EV Parking) 8,000 Energ y Production (Actual) 6,000 4,000 2,000 0 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb 2019 2020 CumulCahtiavret NTietlteEnergy Performance (2019 - 2020) 40,000 30,000 PVWatts Calculation 20,000 10,000 kWh 0 Net Zero -10,000 Actual Performance Net Negative -20,000 -30,000 Estimated -40,000 Net Energy Production -50,000 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb 2019 2020 74 Zero Net Energy Case Study Homes: Volume 2 SILVER STAR APARTMENTS CASE STUDY NO. 9 (Left) Photo of particulate film coating the PV panels. Its degree of opacity suggests significant effect on the power production of the panels. (Photo courtesy of Green Dinosaur.) The solar generation data since March, 2019, has been corrected with estimated data of these 75 three short periods of production drop-off by taking the data from the adjacent period of time that has full operation. In addition, the solar data for November, 2019, through February, 2020, is simply estimated by that predicted by PVWatts11 for the system as designed and located at the site in Inglewood, CA. This actual performance data, the corrected data gaps and the estimated performance for the remaining four months, are shown in the chart on the opposite page, Solar Photovoltaic System Performance. The chart also displays the monthly energy use totals for the project and, for illustration pur- poses, the PVWatts prediction for the system as desigmed for the entire year. The chart clearly shows that the system is performing at a level of about 35% less than designed and less than the project goal. After some investigation and site inspection, the cause remains somewhat unclear, but the probable cause is inadequate cleaning of the solar panels. (See photo above.) The site experiences a high level of air-borne particulate pollutants that can form a sun-blocking film on the PV panels. The effect can be substantial if allowed to build up, perhaps as much as shown in the reduction of the energy output data. There may also be continuing is- sues with the inverters, which is being investigated. As with the other case studies, The Cumulative Net Energy Production, the bottom chart on the opposite page, essentially shows the progression of the energy performance toward ZNE by adding each month’s net energy performance to the previous month’s total—if, at the end of the 12-month period, the curve returns exactly to the zero-axis, the project is performaing at Net Zero (ZNE). This chart clearly shows the impact of the operational issues with the solar PV system on this project. The ideal system performance is given by the curve that represents that predicted by PVWatts for the system as designed, which just achieves ZNE at the end of the year, The actual system performance, however, falls significantly short of ZNE . Post-Occupancy: Observations and Conclusions The most noteworthy observation is the obvious need for a regular maintenance program for the solar PV system. The system is performing substantially lower than its capability and causing the project to fall short of its ZNE goal, which is a principal concern for client and design team. Real-time monitoring and recording of the performance of the system is being done, which en- ables the facility manager to be informed about any failures of system components or under- production that needs to be investigated. Nevertheless, putting a regular service agreement in place would help to ensure prompt response to any performance issues and to maintain optimal operation of the system. On the energy-use side, the occupants of the Silver Star Apartments are a unique population in that they do not pay utility bills. Therefore, they have no motivation to consider energy efficiency in the operation of the units based on the normal feedback that is given by an energy bill. Moni- toring the individual unit’s energy use and communicating the information to the occupant may influence user behavior to lower energy use. It would be useful in any event for management to have this information. The energy modeling done prior to construction using EnergyPro is based in part on patterns of use for a standard population, as required by code. There may be a benefit in general of knowing patterns of energy use for this population in order to plan more efficient affordable housing of this type in the future. 11 See: https://pvwatts.nrel.gov/pvwatts.php Zero Net Energy Case Study Homes: Volume 2 CASE STUDY NO. 10 Cottages at Cypress 76 PHOTO: RYAN FILGAS 77 CASE STUDY NO. 10 COTTAGES AT CYPRESS Cottages at Cypress Case Study No. 10 Data Summary “Affordable housing” is a recognized urgency for many subsets of the population, each with its special needs and aspects. For some, this subset is low-income families or the homeless with Building Type: Multifamily – support service needs, as in two previous case study projects in this series of books, Zero Net Low Income Senior Housing Energy Case Study Homes. This case study is yet another group for which affordable housing (New Construction) has become an urgent issue: low-income seniors. Location: Fort Bragg, CA What is common to all housing currently under development for these populations is the desir- Gross Floor Area: 17,260 able aspect of zero-net-energy (ZNE) performance for the completed project for the simple rea- son that future energy costs for the tenant or building operator are minimal. Indeed, the award gross sq. ft. of the contract for the design and construction of an affordable housing project often depends on this feature being included in the proposal. The financing arrangements for the project are Occupied: 2014 structured so that ZNE is a natural method of