Attic Venting for Metal Roof

Metal roof.

Attic Venting and Installing Exhaust Fans

I have a new house with a metal roof and without a ridge vent. Please recommend a vent system without cutting holes in the metal roof.-Bjorn

Hi Bjorn,

That would depend on the style of roof you have. If your house has a gable roof, you can install a vent in each gable then mount an exhaust fan in the attic behind one of them that is controlled by a thermostat. If you have a hip roof, you would either have to replace the existing ridge with a vented one—making sure the roofing and sheathing at the peak are cut back so air from the attic can escape through it—or mount a power vent fan on the roof itself, which would require cutting a hole in the roofing.

If you decide on a roof mounted fan, position it high up on the back of your roof, but not so high that it is visible from the front. Solar powered models are available that don’t require wiring, though they are more expensive than hard wired ones. Be sure the soffit under the eaves is vented so outside air can enter the attic.


  1. Hi,

    I would like to install a roof mounted, solar powered attic exhaust fan (although the incline is fairly steep and maybe I should hire a roofer) and was looking for a step-by-step procedure describing the removal of/and replacement of the asphalt shingles. I’m just a bit unsure of proper measurment, cutting and reinstallation of the shingles (ie. overlap, etc). Thanks!


  2. I have an older room in my home. I live in the trailer that is attached to the “bowling alley” ( this added room, which is fairly large; in which we have had to seal the fireplace (Rock); because the dampener is broken, put a plastic box over the top of the chimney and use black solid duct insulation to completely close off the fireplace.
    The windows in the “Bowling alley don’t open, are the “argon” double thickness.. this room is freezing in the winter & you could bake bread in it in the summer.
    The kitchen in the trailer is rather a Maze with an old built-in stove with oven over ( that the thermostat doesn’t work.) in back of this ancient stove there is this “Kitchen island” that is useless other than holding up the microwave.
    I Know this sounds like something I should just move out of; but with todays’ economy We Just can’t afford it.
    ( we are both disabled and don’t have the $$$ to spare to move, put down new deposits on the new house, Utility s etc.
    We could really use some help, Danny
    Thanks.. Sarah

  3. Can you effectively use both gable vents with ridge and soffet vents. I was told that you should not use all three. Any answer?

  4. because the dryer vent goes up into the attic and travels over twenty feet, I am considering venting into the garage which is on the other side of the laundry room. Any siggestions on what to consider? Should I put the vent up a few feet to prevent rodents getting into the house?

  5. Danny,

    I want to install a air vent fan in my toolshed which measures about 17′ long x 9′ wide x 12′ high. It has a rollup door and two windows above on either side. Will your installation guidelines for installing one on a house apply to this kind of structure? Thanks.

  6. Hi Danny, due to the heat that builds up in summer (and the corresponding skyhigh electricity bills) I’d like to install a power mounted roof vent. I am fairly skilled and do not mind working on the roof. I was just up there and noticed that the roof has ridge vents. I’m wondering whether a powered roof vent would just suck the hot air back in that it blows out of the attic. The ridge vents are small in cross-section and the attic does get pretty hot in summer, so I think that even if the vent sucks air back there is still a benefit. Any advice on this issue?

  7. Currently I have ridge vents and soffet vents but in the warm weather my second floor gets unbelieveable hot. This is also were the thermostat is for the central ac system that I have.I’m thinking of installing a power roof ran to help get the hot air out of the attic and the second floor. What would you recommend I do??

  8. I am about to reroof my house and want to make sure the venting is correct. Right now, there is no ridge venting, but there is a powered fan in one gable. Do both gables need a fan or will one pull enough air from the eave vents? It is a pretty large attic with a steep roof. Thank you.

    • Hi Diane,
      If you have soffit vents under your eaves, or some other way for air to enter your attic in addition to the two gable vents, you could put a gable vent fan in the gables at each end. If you don’t have another intake source for outside air other than the two gable vents, you should only have a fan in one gable vent (blowing out), since the other gable vent is used to draw air into the attic.
      Good luck with your project!

