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Development of a novel passive top down

South-facing glass in the northern hemisphere north-facing in the southern hemisphere admits solar energy into the building interior where it directly heats radiant energy absorption or indirectly heats through convection thermal mass in the building such as concrete or masonry floors and walls. The floors and walls acting as thermal mass are incorporated as functional parts of the building and temper the intensity of heating during the day.

At night, the heated thermal mass radiates heat into the indoor space. It has little added thermal mass beyond what is already in the building i. Additional south-facing glazing can be included only if more thermal mass is added. Energy savings are modest with this system, and sun tempering is very low cost.

Overheating of the building interior can result with insufficient or poorly designed thermal mass. About one-half to two-thirds of the interior surface area of the floors, walls and ceilings must be constructed of thermal storage materials.

Thermal storage materials can be concrete, adobe, brick, and water. Thermal mass in floors and walls should be kept as bare as is functionally and aesthetically possible; thermal mass needs to be exposed to direct sunlight.

Wall-to-wall carpeting, large throw rugs, expansive furniture, and large wall hangings should be avoided. The simplest rule of thumb is that thermal mass area should have an area of 5 to 10 times the surface area of the direct-gain collector glass area. Thermal masses with large exposed areas and those in direct sunlight for at least part of the day 2 hour minimum perform best. Medium-to-dark, development of a novel passive top down with high absorptivity, should be used on surfaces of thermal mass elements that will be in direct sunlight.

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Thermal mass that is not in contact with sunlight can be any color. Covering the glazing with tight-fitting, moveable insulation panels during dark, cloudy periods and nighttime hours will greatly enhance performance of a direct-gain system.

Water contained within plastic or metal containment and placed in direct sunlight heats more rapidly and more evenly than solid mass due to natural convection heat transfer.

The convection process also prevents surface temperatures from becoming too extreme as they sometimes do when dark colored solid mass surfaces receive direct sunlight. This should be based on the net glass or glazing area.

Above this level, problems with overheating, glare and fading of fabrics are likely. There are two types of indirect gain systems: The wall can be constructed of cast-in-place concrete, brick, adobe, stone, or solid or filled concrete masonry development of a novel passive top down. This hot air can be introduced into interior spaces behind the wall by incorporating heat-distributing vents at the top of the wall. This wall system was first envisioned and patented in 1881 by its inventor, Edward Morse.

Felix Trombe, for whom this system is sometimes named, was a French engineer who built several homes using this design in the French Pyrenees in the 1960s. The surface of the thermal mass absorbs the solar radiation that strikes it and stores it for nighttime use. Unlike a direct gain system, the thermal storage wall system provides passive solar heating without excessive window area and glare in interior spaces. However, the ability to take advantage of views and daylighting are eliminated.

The performance of Trombe walls is diminished if the wall interior is not open to the interior spaces. Furniture, bookshelves and wall cabinets installed on the interior surface of the wall will reduce its performance. A classical Trombe wall, also generically called a vented thermal storage wall, has operable vents near the ceiling and floor levels of the mass wall that allow indoor air to flow through them by natural convection.

As solar radiation heats the air trapped between the glass and wall and it begins to rise. Air is drawn into the lower vent, then into the space between the glass and wall to get heated by solar radiation, increasing its temperature and causing it to rise, and then exit through the top ceiling vent back into the indoor space. If vents are left open at night or on cloudy daysa reversal of convective airflow will occur, wasting heat by dissipating it outdoors.

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Vents must be closed at night so radiant heat from the interior surface of the storage wall heats the indoor space. Generally, vents are also closed during summer months when heat gain is not needed. During the summer, an exterior exhaust vent installed at the top of the wall can be opened to vent to the outside. Such venting makes the system act as a solar chimney driving air through the building during the day. Vented thermal storage walls vented to the interior have proven somewhat ineffective, mostly because they deliver too much heat during the day in mild weather and during summer months; they simply overheat and create comfort issues.

Most solar experts recommended that thermal storage walls should not be vented to the interior. There are many variations of the Trombe wall system.

An unvented thermal storage wall technically not a Trombe wall captures solar energy on the exterior surface, heats up, and conducts heat to the interior surface, where it radiates from the interior wall surface to the indoor space later in the day.

A water wall uses a type of thermal mass that consists of tanks or tubes of water used as thermal mass. A typical unvented thermal storage wall consists of a south facing masonry or concrete wall with a dark, heat-absorbing material on the exterior surface and faced with a single or double layer of glass. High transmission glass maximizes solar gains to the mass wall.

Glass framing is typically metal e. Heat from sunlight passing through the glass is absorbed by the dark surface, stored in the wall, and conducted slowly inward through the masonry.

As an architectural detail, patterned glass can limit the exterior visibility of the wall without sacrificing solar transmissivity. A water wall uses containers of water for thermal mass instead of a solid mass wall. Water walls are typically slightly more efficient than solid mass walls because they absorb heat more efficiently due to the development of convective currents in the liquid water as it is heated.

These currents cause rapid mixing and quicker transfer of heat into the building than can be provided by the solid mass walls. Temperature variations between the exterior and interior wall surfaces drive heat through the mass development of a novel passive top down.

  • Vented thermal storage walls vented to the interior have proven somewhat ineffective, mostly because they deliver too much heat during the day in mild weather and during summer months; they simply overheat and create comfort issues;
  • Vented thermal storage walls vented to the interior have proven somewhat ineffective, mostly because they deliver too much heat during the day in mild weather and during summer months; they simply overheat and create comfort issues.