keeping future operating costs low and predictable. On-Site Renewable Energy The form of the building program and project design are also quite different, depending on the System Installed: social group and location. The ZNE design strategies are therefore different as well. This case 131 kW (DC) Solar PV – total study, a project for low-income seniors in a semi-rural area, is a case in point. In a location on the California coast where the decline in fishing and timber industries has led to a decline in moder- 1BR unit: 4 kW (DC) ate incomes, seniors now comprise most of the low-income population. Their lifelong familiarity 2BR unit: 5 kW (DC) with and preference for individual homes rather than larger complexes of adjacent units led to Communal Bldgs: 20 kW(DC) the concept of the neighborhood of small houses, or individual “cottages”. The ZNE design strat- egies therefore involve smaller independent systems and envelope-dominated design of small On-Site Storage Battery: None buildings rather than other types of design approaches better suited to larger buildings. Measured On-Site Energy Production: Background 1BR unit (#26): 6,440 kWh/yr The initiator of this project, Danco Group, is an affordable housing, for-profit developer that was 39.9 kBtu/sq.ft. per year looking to initiate a project in the Fort Bragg area on the Northern California coast. Affordable housing for seniors in one of a portfolio of types of affordable housing pursued by Danco Group 2BR unit (#23): 7,315 kWh/yr in addition to low-income family and supportive-services types. Most of their projects are initi- 31.5 kBtu/sq.ft. per year ated by the company rather than packaged in response to a specific RFP. The company has a construction division and a property management division, which are involved in their projects Modeled EUI (Site): at various times. 1BR unit: 27.8 kBtu/sq.ft. per year Their methodology is that they proactively seek such projects in their geographic area, North- 2BR unit: ern California between San Francisco and the Oregon border, and the company puts together 24.3 kBtu/sq.ft. per year proposal packages to interest local governments who want to create affordable housing for their constituents. If there is interest, Danco Group forms a limited partnership for the project, arrang- Measured EUI (Site): es the financial packages and then acts as the design-build entity to construct the final product. 1BR unit (Unit #26): There is a non-profit partner within that limited partnership (LLC) that is the “managing general 17.4 kBtu/sq.ft. per year partner”, while Dance Group is the “administrative general partner”. A limited partner to provide 2BR unit (Unit #23): financing and to buy the tax credits is the third member of the LLC. 13.9 kBtu/sq.ft. per year Danco Group chose the City of Fort Bragg as a good candidate for their strategic plan to de- Owner/Client velop affordable housing and approached the city with a proposal for a project for low-income Danco Group, Arcata, CA seniors, the local population with the highest need for this type of housing. The city accepted the idea. The company sought and received federal tax credits for the project through a program of Project Team the U.S. Department of Agriculture (USDA), which had a requirement at the time that funding required that the project be ZNE. Thus, ZNE was integral to the program, as described above. Architect: K. Boodjeh Architects, “It does not cost an affordable housing project any more money to go net zero.” —Chris Dart, President of Danco Group. Eureka, CA Structural Engineer: The project site was found after three years of searching and Danco Group, upon final agree- Branch Engineering, Inc., ment with the city, purchased the land and began the project. Springfield, OR Zero Net Energy Case Study Homes: Volume 2 Energy and Sustainability Consultant: Redwood Energy, Arcata, CA Solar PV System Design & Installation: Roger, Arcata, CA General Contractor: Danco Builders Northwest, Arcata, CA 78 COTTAGES AT CYPRESS CASE STUDY NO. 10 South Main Street South Franklin Street Cypress Street 79 Cottages at Cypress - General Vicinity Plan Zero Net Energy Case Study Homes: Volume 2 CASE STUDY NO. 10 COTTAGES AT CYPRESS (Opposite page) Site Plan for The Cottages at Cypress. (Left) View of the project from Cypress Street. (Photo by Ryan Filgas.) Project Process Building Program The program reflects the strong desire of the target population to continue living in separate homes as they have been doing throughout their lives while raising families and working in the local industries. They were not inclined to be forced to live in the close quarters of the unfamiliar housing type of an apartment building or other clusters of units. The developer therefore elected to build small individual homes of the type that were familiar to most local people. As planned and built, the project consists of eighteen (18) one-bedroom cottages, six (6) two- bedroom cottages and one manager’s cottage, for a total of 25 small houses on the two-acre site. There are also two communal buildings: the community center and the shared laundry facility. The cottages are quite small: between 550 sq. ft. and 582 sq. ft. for the one-bedroom units and between 782 sq. ft. and 821 sq. ft. in the two-bedroom units. The shared community building, with the large open room for meetings, a kitchen and a manager’s office, is 1,200 sq. ft. The separate common laundry facility is 470 sq. ft. All the buildings total 17,260 sq. ft. The site includes a designated “coastal wetland area” that was to be enhanced and restored as part of the development. This included a significant portion of the southwest corner of the site. (See the