This video documents the progress inside the "Modest House," focusing on the crucial stages of integrating HVAC ductwork, establishing an airtight ceiling, and laying out interior wall framing. The builders detail innovative solutions, such as custom plywood boxes, to create seamless, sealed connections for HVAC supply lines penetrating the Myrex air control layer. The process of installing and taping the Myrex ceiling is demonstrated, emphasizing techniques for achieving optimal airtightness. The video culminates with a preliminary blower door test, yielding a commendable air leakage score of 37.38 at 50 Pascals, validating their meticulous approach to building an energy-efficient envelope before proceeding with interior walls.
Building the Modest House: HVAC Integration, Air Sealing, and Framing Prep
0:00 Initial Progress & HVAC Integration: The video begins inside the "Modest House" with Myrex installed on the walls and HVAC main supply and return trunk lines in the attic. The focus is on preparing the ceiling for interior finishes and wall framing.
0:24 Custom Plywood Boxes for Ductwork: To ensure an airtight seal between the HVAC ducts from the attic and the Myrex air control layer, custom plywood boxes are constructed and installed in the ceiling. These boxes provide a solid surface for sealing connections.
0:41 Air Sealing HVAC Joints: The HVAC team seals every duct joint with mastic to create an airtight connection from the air handler to the rooms.
1:29 Attic Air Deflectors: Attic air deflectors are installed to maintain proper soffit ventilation while allowing for ample insulation at the eaves.
4:09 Purpose of Plywood Boxes Explained: The plywood boxes allow custom HVAC boots to slide in, providing a firm connection point for flexible ducts and enabling a robust, sealed bond to the Myrex air control layer, crucial for airtightness.
4:56 "One Hole, One Penetration" Concept: The design philosophy follows Jake Bruton's "one hole, one penetration" concept, creating a single, sealed point for each utility (like a duct) to maintain the building's airtight envelope.
6:13 Laying Out Wall Plates: The team meticulously lays out and marks the positions for interior wall plates on the floor using a laser level for precise alignment.
15:55 Removing Unnecessary Conduits: PVC conduits, previously laid for potential future PEX line replacement, are cut flush to ensure clear paths for wall framing.
18:46 Myrex Ceiling Installation Prep: After HVAC ductwork is complete, the team prepares for the ceiling's air control layer using Siga Fentrim double-sided tape (later corrected to Siga Twinet) for secure Myrex attachment.
21:50 Myrex Installation Technique: For a flat, wrinkle-free Myrex ceiling, it's recommended to snap a straight line guide and start applying the Myrex from the middle, working outwards.
25:35 Taping Myrex Seams: Siga Rissan tape is used to seal Myrex seams. It's advised to apply light pressure to avoid stretching the Myrex and creating gaps.
29:54 Ceiling Framing for Service Cavity: 2x4 lumber is installed at 2-foot on-center spacing, fastened with 4-inch GRK screws, to create a service cavity for electrical wiring and provide support for drywall.
32:06 Temporary Attic Access: A temporary attic access point is planned in the master closet for insulation and future HVAC return installation after interior walls are framed. This will be sealed later for airtightness.
37:07 Post-Myrex "Yeti Cooler" Effect: With the Myrex ceiling installed and taped, the house achieves an airtight "Yeti cooler" effect, indicating readiness for the blower door test.
38:32 Blower Door Test Results: The preliminary blower door test at 50 Pascals yields an AC50 score of 37.38, which is considered a very good result, confirming the effectiveness of their air-sealing efforts.
39:34 Next Steps: Interior Walls: With the air control layer complete and the blower door test passed, the next phase of construction will be framing the interior walls.