Philadelphia Weekly

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3 ingredients for comfortable indoor temps

Bill and Kevin Burnett
Inman News™

Q: Could you help me decide how to relieve oppressive heat in my rental house, a 1912 Southern California bungalow? In July, August and September, the second-floor bedrooms are uninhabitable until long after sundown.

The house was apparently built with no air vents into or out of the attic adjoining those rooms. The following suggestions have been made:

• Install a wind- and heat-driven turbine on the roof;
• Install an electric exhaust fan;
• Build vents into the roof near the ridge, and drill holes for incoming air into the boards between the rafters at the front of the house under the eaves.

I want to provide some relief for my tenants without huge expense.

A: Both of us having been landlords, we applaud your desire to provide a comfortable living space for your tenants, and we have several suggestions to reduce the second-floor oven temperature. Here are the improvements we would make, in the order in which we would make them:

Insulate the attic: This is the first line of defense. Indoor temperatures seek the temperature outside. In winter, warm house air migrates outside. In summer the opposite happens. Insulation retards this migration.

Insulation is usually figured in R-value, a measurement of the resistance to heat flow. The greater the R-value, the greater the heat resistance. Heat from the roof radiates into the attic space and in turn radiates through your ceilings into the living space.

If the attic isn't insulated, do it. If it is insulated, and the insulation is less than 12 inches thick, beef it up. Twelve inches of batt or loose insulation provides a resistance factor of R-38. This is probably more than your building code requires, but in this case more is better. The material is inexpensive, and if you do the labor yourself, you'll get a huge return on your investment.

Provide adequate attic ventilation: Hot air rises. The trick is to move the air up from the eaves to the ridge vents and out of the attic.

Holes in the lower portion of the roof, called soffit vents, allow the relatively cooler outside air to enter the attic and force the warmer attic air out of the top, or ridge. When you insulate, make sure you do not block the soffit vents. Nail pieces of plywood across the rafters to make an air channel from the soffit vent into the attic.

Ridge vents are an integral part of this system. But rather than go with common "eyebrow" vents, have the roofer install a ridge vent along the entire length of the ridgeline.

Ridge vents are installed by cutting the roof sheeting back a few inches on each side, nailing a long plastic vent over the opening and covering the vent with composition roofing material. One architect told us he prefers instead to drill multiple holes in the sheeting to maintain structural integrity.

Either way the result is a watertight continuous vent system that exhausts hot attic air that is replaced with cooler outside air drawn in through the soffit vents.

Install a fan: There are three choices: a passive fan, a temperature-controlled fan and an electric whole-house fan. All work in concert with insulation and ventilation.

The passive fan is the turbine. It depends solely on convection. We don't like it. Frankly, with insulation and adequate ventilation, the turbine won't bring much to the party.

Temperature-controlled fans are electrically powered or solar-powered. We prefer the electric version.

Solar-powered attic fans rely on a small solar panel (typically 10- or 20-watt) to power a DC motor. Intake vents provide high-capacity powered ventilation without electricity operating costs. Most vents are mounted high on the roof near the ridge and are combined with soffit vents at the roof overhang or gable vents located on the building walls near the roof peak for balanced intake and exhaust airstreams.