Musings of an Energy Nerd

The 2012 Code Encourages Risky Wall Strategies

Posted on July 18, 2014 by Martin Holladay, GBA Advisor

Builders who follow the prescriptive requirements of the 2012 International Residential Code (IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.) in Climate Zone 6, 7, or 8 are required to install a minimum of “20+5 or 13+10” wall insulation. What does this mean? According to an explanatory footnote in the code, the “First value is cavity insulation, [and the] second is continuous insulation or insulated siding, so ‘13+5’ means R-13 cavity insulation plus R-5 continuous insulation or insulated siding.”

Every House Needs Roof Overhangs

Posted on July 11, 2014 by Martin Holladay, GBA Advisor

Many residential designers pay too little attention to roof overhangs. Roof overhangs have several important functions: they can protect exterior doors, windows, and siding from rain; they can shade windows when solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. is undesirable; and they can help keep basements and crawl spaces dry. A house with improper overhangs can overheat in the summer, can suffer from water entry problems at windows and doors, and can have premature siding rot.

The most common design error is to make roof overhangs too stingy. It’s also possible (although much rarer) for roof overhangs to be too wide.

South-Facing Skylights: Threat or Menace?

Posted on July 10, 2014 by Martin Holladay, GBA Advisor

There are two kinds of sunrooms: those that have sloped 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. and those that have only vertical glazing. Sunrooms with sloped (or in some cases, curved) glazing are more common (and, of course, more uncomfortable). In order to make sure that these rooms are sunny, they are often located on the south side of the house.

Polyethylene Under Concrete Slabs

Posted on July 4, 2014 by Martin Holladay, GBA Advisor

What goes under the concrete in a slab-on-grade home? In the old days, not much — just dirt. Eventually, contractors discovered that it made sense to include a 4-inch-thick layer of crushed stone under the concrete. The crushed stone provides a capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. break that reduces the amount of moisture flowing upward from the damp soil to the permeable concrete.

Since the crushed stone layer provides a fairly uniform substrate, it also may also reduce the chance that a concrete slab will be poorly supported by random pockets of soft, easily compressible soil.

Banish These Details From Your Plans

Posted on June 27, 2014 by Martin Holladay, GBA Advisor

Is it possible to disassemble old shipping pallets and glue the pieces of lumber together to make furniture? Of course it’s possible; some woodworkers have used this method to make beautiful tables and chairs. There’s a fly in the ointment, however: while it’s possible, it’s not very easy.

Many commonly used construction methods, design details, and materials fall into a category I would call “possible but not easy.” I decided to create a list of items that fall into this category.

How Balanced Ventilation Systems Become Exhaust-Only

Posted on June 20, 2014 by Martin Holladay, GBA Advisor

Unlike the homes of our great-grandparents, the homes of most Americans are served by an array of automatic appliances and systems.

When our great-grandparents returned home after a three-day absence, they would need to haul a bucket of water from the spring and light a fire in the kitchen stove before they could brew tea. Today’s homes, of course, have electricity for lighting, a furnace for warmth, an air conditioner for cooling, a water heater for showers, and internet access for Googling.

Universal Design

Posted on June 13, 2014 by Martin Holladay, GBA Advisor

Why are most interior doorways only 30 inches wide? Why are so many doorknobs hard to grip? And why do so many homes have a long stairway between the front door and the bedrooms?

Two typical answers to these questions would be, “because that’s the way we’ve always built houses” and “because these houses meet code.” (Those two reasons happen to be pretty weak, by the way.)

Vermont House Uses Only Half a Cord of Firewood

Posted on June 6, 2014 by Martin Holladay, GBA Advisor

When my friend Laura Murphy mentioned that her neighbors in Ripton, Vermont, Chris and Zoe Pike, stayed warm last winter by burning just half a cord of firewood, I was intrigued. So I tracked down the Pikes to learn a few more details about their house.

New Green Building Products — May 2014

Posted on May 30, 2014 by Martin Holladay, GBA Advisor

It’s time once again to take a look at a few interesting new building products. I recently spotted two potentially useful ventilation products — a new type of ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV. and a fan for ventilating small rooms — and two products that are destined for attics — an insulating “hat” for recessed cans and a ventilation baffle that can be installed between rafters. I will also report on JointSealR, a tape distributed by Owens Corning for taping XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation. seams.

Earthship Hype and Earthship Reality

Posted on May 23, 2014 by Martin Holladay, GBA Advisor

If you are a hippie from Taos, New Mexico, you know what an earthship is. It’s an off-grid earth-bermed passive solar home with exterior walls made of old tires packed with dirt.

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