BAIHP Research: A. Manufactured Housing Research Cont'd

• Portable Classrooms
  Portland, OR; Boise, ID; Marysville, WA

Project Overview

This is primarily a WSU (with subcontractors Oregon and Idaho) and Pacific Northwest National Lab (PNNL) task. Other partners include FSEC, UCFIE, the State Energy Offices of Oregon and Idaho, school districts in Portland, Oregon, in Boise, Idaho and Marysville, Washington, regional utilities, manufacturers, and other stakeholders in the Pacific Northwest.

The objective of this task is to promote the adoption of energy efficient portable classrooms in the Pacific Northwest that provide an enhanced learning environment, high indoor air quality, and both substantial and cost-effective energy savings. BAIHP staff focus on four main goals: (1) offering technical assistance to portable classroom manufacturers, school districts, and related organizations, (2) field assessment, monitoring, and analysis of innovative building technologies and energy saving features to determine their value, (3) facilitation of collaborative agreements among regional utilities, northwestern portable classroom manufacturers and materials and equipment suppliers, as well as school districts, and state education departments and their affiliates, and (4) conducting and creating educational opportunities to advance the widespread adoption of energy efficient portable classrooms in school districts nationwide.

The experiences working on the energy efficient portable were instructive, particularly in the identification of flaws in portable classroom design. The difficulties that BAIHP staff encountered demonstrate the importance of well-defined commissioning protocols, documentation, and coordination among all personnel that service and install HVAC equipment.

Findings:

• Portable classrooms in the Pacific Northwest are occupied about 1225 hours per year, or about 14% of the total hours in a year.
• The average number of occupants in the standard 28’ x 32’ portable classroom provide an internal heat of about 480 kWh/year, or 8% to10% of space heating requirements.
• Most of the heat loss in portable classrooms manufactured after 1990 occurs by air leaking through the T-Bar dropped ceilings, because they have no sealed air/vapor barrier. This newly created phenomenon occurred with the incorporation of the less expensive dropped T-Bar ceiling in place of the more expensive sheet rock used in older portables. Air leakage also is increased because of unsealed marriage lines - now used as a low cost method of meeting the state attic ventilation requirements.
• Since all portables tested in the project used a simple seven-day programmable thermostat, the HVAC systems operate during vacations and holidays.
• Energy codes in Washington, Oregon, and Idaho are high enough to make beyond-code envelope measures non cost-effective.
• Older portable classrooms under removal consideration could be retrofitted with new energy efficiency measures at much less cost than purchasing a new portable classroom. Installing low-E, vinyl framed windows, insulated doors, T-8 light fixtures, and caulking and sealing air leaks can all be cost-effective when refurbishing older portable classrooms. HVAC system replacement in older portable classrooms will be the biggest single cost item, ranging from $4500 to $6500.
• CO 2 sensors appear to be unreliable as a control strategy. Those installed by field crews and monitored by dataloggers in this study did not match the readings shown by the CO 2 sensors which controlled the ventilation systems.

Based on data analysis from years one through four, the following measures were recommended. New portable classroom procurement, setup, and commissioning as well as existing classroom retrofit guidelines produced by the BAIHP study can all be found in Appendix A.

Recommendations:

• Install 365 day programmable thermostats in all existing portables and specify these thermostats for new construction.
• In portable classrooms constructed with T-Bar dropped ceilings, install an air/vapor barrier above the T-Bar system on the warm side of the insulation. Completely seal all edges and overlaps.
• If roof rafter insulation is used, seal the marriage line at the roof rafter joint with approved sealant such as silicon caulk or foam. Make sure there is adequate ventilation between the insulation and the roof.
• Conduct an audit of older portables scheduled for disposal to determine if retrofitting would be more cost effective than purchasing a new unit.
• Install occupancy sensors to control the ventilation system.
• Specify that new portables contain windows on opposing walls.
• Specify that new portable units contain exhaust fans on the opposite side of the classroom from the fresh air supply.

School Partnerships

Figure 64 64 Energy efficient portable classroom at Pinewood Elementary School in Marysville, Washington

Figure 65 Graph comparing heating system use of the Pinewood control portable (P2-Blue) with the energy efficient portable (P5-Red). Note the energy efficient portable’s high energy use during the Christmas holidays due to incorrectly configured heating system controls.

