Help! The ceiling leaks but the roof doesn’t?


It was very cold, -20-30 C (or well below zero F) for a few weeks, but the deep freeze has ended, overnight it warmed up to well above freezing, everything is melting.  And there is this huge new water stain on the ceiling…  If this is your house, keep reading.

Here are some clues.  Your house has a humidifier and you use it, you do a lot of cooking, there are more than three people living in the house, you have a lot of house plants, someone, or maybe more than one someone, likes their long, hot, morning showers, and maybe forgets to use the bathroom fan, or maybe there is no bathroom fan.  Maybe you live in a older house with new insulation, or maybe your house has a cathedral ceiling.

Frost inside attic hatch


The picture above was taken on a very cold day notice the ice (frost) built up inside the attic hatch opening.

The next picture, from another house was taken a few days after a big melt. This was an older house with upgraded insulation stuffed into the eaves, blocking ventilation.  A brand new rotary ventilator was spinning merrily on top of two year old shingles.  Insulation and rafters were very wet, and there were indications of mold growth in the attic.  Water was leaking everywhere.



What is happening?
Air from inside the house leaked into the attic.  Warm inside air holds more moisture (humidity) than cold air. When the inside air enters the freezing attic the moisture condenses as thick frost. Because the frost does not evaporate readily, it builds up like the snow in your yard. The more inside air leaking into the attic, and the longer and greater the cold spell, the greater the build up of ice. If it warms up suddenly, the ice melts, there is too much water to evaporate, so it runs down, if it can collect somewhere, or it finds an opening, you have your leak, and a water stain.  Water may even run down the back (inside) of sloped roof sheathing and rafters and trickle into the walls.

If the air inside your house had been dryer, the moisture would have been absorbed by the dry air inside the attic before it could condense. If the attic was warmer it would also be drier because the air in your attic came from outdoors and able to hold more moisture, the leaked humid inside air might have dried or been absorbed  before there was enough of it to leak. If the ceiling and vapor barrier were intact the inside air would have stayed inside.

Your indoor humidity is too high if you can see this


If you have this problem, there are a number of things you can do to prevent it. The first thing is to reduce the humidity inside the house. In all the cases above, the humidity indoors was over 30%. Even though 30% is recommended for comfort and even more for fine wood furniture or hardwood floors, it is too high for very cold winters. If you can see condensation on your windows, your humidity is too high.

Use your exhaust fans, you should have a kitchen exhaust to outdoors if you do a lot of cooking, you should have a bathroom fan in every bathroom that is used for showering. If you have no fans, you should open a door or window (this may be tough – be strong :-)) If these methods do not get indoor humidity below 30% you may need a de-humidifier.

Eaves are blocked by insulation


Check the attic for adequate ventilation.   A well ventilated attic is a healthy attic.  If your house has upgraded insulation, it may not have been properly installed.  Air needs to be able to flow in from the eaves and out the ventilators on the roof.  Mixing static and rotary (turbine) ventilators is a bad idea, use one or the other.  A rotary ventilator can ‘short circuit’ attic ventilation by drawing air out of a nearby static ventilator instead of from the eaves.  Many pros only recommend static ventilators, rotary ventilators sometimes work too well, drawing air into the attic from inside the house.

A well ventilated attic is a dry attic


Check the ductwork inside the attic, in Canada the only duct work normally found in attics are exhaust ducts from the bath and kitchen fans. All ductwork in unheated attics should be insulated. Straight pipe is better than flex, and uninsulated white plastic dryer vent is not appropriate for bath exhausts. All exhausts must be vented outside through the roof, not inside the attic. Exhaust ducts should be as short as possible. It is not difficult to install a ‘gooseneck’ for an exhaust duct on a normal asphalt shingle roof, there is no need to run duct from one side of the attic to the other.

Air is leaking through the gap between the electrical octagon box and the drywall ceiling


You also need to prevent air from inside the house leaking inside your attic. The picture above shows a badly sealed light fixture in a cathedral ceiling, it has allowed air to leak into the attic space as well as  water back through the ceiling. Air may also be able to leak through the wire opening (knockouts) (circled). The area between the fixture box and ceiling should be caulked so that air cannot leak into the attic. A small amount of foam sealant at box openings will seal it. (Do not fill the box with foam, the electrical wires could overheat and cause a fire.). All openings in the ceiling between house and attic should be checked and sealed if necessary, including the exhaust fan openings.

