© D. R. Wulfinghoff 1999. All Rights Reserved.

Passive Solar Heating

Subsection

8.4

INDEX OF MEASURES

8.4.1 Keep open the window shades of
unoccupied spaces that need heating.

8.4.2 Install combinations of sunlight absorbers
and reflectors inside windows and skylights.

8.4.3 Install solar enclosures over areas that can
benefit from heating.

RELATED MEASURES:

•

Subsection 5.6

, for heat pump loop systems.

These systems can transfer heat from sunlighted
areas to other parts of the building

•

Subsection 6.3

, for reduction of air leakage

through windows

•

Subsection 7.3

, for reduction of conductive heat

loss through glazing

•

Subsection 8.1

, for glazing and shading

principles

•

Subsection 8.3

, for daylighting issues

The Measures of this Subsection exploit

passive solar heating for a limited number of
applications. These Measures tap only a small
fraction of the theoretical potential of passive
heating, but they are practical to try without a
great deal of pioneering. Exploiting passive
solar heating to a greater extent involves a
major commitment to unproven methods. For
the perspective that you need to be successful
in this fascinating and risky area, see

Reference

Note 47

, Passive Solar Heating Design.

1008

8. CONTROL AND USE OF SUNLIGHT

ENERGY EFFICIENCY MANUAL

If windows face the sun for at least part of the day,

they receive enough sunlight to provide a significant
amount of heating for the space. However, windows
exposed to direct sunlight usually have shades or blinds
to prevent glare. These shades may be left closed when
the space is vacant, wasting the potential of passive
heating.

If a space is vacant during long periods of daylight,

open the shades during cold weather to admit solar heat.
Accomplishing this requires people who can be assigned
the task of opening the shades. For example, this
responsibility can be assigned to maids for hotel rooms,
to teachers for classrooms, to nursing staff in hospital
rooms, and to the occupants of single-person spaces.
Security patrols can be assigned this responsibility in
many types of facilities.

Opening shades or curtains reduces their insulating

value at night. This is not much of a penalty, because
ordinary window shades and curtains provide little
insulation. Convection bypasses them. The gain in solar
heating during the daytime is much greater than the
increase in heat loss overnight. This being said, try to
close the curtains overnight, but only if you have a
reliable procedure for opening them again before sunrise.

Energy Saving Potential

Throughout the middle latitudes, windows facing

in any direction from southeast to southwest admit about
1,000 BTU per square foot of window area per day
during winter, if the sky is clear. Conventional window
treatments absorb 30% to 70% of this heat when they
are closed. If they are kept open, all the heat gets into
the space.

The total annual saving depends on the number of

daylight hours during which the space is vacant, the size
and orientation of the glazing, the clearness of the sky,
the number of days requiring heating, and the heating
requirements of the space.

This Measure may also save a significant amount

of lighting energy, especially at the beginning of
occupancy periods. For example, hotel guests arriving
during the day typically rely on daylighting for most of
their room lighting, provided that the windows provide
satisfactory lighting.

MEASURE

8.4.1

Keep open the window shades of

unoccupied spaces that need heating.

New Facilities

Retrofit

O&M

RATINGS

A

SUMMARY

An easy way to save heating energy in spaces
that are vacated for long periods.

SELECTION SCORECARD

Savings Potential ...................

Rate of Return .......................

Reliability ...............................

Ease of Initiation ....................

Explain It to the Staff and Occupants

This sort of procedure tends to be neglected. Use

whatever administrative methods work in your facility
to keep the procedure in effect.

Ask occupants to control the shading to conserve

energy. Placards are usually the best way to do this.
See

Reference Note 12

, Placards, for guidance in

designing and installing placards.

ECONOMICS

SAVINGS POTENTIAL: 20% to 80% of heating costs
in the sunlighted spaces, depending on the factors
discussed above.

COST: Usually minimal. Customized placards typically
cost about $1 to $5 apiece, in quantity.

