburndale Builders
Carpenter Tim Houldcroft cuts out a window opening in the membra…
Carpenter Tim Houldcroft cuts out a window opening in the membrane-covered wall.
Mike Dutra/Auburndale Builders
Carpenters Tim and Casey work on a window opening prototype in t…
Carpenters Tim and Casey work on a window opening prototype in the Passive House wall.
Mike Dutra/Auburndale Builders
Carpenters Casey and Tim install a Unilux Passive House window i…
Carpenters Casey and Tim install a Unilux Passive House window in the punched opening.
Mike Dutra/Auburndale Builders
A closer look at the Siga Wigluv tape air-sealing detail around …
A closer look at the Siga Wigluv tape air-sealing detail around the window buck.
Mike Dutra/Auburndale Builders
The Auburndale team is attaching Roxul rock wool insulation to t…
The Auburndale team is attaching Roxul rock wool insulation to the walls and roof of the house using a system supplied by Ramset. Here, a carpenter prepares to insert the long driver pin into the hollow fastener tube.
Mike Dutra/Auburndale Builders
The carpenter uses a Ramset gas-fueled fastening gun to drive sp…
The carpenter uses a Ramset gas-fueled fastening gun to drive spiral-shank nails through the pointed end of a plastic tube fastener.
Mike Dutra/Auburndale Builders
Using a Ramset T3 InsulFast gas-fueled gun, the crew applied six…
Using a Ramset T3 InsulFast gas-fueled gun, the crew applied six inches of Roxul rock wool insulation over the air-tight, vapor-permeable Siga Majcoat membrane.
Mike Dutra/Auburndale Builders
Here's another look at the roof insulation job in progress, show…
Here's another look at the roof insulation job in progress, showing staggered courses of 2-foot by four-foot, three-inch-thick Roxul rock wool insulation batts.
Mike Dutra/Auburndale Builders
The roof, face, and cheek walls of the dormers were also insulat…
The roof, face, and cheek walls of the dormers were also insulated with six inches of Roxul rock wool.
Mike Dutra/Auburndale Builders
Another look at the Roxul rock wool insulation on the dormers du…
Another look at the Roxul rock wool insulation on the dormers during installation.
Ted Cushman/JLC
Framers apply vertical 2×6 strapping over the Roxul rock wool in…
Framers apply vertical 2×6 strapping over the Roxul rock wool insulation, to create an air channel under what will be the sheathing for a slate roof. The uninsulated portion of roof at left will be the location for a skylight.
Ted Cushman/JLC
A framer uses long GRK structural screws to attach 2×6 strapping…
A framer uses long GRK structural screws to attach 2×6 strapping for the structural deck for a slate roof.
Ted Cushman/JLC
A framer nails steel straps onto the 2×6 roof strapping, to conn…
A framer nails steel straps onto the 2×6 roof strapping, to connect the strapping across the roof peak to strapping on the opposite side of the roof.
Ted Cushman/JLC
A framer installs metal strapping across the 2x strapping at the…
A framer installs metal strapping across the 2x strapping at the roof hip, to strengthen the roof against wind uplift loads.
Ted Cushman/JLC
Carpenter James Stewart applies Pittsburgh Corning PC 99 sealant…
Carpenter James Stewart applies Pittsburgh Corning PC 99 sealant to the joints between pieces of Foamglas insulation around the house perimeter. High load bearing "HLB" Foamglas will support the brick veneer cladding at this location, but the Foamglas has to be thoroughly waterproofed because of its vulnerability to freeze-thaw damage.
Progress continues on the high-end custom Passive House under construction in Wayland, Massachusetts, by Auburndale Builders. In September, JLC visited the job again to catch up on the latest developments.
By mid-August, the Auburndale crew had completed rough framing and sheathing for the house’s double stud wall frame. With plywood sheathing installed and taped (including over window and door openings), the team did a preliminary blower door test, but fell far short of the required Passive House airtightness spec (0.6 ACH-50). Conducted on a rainy day, the blower door test revealed that plywood, like OSB, is far from airtight, production manager Mike Dutra told JLC (see slideshow).
“When we had the house under positive pressure,” said Dutra, “you could see the air bubbles coming through the plywood.” When the team reversed the fan to apply negative pressure, Dutra said, “It was like it was raining inside” as the fan sucked rainwater through the plywood — proof, if any is needed, that wind-driven rain poses a moisture threat to wood framed walls.
For Passive House, of course, the air infiltration is also a significant energy concern. But Auburndale had already planned on covering the plywood skin with air-tight, waterproof, vapor-open Majcoat fabric membrane. Once the membrane was applied and taped, and after window openings were cut and the Unilux Passive House windows were installed, the house scored .28 ACH-50, easily tighter than the Passive House spec.
Next the crew moved on to installing exterior insulation: six inches of Roxul rock wool batts. They pinned the batts to the walls using the T3 Insulfast system from Ramset, which uses six-inch hollow tube fasteners pinned to the wall with spiral-shank hardened steel nails for a connection with close to zero thermal bridging.
With the insulation applied, framers began to strap over the roof insulation in preparation for a roof deck. Ultimately, the house will get a slate roof. Meanwhile, Auburndale’s crew worked on building an insulated brick shelf to support the building’s brick veneer cladding.
