Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Who has experience with solar powered roof/attic vent fans? What can you tell me about them? Which one(s) should I select or NOT select?
Any problems with rain blowing in? Noise problems?
Since they are solar powered, I'm curious as to whether they would work on a cloudy day?
On a sunny/warm day, how long do they continue to work after the sun goes down?
Years ago, I had two electric powered roof/attic fans. They worked very well but were noisy. The noise was quite irritating if you were on the second floor of the 2-story house. On a hot summer day, the fans wouldn't quit running until around 11 PM.
Just wanted to get some comments/recommendations from people who have actually used the new solar powered roof/attic fans. Thanks.
I have seen powered roof vents burn up. Solar or not, there is a fire risk involved. A far better solution, when possible, is to upgrade the ceiling insulation. A hot attic isn't a particularly bad thing.
I wouldn't get so overly zealous about "fire"- but it can happen.
As harry mentioned, upgrading the envelope of the house is probably better than trying to decide which, if any*, ventilation means is necessary. And to that point- active ventilation systems can be counterproductive because they may actually be pulling the cool air in the conditioned space into the attic.
Since I have no idea where the house in question is- it's hard to have a starting point, other than the aforementioned "upgrade". But, there are many things that work in zones 1 and 2, but do nothing for zones 4 and 5.
For most H/O's (the typical layperson that has no conception of residential construction, and the systems that make a house a home- and maynot know typical maintenance and/or schedules of such...), *a passive system (properly installed) will always be the best system.
I had such a fire at a business I owned about 30 years ago. No one was in the building when the fire started. Fortunately a passerby saw smoke, called the fire department, and there was minimal damage.
Locally most homes are built with either a ridge vent or the spinning golf ball type vents. His is in south Louisiana. Check with builders in your area. Different climate may have different needs. Allowing the attic some ventilation is healthy for the home and its occupants.
I had a solar attic fan at my 1927 bungalow. I had it installed after the roof was replaced (the first time) and the old turbine fans were removed and a ridge vent was installed. There were never any problems with it in the 12 years it was there until I sold the house, and no rain came inside either. I did have it on the southern end of the hipped roof so it would pick up any sunlight and ran a LOT. It did make a difference in the attic temperature.
I had a solar attic fan at my 1927 bungalow. I had it installed after the roof was replaced (the first time) and the old turbine fans were removed and a ridge vent was installed. There were never any problems with it in the 12 years it was there until I sold the house, and no rain came inside either. I did have it on the southern end of the hipped roof so it would pick up any sunlight and ran a LOT. It did make a difference in the attic temperature.
This is the kinda stuff I see and hear all the time- and it's WRONG!
Why have a ridge vent if you're going to have a power ventilator? It defeats the purpose of the the ridge vent! Air, like water, takes the path of least resistance. So, if the ridge vent is in close proximity to the power ventilator it's just "pulling" air from there instead of the soffit vents. The whole idea of soffit vents and a ridge vent is for "convection". Cooler air is pulled through the soffit vents and rises to the ridge vent and exits- the essence of a "passive" system.
Whenever you introduce an "active" means (mechanical/electrical fan), you are not only defeating the purpose of the ridge vent, but you're probably also creating enough negative pressure that you may also be pulling the conditioned air from the living space (as I previously noted). This would be especially true on just about any home that is 25+yrs old.
This is the kinda stuff I see and hear all the time- and it's WRONG!
Why have a ridge vent if you're going to have a power ventilator? It defeats the purpose of the the ridge vent! Air, like water, takes the path of least resistance. So, if the ridge vent is in close proximity to the power ventilator it's just "pulling" air from there instead of the soffit vents. The whole idea of soffit vents and a ridge vent is for "convection". Cooler air is pulled through the soffit vents and rises to the ridge vent and exits- the essence of a "passive" system.
Whenever you introduce an "active" means (mechanical/electrical fan), you are not only defeating the purpose of the ridge vent, but you're probably also creating enough negative pressure that you may also be pulling the conditioned air from the living space (as I previously noted). This would be especially true on just about any home that is 25+yrs old.
I have read statements online similar to yours on this topic in the past day or two while doing my research, but I'm not sure that I buy that argument. If you're willing to defend it or educate me, I'll tell you why I don't buy it.
These vents (whether passive or active like an exhaust fan) are typically placed high on the roof. Let's assume that the roof also has soffit (entrance) vents under the eaves. Further, let's assume that on a hot summer day, it may be 130 degrees in the attic while the outside air temperature may be in the 90's.
