techdirections April 2013 : Page 21
By David Enos DEnos@humboldt.k12.ca.us D ESIGNING and building homes is normally the responsibility of a profes-sionally trained work-force. So a lot of people are skeptical about the idea of a team of high school students taking on those tasks. Would a young, un-trained group of students be able to undertake and successfully complete the construction of an entire home, from start to ﬁnish? The Humboldt County Ofﬁce of Education, located on the North Coast of California, has been supporting teams of teenagers who do just that. In fact, students attending classes in the Northern Humboldt Union High School District recently completed an ambitious two year model/demon-stration house-building project. The energy-efﬁcient house (shown on the cover) was designed in the drafting classroom and built on a site near the school by students enrolled in the county’s Regional Occupational David Enos is an architectural design/building trades and computer-aided drafting instructor, Arcata (CA) High School. Program’s building trades class. This article describes how they did it. Getting Started The construction teams were made up of students from the dis-trict’s two high schools, Arcata and McKinleyville. They began the school year with classroom instruction that included a discus-sion of safety rules, tool identiﬁcation and usage, and construction ter-minology. Instruc-tors used a scale model house to show the students house construction components and to reinforce the application of the construction termi-nology. Our ﬁrst hands-on activity involved constructing a set Students pour the slab foundation perimeter. of saw horses. Us-rived at the work site with their own ing an existing set of saw horses as sets of hand tools, which were on an example, each team of two stu-loan from the building trades class dents drew a sketch of their design, came up with a materials/cut list, and then built their saw horses. The saw horse project was a great way for us to evaluate each student’s current level of ability. Then, we announced that we would take a rather large step for-ward for our second project: It was time to build a house. Students ar-www.techdirections.com CONSTRUCTION 21
Building a Green House in the Redwoods
DESIGNING and building homes is normally the responsibility of a professionally trained workforce. So a lot of people are skeptical about the idea of a team of high school students taking on those tasks. Would a young, untrained group of students be able to undertake and successfully complete the construction of an entire home, from start to finish? The Humboldt County Office of Education, located on the North Coast of California, has been supporting teams of teenagers who do just that.
In fact, students attending classes in the Northern Humboldt Union High School District recently completed an ambitious two year model/demonstration house-building project. The energy-efficient house (shown on the cover) was designed in the drafting classroom and built on a site near the school by students enrolled in the county’s Regional Occupational Program’s building trades class. This article describes how they did it.
The construction teams were made up of students from the district’s two high schools, Arcata and McKinleyville. They began the school year with classroom instruction that included a discussion of safety rules, tool identification and usage, and construction terminology. Instructors used a scale model house to show the students house construction components and to reinforce the application of the construction terminology.
Our first handson activity involved constructing a set of saw horses. Using an existing set of saw horses as an example, each team of two students drew a sketch of their design, came up with a materials/cut list, and then built their saw horses. The saw horse project was a great way for us to evaluate each student’s current level of ability.
Then, we announced that we would take a rather large step forward for our second project: It was time to build a house. Students arrived at the work site with their own sets of hand tools, which were on loan from the building trades class tool inventory. All power tools and other construction tools and equipment were already on site, stored in an 8' ?? 8' ?? 20' steel storage container. Additional tools and supplies were stored at the school facility.
On-Site, Hands-on Education
The majority of the school-year training was spent at the building site listening to instructions, watching demonstrations, and—the fun part—building the house.
After locating the property corners, students set stakes and ran string lines to lay out the property borders. The next step was locating batter boards, more string lines, and checking for set-backs. The Pythagorean theorem came into play for squaring the foundation. Students found themselves putting their math skills to work in a real-life setting.
After lining out the slab foundation perimeter, we started digging the house footings with a backhoe. Footings cleaned and inspected, we began forming the perimeter for the outer stem wall.