PAYBACK PERIOD: Immediate.

TRAPS & TRICKS

ADMINISTRATION AND COMMUNICATION: This is
primarily a matter of effective leadership and
communication. Back up your request with a well written
memorandum to the responsible managers. Show
people what needs to be done. Say please and thank
you.

MONITOR PERFORMANCE: This kind of procedure
tends to fade away. Keep it refreshed by periodic
contacts with the departments responsible. Put this in
your tickler file.

1009

8.4 PASSIVE SOLAR HEATING

© D. R. Wulfinghoff 1999. All Rights Reserved.

SUMMARY

A simple but unconventional technique that
can provide comfortable heating, and perhaps
enhance daylighting. Uses conventional
materials and equipment in a clever manner.

SELECTION SCORECARD

Savings Potential ...................

Rate of Return .......................

Reliability ...............................

Ease of Retrofit ......................

Measure 8.4.1

points out that most glazing exposed

to sunlight is equipped with shading devices that block
out the sun completely, wasting the sun’s heating
potential. The inexpensive procedure recommended by

Measure 8.4.1

is not effective for exploiting passive

heating when spaces are occupied, because it does not
correct glare problems that motivate people to close the
shading.

A simple concept for exploiting solar heating while

controlling glare is to install an absorbing surface inside
the glazing that converts the sunlight to heat. There are
two differences between the heat absorber and
conventional window treatment:

• the absorber is intended to absorb heat, rather than

reflecting it. It does this with an outward facing
surface side that is dark.

• the absorber is installed far enough inside the space

so that it acts as an efficient convector. The absorber
does not have to intrude far into the space.
However, you can install the absorber anywhere in
the space where it will intercept direct sunlight and
kill glare.

If absorbers are installed close to glazing, they can

reduce the chill that occupants feel in cold weather when
they are near glazing. When sun is shining through the
glazing, the absorbing surfaces are warm, so they act as
low-temperature radiators. When sun is not shining
through the glazing, the surfaces limit radiation heat loss
from the space to the windows.

You can make the heat absorbing surfaces from any

opaque or translucent material, such as fabric. With a
bit of creativity, you can use this Measure in most types
of facilities, while adding a decorative touch.

In most cases, you still want to be able to minimize

the cooling load during warm weather. You can do this
by having a reflecting surface just inside the glazing
when heating is not desired. In retrofit applications,
you can keep the original window shading devices to
serve this purpose.

An Example for Windows

You can put this concept into practice in many ways.

For example, you can use two conventional venetian
blinds. Install a highly reflective venetian blind as close
to the window as possible, in the conventional manner.
Install a second, highly absorptive venetian blind on a
bracket that holds the blind about six or eight inches
inside the wall. The inner blind can be a conventional
blind that has a dark, fairly dull color. Suspending the
dark blind inside the space keeps the convection from

the dark blind from scrubbing the stagnant air layer off
the window surface.

Only one blind is used at a time. When the weather

is warm enough that passive heating is not useful, the
reflective blind is lowered, and the dark blind is raised
out of the way. Occupants adjust the reflective blind in
the normal way to avoid glare and exploit the view as
much as possible.

When passive solar heating is desired, the reflective

blind is raised and the dark blind is lowered. Again,
occupants adjust the dark blind in the normal way to
avoid glare and exploit the view as much as possible.

Sunlight comes through the window at various

angles. Therefore, the absorbing blind may have to be
much larger than the window to keep sunlight from
entering the space around the sides of the blind.
Alternatively, you can install side fins, projecting from
the wall, to keep sunlight from getting around the dark
blind.

An important advantage of this technique is that the

effectiveness of passive heating does not depend on
occupants adjusting the blinds in any particular way.
Most of the sunlight that enters the window is captured,
no matter how the dark blind is set. The purpose of the
dark blind is to capture most of the solar heat even when
occupants close the blind to avoid glare.

