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Passivhaus: maximising comfort while minimising energy



In the late 80s, two building researchers – Bo Adamson of Lund University, Sweden and Wolfgang Feist of Institute for Housing and the Environment, Germany – came up with an idea to maximise the comfort of homes while dramatically reducing their energy usage. The result was the Passivhaus standard, by which over 25,000 properties around the world are now certified .

In the UK, the Passivhaus standard has been promoted and protected by the Passivhaus Trust since 2010. It’s a very new concept, with around 200 complete and certified passive houses currently.

But with over 500 Passivhaus-certified buildings in the pipeline, within two years there is set to be over 1,000 homes with the accreditation.

The Passivhaus Trust’s chief executive Jon Bootland tells Blue & Green Tomorrow more.

This article originally appeared in Blue & Green Tomorrow’s Guide to Sustainable Homes 2013.

Why do we need the Passivhaus standard?

There are consistent problems in the performance of new homes around their energy use, ventilation and potential overheating risks, and therefore the wellbeing of the occupants. Passivhaus, as a low-energy and comfort standard, gives you a software tool and a standard to come up with a solution that addresses all of those things and resolves them all for you.

The Passivhaus Trust promotes the standard in the UK, ensures its integrity, and makes sure that when Passivhaus buildings are built to that standard, they do what they say. It’s a very high quality standard that has a lot of rigour in its approach.

What is a passive house?

It’s a very low-energy building that provides optimal occupant comfort conditions, adjusted for the local environment.

More specifically, it’s a building that can meet all of its heating energy requirements, simply by heating small amounts of ventilation air coming into the building. You need very little heating.

Is the definition of a sustainable home different?

Passivhaus is an energy and comfort standard only. That’s all it does. It does that very well, and very few other people can do that at the minute.

A sustainable home must address lots of other things as well, such as the kind of materials that you use in the home, or whether you’ve got green space nearby, or whether you’re sited near public transport links or local amenities. Passivhaus doesn’t address any of those; it just sorts out very well the energy and comfort parts.

Is the Passivhaus standard for new homes only?

No, there is a Passivhaus standard for retrofit as well. It’s a very exacting standard, so it’s not something to be undertaken lightly. And it is slightly less demanding than the new-build standard, because it needs to take into account things that you can’t change, like the orientation of the building, which affects how much sunlight you’ll gain during winter months for example.

You can’t change that when your house is already built, so we have to make an allowance for that on existing homes. It’s also very difficult to insulate underneath the floor in an existing building, so the standard is relaxed slightly for a refurbishment project, but it is still very demanding.

Can the Passivhaus standard become mainstream?

I’m not sure it’s going to be a product for the mass market house builders for a few years. That’s because the main benefit is in the running costs, which benefit the occupier, not the builder! Heating bills might be £100-£200 per year for a Passivhaus, compared to £1,200-£1,500 a year for a typical home. That’s an enormous difference.

If you’re a private buyer and this is going to be your house for life, and you’re going to be retiring into this house and owning it for 20 years, saving £1,500 a year on your heating bill makes a lot of sense. You’ll have a much higher quality home, it should retain its value better and it should be easier to maintain, so it’s worth paying a little bit extra in order to have that saving.

But if you’re a major house builder and you’re just going to sell the houses and then leave, the savings will accrue to the person who buys the house and lives there – not the person who built it.

What do you see of the future of sustainable homes?

The government is very keen to water down and relax standards at the minute. The Housing Standards Review is underway at the minute and it seems likely that the Code for Sustainable Homes might be axed, for example. So in broad sustainability terms, I think the immediate future looks a little bit bleak.

But for low-energy homes, I think it’s a different matter. The government is still committed to improving the standards of new homes towards the Passivhaus level and Passivhaus is still above what current regulations require.

Buyers and homeowners are also starting to get switched onto it. There was some research last year that showed people expect an energy efficient home to hold its value better and to be worth more in the long-term, so I think homeowners will start to recognise the value of having a very low-energy and energy efficient home. I think that will start to drive the market on the energy efficiency front.

