Tag: carbon footprint

HPH316 : Why we must embrace sufficiency – with Lloyd Alter

Lloyd Alter explains how we can take personal actions to address our own carbon footprints, and why it’s more important to do so than ever.

Interview with Lloyd Alter

Lloyd Alter is an eminent writer at TreeHugger, a teacher of sustainable design at Ryerson University, and has spent many years working in the built environment field. But for his latest book,”Living the 1.5 Degree Lifestyle”, he has taken a wider view on the behavioural changes we can all make to lessen our carbon footprints and impact on the planet.

Personal actions matter

Lloyd took umbrage at a headline in the Guardian newspaper in 2017, that said 100 companies are responsible for 70% of emissions. By seemingly laying the blame with the oil companies it took away personal responsibility, and this was something he fundamentally disagreed with. As individuals, we have choices and are responsible for consuming what the oil companies are selling. It’s the consumption, not the production that is the biggest issue.

According to a study by Aalto University in Finland, The 1.5 Degree Lifestyle, 72% of emissions come from the choices we make, such as driving and eating habits, and it is these decisions that drive consumption.

The target average carbon footprint is 2.5 tonnes by 2030

Around the same time that Lloyd was reading into the idea of the 1.5 degree lifestyle, the activist and London mayoral candidate, Rosalind Readhead, was trying to live a lifestyle with the carbon footprint that we’re going to have in 2050, of one tonne of carbon per year. While he felt that would be impossible to manage, he did think he might be able to achieve the 2030 target and had agreement with a publisher to write a book about it.

“So that basically started the project of what can I do to produce less than 2.5 tonnes of carbon emissions for an entire year.”

An example of how Lloyd was tracking his carbon footprint

It is far easier to achieve in certain locations

By virtue of living in Toronto, Lloyd was already at an advantage over other locations when it came to the impact of his electricity usage. What with its nuclear and hydroelectric power generation, rather than coal-fired plants, the power there is almost entirely carbon-free.

He also lives in a suburb where he can collect groceries on foot, so not driving for a year becomes easier.

This is all in stark contrast to more remote areas just 100 miles away that have to rely on coal power, and vehicles for getting provisions.

Our street design should encourage walking, cycling and using public transport

Without sufficiency, efficiency is lost

One of the key things Lloyd has learnt through this process is moderation. How much is enough? By looking at life through a lens of sufficiency, you can ask yourself the questions such as do I need to build as big, or buy as much, or drive to the shops when perhaps walking would be better?

A big surprise for him was how, after gas usage, his Apple devices were the biggest contributor to his carbon footprint. Although they’re designed to use very little electricity, when embodied carbon is taken into account an iPhone alone releases 80kg of carbon in its manufacture.

Lloyd has always loved his Apple gadgets

“When you look at everything through the lens of embodied carbon, it changes everything.”

Lloyd now questions for example, whether there is a need to keep upgrading mobile phones when invited, when they are still perfectly efficient. And whether a new electric pickup truck seems such a good idea when its 40 tonnes of upfront carbon emissions is equivalent to nearly a lifetime allowance under the 2.5 tonnes that he is allocating per year!

With regards to housing, you could build a house that’s really big and efficient, but because it’s big it’s using more energy than a smaller house would. And although polyurethane foam has the best R value, it has a huge upfront carbon cost, especially when compared to cellulose or straw. This is why it’s important to build sufficiently, with the right materials that have the low embodied carbon, and that are relatively local.

Low rise, multi-family Passivhaus apartments in Munich

People’s perceptions have been changed by the energy crisis

Lloyd explains that two years ago when he spoke about Passivhaus, he had to talk about comfort and health, because energy was so cheap that putting in more insulation didn’t pay. However, with spiralling energy costs people are far more worried about building for resilience and ensuring that the house needs to use as little fuel as possible.

“If you’ve got a given budget, and you build better with more insulation and higher quality windows…you’re going to have to probably build a little bit smaller.”

Living sufficiently isn’t worse, just different!

An automatic reaction to thinking about this lifestyle approach, is that it will be less enjoyable, but Lloyd explains that this doesn’t have to be the case. Whereas he used to enjoy snowboarding, the reality was that he had to drive for three hours in order to get electrically winched up a hill, and slide down artificial snow made with electricity and water pumped up from the lake. He now straps a pair of cross country skis to his ebike and heads for the nearest park.

