Cathedral Ceilings – Mold and Moisture – Problems and Solutions


Rotten roof deck

Disclaimer: while I think all the information presented here is accurate and scientifically valid, you are advised to consult a *professional before changing your home. This article covers just one component of your home. Your specific home may have conditions that override the comments contained herein.

*By professional, I mean an experienced building scientist, not your local carpenter or roofer or even a structural engineer or architect. While many of these people are artists in what they do, most have no training in building science or engineering and cannot be trusted to properly design a roof assembly. Likewise, you wouldn’t hire a building scientist to swing a hammer and build your roof!
Cathedral ceilings are very popular – they give rooms a feeling of openness and an added aesthetic dimension. At the same time, they are responsible for a variety of building problems and homeowner heartbreak. What causes these problems and how do you avoid them?

There are a variety of climate zones. The south-eastern United States is hot and humid, while the north east is cold. The mid-Atlantic states, where I live, is mixed – during the summer it is hot and humid, during the winter it is cold. The south west is mostly hot and dry and the northwest is moderate in temperature but very humid! Each of these climate zones has its own particular building details. However, all must follow the laws of physics.

Physics tells us that moisture moves from areas of high humidity to areas of low humidity. If it’s more humid outside, moisture wants to come in. And when it’s more humid inside, the moisture will move toward the outside. Simple!

The trick is, the amount of moisture that air can hold depends on the temperature of the air. Warm air holds more moisture than cold air. And, at some temperature, the air reaches a point where it can’t hold more moisture. This temperature is called the dew point.

The next thing to know is that moisture in air is water vapor. Water vapor is much smaller than liquid water, so vapor moves through building materials much more easily than liquid. Water vapor is also lighter than air, so it rises up to the ceiling and through any cracks or holes. Warm air also rises, so there is a tendency for warm, humid air to exert lots of pressure on the ceiling. These concepts are also pretty simple. Just remember – humid air and warm air rise.

So what happens during the winter when you heat your house? The warm air in the house contains lots of water vapor. That warm air and water vapor rises up to the ceiling. If there are holes, like electrical boxes, recessed lights or ceiling fans, the vapor easily moves up into the space above the ceiling. What looks like a little hole to you looks like an open window to the tiny water vapor molecules.

Let’s look at a diagram of a typical cathedral ceiling during the winter….

Typical fiberglass insulated ceiling

The blue lines represent moisture trying to move from the inside of the house, where the air is warm, to the outside, where the air is cold and dry.

For most of the ceiling, the moisture encounters painted sheet rock, which stops air flow and most of the water vapor. However, a small amount of the vapor travels through the sheet rock slowly (thin blue lines). Where there are any holes, such as at recessed lights, air moves through the holes, carrying water vapor right up into the insulation. In fact, a small hole can transmit tens or hundreds of times more water into the ceiling cavity than moves through the the painted sheet rock.

As the water vapor moves through the insulation towards the cold roof and outside air, it encounters colder and colder temperatures. If the temperature reaches the dew-point, the water vapor condenses  into liquid water and can drip back down through the insulation and back onto the ceiling, causing water damage. Some people have experienced it literally raining in their living room when this happens!

In order to combat this effect, builders created the vented ceiling. This is a space between the insulation and the roof deck. At the bottom, there would be a soffit vent and at the top, a ridge vent. Such a construction allows airflow through the cavity. This airflow is supposed to carry away moisture that builds up inside the cavity. It is also intended to keep the roof deck cold to avoid snow melt and ice dams

Problems with the conventional vented roof

Problem 1: Moisture Buildup Within the Insulation

Thermal image showing air leaks

In moderate and sunny climates the roof may heat up during the day, warming it enough to carry away the water vapor and dry out the insulation. However, what if the roof doesn’t get much sun or the moisture moves through holes in the ceiling faster than it can get carried away?

The moisture in the ceiling cavity can accumulate until it leads to ceiling damage. This is prevalent when the ceiling has many recessed lights or, uses tongue and groove boards instead of sheet rock.

The thermal image shown here demonstrates just how leaky a tongue and groove ceiling is. The dark areas show places in the ceiling that are colder than the surrounding areas. The lightest areas are where the insulation is intact and the ceiling is warm.

