• Floor Research

A weak link in the energy analysis of residential buildings is heat transfer modeling for on-grade floors, crawlspaces, and basements.  Researchers planned to construct two test buildings at FSEC to conduct this research. After careful analysis, using a detailed finite element software to define the size necessary for a residential test facility, staff determined that the best facility size would be 40' x 40'.  However while gathering information about DOEs construction processing paperwork, it was determined that the process would probably take two years.  Because of this information, the task is being discontinued.  This year, a request was made to expend the funds for this task on an alternate high profile task.

• NCA&TSU Side-by-Side Manufactured Home Monitoring

Side-by-side monitoring of two manufactured homes at North Carolina Agricultural and Technical State University  (NCA&TSU), evaluated the value of a variety of energy saving technologies and techniques.  (Please see Figure 62 and Table 21.)  Home instrumentation measured energy consumption as well as interior and exterior climatic conditions.  The "standard home," designed and built to basic HUD code requirements, represented the control home.  Modified to use at least 50% less energy, the "energy home" met Building America standards.  Cooperating researchers at NCA&TSU and FSEC investigated energy feature performance and compared actual energy used to energy modeling program predictions.  In-situ energy performance data provided researchers with interesting information on both issues.

Figure 62.  Side-by-side monitoring of manufactured homes.

Data collection on the two homes began in early January 2001 and continued through this reporting period.  Palm Harbor Homes in Siler City manufactured both homes, the results for program year three and four are detailed below. 

Year 4 Side-by-Side Monitoring Results: During Phase 2, modifications were made to the solar water heating system in the energy efficient housing unit to help improve the performance this system.  Further, a number of the incandescent light bulbs in the energy unit were replaced with compact fluorescent bulbs.  These changes were staged to allow an evaluation of the effect of each measure on the home's energy use.

Based on investigative results, it can be concluded that:

• Changes in the building envelope, HVAC and duct systems, and fenestrations in the energy home met researchers 50% energy use reduction goal.  Measured annual energy savings for heating and cooling energy was 58%, and 53% for heating, cooling, and hot water production.
• Care should be exercised in the manufactured housing unit setup or relatively minor construction deficiencies can significantly reduce a home's energy efficiency.  Many of these items are invisible to the homeowner, therefore procedures must be developed to ensure that deficiencies do not occur during setup.
• The Energy Gauge energy analysis program appears to give a reasonably accurate prediction for expected energy use reduction in a typical manufactured housing configuration.  The predicted energy savings for the housing units evaluated in this investigation ranged from 54% to 63%, while the measured values ranged from 53% to 58%.  Version 2.0 of the Energy Gauge Program provided a more accurate energy savings prediction than the older software versions.
• An increase in pipe and tank insulation can increase not only the energy efficiency of a solar water heater by reducing stand-by losses, but also can reduce the cooling load in a manufactured housing unit and increase the overall energy efficiency of the water heating unit.  Even small amounts of exposed piping can significantly affect the energy efficiency of the water heating system.
• While providing essentially the same lighting levels, replacing incandescent lamps with compact fluorescent bulbs not only reduces lighting energy use, but also reduces the home cooling load.

The total measured energy used by each of the housing units for cooling and heating are shown in tables below.  Table 22 shows the energy used for heating and cooling the standard housing unit from January through August of 2002.  The standard home datalogger was struck by lighting in mid-August 2002.  Data after this point was not included since only partial data is available and  performance comparisons were not possible.  Table 23 shows a summary of the cooling and heating energy used by the energy housing unit.  Tables 24 and 25 list the energy use for hot water production for the standard and energy units, respectively. 

