FOCO - GoElectric: Net-Positive Engineer's Dream

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SUMMARY

• Built: 2021

• Size: 4,800-SF

• Budget: $950,000 all costs including lot.  (±15% performance premiums ➔ 8% timber framing; 5% high-efficiency envelope; 2% PV system)

• Type: New Construction

• Performance: All Electric, Net Zero, EUI: 12.8 kBTUs/sq.ft./yr

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NARRATIVE

This home was completed in 2021, as a result of a life-long ambition of Go Electric Colorado's Tony Mitchell to design and build an attractive, energy-efficient, net-zero home. After researching the concept for several years he found an inspired designer who worked with ICS SIPs to help. The key was to create a cost-efficient high-performance thermal envelope: combining a high R-value outer shell (walls, ceilings, floors, windows) with air tightness, and ensuring as much thermal mass as possible remains within the thermal envelope to modulate through cold/hot spells. Structural Insulated Panels (SIPs), designed and manufactured in the shop were used, and windows were strategically placed to minimize heat loss and maximize solar gain during the heating season. Great attention was given to ensuring all joints were fully sealed, and thermal bridging was minimized.

With a good envelope, the most energy efficient heating, cooling and ventilation system was designed using a hydronic heat pump (AWHP) and energy recovery ventilator (ERV) to ensure 24 hour filtered fresh air. Radiant floor heating was installed, for comfort and efficiency gains. The main Chiltrix Heat Pump runs only on a 20A/240V circuit. Almost too good to be true, for a 4,800 sq ft home! That's possible with an efficient thermal envelope. Low powered air circulation fans distribute the energy stored in the thermal mass from the basement to other parts of the house, and together with the ERV system, a very comfortable indoor environment is created. Structural exposed timber framing and aesthetic aspect ratio windows add a sense of interest and proportion to the design.

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MATERIALS & CONSERVATION

Fire resilient features: Fire resistant stucco, no vents. Firewise landscaping.

Natural Materials: Douglas Fir exposed timber frame.

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SPECIFICATIONS

WINDOWS

• Spec: Anderson A-Series, Uf 0.30

ENVELOPE + INSULATION

• Airtightness: 1.0 ACH50, <0.1 ACHnat

• Slab: R-20, XPS

• Wall underground: R-20, XPS

• Wall aboveground: R-40, ICS Eco-SIPs

• Roof: R-49, ICS Eco-SIPs

MECHANICAL

• Heat Pump: Chiltrix CX-34

• ERV: RenewAire ERV - up to 270cfm

• Hot Water Heat Pump: Rheem Platninum, UEF: 4.2-65 Ga

• Radiant Heat: Entire home

ON-SITE RENEWABLES

• PV: 13kw Sunbox Solar array - produces 21Mwh per year

• Geothermal:

OTHER GREEN FEATURES

• EV Charging (2)

• Induction Cooktop

• Heat Pump Dryer

• Sustainable landscaping