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Introduction
No matter how hot it gets in your home this summer, you can bet
that it’s even hotter in your attic. All that heat in your attic gets
transferred to the ceiling below, which will in turn heat the interior
of your house.
One way to solve this problem is to cool your attic with an attic
fan. An attic fan pulls in outside air through the roof vents and
forces hot attic air out through the fan. On a hot day, the outside
air can be 15 to 30 degrees cooler than attic air, even if your attic
is well vented. This exchange of air can make quite a difference in
keeping your attic and your house cool in the summer even if your
attic is insulated or you have air conditioning.
Choosing a fan is a relatively simple process. Decide how you will
mount the fan by reading the steps below, and then choose the
appropriate model. You can mount the fan to vent either through the
roof or through the gable. Next, choose the correct size fan by
comparing the manufacturer’s specifications to the square footage of
your attic space. If you have a large house, or will encounter
problems mounting a large fan, consider two smaller fans that together
will meet the manufacturer’s recommendations for your attic.
•
Beginner - 5 hours
• Intermediate - 4 hours
• Advanced - 3 hours
Caution ! Make sure you turn off the
electrical circuit you will be working on.
Caution ! Working in a hot attic can
lead to dehydration. Make sure you drink plenty of water and take
frequent breaks.
Caution ! When walking through an attic,
always step on the ceiling joists, never between them.
Helpful TIP
P
Make sure
your power source can handle at least a 15 amp draw from the fan. If
not, you will need to install a new circuit.
Helpful TIP
P Try to
purchase an attic fan with a temperature control switch (regulator) so
that it turns on and off as the attic heats and cools. This will
save money by not having the fan run continuously. It also makes
installation easier because no power switch will need to be installed
in the house.
Helpful TIP
PHeat
rises, so position the fan near the top of the roof for better
efficiency.
Helpful TIP
PFor the hot air to exit, outside air needs to come in. Make
sure that your existing roof vents are large enough
and not blocked by anything, such as insulation. To
determine if your existing roof vents are large enough, add the total
square footage of all in take vents together. The total should
be at least double the area of the fan opening.
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Learning Steps
1.
To
mount an attic fan on the roof, drill a starter hole out through the
roof. Next, with a reciprocating saw, start your cut in the starter
hole and cut a circle matching the diameter of the fan. Note: If you
have a tile, metal, or flat roof, this portion of your installation
should be done by a professional roofer as special tools and
techniques are needed to cut through and seal these roofs. Other
options are explained in step 4.
2.
Slip
the flange on the fan housing under the shingles that are above the
hole. It may be necessary to remove some of the shingles or cut them
back to accomplish this. Refer to the Replacing Damaged Shingles
tutorial to replace your shingles. Before putting the fan in place,
make sure to spread a generous amount of roofing mastic under the
flange to seal against water.
3.
Once in
place, nail down all four corners of the flange (the top corners can
be nailed through the shingles) and put some tar over each of the
nails. If necessary, also screw in place any hood or cover at this
time
4.
An
alternate method of mounting a fan is to mount it in the gable end of
older homes. Gable ends should have existing vents set between studs
that are 16-inches apart on center. To take advantage of these vents,
simply use a fan with mounting brackets that allow it to be mounted
across the studs (such fans are a common item). To make the fan work
more efficiently, put blocking between the studs, both above and below
the fan to direct the flow of air out. Note: If you do choose to use
an existing vent for your fan, there must be at least two other vents
of similar size to serve as intake vents. If not, you will need to
install more vents for the fan to work properly.
5.
With
the fan in place, remove the regulator cover and secure the regulator
to a near-by stud or rafter.
6.
Remove
a knock-out for the power supply cable. Install a cable clamp in the
hole, thread the cable through the clamp and tighten the clamp. Remove
the sheathing on the cable and strip the wires. Repeat the procedure
for the fan cable as necessary.
7.
Attach
the fan wires to the regulator wires as specified by the manufacturer.