Washington Schools - Pinewood Elementary

An 895 ft 2 portable classroom (P5) was sited at the Pinewood Elementary School in Marysville Washington in August 2000. This unit exceeded current Washington State Energy Code standards with upgraded insulation in the floor, roof and walls, low-E windows, and a sensor-driven ventilation system that detects volatile organic compounds (VOCs). A second portable, built in 1985, and also located at Pinewood Elementary (P2), served as the control unit. (Figure 64)

Energy use comparisons of the two classrooms show that the energy efficient portable used considerably more energy than the control portable. This was attributable to several factors:

• Incorrect wiring of the exhaust fan, causing it to run continually. The fan was rewired in 2000 during the summer break. Once corrected, energy use in the portable declined.
• Incorrect programmable thermostat settings which were not programmed to turn the heating and cooling system off during holidays and vacations. Though energy use was reduced when the portable was unoccupied, use was still excessive (Figure 65).
• Higher air leakage in the energy efficient portable than the control portable. Blower door testing found 19 ACH at 50 Pa in the energy efficient classroom compared to nine ACH at 50 Pa in the control classroom. Follow-up blower door, smoke stick, and APT pressure tests indicated that the predominant leakage path tracked through the T-bar ceiling and into the vented attic due to an ineffective air barrier in the energy efficient portable. The control portable contains taped ceiling drywall.
• No initial HVAC commissioning by the HVAC supplier or the school district.
• Significant HVAC system alterations (including rewiring, ventilation system VOC sensor replacement with a CO 2 sensor, and modifications to other aspects of the HVAC control system) during 2001 by maintenance staff and the HVAC supplier, unbeknownst to BAIHP staff. Calibration testing done by scientists at the Florida Solar Energy Center on the CO 2 sensors showed significant drift in output results. This made data collected virtually unusable.
• The use of plug-in electric heaters during the winter of 2001 by the resident teacher because of room comfort problems. This led to significant room temperature variations and monitoring data showed high plug-load energy use.
• Poor fresh air flow design with the fresh air intake and exhaust fan positioned so they create a “short circuit” of fresh air, bypassing the students and teacher.

BAIHP staff proposed the following recommendations to Pinewood Elementary:

Figure 66 Ventilation system testing at North Thurston School District.

• Well-defined commissioning protocols, documentation, and coordination among all personnel that service and install the HVAC equipment. This is a critical component of efficient and healthy classroom operation and should include outside airflow rate measurements to assess adequate ventilation and control testing to insure correct system operation.
• Design changes to the portable classroom manufacturer, including the use of a structural insulated panel system (SIPS), tighter ceiling barrier and sheetrock ceilings, elimination of the vented attic, and relocation of the exhaust fan to the wall opposite the supply air vent.
• Removal of current HVAC controls and replacement with both an occupancy sensor-driven control for the ventilation system and a heating system programmable thermostat. Staff also proposed a classroom on/off switch to simplify the system turnoff during unoccupied summer and school vacations.
• Location of exhaust fans in future portables on the wall opposite the supply air vent.
• Window installation on opposing sides of the classroom to increase daylight penetration and to assist in passive cross-ventilation.

Based on the above recommendations, WSU researchers worked with Marysville school facility manager and customer representatives from Snohomish Public Utility District to assist them in setting new construction specifications for 13 portable classrooms they will procure during the next reporting period. Marysville School District will specify a completely sealed ceiling barrier, a new model heating/ventilation system, a 365 day programmable thermostat, window placement on opposite sides of the classroom, and exhaust fan placement on an opposite wall from the fresh air supply.

Washington Schools - North Thurston School District

BAIHP staff also worked with the North Thurston School District to troubleshoot a portable classroom in Lacey, Washington. (Figure 66) The classroom was experiencing high energy use and poor indoor air quality. BAIHP staff tested the classroom, made recommendations including opening the supply dampers, installing a wall side vent to better ventilate the classroom and discussed the specification development process with district staff. The North Thurston School District now is including most of the measures listed in the new procurement guidelines for their future portable classroom purchases. The school district will investigate the feasibility of installing an air/vapor above the T-bar dropped ceiling and will record costs for making these improvements.