Problem 2: Moisture Buildup on the Back of the Roof Deck

If the moisture makes it through the insulation without condensing, it tries to move up and out of the cavity. However, this space is like a refrigerator. As the air moves through, it gets colder. Eventually, it may form ice on the back of the cold roof deck. I’ve seen many roofs rotten and covered with mold because of this.

The next photo shows an example of this problem. The home owner was replacing a recessed light when the electrician found mold. After deciding to tear off all the ceiling sheetrock, they found that almost all of the plywood roof sheathing was moldy. It should be noted that this roof was built strictly to code….using fiberglass insulation and ridge/soffit vents and a gap above the fiberglass to allow air flow.

Moldy roof deck

Problem 3: Improper Venting

Almost every roof put on these days includes a ridge vent, even if  it is not necessary. This is done because roofing manufacturers have stated that they will not honor the warranty if the roof isn’t properly vented. Unfortunately, putting a ridge vent on an old house often creates these types of problems!

Older homes used gable vents, not ridge vents. Most older home do not have soffit vents. What do you suppose happens if a ridge vent is installed on roof that has no place for air to come from?

The ridge vent still pulls air out of the attic or, in the case of a cathedral ceiling, out of ceiling cavity. That air has to come from somewhere, and that somewhere is the house. Many of the problems I have seen are caused by the ridge vent.

Building rule #1: if it ain’t broke, don’t fix it!

Building rule #2: understand what you’re trying to accomplish before doing it.
I have no problem with ridge vents IF they’re implemented along with a proper amount of soffit vents. I have huge problems with ridge vents when installed without soffit vents. I also have a problem with improper use of ridge vents where they are inappropriate.

For my own projects, I use Cor-A-Vent. They make excellent products backed up by proper engineering and supported by excellent technical documentation. If you plan on doing any roof work, I strongly recommend visiting their site and reviewing their technical literature. If you only read one document, make it this one. I’ve also copied this document so that it is available below.

Solutions

Now that you understand how and why things go wrong with cathedral ceilings (and roofs in general), let’s look at how to do them right. First, we need to know exactly what problem we’re trying to solve (building rule #2).

Refer back to the first diagram to the left – what problems exist?

  1. Warm, moist air enters ceiling cavity through holes and cracks
  2. Small amounts of moisture moves through the sheet rock
  3. Air and moisture easily move through fiberglass insulation
  4. Moist air temperature drops below the dew point
  5. Intentional airflow from ridge vent draws moisture/humidity from the house

Solution 1 – don’t put holes in your ceiling

This is obvious, so why do people insist on poking so many holes in a perfectly good ceiling?

Typical recessed light fixture

The biggest offender is the recessed light fixture. Most of these fixtures, even those rated for insulation contact, are worthless in cathedral ceilings. You may as well just drill holes in your ceiling to let the heat and moisture out.

If you absolutely must install recessed lights, buy boxed fixtures rated ICAT – Insulation Contact Air Tight. Be warned that all ICAT fixture’s are not created equal. For example, The fixture to the right is rated ICAT, but I don’t recommend this style. Much better are the fully sealed box fixtures, like the next photo.

Boxed ICAT fixture

Next, be sure to seal the fixture to the sheet rock so that it is air tight. A continuous bead of high temperature caulk greatly reduces the air lost by mounting recessed lights.

Recessed light fixtures may be the most common hole in your ceiling, but there are others that cause similar problems.

Be careful of electrical boxes mounted in the ceiling. These are usually very leaky, and can lead to even greater problems than recessed lights. These can be found above ceiling fans, smoke detectors or ceiling mounted lights.

Most of these are sealed with caulk or foam. Note that you need to do this carefully so as not to interfere with the electrical wires and/or contacts in the box. Best, have a licensed weatherization contractor deal with it.

Solution 2 – Use Insulation that Stops Air Movement

Fiberglass is a cheap insulation product, but it is not a good one in all situations. It works by reducing conductive heat transfer, but it does almost nothing to slow air movement. It doesn’t matter whether you put three inches or three feet of fiberglass insulation in the cavity, it’s not going to stop air movement and the associated moisture movement.

Unfortunately, most contractors love fiberglass. Anyone can install it and it is cheap. Granted, almost everybody installs it incorrectly – they compress it (reducing the R-value) and they install it in areas with air movement, rendering it almost useless.

