Do It Yourself Energy Efficiency Projects: Your Home’s Thermal Envelope (Part 11): Your Roof: Heat Shield to Maximum!

By Vernon Trollinger, February 19, 2010, Energy Efficiency, Home Improvement

There are a few things you can do around your home to save money during the winter months and the hot summer. Basically, you need to air seal your home's "thermal envelope"; the sum total of the home's insulation systems including walls, ceilings, foundation, floors, windows, and doors. These work more effectively with good, tight fits that seal-out the weather, moisture, and air. 

By having a tight seal, the less energy you waste or lose by exchanging it too often with the air outside. Your roof doesn't just keep out the rain. It helps cool and ventilate your home and in a few years, Dow's Solar Shingle might even generate some of your home's electricity.

You might believe that work I describe below is beyond your ability. Never fear, these are easy tasks for any average person. Make sure you have a good set of tools. Plus, you might want to look at the Federal Energy Efficiency Tax Credit and save on your taxes, too.

By the way, there's no way around this: you will get dirty.

Your Roof: Heat Shield to Maximum!

Your roof is a heat shield for your house. But in order for it to work at peak efficiency, it needs to be adequately ventilated. The National Roofing Contractors Association recommends 1 square foot of ventilation opening should be provided for every 150 square feet of ceiling area.  

If you've ever ventured into an attic on a sunny summer day, you know how hot it can be. Temperatures can easily reach 150 degrees F. Trapped heat increases your air conditioner's heat load. This raises your energy costs. Trapped heat also can damage the plywood sheathing, under-layment, shingles and personal items located inside the attic. 

If you are considering re-shingling your home, take a serious look at choosing a light-colored shingle.  A white colored shingle can reflect 30% of the heat it absorbs from sunshine.  Metal roofing systems also come with finishes that reflect heat as well.

Roof ventilation works with two kinds of vents, an exhaust and an intake. Heated attic air flows out through a vent in the upper part of the roof. This pulls in cooler air to enter through intake vents located down in the soffiting or fascia board. As this air absorbs heat, it leaves through the upper vent and the cycle is repeated. Most houses built in the 1960s onwards use a combination of soffit vents and either gable vents, roof vents, or ridge venting to allow air to flow through the attic. By allowing the attic to breathe and circulate heated air out, the house can let go of the heat it absorbs during the day. 

Retrofitting roof vents is not as hard or expensive as it sounds. Nevertheless, it can be daunting to climb onto your roof and cut holes into it. I have found the easiest to install is the ridgevent system. Ridgevents come in plastic or metal vent kits ranging from $1.50 to $4.00 per linear foot. Ridgevents are hollow inside and have either vents along their sides or under a flange. By straddling a slot cut though the sheathing at the roof's ridge or peak, heated attic air can leave without letting rain inside. 

The actual installation technique varies slightly depending on the kit you use.  But basically, you remove the top cap of shingles on the roof, and use a circular saw to cut out two 1-inch wide slots through the roof sheathing from both side of the roof's ridge. If you're installing full length venting, you'll be cutting slots the entire length of your roof. Afterwards, attach the ridge vent (carefully follow the manufacturer's instructions) and caulk over nail heads and all seams. 

Remember, use a new, sharp saw blade and take your time.  Using a dull blade while way-up-high just begs for saw kick-back and a tearful ending.

Seal the Envelope

Now that you've seen what to look for in your home thermal envelope, you can start planning where to begin; walls, ceilings, foundation, floors, windows, doors, or the roof. And while it's import to consider how your home works as a whole, approach improving it one step at a time. Remember that all these jobs don't need to be done all together all at once.  Dividing the project of sealing your home into smaller, manageable jobs around the house makes it easier to tackle. Tackle ridgevents one weekend, insulation another, or a new thermostat some weeknight after dinner. You should notice more energy efficiency — however slight — after each improvement. They will add up: you will save money and your home will feel more comfortable. But be sure to take your time preparing and researching: read the instructions, and use good, sharp tools. 

Above all, be careful when considering projects that seem beyond your skill level. If in doubt, hire a professional. After all, sometimes doing-it-yourself can really do-it-to-you.

Visit the Bounce Energy Education Center for more tips on saving energy everyday.
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Comments (1)


  1. Ender Berett says:

    One of the most important parts of heating and cooling your home is your roof. That’s why I want to get a roofing contractor so bad. It seems like energy bills take up most of my payments, and I would love to prevent that.