Attic venting, energy efficiency, solar powered attic fans, attic fans, vents, venting, tubular skylights, energy conservation, HUD, , attic power vents, solar fans, gable vents

Attic Venting In Your Home



If you are considering the purchase of a solar powered attic fan or a home store fan, I encourage you to read this page completely.  Get the facts before you buy any energy conservation product.

About home store fans: During an energy audit, the customer related he was wary of installing one of our German attic fans proposed as part of our NRG Package.  "My last one caught on fire" he said, "my neighbor was outside and noticed flames shooting out of my gable vent so she called 911.  The fire department broke into my house and put out the flames.  Had she not seen that my house would have burned down".   Then this today (4.15.10)

After posting this, another one came in:

I am sending you the pictures of my attic fan that was purchased at Home Depot about 5 years ago. This was purchased to replace the same exact fan purchased 2 1/2 years prior to this one. So that is 2 fans in 7 1/2 years. The first one I chalked up to a defect, now the second one is a complete different scenario.

The weather has just changed on the east coast and my attic is now heating up to the point where our attic fan is turning on and off with the varying daytime temps. The other night my daughter asked to go out back and have Popsicles, reluctantly I said "yes". Thank God I did. While out back with my kids and neighbor we heard a loud noise, being curious to what it was I stood up and looked on the roof. My neighbor thought "It was probably just a squirrel". I agreed, but he kept looking and asked "Is your furnace running", I said "Nope, I'd hear the exhaust venting if it was". Well then, where is the smoke coming from by your roof?" I immediately stood up and looked into the vent at the gable end of my roof and could see what looked like fireworks on the 4th of July!!!!! I the ran to my garage, grabbed my fire extinguisher, proceeded to our attic access, pulled the pin and aimed right at the motor that had flames coming out the back of the motor!!!!!!!!!!!! I checked the motor and no more flames, good. I then immediately removed the fan from the attic, and found that the cheap motor had seized tight and the blade would no longer turn. If not for my daughter wanting a  10 cent snack, I'd be out of a home or at least a severely damaged house. I know this fan runs late into the evening hours during the summer and I couldn't imagine if this happened while we were asleep!

I started looking for what I think would be the best attic fan and have settled on your German made fans with real ball bearings. I have not been able to find a better quality built fan online. The amount I have spent on these two cheaper fans is almost the same as one of your fans, but the thought of something happening to my family is priceless!
 I sure hope you share this on your website for others to see, I will be ordering one of the fans from you in the next few days. Thanks for all you time.


Thanks again,

Dan Bray

*****If you look close enough at the pictures you can see the charred marks that came out of the cooling vents of the motor.

The importance of venting your attic cannot be overlooked.  In cold climates, improper venting can lead to moisture buildup which causes mold to grow, wood rot in extreme cases or even ice in the attic insulation.   During the summer, stagnant, superheated attic air can dry out your trusses, increase your energy costs for air conditioning and make your house uncomfortable.

How did we become experts on attic venting?  Our patented reflective insulation products reject the infrared heat emitted by hot roofs which in turn makes attics even hotter.  Getting rid of this waste heat then forced us to look at not only how homes are vented, but the US home building codes that dictate what is needed for adequate ventilation.  What we found was amazing.  Codes for attic venting are same all over the US regardless of the climate are designed for moisture egress, not the removal of hot air.  Further, most homes that do have venting have vents that are plugged with insulation (see photos below).