He is also now eating a lot less red meat and trading it instead for more white meat or vegetarian options. He’s not missing the steaks as now his diet is actually more varied and interesting.

He doesn’t feel he’s trading things for a more marginal experience, he’s just trading them for a different one.

The one area he does feel that he will struggle with though, is air travel. The US and Canada don’t have such good rail links as the UK and Europe, but the cheap airfares in Europe also make hopping on a plane for a weekend trip very attractive to many people. He thinks this will be the hardest thing for people to adjust to.

Lloyd has always enjoyed travelling to Portugal for their Passivhaus conference

“And we’re just going to have to change the way we do it, you know, no wild little weekend trips. But maybe you pack them together, take two weeks, go somewhere and really enjoy it and amortise that flight over a whole year worth of carbon.”

It’s far easier to make the changes if you realise what your carbon footprint is

Lloyd has had many comments from people who have read his book saying that it’s changing the way they live, because these were things they just hadn’t thought about before.

For Lloyd himself, one of the greatest joys has been replacing many of his car journeys with using his ebike, and he believes these could have the biggest impact in suburban areas. Other people are sharing his views and he talks of people telling him they’ve replaced their second cars with ebikes instead.

He also says that you don’t have to be rigid about your self-enforcement. If the single biggest thing you can do is cut back on eating red meat, then great, but that doesn’t mean you can’t have the occasional steak.

Personal actions also set an example to other people. Using the parallel of how smoking has become gradually more socially unacceptable over time, he hopes the same will become true of our carbon footprints.

Privilege can be a blind spot

Lloyd understands that he is in a position of privilege to have been able to make the changes he has without it being too much of a disruption to his life, but he appreciates that’s not possible for everyone.

“That’s the hardest thing that we all have to look at. It’s not to think, well, the example that I’m setting is something that works for everyone. We have to change society to the degree that the structure is there, so that people do have choices that they don’t have to choose between food and heat in their houses. We have to make it more equitable and more fair.”

Find out more

Visit the website of TreeHugger

Follow Lloyd Alter on Twitter

Purchase a copy of Living the 1.5 Degree Lifestyle

Transcript

Download a transcript of the interview with Lloyd Alter

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May 25, 2022
HPH238 : Making Passive House homes affordable – with Adam Cohen
Architect Adam Cohen explains how his modular construction system is making Passive House building simple and affordable.

Interview with Adam Cohen

Adam Cohen qualified with a Degree in Architecture from the University of Maryland 35 years ago. He was uninspired by the post-modern approach of the time, and instead was a keen follower of Ken Kern and Michael Reynolds‘ owner-built homes, and of Malcolm Wells‘ earthship movement.

After qualifying as an architect he set about building healthy homes that used no glues or chemicals, were off-grid, had first generation solar panels and composting toilets that they made themselves. Over the several years that followed he found it a struggle to find clients who wanted to build this way so, out of financial necessity, he started a more traditional company that he ran for 20 years, employing 43 staff where they designed what they built, and built what they designed.

“I had sold out completely”

The company was very successful financially but it wasn’t until ten years ago when his 12 year old son started asking questions about carbon footprints and climate change that he says he had a ‘slap in the face moment’. It brought home to him that because it had been hard to find people interested in energy efficiency at the time, that he had given up his principles and was building in an entirely different way.

That realisation gave Adam a renewed focus to “atone for all these sins. I’ve put a lot of potential carbon in the atmosphere by creating crappy buildings.”

Finding Pasivhaus in 2008, he became one of the first people in the US to take the training. Spending a month in Europe gaining his international certification and spending time with Passivhaus builders, he returned to the US with a desire to build commercial Passivhaus buildings using a design / build methodology.

“I realised how fragmented and dysfunctional the design and construction world really was.”

By 2012 others had started sitting up and taking notice of what Adam and his company were doing, and were keen to seek their assistance to help other teams. However his in-house firm of architects, engineers and builders where everyone was working together, wasn’t the way the process worked elsewhere.

