Solar Roof Fans 101
You've got questions, we've got your answers! Everything you have every wanted to know about solar roof ventilation systems courtesy of consumer inquiries. If you don't see your question below, feel free to Contact Us and we will add your inquiry to the list!
Q. We get a lot of sun and our home gets extremely hot during the summer. It seems like our air conditioner runs constantly and sometimes cannot keep up. Will your SolarVent roof ventilation fans help?
A.During the summer, roof cavity temperatures can soar to over 65 degrees Celcius, keeping your roof cavity hot throughout the day and well into the night. The higher the temperature of your roof cavity, the less effective roof insulation will be at stopping heat from entering your home. While roof insulation slows this process, it does not eliminate the heat transfer process entirely. Furthermore if the insulation is old or the roof is not very well insulated, it will do very little to stop heat from entering your home.
Installation of an Attic Breeze solar attic fan helps to minimize the amount of heat entering through the attic by reducing your attic temperature. By minimizing the amount heat entering your home, your air conditioner will run less and your home will feel more comfortable.
Q.We receive a lot of hail storms in the area. How well do the solar panels on SolarVent solar roof fans hold up to hail?
A.SolarVent uses commercial grade solar panels with high-strength tempered glass on all of our products. These solar panels feature an anodized aluminum frame for added strength and protection, similar to the solar panels that are used by your local state highway department. Our solar panels are designed to withstand mild to moderate hailstorm conditions and are factory tested to comply with impact resistance industry standards.
Q. We purchased a SolarVent solar roof fan (SVA25B) for our home last year and absolutely love your product! I could not believe how much cooler our house felt. My husband would like to install one of your solar roof fans on his workshop to help keep it cool during the summer, but the workshop doesn't have a roof cavity. Do you have any type of product for this application?
A. The application you are describing is know as "whole house or workspace" ventilation and we can absolutely help. In this application, air is moved through the entire house, workshop, or warehouse space to generate a continuous breeze. Fresh air is brought in through open windows, doors, or intake vents and exhausted through the solar powered fan. SolarVent has both wall mounted and roof mounted solar fans available for this type of application. Please note that sizing of the fan(s) for the application will depend on how the workspace is being used (amount of ventilation needed) and on the actual dimensions of the workshop.
Q.How quiet are your fans?
A.SolarVent solar roof fans are designed for whisper quiet operation. Using a proprietary five wing aluminum fan blade adjusted to optimum pitch performance, our solar roof fans will produce <1 sonne (<30 decibels) of noise during operation. In real world terms, this is less noise than a quite library.
Q. I have heard good things about SolarVent from one of my neighbors that has installed your solar ventilation fans. I would like to install a solar ventilation fan on my home as well, but my roof has ridge vents and I am concerned that these may not work well with the fan. Can your solar ventilation fans be installed on a home that has ridge vents?
A. Yes, you may install our products with an existing ridge vent. However please note that while the solar roof fan is operating, the ridge vent will work in reverse acting as air intake vent. In fact, every passive vent on your roof will act as an air intake vent while the fan is operating. This is not a problem, it is simply a different method of operation for your roof's ventilation system.
Ridge vents operate on the principle of natural draft air convection. This means that as the roof cavity heats up, hot air will rise to the roof ridge and naturally flow out from the ridge vent. For ridge vents to work properly, the roof cavity temperature must be in the range of 55-60°C. During normal operation, ridge vents typically produce 3-4 roof air exchanges per hour, not enough to adequately cool the roof and minimize heat transfer into your home.
SolarVent solar roof fans operate on the principle of forced draft air convection. Our fans create an air draft through the attic many times more powerful than that of natural draft air convection or wind powered turbine vents. SolarVent solar roof fans work the hardest when you need them the most creating a self-regulating ventilation system; the more solar radiation (sunlight) your roof receives, the faster our solar roof fans operate to remove heat. During normal operation, SolarVent solar roof fans have the capability of exchanging hot roof cavity air 10-20 times per hour, typically keeping your roof cavity temperature between 5-15°F of ambient outside temperature.
When installing our products in conjunction with ridge vents, the solar roof fan unit should be installed a minimum of 5-6 feet away from the ridge vent to allow for balanced air flow through the attic. Experience shows that this distance will typically allow enough space for proper balancing of air intake ventilation from both the ridge vent and other roof vents. When the solar roof fan is not operational, the ridge vent will function as normal.