Let's start with an understanding of basic physics:  Hot air rises.  But why?  Heated air rises due to a differential in density (mass), which causes an upward movement of the fluid (air is a fluid).  Like a lava lamp, the colored liquid is heated, rises to the top, cools off (density is increased), then falls back to the bottom.
Think of the force required to raise a hot air balloon off the ground with 10 passengers, the tanks of propane, the weight of the basket and the balloon.   Pretty impressive force if you think about it.   Should be easy for hot air to rise out of your attic right?  Driven by the density differential, the exhausting of the hot air should bring in fresh air where vents are located around the base of the roof (soffit). 
There is no "pressure" that drives hot air out of an attic aside from the increased bouyancy due to being less dense.  The pressure (atmospheric), inside your attic is the same as it is outside (based on a no wind condition).  Wind blown across a roof can create a positive pressure on the windward side and a lower pressure on the lee side.  Only the differential buoyancy of heated air over the temperature of ambient air is different.
Using a tracer gas and smoke generators,  we have documented all types of attic venting, the appropriate sizes that work in hot climates and have posted our findings below.   This is not a scientific study but observations made over two decades the study of hundreds of homes in all types of climates.

Click here to review the UBC code on attic venting.

Our Field Proven Results and Recommendations: (if using a radiant barrier in hot sunny climates)


What works, what doesn't:
CONTINUOUS SOFFIT VENTING
Continuous soffit venting is typically a 2" or 3" slot cut into the soffit into which is placed a manufactured venting system made from plastic or metal.   The plastic is typically molded with thousands of small holes (1/32" in diameter), to keep bugs out.  Great idea, easy to install but falls short of offering sufficient free area to allow air to move.

Another popular type is an aluminum strip with small louvers pressed into them. 
BENEFITS:  Easy to install and attractive.
PROBLEMS:  The holes are too small (see photo below), to pass sufficient air to let the attic aspirate naturally.  Most often these are covered with insulation or partially plugged with dust/pollen/spider webs over time. 
    
 
  This vinyl soffit covering is very popular as it completely eliminates the need for painting and/or maintenance on your home.  Great idea!  Unfortunately, it starves the attic for air and costs you money and comfort.
SOLUTION:  Cut in larger openings (8" x 12"), in the soffit and cover with a screened, louvered grill .  (see photos below)

WHIRLYBIRDS
The correct term is "air motor" , also called roof turbines.  It is thought that the spinning turbine creates some sort of suction which induces air movement.   This has not been proven.   These are called "air motors" as they are used in large commercial applications for venting of smoke and fumes from a manufacturing plant.  The wind spins the turbine which is connected by a shaft to a fan blade below which spins and pulls the air from the building. Turbines used in the residential market do not have these fans and therefore can exhaust only what the roof opening dictates.   Pi times the radius squared equals the area.  A 10" unit offers 78.5" of free net area, a 12"  113" square inches.   Venting an attic using natural aspiration is based on free net area.   Use this to calculate the sizes of intake vents (soffit) and exhaust vents (at the top of the roof).  We recommend Aura Vents for natural venting

Despite the small area of these vents, the vertical stack of this vent allows for the fastest flow of air from a hot attic.  For best performance, these vents should be placed as close to the peak of the roof as possible.

Since our reflective attic insulation products increase attic temperature by the rejection of infrared heat, attic venting has played an important aspect of looking at the big picture.  Getting rid of this heat is very important to reduce energy consumption and increase interior comfort.   We have found through experience that homes with ridge venting are historically the hottest and emails from our customers who have read this site reinforce this over and over.
Puffing tracer gas inside the attic at 2pm just under the opening shows the air in the attic to be stagnant.   Stay away from ridge venting unless your home is built where there is a constant breeze as the air moving over the roof will tend to create a vacuum on the lee side of the roof which will draw the hot air out.

VENTING IMAGES
 

 

 

If you see these balls of sap boiled out of your rafters your attic is an oven due to inadequate venting. This makes your home hot, dries out your structural framing members and is an indication your may be spending too much  to maintain interior comfort.

 
 
 
 
 
 
 
 
 
 
DORMER VENTS 
 

Ridge Venting vs. Dormer Vents
Having installed our reflective radiant barrier in homes for over 18 years we have found that the rejected heat, previously absorbed by the insulation (and passed on later), winds up in the attic making the attic hotter.  Much hotter in fact than an attic without a radiant barrier.   This means the attic venting must be properly sized or install a quality attic fan (seen below), to exhaust the excess heat.  A properly vented attic, be it vented by natural aspiration (adequate soffit vents and properly sized and placed exhaust vents), or a powered attic fan, should be only a few degrees above outside ambient temperature.

