Passiv-Haus Principles

From Swikipedia

Introduction

Passivhaus is a German term meaning passive house. It basically refers to the rigorous, voluntary, Passivhaus standard for energy efficiency in buildings, which results in ultra-low energy buildings that require little energy for space heating or cooling. This concept was developed in Germany in early 1990s by Professor Wolfgang Feist with Professor Bo Adamson from Lund University, Sweden, based on well researched and proven building physics.

Brief Description

Passivhaus design seeks to eliminate the need for space heating and cooling and is based on the principle that reducing heating loss to a minimum is the most cost-effective and most robust way of achieving a low carbon building.

Key features of Passivhaus Standard Buildings:

• Super insulation: Exterior insulation of a Passivhaus building to achieve a U-value of less than 0.15 W/m2K

• Windows: Energy efficient glazing and frames should have U-values not exceeding 0.80 W/m2K

• Stringent levels of air-tightness: Air leakage through unsealed joints must be less than 0.6 air changes per hour @50 Pa (equivalent of an air permeability of less than 1m3/m2/h @50 Pa)

• Ventilation: over 80% heat recovery from ventilation exhaust air, using an air-to-air heat exchanger

• Total energy demand for space heating and cooling should be less than 15 kWh/m2/yr treated floor area

• Total primary energy use for all appliances, domestic hot water and space heating and cooling should be less than 120 kWh/m2/year

• Minimal thermal bridging should be there

• Optimization of passive solar gain

By specifying these features the design heat load is limited to the load that can be transported by the minimum required ventilation air. Thus, a Passivhaus does not need a traditional heating system or active cooling to be comfortable to live in - the small heating demand can be typically met using a compact services unit which integrates heating, hot water and ventilation in one unit (although there are a variety of alternative solutions).

While passive houses work in a temperate climate, they have not (so far) produced ideal internal conditions in a tropical climate with high levels of humidity.

References:

http://www.passivhaus.org.uk/index.jsp?id=668

http://en.wikipedia.org/wiki/Passive_house

http://www.greenbuildingstore.co.uk/page--passivhaus-design.html