Usually, all the white wires will go together, the black wires from
the supply line and regulator will go together, the black wire from
the fan will go to the red wire from the regulator, and the copper or
green ground wires will be connected to each other or a ground screw.
8.
When
the connections have been made, reinstall the cover to the regulator
and set the temperature control to about 95 degrees Fahrenheit. This
setting should provide a good compromise between energy efficiency and
cooling. Your fan is ready to start keeping your house cool, so turn
on the power and see how it works. Remember, if it does not come on
right away, it may not be hot enough in the attic. Try turning the
regulator down or waiting until the attic gets warmer before
concluding that the fan is not working.
Materials Needed
• Attic fan
• Roofing nails
• Roofing mastic (tar)
• Electrical cable (NM)
• Cable clamps
• Wire nuts
• Self tapping wood screws
Tools Needed
• Reciprocating saw
• Electric drill
• Drill bits and screw bits
• Hammer
• Screwdriver
• Putty knife
• Wire cutter/stripper
• Tape measure
• Work gloves
• Safety glasses
Attic
Insulation - Getting Ready for the Cold (and Hot)
Heat naturally
flows from a warmer area to a cooler one. It does this in only three
ways: conduction, where heat is transferred directly from mass to
mass; convection, the movement of heated air from one space to another
(hot air rises, heavier cool air sinks); and radiation, which simply
means that any warm body gives off heat toward a cooler one.
The function of
insulation is to minimize the radiation and convection transfer of
heat with a minimum of solid conduction so that our homes stay warmer
in cool weather and cooler in warm weather.
In this section I discuss the merits and uses of various types of
well-known insulations and inform you on how best to evaluate
R-values.
R stands for 'resistance to heat flow.' The greater the R-value, the
greater the insulative power. R-value requirements depend on factors
such as local climate and the surface you are insulating (walls,
ceiling, floor, etc.) and will be regulated by your local building
code. I suggest you contact the office of your city or county building
inspector for the requirements of your area. Each region of the
country has different requirements for adequate amounts of insulation.
In most areas, (see weatherizing section), local utility companies
will offer helpful suggestions on how to reduce your energy bills.
Many will arrange to have an expert come to your home to point out
areas that need to be insulated or weatherized. Often there is no
charge for this service and it may even lead to low- or no-interest
loan programs you may be eligible for. Also, state or federal tax
credits may apply.
Check with your State Energy Commission, local power company, or local
home center for the optimum R-value in your region.
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Safety
Safe-use practices are important when you work with any type of
insulation.
1.
Dust
mask and goggles are necessary for work with all types of insulation,
or when sawing wood.
2.
Fully
cover your body, if possible long sleeves, a hood, long pants, and
gloves. Insulating materials are skin irritants.
3.
Always
use the correct tool for the job.
4.
Be sure
power tools are properly grounded.
5.
Watch
power cord placement so that it does not interfere with the tool's
operation.
6.
A hard
hat should be worn, since roofing nails may be sticking through the
sheathing.
7.
If you
are not allergic to tetanus shots, be sure yours is current. There are
usually exposed, rusty nails in an old attic.
8.
Keep
the insulation clear (3" or so) from objects that transfer heat to
reduce fire hazards, and install sheet metal baffles around recessed
light fixtures, chimneys, and flues.
9.
In
older homes with possible frayed wires, do not allow the aluminum
vapor barrier of batt insulation to come in contact with the wire,
since it could short circuit
10.
Working
in attics or other hot areas can cause loss of body salt by excessive
sweating. Consider taking salt tablets.
11.
When
working outside on a roof, wear shoes or boots with rubber soles; stay
clear of power lines; secure extension ladders with safety hooks that
clamp over the ridge; and delay your work until the roof is free from
dampness of rain, frost snow, or dew.
12.
When
working high on the outside of the house, I suggest you rent
scaffolding to provide a balanced, level working surface.
13.
Do not
step through attic floor joists onto the ceiling of the room below. It
will give way.
14.
Some
types of insulation are flammable. Check with your local building
department and fire department for special application precautions or
restrictions.
