Sandywoods Farm Net Zero Spec House #1

This is the first of two Net Zero houses built on spec by Church Community Housing in the market rate portion of a mixed-income, mixed-use, arts and agricultural community called Sandywoods Farm.  The development includes 50 Affordable apartments in single family and duplex buildings and 17 unsibsidized market rate lots for sale.  The two Net Zero spec houses have been built in the hope that it will stimulate the sale and development of the other lots and that it will set a precedent for energy efficient home construction that will be followed by the purchasers of those lots.  Furthermore, the Town of Tiverton where Sandywoods Farm is located has a relatively high property tax rate relative to the surrounding communities.  It is hoped that the Net Zero houses would compete favorably with spec houses for sale in those communities by offsetting the higher taxes with low/no utility costs.  Lastly, Church Community Housing has long been dedicated to increased energy efficiency, renewable energy development and sustainable and healthy building materials and practices.  The construction of these Net Zero houses was simply the next step in a long road of ever increasing residential construction performance. The houses stats are:  R-60 SIP Roof, R-50 .8 lb open cell spray foam 12" double stud walls, R-15 closed cell spray foam under the basement slab, R-20 closed cell spray foam on interior of basement walls, R-50 open cell spray foam in rim joist.  Triple glazed, low-E, Krypton gas filled windows and sliding glass door achieving .20 or better U-value.  Super high efficiency "hyper heat" Fujitsu mini-split HVAC system: one floor mounted 15,000 btu unit on first floor, one compact ducted 12,000 btu unit on 2nd floor.  Less than 1 ACH @ 50 Pascals.  Panasonic programable bath fans in both bathrooms set to run continuously based on results of blower door test to ensure healthy indoor air quality.  Tier II vapor retarder interior primer and gasketed electrical boxes to prevent vapor drive through wall assembly.  Electric heat pump hot water tank for domestic hot water.  9kw PV array atop south facing roof. 

Quick Facts

General

Location
34 Vitruvian Lane
Tiverton, RI02878
United States
Building Type single-family residence
Project Type Zero Energy
Basis of Performance Claim Modeled,
Bedrooms 4
Conditioned Floor Area 1 372

Energy Summary

Energy Data Type Modeled,
Renewable Energy System Type(s) Photovoltaics,
Ratings

The house will receive a HERS rating upon completion as a result of it's enrollment in the Energy Star Certification program. Initial modeling showed a HERS of 4 - before installation of the larger PV array and higher density spray foam in the walls. The house is expected to achieve a negative HERS rating (net energy exporter) upon completion.

Annual renewable energy generated 10 890

Envelope and Mechanicals

Subslab assembly

R20 closed cell spray foam sprayed on top of 3/4 stone under concrete basement floor slab.

Foundation wall assembly

closed cell foam sprayed to R20 on inside of foundation walls

Above grade wall assembly

12" double stud walls filled with open cell spray foam insulation.

Door Assembly

Sliding glass door is from same Harvey Tribute line with same spec's as windows. Entry doors are Therma-Tru Classic Craft models

Air Changes per hour, ACH50 1.00
Lot 8 Rear Elevation

Project Team:

Other Team MemberTeam Member: Christian Belden

Other Team Members:

Church Community Housing Corporation, Northeast Collaborative Architects, NPTRE (Newport Renewables), UG Nasons HVAC, FOARD Panels, Bodington Plumbing, Ecologic Insulation, Foster Electric

Ratings:

The house will receive a HERS rating upon completion as a result of it's enrollment in the Energy Star Certification program. Initial modeling showed a HERS of 4 - before installation of the larger PV array and higher density spray foam in the walls. The house is expected to achieve a negative HERS rating (net energy exporter) upon completion.

Awards:

Completion

Completion Date: Wednesday, June 15, 2016

Scope

New construction single-family home built "on spec". No buyer in place yet.

Type of Construction New,
Number of buildings 1
Floor area of each building 2 160
Bedrooms 4
Stories 2
Conditioned Building Volume 11 222
Conditioned Floor Area 1 372

Location and Climate Details

single-family residence

Address
34 Vitruvian Lane
Tiverton, RI02878
United States
Location Type Rural
Climate Region Zone 5
Köppen Climate Type Dfa
Lat. / Long. POINT (-71.2133801 41.6259357)
Elevation 270
Solar Insolation 3.81 kWh/m2/day
Annual CDD and Base Temp 762 | 65 deg F
Annual HDD and Base Temp 6119 | 65 deg F

Site

Site Conditions:

previously undeveloped land,

Site Description:

