Due to the popularity of solar energy, a lot of innovations have come forth to deal with nearly every housing or building problem.
The passive solar design, for instance, is practiced throughout the world and has been shown to produce buildings with reduced maintenance, low energy costs, and superior comfort.
Passive solar design talks about the use of energy from the sun for the cooling and heating of living spaces. With such an approach, the building or some element of it takes advantage of the natural energy characteristics in materials and the air that is created by the exposure of the sun.
Passive systems are simple and have few moving parts like solar panels Cape Town. They also require no mechanical systems and minimal maintenance.
So, how do you design greenhouse heating with the passive solar design to provide a cozy winter space, overcome poor growing conditions and extend the growing season?
Here are 5 tips for designing one:
Site selection is key. Basically, a passive solar greenhouse is a solar collector that is collecting solar energy for photosynthesis and heat.
You might think that in order to capture the maximum amount of solar energy, it should be oriented straight in a southern direction. However, the ideal orientation should be -15 degrees south-east in the Northern Hemisphere.
This gives the greenhouse the early morning sun when the building is at its coldest and reject the sun toward the end of the day when it is more prone to overheat.
Having said that, in case you have limited options, you can orient your greenhouse up to 45 degrees south and you will still achieve decent results.
Additionally, it is important that you choose a site that provides your greenhouse with good access to the sun year round. Also, make sure that the site does not have excess shading from other buildings and trees. With greenhouses, you want all the sun you can get.
The glazing surface in the South part is the collection unit. This is the area that allows the sun to heat up the space and lets your plants to grow. However, it is also the weakest link in the entire assembly.
There is a not-so-good relationship between the R-value (thermal resistance) and transmissivity (how much light comes through). As your R-value goes up, it means that less heat is lost. Should the transmissivity drop, less light can get through.
If the transmissivity drops below 70 percent, plants do not get enough light. They get a bit “leggy” and might never reach their full growth potential or just die.
In general, you should choose poly-carbonate or you can get a double wall poly that is greenhouse-grade and comes at a fraction of the cost.
When deciding on the glazing material, you should choose one with the highest R-value glazing and a transmissivity of 70 percent or higher. Also, make sure that the glazing is able to withstand the snow load in your region.
In cold climates, insulation is of utmost importance. It is the element that makes the biggest difference in the thermal performance of your greenhouse. Which is why you should consider using R20 wall all around.
Also, the R-value you choose will depend on how many seasons you want to grow, how you plan on heating the space and how cold your environment gets.
I believe that there is no upper limit in terms of ventilating a greenhouse. I recommend that you install a ventilation area that is equivalent to at least 30 percent of your glazing.
But, take note that this should only keep things cool in the shoulder months. In order to get a sufficient amount of air through the greenhouse, it is vital that you have other ways to increase ventilation and keep the temperature below 26 degrees Celsius durinig other seasons.
Thermal mass is crucial in any passive solar building and is important if you wish to extend seasons. It helps keep the building warm at night during winter and keep to cool during the summer.
Water is typically used, however, it can freeze and make a mess. Instead try various thermal mass options such as metal, water + glycol, cob, concrete, rock, and basically any cheap materials that store heat— you do not have to worry about these during the winter.