Idaho Schools - Boise School District Retrofit

BAIHP staff located a portable classroom at the West Boise Junior High School in the Boise Idaho School District, occupied by a teacher who was interested in having the classroom monitored and retrofitted. The teacher also is an Idaho State legislator active in education issues, which staff members believe will increase the chances of implementing the final recommendations. (Figure 67)

Figure 67 Weather monitoring system installation in the Boise portable classroom.

BAIHP staff performed a baseline audit, and installed monitoring equipment to track the classroom’s energy use during 2000. In 2001, the classroom was retrofitted with an efficient HVAC system (controlled by CO 2 sensors), lighting, and envelope measures. The classroom was then reaudited, and monitored for the remainder of the year.

BAIHP staff worked with Pacific Northwest National Laboratories (PNNL) on the pre- and post-retrofit audits, and installation of the monitoring equipment. In their capacity of providing energy management services to the school district, the local utility Avista Corporation, collected lighting and occupancy data.

Monitoring data indicates a 58% reduction in energy usage post-retrofit. Blower door tests indicate a reduction in air leakage from nine ACH at 50 Pa to five ACH at 50 Pa. Data also revealed that heating use actually increased on weekends and holidays because of lack of internal heat gain and because the HVAC control systems are not programmed to shut off on weekends and holidays. The total retrofit cost was $9,892.

Monitored data suggests that the CO 2 sensor that controls the HVAC system is not correctly configured. The system does seem to react to an increase in CO 2 levels early in the day, but does not remain on; CO 2 levels only begin to significantly dissipate after one o'clock PM. BAIHP researchers have noted the difficulty of correctly configuring these sensors in other monitored classrooms.

Oregon Schools

Oregon BAIHP staff worked with the Portland Public School District to procure two energy efficient classrooms. These were constructed to BAIHP staff specifications and included increased insulation, high efficiency windows, transom windows for increased daylighting, a high efficiency heat pump, and efficient lighting. Staff videotaped the construction of one classroom.

Monitoring equipment was installed by PNNL staff. Estimates using the software Energy-10 indicated a total energy consumption of 9200 kWh, or $583 per year at Portland energy rates. Measured results showed the Oregon portable used about 6600 kWh for the monitored period.

Incremental costs for the energy efficiency measures were $6,705 over Oregon commercial code, including approximately $2,500 for the HVAC system. This suggests a simple payback of 10 to12 years.

Initial blower door tests found air leakage rates of 11.3 ACH at 50 Pa. BAIHP staff also identified significant leakage through the T-bar dropped ceiling and up through the ridge vents. Other monitoring results indicated that the same HVAC control problems exist with the Oregon classroom as with the others studied in this project.

The Energy Efficient model outperformed code level models in the Portland area. The older the classroom, the more energy consumed. Even when compared with new code level models from the same year, the Energy Efficient model used 35% less energy. Conventional code level classrooms do not include energy efficient measures which greatly increases the unit’s operating costs. Classrooms built more than 10 years ago, use twice as much energy as the efficient model. Those older than 20 years consume more than three times the amount of energy. From this study, researches determined that high performance classrooms can save anywhere from $200 to $1000 dollars a year in energy costs compared to older, less efficient portables.

A survey sent to teachers and maintenance staff indicates a high degree of satisfaction with the efficient portables; the teachers were most impressed with the improved indoor air quality and increased light levels due to the daylighting windows.

Historical Data Collection

In Idaho, Oregon, and Washington, BAIHP staff worked with local utilities and school districts to obtain historic energy use data on portable classrooms. This data will be used to compare energy usage from the energy efficient portables monitored in this study.

In Idaho, BAIHP staff worked with Avista Corporation's energy manager to collect historic data on 14 portable classrooms in the Boise School District. The classrooms each were equipped with discrete energy meters; as a result, BAIHP staff was able to obtain energy usage data for the past three to four years. A procedure was developed to collect information on portables at each school in cooperation with the physical facilities manager and each school lead. Historic data collection continues. Site visits and walk-through audits are planned for these 14 buildings.