If you absolutely, positively must use fiberglass, then do it right. Install it flush to the sheet rock so no air can come between the fiberglass and the ceiling. Do not compress it – if wires must be routed, split the fiberglass so the wire runs through the middle. If it has to go around obstructions, don’t compress it – cut it to the exact size and shape needed. And finally, make sure everything is sealed air tight so no air is tempted to flow through the fiberglass.

A much, much better solution is to use dense packed cellulose insulation. This is cellulose insulation that is installed to approximately 3.5 lbs./cubic foot density. At this density, cellulose does not allow air movement under normal conditions. The way it is blown in also forces it into all the nooks and crannies – around wires and pipes and fixtures. It also can be used in a “hot roof” design. With this installation, soffit and ridge vents are not used. The entire cavity is filled with cellulose. For details, see this link. A PDF of the Applegate Insulation technical bulletin is also available below.

What about moisture? Cellulose insulation can hold a tremendous amount of water, dispersing it throughout the material. In this way, like a sponge, any small amount of moisture that gets into the cellulose spreads out rather than puddling up. In a properly made roof assembly, this moisture then moves towards the shingles and out. Note – there is some controversy about using dense packed cellulose in ceiling cavities. Read this building science article by Joe Lstiburek. The problem arises when you have very porous ceilings, like the tongue and groove ceilings. Because so much moisture passes into the ceiling cavity, it can overcome the moisture flushing capacity of the insulation and roof. This is especially problematic if you have a completely vapor impermeable roof, like a metal roof or a roof covered with a rubber membrane (like all flat roofs). To avoid problems, listen to Joe and don’t dense pack your cathedral ceiling if you have any doubts.

Even better than cellulose insulation is high density sprayed polyurethane foam. This foam creates an air-impervious barrier and is also very effective at slowing vapor movement when applied at adequate thicknesses (greater than about 2 inches). Because of these properties, foam is usually applied using the hot roof (no venting) method. Note that the amount of insulation needed depends upon your climate zone. Colder climates need more insulation.

Polyurethane foam also has an excellent R-value, about twice that of fiberglass or cellulose.

Solution 3: Understand the Physics

Usually, when I explain the unvented roof to people, they ask “where does all the moisture that gets in there go?” To this I reply – where does all the moisture in your house go? Are your walls rotting out? Has your floor collapsed recently? Is there mold growing anywhere? Mostly, they say “no – but that’s not the same.

In fact, it is exactly the same! The reason that your house doesn’t rot or have mold growing everywhere is because the humidity of the air isn’t high enough to cause condensation on normal surfaces. In the same way, when you apply foam, the air cannot come in contact with a surface cold enough for condensation to occur (unless you keep your house like a greenhouse!) The humidity within the ceiling cavity is the same as it is inside the house so you have no problems.

Except for one….

There is an unfortunate technique called “flash and batt” that has become popular among builders because it allows them to air seal using spray foam but keep the cost down by providing the majority of the R-value with cheap fiberglass. Unfortunately, many of these insulation contractors do not understand physics. In the cathedral ceiling example, they spray a thin layer of foam to the bottom of the roof deck, air sealing the cavity from the top. Then, they fill the cavity with fiberglass.

What’s wrong with this picture? The fiberglass allows the warm air from the house to move into the cavity, through the fiberglass. But, the air cools as it gets close to the thin layer of foam on the roof deck. If the foam is not thick enough (usually the case), then it will be very cold. Now, the moisture in the air condenses on the inner surface of the spray foam. Even worse, the air and moisture sealing properties of the foam then locks this liquid water into the ceiling cavity. Before you know it – rotten ceiling or rotten roof.

Now, you can do flash-and-batt in a way that it works, more or less. Remember the physics – we want to stop the air and moisture movement and prevent the water vapor from coming in contact with cold surfaces. To do this, you build your ceiling, install wires and fixtures and then spray the back side of the ceiling with foam. This seals everything and keeps the moisture in the house. The problem is, this means putting the roof on last! This is never done because you need the roof on as soon as possible to keep the weather out while you’re building the house.

So, if anybody says you can save a lot of money by doing flash-and-batt for your ceiling, send them packing – they don’t understand the physics of insulation and you’ll probably end up having to buy a new roof in a few years because your builder cheaped out on insulation.

Side note: Walls

Think about walls. They don’t require ventilation. They’re supposed to be sealed tight, and they don’t rot out (except when they leak, but that’s another story.) Why do we build ceilings differently than walls? Well, there is a slight difference – remember that warm, moist air rises. So ceilings are more likely to have warm, high humidity conditions than walls. However, the same physics applies.