In addition, as well as being a good investment for individual, high-end homeowners, I think that Passivhaus also makes a lot of sense for housing associations whose tenants are in fuel poverty to have very low fuel bills. So the future for Passivhaus could be bright indeed.

Jon Bootland is chief executive of the Passivhaus Trust.

Further reading:

Making your period home more energy efficient: a practical guide

Mythbusting on sustainable homes

Superhomes for a super future

Creating a low-carbon home of your own

The Guide to Sustainable Homes 2013


Will Self-Driving Cars Be Better for the Environment?



self-driving cars for green environment
Shutterstock Licensed Photo - By Zapp2Photo |

Technologists, engineers, lawmakers, and the general public have been excitedly debating about the merits of self-driving cars for the past several years, as companies like Waymo and Uber race to get the first fully autonomous vehicles on the market. Largely, the concerns have been about safety and ethics; is a self-driving car really capable of eliminating the human errors responsible for the majority of vehicular accidents? And if so, who’s responsible for programming life-or-death decisions, and who’s held liable in the event of an accident?

But while these questions continue being debated, protecting people on an individual level, it’s worth posing a different question: how will self-driving cars impact the environment?

The Big Picture

The Department of Energy attempted to answer this question in clear terms, using scientific research and existing data sets to project the short-term and long-term environmental impact that self-driving vehicles could have. Its findings? The emergence of self-driving vehicles could essentially go either way; it could reduce energy consumption in transportation by as much as 90 percent, or increase it by more than 200 percent.

That’s a margin of error so wide it might as well be a total guess, but there are too many unknown variables to form a solid conclusion. There are many ways autonomous vehicles could influence our energy consumption and environmental impact, and they could go well or poorly, depending on how they’re adopted.

Driver Reduction?

One of the big selling points of autonomous vehicles is their capacity to reduce the total number of vehicles—and human drivers—on the road. If you’re able to carpool to work in a self-driving vehicle, or rely on autonomous public transportation, you’ll spend far less time, money, and energy on your own car. The convenience and efficiency of autonomous vehicles would therefore reduce the total miles driven, and significantly reduce carbon emissions.

There’s a flip side to this argument, however. If autonomous vehicles are far more convenient and less expensive than previous means of travel, it could be an incentive for people to travel more frequently, or drive to more destinations they’d otherwise avoid. In this case, the total miles driven could actually increase with the rise of self-driving cars.

As an added consideration, the increase or decrease in drivers on the road could result in more or fewer vehicle collisions, respectively—especially in the early days of autonomous vehicle adoption, when so many human drivers are still on the road. Car accident injury cases, therefore, would become far more complicated, and the roads could be temporarily less safe.


Deadheading is a term used in trucking and ridesharing to refer to miles driven with an empty load. Assume for a moment that there’s a fleet of self-driving vehicles available to pick people up and carry them to their destinations. It’s a convenient service, but by necessity, these vehicles will spend at least some of their time driving without passengers, whether it’s spent waiting to pick someone up or en route to their location. The increase in miles from deadheading could nullify the potential benefits of people driving fewer total miles, or add to the damage done by their increased mileage.

Make and Model of Car

Much will also depend on the types of cars equipped to be self-driving. For example, Waymo recently launched a wave of self-driving hybrid minivans, capable of getting far better mileage than a gas-only vehicle. If the majority of self-driving cars are electric or hybrids, the environmental impact will be much lower than if they’re converted from existing vehicles. Good emissions ratings are also important here.

On the other hand, the increased demand for autonomous vehicles could put more pressure on factory production, and make older cars obsolete. In that case, the gas mileage savings could be counteracted by the increased environmental impact of factory production.

The Bottom Line

Right now, there are too many unanswered questions to make a confident determination whether self-driving vehicles will help or harm the environment. Will we start driving more, or less? How will they handle dead time? What kind of models are going to be on the road?

