Proper Air Ventilation – Relief from the heat

Just Venting -- Proper air ventilation can give you and your hot house relief from the heat
By Tim Ryan
Star-Bulletin There are lots of ways to beat the heat in your home. And it doesn’t have to involve air conditioning.

You can try ceiling paddle fans or portable tabletop fans but any system, even air conditioners, have to work harder if the home is not properly ventilated.

Most homes have “passive” attic ventilation like eaves, gables or ridge vents. But passive ventilation is never enough to adequately reduce the 150-plus-degree temperatures that hot weather can generate in the upper spaces of a house.

This “hot box” effect acts like a giant radiator, transferring attic heat to the living spaces below. It compounds the cooling problem and sends utility bills soaring.

A first step in cooling a house means beefing up “passive” ventilation. You can do that by:

Increasing the number, size and type of vents.

Adding eave vents.

Installing gable vents.

Installing a ridge vent along the roof line.

Wind-driven turbines — those silver domes you see spinning on roofs — are also a consideration.

But no matter what method you choose, air exchange is the key. When over-heated air in your home or attic is vented and fresh air is pulled in to replace it, that’s air exchange. Cool air enters intake vents, which are located along the underside of the eaves. When air warms, it rises and moves out of the roof or gable attic vents.

Active ventilation systems use mechanical equipment — specifically fans — to exhaust hot air. Two of the most widely used are the attic fan and whole-house fan.

An attic fan, which costs less than $100 at most hardware stores, draws hot air out of the home and discharges it to the exterior. The hot air is displaced by cooler air, drawn in from vents in the eaves. A venting fan is generally placed at one of the highest points on the roof. Where a gable exists, a fan can be affixed to the inside face of the gable. In either case, the fan requires an electrical circuit, and more than one fan can be installed depending on the volume of air involved.


By Dennis Oda, Star-Bulletin
Panasonic’s whole house fan and other vent systems
are most effective when the outside air is cooler
than the air in the home.


The Home Ventilation Institute, a company that rates air conditioning and ventilation systems, recommends a minimum rate of 10 air exchanges every hour. The higher the air exchange rate, the better ventilated the home becomes.

A whole-house fan, which costs less than $250, does everything an attic fan does, but also ventilates the entire house, including the attic.

A whole-house fan draws in fresh air through windows and passes it through the attic where it’s exhausted through gable and other roof vents. You cool your home and attic at the same time, and get added benefit of fresh air.

The louvered-shutter intake system of a whole-house fan is typically installed in the attic floor at a central location of the home such as a hall. Installation is relatively simple. (All ventilating fans whether for a single room like those made by Panasonic or a whole house fan have CFM (cubic feet per minute) ratings. The rating gives you some idea of the unit’s ability to circulate air. Before buying a fan, estimate the volume of living space in your house so you know how much air the fan will have to circulate. Do this my multiplying the length of each room by the width and height, then adding the totals.

ImageOnce you’ve calculated your home’s volume, multiply this number by 0.33 to obtain the recommended fan rating. So a house that has 12,800 cubic feet of space will need a fan with a rating of 4,224 CFM.

Your attic may already have some roof vents, but with a whole house fan you may have to add more. Calculate the venting area by dividing the fans’ rating by 750. So 4,224 CFM divided by 750 requires 5.6 square feet of unrestricted vent area.

A whole house fans can cost three or four times as much as other fans, but they provide a tremendous amount of cooling effects like portable, ceiling and window fans combined.

If you only want to ventilate individual rooms, including bathrooms, take a look at Panasonic’s new Whisper Series ventilation system.

The six models — with noise levels ranging from rustling leaves to “a calm office,” the lowest currently available in a ventilating fan. The WhisperLites can ventilate up to 190 cubic feet of air a minute, or a room up to 500 square feet, depending on the model. Prices range from $94 to $229.

Ways to vent

WHOLE HOUSE FANS: The most effective and efficient, low-cost system for cooling a house. These are large fans mounted in the ceiling of the uppermost floor of a home. They work by drawing air from open windows in the house into the attic, where it is released through enlarged vents to the exterior. The air flow in the house can be controlled by the number and location of open windows, as well as the speed of the fan, which usually has several settings. Using a time switch allows you to set the fan to run at specific times.

ATTIC FANS: Attic fans, mounted on the roof, keep the home cooler by reducing the temperature of trapped warm air in the attic. If the attic is cooler, the house temperature will be lower and air conditioners will not have to work nearly as hard. These fans are inexpensive and run by a thermostat which turns the fan on automatically whenever the attic temperature goes up.