landscape site plan on the opposite page.) The project was also programmed as an all-electric development in order to keep the carbon footprint minimal. Site Constraints Large cypress trees at the northeast corner of the site cast a significant amount of shade on that corner of the site. Because of the limited size of the site and the number of houses planned, units would have to be located in that shaded area. Solar shade analysis showed that two of the house building sites would be negatively affected, namely units #8 and #12. (See the landscape plan on the opposite page.) The solar PV systems planned for those units would not be productive, so their PV panels were placed elsewhere on the site where sunlight exposure was good, namely on the roof of the communal buildings. (See the discussion below in Renewable On-Site Energy Supply.) Low Energy Design Strategies As with the affordable housing Case Study No. 9, the Silver Star Apartments, ZNE performance was part of the program brief, so the solar PV systems were sized to cover slightly more than the annual energy demand of the houses and an allowance for charging an EV, in this case 110%. The one-bedroom units have very similar floor plans and orientations, so this energy demand is much the same for each unit of this type and the same system could be specified for each one. The same is true for the two-bedroom units. Many of the house plans are repeated for both the one-bedroom and two-bedroom units, but are rotated in orientation to make the site plan work. Since the solar panels must face south, this resulted in a different roof orientation and design for the same floor plan. 80 Zero Net Energy Case Study Homes: Volume 2 COTTAGES AT CYPRESS CASE STUDY NO. 10 Zero Net Energy Case Study Homes: Volume 2 81 CASE STUDY NO. 10 COTTAGES AT CYPRESS NORTH COTTAGE #18 1 BR UNIT 01 2 4 8 FT ROOF PLAN COTTAGES AT CYPRESS — FLOOR PLANS AND SECTIONS FLOOR PLAN 82 Zero Net Energy Case Study Homes: Volume 2 COTTAGES AT CYPRESS CASE STUDY NO. 10 NORTH COTTAGE #23 2 BR UNIT 01 2 4 8 FT ROOF PLAN FLOOR PLAN 83 Zero Net Energy Case Study Homes: Volume 2 CASE STUDY NO. 10 COTTAGES AT CYPRESS NORTH COTTAGE #26 1 BR UNIT 01 2 4 8 FT ROOF PLAN COTTAGES AT CYPRESS — FLOOR PLANS AND SECTIONS FLOOR PLAN 84 Zero Net Energy Case Study Homes: Volume 2 COTTAGES AT CYPRESS CASE STUDY NO. 10 STANDARD SECTIONS ALL UNITS 01 2 4 8 FT Zero Net Energy Case Study Homes: Volume 2 85 CASE STUDY NO. 10 COTTAGES AT CYPRESS Building Envelope — Insulation and Windows The windows are double-glazed, but do not have the low-e coatings, which are conventionally used in most climate zones of California to reduce the cooling load produced by solar gains. This location in the mild climate of the Northern California coast generally has little or no cooling load. The seasonally large heating load, on the other hand, is reduced in these houses by the passive solar heat gains that are obtained by omitting the low-e coating. Insulation levels were designed to California energy code only, which required R-21 walls and R-35 roofs. No rigid insulation was installed on the outside of the studs to prevent solar bridging because of the cost premium, not appropriate for tightly budgeted affordable housing. Building Envelope — Airtightness Measures were taken to air-seal the homes and meet the requirements of the Energy Star® for Homes program. These included gaskets under the sill plates as well as complete inspection and sealants in all the gaps in the house walls and roofs. Each house was tested using the Blower Door Test and every house in the final test measured 3.0 ACH50 or better, as required by Energy Star® for Homes. Heating, Ventilating and Cooling Systems The houses are heated and cooled with high-efficiency ductless mini-split heat pumps1. Only one mini-split wall unit is required since the cottages are small. (Above) Ductless mini-split The mildness of the marine climate allows natural ventilation with operable windows for the en- heat pump unit: outdoor com- tire year so no HRV units were specified for fresh air ventilation and the heat exchange between pressor unit (top) and indoor outgoing and incoming air. Normally, they would be recommended for climate zones with larger heating/cooling unit (bottom). heating and cooling loads and very airtight houses. 86 The kitchen fans exhaust directly to the outside and meet Energy Star® standards for power demand, air flow rates and sound level. Recirculating fan units were deemed to be unsatisfactory for their effect on indoor air quality. Lighting and Plug Loads All lighting is provided by LED sources for maximum efficiency. Electric coil ranges were selected were specified for the kitchens for their affordability compared to electric smooth-top type. Electric induction cooktops were considered too costly to specify despite advantages in terms of energy use. Domestic Hot Water Each house has a 50-gallon heat pump water heater2. When the energy modeling for the houses showed that domestic hot water would be a major part of the total energy use, the project team decided to specify heat pump water heaters as an energy efficiency measure. Since this type of water heater requires a comparatively large closet size and the floor plans had already been completed, the water heaters were placed in the attic space to avoid taking up some of the us- able floor space. Construction Since the individual houses were simple in design and conventionally detailed with standard products, the construction process was straightforward. 1 25-SEER Fujitsu 9RLQ with a heating seasonal performance factor of 12. 2 GE GeoSpring™ Heat Pump Water Heater Zero Net Energy Case Study Homes: Volume 2