Q. I had two SolarVent solar powered gable fans installed last summer by your dealer. I was very impressed with the reduction in my electricity bills! However, I am concerned that the fans appear to still be running even though it is 18°C outside. The gable fans were ordered with thermal switches included, so I'm wondering if they are operating properly?
A. Yes, your solar gable fans are operating within normal parameters. The thermal switches included with all SolarVent solar powered ventilation products function within a nominal range of 18-24°C. Please note that these mechanical thermal switches are not "thermostats" and have a much more course range of operation, which is appropriate for this type of application.
In general, given a home with typical roof insulation, heat transfer into or out of the home will only begin to occur when the temperature difference between the roof and inside of your home is greater than about 15-20°F. For example, assuming the inside temperature of your home is roughly 24°C, you will find that heat loss is negligible when your roof temperature is as low as about 12-15°C. Likewise, any heat gain into your home will be negligible when the roof temperature is as high as about 32-35°C. Please note that your roof temperature will always be higher than that of the ambient outside temperature. So no worries, your fans are working properly.
Q. I have researched solar ventilation fans on the internet and in my opinion it appears that SolarVent is the best. You guys don't use plastic parts, the product is made here in the USA, and you have a lifetime warranty. However, I noticed that SolarVent doesn't make the same 30-40% savings claims that I saw on other manufacturer's websites. What kind of savings can I expect if I were to purchase your product?"
A. SolarVent strongly believes in the concept of "truth in advertising" and in doing so will not publish any claims that cannot be substantiated. No solar roof fan manufacturer can actually guarantee how much a customer will save by installing a solar roof fan. In general terms, the more air a solar roof fan moves, the closer the roof temperature will approach that of the outside ambient temperature. Reducing the roof temperature helps to minimize the amount of heat transferred into your home. Actual savings from installing a solar roof fan are realized by reducing the amount of heat your air conditioner must remove.
As you can imagine, older homes with poor or degraded insulation may benefit more than newer homes. Likewise, homes with poorer quality air conditioning systems will benefit more than homes with high efficiency heat pumps. Factors such as electricity cost, total roof cavity area, roof slope, roof color, age/efficiency of roof insulation, and the age/efficiency of your air conditioning equipment all play a role in determining your overall savings. Annual savings can range from as low as 5% to as high as 40%; everyone will see some benefit by installing a solar roof fan, but everyone’s situation is different.
We can say that if properly sized for your application, installation of our products will typically reduce roof air temperatures to within -9--15°C of the outside ambient temperature. Experience shows that installations on older homes typically have a pay back of 1-2 years. Newer homes will have a slightly longer pay back period based on their designed energy efficiency.
Q. Is there any electrical wiring required to install your solar ventilation fans?
A. No, SolarVent solar ventilation fans ship assembled and ready for use. Our solar ventilation fans are stand alone solar powered units and are not tied to your home's electrical grid.
Q. I have two whirlybird vents on my roof, but we are re-shingling next week and I'm considering replacing these with your products. Are your solar ventilation fans more effective at cooling the roof cavity than the vents I currently have? Would I have to replace the whirlybirds or can I keep them and install your products as well?"
The effectiveness of any ventilation product is based on the physics of thermodynamic heat transfer. As this applies to cooling a roof cavity, the more roof air exchanges you can achieve in a given amount of time, the closer the roof temperature will approach that of the outside ambient temperature. Therefore, cooling effectiveness really comes down to how much CFM the ventilation product can create.
A typical "whirlybird" turbine vent generally produces about 500-800 CFM of air movement when the wind is blowing good. The actual CFM generated by your turbine vents can most likely be found on the manufacturer's website. While this amount of air movement is respectable, the technology is limited in the fact that it only works when the wind blows, not necessarily when the sun is beating down on your roof.
SolarVent residential model solar roof fans can move up to 1550 CFM of hot roof air. The real advantage of using our solar roof fans is that they operate faster as your roof receives more direct UV radiation. In this respect, the technology is "self-regulating" in terms of cooling efficiency; our solar attic fans work the hardest when you need them the most.
