27
Mar
Passive house is recognised as the ultimate standard in energy-efficient house construction. One which we should all aspire to, but what is it? How easy is it to achieve? And what are the cost and practical implications?
A Passivhaus or passive house, provides a high level of internal comfort while using very little energy for heating and cooling the home. A passive house is built with particular attention to the detail, the design and the construction according to principles developed by the Passivhaus Institute in Germany. The house is certified through an exacting quality assurance process.
A passive house maintains comfortable temperatures, whatever the weather. Optimal building positioning, shading and detailed modelling ensures the house is cool in even the hottest summers. With the house being comfortably warm in the winter, whilst using very little energy for heating, as a result of high-quality triple glazed windows and walls. Meaning there is no draughts, no cold spots and no condensation. Internorm is the number 1 Passivhaus window manufacture in Europe, with 9 passive house certified components.
The energy needed to heat a building is quantified by kilowatt hours (kWh) used per square metre of useful floor area per year. Kilowatt hours per m² varies from building to building depending on how well insulated they are, how efficient the heating system is, and how the residents use the building. People living in an average UK house might use around 140kWh/m²/yr for space heating. In a passive house, a target of 15kWh/m²/yr is set as a maximum energy demand for space heating. This is achieved by reducing the heat lost from the building to a minimum. The target of 15kWh/m²/yr is used because this is the level of performance that is most cost-effective over the lifetime of the building. Much below this figure pushes costs above a level where the benefits pay for themselves.
While there is evidence that the energy performance of new homes don’t match their design claims, the Passivhaus quality assurance process ensures that what is designed is what gets built. The actual energy performance is, on average, exactly as predicted by the design stage modelling using PHPP (Passivhaus Planning Package). Passivhaus buildings do not suffer from a performance gap as standard new builds.
Obviously a quality build usually attracts a premium but not necessarily. Passivhaus can be achieved with modest builds, costing much the same as a standard home. Taking into account the savings of around 90% on energy bills which can be achieved without the need for any expensive eco-products, the investment is clearly justified. There is no need for underfloor heating, and a wood burning stove would be mainly be for show. The super-efficient ventilation system is also affordable to run, and the quality of the build ensure minimum maintenance costs.
Passive houses come in all shapes and sizes and can be built to almost any budget. But attention to details is paramount, and great care needs to be taken in the actual construction, with a rigorous quality control process. A passive house can be built using different materials, such as timber and masonry and in a range of styles from period to contemporary, to suit individual preferences and the location.
Homeowners give glowing reviews about living in a passive house, quoting a healthy living environment, with a year-round ambient temperature, and clean air, courtesy of the ventilation system. Not to mention the low energy bills.
The most successful and cost effective way of achieving Passivhaus certification is by incorporating the standard into your design. Its also useful if the Passivhaus elements are included in your planning application.
Building a passive house is a team effort. Ensure you have the right skills on the project. It can be as varied as getting an experienced team that has successfully delivered Passivhaus already or learning yourself on a Passivhaus Trust course.
It would be very hard to retrofit an existing house to the exacting standards, but there is an equivalent, less rigorous, standard for retrofits called EnerPHit (the ‘PH’ is for Passive House). Where Passivhaus looks to achieve 15kWh/m²/yr for space heating, EnerPHit aims for a more realistic 25kWh/m²/yr. As older homes use more energy than the average new one, there is more potential for energy savings and a reduction in CO2 emissions – anything between 75% and 90%.
Passivhaus open days are held nationwide every November, allowing you to visit a passive house in your area. There is also a Passivhaus show at the Potton Self Build Show Centre in Cambridgeshire. Alternatively you can visit the Passivhaus Trust website, which has a wealth of information and case studies. The Passivhaus Trust is an independent, not for profit organisation and a subsidiary of the AECB. The trust has an inclusive government structure that incorporates all relevant parts of the Passivhaus process and supply chain. As well as independent experts, academics, buildings-related charities and not for profit organisations.
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