II. BAIHP Technical Assistance (D-E)

• Dukane Precast
  Naperville, Illinois

Figure 13 Completed Dukane Precast home tested by BAIHP

FSEC made a February 2002 site visit to Dukane Precast in Naperville, Illinois and provided technical design assistance in a follow-up telephone conference call in March ‘02.

In 2003, Dukane Precast requested BAIHP assistance in the design phase and monitoring of the first prototype of a new line of homes called “The Fortified House (Figure 13). Objectives of Dukane’s Fortified House include energy efficiency, comfort, durability, and good indoor environment conditions.

In December 2003, FSEC visited 3 prototype buildings in various stages of construction in. One was complete. Researchers made recommendations regarding window flashing, below grade drainage and waterproofing, interior ducts, air sealing, attic access detail, floor finishes with radiant heating, radiant heat zoning, ventilation system design and operation.

In February, FSEC returned to Dukane for testing and infrared evaluation of 3 completed prototype Fortified Homes built by Dukane’s sister company, Mustang Construction at Keller Court, Boilingbrook, IL, just west of Chicago.

Infrared images were recorded from the inside and outside during a calm morning with ambient air temperature of about 25 º F and interior temperatures of about 70 º F, and whole house air tightness was assessed with a blower door test. Whole house infiltration was ACH50=1.28 (very low) 11 Keller Court data (Specifications, Table 11) was obtained with a multipoint blower door test. IR scans found no major infiltration pathways.

The ceiling and gable end of the vaulted living room were built with wood frame construction instead of precast concrete. Both showed higher heat loss than was generally found in the precast panels. Flaws in the continuity of ceiling insulation over the vaulted ceiling were visible from the vented attic. especially around can lights. The flat ceilings in this home were insulated with R-38 rigid polyisocyanurate loosely laid on the concrete ceiling panels. Dukane has now switched to an R-23 precast panel for ceilings.

Opportunities for Improvement

Figure 14 IR-scan showing metal trusses in precast walls. Temperature at the crosshairs is 20.2 ° F. Overlaid temperature graph shows temperature variation of the surfaces at the white line running horizontally through the crosshairs.

Infrared scans were performed on the ranch home and two other homes nearing completion on Keller Court. All three had the space heating system in operation holding the interior near 70 F. Initial scans of the exterior clearly showed increased heat conduction at the truss locations in the precast panels (Figure 14). The metal truss members are cast into the assembly to connect the interior and exterior panels and allow for approximately 3 inches of polyisocyanurate foam (R-23). Exterior infrared scans showed a 2 - 4º F temperature rise at truss locations; exterior temperatures were between 12º and 24ºF.

Increased heat loss was also visible at the top and bottom of precast sections where field connections are made during construction and filled with grout. Each panel has at least two lifting fasteners imbedded in the top edge for the crane to connect to during home construction. Foam insulation around these fasteners is sometimes removed to connect the lifting hook and the void is re-insulated in the field. Insulation levels are reduced where precast walls are connected to floors and ceilings. These areas have one inch of rigid XPS foam (R-5) next to the outer panel but are otherwise left open until structural and electrical conduit connections are made in the field after which they are filled with grout.

Interior Ducts and Moisture Issues

FSEC Researchers met with Dukane Precast staff, their architect and mechanical contractor to identify a way to incorporate interior ducts into a new model of the Fortified House. Ducts are used primarily for cooling and ventilation as all Dukane Precast homes are designed with in-floor radiant heat driven by a high efficiency (92 AFUE) boiler. The boiler also provides domestic hot water in conjunction with a 50-gallon storage tank.

The main obstacle to building interior ducts was finding a place to run ducts from the basement mechanical room to the first and second floors. Agreement was made to run supply risers near the center of the home and returns in a chase on an outside. The two-story foyer offers the best placement for a central return for both the first and second floor supplies.

Dukane is currently using a high velocity, small duct air conditioning system by Unico with 2-inch diameter supply branches that are easier to fit into walls and chases than low velocity ducts. One unoccupied home had problems with condensation accumulating on the attic-mounted ducts. The cause was traced to humid indoor air contacting cold metal trunk lines in the vented attic.

No occupant-related moisture was present but the precast panels, which are still in the process of drying, are one possible source. Periodic mixing of the indoor air may be all that is required until moisture output from the panel is reduced. Otherwise, introducing dry air was recommended to prevent condensation. Findings and recommendations were sent of the Dukane Precast in a Trip Report.

• Dye Company and DelAir - Southern Living Home
  Category A, 1 Home
  Category B, 1 Home

Florida H.E.R.O. met with Dye Company president and his staff to discuss the new Southern Living Home planned for showcase at the 2003 Southeast Building Conference (SEBC) in Orlando, Florida. This firm has a strong desire to differentiate their homes by emphasizing healthy and energy efficient homes. Florida HERO introduced the Building America systems engineering approach to the builder and subsequent discussions resulted in Dye’s commitment to partner with Building America in this project. As a result, researcher met with DelAir mechanical contracting to discuss the development of mechanical specifications for the Southern Living project.

This home did have a Honeywell ERV added and had a HERS score of 88.5. While this home did not meet the BA standard of performance for the 2003 SEBC show, retrofits were being completed to bring it up to BA performance level.

The 2004 home achieved a HERS of 89.6. Both homes have unvented attics with ducts in conditioned space, and used heat pumps with SEERs ranging from 13.5 - 14.1. Windows in the 2004 home had a SHGC of .29 and gas (LP) instant hot water heaters were used.

• EnergyGauge® USA
  FSEC - Cocoa, Florida

Figure 15 Window input screen from EnergyGauge USA home energy rating and simulation software.

This software uses the hourly DOE 2.1E engine with FSEC enhancements and a FSEC-designed user friendly front end to calculate home energy ratings and energy performance. (Figure 15) Researchers continue to improve the software’s features and accuracy. Version 2.0 incorporates many enhancements, which may include multiple zones, multi-fuel use, and a detailed solar thermal and solar electric system analysis. For more information, please visit www.energygauge.com .