As noted above, flash-and-batt is becoming more popular, but the same rules that apply to its installation in ceilings applies to it in walls – the foam must be sprayed against the backside of the sheet rock on the wall. It must not be applied to the outer wall sheathing with fiberglass on the inside. This is almost certain to lead to rotten, moldy walls. But, if you don’t do it the cheap way, then just spray the foam against the sheathing, but use enough of it so that the inner surface never gets cold.

Final Comments – Understanding R-Value

If you’re interested in more physics, see my notes on insulation and heat transfer.

Related articles and discussions

Caveat – if you read through discussion groups on this topic, you will find a lot of bad information. Information from builders, architects, engineers. I’ve sorted through the garbage and only included links to sources that appear correct. If you need to, go back and read “solution 3” above. The physics are simple. But the details can be complicated since the exact roof structures vary considerably and the devil’s in the details!

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22 thoughts on “Cathedral Ceilings – Mold and Moisture – Problems and Solutions

  1. I am having a home built in Oklahoma with a cathedral ceiling living room and concerned about moisture problems. If I use open cell spray foam, should it be applied to the roof rafters/sheathing cavity or behind the cathedral ceiling cavity?

  2. I am building a home with a cathedral ceiling in Oklahoma and I am concerned about moisture issues. Regarding your the last paragraph or two under “Solution 2 – Use Insulation that Stops Air Movement” you mention spray foam being a good solution. Are you talking about open or closed cell? Should it be installed on the back of the cathedral ceiling cavity? Or up on the roof rafters/sheathing? Thank you.

    • Closed-cell spray foam is best because it has a lower moisture permeability. You can spray it to the back of the ceilings drywall if the roof is open or the underside of the roof decking if you need to do it that way. Ideally you would spray it to the back of the ceiling drywall and then you would ventilate the rest of the cavity from the soffits up to the ridge vent. Since you’re building the home and have control over the process you may also want to consider using board foam on the inside of the rafters before you put up the sheetrock. This would greatly reduce thermal bridging from the rafters and then you could fill the cavities with either open or closed cell foam and ventilate under the roof decking to flush out any residual moisture. You could even use fiberglass because the moisture levels getting through the board foam will be so little.

  3. We have cathedral ceiling in several rooms. The house is in NC. This has been an exceptionally humid summer but it is the the first time since the house was built (1984) that a severe humidity issue has developed in one of the three rooms with a cathedral ceiling. It is so bad that the ceiling gets a layer of moisture on it if the ceiling fan is not run during the day. There are also four large windows starting at 7 feet up between the kitchen and sun room (interior windows) that steam up as well. The crawl space under this room is dry. The windows, are mostly the older style Pella windows (two single pane pieces of glass with a 2 inch space between them). Humidity in the house is high although the HVAC is working properly according to to two HVAC companies. I have put a vapor barrier between the attic and upper portion of the room to no avail. I’ve read that moisture migrates from hot to cold as well as rising since it is lighter than air and this is made worse since hot air rises. If the moisture was coming in through the windows we would expect the problem to show up in all rooms with cathedral ceilings. Not the case. It must have something to do with the ceiling since the crawlspace has been ruled out. A new roof was put on by the previous owned 2 years ago and shingles were laid over the opening for the ridge vent. I corrected this deficiency several weeks ago but the problem continues. I wonder if air flow from the soffits to the ridge vent is blocked and casing the problem, But again, it is not a problem in other sections of the house. I will add that we added three skylights to the roof but the condensation problem is on both side of the cathedral ceiling wnad the skylights are only on one side. All comments and suggestions are welcome.

    • Can you think of any other factors that might have changed? Since you have such a long, trouble-free history with the house, it would seem that something had to have changed to cause the current humidity issues.

      A few things that I can imagine:

    • Vent fan(s) clogged – this could be bath fans or range hoods. It’s fairly common for birds and squirrels or other animals to get into the duct and clog them with debris.
    • Dryer duct – when was the last time you cleaned the ductwork from your dryer to the outside? These fill with lint after a few years, leading to very inefficient dryer operation and excess household humidity levels
    • It’s possible that the ridge vent has something to do with it but I kind of doubt that it would cause these type of issues.

      If you can, check all your vents, listed above, and get back to me. We should be able to troubleshoot this together before your roof rots out.