  9. We recently reshingled our roof, removed the attic fans and installed ridge vents. There are gable vents on each end of the house and soffit vents. Will this setup work the way it is supposed to? If not, what do we need to do? Thanks!

  10. Hi Ben,
    I have a hip roof without any type of intake vents. There are two static, low profile vents on the roof and a single turbine vent. I was thinking of adding a fan to help remove the very hot air from the attic, but without any type of intake, would that work? Can a fan be added to or replace one of my existing vents?

    • Hi Dave,
      You need to be sure you have way to take enough air into your attic before putting in a power vent. The intake should preferably be near the bottom of the attic, but doesn’t have to be. For example if you had a triangular gable vent on each end of your house, you could put a fan blowing out in front of one and use the other as the intake. Depending on where your vents are located, you could take out the one high up on your roof (turbine?) and use the others as intakes (if they provide enough intake area). Since they will be drawing air in, be sure rain will not be a problem.

  11. recently installed a power vent (heat and humdity controlled). Our last 2 electric bills have tripled. Is this the vent? Are they that energy hungary? The settings are 105 degrees and 50 humidity.

    • Hi Debra,
      A typical attic power vent fan only draws about 2 amps of electricity, which equals 240 watts per hour (2 amps x 120 volts) or about a 1/4 kilowatt an hour (240 watts/hr ÷ 1000 kilowatts/hr). At an average price for power of $0.10 a kilowatt, your fan uses about 2.5 cents of electricity an hour ($0.10 x 1/4). If it ran around the clock, your attic vent fan would use about $18 of power a month (730 hours/month x 0.025). If it only ran during the day when it’s hot, it would use about half that much. Hope that helps!

  12. Thanks this helps alot-I need to look into why my is costing so much–or if there is somethng else drawing all electicity

  13. Hi, looking to install a power gable vent in the attic , already have vents there but living here in hot and sunny Florida it gets really hot up there , have checked them out, but wondering what size electrical wire I should use to wire up the fan. 14/2 or 12/2? Thanks

    • Hi Bruce,
      Most power vent fans draw around 2 amps, and 14 gauge wire is rated for 15, so it should be fine, but I would check the info or manual that comes with the fan as to wiring size and the number of amps the fan draws to be sure. Also, you should use grounded wire (14/3), and properly ground it at the fan and circuit breaker box. Good luck with your project!

  14. My husband is thinking about installing a window ac unit,in our finished attic office, by cutting a hole in the wall, to the unfinished portion of the attic, to vent… Since the attic gets so hot, would the AC unit even be able to cool the room that its installed in? Also, would condinsation be an issue in the attic? He thinks he can put a catch basin beneath the AC unit and plumb that to the outside for drainage… Thoughts? My husband is handy, but this all sounds a little odd to me…

  15. Hi Bruce,
    My husband and I are trying to replace our 100 year old slate roof with gaf shingle. When getting quotes, we started to discuss venting. We have a Cape Cod with multiple roof lines and the attic portion is converted living space, except for the very top roofline, which is an approximately 4 foot space with gable vents on either end.
    The concern is there is no way to vent the roof through soffit vents or even smart vents, they won’t communicate to the roofline (if we put in a ridgevent for example). So, do conditioned air spaces, ie converted attic space, need to be vented? If they don’t need venting, then just the gables should suffice with a fan at one end, or just the gables with a ridge vent will work, correct?

    We really appreciate your advice, thank you

  16. added on to previous question:
    we have not had any issues with moisture build-up or ice damming (except for back to back blizzards this winter!), so does a slate roof naturally breathe and we will face these problems with no venting and a gaf roof? thanks!

  17. Danny, I have a row house, mine is a middle unit, here in D.C.the roof has a power vent fan and not much of any kind of soffit(less then 9″). This winter is very windy and could feel cold air radiating from the walls. The rafter insulation is loose fiberglass and stops about a foot from going all the way out to the soffit edge. What should/how do I get proper air flow up there and still cut that air from seeping between the walls?

