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Innovation’s Next Steps

26 July 2010

You’ve downsized your floor plans, stripped away gables and gingerbread, and accepted razor-thin margins. Now it’s time to truly step out of your comfort zone and try some building methods and materials that can make a real difference.

By: Rich Binsacca
ImageCredit: PETER HOFFMAN

It’s a myth that home building hasn’t changed in a hundred years. Sure, most new homes are still stick-built. But look more closely and you’ll find many incremental, and in some cases wholesale, evolutions in basic products and practices that have improved productivity and performance while reducing costs and cycle time.Taken together, these advances add up to a sea change in how new homes are built. Think of the proliferation of panel products; insulation products created for every nook and cranny; plated roof trusses, wall panels, and other factory-built, snap-together framing components; and today’s far-superior windows and doors that plug what used to be a critical energy leak.

This is just a small sample of the innovations since the mid-20th century that have entered mainstream practice. Their adoption accelerated during the last decade thanks to economic challenges and environmental objectives. Now many builders have seized on technological improvements to set their homes apart from resales and create more margin opportunity in the new economy.

The innovations profiled here are not necessarily new. But they haven’t received wide-spread adoption either. Most are time-tested with solid track records of predictable performance and cost. They can reduce labor and operating costs, distinguish the performance and comfort of your homes, and inspire more interest among buyers. They are worth close examination.

Reconsider Concrete

Bob Cenk, VP Operations for Homecrete Homes, poses on a job site  in Palm City, FLA. Cenk and his company uses ICF's, similar to  giant hollow styrofoam legos, which are filled with concrete to create a  fully-insulated concrete wall. Photo by Josh Ritchie

Bob Cenk, VP Operations for Homecrete Homes, poses on a job site in Palm City, FLA. Cenk and his company uses ICF’s, similar to giant hollow styrofoam legos, which are filled with concrete to create a fully-insulated concrete wall. Photo by Josh Ritchie

Credit: Josh Ritchie

As minimum standards for the performance of a home’s thermal envelope continue to rise (at least for homes to qualify under Energy Star or other green guidelines), the use of next-generation concrete systems for walls, floors, and roof structures is poised for growth.The most obvious (and currently most popular) of these alternatives is insulating concrete forms (ICFs). ICF manufacturers basically combine a handful of wall assembly materialsthey mold expanded polystyrene into interlocking CMU-like blocks or into flat panelsto create site-assembled concrete formwork.

ICF users balance the premium cost of the blocks or panels with faster cycle times. Labor savings may also result because the system relieves subs, with varying skill levels, from trying to cobble together a comparable thermal shell out of advanced stick-framing methods and various insulating, flashing, and air-sealing components.

With ICFs, the result, at minimum, is an R-20-plus wall that is permanently insulated on both sides with a thermal mass (solid concrete) core. The blocks and panels also feature integral nailing strips for attaching interior and exterior finishes and the ability to “let-in” mechanical runs, such as wiring and plumbing, without cutting into the concrete core (wall penetrations should be accommodated before the pour).

A similar technology, if less popular than ICFs, is precast concrete panels for below- and above-grade walls as well as floors and roofs. These panels are typically fabricated in a factory, with connecting rebar stub-ups, door and window openings, and service penetrations made per detailed shop drawings. An integral layer of foam insulation boosts thermal mass.

Precast panels have a proven track record and popularity in the non-residential and multifamily realms, which may help the technology transition into single-family housing construction. They also benefit from their more popular use as a below-grade basement wall system, and from the increasing familiarity among builders who use wood-based panelization to help reduce labor costs and cycle time.

Like their foam-form brethren, precast concrete panels require builders to plan and design to a much higher level of detail than they are used to with stick-framing. They must also come to terms with a different labor pool, local building code resistance (despite allowances in the I-codes), and availability issues caused by a specializedsupply chain of regional manufacturers hampered by shipping restrictions.

For all these reasons, precast has struggled to find a sweet spot in single-family. “If your details are very complex, or you’re just building one home, [your] project is not a good candidate for precast,” says Brian Bock, vice president of sales & marketing for Dukane Precast in Naperville, Ill. “If you are building 10 homes on the same block, it makes more sense.”