Ridge vents are very attractive, easy to install and makes all the sense in the world...they just don't work.  Everyone will agree hot air rises.  Where best to put an attic exhaust vent?  At the peak where the attic air is the hottest? 
Sounds logical except for one basic fact:  Hot air rises, it doesn't go down.  A ridge vent design dictates hot air must fight gravity, travel down from the peak of the roof in order to escape.  This of course is unrealistic and so is expecting this type of vent to be effective.  The only "driving force" that makes hot air leave an attic is the differential density of the 140F attic compared to the more dense ambient outside air.   If you have any doubts (as we did), as to the function of this type of vent, do what we did:  Buy a 2000 CF smoke canister, place it in a coffee can in the center of the attic and light it.  What doesn't happen is just amazing.

The roof you see above was finished being built in December using a continuous ridge vent.  When the hot weather came in April to this Phoenix home, the attic was like an oven despite the fact the intake venting (soffits), were doubled to insure good flow. 
We cut the first hole in this roof about noon to install the dormer vents you see above and the air came out so fast if you kicked the sawdust into the hole it would hit you in the face!  Proof that the hot, stagnant attic air is not being vented properly and being trapped by the ridge vent design.  Further, the steeper the roof pitch, (like homes in Texas or the older Cape Cod homes in the Midwest),  the less the ridge vent will work.  This observation is based on fact, physics and common sense.  Hot air does not fight gravity.  Further, in cold climates, it only takes a few inches of snow to render ridge vents completely useless....when you need them the most to keep the roof from getting warm, melting the snow and creating ice dams.  Inadequate venting is a major contributor to costly ice dams. 


Dormer vents installed on a home in Dallas where the hottest attic air temperature was ever recorded by our NRG Auditor.  Two reasons:
1) The underside of the roof decking was sprayed with silver radiant barrier paint thus lowering the emissivity and increasing the convective currents (and energy use), in the attic space.
2) Ridge vents trapped the hot air.  Ridge vents rely on some unknown source of the universe to drive hot air down then out.  The dormers shown here dropped the attic temp by 42 degrees.  Solution: TCM6 over the insulation and Dormers.

 

 

We have found Aura vents to outperform all others and offer them here:  Click here

 SOFFIT VENTING
Many homes do have soffit vents but are blocked by improperly installed insulation.  Proper attic ventilation is necessary and the products listed below will help.




 
 
 
This is what you may see when you look at your venting around the perimeter of your home

 

 

 

 





Remove the blocking and you can see the fiberglass blocking the vent holes.  Very common problem found during our NRG Audit inspections.

 

 

 

 

 

 

 

This is what is recommended on the outside of the home if you  do not have a soffit.  If you have a soffit, add 8"x12" screened  vents every eight feet of soffit.  These also can be obtained at Home Depot outlets.

This procedure gives your attic the air it needs to vent properly.  In cold climates this equates to adequate moisture removal and the elimination of the associated problems like mold growth and wood rot.  In hot climates, the super heated attic air can flow out the upper vent (if you have them), and draw cooler air in around the house.  This what your architect and builder expected.  However, in most homes the insulation contractor may have plugged up some or all of your soffit vents.  Our home energy auditors have found most homes have this problem.  Check yours or click here to schedule an energy audit (if you live in the Phoenix area),  for your home.  If you have questions about your existing attic vents, take a few digital pictures and send them to us for evaluation.  This will be a free service as we fine tune our online NRG Audit coming soon.  Take advantage of our knowledge and free advice!  Please, no more than five pictures.  Take one of each side of the home noting to make photos of the soffits vents (if any), gable vents (if any), and one or two shots of the attic.

Step by Step Soffit Venting

 

 

 

The soffits on this home were completely blocked making the attic like an oven increasing energy costs and making the upstairs unbearable during the summer.
This is very common in homes of all ages, even brand new homes across the country.