We all know that hot air is lighter than cooler air and therefore will rise to the top of the attic. So, we know that on a hot summer day the air temperature in the attic near the top of the attic is going to be much HOTTER than the outside air temperature.
With the above factual information as a "given", then why would we think that the attic fan is going to pull outside air (about 95*) down from the ridge vents instead of pulling the much hotter and much lighter air from the attic? That doesn't make sense to me that the 95* air from the outside would circulate in the top foot or two of attic space while the hotter (130*) and lighter air stays below near the bottom of the attic space.
If you can explain how and why the cooler and heavier 95* air would circulate in the top foot or two of the attic while the much lighter (130*) air remains below, then I would be interested in hearing it. That's kind of like saying that an inner tube that's filled with air is going to remain on the bottom of the swimming pool because the heavier water above it won't let it rise. Sorry, but I'm just not buying that.
Let me give you one analogy. Suppose that you are using a vacuum cleaner to clean off a desktop that is filled with a variety of objects such as paper, pencils, stapler, books, etc. So you're waving this vacuum cleaner nozzle just a few inches above the desktop, which object are you most likely to suck into the vacuum hose? It won't be the book or the stapler. Nor will it be the pencils. It will be the lightweight pieces of paper that will be sucked up. Seems that the same would apply to the lighter (hotter) air being pulled out of the attic.
I have read statements online similar to yours on this topic in the past day or two while doing my research, but I'm not sure that I buy that argument. If you're willing to defend it or educate me, I'll tell you why I don't buy it.
These vents (whether passive or active like an exhaust fan) are typically placed high on the roof. Let's assume that the roof also has soffit (entrance) vents under the eaves. Further, let's assume that on a hot summer day, it may be 130 degrees in the attic while the outside air temperature may be in the 90's.
We all know that hot air is lighter than cooler air and therefore will rise to the top of the attic. So, we know that on a hot summer day the air temperature in the attic near the top of the attic is going to be much HOTTER than the outside air temperature.
With the above factual information as a "given", then why would we think that the attic fan is going to pull outside air (about 95*) down from the ridge vents instead of pulling the much hotter and much lighter air from the attic? That doesn't make sense to me that the 95* air from the outside would circulate in the top foot or two of attic space while the hotter (130*) and lighter air stays below near the bottom of the attic space.
If you can explain how and why the cooler and heavier 95* air would circulate in the top foot or two of the attic while the much lighter (130*) air remains below, then I would be interested in hearing it. That's kind of like saying that an inner tube that's filled with air is going to remain on the bottom of the swimming pool because the heavier water above it won't let it rise. Sorry, but I'm just not buying that.
Let me give you one analogy. Suppose that you are using a vacuum cleaner to clean off a desktop that is filled with a variety of objects such as paper, pencils, stapler, books, etc. So you're waving this vacuum cleaner nozzle just a few inches above the desktop, which object are you most likely to suck into the vacuum hose? It won't be the book or the stapler. Nor will it be the pencils. It will be the lightweight pieces of paper that will be sucked up. Seems that the same would apply to the lighter (hotter) air being pulled out of the attic.
This is a wonderful questioning, and kudos for going there.
There are reasons, but they might not be obvious.
When a roof gets hot in the sun, the underside of the roof is the hottest part of an attic. There is nothing otherwise that adds heat in such an amount. The ceiling of a 75 degree room? Not even.
The vents at the peak of a roof are part of a laminal flow. coolISH air form the outside comes into the soffit vents. It puddles at first, but when the sun hits the roof there is a natural convection happening just under the roof sheathing. Cool air is warmed, and being less dense, rises. With a vent at the peak, the air flowing up along the underside of the sheathing exits.
Radiational heat from the sheathing is less strong than convectional heat to air that is in contact with it. As an example, I can be in a room with my radiant propane heater where I am ten feet from it. The air around me is 60 degrees, The air above the heater is 90 degrees. I get somewhat warm, but not as warm as if I had a shelf above the heater to sit on.
A smooth flow of air is efficient. Toss in a fan to disrupt that flow and the turbulence disrupts that.
KB may have been shortcutting, but here is what I sense happening with powered fans in addition to a ridge vent.