Adam has made it his mission over the last few years, since selling his business, to try and help the industry move forward. He has recently moved to Canada and is helping Passive Buildings Canada put together an education programme to raise awareness that if you’re building new construction it should be done to a carbon neutral standard.

“They need to reduce their embodied energy and they need to reduce their operational energy and then they need to offset their carbon with either credits, site generation or local generation of energy.

We have the choice now to be proactive, or we have the choice later to be reactive.”

The construction industry needs greater awareness of climate change

Adam believes that in Canada, unlike the US, the federal, provincial and municipal levels are fairly well aligned in terms of being tuned in to the climate change emergency, however within the construction industry there is still not sufficient awareness from the consumers, owners, producers, architects or builders.

He sees there being far more awareness in the European design and construction community, and the population generally, but sees the greatest potential being what’s going to happen in China in the next 20 years.

Adam has written a draft paper called “The Integrated Modular Design Theory for High Performance,” which sees a need to move towards building with modular components that can be put together in different ways, manufactured easily and built efficiently.

The aim is for cost parity

Once Adam decided to divert his company’s focus to constructing healthy buildings, he realised this was only going to work if he could make an economic argument for it and get cost parity with the alternatives. In the commercial sector this wasn’t too difficult to achieve, but in residential it has taken a lot longer.

One of the first steps was to convince people to pay more for the construction of the building, instead of a cheaper building with higher energy bills.

“Then it became a question of, if you’re going to be paying eleven-hundred dollars a month for energy and mortgage and I can deliver a building that’s more comfortable, that uses less energy, and it’s going to cost eleven-hundred dollars a month or less…. if I could take some of that money that you’re spending on those electrons and put them into your mortgage so that you’re building equity and wealth rather than just spending money, but the net monthly cost is the same, why would you not do it?”

After three years of mining data they were able to put forward a proposition for single-family homes, where mortgage plus energy is equal to or less with a Passivhaus than you would pay for a standard house. Initially that was hard to achieve as windows had to be imported from Europe and there were very few suitable mechanical systems, but now the US market has options available.

Paying for an experienced team could save money

Adam tries to encourage owner-builders who are starting out on the process to create a team of people who have experience in Passivhaus, otherwise they might end up wasting money while they learn, to the cost of the client.

Adam has created a Lego style of system where owner-builders can buy a kit of pieces that snap together making a Passivhaus envelope very simple. Similar systems exist in the UK where you can buy a guaranteed shell and do the rest yourselves.

Understand the inter-relation between construction stages

Adam tries to simplify the thought process for self builders when approaching a new project, by helping them to understand the inter-relation between the different stages of the construction.

He breaks these down into four ‘buckets’. They are:
- Site acquisition – how much it is going to cost to buy the site
- Site development – how much it will cost to clear the site, install utilities, do any groundworks and landscaping
- The construction – the cost of getting the shell up, enclosed and tested for airtightness and thermal continuity
- The finishes – interior and exterior finishes, including mechanical and electrical and everything else within the shell.
He explains that when people have a fixed budget, he makes them understand that money can be moved around those buckets as none are fixed. There is an inter-relation between the site acquisition and site development buckets which need to be balanced, before you know how much there is left for the other two buckets.

Within each area there will be some costs which are fixed but others where savings can be made, such as with the complexity of the design.

“So, when you start to create your balance of how do I make all these pieces balance in this budget, I want people to understand that you need to separate out your thinking so that you understand, if I go spend a quarter of my budget on the site and then I spend another quarter of my budget on site development, so I have actually half of my budget to build the building with, is that realistic that I can actually get that building built?”

“Start with, ‘here’s the system, now let’s design to the system’.”

Using Adam’s Lego style system of modular construction, he explains how clients often use a free programme like Google Sketchup to help with their design. Rather than people coming up with a design and then trying to make it fit a manufactured system, this way allows clients to use the Sketchup modular blocks that Adam has created, to start their design. The manufactured products help generate an efficient form, leading to an affordable solution.

Consider the long-term impact

“I would hope that anybody considering a new build would try to work their way through to figure out how to build that building with the lowest impact possible. Because as a species, it’s critical that each of us make the right decision every day in everything we do, and if you’re building a building that’s going to saddle your grandchildren with ongoing operational energy that’s going to be carbon intensive, you’ve kind of just slapped your grandchildren in the face.

