ROOF VENTILATION

3 Green Steps = A Cooler, Durable, Earth-friendly Home

Want your roof to last, be comfortable, save you money, and help the environment? Whether you are installing a new roof or retrofitting your existing roof, one of the most important things you can do to make sure your home is comfortable, energy efficient, and environmentally-friendly is to have a proper transfer of heat away from the inside of your home. The 3 Green Steps will help achieve these benefits, along with ensuring your home roofing system meets the standards for manufacturer’s warranty.ventilation-1

The 3 Green Steps

  • Ventilation

  • Insulation

  • Radiant Barrier

Ventilation

It is estimated that nine out of 10 homes in North America do not have proper attic ventilation. Why? Because most people are unaware that attic ventilation can impact the longevity of their entire home.

Proper attic ventilation systems allow a continuous flow of outside air through the attic (see illustration at right), protecting the efficiency of the insulation and helping to lower temperatures in your home living areas. The ventilating flow exists when there is a balance between air intake (at your eaves or underneath the roof overhang) and air exhaust (at or near the top of your roof).

Shingle manufacturers require proper ventilation or they will not warranty their shingles or will greatly reduce the warranty because they know the shingles can superheat from below and will not last their intended lifespan. In the summer, an improperly ventilated attic can cause heat to build in excess of 160 degrees. This superheated air eventually penetrates the ceiling insulation into the living area below.

Damage that can result includes:ventilation-2

  • Cracked or curling shingles
  • Wood framing warping, cracking or breaking down
  • Mold and mildew
  • Damage to siding, exterior or to exterior siding, interior paint, and wallpaper
  • Damage to insulation
  • Higher energy costs to heat and cool the home
  • Wood rot
  • Deteriorated air quality
  • A shorter lifespan for your roof
Wood rot due to improper attic ventilation,
case study, Stanford Park Hotel

A properly ventilated attic can help reduce the load on your air conditioner by moving superheated air out of your attic before it builds up and enters your living area.

In the winter, various household appliances, bathtubs, showers, and cooking vapors can contribute to excess moisture build-up called vapor drive. Improperly ventilation-3ventilated attics will allow this moisture to collect and cling to the underside of the roof deck. There, it will condense and fall, soaking the attic insulation, causing it to compress and clog, reducing its efficiency.

Retrofitting ventilation on existing home

Your attic is an oven – literally! Trapped heat will bake your roof, regardless of which type, causing premature damage. Now is the time to correct the problem with proper ventilation. Let your attic breathe to cool your roof down and soon you will feel the temperature in your home go down as well, which saves you money on air conditioning while making the whole family more comfortable.

It is estimated 9 out of 10 homes have improper ventilation caused by an inadequate, outdated design which doesn’t create enough circulation to create proper airflow required to meet the roofing manufacturer’s specifications for warranty.  Yes, the building code and manufacturer’s requirements do change. Eastman Roofing and Waterproofing is adept at fixing this problem. We examine the unique configuration of your home to find the best combination of location and type of vents to take the burden of trapped hot air away from your attic space to keep your roof and the inside of your home cool.

When retrofitting attic ventilation the same basic principles apply as to when applying a new roof. The best solution for you should include:

  • Area (in square feet) of the attic space to be vented
  • Calculations to determine the net ‘free air’ in inches needed to achieve one sq. ft. of ventilation per 150 sq. ft. of attic space (Note: The vent manufacturer publishes what the net free air of each vent produces and this information will be given to you)
  • The location of the vents should be balanced
  • Half of the ventilation needed should be intake and the other half should be exhaust
  • Calculations to show the accurate number of vents needed
  • A diagram showing the type and where the vents are to be located

See our case studies for examples of retrofitting ventilation on existing homes in Los Gatos and Burlingame.

How much ventilation do you need?

The current code requires a minimum of at least one square foot of attic ventilation (both intake and exhaust) for every 150 square feet of attic space. For example, if your attic is 900 square feet, you need a total of 6 square feet of ventilation. This amount is generally divided equally between intake and exhaust ventilation (i.e. 3 feet of each), to insure proper airflow through the attic.

 

Insulation

Properly installed insulation not only helps protect your living spaces from heat build-up in your ventilation-4attic, it also helps prevent energy leakage from the top-floor ceiling. Insulation should not block attic ventilation. There are different types of insulation for different applications. How much attic insulation do you need? For example in our area, about 7 ½ inches of blown in insulation will give you R-30.

 

Radiant Barrier

A properly installed radiant barrier can be an important part of reflecting external radiant heat from the sun away from your attic. In fact, a good radiant barrier product such as the LP® TechShield® Radiant Barrier offered by Eastman Roofing & Waterproofing, could lower your attic temperature by as much as 30 degrees! Think of how that can impact the comfort of your home, let alone how much less (up to 17 percent) your air conditioner will have to work to keep your home cool.

If you want to choose the 3 Green Steps for your home give Eastman Roofing a call at 1-800 287-2006 and we’ll send our expert inspectors to examine your roofing system and provide a tailored report.