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FAQ Frequently Asked Questions

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The #1 question: "Won't the fan blow all my insulation around?"

The Answer: No. There is no "blizzard" of insulation created when you turn on the fan. Everything seems perfectly still in the attic. If you put you hand over the moving fan you will feel air blowing upwards, but apart from that there does not appear to be any air movement. It is only at the exhaust vents that you will feel air moving.

1.    What is an attic fan?                                                                                                                     

2a.  What is a whole house fan and how does it work?                                                               

2b.  What is the difference between a belt drive and direct drive whole house fan?            

3.     Which type of fan do I need?                                                                                                       

4.     Are there different types of speed controls for the fans. Is there a   remote controller?

5.     How much power does an attic fan use?                                                                                 

6.     I have a whole house fan, do I need an attic exhaust fan as well?                                    

7.     What types of fans does Weatherseal ( sell?                                                

8.     Why shouldn't I buy a whole house fan from my local hardware/lumber supply store?

9.     What about buying a fan on the internet?                                                                              

10.   Who should install my fan? Can I do it myself?                                                                 

11a. How much venting do I need?                                                                                                

11b. I already have an attic exhaust fan. Do I need more venting anyway?                         

12.   Which size fan do I need?                                                                                                          

13.   Do whole house fans have to be noisy?                                                                                

14.   Do I need to insulate the fan for the winter?                                                                         

15.   The upper level of my house stays hot, even with the air conditioner running all day.  ...Will a whole house fan help me?                                                                                             

16.   Why is my whole house fan noisy and what can I do about it?                                        

17.   What type of maintainance does a whole house fan require?                                    

18a. Why do attics need ventilation?                                                         

18b. Why don't I have enough ventilation?

19. Letter asking about our fans (long answer)

20. Solar fans? Electric attic exhaust fans? Whats your opinion


1. Q.  What is an attic fan?

1A.  There is no such thing as just an "attic fan" but there are two distinct types of fans called attic fans: the whole house fan, described in section 2a below, and the attic exhaust fan (or "powered vent' abbreviated as "PV").

The attic exhaust fan (PV) comes in two styles: a roof mounted version, looking like a mushroom, located on the roof and a gable mounted version, inside the attic behind the vent in the triangular end of the roof. Their purpose is simply to keep the air in the attic from overheating. They turn on and off automatically via a thermostat and pull fresh air into the attic through the existing venting. 

Unlike a whole house fan they do not create a breeze through the house, nor do they remove the hot air from inside the house. In a conventional house with flat 8' or 9' high ceilings, a pv can reduce the temperature of the rooms under the attic by about 5 degrees Fahrenheit. They also remove some heat load from the air conditioning system and allow the house to cool off more rapidly, especially at night. 

These fans work best in a house which already has air conditioning and 8 foot high ceilings. They will help the air conditioning work more effectively. They will not remove the hot air from inside, however. Nor will they bring fresh air into the house or create a breeze through the house. For that, you need a whole house fan.

 2a. Q.  What is a whole house attic fan and how does it work?

 A.  A whole house attic fan is a large, propeller fan that usually sits on the floor of the attic. The fan is framed in with lumber and a hole is cut through the ceiling directly under the fan. A white shutter is placed in the hole and this shutter opens and closes automatically when the fan turns on and off. The shutter allows air to flow from the house into the attic when the fan is running and keeps the attic air from entering the house when the fan is off.

The fan draws air into the house from the open doors and windows, creating a breeze to the fan, removes the hot air in the path of that breeze and blows the air into the attic and then blows the very hot attic air out of the attic through the vents, allowing the house to cool down naturally. The blades of these fans can be as small as 24" diameter to as large as 48".

2b. Q What is the difference between a belt drive and direct drive whole house fan?

A. Belt drive fans transmit power from the motor to the fan blade via an automotive style fan belt. This type of engineering usually, but not always, results in quieter operation. It enables the use of larger blades spinning more slowly to move the air. These fans also use standard motors that can be easily replaced if necessary. Be aware, though, that in recent years, some companies have designed very cheap, noisy belt drive fans. These are often sold at the big box stores and have no advantages over direct drive fans.

