If you live in an area with
a moderate climate, you may be able to use a whole house fan for
most of your cooling needs and reserve your air conditioner for
the hottest hours of the day.
Whole House Fans Are Installed Inside The Attic Of A Home
The Optimal Time To Use A Whole House Fan Is When Outside
Temperatures Are Cooler Than Inside Temperatures (Usually Early
Evening & Morning Hours)
Cools Your Home At A Fraction Of The Cost Of Air Conditioning
The Problem:
During summer months attic temperatures can reach over 130
plus degrees Fahrenheit. The hot air trapped in the attic causes
the inside of the home to heat up. That's why if you ever lived
in a two story house you'll notice how much hotter it is
upstairs!
Point: Especially During Summer
Months Your Home Gets Hot!
Most every home has passive attic ventilation vents. Gable vents
can usually be found on the front or back of the home, soffit
vents are located in the eaves and ridge vents along the top of
the roof. On older homes you see those metal turbine vents.
These passive vents require wind or hot rising air to drive them.
Of course on very hot days there is usually very little wind and
the hot rising air can only escape through these vents very
slowly.
Some homeowners have tried to alleviate this problem by installing
attic fans. These are fans placed next to vents in the attic that
attempt to flush out the hot attic air. The attic fans however
does not flush the heated air from the living space of the home.
Point: Gable Mounted Attic Fans Do
Not Cool The Living Space
A very important Requirement: Roof
Venting Requirements:
As a
whole house fan pulls air your attic, the passive attic/roof vents
of your home allow the air to escape outside. Having an
adequate amount of attic/roof venting is a must. But exactly
how much venting is needed?
To Properly
Calculate How Much Roof Venting You Need:
Total CFM Of Fan(s) in attic /
750 = REQUIRED NET FREE AREA OF VENTING
Example: A 6000 CFM Fan would
require 8 square feet of net free venting.
HV1000 - Requires a min. of 1.34
sq. ft net free venting area
HV1600 - Requires a min. of 2.14 sq. ft of net free venting
area
Ghost - Requires a min. of 3.74 sq. ft of net free
venting area
Superfan - Requires a min. of 3.20 sq. ft (when exhausted
directly into attic)
How To Calculate Your Net
Free Venting Area:
First figure out what kind of
vents are in your home and where they are located.
Once you have this figured out,
measure the Length X Width of each vent. You will have
the area of each vent in square inches. Divide this
number by 144 to convert to sq. ft. But, we are not
done.
Since most vents are screened or
louvered, this restricts air flow by about 1/2, so we would
divide the number above by 1/2 to get the NET FREE AREA.
Calculating Net Free Area: L
X W in inches = GROSS AREA / 144 / 1/2 = Net Free Area
Example: You have 2 Gable Vents,
each is 12" x 12" in size they are screened.
Vent 1: 12 X 12 / 144 / 1/2 = .5
sq. ft Net Free Vent Area (NFVA)
Vent 2: 12 x 12 / 144 / 1/2 = .5 sq. ft NFVA
Adding the 2 vents NFVA will
yield a total of 1 sq. ft of NFVA
Traditional whole house fans are usually installed on the attic
floor and a hole is cut into the ceiling. These giant fans suck
the air out of the living area into the attic and out through the
vents. The traditional sizing method for a whole house fan is typically done by
taking the square footage of a home and multiplying by three. A
1800 square foot home would require a fan pushing over 5400 cubic
feet per minute (cfm) of air! These monster fans are usually very
loud and consume a lot of watts per hour. In order for these fans
to work properly, the attic space must have proper venting, in
this case over 7.2 square feet of unobstructed and open attic vent
openings. Most homes do not have this much attic venting and a
lot more attic vents must be added. This means cutting holes in
the roof or side of the home so the hot air being blown by these
fans can properly escape the attic space.
So why is this method used for sizing
whole house fans? The theory has been that you need
such a large fan to create a breeze through the home to cool the
people as well as the building. The breeze moves air over the
skin which makes the occupant cooler. Unfortunately, the fan
required to move that much air is loud and people don't like the
noise and so they turn the fan off.
And there is a maintenance issue with these large fans. Many are
belt driven, which requires belt maintenance, and they all require
some type of home-made cover that is used, at most, twice a year.
The homeowner has to climb into the attic to cover or uncover the
fan or live with the heating or cooling losses.
Remember with the standard 24" and 30"
traditional whole house fans your attic must be able to support
the flow of air out, most homes don't have this amount of attic
ventilation. Moreover, the larger fans are louder, consume more
energy, require maintenance, and are not well insulated! In fact
these huge fans pump so much air that they may actually send hot
attic air back down into your home.
A Whole House
Fan That Moves 6000 CFM Of Air Will Require 16 sq. ft of
total roof venting, or 8 sq. ft of net free area.
Our Philosophy & Solution:
We believe a more effective means of
cooling the home, is not by blasting it with large amounts of
airflow as done with a traditional whole house fan. In fact,
having a balanced flow, that is adequate for cooling is more
efficient and much more effective.
At the end of the day, when the sun
sets and evening approaches, your home has literally turned into a
giant hot box. The roof, attic, walls and structure of your
home radiate stored heat from the sun - right into your living
area. Your home remains incredibly warm, yet, outside it is
cooler. Constant ventilation, over a period of time will
effectively remove the stored heat built-up in your home and cool
it down. This can be accomplished with one of our fans below
depending on the size of your home:
The HV1000 - HV1600 - Superfan™ - Ghost Fan...
The
chart below depicts whole house air exchanges (in minutes),
depending on the size fan and square footage of home:
House Size
HV1000
HV1600
Superfan™
Ghost Fan
Air Flow
1000 cfm
1600 cfm
2400 cfm
2800 cfm
1500 Sq. Ft
12 minutes
8 minutes
5 minutes
4.3 minutes
2000 Sq. Ft
16 minutes
10 minutes
6.7 minutes
5.7 minutes
2500 Sq. Ft
20 minutes
12.5 minutes
8.3 minutes
7.1 minutes
Ambient air temperature in the home
will drop within the first few air exchanges, it will take a
constant flow of cooler outside air, and multiple air exchanges to
remove the tremendous amount of stored heat from your home.
These fans will expedite the cooling process, making your living
area comfortable and cool.
