How to Prevent Attic Mold From Growing (If It's Not Too Late Already)

Updated on April 21, 2019
Home Maintenance profile image

I’m a retired Illinois home inspector, and I've crawled through the attics and crawlspaces of Chicagoland homes for over 12 years.

I went through just a couple of hundreds of files from my recent inspections in search for some pictures and I'm overwhelmed by the number of mold-contaminated attics. I've never realized it but it seems like this area is completely off-limits for some homeowners. So, I decided to bring a little attic awareness into your daily routine and hope you'll appreciate it.

What Causes Attic Mold?

There are a few factors that have a major impact on making attic areas a "mold friendly" environment:

  • inadequate attic ventilation: #1 cause of mold growth in the attic!
  • bathroom/kitchen/dryer vents discharging into the attic
  • inadequate/missing attic floor insulation
  • improperly insulated cathedral ceilings and skylight chases
  • furnaces and water heaters installed in open attic
  • plumbing vents open into the attic—uninsulated air ducts
  • poorly insulated ceiling penetrations, attic access panels

Just the first two items combined together could transform your attic into the steamy, mold contaminated room during the cold season. Any warm air trapped under the roof will form condensation on framing, decking surfaces, and roofing nails creating mold nesting habitat. Some homes have more than one attic and an upper one, usually located above the bedrooms and bathrooms is always more susceptible of being contaminated because warm air from lower parts of the house will naturally raise up, transfer through the ceiling and all its penetrations into the attic.

Solutions to attic problems are very simple, and all you need is a knowledge of what is going on above the ceiling. Once everything is properly done, you won't have to worry about any mold growth under the roof, but I still highly recommend to monitor it periodically. So, let me walk you through your attic, stay close and watch your steps carefully - before you look for a potential problem in the attic, make sure that your feet have proper support.

First, we pick a cool day for this trip . . . access might be as easy as pulling down folding attic stairs, but sometimes it is a challenge as far as the size of an opening and its location.

If you don't feel comfortable with it, find somebody else to do it for you!

Typical hatch placement would be hallway or closet ceiling, but depending on house design, other areas are used as well, and sometimes it could be from the house exterior, garage . . . or there might not be access at all. In some attics, with a good flashlight, you might be able to spot most of the problems right from the entrance, without even crawling through the insulation. Shine your light beam above your head and onto the roof decking/framing surface, check carefully areas where the attic floor meets the roof, because that's where mold usually starts appearing (samples of what you might see are on the pictures). If there's no unusual discoloration, or if you can see clean wood surface with no residue on it, then everything might be OK and you can put a check mark by each of the items below.

How to Do It

First things first: All bathroom/kitchen/dryer vents HAVE to discharge to the house exterior and beyond the attic area.

  1. Access panel, pull down stairs should be insulated to minimize air transfer between the living area and the attic
  2. If you're looking at the attic section located directly above the bathroom and / or kitchen with an exhaust fan discharging through the ceiling you should be able to see some kind of a pipe (galvanized steel, aluminum, plastic, sometimes insulated - recommended) between the attic floor and the roof decking. If there is no pipe, and you can't see the fan itself, turn it on and try to locate it by following the sound, because it might be just hidden under the layer of insulation. There's a chance, that discharge pipes from those vents have been dropped into the soffit, or to the vent ports installed in the soffit - personally, I don't recommend such installation and for one very simple reason—warm air rises up, and during the cold season it will return back to the attic (some jurisdictions recommend or permit such installation). So, if there's no pipe attached to the vent, or one discharging through the soffit appears to be causing problems (stains / discoloration above the soffit area where the pipe enters), get it through the roof using a dedicated port or at least install it close to the attic vent (just make sure that vent screen is clean). Kitchen vents should have dedicated ports (do not use attic vent ports), and smooth interior, metal pipes should be used for discharge, not plastic or aluminum flexible hoses.
  3. A dryer vent discharging into the attic is a huge source of moisture and heat, and requires its own dedicated port (just like the kitchen vent). Again, smooth interior wall, metal pipe should be used (no plastic permitted). Dryer vents require periodical cleaning to remove accumulated lint from interior walls—when it becomes clogged, you're just wasting precious energy—if it goes through the roof, it would probably be easier to separate the discharge pipe in the attic area (at roof vent connection) and clean pipe and roof vent screen from there. Clogged dryer vent pipes overheat and if pipe connections have been sealed/secured with duct tape, they might eventually separate. Using screws on connections causes more lint to be trapped inside, so plastic ties and duct tape + maintenance might be the best choice.
  4. Any missing insulation on skylight chases, walls/ceiling between the attic and living quarters should be installed - with blanket type insulation always put moisture barrier facing towards the heated area (never leave flammable paper exposed). There might be an open chase/empty wall space between the basement/crawlspace and attic area—seal it, from both sides if possible.
  5. Cathedral ceilings insulation has to be installed with a proper clearance to decking surface, otherwise, it promotes mold growth.
  6. Plumbing vents left open in the attic area, have to extend through the roof.
  7. Furnaces and water heaters installed in attic area should be contained inside a separate room - code requirement in some jurisdictions, any vent pipes from those appliances must be double wall if penetrating attic area.
  8. Heating ducts should be properly insulated
  9. Because you need to have an attic as cold as possible, and especially during the cold season, but, I'll tell you a little secret, sometimes with all those things I've listed above being the wrong way, and without any ventilation, there will be no mold at all.