      • Thank you for the response. I will get back to you after checking the dryer vent but that is on the other side of the house.

  4. I am at a loss as to what to do with my roof. I live in the Pacific Northwest in a Justus solid cedar home with a Monier shake style concrete roof that has been on about 20 years and is in good condition. However, about 3 years ago bats and possibly mice have managed to get in the tiny openings between tiles and perhaps under the sheathing. I had the side and ridges foam sealed by an exclusion company and this has helped reduce the animal problem, but some are still are entering at night. Since that sealing I have noticed an increase in loud cracking sounds during the day and night which are apparently from built up heat in the sealed unvented roof on hot days. All ceilings are cathedral style tongue and groove cedar covered by a membrane, 3″ rigid foam insulation, 1×4 battens to hold the foam in place, solid plywood sheathing and a waterproof membrane, followed by tile hanging on wood strips. All interior lights are surface mounted and none penetrate the ceilings. I can replace the roof with composition, thereby sealing the roof even more, but am concerned that this would allow even greater heat build up and rapid temperature fluctuations than the tile. Some roofers have suggested that we could put ridge vents in, but I have read on some building sites and on ASHRE that venting a sealed roof design in the Pacific Northwest can result in increased moisture in the roof and lead to mold. I had a conversation with a principal at a very large roofing consultant company and he felt that just adding ridge vents would allow the lighter hot air to escape above the foam and resolve the heat build up and noise problem. I would appreciate your opinion on whether this would be a reasonable approach.
    Thank you-

    • From a physics standpoint, the cracking is probably due to structural members expanding during the day and contracting at night, as it appears you understand from what you wrote. I am concerned that the sealing process changed the dynamics of the roof, since you had good luck with it in the past and only recently experienced the cracking sounds.

      I’m unclear as to where the pests have gotten into. Given the construction you lay out, there wouldn’t appear to be any place for them to go except under the tiles. Sorry if I’m not visualizing this right.

      I’m also unclear in your construction as to how the ridge vents would improve ventilation? Where would the air move from/between? Sorry again, I’m just having a hard time seeing the logic behind the suggestions you’ve been given. The only thing that I can imagine is that he’s thinking that air will move between the foam and the plywood sheathing above. That could make sense if there’s enough airspace and venting at the bottom to allow air to flow into the cavity. But just adding roof vents without allowing for air intake at the bottom will result in minimal/no air flow and would be a waste of time.

      I also agree that venting a sealed roof in a humid climate is opening it up for problems. I would advise against doing anything that changes the basic configuration that’s been working all these years. However, if it’s venting in the way I described above, the moisture would probably be flushed out as air flowed through and the roof goes through heating cycles during the day. But again, if you haven’t had moisture problems in the past, I’d be very cautious about changing it.

  5. Great information! How do I figure out the problem with why paint is peeling off the top of my cathedral ceiling. Before reading this page, I thought it was too much humidity/moisture in the house, especially as a result of a broken oven hood that does not suck out any moisture while cooking in the kitchen. Another issue I thought might affect it is the attic next to the cathedral ceiling is not ventilating probably because the vent fan is not working. Now, after reading this page, I think the problem might be improper airflow through the roof of the cathedral ceiling because there is no ridge vents. The house was built in 1978, location southeast Georgia.

    • Could be any of those things. Since moisture rises and tends to accumulate at the peak, I’m thinking maybe your theory about moisture in the house could be accurate. It could also be possible that when the ceiling was painted, it was moist towards the peak and that moisture caused poorer adhesion of the paint.

      If the moisture is coming from the space behind the sheetrock, then there’d be a pretty large amount of moisture up there which would probably be causing issues with your roof.

      It would be worth inspecting the areas where the paint peeling is worst. I’ve found that cutting a small hole in the sheetrock (that can be easily patched) can be very revealing. That would tell you if there’s moisture/mold in the cavity or if it’s just accumulating inside the living space so you can address the real issue. Often people spin their wheels for years, trying this and that without success.
      Good luck. Please let us know how you make out.

      • I am thinking of putting some wooden trim at the top of my cathedral in order to cover up where the paint is peeling. Carpenters who have come by to look at the issue say that they would have to nail the trim into the ceiling into the sheetrock (i.e. drywall) in order to hold the trim in place. Do you think this would allow moisture air to seep in from the house and into the space between the roof and sheet rock thus contributing to the problem? Or do you think that the nailing trim to the top of the cathedral ceiling will not cause any additional problems? Thanks!

