Energy Efficient Attic Space Design

How does one design the best possible energy efficient attic system?

First let me draw your attention to human behavior. What does the design of attic spaces have to with behavior? It seems that an innate basic human behavior is the ‘fear of being wrong’. Another innate behavior is ‘fear of change’. Human sometimes would rather continue to make the same mistakes over and over rather than admit being wrong and/or be willing to change.

I’d like to use ‘Indians’, as in Native Americas as a quintessential example of how human beings feel about being wrong and about change. When Columbus set sail from Spain on his first voyage in 1492 he was searching for a direct water route to Asia. Columbus could never admit that he had reached a continent previously unknown to Europeans, instead of the East Indies he had set out for, Columbus called the inhabitants of the lands he visited indios (Spanish for “Indians”). So for the past 523 years we (most of us) still erroneously refer to Native American peoples as Indians, because we, for the most part, are ‘used to’ the term. When I was working in Oklahoma City I was exposed to a phrase that helped identify Indians from India versus Native Americans, which I found kind of funny. “Feather not dot.”

The same can be said for how we design attic spaces. Prior to mass production of central air conditioning the best way to assist in cooling buildings was venting attic spaces. Vented attics were part of a passive ventilation process to create a flow of air.

Enter central air conditioning (and room) for the masses, roughly in the early 1950’s. Building designers elected to place main duct systems in the attic space, put insulation (much later) on top of the ceiling, the compressing unit outside and air handler inside. (Generally) They elected to continue venting attics with the thought it would keep attic spaces cooler, which was true, if you consider 120-160 °F cooler. They simply were and still are fearful of change and now nearly 70 years later are fearful of being wrong. If you live or work in a building that is anything but a passively ventilated, the building’s attic spaces design is very wrong on 4 levels, not just the most egregious one of being grossly energy inefficient. A vented attic space is:

  1. Energy inefficient
  2. Open to humidity, wind driven rain that allows for mold growth.
  3. Open to flying insects, namely termites.
  4. Susceptible to windstorm damage through uplift

How do we create a new or existing efficient attic system? Firstly, big surprise, do not vent the attic. Secondly, insulate the attic on the underside of the roof deck, not on top of the ceiling. Thirdly, with recommendation from a mechanical engineer, bring conditioned air into the space with a supply and return duct. Not to cool the spaces, but simply to move the air through it.

There are many architects and engineers who understand these design parameters. Maybe you’re one of them?

By renovating existing attics or building new ones using spray foam on the underside of the roof deck and recirculating air via an air handler can improve energy efficiency to upwards of 60% versus creating the antiquated, poorly design, status quo vented spaces. As I mention above, the benefits are 4 fold with increased disaster preparedness and improved indoor air quality while decreasing susceptibility to termite infestation.

If you’re a building owner, building manager or homeowner I urge you to consult with an architect and/or mechanical engineer to discuss and implement the correct design for attic spaces.

Gary Shlifer LEED AP BD+C, O+M, Homes - Performance Green Building Consultant

Performance Attic System Design

Please feel free to contact me anytime to discuss this and other topics related to LEED Certification, and Sustainable Performance Green Buildings.