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Generally passive houses require no dedicated separate Central Heating system except for a domestic hot water DHW heater or boiler. A passive house makes extensive use of its intrinsic heat from internal sources such as waste heat from electrical devices (other than dedicated heaters), and body heat from people and animals inside the building. Typically passive houses also utilise passive direct solar gain. Passive houses also routinely recapture heat from air being exhausted using Heat Recovery Ventilation (HRV) that is integral to the whole house ventilation system. The HRV may have used ground heat exchangers (Earth-to-Air Heat Exchangers) to pre-heat (or pre-cool) the HRV intake air with ducts ≈20cm diameter ( ≈40 m long at a depth of ≈1.5 m) in the soil. Passive houses built in Germany typically have a dual purpose 1500 watt resistance heating element integrated with the ventilation /HRV system. The element serves as a space heat source on very cold nights and is also used to prevent the formation of water ice in the heat exchanger when outside air temperatures are below 0 degrees Celsius. Passive houses typically employ high levels of insulation, super insulated windows and rigorous energy design focused on eliminating thermal bridges and infiltration. A wide range of Insulation materials are used to create high R-value exterior walls which are much more efficient and slow the flow of heat through the walls more than wood, natural stones or concrete. Passive houses can be constructed from dense or lightweight materials but some internal thermal mass is useful to reduce summer peak temperatures and increase winter temperatures as well as guarding against possible over-heating in spring or autumn before normal solar shading becomes effective. Some high mass insulations such as building blocks of foamglas ( Thermal Resistance 0,045 W/m&2K), aerated concrete, and hollow clay bricks (thermal resistance 0,20 W/m&2K) can be used as well as highly insulated timber construction. The minimum standard for heating consumption of a passive house is 15 kWh/m&2a in Germany. Rules of Passivhaus-Institut Darmstadt, Germany for a German "Passivhaus" :
A net Zero Energy Building (ZEB) is another term for a very similar approach to creating small buildings that use substantially less energy. ZEB research is currently being conducted by Jeff Christian and others at Oak Ridge National Labs (ORNL). Zero energy building or zero energy home seem to be phrases that are gaining popularity in the USA possibly due to the implication that the energy for a zero energy home would be free. Unfortunately this seems to have been implemented without making maxium use of passive techniques to minimise heat loss and instead relies on active techniques to make up the shortfall. EFFIENCY WITH HEATING ENERGY OF ZERO KWH/M&2A. If a house like this uses Alternative Energy like Solar Cell s, Solar Thermal Energy , Wind Energy , Biofuel or an Earth-heat Exchanger , it can be called an Energy-plus-house . Normal houses in the US need 30 times more energy for heating, cooling and hot water than other nations. With these new standards, energy consumption in U.S. households could be reduced by 97%, and overall consumption of the U.S. reduced by 30%. SEE ALSO
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