As energy costs increase and people
become more concerned about their impact on the environment, it
would seem to be logical to focus some of our efforts on building
better, more energy efficient homes. In the US, our homes and
businesses account for half of our energy usage. By building more
efficient houses, we reduce the energy they consume. This saves
energy over the life of the building or the next 50 to 100 years.
There are a number of ways in which we
can greatly improve the energy efficiency of our homes. This
document provides a list of things that can be done to build a
better, greener home. Some of these items cost next to nothing
while others do increase the total cost of the house. But, the
increase in initial cost can typically be easily offset by the
reduction in the energy cost over time.
The Building Envelope
Improving the energy efficiency of the
building envelope probably offers the biggest return on
investment. In the US, most new homes, even very expensive ones,
are being built using the same methods that have been utilized for
over 100 years.
2x4 frame construction is fine for
building a reasonably strong house in an efficient manner. But,
this type of construction is found lacking in a key area, energy
efficiency. Since the wall cavity formed by 2x4 construction is
only 3.5” deep, there is a limit to the amount of insulation
that can be installed. Simply increasing the framing members to
2x6s adds another 2” of insulation to the wall cavity. This
allows you to add 42% more insulation.
Wood framed buildings also suffer from
thermal bridging. This occurs when heat more easily travels
through the wood framing members, reducing the overall thermal
efficiency of the wall system. Other building systems do not
suffer from this problem to the extent that a stick framed
building does. Adding a layer of foam sheathing to the exterior of
the frame will further increase the energy efficiency of the
building and reduce thermal bridging to some extent.
Another large contributor to energy
loss with a wood framed building is air infiltration. Since a wood
framed building is constructed with many parts, there are many
cracks and crevices through which air can leak into and out of the
home which is air infiltration. Materials such as house wrap can
be used to help combat this issue, but it still remains a problem.
Again, other building materials do not suffer this problem to the
extent that wood framed buildings do.
Other building materials such as SIPs
or ICFs offer energy efficiency increases. SIPs, or Structural
Insulated Panels, are a composite material made of an inner layer
of EPS or other foam with an exterior skin of OSB on each side.
This creates a panel that is light, strong and very well
insulated. The most common thickness is 6”, but they can be
manufactured to almost any thickness desired. The thicker the
foam, the more the insulation value of the wall. SIPs are
typically used for wall and roof panels, but can be used as floor
panels also. SIPs are cut to size at the factory and assembled at
the job site to form the shell of the home. Since SIPs are made of
large panels, there are fewer areas for potential air infiltration
compared to frame construction, further improving energy
ICFs or Insulated Concrete Forms are
another high efficiency building option. ICFs are essentially
hollow foam blocks that are assembled at the job site to form
walls. Once the walls are complete, they are filled with concrete.
The concrete provides the structural part of the wall and the foam
on each side provides the insulation. Most ICFs have between 5”
and 5.5” of insulation. The concrete in the middle of the wall
acts as a thermal mass that buffers temperature fluctuations of
the building, adding to the overall efficiency. Since ICFs are
filled with a continuous layer of concrete, there is virtually no
air infiltration through the wall. These factors make ICF homes
very energy efficient. Additional advantages of ICFs are the
strength of the wall system and sound deadening. The steel
reinforced concrete inside the ICF wall makes them the strongest
common building material available for a home.
Regardless of what type of wall system
you choose, make sure that all the cracks and crevices open to the
outdoors are caulked well. Caulking is really cheap but can save
you a lot of money by reducing heat loss.
In addition to the walls, you also
need to consider the insulation below the floor and above the
In many homes, there is no insulation
below the floor whether the home is built on a concrete slab, over
a crawl space or with a basement. If the home has a slab floor,
insulation should be placed below the concrete before it is
poured. The typical method is to use 2” of foam sheets below the
slab. This insulation helps to keep the slab floor from
transferring your heating dollars to the ground below. A crawl
space or unfinished basement is typically cooler than your living
area. Heat will also transfer to these cooler areas below the
house, causing your HVAC system to replace it. Adding insulation
below the floor will reduce this heat transfer. If you have a
finished basement with a slab floor, it should have insulation
below the slab just like any other area with a slab floor.