I know that the millions of square feet where I’ve built really bad buildings, I’m now approaching about a million square feet of Passivhaus buildings. So, not that I’m offsetting them, but at least I’m reducing my impact long-term.

So, I would encourage all of the individuals listening to this to consider their actions when building a new building, and how it will affect their grandchildren.”

Find out more

Visit the website of Build Smart

Follow Adam Cohen on Twitter

Check out Adam’s YouTube channel

Transcript

Download a transcript of the interview with Adam Cohen.

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Subscribe, rate and review the podcast in iTunes

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January 16, 2019
HPH184 : Balancing a self build with work and family life – with Donal O’Leary
Donal O’Leary tells us about his self-build in Ireland and shares advice for a successful project.

Interview with Donal O’Leary

We catch up with Donal O’Leary, the first House Planning Help Hub member to complete a self-build project! The decision to self-build came about by accident, as Donal and his wife were originally looking for a run-down property to renovate or rebuild. The properties they viewed didn’t quite meet their needs or budget, and suddenly the right site came along.

An unorthodox approach helped them secure their plot

Donal explains, “We didn’t really need the full site as it was. It was actually too big and therefore it was outside of our price range.” After making enquiries and seeking legal advice, they came to an agreement with a neighbouring landowner to join forces and put in a high enough offer to outbid another interested party. The site would then be split into two, for their own developments.

It took a year of planning before construction started

After acquiring and sorting out the site, the second year was the planning phase, split into obtaining formal planning permission and working with architects and quantity surveyors.

In Ireland, you have a pre-planning meeting with the local authority. This is an opportunity to run through plans and get approval to apply for formal planning permission (or find out what needs to be done differently). Donal explains you don’t have to have final drawings, but you do need to provide plans showing where the house will sit, access, and services like sewage and water.

Cost dictated the final design of the house

The site was large enough to accommodate a big house. But for Donal and family, the priority was a comfortable, clean and healthy home that would take advantage of the light and aspect, as well as modern insulation and air-tightness standards. Cost ultimately decided the final design, and the overall size was dictated by that design and how the spaces were arranged.

The budget was based on some funds left over from the sale of their previous property, plus the mortgage amount they would be able to secure. Donal adds, “The rainy-day fund and the piggy bank were all broken at this stage. So, we worked out roughly what we could afford…and worked back from that primarily.”

The planning phase included very detailed specifications

Their architect and quantity surveyor filled in most of the tender document template, detailing the build specifications. Donal and his wife provided additional information (such as doorknobs, stove handles, bathroom finishes) to complete the document.

It took five or six iterations of 20-30 page documents to figure out exactly what was needed. Donal says in hindsight it was definitely worth it, but at the time it was difficult. “You’re at the stage where you can’t even visualise what the house looks like, and you’re expected to say, ‘well, I want a Belfast sink with a tap that goes a certain way’.”

Time-wise, their biggest challenge was appointing a builder

Christmas time was the deadline for receiving responses to their tender. Donal says, “I’m sure the builders were delighted to be filling out a huge tender document on Christmas Eve!” They narrowed it down from four builders to two, met both and then picked one. Availability was a very important factor, as well as previous experience and price. The tender process took a couple of months and the actual build lasted just over 12 months from start to finish.

A precise calculation helped them stick to their budget

The quantity surveyor broke the build down to a very detailed level, so they knew exactly how much it would cost. Donal says they were reasonable estimates with a bit of wriggle room to alter the spec if needed, when it came to actually buying fixtures and fittings.

There were only a few minor changes during the build stage. Donal attributes this to the time spent upfront with their architect and quantity surveyor on the spec. It gave them a baseline to go back to, which helped them manage their finances. And they had monthly budget reviews with the builder.

They tried to attend site as often as possible

The building contractor was effectively the project manager. So for Donal, the biggest challenge was not a technical one, it was just keeping on top of everything and being available. He admits it’s difficult when you have to take calls and send emails while at work, but says you just have to find a way.