The unsubsidized or "market-rate" portion of a mixed-income, mixed use arts and agricultural development that has 50 subsidized apartments as well as the 18 undeveloped lots, one of which this house is built on. The overall parcel was 190 acres before the sale and preservation of 90 acres to the local land trust. Of the remaining 100 acres all development of the 50 apartments, arts and agricultural buildings and outbuildings were placed on the 25 acres with soils with the lowest agricultural or forest/wildlife value and the remaining 75 acres are preserved as farm or forest lands. All roads constructed for this development were designed to allow perfect south facing home orientation

Monthly Energy Data and Utilities

Energy Data Type: Modeled,

Electric Utility: National Grid

Gas Utility: N/A

Renewables and Energy Balance

Renewable Energy Sources:

Renewable Energy System Description & Details: 33 Solpower 275kW photovoltaic panels connected to 33 Enphase microinverters.

Annual renewable energy generated 10 890
Annual Renewable Energy Generated Data Type Modeled,
Power Rating 9 075Watts
Renewable Energy System Type(s) Photovoltaics,
Source of Annual Production Data Estimated gross annual production

Walls and Roof

R-60 SIP Roof, R-40 double stud open cell spray foam walls, R-20 closed cell spray foam under slab and covering entire surface of interior of concrete basement walls. R-40 open cell spray foam in rim joist. Triple glazed R-5 windows and doors.

Subslab assembly

R20 closed cell spray foam sprayed on top of 3/4 stone under concrete basement floor slab.

Subslab R-value 20.00
Slab edge assembly

before the slab is poured the closed cell spray foam is sprayed on the stone and up the interior of the foundation walls. Therefore the slab is completely insulated from the outside.

Slab edge R-value 20.00
Foundation wall assembly

closed cell foam sprayed to R20 on inside of foundation walls

Foundation wall R-value 20.00
Above grade wall assembly

12" double stud walls filled with open cell spray foam insulation.

Above grade wall R-value 40.00
Cathedral ceiling assembly

16" thick EPS SIP Panel Roof

Cathedral ceiling R-value 60.00

Windows and Doors

Window Assembly:

vinyl new construction triple glazed, low-e, krypton gas filled double hung windows from Harvey Tribute Line

Door Assembly:

Sliding glass door is from same Harvey Tribute line with same spec's as windows. Entry doors are Therma-Tru Classic Craft models

Average window U-factor 0.20
Door U-Factor 0.20
Door Area 80

Mechanical Systems

Space cooling - Manufacturer & Model Fujitsu XLTH,
Space heating - Manufacturer & Model Fujitsu XLTH,
Domestic hot water - Manufacturer & Model GE Geospring Heat Pump Hot water Heater
Domestic hot water - capacity 60
Ventilation - Manufacturer & Model Panasonic FV 05 11VKSL1,
Lighting Manufacturer and Model LED screw in,
Lighting Efficiency LED,
Mechanical Equipment Installation Details and Comments

blower door testing will be done at end of construction. All ducting is within the conditioned space.

Envelope

Air Changes per hour, ACH50 1.00
Air Changes per hour, CFM50

General Process

House aesthetic and floor plan designed by Northeast Collaborative Architects with input from CCHC regarding function. CCHC staff member completes NESEA Net Zero Homes course and applies lessons learned to ensure the house will function as Net Zero.

Design for Adaptability:

There are 16 remaining house lots to build on. If this design proves popular it can be used over and over again. Also, the most cost effective features of these houses have been incorporated into the design and construction of all other single family homes CCHC develops. So far the result of this is 6 affordable land trust homes being built to zero energy ready and being sold for $150,000. All of these homes will be finished by June of 2016 with Purchase and Sales Agreement in place with buyers for all of these homes.

Software Tools

Software Tools:

N/A

General modeling information:

Mark Rosenbaum's software that is provided in the Zero Energy Homes class.

Lessons Learned

Outcome of Project Goals:

Keeping cost of construction to as close to the standard for a conventionally built home built "on spec" wasn't achieved because of the SIP roof which was expensive both in material and labor costs as compared to a truss built roof. This SIP roof was used because the house is not a full 2 stories it is a 1 3/4 story home with dormers and cathedral ceilings. If a full 2 story design had been started with savings would have resulted from the simple roof design, lack of dormers, and ability to use blown in cellulose insulation in the attic.

Discrepancies:

Not yet able to do actual measurements.

Rebates and Financial Incentives

Federal incentives
Local incentives
State incentives

CommerceRI Renewable Energy Fund $8,649 grant.

Utility incentives

Energy Star Tier III and HVAC and Hot Water Rebates: $5,650

Other incentives
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