Q&A Spotlight

Insulating the Roof of a Bonus Room

Posted on December 2, 2013 by Scott Gibson

Andrew K has a project that should ring a bell with lots of homeowners: What's the best way of insulating a room over the garage so it becomes useful, conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. ?

Andrew lives in Massachusetts, in Climate Zone 5A, and would like to turn the space, what real estate agents used to call a "bonus room," into an office. The roof is framed with 2x8 rafters and already has both soffit and ridge vents, but no insulation whatsoever.

One Minisplit or Two?

Posted on November 18, 2013 by Scott Gibson

Christopher Vernott is an architect at work on his own home — a tight, well-insulated house in southeastern Connecticut — and the time has come to rough-in the heating and cooling system.

Because of the 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. construction, triple-glazed windows, and careful air-sealing, his heating and cooling loads are low, he writes in a Q&A post at Green Building Advisor.

How to Seal Sheathing Boards

Posted on November 4, 2013 by Scott Gibson

The use of plywood and OSB 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. is a fairly recent phenomenon. Before these sheet goodsMaterial, 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. became readily available, builders nailed wood boards to the frame of a house for sheathing, and it is a house with this type of sheathing that Nick Welch is trying to update.

His 900-square-foot house in Climate Zone 4C is sheathed with 1x8 boards, apparently over a layer of asphalt felt. There is apparently no insulation in the wall cavities behind the sheathing. His plan of attack is to air-seal the house, then install foil-faced polyisocyanurate insulation over that. The question is how.

If We Build It, Will They Come?

Posted on October 21, 2013 by Scott Gibson

This Q&A Spotlight starts with a simple question from Anders Lewendal, a builder in Bozeman, Montana. If building to the Passivhaus standard is so cost-effective, Lewendal wants to know, why are only a handful of these houses getting built in the U.S. every year?

"Either the cost of fuel is too low or the cost of 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. is too high," Lewendal writes in a post at Green Building Advisor's Q&A forum.

Rescuing a Problem Cathedral Ceiling

Posted on October 7, 2013 by Scott Gibson

You could call it the $6,500 problem, because that's what it's going to cost Kacey Zach to re-insulate a cathedral ceiling with closed-cell polyurethane foam and hang new drywall.

Writing at Green Building Advisor's Q&A forum, Zach explains the situation: a cathedral ceiling framed with 2x12s and insulated with fiberglass batts to R-38 "with no regard to air sealing."

Upgrading a Shop’s Heating System

Posted on September 23, 2013 by Scott Gibson

Matt Cooper's 1,800-square-foot woodworking shop sits on a 6-inch concrete slab heated with a radiant-floor system. Unfortunately, the on-demand water heater that Cooper uses to heats the water for the in-slab tubing isn't performing well.

"I've been using a Takagi Jr. to heat it for the past couple of years but it's been no end of headaches," Cooper writes in a Q&A post at Green Building Advisor.

How to Install a Foundation Drain

Posted on September 9, 2013 by Scott Gibson

On its face, the location of a foundation perimeter drain seems like the simplest of details. The perforated drain line is run around the foundation next to the bottom of the footing.

At least that's what many construction drawings show. But in some parts of the country, the drain is placed on top of the footing rather than next to it, and this discrepancy is at the root of Steven Knapp's dilemma.

How to Fix an Old Farmhouse Chimney

Posted on August 26, 2013 by Scott Gibson

Between the spalling bricks and a persistent leak that has damaged a mudroom ceiling, the chimney on Page Hyler's 1900 farmhouse is proving to be a problem that just can't get fixed.

What Makes the ‘Best’ Air Barrier?

Posted on August 12, 2013 by Scott Gibson

Bill L. is planning a high-performance house in Massachusetts and is wrestling with options for the air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both., that all-important building detail that enhances both energy efficiency and building durability.

Above-grade walls will consist of a 2x4 structural frame sheathed in 1/2-inch plywood, followed by I-joists packed with cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection., another layer of 1/2-inch plywood, a corrugated plastic product to provide an air space, and fiber-cement siding. The primary air-barrier plane will be at the plywood over the 2x4 studs.

Finding the Insulation Sweet Spot

Posted on July 29, 2013 by Scott Gibson

Anders Lewendal, a builder in Bozeman, Montana, is wrestling with a familiar dilemma: What's the right amount of insulation to put in a house?

"Our theory," he writes in Q&A post at GreenBuildingAdvisor, "is that too little insulation wastes energy and equally, too much insulation wastes energy. Where is the sweet spot in each climate zone?"

To that end, Lewendal is proposing more performance testing.

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