Main Menu

Scionwood Retreat

An Alternative Approach to Net Zero Energy Home

Walls and Roof

This is an on-frame HUD Code doublewide. It measures 28' x 64' = 1792 sq. ft. Concrete footers were poured for all the concrete block piers that carry the weight of the home from the I-Beams and for the parameter brick curtain wall that totally encloses the properly closed crawl space. Prior to pouring the concrete for the parameter footer the tie-down anchors were augered into the footer trench. Following construction below grade foundation water-proofing and a drain to daylight parameter french drain was installed. The finish grade of the soil drains all surface water away from the foundation.
The home uses 2 x 6 wall framing and a 2 x 4 roof truss system with cathedral ceilings throughout the interior and approximately a 3/12 roof pitch.
Insulation values are: Ceiling R-30, Walls R-19, Floor R-22
The windows are intentionally simple. Single-hung, none treated, single-pane glass in an aluminum frame plus and interior single-hung of the same materials. The two windows are separated by the wall framing leaving a 5 inch space.
Space conditioning is provided by a standard heat pump and an energy recovery ventilator. Separate airtight ducts systems were site installed for each.
The properly closed crawl space has a continuous and sealed poly vapor retarder for the ground and walls - leaving a 3 inch view strip at the top of the foundation wall. A dehumidifier with gravity drain to outside manages the minimal water vapor that migrates into the space.

Foundation wall assembly

Concrete footers were poured for all the concrete block piers that carry the weight of the home from the I-Beams and for the parameter brick curtain wall that totally encloses the properly closed crawl space. Prior to pouring the concrete for the parameter footer the tie-down anchors were augered into the footer trench.
The single brick width curtain wall foundation is not insulated. Its height ranges from 3.5 to 4.5 feet tall.
The home is 28 feet wide and 64 feet long.
Above grade wall assembly

2x6 wall assembly with R-19 fiberglass batts. The interior surface is 1/2 inch sheetrock and the exterior is 1/2 inch OSB with vinyl siding
Above grade wall R-value 19.0
Cathedral ceiling assembly

100% of the ceiling is a cathedral assembly using a 2 x 4 truss system
Because it is HUD Code, the ceiling assembly for each half is fully constructed and then placed onto each half of the home as a unit which substantially reduces the wall to attic air leakage paths. The ceiling is 1/2 inch sheetrock and the insulation is blown cellulose.
Cathedral ceiling R-value 30.0
Roof Assembly

2 x 4 truss system
The home is 28 feet wide and 64 feet long.
each section is 14 wide and 64 feet long.
The attic has soffit and ridge venting and the decking is 1/2 inch OSB with shingles.

Windows and Doors

Window Assembly:

Intentionally inexpensive aluminum frame single-hung windows with non-coated single-pane glass.
Interior single-hung storm window of the same materials with the two windows separated by the wall framing leaving a 5 inch space between them

No record of U-factor, SHGC, etc.
Cheap windows

Door Assembly:

foam core filled steel door [3' 0" x 6' 8"] with one third of its area being an insulated glass sandwich fixed window light

Door Area 20 sq ft

Mechanical Systems

Space cooling - Manufacturer & Model Rheem RPRL 024JEZ 2-stage heat pump
Space cooling - capacity 7 kW
Space heating - Manufacturer & Model Rheem RPRL 024JEZ 2-stage heat pump
Space heating - capacity 7 kW
Domestic hot water - Manufacturer & Model Intertherm 20RTOE3JNC - electric
Domestic hot water - capacity 50 gal
Domestic hot water - efficiency 92 kW
Ventilation - Manufacturer & Model Venmar AVS Duo 1.2 with TRE = 75%
Lighting Manufacturer and Model multiple
Lighting Efficiency all lighting is cfl [80%] or led [20%]
Mechanical Equipment Installation Details and Comments

Manuals J,D, S, & T were used in design and selection. With room by room calculations present, air distribution was balanced with air flow measurements. The complete air distribution system including the air handler was tested with a duct blaster and found to have less than 5 CFM25 Total air leakage. System performance was achieved by establishing correct air handler air flow and then establishing proper refrigerant charge. The 7KW heat strip is locked out until outside temperature drops to 20 degrees F.
The ERV ventilation system has a separate sealed air distribution system that was tested with a duct blaster and found to have less than 5 CFM25 Total air leakage. Balanced air flow into and out of the home was achieved by using through the cabinet pressure taps and the resulting air flow measurements at the ERV and then making adjustments to the balancing dampers. There is a simplicity to using a separate duct system for the ERV that avoids a lot of installation mistakes that we find where space conditioning and ventilation equipment are connected to the same duct system.