Heat circulates through the space by convection, as

with a conventional convector. The effectiveness of the
circulation depends on the geometry of the space. In a
space with a horizontal ceiling, the warm air circulates
throughout the space. Cooler air remains near the floor.
This cooler air is heated only if the warm part of the
heat absorber is low enough to reach it.

Therefore, this method alone may leave an

uncomfortable cold air layer near the floor. This is true
even if there is ample solar energy. For this reason,

MEASURE

8.4.2

Install combinations of sunlight

absorbers and reflectors inside windows
and skylights.

New Facilities

Retrofit

O&M

RATINGS

C

C

1010

8. CONTROL AND USE OF SUNLIGHT

ENERGY EFFICIENCY MANUAL

expect to use another method of heating the air near the
floor. The most efficient solution is to let sunlight shine
on a dark part of the floor near the window, if you can
do this without creating glare.

Or, you might rely on your conventional heating

equipment, such as a baseboard convector, but this uses
purchased energy. (Any space needs a conventional
heating system for periods when there is no solar energy
available.)

Or, if the space has a forced-air heating system, keep

the circulating fan running at low volume. The heating
system must have a low-speed fan setting for this to be
acceptable. Running a heating unit fan without heating
the air will cause a wind chill effect on people. The air
velocity must be kept low enough so that this effect is
not objectionable.

An Example for Skylights

Skylights can produce oppressive heat and glare that

motivates building owners to remove them or to paint
over them. This wastes their potential for passive heating
and daylighting.

A general approach that captures the heat of

skylights while avoiding glare is to install a light
absorbing screen under the skylight. The screen can as
simple as a hanging of dark fabric. This solution avoids
the need for any additional structure, and the fabric is
easy to attach.

In a space that uses skylights, the heat absorber will

be visually prominent. Use it to create pleasant
daylighting. At the same time, exploit its potential as a
decorative item.

There is a fundamental problem when using heat

absorbers with skylights, or with other glazing that is
located high in the space, above the level of the
occupants. The heat absorber releases virtually of its
heat by convection, so all the heated air rises to the space
above the absorber. The absorber itself cannot project
heat downward.

To solve this problem, try to feed the heat through

the existing heating system, if it uses fan-forced
circulation. This requires an air return located above
the absorber, preferably near the top of the space. This
is so important for the effectiveness of passive solar
heating that you should consider adding an appropriate
air return if none presently exists.

Even if the heat from the absorber cannot be

distributed through existing heating equipment,
installing the absorbers can still be a better alternative
than abolishing the skylight. In a space with skylights,
it is likely that most of the heat loss from the space occurs
through the skylights themselves. The heat absorber
allows the solar energy passing through the skylight to
offset the heat loss from the skylights without creating
visual problems inside the space. (During most daylight

hours, a skylight takes in much more energy than it loses
by conduction.) The warm air bubble created at the
ceiling level eliminates radiation cooling of the space
below, improving comfort. And, the heat absorber can
be designed to create effective daylighting.

Energy Saving Potential

Throughout the middle latitudes, windows facing

from southeast to southwest admit about 1,000 BTU
per square foot of window area per day (about three
kilowatt-hours per square meter per day) during winter,
if the sky is clear. Conventional shades typically absorb
30% to 70% of this heat. The heat collecting devices
suggested here may capture 90% of the heat.

The total annual saving depends on the size and

orientation of the glazing, the clearness of the sky, the
number of days requiring heating, and the heating
requirements of the space.

The potential saving depends on the transparency

characteristics of the glazing. The devices recommended
by this Measure capture only the solar heat energy that
passes through the glazing. If the glazing is tinted or
reflective, or if it has special features to block solar
infrared radiation, the value of this Measure is greatly
reduced.

Design Guidelines

This technique is unconventional, so you have to be

an innovator. While you are being creative, follow these
guidelines.

Select the glazing transparency for
the application.

