In planning the location of intake and exhaust vents two other factors must be considered.
Intake and exhaust vents must be positioned so they assure continuous airflow along the underside of the roof sheating. As I spoke about in the introduction this is where ventilation is most effective. During the summer months airflow along the sheathing removes heat before it can radiate to the attic floor. During the winter months airflow along the sheathing removes moisture before it can condense into water droplets or frost. Intake vents must be located so there is little possibility of (0 comments)
Thermal effect by it self cannot create the high volume of air movement needed for effective ventilation. That is why the influence of wind is the key element in the design of a non-powered ventilation system.
Wind is a natural flow of air. So when designing a ventilation system you want to make the wind work to your advantage.
To use the power of wind you have to understand how wind force affects ventilation. It is not the velocity of the wind by itself that causes air to move through an attic.
Ever wonder how ventilation works? The word ventilate comes from the Latin word for “to fan”, the action of causing air to move. This is how ventilation works. It provides the conditions that allow air to move.
Effective ventilation requires a very specific type of air movement. We are not interested in moving air just to create a breeze that cools us by speeding evaporation.
Instead we want ventilation that provides year around benefits. If you have ever walked into the stuffy confines of a room that has been completely closed for a lengthy period of time, you (0 comments)
In this blog I will continue talking about dealing with the effects of ice dams. The greatest damage occurs when the water pooling inside the dam begins to infiltrate under the shingles.
The shingles themselves are damaged if not destroyed. Far more serious is the damage caused at the plateline area. Insulation can be soaked reducing its effectiveness.
Water also can infiltrate into both exterior and interior wall cavities leading to structural damage and the deterioration of painted surfaces. At the very least mold and (20 comments)
This section I will be talking about dealing with the effects of ice dams.
Winter creates a special attic ventilation problem where snowfall and cold temperatures are common occurrences. The problem begins with the formation of ice dams or barriers formed of ice, that prevent water from running off the roof.
Ice dams can form when the following conditions exist:
-Warm air accumulates near the peak of an attic. This condition is much more common than people think. It occurs because most attics experience some heat loss from attic insulation.
When it comes to moisture in the attic (this blog is continued from part 3) even vapor barriers for all their effectiveness cannot totally stop this process.
Another way moisture travels into an attic is by air moving through openings cut into a vapor barrier. These openings are commonly found at recessed ceiling boxes and attic entries.
The problems start when moist air hits cooler rafters, (1 comments)
When winter arrives and temperatures plunge you might think the movement of heated air would no longer cause problems in attics. This is not true! With seasonal changes the conditions just reverse.
Heat does not travel from an attic into the home. Instead heated indoor air travels from the home into the attic area. Moisture also travels into the attic during the winter months.
Furnace warmed air circulates through the house picking up water vapor generated by activities like cooking, showers, (0 comments)
Homeowners take action to cool themselves during the warm summer months. To reduce the effect of heat they will turn on fans, window air conditioners or central air conditioning systems.
As the hot weather continues these appliances run longer and longer. Heat also is being stored in the attic.
A less obvious but equally consequence can be found on the roof itself. Homeowners can’t see it happening but over time excess attic heat can cause some shingles (1 comments)
Every wonder what is the purpose of attic ventilation? This seems like a simple question. Most homeowners and even some experienced contractors believe the purpose of attic ventilation is to remove heat that builds up in the summer.
Well I would say that is accurate but what that answers leaves out is just as important as what it includes. If you understand the principles of attic ventilation you know an effective system provides year round benefits.
To start during warmer months the ventilation helps keep attics cool. With colder months ventilation (0 comments)