Donal advises others to take any chance they get – before or after work, or at lunchtime if you’re nearby – to go to site and give an opinion so things can move on. His wife spent any spare time during the day onsite, involved in the daily decision-making. Donal recalls a few times where just being there averted a disaster, explaining, “So, if we weren’t there, they would’ve done x, but because we were there, they did y.”

Keeping their architect engaged in the entire build process was worthwhile

Laws have changed in Ireland and you have to have an Assigned Certifier; an engineer or architect signs off the various certification and documentation across each phase of the build and can be held accountable by the local authority.

Donal and his wife chose to involve their architect (who they found through word of mouth) for the whole project. So she had a vested interest not just from a design perspective, but also legally and financially. As the client, they had the reassurance of a professional overseeing the builder.

They leaned on their architect quite a lot. As Donal explains, “It’s not just somebody who draws nice designs, prints them off and you go, ‘move a wall here, move a wall there.’ It’s far more than that. It’s a design eye, it’s finishing, it’s the construction knowledge that the average client doesn’t have.” She was a good sounding board when they had to make decisions, offering suggestions and steering them in the right direction.

Sustainability had to be balanced with budget

There were times where a sustainable option wasn’t the most economical or expedient, for example they considered rainwater harvesting but the cost involved would have pushed the build over budget.

However, they tried to reduce the carbon footprint of their new build where possible:
- Orienting the house for solar gain, with canopy-style shading to reduce overheating.
- Avoiding the need for oil due to high-spec insulation.
- Using an air source heat pump.
- Leaving some of the garden as a nature area for wildlife, planting some clover there instead of grass so as to have a low maintenance meadow.
Transcript

Download a transcript of the interview with Donal O’Leary

How stupid is our obsession with lawns?

If you’re planning a vast lawn for your new house, is it actually the most sustainable thing to do?

Donal recommends listening to a Freakonomics episode which ponders how natural lawns are and looks at alternatives.

And if you enjoy that, check out last year’s interview with Lisa Kerslake on creating a biodiverse garden.

Please connect with me
- Subscribe, rate and review the podcast in iTunes
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July 14, 2017
HPH132 : What is modular design and how does it work? – with Peter Schneider
Peter Schneider explains how modular homes are built, and why they are an ideal replacement for traditional manufactured mobile homes.

Interview with Peter Schneider

Peter Schneider is a senior consultant at Efficiency Vermont and the Vermont Energy Investment Corporation (VEIC), a non-profit organisation which aims to reduce the long term and immediate costs of energy.

6 years ago he began looking to achieve the Passivhaus standard in modular homes built at a local factory.

Modular homes can be made from single or multiple boxes

They work with 16ft wide modules of varying lengths and have an exterior thermal envelope which houses the insulation, air barrier and weather barrier siding.

Multiple boxes on the same floor level are typically connected by an uninsulated wall with interior door openings, or just open spaces to move from one box to the next.

For boxes that fit on top of one another, there is a ceiling and floor system that connect together which provides rigidity when transporting and lifting the modular homes into place.

The boxes are built in a factory and transported on a flatbed trailer and delivered to the site where they are lifted by crane and set onto a foundation. The boxes are then moved together, fastened, fixed to the foundation and to themselves.

A series of detailing with regards to airtightness, the weather barrier, and the siding needs to be done on site, but typically the houses can be delivered, installed and made airtight and weathertight within a single day.

More complicated forms will have cost implications

Designs aren’t limited to four sided boxes but in order to take advantage of the modular build process with regard to cost and performance they generally do use the simple geometry of putting boxes together.

Peter says that any forms can be built with this system, but there are cost advantages to getting as much built in the factory as possible as it will minimise the amount of work needed on site, which is typically where extra costs will occur.

“The simpler the number of boxes, the less work that needs to be done on site, the better cost optimised the modular approach is.”

Modular homes traditionally have a stigma of not being as good quality as custom houses built on site

This is something the industry is working to change and Peter believes that builders, home owners and architects are beginning to see the value of working with modular manufacturers.

A benefit of factory building is that they are being made within a climate controlled environment, and aren’t susceptible to the problems of delays and trying to keep materials and equipment protected from weather on site. This results in a faster build process, and with a very close eye on attention to detail in a lot of factories, is producing homes which Peter says are exceeding the quality, creativity and performance of custom built houses on site.