Useful Terms
Caulk. A pliable material, usually forced into a gap or crack with a gun
or pressurized can, hardens into an effective seal against air and
moisture infiltration.
Cellulose . Blown-in or loose, consists of rock wool, glass fiber,
vermiculite, and/or perlite. Use this in floors, walls, and
hard-to-reach places. This type of insulation is poured between joists
or blown in with special equipment. It is best suited for use in
irregular-shaped areas and is the best option for blowing into
existing finished walls.
Fiberglass . Blankets or batts, a widely used insulator for walls,
floors, ceilings, roofs, and attics. Fitted and stapled easily between
studs, joists, and beams, I feel it is best suited for the
do-it-yourselfer.
Flexi-vent . A waffle-like strip of plastic designed to allow air
circulation to carry away moisture that could build up under
insulation.
Foam . Extruded polystyrene, isocyanurate board, and fiberglass board.
These rigid panels are used on unfinished walls, in new construction,
or on basement and masonry walls or exterior surfaces. The panels are
glued or cut to friction fit between studs, joists, or furring strips
and must be covered with drywall or paneling for fire safety. They
offer a high insulating value for a relatively thin material, but are
highly flammable, and some chemically based sprays or foams may
discharge poisonous films over a period of time. Be sure to use a
closed-cell, waterproof rigid panel in exterior applications or in
high moisture areas.
Furring. Strips of wood used to level out a surface prior to finishing.
Shims . Thin wedges of wood used to bring furring strips level with each
other when used on an uneven wall.
Silicate compound . Made of glass and sand. It does not burn,
release toxic fumes, nor attract vermin. It comes in lightweight
easy-to-handle bags and should be used in the same manner as loose
fill or cellulose.
Vapor barrier . Most common is a 6 mi. sheet of plastic attached over
insulation to eliminate moisture infiltration and deterioration of
insulation.
Tip : Working in your attic is hot and tiring. Try to work early in
the morning before it gets too hot. Carry a spray container of cold
water to spray on yourself and your fogged-up goggles.
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Attic
Furnace Continues to Heat Home During Warm Weather
By: Barry Stone
Dear Barry,
We are selling our
home that has a brand new asphalt shingle roof. We have noticed that
whenever the weather is hot, the forced air furnace in our attic turns
on. The only way we can get it to stop running is to shut off the
circuit breaker at the electric panel. We called a local home
inspector who advised us to install an attic fan. We took his advice,
but the new fan runs continually during warm weather, and this hasn't
stopped the furnace from blowing also. How can we solve this annoying
problem before we list the house? -- Doug
Dear Doug,
Your problem may be
the temperature limit switch in your forced air furnace. This is a
built-in thermostat, which lets your furnace blower know when to turn
on. Limit switches in furnaces are typically set to activate at about
150 degrees, and overheating of the attic during hot weather could be
causing it to turn on. What is surprising, however, is that the
problem has continued after installing a ventilation fan.
There are two
conditions which may be causing unwanted operation of your furnace
blower: The temperature limit switch may be turning on when
temperatures are less than 150 degrees. If that's the case, the switch
could need repair or replacement. If, however, the attic is actually
heating to 150 degrees, then additional ventilation is needed.
Therefore, my advice is two-fold:
First, have your
heating contractor check the limit switch to be sure proper adjustment
and operability. The switch may be set at a lower-than-normal
temperature, or it may simply be defective.
If the limit switch
is OK, place a thermometer in your attic on a hot day to determine
just how hot your attic is becoming. If the temperature is nearing 150
degrees, then installing a set of turban vents along the roof ridges
should adequately lower the ambient attic temperature during hot
weather.
Dear Barry,
The home inspector
who checked my house recommended anti-siphon valves for the lawn
sprinkler system. This came as a surprise, since the system works
perfectly. Please tell me the purpose of anti-siphon valves and
whether they're truly necessary. -- Lorne
Dear Lorne,
Anti-siphon
sprinkler valves are a form of backflow protection. Their purpose is
to prevent contaminated water from flowing back into the water supply
system of your home. The absence of anti-siphon valves indicates that
your irrigation system was installed by someone who lacks adequate
plumbing knowledge.