This Measure provides the greatest heating benefit

if the glazing transmits a large fraction of the sunlight
that falls on it, whether the glazing is clear or translucent.
Glazing that is highly absorptive or highly reflective
reduces the potential for passive heating so much that
this Measure may not be worthwhile.

In new construction, you get to select the glazing.

If you select clear glazing to maximize the benefit of
this technique, the building will be married to it. This
is a novel technique, so think hard about this decision.

Distribute the heat into the space effectively.

Provide enough clearance at the top and bottom of

the absorber to allow free convective circulation. Install
the absorber far enough from the wall so that the
convective current from the screen does not scrub the
surface of the wall. Leaving the wall’s air layer intact
reduces heat loss somewhat.

The absorbing device distributes its heat to the space

mostly by convection. The absorber does not become
warm enough to radiate strongly. The amount of heat
that the absorber emits by radiation depends on the
absorber’s temperature and emissivity. Most non-
metallic materials that you would use to make heat

1011

8.4 PASSIVE SOLAR HEATING

© D. R. Wulfinghoff 1999. All Rights Reserved.

absorbers have high emissivity, which increases the
amount of heat they transfer to the space by radiation.

Too much heat radiation may be uncomfortable for

occupants who are near the absorbing surfaces, but this
is unlikely. If you want to decrease radiation and
increase convection, use surfaces of low emissivity. This
means smooth metal surfaces, or metallic coatings.
Another method is to install a second screen inside the
absorber. This innermost screen will block heat radiation
regardless of its other characteristics (color, weight, etc.),
as long as it is opaque.

If the heat absorbing surfaces are located high in

the space, as with skylights, design them to radiate as
much heat as possible downward to the occupied space.
Heat that is transferred by convection rises. If this heat
accumulates above the occupied space and does not
circulate, it has limited value.

Be able to reject excess solar heat.

In most buildings, there are times when sunlight

could overheat the space. To deal with this, provide
reflective shades or other methods of reducing cooling
load (See

Subsection 8.1

). In retrofits, the original

shades may serve this purpose adequately.

Some large skylights have vents or openable panes

to get rid of heat gain during warm weather. Make sure
that any vents are airtight when closed, or they may waste
large amounts of heating energy. (See

Measure 6.4.4

about this.)

Exploit daylighting.

This technique has potential for daylighting. The

trick is not to absorb all the entering sunlight, but to
distribute some of it within the space in a glare-free
manner. See

Reference Note 46

, Daylighting Design,

for the full story on daylighting.

Preserve the view, if there is one.

If the glazing offers a good view, try to make it

available. For example, using a pair of venetian blinds,
as in the previous example, accomplishes this.

Minimize waste of useful space.

Space inside a building is valuable. Also, devices

that stick out are more likely to be a nuisance and get
damaged. Design the absorbing devices to use a
minimum of space that is useful for other purposes.

Have a sense of style.

Make this an opportunity to enhance the appearance

of the space. For example, using fabric heat absorbers
offers endless possibilities for decor.

Avoid condensation damage.

Skylights are prone to serious condensation. The

absorbers will make the glazing colder at night because
they shield the glazing from the warmth of the space.
This aggravates the condensation problem. The
condensation may damage your absorbers and cause
other problems. See

Reference Note 47

, Passive Solar

Heating Design, for ways of reducing condensation.

Don’t interfere with fire egress.

Windows may be potential escape routes in the event

of fire, or points of entry for firefighters. Do not install
devices that conflict with safety.

Select materials for longevity.

Select materials that resist sun damage. If the

absorbers can come in contact with people or moving
equipment, design them to resist impact. Select movable
components that resist wear. For example, pull cords
should be designed so that they do not fray or jam. Select
equipment that allows worn components to be replaced
easily.