Direct drive fans have the blade directly attached to the motor. Since it is difficult to design a motor to spin slowly, the blades on these fans are usually small and flat, causing the fan to operate nosier than a belt drive. The motors are often mounted to the frame using a custom designed system, making them difficult or impossible to replace should they ever fail. 

At this time there is no direct drive fan that can operate without a good deal of noise. currently uses a high quality belt drive, 2 speed fan in all its installations.

3. Q.  Which type of fan do I need?

 A.  That depends on the type of house you have and what you want to accomplish. If you have a ranch house with air conditioning and you want only to reduce you air conditioning costs, then a simple attic exhaust fan is the way to go.

 If you have a conventional two story with a narrow stairwell going upstairs and you just want to reduce the temperature upstairs by a few degrees then a simple attic exhaust fan might work well enough.

 In the following cases, a whole house fan may be a better alternative:

You want an inexpensive, energy efficient way to cool your entire house.                                     

You have a house with an open floorplan, and/or high ceilings and are trying to cool down the upstairs levels without running the air conditioner all day and night.                                   

You want the longest lasting,most cost effective, least energy impactful, most natural and maintenance free cooling system available. 

You want to substantially decrease or eliminate your use of the air conditioner.         

You or your children have become sensitized to the mold produced by evaporative (swamp) coolers or you are tired of all the maintainence required by swamp coolers.

You have a house with extra high ceilings, or an open, cathedral style home and simply cannot cool the upstairs properly, even with the air conditioner or swamp cooler running all day.

You dislike artifical cooling but don't want to put up with an overheated house.      

You want to spend your money on a system that will last forty years and then enable to recover some or most of its installation costs.

In these cases, a whole house fan may be the best solution.

4. Q. Are there different types of speed controls for the fans. Is there a remote controller?

A. The most reliable type of controller for a whole house fan is a discrete two speed switch. These switches almost never fail, unlike electronic, variable speed controllers.  Also, variable speed controllers can only be used on motors specifically designed for them. A variable speed motor used on the wrong type of motor will damage or destroy it and may create a safety hazard.

No true whole house attic fan has a remote controller available for it at this time.

 5. Q.  How much power does an whole house fan use? An attic exhaust fan?

 A.  About the same as 2 to 4 light bulbs, 200 to 400 watts. Much less power than an air conditioner. You can run the whole house fan for 10 summers for the same cost as running an air conditioner for a few months! 

An attic exhaust fan (powered vent or pv) uses even less power, although it runs for longer periods of time. It runs for 6 to 12 hours a day in the summer, using about 50 to 75 watts of power. A solar powered pv uses sunlight and is not connected to the electric system of the house. Neither of these last two fans do nearly as complete a job as a whole house fan, however.

 6. Q.  I already have a whole house fan, do I need an attic exhaust fan as well?

 A.  Probably not, but it won't hurt either. You can use the whole house fan to blow the hot air out of the attic at any time. If you don't want a breeze through the entire house just open a window near the fan and turn it on for a short while. Some customers go ahead and install an attic exhaust fan through the roof in order to provide some additional ventilation and allow the power vent to work automatically. A roof mounted power vent provides 1 sq ft of venting. The new solar powered attic exhaust vents are a clever option but are less powerful than a traditional electric model and do not run well when cloudy or dark skies prevail.

 7. Q What types of attic fans does Weatherseal sell?

 A. We sell only top quality whole house fans that have generations of proven effective and quiet performance, attic exhaust fans, and solar powered pvs.

 8. Q.  Why shouldn't I buy a whole house fan from my local hardware/lumber supply store?

 A. The big box stores tend select the cheapest and most poorly engineered fans available for their customers. These fans have two advantage: they are cheap and they can be returned. They have several disadvantages: they are usually very, very noisy, poorly made, not repairable due to the lack of spare parts, and often not supported by either the retailer, manufacturer or installer. Usually the store that sells them will not install them and will refer you to a third party for installation. If a problem with the unit should arise, no one wants to take responsibility. 

Each summer we remove many of these fans installed the year before because the home owner cannot stand the noise or cannot get them repaired.