Your irrigation
pipes retain standing water long after the system is used. This water
can become stagnant, harboring bacteria and other micro-organisms. In
the event of back-siphonage, unsanitary water in the irrigation system
could contaminate the potable water supply. For this reason, the
Uniform Plumbing Code requires that all irrigation lines be equipped
with anti-backflow protection.
To ensure health
safety, you will need to hire a licensed plumber.
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Continuous Ridge Vents Offer Attic Ventilation Alternative
By: Paul Bianchina
While it’s an
acknowledged fact that an attic needs good ventilation, one of the
biggest objections that builders and homeowners have to installing an
adequate number of roof vents is that most of them can be unsightly.
They don’t match the color or style of the roofing, and can mar the
beauty of many carefully designed roof structures.
One alternative to
the traditional metal or colored plastic roof vents is to use a
continuous ridge vent. Continuous ridge vents are easy to install, and
they offer airflow right at the ridge – the highest point of the attic
where it’s needed most. The vent material is compatible with wood
shakes and shingles, composition shingles, roof tiles, and metal
roofing, and best of all, since the vent is covered over with the same
roofing that’s on the rest of the roof, it’s much less visible.
Combined with a sufficient number of low vents in the eaves or soffits,
it offers a workable alternative for ventilating just about any type
of attic.
How They Work
In normal roof
construction and roofing, plywood or waferboard sheathing panels are
installed over the rafters and meet snugly at the peak of the roof.
The roofing is then installed over the sheathing, and the joint where
the roofing material meets at the peak is covered over with a ridge
cap to seal the joint and finish off the installation. No rain can get
in, and no attic air can get out.With a continuous
ridge vent, the sheathing panels are installed with a gap at the
ridge, typically about two to four inches wide, depending on the vent
material being used. This gap allows hot attic air to escape, and is
often large enough that no other vents are required on the roof.
To cover the gap
and still allow air to move out of the attic, a special continuous
ridge vent material is used, of which there are a couple of different
types. Cor-A-Vent, one of the oldest and best know ridge vent
manufacturers, uses strips of corrugated polyethylene – similar in
cross-sectional appearance to a corrugated cardboard box – building up
four to six plys of the material in each strip. The strips have a
flexible fold and a v-cut profile along the centerline, allowing each
strip to be folded over the ridge sheathing. This allows the vent
material to cover the ridge gap, and air exits through the
corrugations.
Cor-A-Vent offers a
couple of different thicknesses of vent material – the thicker the
material is, the more ventilation area it has, but the higher it
protrudes up above the roof. Net free area for this material – the
actual air space in the vent, abbreviated NFA – ranges from 9 to 18
square inches per linear foot, depending on thickness.Another style, Celotex’s Roll Vent, is a two-layer composite of nylon and polyester
that creates a "fabric" with numerous small air gaps that allow air
circulation. The flexible matt comes in 20 and 50-foot rolls, and
conforms to roof pitches of 3/12 to 12/12. Here again, it is installed
over a gap in the sheathing, covering the ridge while still allowing
air to exit.
Roll Vent has an NFA of 18 square inches per linear foot
of material with either
material, no special tools or techniques are required for
installation. For existing roofs, the ridge shingles are removed
first, then a chalk line is snapped along each side of the ridge and
the roofing and roof sheathing are cut out along the lines to create
the gap. For new construction, the sheathing is simply stopped short
of the ridge. The gap is stopped short of each end of the ridge by
about six to 12 inches. Starting at one end, the vent material is
installed so that it is centered over the gap in the sheathing. The
material is held down with standard roofing nails, and can be cut with
snips or a utility knife.
Finally, to make
the installation weather-tight and cover the vent material so that it
blends in with the surrounding roof, ridge shingles of the same
material as the roofing are installed over the vent and fastened with
nails. Continuous ridge
vents are available wherever you purchase your shingles and other
roofing materials, and complete installation instructions are provided
with the material. Talk with your contractor or roofing supplier to
determine how much ventilation your roof requires, and whether you can
achieve sufficient ventilation with a continuous ridge. They can also
help you with special applications such as overly high or low pitches,
clerestories, and other situations.