      • If you add trim as an aesthetic addition, it will minimally affect moisture one way or the other. Nail through the material isn’t going to change anything either in any sort of substantive manner. Where it starts making a difference is if there are actual holes, like for an outlet or light fixture, where air can freely move between the interior and the wall/ceiling cavity.

  6. Hi T.D. . . I have a bit of an issue and this article seems to touch on exactly what I’m seeing. I have a cape style home that was built in 52′ w/ gable end vents and a walk up attic. At one point the walk up became living space with knee high walls and the ceiling sheetrocked right to the peak and around the collar ties.

    The problem is that it’s a hot roof, no ridge vent and no soffits, because of the warmer air on the inside of the house in the winter (North East) I am getting some condensation near the peak on the inside of the sheet rock. This also happens in the summer when there is an air conditioner on and the hot air rises and gets forced up. There is a brand new roof on the house as the old one needed to be replaced, There are no rafter mates in the space between the sheetrock and the roof sheathing and the space between the roof and the sheet rock is completely filled with fiberglass insulation. I have NO idea how to resolve this now !!!!

    I could cut in a ridge vent but there are no soffits, I could add a hicks vent at the bottom of the roof but the area inside is full with fiberglass. What can I do to fix this issue once and for all ?!?!? I’m really at a loss, any direction you could provide would be greatly appreciated.

    CP

    • It sounds like you have a high moisture level in the house. Even with an insulated cathedral ceiling, the sheet rock will be colder than you might expect. If you have more ventilation then the sheet rock will get even colder and the condensation problem will get even worse.
      Humid air rises, which is why you’re getting condensation at the peak.
      I suggest getting a humidity meter (you can get one that measures air relative humidity for maybe $30.) Measure the humidity low in the room then measure it up near the peak. During the winter/cooler weather, you should be reading 40% or so. I suspect you’re up closer to 55-60%+ when you see condensation. The question is why?
      It could be as simple as bathrooms not venting the moisture when you shower. Check the bath fans to ensure good flow and run them while showering and 20+ minutes after you shower.
      Think about your home – are there any other moisture sources? Lots of house plants? Dirt crawlspace or basement? Anything like that can cause moisture issues like you’re seeing.

      • Hi T.D. thanks so much for the quick reply. I’m at a loss . . . the house is in the north east (Massachusetts) and currently the house is completely unoccupied as I renovate it so there is no source of moisture right now. I’m really at my wits end about this problem. To make the problem even more curious is the temp difference from inside to outside is not even that significant. It’s been a little cooler here lately maybe 30’s-40’s outside and the inside temp is set to 52.
        I am thinking that my only alternative, because I just got the new roof installed, is that I may have to rip out all the sheet rock and insulation on the inside in order to install proper vents then cut in a ridge vent and add hicks vents at the bottom of the roof. I’m freaking out, I hope I don’t have to do this but I’m not sure what other alternatives I’ve got.
        I’m thinking about cutting a good sized hole in the ceiling upstairs to see what is going on inside the rafter cavity to see if there is any damage in there or signs of water inside the rafter area.

      • Condensation on the inside doesn’t come from the outside so you can rip it apart and ventilate all you want but the problem won’t go away.
        I still encourage measuring the relative humidity indoors. There has to be a source of moisture. Wet basement? Something is causing the problem.
        Is the house closed up? It could be like the dew forming on the car at night. If the house absorbs moisture during the day, it will hold that in the building material. With the house so cold, it won’t take much to get condensation problems. That’s why houses should be heated even if vacant. Otherwise, they get moldy. Try turning the heat up to at least 60. Also, you might want to air out the house when the humidity is low.
        I’d turn up the heat and run a commercial dehumidifier until the humidity drops to an acceptable level.

