“Hot spots and moisture pockets. Hot spots and moisture pockets.”
No, I’m not writing a song or inventing a children’s playground chant. I’m talking about two of the flaws in conventional solar roof ventilation ideology. The idea of solar attic ventilation is fairly new and it is a great idea! Why not use the power of the sun to remove hot air in the summer and moist air in the winter? Many ventilation manufacturers immediately seized on this idea and have brought many products to the market as a result. As manufacturers raced for the lead and products began competing, many variations sprang up, most trying to squeeze the highest horse power out a solar panel to power the largest fan possible.
When I’m telling others about Solar Blaster’s ventilation solutions, many times the first question they ask is, “What’s the cfm of your fan?” If they are competitors, after I tell them the answer, they begin bragging about their fan’s higher cfm.
Laughing aside all the “bigger is better” analogies, I proceed to explain to them why my way of solar venting a roof is not only the best and correct way to ventilate an attic space, but also why it is the future of solar-powered roof ventilation.
Large solar fans do not take into consideration roof design. Roofs are designed to passively pull air in from the intakes vents located at the eaves and exhaust the air uniformly from the highest possible point on the roof either by using multiple can-type roof vents or ridge venting. The keywords here are “uniform” and “multiple.”
Placing a large solar fan high on the roof in many cases defeats the purpose of the designed passive ventilation system. Large, high-cfm solar fans have to get their air from somewhere, and due to their power, will often rob air from the nearby ridge vent or can-type vents. They defeat the uniform air movement concept by leaving hot spots in many areas of the roof during the summer because they are no longer drawing air in from the eaves. During the winter, when hot air from your living space hits the cold roof decking in your attic, it condensates just like a can of pop. Without uniform air movement in winter to get rid of that moisture, your attic can often end up with mold which causes serious health problems. Many of the winter problems I see on a regular basis involve attic moisture problems caused by lack of uniform venting.
The only proper way to work within the confines of the existing design system of your roof is to remove and move air in a uniform manner. So how do we do that?
The future of solar-powered attic ventilation will include the use of multiple, smaller fans to uniformly remove hot air and moisture from your entire attic. In this respect, several smaller solar-powered fans do a much better job than one large solar-powered fan.
High cfm solar fans give the wrong impression to homeowners. Even if the mathematics say you only need one of these super-duper high cfm solar fans to recycle your attic air so many times an hour, what happens when the sun isn’t shining? Your roof must have a passive vent system that works when the solar fans can’t.
So there has got to be a better solution that enhances one’s passive ventilation.
A small fan is not powerful enough to rob from the surrounding vents while strong enough to solar activate the passive vents to exhaust the air already searching for a high point. Multiple, small fans work in concert to move air uniformly across your entire attic length. Once air has begun to move in your attic through solar activation it tends to stay in motion. A solar-powered attic breeze reduces energy costs. Summer attic heat tends to transfer into living space because homes and insulation store loaded heat. Unloading this heat through uniform attic air movement increases your comfort and reduces cooling costs. Moisture in your structure and especially in your insulation reduces its effective R-value, thereby increasing your heating costs.
The invention of the first true solar-powered ridge vent, the Solar RIDGEblaster, has revolutionized the way people ventilate because it uses the very highest point on your home to exhaust air. It uses a 10-watt panel to power three small 2.7 watt fans. As soon as the panel captures enough energy, it will power the first fan even on most cloudy days. On full sunny days, all three fans kick in to really move that attic air and boost the effectiveness of your passive vents.
Can you tell me your large solar attic fan works on cloudy days? I didn’t think so.
Solar activating your existing can vent system means that your passive can vents work as they are supposed to according to the design of your roof even under thick cloud conditions. But when the sun comes out. Whammy! Air begins to move more quickly through your existing design system by the power of the sun. Utilizing the existing passive ventilation system protects the aesthetic aspect of your home by not adding unsightly large solar-powered fans. It also works in conjunction with what your roofing contractor is already installing on your home — conforming to local and national building codes.
There are also tax credit advantages available on a federal level which includes both material and installation labor.
The use of multiple, smaller solar-powered fans is the only correct way to properly power assist venting of your attic space and is the future of roof ventilation.
About the Author
Dan Rheaume is the owner of Raynproof Roofing, a residential roofing company in Seattle, Washington since 1986. In 2009, he started the Solar Blaster Corporation and is the nation’s leading expert in the use of multiple, small, solar-powered fans that will revolutionize the way homeowners ventilate their roofs.