You can leave your whirlybird vents in place and simply add our solar roof fans. The only requirements are that the solar roof fans must be installed at least 10 feet away from the whirlybird vents and you must provide enough roof cavity intake ventilation to support both the solar roof fans and the existing whirlybird vents. If aesthetics or intake ventilation requirements are a concern, you may easily replace the whirlybirds with our solar roof fans.
Q. I am interested in solar roof vents, but have some concerns over roof cavity depressurization. I recently read an article that suggested roof ventilation fans have the potential to pull air from inside the home and into the roof. Is this a possibility with the SolarVent fans as well?"
Roof cavity depressurization occurs when there is not enough roof cavity air intake ventilation to support the volume of roof air being removed. While depressurization can occur naturally (i.e. the sudden cooling of your roof during a rainstorm), it may also occur when using powered ventilation. Since airflow follows the path of least resistance, for any powered ventilation system to create depressurization and pull conditioned air into the roof, it must have enough power to overcome both any roof intake ventilation present, as well as that of frictional effects created from pulling air through the small cracks and opens between the roof cavity and living space of your home.
Although by appearance they may seem the same, AC powered attic fans and SolarVent solar powered roof fans are distinctly different. AC powered roof fans have a very large source of grid power from which to use, as well as a constant speed AC motor. When an AC powered fan does not have enough "free" air intake to support the motor's operating speed, the fan simply uses more power in order to maintain motor speed, thus pulling more air from any air intake source available. If the AC powered fan is not installed with enough roof cavity air intake ventilation, roof depressurization may occur.
By contrast, SolarVent solar roof fans have both a limited source of solar power and use a variable speed DC motor. Given the same situation, our solar roof fans will simply reduce in speed rather than pull more air because additional power is not available. Additionally, our proprietary UltraFlō™ technology also helps minimize any chance of depressurization by virtue of our unique airflow dynamics. If installed properly with the recommend amount of intake ventilation, roof cavity depressurization will not be a problem with SolarVent solar powered ventilation products.
Q. My sister bought a SolarVent solar roof fan last summer. She is very happy with her fan and has convinced me to buy one as well. I see from your website that I can either have the solar roof fan with or without a thermal switch. Why would I not want the thermal switch?
A.SolarVent SV25 series residential model solar roof fans include a thermal switch as part of our standard package. This mechanical thermal switch is factory preset to operate within a nominal range of 18-24°C. The thermal switch allows the solar roof fan to automatically shut down when roof temperatures fall below the preset range. This reduces winter heating bills and extends the life of the motor.
You may consider removing the thermal switch if you will be using our products to ventilate a warehouse, workshop, or garage where you would want the solar fan operate continuously, regardless of temperature. Additionally, in tropical climates you may also choose to have the fan operate continuously if used as a whole-house fan.
Solar roof fans are also used in northern climates to control roof moisture and humidity problems which occur during the winter. If your home experiences ice damming, then operating a solar roof fan through the winter may be a good option. For any of these applications, it would be appropriate to operate the solar roof fan without a thermal switch.
Q. Will SolarVent solar roof fans operate on cloudy days? Do the solar panels store energy so that they can operate when the sun goes down?"
A.The high efficiency monocrystalline solar panels used on all SolarVent products allows our fans to even operate on cloudy days. Our solar roof fans work the hardest when you need them the most; the more direct sunlight the fan receives, the faster the fan moves. On cloudy days the fan will move more slowly, on rainy days the fan will not move at all... which is exactly the operation that you want with regard to your roof ventilation.
No, the solar panel transfers all power to the fan and there is no battery back up included with our products. However, if sized appropriately for your application, running the solar roof fan at night should not be necessary. The majority of all heat gain to your roof occurs between the hours of 11AM to 3PM, so the real key to proper roof ventilation is removing the heat from the attic as it is received. If sized and installed properly,SolarVent solar roof fans will keep your roof cool throughout the day and eliminate the need for additional night time cooling.
Q. I am a contractor and have installed 10 watt solar roof fans for about a year now. I can see there is a clear need for something more powerful, so I found SolarVent on the internet. I am impressed by the various options SolarVent offers as this is not the case with the roof cavity fans I currently use. Since the 10 watt fans I use now are plastic, I do have a question about the corrosion resistance of the natural zincalume finish. Does the zincalume finish need to be painted to avoid rusting?