 



Cutting holes in the plywood soffit to allow intake air to cool the attic.  Be sure and snap a chalk line to center the holes you plan to cut or it will look really bad once you are finished.


Once you get the holes cut, simply cover them with 8"x12" louvered grills available at Home Depot.  They are available in white, silver or dark brown.











This attic was sealed like a tomb and the upstairs bedrooms were like ovens.  A German attic fan was installed under an Aura Vent and screened soffit vents were installed. 

The completed installation.  Efficient, inexpensive and lasts forever.   Paint the grills after the installation to match the soffits and they blend right in.  Purchase them here





Homes we have upgraded attic vents on have significantly reduced attic temperatures during the summer.  This means lower A/C bills, more comfort and A/C equipment lasts longer.  In cold climates, these vents allow for the egress of accumulated moisture which can be a source for many problems.

  
 
This is the vent we recommend for proper attic venting, the Aura Vent. 

 Step by step instructions on replacing your burned out, roof mounted attic fan Click here

Roof Mounted Fans Need Exhaust Air To mount this fan under a roof deck we recommend using an Aura Vent of the appropriate size listed below:

 

 

10" German fan:  12" Auravent   Model #AV-12-C4-CN Click here

12" German fan:  14" Auravent    Model #AV-14-C4-CN Click here

14" German fan:  16" Auravent   Model #AV-16-C4-CN Click here

16" German fan:  18" Auravent   Model #AV-18-C4-CN Click here

  

Dormer vents installed correctly on the back side of an apartment building.  The lower vents on the roof are intake vents, the upper vents are exhaust vents.  This type of venting, if correctly sized to the attic size and volume, can adequately vent the hot air out during the summer and moisture during the winter. 
These are not seen from the front of the building and therefore do not detract from the aesthetics.

 

 

 

 

POWER VENTING


This shows a typical home store attic fan installed on a gable vent inside the attic.  Although the mounting looks secure, the application is incorrect since the space around the fan is not blocked off.   The fan will create a negative pressure behind the fan and will draw air from the closest point, in this case, from vent openings around the fan.This means very little air will be exhausted from the attic and most of it will be drawn in around the fan.  
The open area around the fan shroud (the round ring), needs to be blocked off with cardboard or wood to make this type of installation effective.

 

Power Fans:
Natural attic venting is best but rarely sufficient in most homes.  This make a powered attic ventilator is more cost effective, especially in tile roofs. 

 SOLAR ATTIC FANS,  Great idea, not enough power, especially late afternoon when venting is really needed.  

 

We have been importing for eight years, a balanced, powerful, efficient and reliable powered attic fan manufactured in Germany.  This attic fan is unlike any other available.  
It comes pre-wired with an adjustable thermostat and an optional mounting box.  This fan features an external rotor motor to which the fan blades are welded.   This unique design reduces blade flex and vibration and eliminates one of the shaft bearings. 
The bearings are sealed and never need attention.  Install it, set the thermostat and forget about it. 
Costs 2 cents per hour at .10/KWH to operate! 

 

 

                     14" 1800 CFM fan shown here

To place an order click here

            Step by step instructions on upgrading your home store fan with our NRG Systemtm  Click Here

    Construction Features

Specifications
Performance Data
Fan
Model		 RPM Volts Max.
Watts		 Max.
Amps 		0" .100" .125" .25" .375" .5" Sones**
8" PAV 1550 115 45 0.41 304 246 224 74 - - 4.1"
10" PAV
 1500 115 68 0.62 624 558 533 377 132 - 7.9
12" PAV 1400 115 130 1.19 1208 1069 1030 797 - - 9.4
14" PAV 1200 115 245 2.24 1839 1654 1599 1295 - - 9.6
16" PAV 1400 115 458 4.19 3054 2882 2839 2570 2198 1699 12.0
18" PAV 1550 115 698 6.39 4115 3895 3840 3549 3239 2908 14.3
20" PAV
 1100 115 435 3.98 3693 3368 3279 2775 1429 - 10.7
20" PAV
 1450 115* 916 8.39 4949 4682 4615 4274 3917 3445 16.4
22" PAV
 1000 115* 756 6.92 5629 5248 5153 4432 - - 12.
25" PAV 1000 115* 1134 10.38 7858 7355 7230 6567 - - 14.8
** The sound ratings shown are loudness values in fan sones at 5ft. (1.5m) in hemispherical free
 field calculated per AMCA Standard 301. Values shown are for installation Type A: Free inlet fan
 sone levels. All sone values shown are calculated at 0.1" (static pressure in inches W.G.).
 
