- Passive heating design can keep out summer sun and let in winter sun while ensuring that the building envelope keeps that heat inside in winter and allow any built up heat to escape in summer.
- Passive heating uses the energy of the sun to keep occupants comfortable without the use of mechanical systems.
direct solar gain
- Direct solar gain is the simplest and least costly way of passively heating a building with solar heat gain.
- Sunlight can heat a space through the solid walls or roofs of the envelope.
- Sunlight can enter the space through windows and heat interior surfaces as well.
avoiding
- Using thick drawn curtains with a closed cornice board or “pelmet” to seal the top.
- Using insulated internal/external roller shutters.
- Using low-E glazing can prevent heat from re-radiating out through the glass of a Trombe wall and greatly reduce the amount of heat lost.
- Applying a spectrally selective surface or low-E coating to the wall itself can also improve performance by reducing the amount of infrared energy radiated towards the glass.
adapting to day & season
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sunspaces
- Sunspaces can heat spaces both through radiation and convection.
- Sunspaces can also be used for indirect solar heat gain and generally have more glazing area than floor area.
surface colour and colour roofs
massing & orientation for heating
Some distinctions of massing and orientation for passive
heating are:
- The amount of sunlight that is optimal for daylighting is often not optimal for solar heat gain.
- Since the sun's heat does not come from all directions like the sun's light can, walls facing away from the sun's path get no heat gain, even though they can still get large amounts of diffuse light.
- The sun's heat can be stored by thermal mass, which the sun's light cannot. This can be useful for west-facing walls to store heat for the night.
massing strategies for passive heating
In cold climates, massing that minimizes the ratio of surface
area to volume (approaching a cube or hemisphere) can avoid unwanted heat
loss. The sun's heat is advantageous,
though, and more surface area facing it can help passively heat the
building. The side of the building
exposed to the sun's path can be
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increased while reducing the exposed areas of the other sides of the building.
In hot climates, thin buildings with their biggest face exposed to the sun can cause unwanted solar heat gain. Shading devices and good windows can be used to reduce this while still allowing natural ventilation. Taller buildings can also reduce unwanted gains in hot climates, as the sun's heat strikes more strongly on roofs than on walls in warm latitudes, and tall buildings have less roof area per unit volume.
It’s important to remember that the sun's heat does not come from all directions like the sun's light can. Walls facing the sun's path get the most light and the most heat. Windows facing away from the sun's path can still get large amounts of diffuse light, but without heat gain (and can have excessive heat loss). Windows facing east are warmed in the morning when it is often welcome to break the chill of night, but windows facing west are heated in the afternoon when spaces are generally already warm.
In hot climates, thin buildings with their biggest face exposed to the sun can cause unwanted solar heat gain. Shading devices and good windows can be used to reduce this while still allowing natural ventilation. Taller buildings can also reduce unwanted gains in hot climates, as the sun's heat strikes more strongly on roofs than on walls in warm latitudes, and tall buildings have less roof area per unit volume.
It’s important to remember that the sun's heat does not come from all directions like the sun's light can. Walls facing the sun's path get the most light and the most heat. Windows facing away from the sun's path can still get large amounts of diffuse light, but without heat gain (and can have excessive heat loss). Windows facing east are warmed in the morning when it is often welcome to break the chill of night, but windows facing west are heated in the afternoon when spaces are generally already warm.
orientation strategies for passive heating
Buildings that are longer than they are wide should usually
be oriented east-west rather than north-south.
This orientation lets you consistently harness thermal gain, or
consistently avoid it, along the long face of the building. It also lets you minimize the area that’s
subject to faster energy swings from the rising or setting sun. Solar heat gain on the east side can be
acceptable or even useful, because it happens in the morning after the cooler
night; but solar heat gain on the west side is rarely desirable at the end of
an already warm day.
Before determining the materials for the façade, it’s important to understand the patterns of solar radiation that affect the building. The following image shows solar incident radiation throughout the day and throughout the year on the five exposed faces of a cube-shaped building. The vertical axis shows times of day while the horizontal axis shows times of year, and the colour shows the amount of incident heat.
Before determining the materials for the façade, it’s important to understand the patterns of solar radiation that affect the building. The following image shows solar incident radiation throughout the day and throughout the year on the five exposed faces of a cube-shaped building. The vertical axis shows times of day while the horizontal axis shows times of year, and the colour shows the amount of incident heat.
material choices for orientation
thermal conductivity with thermal mass
- Insulation can be extremely valuable in preventing direct gain from being conducted to the ground or outside air where it is lost.
- Thermal lag from mass can greatly reduce the need for insulation in the building envelope, especially in climates with large temperature swings from day to night.
- Combining thermal mass with insulation can avoid such unwanted temperature swings indoors while still allowing solar heat gain or radiative cooling.
rules of thumb for designing with thermal mass
- Choosing the right amount of mass.
- Large surface areas of thermal mass with sufficient solar exposure.
- In direct gain storage, thin mass is more effective than thick mass.
- Insulating the thermal storage from exterior climate conditions, so that they do not add or remove too much heat.
- It is important to locate as much thermal mass in direct sunlight (heated by radiation) as possible.
- Locating thermal mass in interior partitions is more effective than external walls.
- The most effective internal storage wall masses are those located between two direct gain spaces.
- Thermal mass can be combined with glazing to form "Trombe walls".
trombe wall and attached sunspace
- A successful Trombe wall or attached sunspace optimizes heat gain and minimizes heat loss during cold times, and avoids excess heat gain in hot times.
- The glass prevents the escape of radiant heat from the warm surface of the storage wall.
- You can also configure Trombe walls to heat air within the internal space.
shading for solar heat gain
- Shades can keep the heat and glare of direct sun from coming through windows.
- Shades can also keep direct sunlight off of walls or roofs, to reduce cooling loads.
avoiding losses
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