A. For most applications painting or powder coating is not necessary to prevent rusting. All SolarVent ventilation products are manufactured from corrosion resistant zincalume alloy (45% zinc; 55% aluminum). Zincalume has all the corrosion resistant properties of aluminum, but is much stronger and of course will not crack or degrade over time like plastic.
In the case of salt air environments, it is recommended to choose an SolarVent product featuring a powder coated finish (roof mounted products only). Our powder coating process meets ASTM standards for marine environments and adds an extra degree of protection against salt air corrosion. Powder coated models are available in your choice of black, brown and terracotta.
Q. Which direction does a solar roof fan need to face? Our home faces west and I want to make sure I buy the correct SolarVent model. Can you help please?
For optimum performance in locations throughout Australia, the solar panel on your SolarVent solar ventilation fan should always be installed facing toward the north. This will give the solar panel the best average sun exposure throughout the day (see below).
Determining the optimum angle of inclination will depend on your specific location and time of year. As a general rule, the solar panel should be inclined to the same angle in degrees as your latitude coordinates. For most locations in Australia, this angle will be between 35-45 degrees from horizontal for obtaining the best average performance throughout the year. If the solar attic fan will be operated mainly during the summer months, you may subtract roughly 10-15 degrees from this angle to obtain maximum seasonal performance.
Since your home faces west, you will most likely want to install the solar roof fan on the rear exposure of your home (west side). In order to get the proper northern orientation, there are two SolarVent model options to consider: models featuring an attached solar panel with the optional pivot bracket or models featuring a remote mounted solar panel with optional universal bracket. While either option will work, we do recommend the universal bracket for areas prone to high winds.
Q. Can SolarVent solar roof fans be installed on a flat roof?
A. Yes, we offer models featuring curb mounted flashing designed to work with flat roofing designs. Curb mounted models are available in 25 watts for either residential or commercial flat roof applications.
Q. I came across SolarVent while looking for a way to lower my electric bills. Your solar roof fans seem like a great way to do this. If I need more than one solar roof fan for my home, how should they be spaced on my roof?"
When installing multiple solar roof fans, the units should be located on the roof to maximize cross-flow ventilation through the roof cavity and balance airflow from all air intake sources. Spacing between solar roof fan units should be at least 10 feet apart for optimum performance.
Q. I have a very low pitched roof with only 3-4 feet of cavity space and blown insulation. My roof gets very hot during the summer and I need a solution. Will the SolarVent solar roof fan work with blown roof insulation? Will I have to crawl through the roof to install the fan?"
As long as the blown insulation is at least two feet under the solar roof fan, there should be no issues. SolarVent SVA25 series roof mounted solar roof fans may be installed from the top of your roof, so no need to crawl through your roof cavity.
Q. Does your solar roof fan require any annual maintenance?
A. SolarVent solar roof fans are virtually maintenance free. The solar panels are typically self-cleaning, but may require an occasional wash if you live in a dusty area or only get small amounts of annual rainfall.
Q. Some manufactures claim that their gray colored solar roof fans perform better than black colored competitive fans. Do you find that the lighter colored SolarVent solar attic fans perform better than the dark colored fans?
A. While it is a fact darker colors do absorb more heat than lighter colors, this will not affect the performance of our ventilation products. SolarVent solar roof fans are designed to be self-cooling, so all of our products perform equally well, regardless of color.
SolarVent solar roof fans featuring a unit mounted solar panel are designed with an air gap between the solar panel and fan unit. This air gap functions to keep our solar panels well ventilated, allowing the panel to operate at peak efficiency and provide more of its rated power over a larger ambient temperature range. Other manufacturer's solar roof fan products without this feature (flush mounted solar panels) may lose rated power as the panel temperature increases, resulting in less air flow from the fan than claimed.
Q. I have a small warehouse I wish to ventilate, with many trees surrounding the building. Will shade from trees prevent your solar roof fans from working?
A. Shade trees and shadows in general have a very negative effect on the operation of solar panels. While our high efficiency solar panels do work given cloud cover, they will not work in the shade. When choosing a location to install your solar roof fan, make sure to consider the sun exposure profile your roof receives throughout the day.
For optimum performance, you may consider an SolarVent model fan which features a remotely mounted solar panel. These models come standard 15 feet UV/weather resistant cable. If more cable is needed to achieve maximum daily sun exposure, SolarVent also offers an extended 40 foot cable option.