First, a fan in an enclosed area creates a negative pressure. Suck on a straw and a milkshake comes to your lips. ANY air in an attic will be drawn to an area of low pressure (the intake of a fan). The density of the air is less important than the low pressure area that a fan is capable of creating. I can suck dirt into my vacuum because the low pressure of the vacuum wand overcomes the density of dirt, bugs, wayward children, and other dense objects. A powered roof vent will disrupt a smooth laminar flow. It sucks.
Secondly, (and TBH a weaker argument) the negative air pressure in an attic can pull conditioned air up and out if there are air leaks.
The takeaway is that radiation is much less of an issue than convection. A simple aluminum foil tin hat can keep your brain from being cooked by radiant heat. Put a clothes iron to the side of your skull and your brain is toast. Absent a foil barrier just above a ceiling, a solar/mains powered fan will be working at odds with a set of soffit vents and ridge vent. (BTW, I hate ridge vents, so I am just giving the devil his due.)
This is a wonderful questioning, and kudos for going there.
There are reasons, but they might not be obvious.
When a roof gets hot in the sun, the underside of the roof is the hottest part of an attic. There is nothing otherwise that adds heat in such an amount. The ceiling of a 75 degree room? Not even.
The vents at the peak of a roof are part of a laminal flow. coolISH air form the outside comes into the soffit vents. It puddles at first, but when the sun hits the roof there is a natural convection happening just under the roof sheathing. Cool air is warmed, and being less dense, rises. With a vent at the peak, the air flowing up along the underside of the sheathing exits.
Radiational heat from the sheathing is less strong than convectional heat to air that is in contact with it. As an example, I can be in a room with my radiant propane heater where I am ten feet from it. The air around me is 60 degrees, The air above the heater is 90 degrees. I get somewhat warm, but not as warm as if I had a shelf above the heater to sit on.
A smooth flow of air is efficient. Toss in a fan to disrupt that flow and the turbulence disrupts that.
KB may have been shortcutting, but here is what I sense happening with powered fans in addition to a ridge vent.
First, a fan in an enclosed area creates a negative pressure. Suck on a straw and a milkshake comes to your lips. ANY air in an attic will be drawn to an area of low pressure (the intake of a fan). The density of the air is less important than the low pressure area that a fan is capable of creating. I can suck dirt into my vacuum because the low pressure of the vacuum wand overcomes the density of dirt, bugs, wayward children, and other dense objects. A powered roof vent will disrupt a smooth laminar flow. It sucks.
Secondly, (and TBH a weaker argument) the negative air pressure in an attic can pull conditioned air up and out if there are air leaks.
The takeaway is that radiation is much less of an issue than convection. A simple aluminum foil tin hat can keep your brain from being cooked by radiant heat. Put a clothes iron to the side of your skull and your brain is toast. Absent a foil barrier just above a ceiling, a solar/mains powered fan will be working at odds with a set of soffit vents and ridge vent. (BTW, I hate ridge vents, so I am just giving the devil his due.)
Thanks for the reply. I thought about a rebuttal that would address issues point by point, but that would take more time than I wish to devote to this. So, I will simply make a few comments (in no particular order) that you can apply as you wish.
First, I don't see any difference, in principle, between hot air rising over cold air when using a fan to help it rise versus letting it rise simply because the hot air is lighter. The lighter objects are going to be the easiest to move as illustrated in my example in my previous post regarding the vacuum cleaner. The exhaust fan is simply expediting the process of the hot air rising faster.
Second, yes, the roof is hot and that's yet another reason why the air closest to the roof is the hottest air. The other reason being, as mentioned, is because the hot air is lighter than the colder air. This is yet another reason why the hottest air will be exhausted first which is our goal.
The only way that I can see that adding an exhaust fan would be detrimental to cooling the attic is if you simultaneously closed some of the intake soffit vents.
As to the claim that the exhaust fan would create turbulence and disrupt the flow of the hot air out of the attic, that would apply only if the fan were directing the airflow back INTO the attic. A properly installed exhaust fan is, of course, directing the airflow OUT of the attic which is what you want.
IF, and this is a big "if", you are convinced that the jumbo exhaust fan that you installed in the attic roof is drawing air IN from nearby roof exhaust vents instead of drawing it from the hot attic through the soffit vents, then the simple solution to that problem is to simply stuff some rags into any nearby exhaust vents. That fixes that problem and, in the meantime, greatly increases your cool airflow in from the soffit vents and thereby lowers the attic temperature which is the goal.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
