Housing the people: Modular passive homes emerge

{"version":"0.3.0","atoms":[],"cards":[],"markups":[["a",["href","https:\/\/www.beracahhomes.com\/","target","_new"]],["a",["href","http:\/\/greenhaus.wpengine.com\/passive-houses\/","target","_new"]],["em"],["a",["href","http:\/\/greenhaus.wpengine.com\/passive-houses\/http:\/\/greenhaus.wpengine.com\/passive-houses\/","target","_new"]],["strong"]],"sections":[[1,"p",[[0,[],0,"On an August morning in the\nFairmount Heights neighborhood in Maryland, two prefabricated units sat in a\nparking lot ready to be transported down the street. They were to be lifted\nonto a carefully constructed foundation on a site in the residential community."]]],[1,"p",[[0,[],0,"The units had arrived on\ntrucks to this community just outside Washington, D.C., from the factory in\nDelaware where they had been prefabricated. One unit was the first floor, which\nwas lifted into place in 90 minutes. The other was the second floor unit, which\nhad to have the roof \u201cunfolded\u201dand the eave overhangs\nattached. These last two steps took place on site so the second story could be\ntransported from Delaware to Maryland more easily."]]],[1,"p",[[0,[],0,"From the outside, the units\nlooked like simple wood-framed volumes wrapped in the characteristic green of\nthe Huber ZipSystem sheathing, with taped joints, installed windows and the\nroof fully shingled. On site, prefabricated knee walls were installed and gable\npanels lifted into place. In less than eight hours, the 1,600-square-foot\nhouse was ready for the electrician, plumbing and mechanical contractors to\ncome and make their connections."]]],[1,"h3",[[0,[],0,"Inception"]]],[1,"p",[[0,[],0,"\nAt the end of June, "],[0,[0],1,"Beracah\nHomes"],[0,[],0," in Greenwood, Delaware, began construction of its first modular passive house.\nPassive building consists of a set of design principles used to attain a\nquantifiable and high level of energy efficiency within a specific comfort\nlevel to heat and cool the building."]]],[1,"p",[[0,[1],1,"David Peabody Architects"],[0,[],0," had\nbeen contacted by the Housing Initiative Partnership (HIP) a nonprofit\ndeveloper based in Prince Georges County, Maryland. HIP is dedicated to\nrevitalizing neighborhoods and creating home ownership programs for low and\nmoderate income families. It has been providing single family homes for sale\nand multifamily homes for rent to families since 1988. Since the early 2000s,\nHIP has included sustainability as a part of its commitment to providing high\nquality projects, but it had never built a modular or a passive house before."]]],[1,"blockquote",[[0,[2],1,"Peabody believes that there\u2019s a lot of potential for building modular passive house duplexes and\nfourplexes that could compete in a subsidized housing sector."]]],[1,"p",[[0,[],0,"\n\n\n\n\u0004Jocelyn Harris of HIP procured a\ngrant from the State of Maryland to build their first passive house. Maryann\nDillon, the executive director for HIP, had previously toured the Habitat for\nHumanity \/ Parsons School of Design Empower passive house entry in the 2011 DC\nSolar Decathlon. There she had been introduced to David Peabody and O\u2019Neill Development, Inc."]]],[1,"p",[[0,[],0,"After receiving the grant\nto build a passive house, HIP selected Peabody to execute the project, and he\nproposed using modular construction. Peabody is a certified passive house\nconsultant, and his office had previously designed and built two custom passive\nhouses in Bethesda and Rockville, Maryland. The Bethesda project was a spec\nproject in partnership with O\u0027Neill Development, and the one in Rockville was a\nprivate commission."]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"This project presented the\nnew challenge of being a modular house designed to be affordable to a lower\nincome buyer, a construction process of which Peabody Architects had no\nfirst-hand experience. After researching modular construction companies,\nPeabody decided to partner with Beracah Homes. Beracah had been building Energy\nStar homes and took this challenge."]]],[1,"h3",[[0,[],0,"Fabrication and Construction"]]],[1,"p",[[0,[],0,"The fabrication of the house\nstarted in the factory at Greenwood and the construction of the foundation,\nrelated site and utility work took place in Fairmount Heights. The framing\nincorporated new, nonstandard features into the construction such as double\nwall studs filled with Densepack fiberglass insulation."]]],[1,"p",[[0,[],0,"Passive Buildings must\nincorporate the following:"]]],[3,"ul",[[[0,[],0,"Continuous insulation\nthroughout its entire envelope;"]],[[0,[],0,"No thermal bridging;"]],[[0,[],0,"Extremely airtight envelope\n(.6ACH@50Pascale);"]],[[0,[],0,"High-performance windows\n(typically triple glazed) and doors;"]],[[0,[],0,"A balanced heat and\nmoisture recovery ventilation system to provide constant filtered fresh air\nwhen the house is closed and in the heating or cooling mode. "]]]],[1,"p",[[0,[],0,"For certification, proprietary\nenergy modeling software is used to determine a building\u0027s energy use. Passive houses\nuse, on average, 15% of the energy for heating and cooling as a house of the\nsame size built to code. Some details of the assembly for the modular passive\nhouse are listed below. For more technical information about the project please\nvisit "],[0,[3],1,"David Peabody Architects"],[0,[],0,"."]]],[1,"h3",[[0,[],0,"The Modular Passive House Combination"]]],[1,"p",[[0,[],0,"David Peabody believes that\nmodular construction can bring the price of passive houses down within reach of\na wider population, creating a larger market for these super-efficient houses.