ATTIC VENTILATION: Drafty attics, not drafty houses, make for very efficient heating and cooling. In fact, a well-ventilated attic should be as close to the outside air temperature as possible. To achieve this, most homes should have a combination of ridge and soffit vents. The ridge vent, mounted along the entire peak of the roof, will allow trapped warm air and moisture to escape to the outside. To make this happen however, lower vents must be added at the soffit, which is at the underside of the roof overhang. With these vents installed, air is pushed into the soffits, rides up the underside of the roof sheathing, and exits the home at the ridge.

Learn more about Whole House Fans at Island Cooling Concepts

6 replies
  1. Lee
    Lee says:

    Two important comments regarding attic fans.

    The first is that for attic fans to be useful and ecomical they must be working! I have two attic fans in my attic and, after living in my home for several years, I decided to climb up into the attic and see if they were working. I found one fan had dropped out of it’s fitting and was resting on it’s fan so that it obviously couldn’t turn. And, believe it or not, the other attic fan motor was bad and had to be replaced. I’ve learned my lesson and would now recommend checking your attic fans a couple of time a year.

    The other important consideration is that attic fans should somehow be controlled to shut off in case of a house fire. One way this can be accomplished is with smoke detectors that can be wired so that, if a smoke detector goes off, it will cut the power to the attic fans. I was lucky in this regard as my house was already wired with such smoke detectors. I would think, at a minimum, that the attic fans should be wired to an easily accessible switch so they could be turned off in the event of a fire.

  2. admin
    admin says:

    Great point Lee. The whole house fan that we install come with a timer and on/off switch. Easy to access and manage.
    Also, if the fan was to not function properly, you would know when you turn on your whole house fan, as the shutters open when the fans turns on.
    We provide a 5 and 10 year guarantee on are work and products. Get a free cooling consultation: http://islandcoolingconcepts.com/services/consultation

  3. Bill Brown
    Bill Brown says:

    I own a “Turn of the Century – Post and Beam” house in Western NY. There were no heat ducts to the second floor as the house had a boiler/water system. I had air conditioners in every second floor bedroom,(4)and 2 more in the living room and dining rooms – my house looked like a porcupine and the summer electric bill was killing me! We still sweltered most evenings and the temp in my attic was so high that I could only remain in it a couple minutes at a time.
    After looking into the costs of air conditioning, learning that most of my trouble came from the heat in the attic I added insulation to the attic floor. This helped but not much.
    I decided to install an attic gable powered fan. I spent a total of about 2 hours hooking it up. The temperature change was so great and wonderful that I was now able to stay up in my attic all day, and the air conditioners on the main floor actually turned off on occasion. I decided to try my luck with a whole house fan. This cost me about another 2 hours, well maybe 3 hours – but I did it all myself. Oh! I also cut static gable ventilation holes on the other gables – just screening them inside and trim vents outside, because they said I would need to allow a lot of air to exit. I removed the 2 air conditioners on the lower floor and left the windows open, because they were on the shaded side of the house. Then I turned it on.
    Wow! Wow! Wow! The change in house temperature was immediate! I ran upstairs and took 2 more air conditioners out, feeling the cool shaded breeze flow past me into the house, as I did so.
    Over the last 2 years we have no air conditioners sticking out of windows, the attic is livable, and we are completely comfortable, with a slight breeze flowing from any [shaded side]open window cooling the rooms and whole house.
    I have to advise you DIY-ers that you might want to have the attic stairs door shut, and vacuum the attic dust a bit – prior to turning the whole house fan on. I goofed on that one – I really didn’t believe the manufacturers warning label, got a blast of attic dust all over the hallway – and then even after I THEN cut the extra gable vents, my neighbor seeing dust coming out of the vents came running over telling me he thought he saw smoke coming from my attic. I forgave him for not helping me install the fans, and we had a beer, while we watched a century of attic dust vent from my gables.
    I have noted that the powered gable fan does not turn on as often now that the whole house fan is installed.
    The Fans are quiet, you only hear the louvers open when they turn on. There even is a savings in winter heating too – because the house now is vented properly, allowing the heat to rise into the bedrooms. The fans have thermostats and also turn off switches but really I only adjust them around October and in May or June. The cost to run these fans is quite a savings, when compared to air conditioning! We are spending over $100.00 LESS a month, on our electric utility bill.

  4. jakveli
    jakveli says:

    Hi,
    Good healthy discussion. Poor home ventilation can accumulate contaminants which can threaten your health, such as formaldehyde. Instead of causing health problems, it can also lead to the growth of the mold which can further damage the furniture in your home. It is the reason why proper home ventilation is highly needed for your home. It is also a good way for reducing the bills for your air conditioning.

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