New homes have a heavy (6 mil) plastic sheet vapor barrier between the unheated attic space and exterior walls. The sheets are taped where they are joined, and molded  plastic coverings for electrical fixtures are also taped into the vapor barrier. Older homes built between the 1960’s and 1990’s used lighter plastic (3 mil), lapped joints instead of taped joints, and no covers for the fixtures. Older yet homes may have lapped building paper under the plaster, or nothing at all. Whatever you may or may not have, it is not necessary to remove your ceilings and walls to upgrade your vapor barrier. Vapor barrier paint applied to exterior walls and ceilings will work just as well or better.

Cathedral ceilings can be a problem because they may not have any ventilation and their attic, if they have one, often cannot be accessed. If you have a cathedral ceiling it is particularly important that all ceiling penetrations are well sealed, and if necessary, a vapor barrier paint is applied.

And don’t forget to weatherstrip the attic hatch!

Thermal image of air leak at the attic hatch



Blown in fiberglass insulation

Most new houses in Edmonton insulate the attic with blown in fiberglass, a light fluffy insulation not too dissimilar from the poplar fluff that will blankets our streets and yards in early summer.  In some instances, when inspecting new homes I have found that the blown in fiberglass can be blown around inside the attic, creating insulation voids.

Wet spot on ceiling

The wet spot on this ceiling occurred the morning after a late night thunderstorm with high winds and blowing rain.

Insulation baffle is missing

The insulators forgot to install one of the cardboard baffles fitted between the trusses.  The baffle allows air to move from the eaves to the underside of the roof sheathing, essential for good attic and roof ventilation while holding the insulation in place.  The high winds blew the insulation off the soffits and also allowed water to enter the roof and collect on the ceiling where it leaked through the vapor barrier and created a wet spot on the ceiling.

Insulation voids on ceiling
Insulation voids on ceiling

In this new home the thermograph indicated there was little or no insulation in various spots on the ceiling. The inspection revealed that parts of the attic were bare, and insulation piled up in fiberglass drifts in other spots.

Insulation has been blown completely out of the truss space.
Insulation has been blown completely out of the truss space.

Talking to the builder revealed that the insulation had been installed before the soffits were covered, a wind storm had blown the insulation from one end of the roof to the other.

In the next picture, in this newly built home the roofers mistakenly installed an extra gooseneck ventilator for a bathroom exhaust.

An extra (unneeded) gooseneck is allowing the wind to blow the insulation underneath the opening.
An extra (unneeded) gooseneck is allowing the wind to blow the insulation underneath the opening.

There was no exhaust required here, so the gooseneck was left open, allowing the wind to blow into the attic, dispersing the insulation underneath it.  A truss had been uncovered, if left, the wind would eventually blow away all the insulation underneath the gooseneck, exposing the ceiling.

Out Dammed Ice!


As Winter retreats from Edmonton for a few months, it is an excellent time deal with any ice damming problem you might have had. Ice dams happen when uneven temperatures on the roof lets the snow melt on the upper part of the roof and  freezes again at a lower part. icedam3  When the weather warms, water pools behind the ice dam, unable to reach the eavestroughs.  Water that can’t run off the roof will run inside the roof, causing the damage to the roof sheathing in the attic you see here.damage1The white stains are mold growth. The culprit is also revealed, blown in insulation is preventing air flow and roof ventilation. damage2The black area was sopping wet. damage3
Someone added insulation to this attic without installing baffles or ensuring that there was good air flow. ATTIC EAVEAn insulated ceiling requires a well ventilated attic to ensure that the entire roof surface will be at the same temperature. The fix for this attic will require removing insulation from between the rafters and adding baffles, plus making sure the soffits are open so that air is free to circulate. roof-louvers800 If your roof had ice dams this winter, you should inspect your attic. You should be able to see the bottom of the sheathing all the way to the eaves, or you should be able to see baffles, and ideally some daylight at the eaves, indicating that your soffits are open. You should not see stained sheathing, moisture, rusted roofing nails points underneath the sheathing, or suspicious deposits. Inspecting your attic does not appeal? Call East Side Home Inspection 780 477 2666 and we will do it for you.