Running the plumbing waste lines was next on the agenda. Pipe sizing, using the correct fittings, and keeping the proper fall for the piping can be tricky business. There is little room for error and the students did a great job running the lines and passing inspection on their first attempt. Once the stem wall was poured, we lined the inside of the slab with a 15 mil vapor barrier (no penetrations). Two inches of closed-cell insulation was placed over the water-tight barrier and hydronic-heating PEX tubing was placed over the insulation. Half-inch rebar at 24" O.C. was located in the middle of the 5" concrete slab. A 1/2" thermal break insulation barrier was installed between the stem wall and the floating slab.
The home’s passive solar design uses the concrete slab as a storage heat mass to assist in heating the home.
House framing began after serious discussion and hands-on demonstrations. Terminology, rough opening sizes, and stud layout were the primary focus of our discussions. Teams were assigned a wall area to begin their framing education. We used nail pullers to make minor adjustments to the framing team’s first few layouts. Framing, stair building, wall sheathing, and cutting roof rafters was the training sequence.
As we progressed through the year, the young carpenters moved fairly smoothly through the learning/ building process. Window installation and closing in the house’s door openings completed the first year’s construction schedule.
The second year picked up with siding the house and beginning the inside work. The house was the classroom and students were involved in every aspect of the construction process. We worked with many construction professionals who donated time and money to help with training the student workforce. The students performed over 90% of the work necessary to complete the project, but the assistance from many of our local tradesmen helped ensure the project’s success.
The construction team used many energy-saving features, materials, and mechanisms to build an energy-efficient, practical, healthy home:
• Passive solar design—Most of the windows are located on the south and west sides of the house. The first story stained concrete (storage mass) and slate are heat-absorbing surfaces, designed to assist in heating the home. The design uses daytime natural lighting to minimize the lighting energy needs.
• In-floor hydronic and domes-tic water heating—The home is heated with a 96% efficient natural gas, condensing water heater. The hydronic heating system creates no dust and uses the natural convection properties of warmed air to circulate heat. PEX tubing and individual room thermostats allow for heat to be delivered to only the rooms designated to be heated. The plumbing/electrical mechanical closet is centrally located in the home, allowing for short plumbing runs. Short plumbing runs allow for lower energy usage and reduced water consumption when transferring heated water. We installed low-flow water fixtures to limit water and energy consumption.
• Insulation—Exterior wall cavities are a full 6" thick and filled with ULTRAFIT-DS fiberglass blown-in insulation. The students sealed all wall cavities between the studs and exterior sheathing, reducing air infiltration. They placed half–inch closed cell insulation strips between the interior stud wall and the interior drywall on the house’s exterior walls. This thermal break lessens the heat loss created by conduction through the studs and the drywall.
The second story floor is insulated on the lower side of the floor joist. This insulation provides an oven-effect cavity for the upper floor hydronic in-floor heat system as well as a sound barrier between floors. The blown-in attic insulation has an R-38 rating. Each room is insulated between common walls to reduce sound transmission. The first story 5"-thick slab is insulated with 2" rigid foam. A 15 mil vapor barrier protects the slab from moisture infiltration.
-Solar photovoltaic system—The roof-mounted, 12-panel solar array is rated at 2.33 kW and should generate over 10 kW of power each day. The system uses Enphase Micro Inverters to convert dc power to ac. The gridtie system uses a bi-directional meter that connects to the local utility company. The meter spins in reverse when electrical production exceeds demand. The system should generate enough electricity to meet most of the home’s electrical energy needs. The system can be monitored on site and online to view its energy production at any given time.
-Heat recovery ventilator—The heat recovery ventilator (HRV) is designed to replace indoor air with fresh outdoor air on a 24/7 schedule.
The attic location of the HRV unit allows the ducting to pull in outside air from the west side of the home to bring fresh air into the three bedrooms and family room and to pull exhaust air from the kitchen and two bathrooms. The exhaust air pre-heats the fresh, incoming air and re-captures 80% of the heat energy from the exhaust air. The system is designed to completely replace all of the home’s air with fresh air once every three hours. Air-tight homes need to be mechanically ventilated to provide fresh, healthy air for the homes’ occupants.
• Windows and sliding glass doors—The house was built using Andersen vinyl windows and sliding glass doors with dual-paned glass. The windows and doors are Energy Star rated. Andersen uses recycled materials to build the frames for their vinyl window and door products. The vinyl has a 40% recycled content rating and the glass has a 13% recycled content rating.
