Monday, July 22, 2019

Passive housing is a very active way to combat climate change and cut costs

passive house

Imagine living in a house which heats and cools itself, which saves significantly on energy costs and keeps you healthy and comfortable – and helps to cut greenhouse gas emissions in the process.

The good news is that, in the UK and several other countries, you don’t need to imagine it. Houses as good as that are available to those who can afford them, thanks in large measure to the Passivhaus Trust, an independent non-profit organisation which promotes the principles of low-energy design.

“If you want to get to zero carbon, Passivhaus gets you most of the way there, and a bit of renewable energy finishes the job”, says Jon Bootland, the Trust’s CEO.

The Trust is one of the winners in this year’s Ashden Awards, an annual international competition to encourage sustainable energy. Passivhaus topped the shortlist for the 2017 award for sustainable buildings.

The awards will be presented on 15 June by Al Gore, the former US vice-president turned climate campaigner, at a ceremony at the Royal Geographical Society in London, with each UK winner receiving £10,000 (US$13,300) to support their business (overseas winners receive twice as much).

Passive cooling and heating of houses is a technique that has been used in different parts of the world for thousands of years: one example is the wind towers which are a centuries-old feature of house design in the Middle East.

The Passivhaus secret, an updated version of this ancient tradition, is no great surprise: it’s a range of practical measures, like enhanced insulation, high quality windows, and buildings that are designed to be airtight, with controlled ventilation.

They are built with great attention to detail and rigorous design and construction principles, certified through an exacting quality assurance process.

A core part of the Passivhaus standard, obviously, is passive design, which makes the greatest use possible of daylight for lighting, the sun’s warmth for heating in the winter, shading to reduce heating in the summer, and ventilation to provide summer cooling.

With good insulation and close attention to keeping buildings airtight, most homes can be heated for much of the year by a combination of sunlight, waste heat from electrical appliances, and the body heat of occupants.

Ventilation in colder months is provided mechanically, but with a heat recovery system to capture heat from the outgoing air and use it to warm the incoming air. In warmer months occupants often open vents and windows to provide a natural flow of air through the building.

Over 1,000 Passivhaus homes and buildings in the UK are expected to be completed by the end of 2017. Bills for heating and hot water in can be £500-£1,000 a year lower than in normal houses, depending on the size of the home. Annual space heating energy use is limited to 15 kilowatt hours per square meter (15 kWh/m2 per year).

The result is that households in Passivhaus homes are less likely to experience fuel poverty, because their energy bills are so low despite the homes being at a comfortable temperature. More than a quarter of the UK’s energy use and CO2 emissions result from domestic energy use, the greater part of it for heating.

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