  18. I need to have my Attic Power Vent replaced. Do replace them? My house is about 18 years old and has 2000 sqft. w/double garage. I live in Athens Ga.

  19. Danny,
    We have a 1914 home with a slate roof. The partially finished third floor gets so hot in the summer time that you cannot stay up there for more than 5 minutes at a time. Also, the attic space above the third floor is not insulated. We are considering having a powered roof vent installed as well as soffit vents and insulating the attic floor. Would insulating solve our problem alone or should we still have the powered ventilation fan installed?

    • Hi Brett,
      If you don’t have any ventilation or insulation in your attic, I would start by tackling those two projects first, and see if that solves your problem. If not, you may need to add a power vent fan to the attic. Good luck with your project!

  20. Hi Danny,
    I’m looking to install a gable exhaust fan in my attic within the next few days (to beat the summer heat). Because the attic isn’t a frequently visited place in my home, I would like to purchase a top quality gable fan that is “maintenance free”(i.e. permanently lubricated motor) and will last many years. What is a top/highly recommended gable fan company(s) that you’d recommend?
    (Note: Doesn’t need to be limited to brands found only in the major home improvement stores) I’ve been told by numerous electricians that Lomanco makes a top product.

    Thank you.

  21. We have a home in Hattiesburg, Mississippi. It is a 1 1/2 story with sprayed in cellulose insulated walls and 14″ blown in cellulose ceiling. The downstairs is 2100 sqft and the upstairs is 1300 sqft. The roof has a 10/12 pitch. It has Georgia Pacific Radiant Barrier Sheeting and vinyl air channels between the rafters from soffit and 2 large porches to attic. (90 7×10.5” channels). The porch ceilings and soffit are 100% perforated vinyl.

    I’ve just discovered that the builder failed to cut the sheeting for the installed continuous ridge vents. There is no ventilation at present. I need to find out what I should do to correct this and found your web page. My attic temperatures are not excessive, but could be improved. It appears the radiant barrier works well. Also, I am concerned about mold/mildew possibly forming due to possible excessive moisture. It is dry at present and has no problems.

    I recorded these temperatures yesterday with a remote thermometer:

    Outside Attic Var

    07:00:00 AM 78.6 75.2 -3.4 Overcast
    08:12:00 AM 80.2 76.1 -4.1 Overcast
    09:12:00 AM 82.2 75.9 -6.3 Overcast
    10:18:00 AM 84.0 82.6 -1.4 Overcast
    11:21:00 AM 85.1 87.3 2.2 Overcast
    01:30:00 PM 88.2 96.1 7.9 Sunny
    02:36:00 PM 90.1 102.9 12.8 Sunny
    03:37:00 PM 90.5 105.6 15.1 Sunny
    04:32:00 PM 91.2 106.3 15.1 Sunny
    05:35:00 PM 90.5 106.2 15.7 Sunny
    06:30:00 PM 89.2 101.8 12.6 Sunny
    07:30:00 PM 87.8 94.1 6.3 Sundown
    08:20:00 PM 86.0 86.9 .9

    Should I use power gable exhaust fan or roof mounted power exhaust fan? I assume I do not need intake vent in the attic due to adequate soffit vents.

  22. Danny,
    We are researching proper venting for a 100+ year old church. The church has only gable vents (approx. 24 sq.ft total)and a history of pealing paint on interior walls. The approx. 60’x80′ attic with an 11/12 roof pitch looks like it needs around 4500 CFM of fan venting. The existing heavy duty well built 48″ belt driven fan (30 years old) is not operational (missing fan blade) but looks to have been too large depending on the blade pitch. With the motor rpm and pulley ratio, it rotated at about 160 RPM. Do you suggest we look for a replacement blade or replace entire fan assembly for 4500 CFM venting if this is the correct amount. At this time we don’t know how well sealed the air conditioned and heated sanctuary is from the attic but there is some attic insulation. Since we are limited to the structural changes that can be made due to historical preservation we are looking at our options to reduce attic heat and moisture. Any suggestions you have would be welcomed or if you can suggest any local contractor with this expertise in the Charleston, SC area we would appreciate it.
    Thanks You for any help you can provide.