\nThis house is the prototype putting that idea to the test."]]],[1,"p",[[0,[],0,"The team faced many\nchallenges developing the prototype. An overarching construction goal was to\nconstruct as much of the house in the factory as possible to shorten the\nschedule and control the energy performance."]]],[1,"p",[[0,[],0,"Peabody, with his associate\nIzumi Kitajima, who\u2019s also certified as a passive house consultant,\nstudied Beracah\u0027s production methods and developed building envelope details\nthat would work with those methods."]]],[1,"p",[[0,[],0,"For the next project, the\nhighly iterative drawing process of this project will not be necessary and the\ngoal will be that the design, permit and fabrication drawings will all be the\nsame drawing set!"]]],[1,"p",[[0,[],0,"Similarly, the construction\nof the next building will incorporate efficiencies that the prototype did not\nhave. The prototype was delivered to the site with a completely finished\ninterior; plumbing fixtures and bathroom mirrors were already installed but the\nexterior had only been completed to the sheathing so if the house did not pass\nthe blower test, any leaks could be much more easily sealed than if the house\nhad the exterior finish already installed.\n\n\n\n\u0003\b"]]],[1,"p",[[0,[],0,"Beracah had paid such\nmeticulous attention to detail that the first test performed by Conway Energy\nhad a result of .65ACH50Pa (air changes per hour at 50 pascals of pressure).\nWith some minor reparations and additional sealing, the house easily exceeded\nthe passive house standard of 0.60ACH the equivalent of a single 2 3\/4\u201ddiameter hole in the envelope. The second test\nresult was even better. Passive houses are 10x more airtight than an Energy\nStar home and 20x more airtight than a standard code-minimum home."]]],[1,"p",[[0,[],0,"The house was cooled using\na window unit, and the temperature difference was only 8 degrees. The greater\ndifference in temperature yields higher contrast images from the thermal\nimaging camera. The leaks found in the first test were due to some minor\nmistakes, which were easily rectified; a few joints were taped again that had\nbeen damaged by foot traffic and some penetrations that had to be made on site\nwere only sealed with foam and needed to be taped.\n\n\n\n\u0003\b"]]],[1,"p",[[0,[],0,"There were other challenges\nwith the prototype. Detailing of a modular home has to take into account the\nshipping of the completed units and this can change the detailing."]]],[1,"p",[[0,[],0,"When asked about this\nchallenge, David Peabody said, \u201cit requires having both a floor and a ceiling on\nevery unit, so between every floor you have not only floor joists but ceiling\njoists. Modular construction is done from the inside out rather than the\noutside in as in traditional stick-built construction. That required us to\nrethink where the air barrier would be placed (exterior sheathing surface).\nSimilarly the roof had to be hinged and shipped down the road in a way that it\ncould be erected in the field."]]],[1,"p",[[0,[],0,"That required figuring out\nhow to make sure the hinges didn\u0027t penetrate the air barrier and how to break\nthe thermal bridging at the hinges and how best to insulate that attic space.\nThere were just a lot of places like that where we had to scratch our heads to\nfigure out how to insulate and seal and still keep this standard factory\nconstruction.\u201d"]]],[1,"h3",[[0,[],0,"Future"]]],[1,"p",[[0,[],0,"Peabody believes that there\u2019s a lot of potential for building modular passive house duplexes and\nfourplexes that could compete in a subsidized housing sector, where the ratio\nof exterior envelope to net square footage of the building is lower. Peabody\nArchitects has taken what it has learned from this experience building passive houses\nand is now applying them to deep energy residential\nretrofits. It is pursuing passive house certification of a landmark\nbuilding in Washington, now under way."]]],[1,"p",[[0,[],0,"HIP is trying to justify\nthe 17% greater hard costs of the project over a comparable project using\ntraditional building methods. These costs are primarily in the envelope, double\nstuds, triple glazed windows and a solar hot water heater, which pushes the rate\nof return to over 14 years. The expectation is that the next project would cost\nless than the prototype, but the costs are unlikely to come down to make it\nbeneficial for the client."]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"The ability to shorten the\nschedule and control the quality of construction makes the modular model very\nappealing despite the limited standard interior finishes on offer. They will\nalso consider using an energy recovery ventilator in future projects since this\nis so beneficial to the indoor air quality. The three largest expenses for the\nclients are mortgage payments, transportation costs, and utility bills, so HIP\nwill continue to study ways to make the homes less expensive to heat and cool."]]],[1,"p",[[0,[4],1,"About the Author"]]],[1,"p",[[0,[2],1,"Pamela Sams, AIA, is a technical director at the Washington, D.C. office of Gensler."],[0,[],0," \n\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n\n\n\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]],[1,"p",[[0,[],0,"\n\n\n\n"]]]]}