Nabih Tahan has been designing buildings in various corners of the globe for 27 years- in a position, as he notes on his website, to practice, learn, evaluate and compare "how we do things" in different parts of the world. Through this experience, Nabih feels that we can all improve our systems so that we can reach our global goals of protecting our local environment and planet.“ MGB talked with Mr. Tahan about the state of his art and his multinational perspective.
How do you define a “passive house?” How would my typical day differ if I lived in a passive house, or would I only notice when it was time to pay energy bills?
Technically, a passive house is a house that meets the performance criteria as specified in the Passive House Planning Package (PHPP). This is an energy calculating tool that is used at the design stages of the project to determine how much energy the building will use. The house has to also meet the blower door test requirements.
When you live in a passive house, what you feel on a daily basis is the comfort and the improved air quality. A passive house stays at constant temperatures and does not have the ups and downs of typical homes where you need a conventional furnace, usually powered by fossil fuels, to blast either hot or cold air so that the home reaches the comfort level.
What exactly is “free heat?” How is it stored and used?
“Free heat” is heat that is gained without paying for it. For instance, heat from the sun coming in through the windows is “free heat”. In a passive house, free heat is gained through anything that uses gas and electricity. If you boil water, you pay for gas or electricity to raise the temperature of the water to make tea or coffee. At the same time, without turning on your heating system, you gain a lot of heat. The same is true for computers, refrigerators, toasters, etc. In a passive house all this free heat is recycled and reused to keep the house warm.
You’ve worked in Ireland and Austria, and on your website you note that the passive house concept is so accepted in Europe that it’s become part of the building code. Does the idea have historic roots there that pre-date the current wave of eco-awareness?
Europe does not have very much oil or natural gas. They have been trying to build energy efficiently for a while. When I arrived in Austria, they were building what was called a low energy home; now they are building passive homes. Europeans rate the energy efficiency of their homes by comparing how many kilowatt hours per square foot per year their buildings consume. It is like comparing miles per gallon for a car. In the US, most rating systems which determine how “green” a project is rely on a point system: the more “green” you are, the more points you accumulate. However, the total number of points you have do not tell you how energy efficient the building is.
Homes in Europe are required to have an energy rating so that when you buy them or rent them, you will know ahead of time how much the energy consumption of the home will be.
Speaking of Europe, on your website, you describe the European method of prefab home building and how it contributes to energy efficiency. Why do you think things are done so differently here in the United States? Would the European method translate to the US market, given a chance- and if so, what needs to happen to make that possible?
When a product is built in a factory, it usually goes through a research and development stage which will determine the performance and price of the product. A car company spends years developing new models, but once they start making the cars, the manufacturing happens under a controlled environment where the performance is guaranteed, such as 30 miles per gallon and 50,000 miles of 5 year guarantee. European houses built in factories are developed using the same method and can guarantee the energy consumption of their homes. In the United States, the method of manufacturing a home in a factory is similar to making a home on site. The advantages of product development, factory automation, etc., are not used.
Where can people find out more about passive buildings?
www.passiv.de
www.passivehouse.us
www.passivehouseca.gov
www.nabihtahanarchitect.com
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