Inside the building, however, daytime heat gain is delayed, only becoming available at development of a novel passive top down interior surface of the thermal mass during the evening when it is needed because the sun has set. Time lag is contingent upon the type of material used in the wall and the wall thickness; a greater thickness yields a greater time lag. The time lag characteristic of thermal mass, combined with dampening of temperature fluctuations, allows the use of varying daytime solar energy as a more uniform night-time heat source.

Windows can be placed in the wall for natural lighting or aesthetic reasons, but this tends to lower the efficiency somewhat. These thicknesses delay movement of heat such that indoor surface temperatures peak during late evening hours. Heat will take about 8 to 10 hours to reach the interior of the building heat travels through a concrete wall at rate of about one inch per hour.

A good thermal connection between the inside wall finishes e. Although the position of a thermal storage wall minimizes daytime overheating of the indoor space, a well-insulated building should be limited to approximately 0. A water wall should have about 0. Thermal mass walls are best-suited to sunny winter climates that have high diurnal day-night temperature swings e. They do not perform as well in cloudy or extremely cold climates or in climates where there is not a large diurnal temperature swing.

  • The simplest rule of thumb is that thermal mass area should have an area of 5 to 10 times the surface area of the direct-gain collector glass area;
  • Using information on a Color for electromagnetic radiation to determine its thermal radiation properties of reflection or absorption can assist the choices;
  • To counteract this, you usually must increase the thickness of the glazing or increase the number of structural supports to hold the glazing.

Nighttime thermal losses through the thermal mass of the wall can still be significant in cloudy and cold climates; the wall loses stored heat in less than a day, and then leak heat, which dramatically raises backup heating requirements. Covering the glazing with tight-fitting, moveable insulation panels during lengthy cloudy periods and nighttime hours will enhance performance of a thermal storage system. The main drawback of thermal storage walls is their heat loss to the outside.

Double glass glass or any of the plastics is necessary for reducing heat loss in most climates. In mild climates, single glass is acceptable. A selective surface consists of a sheet of metal foil glued to the outside surface of the wall.

It absorbs almost all the radiation in the visible portion of the solar spectrum and emits very little in the infrared range. High absorbency turns the light into heat at the wall's surface, and low emittance prevents the heat from radiating back towards the glass. Water is stored in large plastic bags or fiberglass containers to maximize radiant emissions and minimize evaporation. It can be left unglazed or can be covered by glazing.

Solar radiation heats the water, which acts as a thermal storage medium. At night or during cloudy weather, the containers can be covered with insulating panels. The indoor space below the roof pond is heated by thermal energy emitted by the roof pond storage above. With the angles of incidence of sunlight during the day, roof ponds are only effective for heating at lower and mid-latitudes, in hot to temperate climates.

Roof pond systems perform better for cooling in hot, low humidity climates. Not many solar roofs have been built, and there is limited information on the design, cost, performance, and construction details of thermal storage roofs. It functions like an attached greenhouse that makes use of a combination of direct-gain and indirect-gain system characteristics. A sunspace may be called and appear like a greenhouse, but a greenhouse is designed to grow plants whereas a sunspace is designed to provide heat and aesthetics development of a novel passive top down a building.

  • Sunspaces are very popular passive design elements because they expand the living areas of a building and offer a room to grow plants and other vegetation;
  • Home automation systems that monitor temperature, sunlight, time of day, and room occupancy can precisely control motorized window-shading-and-insulation devices.

Sunspaces are very popular passive design elements because they expand the living areas of a building and offer a room to grow plants and other vegetation. In moderate and cold climates, however, supplemental space heating is required to keep plants from freezing during extremely cold weather.

The simplest sunspace design is to install vertical windows with no overhead glazing.

Passive solar building design

Sunspaces may experience high heat gain and high heat loss through their abundance of glazing. Although horizontal and sloped glazing collects more heat in the winter, it is minimized to prevent overheating during summer months.

Although overhead glazing can be aesthetically pleasing, an insulated roof provides better thermal performance.

Skylights can be used to provide some daylighting potential. Vertical glazing can maximize gain in winter, when the angle of the sun is low, and yield less heat gain during the summer. Vertical glass is less expensive, easier to install and insulate, and not as prone to leaking, fogging, breaking, and other glass failures.

A combination of vertical glazing and some sloped glazing is acceptable if summer shading is provided. A well-designed overhang may be all that is necessary to shade the glazing in the summer. The temperature variations caused by the heat losses and gains can be moderated by thermal mass and low-emissivity windows. Thermal mass can include a masonry floor, a masonry wall bordering the house, or water containers.

Distribution of heat to the building can be accomplished through ceiling and floor level vents, windows, doors, or fans.

In a common design, thermal mass wall situated on the back of the sunspace adjacent to the living space will function like an indirect-gain thermal mass wall. Solar heat is conveyed into the building by conduction through the shared mass wall in the rear of the sunspace and by vents like an unvented thermal storage wall or through openings in the wall that permit airflow from the sunspace to the indoor space by convection like a vented thermal storage wall.

In cold climates, double glazing should be used to reduce conductive development of a novel passive top down through the glass to the outside. Night-time heat loss, although significant during winter months, is not as essential in the sunspace as with direct gain systems since the sunspace can be closed off from the rest of the building.