Climate change is a very real concern these days. Even hardcore denialists are a little quiet in the face of unseasonable storms and extreme weather, the likes of which we have never seen before. But, the average man and woman on the street have bigger concerns, like how to save money in times that are still economically uncertain. Passive homes are a solution to both problems, giving people the opportunity to save money on their heating and electricity bills, while living in a virtually zero-carbon environment.
What is a passive house?
A passive house (passivhaus) is one that has been built to very strict (German strict) energy-efficient standards. According to Wikipedia, it’s characterised by a small eco-footprint and super-low energy requirements. While the concept is most often applied to residential homes, there are also passive office buildings, schools and, apparently, a supermarket.
While the most efficient passive houses are those that have been built from scratch – the principles are best integrated with the design – it is possible to retrofit a house to make it passive.
In technical terms, a passive house should not exceed 15 kWh/m² per year in heating and cooling. Alternatively, it should have a peak heat load of 10W/m². Furthermore, according to Wikipedia, total primary energy consumption shouldn’t exceed 120 kWh/m² per year, and it shouldn’t leak more air than 0.6 times the house volume per hour at 50 Pa (N/m²).
How is this achieved?
To achieve this, passive homes have to be super-insulated (walls, floors, ceilings, roof, doors and windows) and super-airtight, and they make use of heat recovery ventilation systems, which extract heat from appliances, lighting and electrical devices (and even body heat) and also ensure that fresh air circulates throughout the house at all times. It does, however, require a little bit more, such as:
- Passive solar design, which basically means building it in the right place and at the right angle for it to make optimum use of sun exposure. It means placing windows in the right positions, and even making clever use of skylights.
- High-tech windows, which tend to be triple-glazed with extras like argon or krypton gas-filled inter-panes, insulating glass spacers, air seals and thermally broken window frames (according to Wikipedia).
- Natural ventilation systems are favoured, especially using multifunctional skylights and, of course, the high-tech windows.
- Temperature is regulated by the heat recovery ventilation systems mentioned, as well as earth warming tubes, heat exchangers and solar gain and sometimes, in extreme climates, by a supplementary central heating system or even a wood-burning stove.
- Energy-efficient appliances and lighting are a given.
There is this idea that building a passive homes are exorbitantly expensive to build – prohibitively expensive, even. This is not true.
They are more expensive, but it’s been estimated that they only add 5% to 10% to construction costs, and this is set to come down as the materials become more readily available (and cheaper to manufacture), and as architects and building companies become more familiar with their construction. In fact, according to NYPH, an organisation that promotes passive home construction and energy standards in New York State, you can bring down costs by choosing experienced builders, as they have already got over the learning curve and are in the process of refining their art.
As part of its efforts to promote passive homes, NYPH emphasises the fact that the money saved on energy bills pays for the house in fewer than 10 years. Moreover, the organisation says that the saving on monthly energy bills can rival mortgage repayments, so residents start benefiting financially immediately.
Lindsay Wilson breaks it down in cash terms. You might pay $1500 a year to heat an old home (with all its weather-worn draughts and whatnot). You might pay $750 a year to hear a modern home. But you’ll only pay $100 a year to heat a passive home. And that’s only considering the heat. It doesn’t include other energy costs savings, like lighting and ventilation. If you do it really well you could actually generate energy to put back into the grid – for which you get paid.
It’s not the end of the world if you aren’t building a home from scratch, as the Guardian’s Lucy Siegle says that even retrofitting your home using passive house principles can reduce your energy consumption by up to 75%. You can go about retrofitting your home by sealing all the joints and seams and blocking off any draughts, especially around doors and windows. You can also insulate the roof and ceiling, wall cavities, and windows. Even adding thick carpets and curtains can make a difference. It might not meet German standards, but as they say, every little bit helps.
Jemima Winslow dreams of her own off-grid, zero-carbon, passive home complete with roof garden, veggie garden and happily lowing cows. Until then, she appeases her conscience with energy-efficient light bulbs and low-energy appliances and by turning on her geyser for only an hour a day.
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