Explain It to the Occupants

The heat absorbing devices are vulnerable to being

misused or abandoned because their purpose is not
obvious, or because they appear to be a nuisance.
Therefore, make people aware of their purpose. Also,
if the shading devices require any human control, explain
how to use them. Placards are an effective means of
doing this. See

Reference Note 12

, Placards, for

guidance in designing and installing placards.

ECONOMICS

SAVINGS POTENTIAL: 10% to 100% of heating costs
in the sunlighted spaces, depending on the factors
discussed above.

COST: Varies widely. You probably cannot invent
anything that will cost less than $100 per window. Heat
absorbers for large skylights will cost much more.

PAYBACK PERIOD: Several years or longer.

TRAPS & TRICKS

THE HAZARDS OF PIONEERING: This is an unusual
concept. You have to develop it into a practical
configuration. Don’t try it unless you have the time and
the discipline to work out all the details. Set up a test
installation before extending your concept to many
windows or skylights.

1012

8. CONTROL AND USE OF SUNLIGHT

ENERGY EFFICIENCY MANUAL

MEASURE

8.4.3

Install solar enclosures over areas

that can benefit from heating.

New Facilities

Retrofit

O&M

RATINGS

C

C

The ultimate in passive solar heating is creating a

space that is heated entirely by sunlight. Many facilities
have opportunities for using a glazed enclosure to cover
an outdoor space, providing free heating for at least part
of the year. The enclosure does not have to be made of
glass. It can be made of any material that admits enough
solar heat to offset the heat losses. Materials include
glass, plastic glazing materials, translucent panels, thin
plastic sheet, and more unusual materials.

Where to Consider Glazed Enclosures

Greenhouses are by far the most common type of

glazed enclosures. Figure 1 illustrates the range of types.
Experience with greenhouses provides valuable lessons
for employing glazed structures for any purpose. For
example, Figure 1 shows the major heat venting and
ventilation requirements.

One purpose of glazed enclosures is to make an open

space usable for a more valuable purpose. For example,
the front of a restaurant may be turned into a sidewalk
cafe.

Another purpose is to extend that length of time

that a facility can be used. For example, Figure 2 shows
a patio restaurant in a mid-latitude location that is usable
for three or four months per year. Installing a glazed
enclosure would approximately double the usable
period. Furthermore, it would make the space usable in
rain and wind.

Enclosing an outdoor swimming pool, as in

Figure 3, typically extends its season of usage by several
months.

Another purpose is to reduce heat loss from adjacent

space, as when enclosing the common area of a shopping
center.

Large glazed enclosures have the ability to collect

enormous amounts of passive heating, and they are able
to keep themselves warm even in cool climates. Figure 4
shows a huge courtyard in a Tennessee tourist hotel that
is enclosed with glazing, making it comfortable under
almost all weather conditions.

Beware of Unexpected Heating and Cooling Costs

There is a fly in this ointment. The glazed enclosure

is able to heat itself only during the daytime, and heating
is substantially reduced when the sky is overcast. The
nature of the activity may require the space to operate
when passive heating is not adequate. Or, the owners
may discover that the increased value of the space makes
it worthwhile to operate the space at night. In this case,
heating equipment is needed. Unfortunately, a simple

glazed enclosure has only minimal insulation value. In
the end, energy cost may be increased rather than
decreased. If you examine glazed enclosures, you will
see that many are heated in ways that require a large
amount of energy.

Furthermore, a glazed enclosure may overheat badly

during warm weather, and even during mildly cool
weather. This sometimes prompts owners to install air
conditioning. This can be very expensive, even in mild
climates.

This leads us to an important point. Before installing

a glazed enclosure, consider how the space is likely to
be used afterward. If the space will be heated, design
the enclosure to minimize heat loss. Also, try to prevent
overheating without resorting to air conditioning.

Energy Saving and Comfort Benefits

Consider this Measure primarily as a way of

improving comfort and/or space utilization. In some
cases, you may reduce energy consumption at the same
time. Or, you may achieve the improvement in comfort
and/or space utilization at a relatively small additional
energy cost.

