Last week we used this coldest part of the year to check for indoor condensation. This week I want you to stick your head up in the attic for an inspection that can only be done well this time of year, the attic frost inspection. We can have moisture problems all year long in an attic, but they will be their worst on the coldest day of the year, and this is the time of year when they are visible.
When it is really cold outdoors, the hot air in the house creates more pressure on the top of the house to escape, and it takes with it more moisture from the house. If this moisture manages to find a leakage path into the attic, it will rarely get out of the attic with the ventilation because it will freeze to the first freezing cold surface it comes to. This starts with just a little moisture on the roofing nail points sticking through the roof deck. It can also form large piles of what look almost like snow on top of the insulation right above any air leaks. The function of attic ventilation in the winter time is actually to keep the snow frozen on the roof, not to take away moisture, because this moisture is all white and frozen. Check out the Search tab above for more information on "Attic - Frost".
Control of frost, in fact all moisture in the attic, is primarily a question of sealing off all air leaks from the warm humid house below. If you find a mild even frosting on the underside of the deck, that is rather normal in an older house and is nothing to worry about. In many houses in January the frost will show up in clumps, usually located right above the source of the air leak. These concentrations of ice, either under the roof or on and in the insulation can cause water damage. What is convenient about these clumps is that they identify the source of the problem, which makes it easier for you to seal off the problem. Check the Search tab above for more details on "Air Sealing - Attics".
If you have lots of window condensation and you have a humidifier of some kind, you should simply turn off that humidifier. You have too much humidity in the house already. If you have a dry house, that is a sign that too much winter air is blowing through your house drying it out and the best solution is to air seal the house. Humidifiers should only be used to add moisture to the air when you have properly air sealed your house and still find that it is too dry for you. Most modern houses simply don't need a humidifier since we now thoroughly seal up our houses. In fact we have always tended to generate a lot of humidity in the house and a modern house which keeps this in needs mechanical ventilation to reduce the humidity rather than humidifiers to increase it. Check the Search tab above for more information on household "Humidity".
If you have a functioning humidifier it is time to check it to see if it needs cleaning and if it has any oil cups, time to oil it. If it is a very old drum type humidifier you may be interested in checking out the many new and much improved humidifiers that are now commonly available. Most of these will have control mechanisms designed to wet the air pad with little or no standing water. Vaporiser type humidifiers have the drawback that the minerals in the water will blow into the house rather than stick to the pad. I would rather have clogged up pads to clean, than white dust all over the furniture.