Cooling and Heating Energy Use
	SEP	OCT	NOV	DEC	JAN	FEB	MAR	APR	MAY	JUN	JUL	AUG
Actual Values (kWh)
Phase 1	337.3	205.7	150.8	452.8	1087.3	472.8	426.9	184.8	528.3	891.5	850.9	671.6
Phase 2					680.7	537.1	378.1	241.9	311.8	603.0	668	626.6

Domestic Hot Water Use
	SEP	OCT	NOV	DEC	JAN	FEB	MAR	APR	MAY	JUN	JUL	AUG
Actual Values (kWh)
Phase 1	197.8	267.7	250.2	212.6	0	0	217.6	244.9	258.1	227.5	207.9	213.5
Phase 2					294.6	280.9	283.2	264.9	280.2	192.2	200.3	85.2

Domestic Hot Water Use
	SEP	OCT	NOV	DEC	JAN	FEB	MAR	APR	MAY	JUN	JUL	AUG
Actual Values (kWh)
Phase 1	133.4	176.2	204.2	189.9	0	0	245.5	184.4	183.0	141.2	152.3	126.6
Phase 2					251.1	212.0	202.8	145.9	157.3	74.8	80.3	83.0

Also listed in each table are the monthly energy use values measured during the first phase of this investigation, January through August 2001.  Please note that the energy housing unit data prior to August 2001 is suspect due to duct and HVAC system problems later corrected.  The entire data set, including, temperature, relative humidity, solar radiation, and power use is listed on the FSEC web site www.infomonitors.com.

The total energy used for water heating and central cooling over the period of August 1 through August 15 was 363.5 kWh for the energy home and 596 kWh for the standard home. This represents a 40 % reduction in energy use between the two homes.

The total energy used over the period of August 1 through August 15 for water heating was    27.13 kWh for the energy house and 85.18 kWh for the standard home.  This represents a 68% reduction in energy use with the solar water heating system and compares well with the June and July reductions of 63% and 60%, respectively. Consistent findings indicate that the tank and piping insulation has reduced the standby tank losses and improved the solar water system efficiency.

In the energy housing unit, three of the 100 watt incandescent lamps that were on the evening four-hour timed duration were exchanged for 25 watt compact fluorescent lamps on June 4th.   This change did appear to have a small effect on the cooling load in the energy housing unit. The relative cooling energy used by each of the housing units from June, 2002 through August 2002 showed a small change.  The percentage reduction in cooling energy used by the energy housing unit increased from about 30% to 38%.  However, it is difficult to isolate the effects of the improvements in the solar water heating system insulation and the effects of the compact fluorescent bulbs.  In any event, these effects appear to be much smaller than that produced by the hot water system changes.    

Year 3 Side-by-Side Monitoring Results:  Heating system savings (2001 to 2002) were a remarkable 70% during Phase 1.  Cooling energy season savings were 36%, less than heating but still very substantial. The combined heating, cooling, and water heating savings were 52% for a 9-month period. (Please see Figure 63 for heating savings.)

Figure 63.  Average heating energy savings for NCA&TSU energy home.

• The best manufactured home energy performance can be achieved using the SIP wall and roof systems with the AAC plank.  This performance can be further enhanced with an R-8 unvented crawl space.  Though a manufactured home performs best with these alternative systems, the cost to include them may not make economic sense.
• AAC planks can be designed to replace both the steel frame and flooring systems for HUD code manufactured housing units and modular units.  These planks also can be modified to incorporate built-in insulated ducts.
• AAC planks are pre-manufactured and require less assembly labor than a typical stick framed unit, but including the plank flooring would increase framing costs by 28%.  The heavier weight of an AAC system might exacerbate high framing costs.  Similarly, comparative analysis results found that replacing a conventional framing system with a SIP system would increase framing costs by 66%.
• At the current prices for energy and wood products, neither the AAC plank system nor the SIP systems are as economically effective as improvements in the current conventional HVAC systems, steel and wood framing, sheathing systems, and air barriers with respect to improving energy performance. 
• The use of AAC planks has the potential to be economically viable in the modular housing market, especially if used with sealed crawl space foundation systems, where their improved resistance to moisture degradation would be very important. 
• SIP wall and roof systems also could prove to be economically viable if the price of wood energy increases, and the SIP manufacturing costs decrease through large volume purchases.
• The proposed AAC planking system presents a system that is significantly less affected by water and moisture degradation and may be effective in reducing manufactured housing units' susceptibility to flood damage.  These systems also are not susceptible to termite attack.
• The savings from reduced transportation damage from greater durability and increased floor system stiffness were not addressed in this investigation.  It wouldn't take many days of damage repair (at about $300/person-day for personnel costs related to transportation) to vastly improve the economics of these alternative systems.