Energy Star SIP Cottage Granite Falls NC II

Location: Granite Falls, NC

Project Information

Project Type:	Residential, Affordable Housing
Manufacturer:
Builder:	Houward Building Science
Design Professional:
Year Built:	2024

Performance

High Performance:	Yes
HERS/EUI Index Score:	43
ACH50 - Blower Test Results:
kBtu/sq.ft./year:
CO2 lbs./sq.ft./year:

Awards/Certifications: ENERGY STAR Certified, EPA Indoor AirPLUS

House Specifications: Two-bedroom, One-bath home with 816 square feet of conditioned space
Design Features: SIPs wall and roof construction, simple roof design, additional loft storage, and sloped ceilings
Completed: June 26, 2024

Completed on June 26, 2024, this attached and affordable single-floor home offers a compact yet efficient layout of 816 square feet, featuring two bedrooms and one bathroom. Designed for Climate Zone 4A, the project emphasizes energy performance and long-term affordability.

The home achieved a HERS/ERI score of 43 with photovoltaic (PV) integration, reflecting its strong energy efficiency. With annual energy costs estimated at just $874 and projected savings of $1,098 per year, the home delivers a substantial reduction in energy use—approximately 6,286 kWh annually. While incremental costs were not reported, the performance outcomes speak to a thoughtful and cost-effective design.

Key construction features include Structural Insulated Panels (SIPs) rated R-26 for the walls and a SIPs gabled roof. The unvented, vaulted attic is insulated to R-52, and the stem wall slab foundation is protected with R-10 rigid insulation along the slab edge. High-performance double-pane windows with a U-factor of 0.25 and a Solar Heat Gain Coefficient (SHGC) of 0.19 further enhance thermal performance.

Air sealing was achieved at an impressive 0.87 ACH50, and indoor air quality is supported by a Broan Overture Energy Recovery Ventilator (ERV) equipped with IAQ sensors. Heating and cooling are managed by a Mitsubishi multi-zone HVAC system with three indoor units, while hot water is provided by an LG heat pump water heater with a Uniform Energy Factor (UEF) of 3.93.

Though lighting and appliance details were not specified, the home is roughed in for future solar PV, battery storage, and electric vehicle charging—positioning it for even greater sustainability down the line. No energy management system was included at this stage.

This project demonstrates how thoughtful design and efficient systems can come together to create a high-performance, affordable home ready for future energy innovations.