Casita Kastrop ADU

2023 All-Electric Leader
Outstanding Residential New Construction (ADU)

Location: Redwood City

Building type: Accessory dwelling unit

Status: Completed

Size: 699 sq. ft.

Completion date: April 2022

Energy use intensity: 18

Owner: D. Michael Kastrop and Lorianna Kastrop



This all-electric, vaulted-ceiling, 699 sq. ft. backyard cottage is highly energy efficient, includes solar energy and battery back-up, and features lots of natural light and ventilation.

cabinetry with ample storage space. The north-facing operable clerestorycabinetry in kitchen and bath, plus a large walk-in closet with changarea. An entry coat closet is provided, with a laundry and storage closetoppositsquare foot

Beautifully designed with quality finishes and custom cabinetry, this accessory dwelling unit (ADU) is all-electric and  features clerestory windows, ADA accessibility, and ample storage space. The north-facing operable 
windows provide natural light and ventilation.

The cottage has dual walls with R-30 insulation between, plus 2-inch continuous exterior insulation. This innovative construction technique enhances structural integrity by minimizing penetrations and has a high sound transmission coefficient rating, making it very quiet while reducing heat gain and heat loss.

The 6 kW solar photovoltaic system produces all the electricity needed, and backup battery storage can provide power for three or more days in an emergency power-loss situation. 

Passive Design Strategies:

  • Orientation
  • Window shading (interior and exterior)
  • Landscaping 
  • Daylighting
  • Solar tubes
  • Stack ventilation
  • Window glazing
  • Insulation: R-38 in roof, R-16 in floor, R-6 continuous rigid insulation 

Special Features:

  • Solar PV
  • Battery energy storage
  • Heat pump water heater
  • Induction cooktop
  • Energy Star appliances
  • Other: reversible fans, smart thermostat, smart battery back-up system

Project Team:

Architect: The Kastrop Group, Inc.
Mechanical engineer: GMEP Engineers
Electrical engineer: GMEP Engineers
Plumbing engineer: GMEP Engineers
Structural Engineer: DRE Structural Design
Energy consultant: GMEP Engineers
Contractor: EMC Construction