Here is an interesting situation: the homeowner is selling the house and the realator tells him to get that horribly noisy fan fixed or have it removed and the hole in the ceiling repaired. Can the fan be repaired? Often only by replacing it with a good, quiet model. The only repair is to replace it completely. Not a pleasant thought compared to originally installing a well made but somewhat more expensive fan to begin with.

Attic exhast fans are a different story, however. There is not much of a quality range in these units and as long as you install a roof mount fan that is ALL METAL you should have no difficulties.

 9. Q. What about buying a fan on the internet?

 A. Many of the fans advertised on the internet are unique and unusually designed. While these fans claim to be "whole house fans" we take issue with that statement. First, most of these fans do not move enough air to work effectively and should not even be considered "whole house" fans. They move between 1000 and 2500 cubic feet of air per minute, not enough to offset the buildup of heat during the day and take forever to cool the house at night.  

The entire purpose of a whole house fan is to move large amounts of air rapidily, otherwise you might as well just turn on your kitchen or bathroom fan to cool your house. This has almost no effect, of course, since not enough air is moved quickly enough to have much effect. A complete air change of all the air in house should occur within four minutes, at least. Our smaller fans move between 5000 and 7500 cubic feet of air per minute, so that you would have to buy 3 or 4 of these much more expensive fans to get the same effect.

Another style of "whole house fan" found on the internet hangs from the rafters of the attic and has tubes leading to ceiling grates. These fans are said to be very quiet, but are also very expensive and solve a noise problem that does not exist!  A normal belt drive whole house fans moves twice the air at less than half the cost and is extremely quiet if engineered and installed well and provided with sufficient ventilation. 

Also, no one has ever been able to resolve this problem: How to move large amounts of air quickly and quietly? The best solution is to use a very large blade, then rotate it slowly. If you use a small bladed fan you must rotate it at high speed in order to move a substantial amount of air.  Small blades = noisy fan or low air volume! Only a large bladed fan will spin slowly and quietly.  So, even though these l fans are touted as "quiet", they are only quiet at their low speed settings, then they move even less air!  

Also consider this: most of these fans have short (3 year or less) warranties and have not been on the market very long. Will parts be available 10 years from now when you need to fix the fan? Will anyone be around who knows how to fix it? Do yourself a favor and stay away from these "fake" , expensive, and mainly ineffective "whole house" fans.

Visit our fans compared page for more opinion & information.

 10a. Q. Who should install my fan?

 A. You best bet is someone experienced. While some homeowners may be able to do the installation, it is rare that they are familiar with all aspects of whole house fan installation. The same thing goes for the local handyman, electrician and plumber. And if you don't get a substantial warranty, how can you trust them to do the work properly?

10b. Q. Can I install it myself?

 A. If you like, we will be happy to just sell you the fan and all necessary components. We will be available for a free telephone consultation if you run into difficulties.

 11a. Q.  Do I need more venting? If so, why?

 A.  Most houses already have 1 to 3 feet of venting originally installed by the builder or subsequent owners. This is enough only for the smallest of whole house fans. Lack of sufficient venting means that the fan will try to blow more air into the attic than can get out in time. Think of people trying to force their way onto a bus quickly in the front while others are getting out the back slowly. There will be a backup. The same thing happens with air molecules: some will get out but some will just be compresses and push back against the fan blades and shutter. This will cause a loss of air flow, increased noise and reduced fan life.

 It is not important where the ventilation is located. The fan will blow the air out of the attic no matter where the vents are located, as long as the air path is not blocked off.

11b. Q. Which size fan do I need? How much venting do I need?  

Fan Size   House Size           Air Movement cfm        fan rpm       sq ft venting                        .........................................................................................................low/high 


24"              to 900 sq ft                  3500/5200           425/635                2 / 4

30"              1000-2400 sq ft           5000/7500           340/510                4 / 6

36"              2500-4500 sq ft.          7000/10,500        315/470                6 / 9 

42"              over 4500 sq ft                                                                     9-12

If you are interested in running an extremely quiet fan, consider having a larger fan installed that you would be likely to run at the low speed, yet it would move as much air a does the next smaller fan at the higher speed. 


12. Q. I already have an attic exhaust fan. Do I need more venting anyway?

A. Probably yes. An attic exhaust mounted through the roof usually requires a 14" diameter hole, or one square foot hole. Even though there is now an electric motor and fan blade, the hole is still only one square foot in size and that is how much venting it provides.

