BAIHP Partnership with Atlantic Housing
formingly known as
CED Construction (Sandspur Housing)
Winter Park , FL

Since 2002, FSEC staff have been working with Sandspur Housing, the largest affordable home builder in the nation. Sandspur constructs approximately 4,000 apartment units per year, primarily in Florida and Georgia. The company’s primary interest in Building America is in receiving assistance for designing low energy-use units with good indoor air quality and resolving recurrent moisture problems in Florida’s hot-humid climate. Contact with Sandspur was initiated by BAIHP subcontractor Florida H.E.R.O. in Gainesville, Florida.

Sandspur Housing staff were taken on a tour of the David Hoak demonstration home to show specific equipment and the role it plays in an overall systems engineering approach. After the tour, discussions continued on the Landing Community analysis. This allowed personnel to view firsthand some of the Building America principles and practices so that they could explain these concepts to others in the Sandspur organization.

BAIHP has worked with Sandspur in three Florida cities: Naples, Orlando, and Gainesville.

Naples, Florida

For Camden Cove, Sandspur’s community in Naples, BAIHP researchers conducted an energy analysis on all individual units and several apartment buildings slated for construction in 2003 and 2004. Information from Sandspur’s building plans was combined with Florida H.E.R.O.’s field experience in Sandspur's Gainesville apartment complex Harbor Cove Community. Results indicated an opportunity to cost-effectively reduce energy use/cost in a 16-unit apartment building by more than 20% while improving indoor air quality and durability. Since Sandspur was already building fairly tight duct systems, savings potential in this area was already being achieved. Additionally, heating and cooling loads in multi-dwelling buildings are lower than similar size and construction single family detached housing because there are fewer exterior surfaces.

Energy efficiency recommendations included:

Air quality improvement strategies focused on including:

A summary of all analysis results and building design features was prepared and submitted to Sandspur Housing. Two meetings were held to review the recommendations.

Orlando Moisture Investigations

FSEC staff tested four Sandspur-built apartment units and installed datalogging equipment in six units at the Landings Community in Orlando where some units had reported moisture problems. Measured envelope leakage was typical for new construction, and all but one unit had very tight duct systems. Dataloggers (stand alone temperature RH loggers) were deployed in the air handler of each unit to record interior moisture levels. Three weeks of data were plotted for six apartments as temperature, relative humidity, and dew point. Ambient weather data from the nearby Hoak house datalogger was included and compared favorably with published Orlando airport weather.

To continue investigating the cause of excess moisture in the apartment units, datalogging equipment was installed in six additional units. To remedy problems, prototype schemes were evaluated such as utilizing a humidistat in conjunction with thermostat, and installation of a dedicated dehumidifier. Data analysis will be completed in 2004.

Gainesville, Florida Brookside Apartment Complex

During the 5 th budget period, work was completed on testing and rating all 176 units in Sandspur’s Energy Star apartment complex Brookside in Gainesville, FL. Apartment features are given in Table 21. Each apartment was individually tested for envelope and duct air tightness as well as flow through the passive outdoor air system by Bob Abernethy, FSEC technician, in collaboration with Florida H.E.R.O. Results are listed in Table 21 below. The complex consists of one to four bedroom models grouped into two-story buildings of eight to 16 units.

Cary Park, North Carolina

BAIHP researcher compared two energy savings improvements: (1)upgrade from SEER-10 to SEER-11, and (2) add a programmable thermostat to the SEER-10 unit.

Analysis

The Groves at Cary Park Apartments include a group of five buildings with 12 units each for a total of 120 units. A detailed computer simulation analysis was performed on a single, representative unit to compare the two energy saving measures using Energy Gauge USA version 2.3, which is based on the DOE2.1E simulation engine. The apartment chosen was a top floor 2-bedroom unit with north-facing windows since these units make up 50% of the complex whereas the remaining 1, 3 and 4 bedroom units make up 17%, 20% and 13% respectively and because the top floor 1 and 2 bedroom apartments are the only ones with exposure to an attic space over their entire floor area. The top floor 3 and 4 bedroom apartments are only partially exposed to an attic space while the remainder (about half the floor area) is below a 1-bedroom unit. The added attic exposure increases the heating and cooling loads on the top floor 1 and 2 bedroom units and is likely to present a worse-case scenario in terms of space conditioning load per square foot.

An hourly computer simulation of a top floor 2-bedroom apartment with north-facing windows was performed using TMY weather data for Raleigh, North Carolina. Four of the five buildings shown on the site plan are oriented at or very near to an east-west axis, causing the majority of windows to have either north or south exposures. The fifth building is oriented on a north-south axis. Specifications as taken from the plans provided are listed in Table 22.

SEER-10

The HVAC schedule in the building plans specifies a Carrier 38YKC024 heat pump compressor and FF1CN024 air handler for the 2-bedroom apartments. Literature downloaded from the Carrier website lists this combination as having efficiency ratings of SEER-10.3 for cooling and HSPF-7.0 for heating.

SEER-11

Product data on the 38YKC shows that several other air handler models (most of which are variable speed) can be used to achieve a SEER rating of 11 or higher and can boost the HSPF to 7.2. These efficiency ratings were compared against the SEER-10 unit in an hourly simulation and showed a savings of 138 kWh/year or $12/year at an electric utility rate of $0.0826/kWh.

SEER-10 plus Programmable Thermostat

Estimated savings from using a programmable thermostat in conjunction with the SEER-10 heat pump slightly exceeded the savings from going to the SEER 11 efficiency upgrade alone and showed a savings of 177 kWh/year or $15/year. A 3 °F temperature difference was used for a nighttime heating set-back from 11pm to 7am and daytime cooling set-up from 9am to 3pm.

Conclusion

While it appears from the Carrier literature that the cooling efficiency on this heat pump model can be brought to SEER-11 by upgrading only the air handler, equivalent or better savings can also be obtained by employing a modest (3 °F) set-back/set-up schedule with a programmable thermostat.

For More Information

• For more BAIHP Partnerships and Projects see: http://www.baihp.org/casestud/index.htm
• Atlantic Housing Website