The width is restricted by transport legislation

Rules vary according to State, but in Vermont the maximum width allowed to travel down the road is 16ft. Length can be unlimited with homes typically being delivered of around 70ft length, which incorporating the truck means a full length of around 100ft. There may however be limitations in transporting something of that size when it comes to corners and inclines, so the route from the factory may determine the length that can be delivered.

With a 16ft width restriction it wouldn’t make sense to choose an 18ft or 20ft model, as the cost implications would mean that you wouldn’t be taking advantage of the modular construction.

Because of the stresses of transport and being lifted by crane, there can be structural implications to modular homes, where certain things that might work well on houses built on site, therefore wouldn’t be applicable to modular.

As well as potential width and geometry limitations, an area that could be compromised is the attention to detail on site. There must be clarity with the user manual and instructions from the factory to ensure that the boxes are tied together properly, the airtight and weathertight barriers are installed correctly and in the way that the factory intended. Something more factories are doing is sending their own crews to finish the homes on site, ensuring everything is done the way they intended, and even warrantying the houses themselves and providing any follow up maintenance.

Modular homes can be an answer to an affordable home shortage

Historically, affordable housing has been concerned with initial cost price. However, lower cost homes tend to come with the drawbacks of worse insulation, poor windows, doors and airtightness. These aspects of lower cost construction result in higher maintenance costs and rising energy prices, making it difficult for lower income residents to build wealth. Additionally these types of homes can even depreciate in value.

These types of homes traditionally have been manufactured mobile homes. They’re delivered and remain on a steel chassis and while they may be very low cost up front, the poor air quality, ventilation, product choices and energy usage are costly to the residents.

“We’re not quite 1 out of every 10 homeowners in the country living in a manufactured home, but we’re not far under that. So we have a lot of people living in these manufactured homes and they’re burdened by living in a home that’s losing asset value over time, and a home that’s very hard to build wealth and actually get out of. So we have a lot of residents who will be in these homes 20/30 years until they’re really uninhabitable. “

Instead, Peter says they are looking at life cycle costs and how they can help homeowners and tenants to have better, healthier housing, with an opportunity to reduce maintenance and operation costs, while also helping them build wealth.

“Right now we’re showing that in the lowest income sector, that is sort of our mobile homeowners, we can deliver a home that on a monthly basis is going to cost less than the alternative home that is a manufactured home, mobile home, it’s going to cost less month one. That is its energy plus mortgage cost. And this doesn’t even factor in all the non-energy benefits like the health implications that you have living in a home with poor ventilation and high off-gassing materials.”

Transcript

Download a transcript of the interview with Peter Schneider.

Find out more

Find out more about Vermont Energy Investment Corporation

Visit the website of VerMod

View a VerMod presentation

National Self Build and Renovation Centre Summer Show

Ben Adam-Smith will be speaking at this event on Friday 17th June on the subject of “Behind the scenes of self build”, looking at the lessons he has learned in trying to build a house. Tickets are only free if purchased in advance online.

Even if you can’t make this session it is worth checking out the NSBRC website to see when their next event is happening.

The Hub update

This month we have added another chapter in the Long Barrow Passivhaus story. The house uses an Insulated Concrete Framework construction method, and in this chapter we’re looking in greater depth at it’s pros and cons, the role it plays, and why there’s a lot of steel on this project.

For more information about the group Facebook page, the quarterly progress calls and to see everything else it has to offer, check out The Hub.

Please connect with me
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June 8, 2016
HPH081 : Rainwater Harvesting From Your House – with Cath Hassell from ech2o consultants
Cath Hassell from ech2o consultants explains what rainwater harvesting is, why it’s useful and how to get started.

If you haven’t heard our first podcast interview with Cath on the topic of saving water, check that one out first!

Interview with Cath Hassell

Rainwater harvesting is just one way of stopping rainwater from getting into our drains and sewers.

If the house is in a city and rainwater is going into a combined sewer, then there will be more waste water to treat and there may be times when water treatment plants can’t cope and so the water spills out into local rivers or the sea.

Keeping rain out of the stormwater stream reduces the likelihood of this occurring.