Fan mounting box dimensions:
8" fan:      10"x10"x4" with a 1" flange 
10" fan:    12"x12"x4" with a 1" flange 
12" fan:    14"x14"x4" with a 1" flange 
14" fan:    16"x16"x4" with a 1" flange
16" fan:    19.5"x19.5"x4" with a 1" flange  

 

Which fan looks like it's more efficient at moving air out of your attic? 
Over the years we have found home store attic fans to be a liability to our installations and the only weak link in our proven NRG Package.  Since a properly installed radiant barrier increases attic air temperature by keeping unwanted heat from getting to the insulation, removing this wasted heat has forced us to become experts in attic ventilation.
Home store fans like the one pictured are under powered, last one year (if that), and the Chinese thermostat is inaccurate, sticks on (or off), creates call backs and problems.  Sure the nice one costs more but like anything else, you get what you pay for.  

Technical support or questions email: ventmyattic@gmail.com.  For the best response, include photos of your venting and several shots of your attic area.  We can help you design the right NRG System for your home.  Be sure and include your address so we know which climate to address your needs.  
 
Warning: In homes that have gas appliances such as water heaters or furnaces in the attic, great care must be taken to insure adequate intake venting (gables/soffits), is provided so as to not create a negative pressure that will draw combustion gasses down the chimney of gas appliances.   Installing an attic fan in this application has the potential for fire or filling your attic with carbon dioxide.  Always consult a professional if in doubt.

  To place an order click here

PRICING OPTIONS:
Price includes the fan with thermostat and 10' of control wire pre-wired to the thermostat which speeds up the installation.  You need only to mount the fan, mount the thermostat on a nearby rafter or truss and bring a 110volt power supply to the thermostat.  Prices below also include UPS ground shipping.
 
PRICING (shipping included to continental states, other areas by quote only)
8"   fan   558 CFM     $247  (for attic space up to 500 square feet)
10" fan   624 CFM     $312  (for attics up to  800 square feet) 
12" fan 1208 CFM     $345  (for attics up to 1375 square feet)
14" fan 1800 CFM     $368  (for attics up to 2600 square feet) 
16" fan 3054 CFM     $444  (for attics up to 3550 square feet)
 
The above recommended sizes are based on an average roof pitch of 4/12.  If your attic is framed higher than this which would create more volume in the attic, order the next larger fan. 
 
If you open the box upon delivery of this item are not totally impressed with the craftsmanship and quality, return it for a full refund.  We'll even pay for the return shipping!  We are that confident of this item.  We do not offer any product on our site that have not been field tested in all climates.

 
14" fan shown here with optional fan mounting box (see below)
We fabricate this sheet metal fan box for our Phoenix installations and thought we should offer it to our online shoppers as well.  
The design allows for a smoother discharge of air as it fully takes advantage of the  aerodynamic  design of  the  shroud and large side flanges makes it much easier to install.   Cuts the installation time in half.   $40 and no shipping cost if included with fan order.

 
 
 
 
 
 
 
 
 
 
 

 
This is how the fan will look when you open the box.   The fan is mounted to the sheet metal box and there is 6' piece of 14 gauge Romex already pre-wired to the fan and thermostat.
We even provide a 2"x4" mounting box to mount the thermostat so all you need to do is run a 115v power supply to the thermostat, mount the fan shroud to the wall, set the thermostat to 105f and call it day. 
 
