Q&A Spotlight

Building With Steel Framing

Posted on January 21, 2013 by Scott Gibson

Sal Lombardo is planning a new home in the New York-New Jersey area (Climate Zone 5) and is looking at a long list of high-performance construction options: double-stud walls, structural insulated panels, insulating concrete forms, Larsen trusses, and walls built with light-gauge steel framing.

Wait a minute. Steel framing, as in the stuff that leaks heat through the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials. like a proverbial sieve? Maybe, Lombardo says, it deserves another look.

Is There an Alternative to a Heat-Recovery Ventilator?

Posted on December 17, 2012 by Scott Gibson

The tighter the house, the more it needs mechanical ventilation. That's become a rule of thumb for energy-efficient builders, and designers often turn to heat-recovery ventilators to get the job done. These relatively simple (but not necessarily cheap) devices use the temperature of outgoing air to moderate the temperature of incoming air, thus lowering the energy penalty for providing fresh air to the whole house.

Walls Without Water-Resistive Barriers

Posted on November 26, 2012 by Scott Gibson

Unless a builder has opted for a Zip System wall or is willing to ignore building code requirements, a layer of housewrap or building felt typically covers any exterior sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. before the siding is applied. This water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material., or WRB, helps to protect the sheathing from damage in the event that water is driven past the siding.

Do Europeans Make Better Windows Than We Do?

Posted on October 15, 2012 by Scott Gibson

It should come as no surprise that Europe, home of the Passivhaus standard, produces some outstanding windows. Some builders of high-efficiency houses in North America turn to European window manufacturers for their glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill., even though some U.S. and Canadian producers also offer high-performance products of their own.

Is there a way to compare the performance data on windows from these two sources? That’s what Steve Young, now planning a Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. in Climate Zone 5, would like to know.

Vapor Barriers Redux

Posted on September 24, 2012 by Scott Gibson

Few topics in building science seem to have caused as much confusion as the use of a polyethylene vapor barrier in exterior walls.

Once routinely used by builders to prevent the migration of interior moisture into wall cavities, polyethylene is no longer recommended for houses unless they’re built in extremely cold climates.

Are Seven Heads Better Than Three?

Posted on August 20, 2012 by Scott Gibson

John Bell, building a 3300-sq. ft. house in eastern Pennsylvania, is weighing his options for heating and cooling, and it comes down to a conventionally ducted air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. or a multi-head ductless minisplit system made by Fujitsu.

Air-Source or Ground-Source Heat Pump?

Posted on July 9, 2012 by Scott Gibson

Dana is building a tight, well-insulated house in climate zone 6 and now faces a choice between a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures. and an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. for heating and cooling.

“After the 30% tax incentive, there is not much increase in cost for the geo system,” Dana writes in a Q&A post at GreenBuildingAdvisor. “I am being told different stories in regard to system performance and longevity of equipment (depending on what side of the fence you’re on).”

Choosing a Cost-Effective Wall System

Posted on June 18, 2012 by Scott Gibson

Erik Olofsson is planning a small house in the Rocky Mountains of British Columbia. Ideally, he’d like to get the walls close to R-40. The question is how.

“Seeing that the received opinion around GBAGreenBuildingAdvisor.com is the tandem of polyethylene sheeting and exterior rigid foam is not ideal, what do the builders on this site recommend?” he asks in a post at the GBA Q&A forum. “Larsen trusses seem fairly labor-intensive and rigid foam is expensive ... Is a double-stud wallConstruction system in which two layers of studs are used to provide a thicker-than-normal wall system so that a lot of insulation can be installed; the two walls are often separated by several inches to reduce thermal bridging through the studs and to provide additional space for insulation. the answer?”

Staying Cool with a Metal Roof

Posted on May 21, 2012 by Scott Gibson

David Martin is intrigued with the idea of replacing his existing roof with a standing-seam metal roof. It should last longer than the alternatives, he says, and it would be compatible with photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. panels should he decide to add them in the future.

So what’s the issue?

David Martin is troubled by some of the advertising claims he’s seen about metal roofing, specifically a statement from the Metal Roofing Alliance that a “cool metal roof can save 25% in energy costs compared to a dark grey asphalt shingle.”

Can Vinyl Siding be Applied Over Furring Strips?

Posted on April 18, 2012 by Scott Gibson

Wall assemblies that incorporate rigid foam insulation over exterior sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. , followed by furring strips and siding, are becoming common. The extra layer of insulation helps reduce thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. through wood framing, and the furring strips create a ventilation space behind the siding that promotes drying.

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