If the newly enclosed space is not conditioned, there

is no increase in energy cost. If it connects to conditioned
spaces, it may substantially reduce energy cost. For
example, enclosing the walkways of a shopping mall
radically reduces heat loss from stores that are open to
the walkway.

But, beware of using a glazed enclosure as a

substitute for a properly designed building or building
addition. Again, consider the ultimate mode of use.

Design Guidelines

A glazed enclosure is not as simple as it looks, if

you want it to be comfortable and efficient. Concentrate

SUMMARY

An opportunity to make space more useful
without increased heating costs. Not as
simple as it looks.

SELECTION SCORECARD

Savings Potential ...................

Rate of Return, New Facilities

Rate of Return, Retrofit .........

Reliability ...............................

Ease of Retrofit ......................

1013

8.4 PASSIVE SOLAR HEATING

© D. R. Wulfinghoff 1999. All Rights Reserved.

on the following points to achieve efficiency and
comfort.

Minimize the heating load.

The insulating value of all transparent and semi-

transparent glazing materials is poor. Furthermore, if
the glazing is slanted away from the vertical, its
insulating value declines radically, typically by a factor
of two to three, compared to vertical glazing. The poor
insulation value does not matter as long as the enclosed
space remains unheated, because solar heat gain will

make the space much warmer during daylight than it
would be if it were left open.

Some composite glazing materials, discussed in

Measure 8.3.3

, offer fairly good insulation value. These

materials are bulky and expensive. They offer no sense
of the outdoors, and they have low light transmission.
However, they can be used effectively in combination
with transparent materials.

If the enclosed area will be used extensively during

hours of darkness, use insulating panels for a

Super Sky Products, Inc.

Fig. 1 Plain and fancy greenhouses The upper one is made entirely of extruded double-wall plastic. The bottom one is made
of glass. All glazed enclosures should apply the lessons that have been learned from a vast number of greenhouses. In both of
these, notice the extensive vents that are located at high points. Venting is necessary for free temperature control in any application.

WESINC

1014

8. CONTROL AND USE OF SUNLIGHT

ENERGY EFFICIENCY MANUAL

WESINC

Fig. 2 Prime candidate for a glazed enclosure This is the roof garden of a busy pizza restaurant at an
oceanside resort. Although more dining space is needed, customers avoid this area because it is too exposed
to chilly winds and frequent rains. Also, the still air temperature is somewhat too chilly for outdoor dining during
much of the active season.

part of the enclosure surface area. Distribute the area
of glazing and the area of insulated panels to save energy
and create a pleasant environment. If practical, design
the structure so that glazing and insulated panels can be
swapped. This gives you a relatively inexpensive way
of altering the daylighting and heat gain characteristics
of the structure after it is built, if necessary. You may
even be able to exchange glazing for insulated panels,
or vice versa, on a seasonal basis.

Deal with excess heat gain efficiently.

A common mistake when adding glazed enclosures

is overlooking the large cooling loads that they may
create. If air conditioning is used to deal with the heat
gain, the energy costs can be enormous in relation to
the size of the space.

Deal with excess heat by venting it. Do this with a

combination of vent dampers at high and low positions
in the space. Locate the low vents where cold entering
air will not cause discomfort. Provide dampers that seal
tightly when venting is not required.

During warm weather, venting alone may not

suffice. In such cases, consider using reflective glazing
(see

Measure 8.1.3

) or opaque panels for part of the

enclosure. If the weather can turn cold for significant
periods, use insulating panels for as much of the
enclosure as possible.

If the space will be air conditioned, avoid any vents

at a low point in the structure, because these would waste
cooled air. If you use vents at all when air conditioning,

limit them to locations at the highest points of the
enclosure.

Even with adequate venting or with air conditioning,

direct radiation of sunlight on occupants may be
uncomfortable. This is most likely to be a problem if
the occupants are stationary, e.g., at dining tables. In
such cases, provide shade for the people.

