As noted in the previous entry, water is a mean b****.
It used to be that water could get in either up or down– from a leaky roof, or by wicking up from the ground. Then we got clever with our buildings and invited it inside from all directions.
Mistake #1: Windows
As Mel Gibson noted, in some countries like Scotland it’s an extraordinary thing when the rain actually falls straight down. When wind and rain combine, sometimes an eave or a gutter just isn’t enough to keep water off the sides of a building.
The example below is called a blackhouse from the west of Ireland, where the soil is poor and they are regularly lashed by vicious storms off the Atlantic. These buildings are extraordinary because they simultaneously solve both problems. The deep thatch roofs and solid walls make the interiors very dark but also very dry in all weather. The soot from fires has nowhere to go, so it wafts up into the roof material. By the time the thatch needs replacing it is heavily impregnated with rich carbon and organic material which, when spread on cropfields, improves the soil.
That’s all grand if you don’t mind dying of lung cancer and/or lose your eyesight by age 25. People invented windows for light and ventilation, but in the process created flat surfaces for water to collect.
This image shows rot damage in a window frame- count how many flat surfaces there are for water to collect. By my count it’s at least three: muntins, sash, and frame. In sash windows, the muntins (which separate the glass panes) are usually horizontal and vertical so they are even more vulnerable than the fan muntins in this lunette window. When water collects, it causes wood rot or pitting depending on the material of the window. Rot and pitting both eventually lead to failure and then water gets into the house.
The solution? Good caulk and good paint. Living houses are all about maintenance, so if you keep your windows caulked and their surfaces painted with a good, water-resistant but breathable paint (i.e. oil-based paint) they will last forever. FYI, vinyl windows are generally rated for 10-20 years. Cost of window replacement vs. cost of a can of paint- your call.
Mistake #2: Climate Control
Again with the humans being clever. In an effort to not freeze our buns off, we invented fire and then decided it would be smart to bring that fire inside our shelter. With fire comes smoke and unless you’d like to die of smoke inhalation, you ventilate. Interestingly, some historians have theorized that major technological advances (i.e. the Renaissance and the Industrial Revolution) have come on the heels of advancements in chimney technology- ipso facto, we’re a whole lot smarter when we don’t have brain damage from carbon monoxide poisoning.
This brings water into the house in two ways- obviously rain can come in through the chimney, but this is easily solved by a lantern cap or chimney pot such as these gorgeous examples at Hampton Court Palace.
The other way that heat (or cooling, for that matter) brings water into a house is through condensation.
Outside, hot humid air rising from the earth cools as it enters the upper atmosphere to form clouds of condensed water vapor. At higher temperatures water is a gas, as it cools it becomes a liquid.
This happens indoors as well- shown to dramatic effect here by artist Berndnaut Smilde.
As we create artificial atmospheres indoors, the water in the air gets caught between the temperature extremes. Think of those cold nights as a kid when you wrote your name in the frost on the window or those backseat hookups that steamed up the car windows (oh my my).
The warm air inside meets the cold air outside on a window surface, in a wall pocket, in an attic, a crawlspace, or anywhere else and condenses to make water droplets that then ruin your walls and cause mold growth.
That’s not pretty.
The worst part is, you can’t always see this kind of condensation- particularly when it’s in wall pockets or hidden by insulation. Insidious!!
How to avoid condensation? Good air circulation. Keep air moving inside with windows, fans, or your HVAC system and you should be fine. Sometimes a dehumidifier machine can also be handy in places where circulation is difficult, such as basements. If air is moving, it resists condensation- physics again. Circulation increases heat loss by convection and also prevents “zones” of hot or cold air from forming.
Also, if you have an HVAC system be very very careful about the collection pans. Most people forget collection pans exist and then they overflow and gee, you’ve got a lake in your living room. Air conditioning works by blowing hot air over a cold coil, which causes the water vapor in the hot air to (you guessed it) condense into liquid water. Air conditioning systems have drain lines installed, but if the line gets clogged or its absurdly hot out sometimes the water can build up. If your HVAC systems equipment is in your attic, make sure to keep an eye on that drain pan.
So now you know how the b**** gets in. How to make her leave? Again, good circulation. Don’t panic if the roof leaks or water comes in a window. Fix it, dry it, good as new. As long as the moisture is cleared out quickly, there should be no lasting damage to the building. It’s only when water has taken up residence that you have major problems. But, if you never let water in the house in the first place that is just so much better.