The attic of your home should also be
well insulated. Most areas have requirements that specify the
R-value of your attic insulation. It is also important that care
is taken to carefully seal any areas of potential air infiltration
into the attic. Since heat rises, the warm air in your home will
try to escape through any small openings into the attic. Problem
areas include around light fixtures and electrical or plumbing
penetrations. These areas can be sealed individually or all at
once. One option is to apply a thin layer of expanding foam to the
floor of the attic (on top of the ceiling wall board) and then to
add a thick layer of fiberglass or cellulose insulation above it.
The foam seals all the air leaks and the other material provides
the bulk of the insulation. Or you could use expanding foam for
all the attic insulation, but this does increase your costs.
To verify rate of air infiltration of
your home, you can have a blower door test performed to help
identify any remaining air leaks. A blower door is a device that
is temporarily installed in an exterior doorway. This device has a
fan that pushes a known quantity of air into the house. The
technician can then determine how much air is leaking from the
building and where the leaks are. The goal of a blower door test
is to identify and eliminate any large areas of air infiltration
that can reduce the efficiency of the house.
The HVAC System
Most homes built today have some form
of HVAC system, which stands for heating, ventilation and air
conditioning. The most common type of system utilizes forced air
for both heating and cooling. The contractor who installs the HVAC
system calculates how large it must be to meet the peak demands of
It is very important that the system
not be too large for the home. An HVAC system that is too large
will do what is called short cycling. When an oversized system
turns on for either heating or cooling, it will only run for a few
minutes before it shuts off because the home has reached the
required temperature. The next time the system is called on, again
it will only run for a few minutes. To be efficient, an HVAC
system needs to run for an extended period of time. This is
especially important in the air conditioning mode. One function of
air conditioning is to remove excess moisture from the air inside
the home. If the HVAC system is short cycling, it has no chance to
remove this moisture. A properly sized system will run for a
longer period and do a much better job of removing moisture.
Besides having a correctly sized HVAC
system, additional energy savings can be gained with a dual speed
system. Most HVAC systems only have one speed, they are either on
or off. A dual speed system has two speeds or half speed and full
speed. Most of the year, you do not need the full capacity of your
HVAC system. The full capacity of your system is typically only
required on the coldest winter and the hottest summer days. Except
for days with extreme temperatures, you need less HVAC capacity. A
dual speed system provides you with this capability. The half
speed option allows the system to run more efficiently for longer
periods of time and consumes less energy. Of course a dual speed
system does cost more than a single speed system, but over time,
your energy savings will more than offset the extra cost.
Another important issue with the HVAC
system is the location of the air distribution ducts. The ducts
for your system should be located inside the temperature
controlled envelope of the home. The ducts should never be located
in a non-conditioned attic space. Non-conditioned attic spaces
experience extremes of heat and cold. Even though ducts placed in
an attic space may have a small amount of insulation around them,
you lose a lot of the energy when heating or cooling energy is
transferred to the non-conditioned area.
The joints in the ducts of the HVAC
system should be sealed to prevent air leakage. A special mastic
compound is commonly used for dealing the joints in the ducts.
Typical “duct tape” is not an acceptable method. After a year
or so, the adhesive on the duct tape will fail and you will have
Windows and Doors
If you are building a highly efficient
house, it makes sense to use good quality windows and doors.
In regard to doors, there are
typically solid wood doors and doors made from either fiberglass
or steel with some type of insulation material in the middle. The
solid wood doors are beautiful but generally require more upkeep
since they are a natural material. Fiberglass or steel doors lack
the natural beauty of wood, but they do generally require less
maintenance and offer better insulation qualities.
As far as windows, you have a few more
choices. Windows are typically made of wood, fiberglass, vinyl or
aluminum. You can also get wood windows that are clad on the
exterior with aluminum giving you the advantage of a durable
exterior finish while keeping the beauty of wood inside. Beyond
the style of any specific window, the most important things to
consider are their energy efficiency and the maintenance they will
require. Commercial aluminum windows are typically much less
energy efficient than residential windows.
The energy performance of doors and
windows is typically expressed as the U-value. The lower the
U-value, the better the thermal performance. Builder grade windows
generally have a U-value of around .35. Higher quality windows
will have a U-value of .30 or better. The same goes for doors,
there are many available that have a U-value of .30 or better.
Your windows and doors are one of the weakest points in the
thermal envelope of your home. Cheap windows and doors will reduce
the energy efficiency of your home and cost you money every time
you pay your utility bill.
Beyond the energy efficiency of your
windows and doors, you and/or your designer need to pay attention
to the quantity and direction your windows and doors face.