  7. Hi Ted. Depressed. I have a 1980 3000sq.ft. 4 level split home in the country in Manitoba Canada which has a cathedral/vaulted ceiling. As you know our Winter’s can be brutal. Building Plans came from California and it was constructed by a home builder as his own home around 1979. They only lived in the house abt 3 yrs. We have lived in it 25 yrs. to date.
    The roof deck from the outside does not have sheathing but wooden slats. We just had the roof re-shingled again abt 3 yrs. ago. Asphalt Shingles are tacked to the slats. About 70% of the roof is not accessible because of the vaulted ceiling. I cannot access built in electrical boxes or vent hoses from the bathrooms and kitchen stove because its just too narrow a space. The South view from the Great Room and kitchen is almost all glass the entire length of the home (abt 40ft). 4 large sections of glass, a couple which are sliding units.
    The only thing on the inside ceiling (tongue & grove cedar) of the Great Room is two lighted ceiling fans and one set of lights over the dining room table. I have a skylight at the top of the stairs abt 5ft above a defective ceiling fan. Water started coming through the highest ceiling electrical (fan) abt 6 yrs. ago. That ceiling fan has now seized up and stopped running. The electrical lights work but that fan doesn’t. I also have two hanging ceiling light fixtures in the kitchen. The higher one (same elevation as the defective fan) has had water dripping down the electric wire into the glass globe a few yrs. back. Luckily no water from there in the last couple of years.
    Soffit vents are on both sides of the home (South & North). I also have 3 roof vents. I had tried a whirly a few yrs. back at the recommendation of a local roofer but it didn’t help so we had it removed 3 yrs. ago. We have circular gable vents at the East and West ends of the house. The attic insulation is cellulose and a bit of fiberglass in cavities here and there. The last 4 yrs. we have now been getting water leaking from the top of the glass window unit frames on the inside at about the same track downwards as the defective fan. There has been enough water to fill half an ice cream pail some years. Towels get sopping wet.
    We also have a real wood burning fireplace in the Great Room which we crank up during winter months. We burn all the time except when sleeping. We manage to get the temp up in the Great Room to about +24 Celsius or 75 Farenheit or highier. We also heat with a new high efficiency natural gas furnace and radiant cable ceiling heat in our upstairs bedrooms. I have looked inside the attic in the small area that I can get into and have noticed some water stains here and there.
    Shoveling the snow from the roof stops the water entry a bit because the roof gets colder on the outside when the snow is off. Last Winter I went up the roof to shovel the snow off and there was ice in spots 6 inches thick under the snow in places at the edge of the roof. I have rubber membrane over the soffit area. I really would appreciate advice which would stop the entry of water dripping into our home. We are getting older and are thinking of downsizing but I worry on passing on this white elephant to someone else. Its a beautiful home and property other than this issue. I can send you pics if you so desire.
    Ron

  8. Hi I have read your article, I have a peeling ceiling in the bathroom and it is going black, I have no money to attain your solutions I was wondering if I stuck on styrofoam packing or sheets ,just to clean it up would it work and stay white or will the fungus spread.through them. I ws going to stick them on using a glue gun.
    Thanks
    Siobhán

    • Peeling paint and mold growth are signs of excess humidity. In a shower, it’s really tough to control without a good bath fan that vents up through the roof. So your most important thing is flushing out moisture or the problem is going to get worse and worse. Over time, this can lead to rotten timbers that are supporting your ceiling or the roof above, so it’s not something to mess with. You HAVE to deal with the moisture properly or you’re going to end up having to pay a lot more later.

      So, number 1, make sure you’ve got a good bath fan. This should run the entire time you’re in the shower/bath and for about 30 minutes after you’re done.

      In the meantime, you should clean the ceiling where it’s moldy. Wear a good respirator because you don’t want to breathe those mold spores as you’re cleaning. Warm soap water should do the trick since the soapy water dissolves the “glue” that binds mold together. Lots of people use bleach, but I’d start with soap water.

      Once you’ve cleaned it, and it’s dried out well, you can repaint it with some good paint intended for bathrooms. Hopefully, you have another shower you can use because you can’t shower until the paint has dried and set. And if the ceiling hasn’t dried out well, the paint won’t adhere and will just fall off.

      That’s your starting point. If you just foam up on the ceiling without dealing with the moisture, the moisture is going to go up there still and rot things out.

      Good luck!

      • It’s really difficult to retrofit an improperly done job. Often, the best thing to do is ensure that humid air cannot enter the ceiling cavity where the insulation lies. I’ve seen many homes that have survived decades with the cathedral ceilings packed with insulation because there was a thick interior ceiling layer of plaster without any holes in it. Unfortunately, more “modern” homes often have these ceilings filled with recessed lights that allow copious quantities of humidity to move into the ceiling cavity. During the winter, the water condenses in the insulation and rots out the roof sheathing. The retrofit for these is to remove the recessed lights and patch up the ceiling.

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