How to Prevent Attic Mold From Growing (If It's Not Too Late Already)
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.
- Access panel, pull down stairs should be insulated to minimize air transfer between the living area and the attic
- 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.
- 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.
- 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.
- Cathedral ceilings insulation has to be installed with a proper clearance to decking surface, otherwise, it promotes mold growth.
- Plumbing vents left open in the attic area, have to extend through the roof.
- 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.
- Heating ducts should be properly insulated
- 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.