 
 
 
 
 
 
 

To place an order click here

This just in from a customer in the Midwest:

THE 12" FAN ARRIVED YESTERDAY {Friday June 23, 2006} AT APPROXIMATELY 12:00 NOON BY UNITED PARCEL SERVICE AND I HAD A CONTRACTOR INSTALL IT TODAY {Saturday June 24, 2006} IN THE FRONT PART OF THE GARAGE ABOVE THE DOUBLE OVERHEAD GARAGE DOOR OPENING WHERE A "VENT" WAS PLACED WHEN THEY BUILT THE HOUSE FOUR YEARS AGO.      YES, THE TWO ROOF VENTS OVER THE GARAGE WERE BLOCKED OFF BY STAPLING BOTH WITH A PIECE OF CARDBOARD PER YOUR ADVICE SO THAT THE ONLY AIR NOW COMES FROM THE FIVE (5) ROOF VENTS OF THE HOUSE PLUS THE SOFFITS.     AND YES, THE FAN IS  INSTALLED CORRECTLY BY HAVING IT COMPLETELY ENCLOSED IN A BOX MADE UP OF A PIECE OF 3/4" PLYWOOD {A ROUND HOLE CUT INTO IT FOR THE FAN} AND ALL FOUR SIDES WITH {2" X 4"}.    THERE ISN'T ANY "OPEN AIR SPACES" AROUND THE BOX AS THE BOX COVERS THE ENTIRE VENT AREA PUT IN THE FRONT OF THE GARAGE WHEN THEY BUILT THE HOUSE.
NOTE:   THE OLD FAN WASN'T INSTALLED PROPERLY AND LOOKED EXACTLY LIKE THE PICTURE ON YOUR WEB SITE WHERE IT'S OPEN ALL AROUND THE FAN HOUSING.     ISN'T THAT A SHAME THAT A CONTRACTOR WOULD DO SUCH SLOPPY WORK.     I DIDN'T USE THESE SAME CONTRACTORS AND WOULDN'T RECOMMEND THEM TO ANY ONE.    THE NEW CONTRACTOR DID A WONDERFUL JOB.
  YES, SO FAR THE NEW FAN IS QUIET AND I'M GLAD IT'S IN BEFORE THE HEAT OF THE SUMMER FORBIDS ONE FROM ENTERING THE ATTIC TO INSTALL ONE.   HOPEFULLY THE 12" FAN WILL DO THE JOB AS YOU TALKED ME OUT OF THE 14" FAN SAYING I WOULD BE OVER DOING IT.    THE OLD FAN WAS ONE YEAR OLD AND WAS------"WHISPERCOOL" ATTIC VENTILATOR 1320 CFM, MODEL # 53319  WCGB  12"------AND THE MOTOR WAS SHOT AND WOULDN'T RUN AT ALL.    HOPEFULLY THE NEW FAN THAT I PURCHASED FROM YOU WILL LAST MUCH LONGER AS IT'S QUITE EXPENSIVE ON SOCIAL SECURITY MONEY.   
  THANKS FOR ALL YOUR TIME AND THE VALUABLE INFORMATION.-----------------------------MARVIN

   My purchase of an attic vent fan was a completly good experience. I like your website.....lots of information.   If you could somehow get the price down that would be key to increasing your sales .....until....until..... people "get it"...your product and the packaging it arrived in reminded me very much of the aircraft I worked on....solid, extreme quality, excellent design,  applied correctly to solve a problem........most people will not pay for that....I learned that the long hard way.....very few people will "take a chance" for quality....lots of folks have no clue about saving energy.  Your web site should be read by everyone!

 
regards,
Mark B.
 

If you live in Phoenix, click here to find out about our Home NRG Auditsİ.  For those of you in cold climates, cut your heating bills with our revolutionary Radiant Barrier Chips or our latest patented energy product. Hot, sunny climate homeowners should consider our latest product, Thermal Control Membrane .

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