The Attic Effect
How Home Comfort and Energy Efficiency are Affected
What is the attic effect?
The attic effect is the impact the attic space has on your home’s overall comfort and energy efficiency. Three factors are at play.
- Warm air rises and cold air sinks. That’s basic gravity.
- Temperature naturally wants to balance between two spaces so there is an exchange of hot and cold air. That’s a heat transfer thing. And…
- Air movement caused by pressure differences naturally wants to balance itself. High pressure moves to low pressure.
And that, my friends, is the physics of building science.
In the summer, the attic’s midday temperature produces the most extreme temperature difference in your home. This is because your attic’s temperature can climb to 140 or 150 to 170 degrees. Your attic acts like an “oven” that radiates heat, fighting your air conditioners. The hot attic wins most of the day.
In the winter, it’s the opposite. Heat from the home moves into the attic space. This causes comfort issues in the home, forcing you furnace to work harder. This causes higher heating bills.
Besides the lack of energy efficiency, such conditions can also lead to excessive moisture and problems with mold. Roof ice damming can also be a resulting problem.
There are three culprits contributing to these attic issues.
The three issues to identify when determining if the attic space has a positive or negative impact on the home’s comfort and energy efficiency are: 1) Ventilation, 2) Insulation, and 3) the Air Leakage Rate between home and attic space.
Air Leakage and Air Sealing
Ceiling breaches (e.g., for wires, lighting and bath fans) and small gaps in construction framing allow air to move freely between attic spaces and living spaces. In the winter, warm air escapes, creating a vacuum effect at the base level of the home. In the summer, hot air from the attic infiltrates the home through the same gaps, cracks, leaks and penetrations.
A proper thermal barrier, in the form of insulation, slows radiant heat and cold-air conduction transfer in both summer and winter. The insulation’s type, depth and consistency must be calculated to determine the most “effective R-value” of the thermal barrier separating home from attic.
If the attic deck has been well sealed and properly insulated, then the attic space can be considered a “breathable” area. The key is to have the proper amount of ventilation running through the attic. This is calculated based on the square footage of the attic space. Also, the ventilation must be equally balanced between the high roof vents and the low soffit vents.
Solve your home's attic issues.
Take the first step to understand if your attic is costing you money and comfort.
An energy audit evaluates all three attic components. The resulting report identifies the attic’s impact on the home’s comfort, safety and efficiency. The amount and balance of the attic’s ventilation is calculated. The insulation is inspected, and its R-value determined. To calculate the amount and locations of air leakage, a blower door test and infrared scan are performed as part of the home energy audit.
The resulting home energy audit report outlines attic issues and provides recommendations to correct attic problems. Improve your home’s comfort while optimizing energy efficiency.