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Project Description:
When we purchased our home in Lake of the Pines, we did so for the location, not for the house. The crazy 1975 design included 2 oversized gas furnaces that short-cycled so often the house would never get warm. Access to one was through a 20"x20" hole in the foundation wall four feet above the basement floor, while the other, located next to the master bedroom, sounded like an airplane taking off every time it came on. Most of the windows were single-pane and leaky, and most of the beautiful view of the lake through them was blocked by a catwalk. With ants and wasps living year round in the roof, not to mention rodents showing up every few months in the basement, we had no intention of tolerating the status quo.
Our passion for energy efficiency and sustainability led us to Brian Fuentes of Fuentesdesign Architecture. He had been refurbishing houses according to his Passivhaus training thoughout the Boulder, CO area for ten years, and he had been getting many requests for proposals due to the need for rebuilding after the Northern Colorado flood of Sept. 12, 2013. So we felt lucky when he decided to take on scraping and rebuilding our home to net zero standards.
We knew we wanted to take advantage of our dramatic views of Allens Lake and the eastern plains of Colorado, and to let the outdoors in without compromising our netzero goal. We were delighted to learn about Zola windows, and incorporated many floor-to-ceiling windows including a 16 foot sliding door. All the windows are triple pane and highly efficient, providing natural light to all living spaces. Brian led us on an exciting path of discovery and design, including a very tight envelope, a ground source heatpump leveraging three geothermal wells for heating cooling and domestic water heat. We leveraged a variety of insulation layers, a high-impact/wind resistent efficient roof, energy efficient appliances, water efficient low-flow toilets and fixtures, and beautiful finishes featuring sustainbly sourced acacia hardwood floors, natural fiber carpets, LED lighting throughout, and beetle-killed pine ceilings. In addition, the garage includes a 220V outlet for EV charging (when we get one!). We also reduced our own square footage while maintaining our property value by converting the basement into a separate efficiency-style apartment with an amazing view to be used as a rental or for an aging parent or caretaker. We decided to include a larger solar array than strictly needed, so we feel better about our use of appliances, including a hot tub and steam shower!
The result is stunning. We relish each sunrise, the bright open spaces, the quiet interior, and the consistent draft-free year-round comfortable temperatures. Consequently, we hope that our home can be a model for other net zero homes in the state of Colorado and elsewhere.
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Other Awards:
Poudre Valley REA Solar Rebate
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Occupancy Type and Details:
This owner-occupied home has two full-time residents. One resident spends 140 hr/wk in the home and the other, 90 hr/wk.
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Site description:
This home is in a rural residential area with 80 homes around 40-acre Allen Lake. The house is located on a hillside 140 ft above and to the west of the lake.
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Data is from PVREA statements. Production is verified with Fronius on-line resource. Data entered in Annual Energy Import/Export is based on first 4 months (July through October).
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Subslab assembly:
Over existing garage slab was a vapor barrier followed by 12" EPS then conventional floor framing bearing on existing walls, R 52. Existing sloped crawlspaces 3" ccsf (R20) over vapor barrier on ground. There was an existing basement slab that remained uninsulated of 723 sf.
Foundation wall assembly:
basement walls 4" polyiso against concrete with dense pack cellulose in 2x4 interior stud cavity
Above grade wall assembly:
Remodel/new construction 4" polyiso nailbase over 2x6 OVE 24" O.C. framing with netted and blown cellulose
Cathedral ceiling assembly:
18" netted and blown dense pack cellulose in trusses
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Process:
The existing house 70's with 11 different floor levels and poor to non-existent insulation. By using existing garage area for a new kitchen and dining area, views of the nearby lake were captured with minimal new excavation and concrete work. The bulk of the house was completely rebuilt on the existing foundation on a single level for accessibility with a spare bedroom in the basement for guests.
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Special architectural measures:
The house was built with Passivhaus design practices, including an ERV and tight envelope (CFM50 = 399, ACH50 = 0.49). Wall are 2"x6" with 4" of polyiso "nail base" insulation.
Energy Strategies:
The home uses Passivhaus design practices to minimize infiltration with tight envelope and an ERV. A ground source heat pump is used for conditioning the air both heating and cooling as well as domestic water heating. Photo voltaic panels cover the three southern facing roofs sections and provide a standard power of 10 kW.
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Scope Description:
IRC 2012 with Boulder County Amendments, Type VB, not sprinklered. This residential project involved scraping an existing home to the slab-on-grade foundation except for the chimney. Other than minor foundation repairs, the primary element added was a 624 sq ft garage.
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Summary of enclosure strategy/description:
The building envelope involved constructing 2x6 walls with polyiso nailbase over existing slab and Zola windows. Outer finish is fire retardant stucco.
Roof Assembly:
Roof made with composite asphalt shingles from Certainteed rated as Landmark impact resistant: UL2218 Class 4 rating
Window Description:
Zola Thermoclad
Door Description:
Zola Thermoclad
Mechanical Equipment Installation Details and Comments:
Forced air hard ducted system for heating and cooling; separate ERV duct system with flex duct at termination for noise control. ERV jumper ducts at bedrooms.