MIL-HDBK-1003/19
Concrete block thermal storage walls may also be introduced during the
construction of new buildings. For new construction, however, it is
advisable to take advantage of the superior performance of solid masonry
walls by filling the cores of the block in the thermal storage wall with
mortar as it is erected. This process is inexpensive and the resulting
performance increment covers the increased cost. The design procedures
developed herein are applicable to 8-inch concrete block thermal storage
walls with filled or unfilled cores.
4.1.5.3 Water wall. As the name implies, water walls are thermal
storage walls that use containers of water placed directly behind the
aperture glazings as the thermal storage 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
capacity available in a Trombe wall while using only half the space.
Furthermore, a water wall can be effective at much higher heat capacities
than a Trombe wall because natural convection within the container leads to
an nearly isothermal condition that utilizes all of the water regardless of
the wall thickness. The high thermal storage capacity of water walls makes
them especially appropriate in climates that have a lot of sunshine.
4.1.6 Sunspaces. There are many possible configurations for a sunspace
but all of them share certain basic characteristics; a representative
schematic is presented in figure 6. Sunlight enters the sunspace through
south 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. The massive elements provide
thermal storage that moderates the temperature in the enclosure and the rate
of heat delivery to the living space located behind the north wall.
Operable windows and circulation vents in the north wall provide for heat
transfer by thermal convection from the sunspace to the living space. The
north wall may be an insulated stud wall placed behind containers of water
or a masonry wall through which some of the heat in the sunspace is
delivered to the building interior by thermal conduction as occurs in a
Trombe wall. A sunspace may be semi-enclosed by the main structure such
that only the south 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 human habitation during most of the day and
appropriate for growing plants year round. Amenities are thus provided that
compensate for the somewhat higher cost of sunspaces relative to other types
of passive solar heating systems.
4.1.7 Incremental cooling load. Unfortunately, not all of the heat
delivered to the living space by a passive solar heating system is useful to
the occupants. During the winter heating season, part of the delivered
solar energy will cause the building to overheat unless ventilation is
employed to limit the indoor temperature. It is to be expected that some
overheating will occur in most passive solar buildings, but too much excess
heat is indicative of a poor design: it may be that the solar aperture is
too large or that inadequate thermal storage mass has been provided. During
the summer cooling
16
Previous Page