Copyright 2002 Inman
News Features. Distributed by Inman News Features
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Creating Safe Attic
Storage
By: Paul
Bianchina
The quest for
additional storage space seems to be a continuous one, and there may
be some interesting possibilities right over your head. Attics can
offer a lot of potential for creating effective storage, but only if
you do it correctly.
The first
consideration with attic storage is safety – is the attic safely and
conveniently accessible, and can it safely handle the weight demands
imposed by storage. With this in mind, you'll want to begin with a
thorough inspection of the attic space to determine the structural
strength and the practical feasibility of using it effectively –
effectively being the key word – for storage.
Many attics, old
and new alike, are not framed with storage or living space in mind –
they are simply a dead space between the top of the ceiling and the
bottom of the roof. When looking at the ceiling joists to determine
their weight-bearing capacity for storage, there are three things to
take into consideration – the size of the joists, the center-to-center
distance between them, and the distance between the walls that support
them.
Once you've
determined these three things—all of which can be ascertained with a
quick look in the attic—discuss the situation with your local lumber
yard. They have lumber tables know as span charts that will allow them
to help you determine how much weight the attic can support, and what,
if anything, you may need to do to reinforce things.
If you have a newer
home and your attic framing has been done with engineered,
manufactured trusses, storage becomes more difficult. Engineered
trusses are very strong, but their configuration of intermediate
members between the ceiling and roof make accessible storage somewhat
impractical. Remember that you cannot cut trusses, so if you would
like to try and devise some storage up there, your best bet is to
discuss the situation with an experienced remodeling contractor or
with a local truss manufacturer.
If the attic will
safely allow for storage, then access to it is the next consideration.
Most attics are accessed via a simple hatch in the ceiling, which is
practical only for very limited storage that you won't need to access
very often. A better solution is to replace the attic hatch with a
pull-down attic ladder. These come in both wood and aluminum
varieties, in sizes to fit just about any standard application. They
are inexpensive and easy for the do-it-yourselfer to install, and are
readily available through most lumber yards and home centers.
Next, you need a
floor to place your stored items on. Plywood is an ideal material for
this use – use ¾-inch thick tongue and groove sheets, and install them
using adhesive and either screws or nails. The drawback to plywood,
however, is that it's often difficult to get the sheets into the
attic. If plywood is impractical, 1x6 tongue and groove boards may
prove to be an easier solution. In either case, you'll find it easier
to measure and precut the sheets or boards on the ground before taking
them into the attic.
Remember also that
you cannot cut any of the intermediate supports or braces that help
support the roof structure, so you'll need to work around them. You
will also need to be careful with any electrical wires that are laid
across the tops of the joists – you'll either need to reroute them
into the joist cavities, or furr up the joists so that the wires are
safely below the storage area floor. Whatever you do, make sure that
the wires are not subject to damage when installing the attic floor,
or from inadvertently stepping on them when moving around in the attic
space.
Lighting is the
next thing that makes for a safe and easily accessible attic – in
fact, most codes require that if the attic is accessible by stairs or
by a ladder, it must have a light that can be turned on and off at the
attic's entry. Depending on the amount of headroom you have, simple
porcelain single-bulb fixtures may be easy to install and provide
enough light. If you cannot maintain an adequate amount of clearance
between the bulb and any combustible material, then you'll need to use
a fluorescent fixture instead – they produce considerably less heat.
Remember that attic
conversions that require structural framing or electrical wiring will
require a building permit, and your local building department can help
you with understanding the applicable codes. If you have any questions
whatsoever about the structural integrity of your attic or how to work
with the necessary structural, electrical, or other changes involved,
do not proceed with any work – consult with your building department,
an experienced remodeling contractor, or even a structural engineer
before going any further.
Copyright 2002 Inman
News Features. Distributed by Inman News Features.