Combine Insulation

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The proliferation of specialized insulation products in recent years has created ample opportunity for builders to optimize energy performance. Consider the invention, introduction, and rapid acceptance of new insulation materials and methods, such as expanding foam, rigid panels, acoustical membranes, cellulose, air/vapor barriers, and blown-in-blanket (BIB) systems. The result gives builders the opportunity to combine insulation technologies—suited to climate conditions, of course—to optimize thermal values and manage costs.One area where this hybrid approach can pay dividends is the underside of the roof deck. In hot and humid climates, such as Florida, builders have taken to creating sealed, semi-conditioned attic spaces by spraying closed-cell expanding foam across the entire roof deck to fill every cavity. Though the practice can have a dramatic impact on energy bills, it comes at a price: Closed-cell insulation can cost three times or more than fiberglass batts.

To balance the equation, building scientists advocate that builders apply closed-cell foam only along the joist-deck joints of each roof frame cavity and use BIB fiberglass insulation to fill the rest of the cavity.

The compromise provides for a judicious yet effective use of closed-cell foam’s air-sealing characteristics and higher-density moisture protection in critical areas, namely where the frame and the roof deck meet. It also protects the full R-value of the blown-in fiberglass by removing the threat of incidental flow of air and moisture through the attic structure.

An alternative to closed-cell foam is open-cell foam. Similar in its application, open-cell costs less, but it is less dense and thus less thermally efficient than closed-cell. Its expansion also is harder to control, and the expanded (hardened) foam is more easily compressed than closed-cell. For those reasons, open-cell foam is not recommended for a hybrid approach, but is okay to use by itself to fill the entire framed cavity.

For wall assemblies, especially ones designed to meet stricter thermal envelope standards, a hybrid insulation approach may include coupling a cellulose or BIB system for the wall cavities (filling them completely, including around foam-sealed mechanical penetrations, to maintain optimum R-value) with joint-sealed rigid foam panels and perhaps an air/vapor barrier on the other side of the wall studs, behind the finish cladding, to create a tight envelope.

Optimize HVAC

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Like ICFs and hybrid insulation, new-age heating/cooling and ventilation systems can lower a home’s energy consumption and improve indoor air quality. They may also help reduce the size and lower the cost of the HVAC equipment. For example, using heat- and energy-recovery ventilators (HRVs and ERVs) to supplement a central heating and cooling system may allow you to “right-size” the equipment to reduce their cost and actually achieve better indoor comfort.Simply, HRVs and ERVs intercept return airflow and capture its heat. That heat is transferred to the incoming fresh (or supply) air—brought in through the HRV/ERV unit—before it reaches the furnace (see illustration, right). This reduces the energy needed by the furnace to bring incoming air up to the temperature set on the thermostat.

Because it is the conduit for fresh air into the house, an HRV or ERV provides a balanced, controlled, and measured flow of fresh air into the house, while its filtration system blocks airborne pollutants before they reach conditioned space. For humid climates, ERVs feature a separate chamber to manage humidity levels in the air exchange.

Though not specifically called out or required, HRVs and ERVs are likely to become the “default” specification to meet the 2011 Energy Star Qualified Home program standard for controlled, fresh-air ventilation. Already, both the National Green Building Standard and LEED for Homes rating systems award extra points for the use of the technology.

Another evolving HVAC technology is MicroCHP, or combined heating and power systems for residential (“micro” or small-scale) environments. Simply, MicroCHP or “cogeneration” systems use an internal combustion engine, usually fueled by an on-site propane tank, to generate heat and also run an internal electrical generator.

As its engine produces heat, the MicroCHP captures and transfers it to a conventional central air-system blower for space or domestic water heating. A typical system produces a thermal (or heating) output of approximately 12,000 BTU/hr., plenty of heat to serve a home’s hot water needs (especially when using tankless units).

In addition, a typical unit (about the size of a conventional outdoor air-conditioning condenser) generates about 1200 watts of electricity to help offset the grid-supplied power. The electricity also can be leveraged to recharge the battery bank of an on-site photovoltaic (solar electric) array if that system is not tied to the electrical service meter, or as a more energy-efficient pool and spa heater.