WSU will continue to coordinate with PNNL and FSEC on instrumented data collection on the portable classrooms being monitored in Boise, Idaho, Marysville, Washington, and in Portland, Oregon. WSU will work with Idaho to potentially procure and test one prototype classroom with SIPS. Evaluate and analyze the collected data and prepare articles for presentation and publications.

• Duct Testing Data from Manufactured Housing Factory Visits
  Paper: McIlvaine, Janet, David Beal, Neil Moyer, Dave Chasar, Subrato Chandra. Achieving Airtight Ducts in Manufactured Housing. Report No. FSEC-CR-1323-03.

Over the past 10 years, researchers at FSEC have worked with the Manufactured Housing industry under the auspices of the U.S. Department of Energy (DOE) funded Energy Efficient Industrialized Housing Program and the Building America (BA) Program (www.buildingamerica.gov). FSEC serves as the prime contractor for DOE’s fifth Building America Team: the Building America Industrialized Housing Partnership (BAIHP) which can be found online at: www.baihp.org.

Data and findings presented here were gathered between 1996 and 2003 during 39 factory visits at 24 factories of six HUD Code home manufacturers interested in improving the energy efficiency their homes. Factory observations typically showed that building a tighter duct system was the most cost effective way to improve the product’s energy efficiency.

BAIHP and others recommend keeping duct system leakage to the outside (CFM25 out) equal to or less than 3% of the conditioned floor area, termed Qn out. However, most homes seen in a factory setting cannot be sealed well enough to perform a CFM25 out test. Results of many field tests suggest that CFM25 out will be roughly 50% of total leakage (CFM25 total). Thus, to achieve a Qnout of less than 3%, manufacturers should strive for a CFM25 total of less than 6% of the conditioned area (Qn total).

Researchers measured total duct leakage and/or duct leakage to the outside in 101 houses representing 190 floors (single wide equals one floor, double wide equals two floors, etc.). Ducts systems observed in these tests were installed either in the attic (ceiling systems) or in the belly (floor systems). Researchers tested 132 floors with mastic sealed duct systems and 58 floors with taped duct systems.

Of the 190 floors tested by BAIHP, the results break down thus:

For mastic sealed systems (n=132):

• Average Qn total = 5.1% (n=124); 85 systems (68%) achieved the Qn total ≤ 6% target.
• Average Qn out = 2.4% (n=86); 73 systems (85%) reached the Qn out ≤ 3% goal.

For taped systems (n=58)

• Average Qn total = 8.2% (n=56); 19 systems (34%) reached the Qn total ≤ 6% target.
• Average Qn out = 5.7% (n=30), more than twice as leaky as the mastic average; 5 systems (17%) reached the Qn out ≤ 3% goal.

The results show that, while it is possible to achieve the BAIHP Qn goals by using tape to seal duct work, it is far easier to meet the goal using mastic. What isn’t illustrated by the results is the longevity of a mastic sealed system. The adhesive in tape can’t stand up to the surface temperature differences and changes or the material movement at the joints and often fails. Mastic provides a much more durable seal.

Typical factory visits consist of meeting with key personnel at the factory, factory observations, and air tightness testing of duct systems and house shells. A comprehensive trip report is generated reporting observations and test results, and pointing out opportunities for improvement. This is shared with factory personnel, both corporate and locally. Often, a factory is revisited to verify results or assist in the implementation of the recommendations.

The most commonly encountered challenges observed in the factories include:

• Leaky supply and return plenums
• Misalignment of components.
• Free-hand cutting of holes in duct board and sheet metal.
• Insufficient connection area at joints.
• Mastic applied to dirty (sawdust) surfaces.
• Insufficient mastic coverage.
• Mastic applied to some joints and not others.
• Loose strapping on flex duct connections.
• Incomplete tabbing of fittings.
• Improperly applied tape

Duct system recommendations discussed in this report include:

• Set duct tightness target Qn equal to or less than 6% total and 3% to outside.
• Achieve duct tightness by properly applying tapes and sealing joints with mastic
• Accurately cut holes for duct connections
• Fully bend all tabs on collar and boot connections
• Trim and tighten zip ties with a strapping tool
• Provide return air pathways from bedrooms to main living areas

