A Passive House, What’s That?
A passive house is designed to use tiny amount of energy for its heating in the winter months and cooling in the summer months. To get this highly sought after designation, the building must adhere to rigorous standards that maintain a comfortable temperature and quality air.
This designation and the accompanying standards were developed in German but had their roots in the experience of North American architects in the 1970s. The oil embargo came out of nowhere and shocked some of the US and Canada’s architects into action. They saw how reliant on oil for heating the region was and looked to creating homes that used little or no energy.
The Passivhaus-Institut was founded in 1996 and through testing and some new technological developments such as heat recovery ventilation systems, we now have the Passive House exact standards. And the term ‘Passive House’ means built to these standards.
How Do Passive Houses Work?
The analogy of a thermos flask is apt. To maintain the temperature in a house, you need to build it like a thermos, insulated from the outside world. This means that windows need to be tripled glazed, superinsulation used and an integrated system used to ensure air quality.
The design of the house must avoid what’s called ‘Thermal Bridging’. This is when two materials that physically touch, transfer heat.
This phenomenon causes dramatic amounts of heat to be lost through junctions in the wall and roof/floor or through any holes in the ‘building envelope’. This building ‘envelope’ or seal is what keeps us warm. Homes built to the Passive House standard are up to 90% more energy efficient than traditional homes.
Why Do People Want Passive Houses?
Passive Houses are extremely energy efficient and minimise the cost of heating. Residents of this house in rural Kerry reported an average yearly bill of £872, which is about £5 per square meter. Due to the consistent temperature within the house, many people report that living in a passive house is far more comfortable than the yo-yoing between hot and cold that goes on in a traditional houses.
In the unlikely event that there’s a power cut, a house built to the passive house standards will maintain its temperature for an extended period. Often passive houses integrate solar energy into the building providing. One other important factor that should be mentioned, is the consistently high quality air that is ensured by the ventilation/filter system.
The quality of air can be of huge benefit to those who suffer from asthma, allergies or other respiratory problems.
How Is A Passive House Built?
These energy efficient homes are built using the same techniques and materials as a more traditional design with a few exceptions. But having said this, passive homes do have the reputation of being more expensive.
The main costs go into the design stage of the house, where the architect has to carefully balance aspects to minimise heat loss. It’s pointless to have double or triple glazing if the design of the roof doesn’t provide the necessary insulation. So the design aspect is perhaps the largest investment but due to government grants and the rising cost of energy, it is an investment that you’ll see a return on in the years ahead.
A deep energy retrofit converts an existing building into a highly energy efficient house but due to the constraints of working with the traditional building structure, it is usually more expensive.
I Want To Build a Passive House—What’s First?
If you are interested in taking the plunge the first thing to realise is that it’s much cheaper to things right from the start than to try and retrofit your home. Take a look at the builders and contractors who are members of PHAI and get the conversation started.