Since windows and doors have the
lowest insulation value of any part of your house, the more of
them you have, the less energy efficient your house will be.
Doors and windows can also impact the
energy efficiency of a house by their location in relation to
available sunshine. We all know that the sun rises in the east and
sets in the west. In the US, the winter sun will shine through
south facing windows, helping to warm the interior. During the
summer, the sun is at a steeper angle in relation to the ground
and will not shine into south facing windows with properly
Windows facing east or southeast will
typically capture the morning sun at all times of the year. This
may or may not be a good thing. You typically do not want the sun
warming the interior of your home on a hot summer day. West facing
windows pose additional problems. They will typically capture
sunshine during the hottest part of a summer day. This heat gain
will cause your HVAC system to work that much harder to keep
You can protect your east and west
facing windows with shades or awnings to help reduce heat gain.
You can also take advantage of trees to provide shade in required
Passive Heating and Cooling
Your home can also be more energy
efficient by taking advantage of passive heating and cooling.
Passive heating and cooling is simply heating or cooling our homes
using no mechanical means.
Our forefathers knew about passive
heating and cooling. They did not call them this, but they took
advantage of them just the same. They simply designed their homes
to take advantage of the suns heat in the winter and to allow
cooling breezes to flow through the home in the summer. We had
forgotten many of these features with the advent of mechanical
Passive heating involves allowing the
suns energy to enter and warm the home during the cooler winter
months. This is also called solar heat gain. The home should be
oriented with the long axis oriented east to west. This
orientation allows for windows to face due south for maximum solar
gain. Windows facing southeast or southwest will also allow solar
heating, but at a slightly less efficient level. If the roof
overhangs above your south facing windows are properly designed,
little of the suns heat will enter the home during the summer.
There does need to be a balance regarding the number of windows on
the south side of the home. Too many windows will allow in too
much energy causing the house to overheat, even on the coldest
The type of windows you utilize can
also make a difference. With the advent of low-E windows, you can
choose how much of the suns energy you allow into the home. Some
windows will block most of the thermal energy from the sun while
others will allow some of the suns energy to enter the home. Pay
attention to the solar heat gain coefficient (SHGC) of the windows
you buy. The SHGC is expressed as number between 0 and 1. The
lower the SHGC number, the less of the suns energy will be allowed
Different areas can utilize windows
with different SHGC ratings. If you live in the north, you may
want the maximum solar
gain and windows with a higher SHGC rating. If you live in the
south and do not need much passive heating, windows with a lower
SHGC rating would be appropriate.
Passive cooling involves designing the
house to promote a natural flow of cooling air through the
building. A typical design incorporates windows close to the floor
and some type of vent or outlet in the ceiling. The low windows
allow cooler air, preferably from a naturally shaded area to enter
the home and warmer air to rise out through the roof. This takes
advantage of warmer air rising and exiting at the roof.
Daylighting is simply using natural
light to illuminate the home. If ample natural light enters the
home, the need to use artificial light during the daytime is
reduced or eliminated, reducing energy consumption. The key with
daylighting is to admit enough light to make people feel
comfortable, but the incoming sunshine should not be enough to
cause the temperature in the room to increase.
There are a number ways to increase
the amount of daylight into all parts of the home. Again, the home
should be oriented lengthwise on an east-west axis. You want to
take advantage of sunlight from the south and north as much as
possible. Utilizing daylight from the east or west is problematic
because of the angle of the sun as it rises and sets. Windows on
the south side can be shaded in the summer to admit light but not
heat. Windows on the north side of the building will admit light
but rarely cause a problem with glare.
Clerestory windows or windows mounted
at the top of the wall, near the ceiling, are common
configurations to get natural light into the interior of the
building. Clerestory windows are typically a row of small
horizontal windows located in the upper portion of the roof. Like
other windows in the home, clerestory windows will admit light at
all times of the year, but can also admit direct sunshine during
the winter months to provide passive solar gain. Either clerestory
or high mounted windows might utilize a light shelf. A light shelf
is simply a horizontal shelf located just below the window
opening. The light shelf reflects the incoming sunlight back up to
the ceiling. This helps to further disperse and soften the light.
A light monitor is another way to
enhance daylighting. A light monitor is essentially a box mounted
on top of the roof with a window facing either south or north. A
south facing window would be shaded by the overhang to block
direct sunshine during the summer. Like a clerestory window,
sunlight enters the light monitor and is reflected down into the
room below. Light diffusing shades are sometimes used with a light
monitor to further disperse the sunlight.