Summary of BAIHP Approach to Achieving Tight Ducts in Manufactured Housing:

• Set goal with factory management of achieving Qnout<=3% using Qntotal<=6% as a surrogate measurement while houses are in production.
• Evaluate current practice by testing a random sample of units
• Report Qntotal and Qnout findings; make recommendations for reaching goals
• Assist with implementation and problem solving as needed
• Evaluate results and make further recommendations until goal is met
• Assist with development of quality control procedures to ensure continued success

Finally, duct tightness goals can be achieved with minimal added cost. Reported costs range from $4 to $8. These costs include in-plant quality control procedures critical to meeting duct tightness goals.

Achieving duct tightness goals provides benefits to multiple stakeholders. Improving duct tightness diminishes uncontrolled air (and moisture) flow, including infiltration of outside air, loss of conditioned air from supply ducts, and introduction of outside air into the mechanical system. Uncontrolled air flow is an invisible and damaging force that can affect the durability of houses, efficiency and life of mechanical equipment, and sometimes occupant health. With improved duct tightness, manufacturers enjoy reduced service claims and higher customer satisfaction, while homeowners pay lower utility bills, breathe cleaner air, and have reduced home maintenance.

• Crawl Space Moisture Research for HUD Code Homes
  Research led by David Beal
  Manufactured Home Merchandiser, July 2005

Figure 68 The test units in place. Note white ground cover under unit on left, exposed dirt under unit on right.

When BAIHP started to respond to HUD code manufactures’ floor damage complaints, the diagnosis often pointed to air distribution system leaks which created negative pressure in the house pulling hot, humid, outside air into air conditioned spaces and unconditioned interstitial spaces such as wall and floor cavities.

In some cases this led to condensation and rot. From this research and the resultant recommendations, HUD Code Home manufactures have learned to prevent such occurrences and have dramatically improved distribution system air tightness practically eliminating such problems For background on this matter, see these sections of this report:

• Building Science and Moisture Problems in Manufactured Housing
• BAIHP Field Visits to Moisture Problem Homes
• Manufacturers Participating in Building Science Research
• Duct Testing Data from Manufactured Housing Factory Visits

Successfully sealing HUD code home crawlspaces may be the last piece of the solution for preventing floor failures plaguing homes in hot, humid climates. Merely curing the duct leakage has proven not to enough to keep all floors intact. Proper techniques to seal these crawlspaces need to be developed. The research reported here and BAIHP’s research plan for 2005 addresses this need.

Field Experience

BAIHP researchers have observed that some houses with rotting floors have acceptably tight ductwork, suggesting that factors other than distribution system dynamics are influencing moisture flow. The rot manifests primarily under vinyl flooring which acts a vapor barrier between the conditioned space and floor substrate, which suggests an external source of moisture. BAIHP researchers further observed that the crawlspaces in these homes are damp and musty, often showing signs of standing or running water in the crawlspace.

FSEC concluded that the only uncontrolled moisture source is the humid air in the crawl space of the home driven by vapor pressure toward the cool conditioned space. Several manufacturers address this potential moisture source by requiring a vapor retarder to be placed over the dirt in the crawl space prior to the installation of the house. However, a further exacerbation of the problem stems from the current trend toward extending the siding of the house all the way down to the grade level, in place of the traditional vented skirting. This tends to reduce ventilation, the primary mechanism for dissipating moisture leaching from the ground into the crawls

Other researchers (www.crawlspaces.org) have reported on sealed crawl spaces, and recommended them as a solution to the crawl space moisture problem. The findings from those studies indicate that merely covering the ground without truly sealing the crawl space is not sufficient to solve the problem of high crawl space humidity. The joints and penetrations in the crawl space must be seal to prevent air infiltration as well.

To determine if sealed crawl space solution could be achieved in HUD Code Homes, research needed to be done to address the unique building techniques in that industry, namely the use of vinyl skirting to enclose the crawl space. To that end, in 2004, BAIHP conducted research utilizing two single-wide manufactured houses at FSEC’s auxiliary test site in Cocoa, FL..