Attic Mold Photos

Click thumbnail to view full-size
Attic moldAttic mold imageBlack mold and frost on roof decking and roofing nails caused by inadequate ventilationDisconnected dryer vent in the attic area discharging warm / humid airBathroom vent discharging into the soffit, and causing mold growthBathroom vent missing discharge pipe in the attic - should be always discharging to the exterior
Attic mold
Attic mold
Attic mold image
Attic mold image
Black mold and frost on roof decking and roofing nails caused by inadequate ventilation
Black mold and frost on roof decking and roofing nails caused by inadequate ventilation
Disconnected dryer vent in the attic area discharging warm / humid air
Disconnected dryer vent in the attic area discharging warm / humid air
Bathroom vent discharging into the soffit, and causing mold growth
Bathroom vent discharging into the soffit, and causing mold growth
Bathroom vent missing discharge pipe in the attic - should be always discharging to the exterior
Bathroom vent missing discharge pipe in the attic - should be always discharging to the exterior

Questions & Answers


      0 of 8192 characters used
      Post Comment
      • profile image


        3 years ago


        I live in Florida and the temperature in the garage from late May-October is brutally HOT. Hour AC handler is in the garage and sweats a lot. The attic space just over the garage is not insulated. My AC company told me if I insulate the attic it will make the handler sweating greater because the heat of the garage enables the moisture to dry out a bit. Does this make sense? Do you suggest to insulate (batt) or not insulate the attic above the garage? Thanks.

      • profile image


        3 years ago

        I have a weatherization team that is working on my house and they put in an exhaust fan or vent in my bathroom as it gets mold on ceilings and walls from lack of it. I asked if they were putting in a vent to the outside. I was told no it didn't need this as they were making it a 'cold attic' and they don't get mold. I still feel uneasy about this. Is it true? Thanks for input

      • profile image

        Nora Moore 

        5 years ago

        That's a good idea to check if the bathroom and dryer vents discharge outside the attic space. If they don't, the moisture could build up in the attic and that's when you get mold problems. I'll have to go look for the vents sometime soon. Those pictures of mold just give me the shivers.

      • Home Maintenance profile imageAUTHOR

        Home Maintenance 

        5 years ago from Illinois, USA

        Hi Cindy,

        For as long as the conditions supporting its growth have been eliminated it will remain in what you could call a "dormant" state. Ideally it should be removed from the surface completely.

        If it's a small area I would take that extra effort and remove it completely. You can also wait till it gets very cold and evaluate the area, see if the surface becomes moist and contamination area starts expanding (surround the contaminated area with a marker so you know if it's growing).

      • profile image


        5 years ago

        Thank you fro your posting! I went through the check list and I am NOW in compliance...replaced plywood and shingles on roof. ridge vent with high air-flow baffle style. Opened up soffits that were clogged by insulation and put in 2nd floor ceiling vent in bathroom (outside vented). Ventilation problem has been solved. there is small amount of mold remaining on support boards. will mold die now?

      • Home Maintenance profile imageAUTHOR

        Home Maintenance 

        6 years ago from Illinois, USA

        Hi Sherry,

        Low temperature in your attic during the cold season is a very good sign, however, the question is: is it as cold as on the other side of the roof surface and is there any air circulation?

        There is a possibility that the roof vents became contaminated with dust, bird nests, or simply got covered with accumulating snow for some extended period of time. If there are any soffit vents, they could become contaminated over the years as well (dust, insulation, paint, etc.) All of the above could cause temperature rise within the attic and result in condensation buildup on the surface of roof decking boards / plywood.

        Moisture, lack of air circulation, and lack of light are some of the main ingredients responsible for mold growth in attics. Insulating attic access doors and checking ventilation / vent screens for contamination would be the first thing to do.

        Mold contamination in on area of the roof decking surface could also indicate failing roof, roof flashing, or / and vents flashing issues. It's difficult to say without examining this affected area.

        Please let me know if you have more questions or check some of my posts in "Attic" category on my website -

      • profile image


        6 years ago

        We have these bedrooms upstairs in our cape cod style home and each bedroom has a little 4 foot door that leads into what you could call an attic or storage area. We just noticed this year after being here four years with no problem that there is some black mold on the roof part of that room. What could be the reason after all this time with no issues? When its cold out its freezing in there and when its hot out its smoldering in there. Now the doors to these areas also have no insulation. Any advice would be appreciated.

      • profile image


        8 years ago

        new roof being installed barrier material now installed it is and will continue to rain this week if the shingles are installed an wet surface will there be a potential mold problem between the barrier and the shingle

      • profile image

        Angel Grace 

        8 years ago

        Does Mold continue to grow once the ventilation problem is corrected and the other bad wood is removed?

      • profile image

        Cira and Associates Consulting LLC 

        8 years ago

        Cira and Associates Consulting LLC can help maintain or re-establish a normal fungal ecology or reduce other contaminants that can adversely affect the living conditions and air quality in your home.

      • profile image

        paranoid mold freak :) 

        10 years ago

        Is the black in the picture with the pink insulation all mold? We have an attic that we are fixing the ventilation problems - the south (sunny) side walls are normal looking wood; the north and shadier side had black wood, like the picture above from 2/8/07. Could all that black be black mold?

      • Home Maintenance profile imageAUTHOR

        Home Maintenance 

        11 years ago from Illinois, USA

        You're welcome, let me know if you ever have any questions concerning your home,


      • profile image

        Rob from Seattle  

        11 years ago

        Good info. Thanks for posting.


      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

      Show Details
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
      ClickscoThis is a data management platform studying reader behavior (Privacy Policy)