Engineers and the general public are in complete control of how this develops in the near future. Hopefully, we’ll be able to see all the safety benefits of having autonomous vehicles on the road, but without any of the extra environmental impact to deal with.

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New Zealand to Switch to Fully Renewable Energy by 2035



renewable energy policy
Shutterstock Licensed Photo - By Eviart /

New Zealand’s prime minister-elect Jacinda Ardern is already taking steps towards reducing the country’s carbon footprint. She signed a coalition deal with NZ First in October, aiming to generate 100% of the country’s energy from renewable sources by 2035.

New Zealand is already one of the greenest countries in the world, sourcing over 80% of its energy for its 4.7 million people from renewable resources like hydroelectric, geothermal and wind. The majority of its electricity comes from hydro-power, which generated 60% of the country’s energy in 2016. Last winter, renewable generation peaked at 93%.

Now, Ardern is taking on the challenge of eliminating New Zealand’s remaining use of fossil fuels. One of the biggest obstacles will be filling in the gap left by hydropower sources during dry conditions. When lake levels drop, the country relies on gas and coal to provide energy. Eliminating fossil fuels will require finding an alternative source to avoid spikes in energy costs during droughts.

Business NZ’s executive director John Carnegie told Bloomberg he believes Ardern needs to balance her goals with affordability, stating, “It’s completely appropriate to have a focus on reducing carbon emissions, but there needs to be an open and transparent public conversation about the policies and how they are delivered.”

The coalition deal outlined a few steps towards achieving this, including investing more in solar, which currently only provides 0.1% of the country’s energy. Ardern’s plans also include switching the electricity grid to renewable energy, investing more funds into rail transport, and switching all government vehicles to green fuel within a decade.

Zero net emissions by 2050

Beyond powering the country’s electricity grid with 100% green energy, Ardern also wants to reach zero net emissions by 2050. This ambitious goal is very much in line with her focus on climate change throughout the course of her campaign. Environmental issues were one of her top priorities from the start, which increased her appeal with young voters and helped her become one of the youngest world leaders at only 37.

Reaching zero net emissions would require overcoming challenging issues like eliminating fossil fuels in vehicles. Ardern hasn’t outlined a plan for reaching this goal, but has suggested creating an independent commission to aid in the transition to a lower carbon economy.

She also set a goal of doubling the number of trees the country plants per year to 100 million, a goal she says is “absolutely achievable” using land that is marginal for farming animals.

Greenpeace New Zealand climate and energy campaigner Amanda Larsson believes that phasing out fossil fuels should be a priority for the new prime minister. She says that in order to reach zero net emissions, Ardern “must prioritize closing down coal, putting a moratorium on new fossil fuel plants, building more wind infrastructure, and opening the playing field for household and community solar.”

A worldwide shift to renewable energy

Addressing climate change is becoming more of a priority around the world and many governments are assessing how they can reduce their reliance on fossil fuels and switch to environmentally-friendly energy sources. Sustainable energy is becoming an increasingly profitable industry, giving companies more of an incentive to invest.

Ardern isn’t alone in her climate concerns, as other prominent world leaders like Justin Trudeau and Emmanuel Macron have made renewable energy a focus of their campaigns. She isn’t the first to set ambitious goals, either. Sweden and Norway share New Zealand’s goal of net zero emissions by 2045 and 2030, respectively.

Scotland already sources more than half of its electricity from renewable sources and aims to fully transition by 2020, while France announced plans in September to stop fossil fuel production by 2040. This would make it the first country to do so, and the first to end the sale of gasoline and diesel vehicles.

Many parts of the world still rely heavily on coal, but if these countries are successful in phasing out fossil fuels and transitioning to renewable resources, it could serve as a turning point. As other world leaders see that switching to sustainable energy is possible – and profitable – it could be the start of a worldwide shift towards environmentally-friendly energy.


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