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Soffit Vent Installation Pricing If you arrived at this page from a search, go to our main Radiant Barrier site. |
Soffit
Vents are probably the most over looked item in a house but
they are arguably the single most important item when figuring
your ventilation needs. You can have all of the roof top vents
you want, whether passive or powered, but if you don’t have any
way for the air to get up into the attic then they are not doing
any good. Imagine if you will that the soffit vents in your house
are like the intake on your vehicle; if they are clogged or
nonexistent, then your vehicle won’t run. In the same way, if
you do not have enough soffit vents, then your roof top vents such
as turbines or powered vents just won’t work. Also, if you don’t
have enough soffit vents, and you have powered ventilation, then
it can create a vacuum effect and begin pulling air from the
inside of your house from light fixtures, ceiling fans, and anywhere
else it can. Another thing that we commonly find is that the cutout
for the soffit vents don’t match the size of the soffit vent. In
other words, hole was cut too small for the vents. The solution
is simple; make sure that you have enough soffit vents to vent your
attic. Here at HeatBlockers we recommend one (1) cubic foot of
intake for every 200 square feet of attic space. A cubic foot
is 144 square inches and a regular 8” by 16” soffit vent has 56
square inches of free space. (You have to take into account for
the louvers and screening.) If you divide 144 by 56 you get about
2.5. That would mean that for every 200 square feet of attic
space you need at least 2.5 soffit vents. Take a 2000 square
foot house with an attached two (2) car garage for an example: 2000
square feet of living space, 400 square feet of garage space, and
500 square feet of covered porches = 2900 square feet total. Now
divide 2900 by 200, and you get 14.5. Now multiply 14.5 by 2.5 and
the answer is about 36, so for 2900 square feet you would need 36
soffit vents. I know this may seem complicated, especially if you’ve
been out of school for a while, but this is really a simple formula
that gets results and that’s what we’re after. To qualify for
the 20% or 30% savings guarantee there is no minimum amount of soffit
vents that HeatBlockers must install, but there must be a minimum
of one (1) cubic foot of intake for every 200 square feet of attic
space present in the home to qualify for either guarantee.
 Do soffit vents need to be replaced? |
 It's a dirty job, but someone has to do it! |
Research Exposes Attic Ventilation Myth |
Attic ventilation is the traditional way of controlling temperature and moisture in an attic. "New --and perhaps more effective ways -- will emerge from on-going research," says Rose. Meanwhile, builders rely on ventilation, so it should be done in the best way known. Purposes of Attic VentilationVentilating an attic reduces temperature swings. From your own experience, you know that a vented attic is cooler on a hot day than an unvented one. The cooling effect of venting has two benefits. First, it makes the home more comfortable during hot weather and reduces the cost of mechanical air-conditioning. Second, it helps get the rated life out of asphalt shingles. According to Rose, BRC research also shows a ventilated attic is slightly warmer on a clear, cold night than an unvented attic. In winter, venting maintains uniform roof sheathing temperature, which reduces the likelihood that ice dams will form. Without good ventilation, warm spots form near the eaves that melt snow, which can later re-freeze into a dam. More melting snow can build up behind the ice dam and damage the building. One of ventilation's primary jobs is to reduce the accumulation of moisture inside attics. BRC's research supports that idea. In side-by-side tests, air was permitted to leak into the attic from a humidified space below. More frost appeared on unvented attics than vented ones. Attic MoistureResearch at BRC and elsewhere clearly indicates that moisture is carried into attics from below on small currents of air. Moisture laden air leaking from the living spaces is one major source. Surprisingly, crawlspaces can supply much of the damaging moisture to attics. Moist air from crawlspaces rises through openings around plumbing, ducts and wires. Once in the attic, the air cools allowing its water vapor to condense on roof sheathing. "Don't rely on ventilation alone to take care of moisture in the attic," says Rose. "The best protection against condensation and mildew in the attic is a dry basement or crawlspace. Also important is an airtight ceiling." Driving ForcesMost people have been taught that warmer air rises and escapes from the high vents, while cooler air enters in lower vents. Thermal buoyancy is a major cause of air leakage from the living space to the attic, but research at the BRC shows that wind is the major force driving air exchange between an attic and the outdoors. "Our research shows that the role of thermal buoyancy in diluting attic air with outdoor air is negligible," says Rose. This requires rethinking about the design and location of attic vents. For example, some ridge vents may allow air to blow in one side and out the other, without drawing much air from the attic. Rose believes that ridge vents with baffles create better suction to draw air out. Soffit Vents
Rose considers soffit vents to be very important. "If a roof had only one type of vent device, I would choose soffit vents," he says, "because they work well as inlets and outlets." There's less problem with rain and snow getting in, because soffit vents point downward. To get maximum protection, locate soffit vents as far out from the wall as possible. If rain or snow blow into the soffit, it's less likely to soak the insulation or drywall. Soffit vents should always be installed whenever there are high vents. High vents, on ridges or gables, will pull air out of the attic. Without soffit vents, make-up air would be drawn through the ceiling, which increases heat loss and adds moisture to the attic. Because of the importance of soffit vents, Rose believes that at least 50 percent of the vent area should be low on the roof. More ResearchFor years, builders have discussed the merits of unvented roofs. Based on current information, venting attics seems to be a good idea. One of BRC's current research projects is looking into the question of unvented vaulted ceilings. Another study is looking into the merits of placing insulation just below the roof in a flat-ceiling attic. Including the attic within the conditioned space reduces heat loss from ducts, protects pipes from freezing, reclaims some storage and makes re-wiring much easier. Perhaps William Rose and his colleagues will soon dispel more attic myths.
Baffles Improve Ridge Vents
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When you hear the term "attic ventilation" you probably imagine that classic diagram of a simple gable roof with arrows pointing in at the eaves and out along the ridge. Real attics must not have seen those diagrams, because airflow rarely follows the arrows. William Rose, with the Building Research Council at the University of Illinois, has been conducting some of the first real research into how and why attic ventilation works. His findings can help you design and build more effective attic ventilation. And they may surprise you.