Rethink Wood

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Make no mistake: composite decking materials—which combine recycled or waste-wood fibers and reclaimed plastics to form planks and other components—are the Cadillacs of low-maintenance exterior wood products.Installed over a properly engineered structural frame, the planks don’t absorb moisture, fade only slightly (depending on the original hue), and maintain their dimensional integrity and stability without water-seal treatments or other care requirements.

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A lesser-known but perhaps even more effective use of the same technology has been applied to window and door frames since the mid-1990s—though most builders wouldn’t know it because it is most often concealed in vinyl or aluminum cladding.With such a long track record and integration into manufacturing processes, a window or door with an engineered-wood frame is not likely to carry a significant cost premium compared to other wood-clad units, though they are slightly higher in price than all-vinyl alternatives. And yet, they out-perform other window frame materials in almost every way.

In addition to being a natural insulator, the denser wood-based material better resists the effects of changing climate conditions. A composite frame won’t shrink or swell depending on the season, significantly reducing the potential for air leaks through its connection to the wall studs and header, a thermal and indoor air quality benefit, while preserving smooth sash operation (and higher homeowner satisfaction).

Add to that the fact that composite wood frames are made from pre- and post-consumer recycled material and can be recycled themselves, and you have a solid environmental story to sell, as well.

Higher Ground

Looking beyond the next steps? Keep an eye on these technologies and practices:

  • ICF Floor and Roof Panels System designs and installation methods vary from pour-in-place to crane-in-place, but at R-3.8 per inch and with significant sound attenuation benefits, the ability to apply the labor savings and thermal qualities of ICFs across the entire building envelope is an attractive prospect.
  • Phase Change Materials These bio-based thermal mass products help regulate indoor temperatures and lessen the energy load on HVAC equipment. One manufacturer markets a barrier mat applied between the stud wall cavity insulation and the drywall to absorb and slowly release heat that gets through the structure from the outside.
  • Sorghum Fiberboard The source of this agricultural waste product grows rapidly and in arid climates. When used in fiberboard panels, its high cellulose content makes it lightweight, pliable, and strong enough for subflooring, door cores, and cabinet boxes, and it doesn’t need a laminated finish.
  • Ductless Mini Split Systems These slim, wall-mounted units blow hot or cold air into a space without using ducts. An inside unit connects to a small cooling unit or heat pump outside to serve a 400-square-foot area and supplement or, in a multiple-zone scheme, replace a centralized system.
  • Manifold Plumbing A centralized scheme for domestic water distribution uses flexible crosslinked polyethylene supply lines run from a multiport manifold to individual fixtures, reducing labor costs, offering higher insulating and heat-loss values, boosting overall water pressure, and enabling better service access. Mini-manifolds can service remote fixture groups.

— Looking beyond the next steps? Keep an eye on these technologies and practices:

Rethink Wood

Image

Make no mistake: composite decking materials—which combine recycled or waste-wood fibers and reclaimed plastics to form planks and other components—are the Cadillacs of low-maintenance exterior wood products.Installed over a properly engineered structural frame, the planks don’t absorb moisture, fade only slightly (depending on the original hue), and maintain their dimensional integrity and stability without water-seal treatments or other care requirements.

Image

A lesser-known but perhaps even more effective use of the same technology has been applied to window and door frames since the mid-1990s—though most builders wouldn’t know it because it is most often concealed in vinyl or aluminum cladding.With such a long track record and integration into manufacturing processes, a window or door with an engineered-wood frame is not likely to carry a significant cost premium compared to other wood-clad units, though they are slightly higher in price than all-vinyl alternatives. And yet, they out-perform other window frame materials in almost every way.

In addition to being a natural insulator, the denser wood-based material better resists the effects of changing climate conditions. A composite frame won’t shrink or swell depending on the season, significantly reducing the potential for air leaks through its connection to the wall studs and header, a thermal and indoor air quality benefit, while preserving smooth sash operation (and higher homeowner satisfaction).

Add to that the fact that composite wood frames are made from pre- and post-consumer recycled material and can be recycled themselves, and you have a solid environmental story to sell, as well.

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