Continuous Attic Ventilation
I'll never forget that day as long as I live. It was a typical late July day here in the Midwest. I was in the midst of a remodeling job that was running slightly (right, give me a break!) behind schedule (typical). Anyway, I had to cut a hole in a roof to extend a new plumbing vent stack out to the atmosphere. For some reason, I waited until after lunch to tackle this project. What a mistake!
I poked my head above the scuttle hole. Immediately I was enveloped by hot air. I mean really hot air. It was difficult to breathe and within a period of 30 seconds I began to perspire profusely. This particular house had no attic ventilation. The air was stagnant. It took 15 minutes to complete my task. Those 15 minutes seemed like 3 hours.
I would have sworn that it was 150 degrees F or better in that attic. The homeowner happened to have a highly accurate thermometer which we used to check it out. It turned out I was wrong. It was only 134 degrees F.
Why no Ventilation Fifty Years Ago?
That's a very good question. If you are a student of older housing, you will notice that older homes rarely incorporated ventilation as a part of the roofing system. Occasionally you would see tiny gable end vents. I don't know of one old house I have ever worked on that had any form of soffit or eave ventilation.
Ventilation of homes began in earnest during the 1970's. This coincided with the increased efficiency of doors, windows and vapor barriers. We simply began to build tighter houses.
Prior to the 1970's, houses used to breathe (lose energy) very easily. Who hasn't been in a drafty old home?? Energy costs were lower. It didn't seem to matter that the old gas conversion furnace was only 45 to 50 percent efficient. Old double hung windows had no weatherstripping. Many old houses had no insulation. Air could move freely between the inside and outside of these old houses. We actually were ventilating old houses quite well. However, we found out that it was expensive!
Times changed. The energy crisis of the mid-70's shocked us into reality. Windows and doors began to be built using very good weatherstripping. Insulation and vapor barriers were applied to outside walls. Within the past 15 years entire houses have been 'wrapped' with air infiltration barriers. All of those previous paths for air exchange have been blocked. Within a matter of years, problems began to develop with houses that were suffocating. None of these problems had ever been seen before.
Old vs. New
Thousands of other people have experienced the hot attic temperatures that I encountered on that hot July afternoon. Old houses have always had the same problem. However, because air conditioning has only been around for the past 40 years or so, hot attics were simply accepted.
The same is true for older houses in colder climates. These houses rarely experienced any attic problems in the winter months. If you are building a new home or are improving and upgrading an existing older home, you can expect trouble if you do not provide adequate ventilation for your attic.
Last Chance for Air
Unless you have a state of the art air exchanger, attic areas of today's house's are the only place where air can be exchanged with outside air. It is here that today's houses must breathe. This is one of the reasons continuous attic ventilation is so important.
There are lots of other reasons why ventilation is important. Continuous ventilation helps to reduce cooling costs, validates the warranties of some asphalt shingles, reduces heating costs in colder climates, reduces chances of moisture buildup in attics, etc. Trust me, continuous attic ventilation is the only way to go.
Continuous Ventilation
If you are not familiar with building or remodeling, you might be easily confused with continuous ventilation. Older homes, and even many modern homes have used different types of vents to exhaust air from attics. A common form is the triangular gable end vents found in many older homes.
Many people have metal 'pot' vents on their roofs. These vents simply cover holes cut into the roof.
Continuous ventilation products are different. These products began to hit the market approximately 15 to 20 years ago. The first ones were metal contraptions that replaced the cap shingles at the top ridge of your roof. Besides being unattractive, they often leaked.
In addition to the ridge vents, a continuous metal strip was often (and still is) placed in the soffit or under eave area to provide a place for fresh air to enter the roof. These strips of metal would run from one end of the soffit to the other in a continuous fashion, just like the ridge vent. Is it a little clearer now?
Column B335