What is Rainwater Harvesting?

Rainwater harvesting is collecting rainwater that falls on the roof of a building. It’s taken from the roof because this is usually the cleanest water. This water is then stored outside but it can be used back in the building (for flushing the toilets, cleaning purposes, in washing machines, etc.) or it can be used outside the building for gardening.

Water is Stored Underground Because It’s Heavy

There are two main reasons why water is stored underground:

1. It’s heavy and therefore it does not want to be kept high up on top of a roof

2. The water will be cool if stored underground reducing the risk of bacteria

Water tanks can take up quite a lot of space so this might be another reason why it’s best to locate them underground.

Setting Up Rainwater Harvesting is Easier for New Build

In a new build house there is already going to be earth-moving equipment on site and so it becomes cheaper to dig a big hole.

While it can be done in a retrofit situation, the initial set-up may cost more. There may also be issues such as no access to the back of a house (in a terrace, for example).

Rainwater is Not Fit For Drinking or Bathing

Astonishingly, in the UK, rainwater is actually given the same classification as water that has been swept from abattoir floors or contaminated with nuclear waste. For this reason there needs to be different pipework which runs to domestic taps, than for that which runs to toilets, washing machines etc.

An Air Gap is Required to Prevent Water From Syphoning Back Into The Pipework

The air gap is basically the space in between where the water can’t touch the taps. If a sink was overfilled the water would go down through the overflow or spill onto the floor and there would be no risk of the potentially dirty bathing water from re-entering the mains system through the taps.

A High Carbon Load Damages The Reputation of Rainwater Harvesting

The air gap does result in a loss of mains water pressure which can be overcome by pumping it to where it is needed, though using electrical pumping obviously does have a financial and carbon cost associated. The performance of the pumps can however be optimised by using particular valves.

A high carbon load is one of the arguments that gets used against rainwater harvesting, but Cath would welcome research to be carried out looking at how taking rainwater out of the stormwater stream impacts on the reduced carbon load of the sewers and sewage treatment plants by reducing pumping there.

Decisions About Rainwater Systems Can Influence The Designs of a New Building

Cath suggests that if you’re planning a green roof she would not recommend rainwater harvesting for use back in the building. This is because the water run-off from the green roof will be discoloured and residents of the building may start using bleaches and cleaning products to remove the staining to their toilet pans.

There is no reason why rainwater couldn’t be harvested by other areas of the building which do not have a green roof, and simply designed in with the gutters and downpipes.

A Calculation Determines The Size of The Required Rainwater Storage Tank

The storage tank holds approximately 5% of the anticipated rainwater that will be harvested in a year, which equates to around a 3 week supply. This is usually enough as the rain falls year round in the UK but there will still be some times where the tank will be too full or too empty. When empty the supply can be switched temporarily back to the mains, and when too full the overfill can be directed back towards the stormwater drains or into areas of garden that can cope with being inundated by water.

Cath Has a Kickstarter Project to Produce a Book Designed to Help Educate Children

A lot of Cath’s work is designing systems for schools. She has a Kickstarter project which will enable her to produce a book explaining about how the toilet systems work which she will be able to use when talking with the children.

The Storage Tanks Are Generally Either Made of GRP (Glass Reinforced Polyester) or Polyethylene

In the early days of rainwater harvesting the storage tanks tended to be made of concrete. Nowadays the two options are GRP (mostly for larger tanks) or poly (mostly for smaller tanks).

A life cycle analysis was carried out on the two by Judith Thornton (CAT, AECB) who found that poly tanks were far better in terms of overall carbon footprint.

Use Rainwater Harvesting Purely For The Garden if The Demand is Great Enough

Cath recommends that for a domestic situation where you have a large requirement for garden watering, that you just use the rainwater for that and do not try and bring it into the house. Her reasons for this are because of the extra pipework and pump (for the mains backup) that will be needed. An additional outdoor mains tap will provide extra if required.

If you’re harvesting rainwater purely for garden use then a different calculation for the storage tank is required. This reflects that as much water as possible will be collected during the non-growing months, in order to provide the best supply for the growing months.

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Transcript

Download a transcript of the interview with Cath Hassell.

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January 11, 2015