  23. Hello My name is ulysses and I have a question Or two, about a Baptistry We have,We notice that , after We put installed,a heater in the baptistry,that a lot of moisture build up was evident, an mold began to grow on the walls Question is can We do to Be rid of this, situation,I believe that a exhaust fan is needed ,or maybe some type of ventilation, system, can you help.

  24. When calculating the NFA of a soffit or fixed screened gable vent shouldent I reduce the actual size by 50%?

  25. Hello,
    My home was built in 1984 and is 1320 sf. I only have gable vents, and a small 8 foot section of ridge vent. No vented soffits. What should I do? I am thinking of just adding a attic fan at one gable end?

    Thank you for your help.

  26. Help! I have a split level house. A new roof was put on about 6 years ago with an attic fan, that is vented. I just found out that the roofer never installed any venting( a ridge vent was on his proposal). There are no soffit or gable vents. I got some leaks and called for estimates and then found out about the venting. The roofers giving those estimates disagree on what venting I should now install. One wants to install 4 louvre type vents and the other just a ridge vent on the lower peak of the split. What should I do?

  27. Can you install an exhaust fan part way down a roof slope? I have two rooms that are not service by the current exhaust fans, and are always very hot in summer. Air conditioners are running all the time.

  28. Hi! Just west of Knoxville TN on Watts bar lake facing south: we have a “attic” cavity between a 3:12 porch metal roof and our 6:12 dwelling roof/ceiling. the cavity has no vents or ventilation. with 5-15F this week water is leaking out at the roof line outside. it actually froze. the triangular profile is about 8 feet wide and 3.5 feet hi at the wall between our dwelling and the porch. the total cavity length (wrap-around porch) is about 90 feet, 55 feet straight (south) and 16 feet on each end west/east.
    The ceiling interior is recovered 75 year old 3×12 Douglas fir on side, covered with tarpaper moisture barrier, then spray PU foam 3-4 inches thick. Sounds tight but the 40-45% Rh inside apparently leaks through it, hits the below-dewpoint metal and drips down to the cracks it finds to the outside. Leaks seem worse on east and southeast. I cannot access this space without ripping metal roof off – builder did not think about it being closed cavity.
    Help me size two “attic” gable fans on each end (no way to put a top vent: it is the 6:12 to 3:12 roof transition); what is the appropriate size and number gable inlet vents along the length? This to keep the air moving and close to the outside so we quit this condensation – like passive soffit vents. Have to have much more than the fan(s) exhaust. What controls to put on the fans: thermostat, humidistat, high temp cut off (fire protection)?
    Thanks Much!

  29. installed a metal roof over shingle roof with wood strips over shingles now its sweating any way to fix this problem the ridge cap is insatalled with foam to seal out rain and snow

  30. I am a roofing contractor. I care a lot about attic ventilation. I haven’t been able to figure out a cheap way to install a intake system on a standing seam metal roof to vent the attic on a hip roof with soffit board on the overhang. The soffit is not vented consequently the bird blocks in between the trusses are solid with no holes. Even I am able to make an opening on the soffit and be able to install any kind of louver or grill, air would’ flow because of the solid bird block blocking the flow of the air. My thinking is to be able to install several intake vents on the metal roof. They would have be to easy to install without working or shaping the metal panel to much and it would have to be water tight fiscally not depending on the sealants in order to make a free of maintenance metal roof and keep the cost down. Any ideas?

