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Passive House Concept

A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. Essentially, the house heats and cools itself, hence the term passive, thus creating eco friendly homes. The combined energy consumption of a passive house is less than the average new European home requires for household electricity and hot water alone.
The combined end energy consumed by a passive house is therefore less than a quarter of the energy consumed by the average new construction that complies with applicable national energy regulations.

Passive House Concept: 1st Principles of Design

A Passive House only needs about 10% of the energy that a traditionally built house requires. The reason, it does not need a traditional heating system or active cooling to feel comfortable for the occupier. The small heating demand can be typically met using a compact services unit which integrates heating, hot water and ventilation in one unit.

The Passive House concept can be compared to a thermos flask.

The flask has a highly insulated shell that maintains the temperature of the hot (or cold) environment inside the flask. A passive house begins with an insulated shell and when you add energy-efficient ventilation, you can maintain the temperature inside with a small amount of energy consumption. A passive house also uses the energy from your appliances (TV and computers on standby), white goods (everytime you run your dishwasher) and the body heat of the occupants, to maintain a comfortable temperature rather than relying on purchasing energy and importing it into your home to create this comfortable environment.

When designing a building, this is achieved by substantially improving the construction details for each relevant component. In particular, the strategies for achieving the Passive House standard in cool and cold climates are:

- very good insulation of the building envelope & careful execution in detail for minimal thermal bridging

- high level of airtightness of the building (n50-value ≤ 0.6/h)

- windows with very low heat loss (including frames & thermal bridges) but with high solar gains

- ventilation system for good indoor air quality with highly-efficient heat recovery

- efficient building services

- efficient electrical devices and lighting

The criteria for the Passive House standard for houses in Central Europe according to the (PHPP 2007) are:

-Space heat demand ≤ 15 kWh/m²/yr

-Heating load ≤ 10 W/m²

-Excessive temperature frequency ≤ 10% (> 25°C)

-Primary energy demand ≤ 120 kWh/m²/yr for all energy applications including electricity

These figures are verified at the design stage using the Passive House Planning Package (PHPP) and includes:

* energy calculations (incl. R or U-values)

* designing of window specifications

* designing of the indoor air quality ventilation system

* dimensioning of the heating load

* dimensioning of the cooling load

* predicting summer comfort

* dimensioning of the heating and domestic hot water (DHW) systems

* calculations of auxiliary electricity, primary energy requirements of circulation pumps etc. & the estimation of CO² emissions

* verifying calculation results for funding (e.g. KfW bank in Germany)

* Climate Data Sheet: Climate regions may be selected from over 200 locations in Europe and North America. User-defined data can also be used.

* many tools for designing of passive houses, e.g. a calculation tool to determine internal heat loads, data tables for primary energy factors

* a comprehensive handbook, not only introducing the PHPP, but also highlighting crucial topics to be considered when designing Passive House.

Pre-planning and the co-ordinated efforts of mechanical engineers and architects at the first stage of design, is essential to achieving and verifying the calculations.

While following a quality control procedure to avoid onsite problems, excellent levels of airtightness and thermal insulation can be achieved to offer energy savings of 85-90%.

The UK is fast catching up to Europe, and our professionals are gaining the skills required. With the Passive House concept as the basis of the Code for Sustainable Homes (UK national standard for sustainable design and construction of new homes) the building industry has a viable alternative to traditional building methods/products that offers greater design flexibility with the promise of extraordinary savings on heating/cooling of the building, from day one.

Reference – PassivHaus Institute, Darmstadt

Passive House Concept of High Energy Efficiency Homes

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