13. Q. Do whole house fans have to be noisy?

 A. No. But there are several problems that cause whole house fans to be noisy.

 1) Most fans sold in the big box stores are inherently noisy to begin with! They are usually poorly engineered in order to produce a cheap fan. If you buy any  badly designed or built product it will perform poorly. A cheap whole house fan will be more expensive and aggravating in the long run than a well made fan.

 2) Most shutter are poorly made and rattle when the fan is running. See 1) above.

 3) Most installations are poorly done. Even the manufacturers' instructions are inadequate and are written to make the fan easier to install, not to operate at minimum sound levels.  We have been installing fans for over 30 years and have learned how to install them so that they operate quietly.

 4) Many attics are not ventilated properly for whole house fans to operate quietly. If the air cannot exit the attic quickly enough the remaining air in the attic will cause backpressure against the fan, causing it to run more noisily.

 By appreciating and correcting all these problems, a good whole house fan will run very quietly (46 db on high speed) and have a lifespan of something like 30 to 40 years! Quiet operation means that you can have a conversation standing directly under the fan without raising your voice and even being able to speak to someone in a whisper standing directly under the fan while it is running on low speed.

 14. Q. Do I need to insulate the fan for the winter?

 A. It is not essential, in that a good shutter will prevent  heat and air loss into the attic and keep cold air from entering the living area of the house. However, if you want a simple way to increase the energy efficiency in the winter, simple cut a piece of foamboard, available in most hobby, office & art supply stores, to fit the shutter. Use self-stick velcro to attach the foamboard to the shutter. That way you can simply remove the foamboard from the shutter from inside the house whenever you want to use the fan.

 A more elaborate system would be to insulate the fan in the attic using a blanket thrown over the fan or even an insulated box build around it. While we are aware of the need to converve energy, we feel these methods, while functional, are somewhat excessive.

 15. Q. The upper level of my house stays hot, even with the air conditioner running all day. Will a whole house fan help me?

 A. A whole house fan is probably the only economical way to solve your problem. As you recall from 3rd grade: hot air rises, cold air falls. That's the reason that air condtioning and evaporative coolers have such a difficult time cooling the upper levels of a house. By blowing out the concentrated hot air upstairs as well as the super-heated attic air, a whole house fan effectively reduces the load on the air conditioner, allowing it to work more effectly and, on some days, eliminate the need for it altogether.

16. Q. Why is my whole house fan noisy and what can I do about it?

 A. There are 4 elements that combine to make a whole house fan noisy or quiet: 1) the basic engineering of the fan, 2) the quality of the shutter, 3) proper ventilation and 4) the basic installation of the fan.

 Poor engineering means that the fan is made to run fast in order to move lots of air. It is more difficult (and expensive) to build a fan that spins slowly and quietly and still moves a substantial amount of air. If the fan is badly designed then it will be difficult or impossible to reduce the noise level.

 Most fan manufacturers include a ceiling shutter that is guaranteed to be noisy. Made of flimsy materials, it lies directly in the air pathway and is prone to shaking and rattling. The solution is to use a heavy duty shutter that is actually made to withstand the intense wind without making a racket. Replacing a shutter is difficult since every manufacturer makes a different size shutter for the same size of fan.

 Without proper ventilation, instead of being expelled, some of the air being blown into the attic is compressed and pushes back against the fan and shutter, increasing the shutter chatter and overall fan noise. A quick test is to remove the attic entry hatch and run the fan (be sure to put down a cloth or tarp since some insulation might be blown out). Listen carefully. If the sound with the hatch open is noticibly quieter than with the hatch closed, it is clear than the attic is not properly vented and more ventilation should be added. If there is no change in sound it might still mean that the attic is under vented, but that the shutter noise will not be much affected due to poor quality.

 The installation of the fan must be vibration free with no loose screws or nails. Rubber mounting of the fan is also suggested. If joists or trusses are cut they must be properly reinforced. Since all this work is done in a part of the house not normally accessed by the inhabitants, some companies take short  cuts and do improper work, resulting in excessive noise transmission through the house. Clearly the solution is to do a proper re-installation of the fan and use a more reliable company next time.