• Lighting and electrical—The home’s lighting fixtures use is either light-emitting diode (LED) or compact fluorescent (CFL) bulbs. This type of lighting requires a very low energy demand and will also greatly extend the replacement interval. The electric subpanel is in a centrally located interior mechanical closet, which makes the circuit breakers readily accessible. The short electrical circuit line lengths reduce wire run lengths and materials used.
Each room has multiple phone and cable connection points for Cat-7 and coaxial cables. All cabling runs terminate in the structured media center hub that is located in the garage. This centralized media center allows for all of the home’s current and future communication needs to be upgraded from one convenient location.
The ceiling fan keeps the home’s air moving and assists in distributing the heated air throughout the house. The refrigerator wall area has a smart-wire connection port to be used with “Smart Fridge” technology.
• Indoor air quality—The home was painted with green label low- VOC paint. The carpet is 100% BCF (bulk continuous filament) polyester. The carpet pad is approved by the Green Building Council and exceeds the CRI indoor air quality standards. Cabinets were built with solid cherry wood and plywood and contain no formaldehyde off-gassing products.
• Appliances—All kitchen appliances are LG brand. The all-stainless steel dishwasher is one the quietest on the market and is Energy Star rated. The microwave doubles as a ventilation fan and exhausts kitchen cooking fumes and odors to the outside of the house. The electric range has self-cleaning and convection oven capabilities. (Convection ovens cook at lower temperatures and require shorter cook times than conventional ovens.) The electric range option was taken to utilize the solar PV system’s electricity-generating capabilities.
• Energy efficiency—The home has been designed to surpass the California Title 24 energy efficiency standards by more than 22%. This high-efficiency rating qualifies the home for the PG&E Solar Homes Partnership Program. A small number of homes are able to qualify for this program due to the difficulty of reaching the efficiency standard.
House Style and Other Features
The Craftsman-style house design includes:
• Custom rafters and gutternotched rafter tails,
• Custom door and window trim elements,
• Exterior brick porch entry and brick columns,
• Stained concrete floor (heat storage mass),
• Slate floor and baseboard,
• Granite countertops,
• Cherry cabinets with pull-out trays, soft-close hinges and slides,
• Corner cabinet recycling carousel,
• Professionally designed and installed landscape, including automated sprinklers and drip irrigation systems,
• West-facing, ocean view deck,
• James Hardie concrete-fiber, horizontal siding, and
• Quality door hardware and Smart-Key lockset technology.
On completion of each school year, most students have accumulated tool credits. Each day’s credit is added up each week and totaled at the end of the year. Students add to their tool credit account by showing up every day, on time, ready to work.
If a student is late to class, leaves a tool out, has a safety violation, or is just goofing off, he or she loses that day’s pay and an additional sum, depending on the offense. Students can earn extra pay/credit by working after class or weekends to assist with various construction duties. Top students have had in excess of $1,000 of tool credits at the end of the school year.
At the end of each school year, students leave the program with a wealth of knowledge, construction experience, and their own tools. We assist the serious, hard-working, and interested-in-construction students in finding a job in the construction trades with one of the many local building contractors who are looking for good workers. A number of students from previous years’ classes have become contractors, engineers, and construction workers, either locally or outside the area.
While we are very proud of the work the students and our tradesmen have accomplished in building green houses, our most important mission is to train today’s youth to become skilled, hard-working, responsible, and successful adults. Whether the students decide to pursue a career in construction or another profession is not the key concern. What is important is for the graduates to see how they can use their own individual and unique skills to explore and follow their particular career path.
Educational opportunities can be packaged in a variety of ways. We need to continue to help today’s students find their niche. If we can help them find a career that they are passionate about, their chances of getting and keeping a job will be greatly improved. If we keep them motivated enough to keep the learning process moving forward, their chances of achieving success in adult life will be greatly improved. Their future—and our future—depend on it.
Read the full article at http://www.omagdigital.com/article/Building+a+Green+House+in+the+Redwoods+/1345348/150954/article.html.
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