A Solar Home

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Rajesh Thakkar

It all started about 20 years ago when climate change and renewable energy were still not popular and surely not glamorous. My curiosity to understand evolution, patterns and design in nature led to a growing exploration of its various processes. From mimicking evolution to creating artificial life, to capturing energy the way plants do, each experiment added to what was still just scientific curiosity. These meanderings one day led to a completely new dimension, that of architecture. This happened in a beautiful dense forest in Pennsylvania. With the sound of gushing water beneath it, the ‘Falling Water’ monument talked about being in harmony and being one with Nature.Building a home that is solar powered and constructed with local low-energy materials works out well in the long term, both in terms of costs as well as renewability

The chance to be one with Nature came finally in 2004, when there was an opportunity to build a home for my family where I could put all those theories, explorations and dreams to practice. By then, creating a home using excessive concrete, steel and brick was to me, akin to violence against nature and self. Its harshness would create an unhealthy and unharmonious dwelling designed to separate, rather than bring together the outside and the inside. Thus, the home was based on the following four principles –

1. Low energy construction techniques – no kiln-fired bricks, very minimal use of steel and cement, no external chemical paints, using mud plastering instead of cement plastering, etc

2. Passive Solar design for maximum hours of natural light indoors, natural insulation through selection of materials for walls, roofs and positioning of windows/doors so as to eliminate the need for air conditioning

3. Active Solar design for generating electricity and hot water that would enable 24x7x365 days of independence from grid power

4. Rainwater Harvesting by collecting every drop of water that falls on the building structure and storing and using the same for cleaning, plants and growing food in a vegetable garden

These are by no means newly discovered ideas. In fact, for millennia man has built dwellings and other structures based on these principles, which focus on use of local materials and design for local environmental conditions.

Low Energy Construction Techniques:

The concept of low energy construction techniques is about minimizing the use of all of those materials and processes that are energy-intensive. This has multiple advantages - not only would the result be far more environmentally friendly but it would also be cheaper, aesthetically pleasing and weather-friendly. It is important to question and look for alternatives for each material and every process including bricks, tiles, steel, cement, paint, glass, etc. The ordinary Red Brick commonly used in construction is manufactured using a highly energy-intensive process of baking. Often, they are baked using coal or oil and sometimes, even wood, which not only burns natural resources but are also highly polluting. Instead of following what most architects and contractors would recommend, I looked for low energy alternatives and found multiple options such as compressed mud blocks, earth bags and bamboo.It is important to question and look for alternatives for each material and every process including bricks, tiles, steel, cement, glass, etc.

Similarly, materials such as the steel and cement extensively used in modern construction methods are energy intensive and wasteful. While it might be difficult to eliminate their use, it is possible to reduce the quantity of these environmentally damaging materials significantly. Usually these are used in the construction of columns and beams – and these can be eliminated by building load-bearing structures. Another area where these are used is in ceilings and roofs. We adopted a technique called ‘hollow roofs’ in which we used ordinary roof tiles as a filler material thus reducing the density of steel and cement required. These techniques have been scientifically proven strong and very reliable.

The picture shows the use of compressed mud blocks and hollow roof, which looks like any other roof but uses less than half the usual amount of cement and steel. These exterior walls are painted using a homemade mix of sieved mud and a very small quantity of Fevicol and Tar to make it sticky and waterproof. This gave the mud blocks the required protection from rain while largely avoiding chemical paints.

Passive Solar Design

Passive Solar design is the lesser understood and used technique. It takes into account the seasonal direction and intensity of the Sun at a given location while designing and selecting materials. Living in a tropical country means the summers are very hot and so heat insulation was crucial to eliminating the need for air conditioning.

Interestingly, the low energy and low cost materials discussed above are not only environment-friendly but these alternative materials and techniques like compressed mud blocks or local granite stone and hollow roofs act as a thermal mass which provides excellent insulation from the heat in the summer and cold in the winter. In these latitudes, summer sun is very hot from the south and south-west directions. So the positioning of windows/doors and the length of their shades or overhangs were designed keeping in mind the direction of the summer sun.

On the south and south-west sides of the house, I decided to reduce the number of windows and doors and provided extended shades, which keep the house cooler during summer. The east side of the house, as seen in the picture below, has large windows which provide ample natural light throughout the day thus eliminating the use of power for lighting during the daytime.

Active Solar Design

Active Solar design is about generating power using photovoltaic cells and heating using panels. In recent years the technology and demand has improved significantly making these systems very viable. It is possible to generate significant amounts of power from a relatively small surface area and typical systems consist of power-generating panels that charge the batteries. The power from batteries can be used for providing electricity for lights and other appliances directly or through an inverter.

The Solar power system for my home, as shown in the picture, generates 1.8KW of power and is designed to run all the appliances in the house (lights, TV, washing machine, fridge, microwave, etc) without the need for external power sources. This kind of system requires detailed analysis of consumption patterns and a design that would meet all the requirements through the various seasons of the year. During the monsoons, the sky is often cloudy for multiple days at a stretch, which is taken into consideration while designing the system capacity. The hot water requirements for the entire family are met using solar heating panels that generate enough hot water for at least 11 months of the year.

Rainwater Harvesting:

Collecting rainwater that falls on the building structure and storing it for household use is a key aspect of sustainable design. As seen in the picture below, the building structure was designed with pre-built water collection channels, which collect water from the sloped and flat roof areas of the building. This water is stored in an 8000-litre underground sump and used for growing organic vegetables behind the house and for washing the car and watering the garden plants.

Cost savings & Return on Investment:

These techniques can be divided into those that provide immediate returns in terms of cost savings and those that provide long-term return on investment.

For instance, the use of local low energy materials such as compressed blocks and techniques such as hollow roofs resulted in an estimated 30-40% savings in construction cost compared to a typical home.

The savings from passive solar design are in the form of lower electricity bills due to excellent natural lighting and eliminating the need for air conditioning. Looking at active solar design, the hot water system is extremely cost effective as you can recover the cost of the unit in 3-5years through savings in electricity bill and state subsidies after which the hot water comes for free. Solar electricity generation systems 5 years ago were very expensive due to the high cost of Solar Photovoltaic panels (Rs. 200 per watt) which made them economically unviable. Today, the prices have dropped by 50% thus making these systems much more viable if designed appropriately.The concept of low-energy construction techniques is about minimizing the use of all of those materials and processes that are energy-intensive.

In certain locations, the cost can be further brought down by designing a hybrid Wind-Solar system. Finally, I live in a community where water is charged at Rs. 12 per kilolitre. The rainwater harvesting system has saved me thousands of rupees in water charges over the years and will continue to do so for the life of the house with minimal maintenance requirements.

The Path Ahead

It is almost 5 years since the construction of my home, and many of the ideas that went into it have worked very well and some have fallen short. Since then, I have also learnt many newer techniques related to construction materials, methods and groundwater recharging.

Looking at the perilous state of our groundwater resources today, my rainwater harvesting system should have been more than just storing water for personal use. I am working with the community towards implementing a rainwater-harvesting scheme on a large scale, which will build more than 150 recharge wells leading to a significant impact on the groundwater level for the entire area.


Lately I have also started the construction of a house on a farm using earth bags. This amazingly simple technique when combined with some contemporary ideas can be revolutionary in terms of cost, aesthetics and almost zero environmental impact, thus moving closer to the ultimate goal of creating a dwelling that supports truly sustainable living.