 17. Q. What maintenance does a whole house fan require?

 A. Little to none. If you have a belt drive fan then the belt will have to be replaced eventually. Their lifespan is somewhere between 5 and 20 years. When they age, they begin to crack and eventually break. You will begin to hear a thumping sound as the cracked sections pass over the pulleys. These are ordinary automotive type belts and can usually be purchased at a local auto parts store. Just remove the old belt in and replace it with one the same size. Do not overtighten the new belt: it should be just tight enough not to slip when it rotates over the pulleys.

 If you change the belt, check to see that all the screws and bolts are still tight, especially those holding the pulleys as well as the motor to the fan housing.

 Occasionally wiping the ceiling shutter slats keeps them clean and operational. Excessive dirt build up usually means the fan is under ventilated or that the vents have gotten clogged up. Check for debris in the vents caused by wind or critters trying to nest.

18a Q. Why do attics need ventilation?

A. The attic, being an enclosed area, can be prone to moisture buildup. If there is no way for this moisture to evaporate, the roof and attic structure can be affected and long term damage created. It would also be possible for mold to grow in the attic and possibly adversely affecting the occupants.

18b Q.Why don't I have enough ventilation?

A. Ventilation is not installed to cool the attic, only to prevent moisture problems. Often attic ventilation does not even meet minimum building code requirements. This does not usually create any difficulties. However, when adding a whole house fan it is usually necessary to add more ventilation for the fan to function at full capacity. 

A whole house fan pulls a large amount of air into the house through the open doors or windows and ultimately all that air is blown into the attic, through the shutter in the ceiling. It is the size of the shutter that indicates the minimum amount of window opening as well as the minimum amount of attic exhaust venting.

If there is not enough venting, the fan will still function, but not as well as it would with adequate ventilation. Imagine driving a car in first or second gear: it would take you everywhere you wanted, but without the performance built into it and with more stress and wear and tear on the engine. The same is true for an undervented whole house fan. With enough venting, a whole house fan will run effectively for many years. Without it, it will never perform as it should, be more noisy and prone to premature breakdown.

19.Q:  I am researching fans for my house. I have two levels w/ roughly 1900 sq. ft.and generally 9 ft. ceilings. Our downstairs opens on ground level, as does the upstairs, as we are on a slope. We get a good late afternoon breeze most days and a whole house fan would really augment it. I would like to do the install myself.

So, how can your fan, which looks like the old monsters that suck enough air to blow doors shut and roars and shakes the whole house, be a good deal? How have you made it quiet, what are the decible levels, how do you provide vibration control? How do I insulate the opening during the winter?

Why should I buy your fan instead of a Tamarack or Quiet Cool? (And, yes, I have read your whole website, so I know your comparison opinions.)

Thanks, I look forward to hearing from you.

J. C., California

A: The whole point of a whole house fan is to move enough air through the house to cool it down. If you turned on your bathroom fan, it would employ the correct concept, but it would not work because not enough air would move through the house.

The question is: how much air do I need to move?

The answer is: move out all the air in the house in 2 to 4 minutes and you will cool it down. That's what our fans do.

Your house has about 17,000 cubic feel of air (9 x 1900) so you would need a fan moving about 5600 cfm to do the job properly.

Our 30 inch fan moves about 5000 cfm at a rotational speed of 340 rpm (low speed) and our 36 inch fan moves about 7000 cfm at a speed of 315 rpm. 

It is the speed of the blades that is the main factor in creating the noise of the fan. The Tamarack fan is rather noisy for the amount of air it moves but is quieter when you slow it down. Unfortunately, you lose air flow. The Quiet Cool is actually noisy, but is hidden away up in the attic so you don't hear how loud it is. For about twice the cost of the 30 inch fan, the Quiet Cool moves about 1000 cfm less air. Also, both these fans use exotic parts and engineering and will be a nightmare to service, should service even be available.

I have seen the same exact fan we sell working properly after 55 years of operation, with only a belt change. Belts need to be changed after 15 or 20 years. As they age, they will begin to crack and cause the fan to be noisier. The belts can last over 40 years but will create more and more noise as they deteriorate.  New belts can be purchased at Ace Hardware or any automotive store. All other parts & components, including the motor, are standard and are easily maintained or replaced at minimal cost.