Control condensation adequately for
the application.

Glazing has low thermal resistance, so condensation

forms if the outside temperature falls much below the
dew point temperature of the inside air. This means
that the glazing will sweat if there is any significant
source of moisture inside the enclosed space. In many
applications, sweating is transitory and causes no
trouble, as long as the structure is made of materials
that are not vulnerable to moisture.

Condensation is a major issue when enclosing moist

environments, such as swimming pools and plant
growing facilities. In such facilities, the glazing remains
wet for long periods, and you need to use special
techniques to prevent damage and unsightly conditions.
Heavy condensation has a major effect on appearance
and view. This may not matter with a swimming pool,
but it is a problem for a restaurant that uses foliage for
decor.

Swimming pools are a special challenge. The water

temperature is typically around 80°F. Because of the
large evaporating area of the water, the water temperature

1015

8.4 PASSIVE SOLAR HEATING

© D. R. Wulfinghoff 1999. All Rights Reserved.

becomes the dew-point temperature of the enclosed
space. The glazing will sweat heavily whenever the
outside temperature is much below the water
temperature. Provide effective drainage to carry
condensate away from any areas where it does not
belong, including the floor and wooden structures.

Lingering condensation grows mold. Sunlight stops

mold growth, but only on parts of the structure that are
directly illuminated. Make shaded surfaces accessible
for frequent cleaning.

Provide good daylighting.

Psychologically, people may be more sensitive to

bright sunlight when a space is enclosed, even if the
function remains the same. You may want to compensate
for this effect by using various types of diffusing and
opaque panels.

As a rule, transparent glazing provides a more

pleasing visual environment than glazing that diffuses
light. You can tint the glazing or use reflective glazing
to reduce heat gain. (At the same time, remember this
rule: if you need to treat glazing to reduce the cooling

load, there is too much glazing area. Few applications
have a view that justifies excessive glazing.) To shade
localized areas that cannot tolerate direct sunlight,
provide localized shading inside the enclosure. For
example, if you are enclosing an outdoor cafe, you could
install sun umbrellas at the tables. Figure 5 shows an
example.

ECONOMICS

SAVINGS POTENTIAL: Various widely, depending on
the application.

COST: Plain glazed enclosures start at about $15 per
square foot of horizontal space. With heating, motorized
venting, and few other accessories, the price may be
about $30 per square foot in middle sizes. Very fancy
enclosures can cost as much as several hundred dollars
per square foot, but you are paying for glamor, not energy
savings.

PAYBACK PERIOD: Many years, if you consider only
energy cost. This is usually done to achieve purposes
besides energy savings.

Kalwall Corporation

Fig. 3 Swimming pool enclosure This swimming pool at an all-year campground uses an intelligent combination of translucent
insulated panels, clear glazing, and venting. Notice that the upper portions of the roof can slide back to provide venting and
daylight.

1016

8. CONTROL AND USE OF SUNLIGHT

ENERGY EFFICIENCY MANUAL

TRAPS & TRICKS

INVESTIGATE: Spend time inside enclosures similar
to the one that you wish to create, under all weather
conditions. There is no other way to appreciate what
the end result will be like.

DETAILS, DETAILS: Work out effective methods of
ventilation, preventing glare, avoiding overheating, and
dealing with condensation. Talk to people who are in
the business of installing glass enclosures. Anticipate
changes in usage that will occur as a result of enclosing
the space, and design the enclosure to accommodate
those changes efficiently.

Vistawall Architectural Products

Fig. 4 A huge enclosed hotel courtyard This area the size
of a village center is entirely under glass. Passive heating
keeps it reasonably warm under most weather conditions, in
a climate that can become fairly cold.

WESINC

Fig. 5 Localized shading This umbrella suspended inside
a swimming pool enclosure shields people seated at the table
from direct sunlight.