Sun tubes are yet another option for
admitting natural light. A sun tube is a special reflective tube
and cover that mounts in the roof. The sun tube captures sunshine
and directs it down the tube and into the home. These are useful
for dark bathrooms and hallways. Sun tubes do not admit a lot of
light but do help in areas that would otherwise be dark.
You want to avoid the traditional
skylights. Skylights admit large amounts of sunshine and heat into
the home during the summer months. This direct sunshine can
increase the interior temperature of the home, causing the air
conditioning system to work harder and consume more energy.
Designing your home for adequate
daylighting can reduce your energy bills from lighting and
possibly reduce your heating bills in the winter by providing some
passive solar gain.
Energy Efficient Appliances and
Some appliances use more energy than
others. Typically, the less expensive models use the most energy.
You can reduce your energy consumption
by purchasing better quality, more efficient appliances. Energy
Star rated appliances are generally the most energy efficient.
One appliance that can make a big
difference is the clothes washer. Front loading washers use less
than half the water of the standard top loading models. This
reduces the amount of water used as well as the amount of water
that must be heated for washing. In addition, they spin the cloths
faster and remove more water from them before they go to the
dryer. Less water in the cloths means less drying time and more
Chances are the few dollars extra you
pay for a high efficiency appliance will be recouped over its
About 20 to 25 percent of all energy
used by a home is used for lighting. If you utilize more efficient
types of lighting, you can reduce your overall energy consumption.
The incandescent light invented by
Thomas Edison has been great for the past 100 years but has never
been very efficient. Of the energy used by an incandescent bulb,
only about 10% is converted into visible light while the remainder
is turned into heat. Today, there are number of lighting options
that use less energy.
Halogen lights use about 20% less
energy than incandescent lights. Halogen lights are typically
small, have high intensity and are available in a number of forms:
desk and floor lamps, surface mount lamps, track lights and
canister style lights. They also are available in a number of
wattages. One drawback to halogen lamps is that they get very hot.
Compact fluorescent lamps or CFLs are
another lighting option. CFLs use about 75% less energy than an
equivalent incandescent light. So, a 60 watt equivalent CFL will
only use about 14 watts of electricity. CFLs are not quite as
flexible as halogens in that there are a limited number to light
styles and wattages available and most of these cannot be used in
conjunction with a light dimmer. But, CFLs do use much less energy
and they can last many times longer than incandescent bulbs.
An emerging lighting technology is
LEDs or light emitting diodes. LEDs have been around for many
years in electronics and more recently in flashlights. But, many
manufacturers are working on bulbs that we can use in our homes.
LEDs hold great promise because they will use a fraction of the
energy of other lighting types and they will last even longer
still. Look for LEDs to become a viable option in the near future.
Making some good choices in your
appliances and lighting can save you energy and money on every
Solar Water Heating
Heating water consumes about 15 to 20
percent of the total energy used in the typical house. In most
areas, adding a solar panel to your roof to help heat your potable
hot water will reduce your overall energy usage.
Solar water heating setups are
typically active systems, requiring a pump and thermostatic
controls to turn the system on and off. The pump and control can
be driven off of standard line current or they can be run off of a
photovoltaic (PV) solar panel that can produce the electricity.
The beauty of a system that runs off of solar energy is that it
uses no energy and produces heat. The PV powered system does cost
This is a relatively short list with a
lot of parts. But, there is great potential to dramatically reduce
energy usage of your home without sacrificing comfort or
convenience. By taking more dramatic steps, you can reduce your
energy usage even more
If you choose to use some of these
energy saving options, you should check and see if you are
eligible for any government sponsored tax incentives. At this
time, there are tax incentives on geothermal heating and solar
water heating systems. There are also incentives for Energy Star
rated homes once the homes energy efficiency has been verified by
a certified technician.
You may also want to implement additional solar options
in the future such as PV electrical generation capability. As more
PV systems are sold, their cost will come down and they will
become even more economically viable. To prepare for this
prospect, you might do a few things to make your home “solar
ready”. You can work with your electrician to add a couple
un-used conduits from the mechanical room to a convenient location
on or near the roof. An access panel near the roof might also be a
good idea. You also need to leave a little spare space in your
mechanical room for the additional
power conversion components of the PV system. These steps
cost very little, but will make it much, much easier and cheaper
to add a PV system to your home at some point in the future.
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