Passive House Construction
When you step into an ancient home, you feel fresh cool air all over. Have you ever wondered, how can such houses be so cool without air conditioning? The people in those days focused on building houses that adapt to the surrounding climate. For example, in warmer climatic regions they made stepwells and enclosed ponds adjacent to the the main building. The evaporating water from them cooled the surrounding air, making the building interiors pleasant. And many such time tested techniques form the backbone of passive house construction.
Yes, passive house construction incorporates every measure to build a house that efficiently adjusts to the prevailing climate; thus giving you extremely comfortable modern homes. And that too without leaving an environmental impact during and after construction.
Sounds interesting? Read on to understand all about passive house construction.
What is Passive House Construction?
Passive House Construction is an energy efficient methodology of constructing a home that is highly comfortable for the occupants. Also at the same time, it efficiently manages the energy requirements of the house. This means bringing down the heating and cooling loads of homes through passive measures. It includes, using natural energy sources (like sun or wind), using energy efficient appliances, providing flawless insulation etc.
But why passive homes?
A conventional home operates differently with changing seasons. For example monsoons and winters require room heaters to prevent dampness, molds and stinky air. If not, it may turn to be a perfect place for allergy breakouts putting occupants health at risk.
On the other hand scorching summers demand air conditioning 24×7. And impact of running air conditioning equipment for longer period translates to higher monthly bills. All the more, they result in environmental heat build up and ozone layer depletion adding to global warming.
Effectively, passive construction is a long term solution to offer a home that is comfortable throughout the year – without environmental and health risks, and no fear of high electricity bills too!
To achieve that, passive house uses specific design and follows building standards to reduce wastage. Major factors involved in a passive house construction are:
- Energy Savings Measures
- Mechanical Ventilation
- House Cooling Measures
- Proper insulation
- Water Saving Measures
- Sustainable Building Materials
Energy Savings Measures
As a first step to save energy, the thermal load of the house is calculated. This includes exterior load from climate as well as interior loads from people and appliances. Depending upon the thermal load, engineers suggest a combination of one or more of the following passive energy saving measures.
- Orientation – Adjusting the layout of the house can optimise the sunlight penetration and heat build up in the house during day time. For this the solar path is studied and a perfect orientation is proposed.
- Solar Shading – Usage of protruding structures called overhangs or solar shading to block undesired sun’s heat.
- Earth Berm – Earth berm or earth sheltering uses earth walls to maintain the temperature inside the house.
Furthermore, as mentioned earlier, passive house installs energy efficient appliances to bring down the overall energy requirement of the house.
Secondly, a passive house use mechanical ventilation system to maintain the quality of fresh air inside the house. The stale air from the house is expelled and the indoors are replenished with the filtered fresh air from outside.
A wind tower or a windcatcher is an example of a physical structure that was used in traditional Persian architecture to provide passive ventilation in the building.
The purpose of this tower is to direct cooler breeze from higher altitudes above the ground into the interior of the buildings. The higher the tower, the more efficient the cooling is. This method is very popular in the Middle East and is even used for buildings which are no more than two stories high.
House Cooling Measures
As said earlier, the mechanical ventilation in a passive house transfers heat from the home to natural energy sinks like air, water or earth. Also, proper shadings for windows help reduce the heat penetration from scorching sun.
You can maintain rooms at a temperature of 29-30 degrees by cooling the fresh air input. Evaporative cooling is a passive method. Here the outside air is cooled by evaporating water before it enters the building.
All of these reduce the capacity and the period for which the air conditioning equipment is normally required. The best thing about passive homes are that the indoor temperature remains the same immaterial of the temperature outside.
Insulation plays an important role in preventing unwanted heat transfer to and from the house, through the roof, floor and walls. A passive house achieves an airtight construction by sealing all the seams, electrical and plumbing fixtures with insulation materials.
Also a completely insulated building envelope is created by making walls with r value greater than 30 and ceilings with r value greater than 50. (r value is a measurement of resistance to heat flow, higher the r value higher the insulation it offers). Furthermore, usage of certified triple pane for windows and doors gives the house an airtight thermal envelope.
In a nutshell, passive house brings down heating and cooling loads in a house. At the same time provide fresh and warm air, thus imparting a healthy living condition.
Water Saving Measures
Just like air, water also has utmost importance in a passive house. Water is saved for future use and reused as many times as possible. For example, collection and recycling of rainwater is wherever possible. Also, grey water is recycled and fed to toilet flushes and used for watering the garden.
Read more: Rainwater harvesting
Sustainable Building Materials
Passive house uses sustainable construction materials like steel. Here, it is a practice to opt for eco friendly building materials that are easily available and processed locally. For example, wood comes in a wide variety and is easily available everywhere. Local workshops can churn out the wood to make timber for construction. This saves money as well as time.
Read more: Steel structures in constructions
To make a fair comparison with existing construction methods let us see the pros and cons of passive house construction.
Pros and Cons of Passive House Construction
The benefits of passive house are:
- Less monthly electricity bills
- Lower energy consumption
- Low carbon emissions
- Controlled indoor humidity
- One constant temperature throughout the year (29-30 degrees)
- Putting it altogether, healthy indoors translates to wellness of whole family
It is true that the benefits of passive houses are many, but there are a few areas where it needs to improve. And they are:
- The design of the house is very much dependent on location and prevailing weather. So it takes immense time to come up with the design after considering all factors.
- And longer designing time translates to high design cost as well.
- It is relatively new and the cost of passive building materials are on the higher side. Altogether, building a passive home is an expensive affair.
- For the occupants, the concept is new and there is a learning curve.
- The insulation layer may get displaced creating heat pockets. This results in uneven air distribution (called as Thermal bridging). To avoid this you need experts to carry out insulation.
The shortcomings are negligible in comparison to the benefits a passive house offers. Having said so, it is of no doubt that passive construction method is the next big thing in construction sector all over the world. And India is no different!
Passive House Construction in India
The German speaking countries and Scandinavia hold the credit of owning majority of the passive homes in the world. Passive house construction is slowly picking up in India also. Indira Paryavaran Bhavan (Office of Ministry of Environment and Forests) is a good example of passive solar design along with energy efficient building materials.
India is a land of varied landscape and diverse climate. Depending on the climatic conditions in different regions, various passive construction methods are adopted. But the passive home characteristics like the windows and insulation remain the same throughout the subcontinent.
Implementation of Passive House Construction in Kerala
With the lookout for heat reduction in homes, passive homes are picking up demand in Kerala. Climate of Kerala is warm and humid, as well as there is abundance of water and sunlight. Accordingly, the passive designs adopted in Kerala focuses on utilising natural light, sustaining vegetation, controlling humidity and reducing heat gain. Some of the popular passive construction methods implemented in Kerala are:
- Customized sun control and shading devices without affecting natural lighting. This reduce heat build up during the day and brings down the cooling requirement.
- Kerala’s tropical climate needs dehumidification to cool the homes. A growing living green roof for the house can be a great addition to provide cooling in summer. Such roofs can reduce rainwater runoff and also form a natural habitat for various birds and animals.
- Another way to reduce heat is by using locally available materials like terracotta tiles, hay and inverted-earthen pots to provide solar shading.
- Solar chimneys along with an evaporation cooling device can make the days comfortable.
And to make it financially attractive, green projects are eligible for cheaper loans. State Bank of India charges lower interest rates for first three years for building projects that reduce carbon emission and promotes renewable energy.
A house that use very little energy, especially for heating and cooling. And, of course at the same time gives a high level of comfort and fresh clean air for living! That is what a passive house do!
For more details on passive house construction in Kerala, contact Team Viya!