The crawl space research plan involved two unconditioned, singlewide manufactured homes sited side-by-side, one home with a ground cover under it, the other without a ground cover (only exposed dirt.). A third identical home was available, however, it was not called into use in this experiment. In each of the two experiment houses, three different skirting (crawl space enclosure) options were evaluated: open or no skirting, perforated skirting, and solid skirting. The solid skirting mimics the effect achieved by extending siding down to the ground instead of stopping it at the band joist, described above. Additional evaluations were planned, however, the Florida’s four hurricanes dramatically curtailed the testing schedule.

The homes (all three) were instrumented with temperature and humidity sensors, two in the crawl space and one in the interior. The site has a weather station, recording ambient conditions. The temperature and relative humidity was used to calculate the dewpoint at the measurement location.

Data Analysis, Interpretation, and Conclusions

The presented data is the ambient dewpoint, the dewpoint of the two crawl spaces. The ambient readings are subtracted from the average of the two crawl space readings to show the temperature difference or )T. The final column of the table (“Difference”) is the difference between the ground cover and the non-ground cover crawl space, showing how much dryer a crawl space with a ground cover is; negative numbers indicating that the ground covered crawl space was dryer.

This data clearly illustrate a potential problem for manufactured houses, or any home on a crawl space. As can be seen, the average crawlspace dewpoint with skirting and no ground cover was over 75 0F. Both crawlspaces with solid skirting were above 76 0F. Any surface in the crawl space that is at or below the dewpoint will condense moisture. Surfaces that could be problematic are exposed floors, A/C ductwork, and plumbing. Also, note that these numbers are averages gathered over at least one week of measurements. The maximums are much higher in all cases, but of a short duration.

The research shows that if a ground cover and perforated skirting are used, the dewpoint in the crawl space will stay near the ambient dewpoint, on average. Often, this is sufficient to avoid problems in homes with crawl spaces. However, if overly cool conditions are maintained in the house (interior temperatures below the ambient dewpoint), problems can still occur.

Research (www.crawlspaces.org) into site built housing with block stem walls has shown that unvented crawlspaces with a ground cover are significantly dryer than vented crawlspaces if they start out as a dry crawlspace or provisions were made to dry them out after completion, such as a dehumidifier or supply air provided to the space. However, the BAIHP data from the “solid skirting and a ground cover” condition do not support this conclusion.

The conclusion is that the solid skirting did not create an adequate seal of the crawl space, allowing significant moisture into the crawlspace. Suspected entry paths for the moisture intrusion were along the joint behind the skirting starter strip, as well as under the molding used to hold the skirting in place at the ground.

HUD code homes (and older site built homes) placed on piers and skirted pose unique challenges to executing the sealed crawl spaces detail. To overcome the air infiltration points associated with skirting described above (at the top and bottom of the skirting) a continuous vapor barrier is needed from the band joist down to and covering the ground. This however would interfere with visual inspect for termite mud tunnels, possibly voiding the termite protection company’s bond. The problem is overcome in crawlspaces with a block walls by stopping the vapor barrier a few inches below the band joist, to allow for inspection.

Planned Research for Summer of 2005

To further research into finding a successful way to seal the crawlspaces of HUD code housing, BAIHP installed a vapor retarder in our on-site, well instrumented, manufactured housing laboratory (MHLab) in March of 2005. The experiment will investigate ways to allow for insect inspection, as well as sealing around penetrations such as piers, anchors, plumbing, and A/C duct work (to package units). The research will also address ways to dry the crawlspace, both from ambient moisture and potential flood problems. This may include a dedicated sump pump and dehumidifier, or the house’s own A/C system.

Air tightness testing of the “sealed” crawl space showed that although the crawl space is much tighter than that provided by solid skirting, it is still too leaky. Further attempts will be made to seal the crawl space by June 2005. When the space is sealed satisfactorily, conditioned air from the house will be introduced into the crawl space and its affect on the humidity level will be monitored.

This BAIHP research has been accepted by the trade journal “Manufactured Home Merchandiser” in an effort to get the information to the people in the manufactured home industry that can alter installation requirements. The anticipated publication date is the July 2005 issue.