indirect gain sunspace convective loop
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Building
Science3
B
BUILDING SCIENCE 3B
Lecture 4: Passive Solar Design Systems
INDIRECT GAIN, ATTACHED SUNSPACE & CONVECTIVE LOOP
Lawrence Ogunsanya
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Indirect gain (Thermal storage wall) Design
Overview The indirect transfer of solar heat into the space to be heated
from a collector that is coupled to the space by an un-insulated, conductive or convective medium (suchas thermalstorage wall or trombe wall).
A thermal storage wall is a passive solar heating system inwhich the primary thermal storage medium is placed directlybehind the glazing of the solar aperture.
The outer surface of the massive wall is painted a dark colouror coated with a selective surface to promote absorption of
solar radiation. Solar radiation absorbed on the outer surface of the wall is
converted to heat and conducted (or convected in the case ofthe water walls) to the inner surface where it is radiated to theliving space.
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Thermal storage wall/Trombe Wall
with Vents
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Thermal storage wall/Trombe Wallwith Vents
Building
Science3
B
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Thermal storage wall/Trombe Wall
Exterior Interior
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Thermal storage wall/Trombe Wall
Salt lake city, Utah, USA
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Operation of Trombe Wall
Sunlight hits the darkened mass wall and absorbed heat moves
slowly across the wall The inside surface temperature peaks 6-8 hours after the midday
outside surface peak
Operational vents allow optional controlled air circulation into
the space during the day Overhang reduces wall sun exposure during the warmer months
Vent added to outside at the top can drive warm air out in the
summer and bring cooler air from a north vent
can be used as part of a North-facing greenhouse
may be retrofitted to existing houses with water, concrete, brick
or stone construction
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Water Wall
Water walls are thermal storage walls that use containers of
water placed directly behind the aperture glazing as the thermalstorage medium.
The advantage over masonry walls is that water has a volumetric
heat capacity about twice that of high density concrete;
it is therefore possible to achieve the same heat capacityavailable in a Trombe wall while using only half the space.
The high thermal storage capacity of water walls makes them
especially appropriate in climates that have a lot of sunshine.
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Water Wall
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Thermal Storage Walls or Trombe Walls
Advantages:
Eliminates glare
Lowers temperatureswings in room
Vents allow partition of
energy into daytime and
nighttime heating Sun hits entire mass
Best for sunnier climates
Disadvantages: More expensive and less
efficient than direct gain
Wall requires speciallysized foundations andinstallations.
The wall can block view
and daylight. Occupies valuable spacein
building
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Attached Sunspace Design Overview
Sunspaces also known as green houses are spaces designed for
passive solar gain that are attached to the north side of the
building.
There are many possible configurations for a sunspace but all
of them share certain basic characteristics:
Sunlight enters the sunspace through north facing glazing that
may be vertical or inclined or a combination of the two and is
absorbed primarily on mass surfaces within the enclosure;
the mass may be masonry or water in appropriate containers
and is generally located along the north wall and in the floor.
Operable windows and circulation vents in the north wall
provide for heat transfer by thermal convection from the
sunspace to the living space.
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A sunspace may be semi-enclosed by the main structure such
that only the north facing aperture is exposed to ambient air,
or may be simply attached to the main structure along the
north wall of the sunroom, leaving the end walls exposed.
The temperature in a sunspace is not thermostatically
controlled but is generally moderate enough for humanhabitation during most of the day and appropriate for growing
plants year round.
Attached Sunspace Design Overview
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Sun spaces come in three configurations
Attached Sunspace
Building
Science3
B
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Sunspace Conceptwith mass wall added
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Attached Sunspace
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Attached Sunspace
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Attached Greenhouses or Sunspaces
Advantages: It acts as a buffer zone to
reduce heat loss from the
adjacent living spaces. The sunspace can be used
for growing house plantsand food.
Provides additional living
space. The sunspace can become
an aesthetic asset to ahouse.
Disadvantages:
Construction of sunspace with
high performance glazing can
be expensive.
Thermal performance
depends greatly on how it is
operated and used.
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Convective loop Design Overview
A convective loop system uses a flat plate solar collector to
heat air or water. The heater air or water then flows by natural
convection to directly heat a living space or to a thermal
storage area.
One of the systems has a vertically mounted collector, and the
other has the collector mounted at a tilt.
Either of these systems can be mounted on an existing wall, so
they are quite suitable for retrofit applications.
Either of these systems needs two openings into the building,
one at the top of the collector for heated air flow into thebuilding,
and one at the bottom of the collector for cool air flow from
the building into the collector.
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Some applications use a window on one floor for the upper
opening and a window on a lower floor for the bottom
opening.
Other names used for any of the convective loop systems are
isolated gain and thermosiphon system.
Convective loop Design Overview
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Convective loop
Building
Science
3B
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Convective loop
Building
Science
3B
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Advantages: It is the most thermally
efficient of all the passive
system types
It can be relatively
inexpensive to install and
construct
The homeowner has
complete control of the heat
gains and losses
Disadvantages: The TAP can be an aesthetic
liability
Convective loop only provides
heat, unlike direct gain and
sunspace which provide light
as well as heat.
The system needs periodic
cleaning and maintenance.
Not effective in denselypopulated and developed
areas
Convective loop
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Questions