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Attic Fan
Installation
An attic should be ventilated year-round. In summer, ventilation
prevents excessive heat buildup, which may shorten the life of some
roofing materials and drive up cooling costs. In winter, ventilation
pulls out interior moisture, which tends to collect in attics and may
saturate insulation or cause mold and mildew to grow. In general, you
should provide vents equal to 1/300 of the ceiling area of the top
floor. For truly effective cross-ventilation, vents should be located
low (as soffit grilles or continuous soffit vents at the roof eaves)
and high (near the roof peak, in the form of either gable-wall vents
or fans, ridge vents, or roof ventilators).
This project describes the basic steps to install a powered
ventilator in a gable-end wall. Choose a model that is controlled with
a thermostat and, if moisture buildup has been a problem, with a
humidistat.
Materials List
·
Tape
measure
·
Work
light and extension cord
·
Pocket
calculator
·
Goggles
and dust mask
·
Extension ladder
·
Wall-mounted attic ventilator
·
Siding
removal/reinstallation tools as req'd.
·
2-ft.
level
·
Carpenter's square or combination square
·
Drill
and 1/2-in. spade bit
·
Portable jigsaw or reciprocating saw
·
Circular saw or crosscut handsaw
·
2x4
and/or 3/4-in. plywood
·
8d
common nails
·
Hammer
·
Neon
circuit tester
·
Standard and Phillips screwdrivers
·
Wire
stripper/cutter
1. Determine Fan Capacity: The Home Ventilating Institute recommends that
one or more power attic ventilators provide at least 10 air exchanges
an hour. Multiply the length by the width of your attic floor to
determine its area, and multiply the result by 0.7 to determine how
many cubic feet per minute (CFM) of air the fan(s) must move. (L x
W) x 0.7 = CFM
. Add 15 to 20 percent to the result for
steep roof pitches (such as 8/12 pitch, which means 8 inches of
vertical rise in 12 inches of horizontal run) or if you have dark roof
shingles.
2. Determine Intake Vent Requirements:
Divide the CFM capacity of the fan by 300 and multiply by 144 to
determine the minimum area (in square inches) of intake vents. (CFM
/ 300) x 144 = min. area (sq. in.)
For information on soffit vents contact The Home Ventilating
Institute (a division of the Air Movement and Control Association
International Inc.) at 847-394-0150.
3. Cut Wall Opening: Working from the top down, remove the siding
below the roof peak and center and level the template for the louvered
vent, as shown. Following the manufacturer's instructions, bore a
starter hole through the wall sheathing and cut the opening with a
portable jigsaw or reciprocating saw. (If you have an adequately sized
louvered vent, skip to Step 6.)
4. Frame the Opening: Provide framing and/or a plywood mounting
board, as directed by the manufacturer. Additional cutting of existing
framing from the inside may be required.
·
 Caution: Provide adequate work lighting. Lay
down a temporary floor, such as a piece of plywood, if needed. Wear
goggles and dust mask.
5. Install the Louver or Shutter:
Secure the exterior accessory shutter (shown) with screws and
reinstall the siding. Siding manufacturers are usually good sources
for how-to information on siding installation and repair, which vary
according to the type of siding.
6. Mount the Fan: Mount the fan to the framing or mounting
board with screws, as directed by the manufacturer.
7. Install the Controller: Remove any knobs and the cover so
you can secure the controller to the mounting plate or studs with
screws, and follow the manufacturer's instructions for locating the
unit. Do not substitute controls (such as solid-state speed controls)
that are not approved by the manufacturer.
8. Make Wiring Connections: All electrical work must be done in
accordance with local codes. If you are not familiar with basic wiring
procedures, hire a licensed electrician. Follow the manufacturer's
wiring diagram to make the connection to your power supply. Shut off
the breaker or remove the fuse for the fan circuit; and verify that it
is off using a neon circuit tester.
9. Adjust Settings: Thermostats and humidistat are adjustable.
Follow the manufacturer's guidelines and instructions to make the
necessary adjustments.
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