  31. i have a ridge vent that was installed improperly and only one side is open. 1 year after it was installed the plaster cracked in the kitchen and bathroom. 10 years later the plaster cracked again so insulation in attic was blown in and it has soffit chutes. the wall in the hallway now have condesation along with condesation along perimeter wall. plaster in hallway, kitchen and bathroom it cracking. learned at that time ridge vent in closed on on side. do i need ridge vent opened on electric fan? also the garage is attached to the house and it is rafters only, no ceiling and the hallway has an attic fan which is disabled.

  32. I have a metal roof (with fasteners) on a 4 / 12 pitch roof. It has a ridge vent as well. As you can imagine, living in Canada where there is plenty of snow and cold weather, the ice build up, especially along the edges is pretty significant. The house has a cathedral ceiling and the metal roof becomes like a grilling skillet, if you know what I mean. The heat that escapes from the ridge vents melts the snow and runs down the roof, eventually solidifying as ice build up. I was wondering if I should install additional vents, in particular “maximum” vent models, in those areas where I know exactly where the maximum heat is accumulating and escaping through the ridge vents. My roof is approximately 900 square feet. How many of these “maximum” vents should/can I install?
    thank you.

  33. I am having my 25-year-old hip roof shingles finally replaced with a standing ridge metal roof, today. The roof will be installed right on the decking which has already been prepared with a 3-foot-wide layer of ice and water shield at the 4 soffit edges. Then a drip edge was installed at the soffit edges. Finally, t ice and water shield was put over the whole thing. The metal will be installed next.

    The roof has always had ample soffit venting but NO “attic” venting. It’s been dry as a bone for these 25 years.

    To keep it bone dry, should I:

    a) leave the roof with NO RIDGE VENT?
    b) put in a ridge vent? (size formula?)
    c) put in a “Maxivent?” (size formula?}

    Please advise.
    L. Richmond

  34. I have a metal poll roof that has been built over a shingled roof. The new metal roof has a steeper pitch which makes the ridge cap about 5ft above the shingled cap. They’re is 1in. Styrofoam insulation directly under the metal. I have condensation, will gable vents and attic fan help?

  35. A metal roof was installed over my shingles roof-something that looked like white plastic paper was stapled on top of the shingle roof before the metal went on. We have the attic insulated and also radiant barrier on the ceiling of the attic. There is a square metal ventilation under the pitch of the roof that is over the 2 car garage and which is also part of the attic We are concerned about proper ventilation so the attic doesn’t get too hot in our hot summers in south Texas. Something that looks like 2 plastic pipes are sticking out o f the back part of the roof-they had covers before, BUT don’t have any thing covering them now. Do they need to have covers? Will water get in when it rains? Is this enough Ventilation for our attic?

  36. We live southern Baja MX, off the grid. We have a metal roof, insulation, but no attic. Ceiling goes from11′ to the peak of room at 14′. What would be the best fan to get the HOT air out?

  37. I have a 2300 sq ft attic in a 1 1/2 story home, 36′ of ridge vents and soffit vents. The attic gets over 115* in the summer and we cant use our two upstairs bedrooms when it gets over 85* outside. The roof is a 6/12 pitch, so it is over 15′ tall at the peak. We live near Omaha, Ne.. Want to put in a venting fan, but wanted to ask your opinion first.

  38. A contractor installed a typical exposed fastener raised seam metel roof over the existing shingles. He didn’t remover the existed shingled ridge vent but went over the top of it with the panels and a metel ridge vent. Will this be ok?

    • Hi, Joe,
      Danny says, “As long as the airflow has not been interrupted, it should work just fine.
      Thanks for your question!”

  39. I have read several sources that say that attic fans can cause downdrafts which affect natural gas appliances and can cause carbon monoxide in the home.

    “House depressurization is a major problem. Homes in the ISU studies have had downdrafting problems caused by depressurization. Exhaust fans, recessed ceiling lights, roof-mounted attic fans, fireplaces, heating appliances, open windows on the lee side of the house, and leaks in return air ductwork can result in CO problems.”
    (IOWA State University: House depressurization is a major problem. )


Please enter your comment!
Please enter your name here