Whilst a little late in the day for our barn (it was built 100+ years ago) the orientation of a building to the sun and the suns relationship with the buildings windows, doors and other openings are the focus of passive solar design.
Through effective passive solar design we seek to harness the power of the sun to our advantage whilst protecting inhabitants from its excesses.
So what do we need to consider in our design:
- The strength of the sun at different times of the year. This will be determined by the latitude, altitude and azimuth of the site, with these factors being tempered by shading of the building and weather conditions.
- Ways in which we can maximise the use of the sun in providing heating for the building whilst avoiding over exposure of the interior and inhabitants to solar radiation.
- What technology and techniques will we need to control and manage heat gain, storage and release and then provide ventilation and system reset.
The basic structure of a passive solar heating system is:
Solar radiation enters the the building via glazed windows, it is absorbed by the thermal mass of the building – its masonry walls and floors. Once stored within the thermal mass of the structure technology is employed to ensure that the heat is retained (through good insulation of the envelop of the building) and utilised in an effective and targeted manner (through well designed radiation, convection and conduction paths and optionally energy consuming methods such as fans and air blowers).
A direct gain system is one where the main means of thermal gain is through direct heating of the thermal mass by solar radiation entering the building through windows and being absorbed by the thermal mass. An indirect gain system is one where solar radiation is captured and stored in a component of the building that has a high thermal mass and from there released to areas within the building that require heating.