A noisy fan is caused by several factors:

1. High blade speed 

Solution: large paddle blades, slow rotation, large air movement

2. Noisy shutter

Solution: high quality shutter, heavy, steel reinforced slats, spring loaded system

3. Lack of sufficient attic ventilation

Solution: minimally provide as much attic ventilation as size of shutter hole

4. Fan vibration 

Solution: properly balanced blades, rubber mounting of motor, blade and fan housing

5. Poor installation 

Solution: heavy duty installation spreads weight of fan over large area. Use screws, not nails.

Loss of heat through the shutter: the expensive Tamarack fans are well insulateed but they are crappy fans that don't move enough air to do the job. The Cool Attic is not insulated. To insulate our fans you simple get a sheet of foamboard, cut it to fit the shutter on the living side of the house and attach it to the shutter using self stick Velcro or screen clips for the winter. This will cost about $10 and looks factory made. Most of our customers don't bother, preferring to spend an extra $5 or $10 a month for the convenience of not having to stand on a chair to remove the cover if they want to use the fan in the winter months. The fan can be used for removing odors and stuffiness throughout the year.

Our fans address all the issues above. They are also rubber mounted in 5 different areas (top and bottom bearings, top and bottom motor housing, and around the entire wood/metal perimeter). This results in an extremely quiet system (46-50 decibels) at reasonable cost using a fan that will last the life of the house. Our installation instructions require about 50 feet of 2x4 or 2x6 lumber and the use of 60 - 80 3 inch screws. While straightforward, the downside is that this is not a simple installation.

Most of what you encounter with Tamarack and Cool Attic is excellent marketing and an inferior product. If we felt the product lived up to the actual requirements for cooling the home, we would sell and install them. We would make more money and not have to explain how much better are these large, old fashioned fans.

The problem with the old fan you experienced was that it was poorly made, not well installed, not properly ventilated, or the belt had gone past its prime. Engineers have known how to build effective air moving equipment for over 100 years and do it quietly. Most people just buy cheap, noisy fans from the Big Box stores, then complain how noisy they are. Very unfortunately, based on our experience of installing fans for almost 40 years, we find that most installers, including contractors and handymen, do not have the knowledge, nor do they usually care, to do a superior installation.

20. Solar fans? Electric attic exhaust fans? What’s your opinion

An attic exhaust fan is a small fan that is meant to only blow the hot air out of the attic.

For many years they were only available as a standard electric unit that would be automatically controlled by a thermostat. In the past few years, small solar panels were attached to these fans. Many people call these “solar attic fans” while the electric units are referred to as “attic fans”. While they are both types of attic fans, the true descriptive name is “attic exhaust fan”. 

We do not recommend installing these fans, since they are not very effective in a house with current insulation standards.

1. Solar fans spin at top speed when then sun is shining brightly. When clouds pass over the sun, the fan slows down. When evening approaches, the fan slows down. When the sun goes down, the fan stops running completely. These fans do not run nearly as well as a standard electrical attic exhaust fan which can run into the night while trying to cool the attic. Even at top speed, the solar fans only move about half as much air as a conventional electric exhaust fan. The cost of electricity of running a standard attic exhaust fan is probably less thant $5 -$10 a year! The primary purpose of the fan is to make the homeowner feel good about going “solar”!

2. Year ago, when attics had only 3 inches of insulation, a hot attic would allow the heat to penetrate the insulation and heat up the rooms below.

Now that most houses have 8 to 16 inches of insulation, it’s almost impossible for the heat in the attic to penetrate through and affect the temperature of the rooms underneath.  

We feel that an attic exhaust fan will not reduce the heat load to any appreciable degree. The only benefit they can provide is when there are air conditioning ducts running through the attic. These pipes often have very thin insulation around them. By reducing the heat in the attic with an exhaust fan, it might prevent these pipes from heating up and allow the air conditioning unit to work more effectively.

Note: the opinions expressed throughout this site are those of If you want to express your own opinion please use the contact us page and we might post it on this site.

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