Attic Ventilation and Insulation (part 1)

What is the impor­tance of proper attic ven­ti­la­tion and insu­lat­ing and how does it affect the rest of the household?

What is Air seal­ing and how is it dif­fer­ent from insulation?

Is ven­ti­la­tion of the attic really that important?

Other than hold­ing the heat in the house, what does the insu­la­tion in your attic do?

These ques­tions are never asked enough and the answers to them are often over­looked. Most peo­ple know that the insu­la­tion in the attic space keeps the heat in the house and it is nec­es­sary, but often enough the insu­la­tion is not installed prop­erly, espe­cially on older homes. Air seal­ing is another con­cern that is often overlooked.

Improper attic ven­ti­la­tion is a prob­lem that I see on many homes in the area and it causes a lot of prob­lems with pre­ma­ture roof fail­ures, ice buildup and mois­ture and heat buildup inside the attic.

Just about every­one knows that when they go into their attic dur­ing the sum­mer it is very hot (or cold dur­ing win­ter). This is nor­mal; how­ever, not hav­ing the attic ven­ti­lated prop­erly allows the heat to be trapped in the attic and the stag­nant air will often con­tain mois­ture that affects the insu­la­tion, roof­ing and can even affect the fram­ing mem­bers of the attic area.

Insu­la­tion must remain dry in order to func­tion prop­erly. It’s just like wear­ing a coat in win­ter while work­ing out­side. As long as the coat remains dry it is func­tion­ing at its high­est poten­tial to keep you warm. But if the coat gets damp either from sweat­ing or from snow or rain you start to get cold because the insu­lat­ing layer of the coat is now hold­ing mois­ture and the effec­tive­ness of the insu­la­tion is cut down to half or less. The same prin­ci­ple applies to the insu­la­tion in your entire home.

Mois­ture and exces­sive heat causes shin­gles on your roof to dete­ri­o­rate much quicker than nor­mal. Often cut­ting the expected life of the roof­ing in half or worse. Wood exposed to exces­sive mois­ture will warp, rot and dete­ri­o­rate over time pos­si­bly caus­ing seri­ous struc­tural dam­age to your house.

Proper ven­ti­la­tion keeps air mov­ing through the attic space and keeps mois­ture from col­lect­ing in the roof­ing, on the wood an in the insu­la­tion. If you want an exam­ple of how this works, think of a room in your house with a car­pet. If you sham­poo that car­pet and then shut all of the win­dows and doors to that room it may take all day or more for that car­pet to dry out. If you open all of the win­dow and doors and put a fan in one of the win­dows to help cir­cu­late air the car­pet will dry in a cou­ple of hours or less.

A prop­erly vented attic has vented sof­fits, a ridge vent on the peak or enough roof vents installed in the roof near the

Proper Air Flow in the attic

peak to han­dle the vol­ume of space in the attic and there should be not restric­tions to block the air flow from the sof­fit to the peak.

Per­fo­rated vinyl or metal sof­fit or vinyl or metal screens installed in wood sof­fit allow the air to enter the attic space from the eves of the roof.

Baf­fles and Rafter Vents are used to keep air flow mov­ing in areas where the insu­la­tion would oth­er­wise come into con­tact with the under­side of the roof. (I.e. Near the eaves or in vaulted/ cathe­dral ceil­ings with the dry­wall installed directly to the bot­tom of the rafters)

Attic Vents and Ridge Vents are installed at or near the peak of the roof to allow the air to escape through the top of the attic area.

The less restric­tion to the air flow from the eaves to the peak the bet­ter. I pre­fer to use ridge vents when­ever pos­si­ble instead of attic vents. The ridge vent spans the entire length of the roof and allows air flow from every pocket in between rafters. The attic vents are installed a lit­tle ways down from the peak and are only installed every few feet along the roof.