Tag: rainwater harvesting

HPH179 : How to deal with sewage for a self build home – with Cath Hassell
Cath Hassell from ech2o consultants explains why connecting to mains drainage is generally the best option for a new build home. She also runs through some alternatives if this is not possible.

Interview with Cath Hassell

Cath Hassell from ech2o consultants talks us through the options available when planning drainage for your self-build.

Practical experience informs drainage design

Drainage is not something usually learnt by architects during their studies. Large architect firms typically employ drainage engineers. On a job with a smaller budget, the builders deal with drainage as they have the know-how.

There’s a choice of materials for drainage pipes

Cath explains that taking sewage away from the house is essentially a simple process, covered by Building Regulations. Lay a pipe in a trench (at a one in 40 drop) up to your site boundary, and backfill. The local water authority will then make the final connection.

Builders tend to prefer using uPVC for the pipe. However uPVC pipe has to be laid in gravel, displacing earth that may need to be removed from site. So Cath always specifies clay pipe, which can simply be backfilled with site earth, and has plastic connectors for ease of use.

If you’re near to mains drainage, use it but don’t overload it

According to Cath, the Environment Agency are now saying if you’re near to mains drainage, you have to use it for your new build. There are few areas where the sewage systems are overloaded; issues only happen during rain events.

That said, it’s important to minimise what has to be taken away as it takes energy to pump along the sewer system and treat. The first step is to contact your local council or Building Control department to find out whether you’ve got separate sewers that take 1) foul and waste water, and 2) rain water, or combined sewers where they’re mixed together.

If possible, you want to keep rainwater out of combined sewers. And even if you have separate sewers, Cath recommends dealing with rainwater onsite. One way is to harvest rainwater, as Cath has explained in a previous podcast. She also mentions SuDS (sustainable drainage systems) for managing surface water.

Cesspools aren’t an environmentally friendly option

Where mains sewers aren’t available, cesspools have been used to capture waste to be processed elsewhere. While they ensure it doesn’t go into the ground or water, Cath says that environmentally it’s a really bad idea and it’s very costly anyway, explaining, “You’ve got to pay somebody to come in, pump it out and then take it to a sewage treatment plant and pump it into the plant.” Her advice is to deal with it onsite.

Use a low-flush, dual-flush loo

Unless you’re on a site in a dry part of the UK and solely reliant on rainwater, Cath wouldn’t bother with composting toilets. They take up space and many are in fact dehydrating toilets that require electricity to dry out the poo. She points out that some people fixate on composting toilets but don’t even compost their vegetable waste!

However, if you’re building a workshop / cabin / sleepover place in the garden, there are some simple compost toilets available and preferable to a chemical toilet. Cath likes the look of this product.

A septic tank is not just a hole in the ground

Septic tanks have been a popular option for 800,000 properties in the UK not on mains drainage.

What a septic tank does is settle out the solids to be broken down by anaerobic bacteria. Some of the solids sink to the bottom, and some float to the top forming a crust. Historically, the resultant effluent left the tank to be treated via a ditch, stream, soakaway or drainage field.

A lot of those systems failed, and an EU Groundwater Directive was passed in 2006 to prevent further contamination. On 1^st January 2015, the UK finally changed their regulations and Cath explains why you can no longer use a septic tank if you want to go into a stream or surface water. “The bacteria will go ‘wayhey, poo, brilliant’, they’ll start eating it, they’ll start to multiply.” This takes the oxygen from the water, which means that there’s less for fish and plants. And because you’re putting in a whole pile of nutrients, you’ll also get nitrification and algal blooming. So now you have to use what’s called a package sewage treatment plant.

Package sewage treatment plants guarantee good quality effluent

Package sewage treatment plants use aerobic bacteria to more effectively break down the waste. This requires introducing air into the system, normally using a pump. Or in the case of a Biodisc – a make of package sewage treatment plant – by use of a rotating disc inside.

Without air the aerobic bacteria will die, so these systems have to be run continuously even if you don’t live onsite full time. The electrical cost may therefore be a consideration. But unlike septic tanks, these systems provide certainty that you will not be putting nutrients into the water or your drainage field.

Drainage fields can clog up for various reasons

A drainage field is a series of slotted pipes in a herringbone pattern laid across the land so that the effluent from a septic tank or package sewage treatment plant will percolate down through the ground.

Septic tanks often clog drainage fields if:
- The tanks are poorly maintained
- The ground is fissured rock, where drainage is too fast and there are no aerobic bacteria left to deal with the bits of organic matter going into the field
- The ground is clay, where eventually the clay gets clogged up and rain may wash off bits of matter into neighbouring streams
There are alternatives to drainage fields

Soil type may mean a standard drainage field cannot be installed for a septic tank or package sewage treatment plant. If this is the case, Cath has some suggestions:
- Effluent from a package sewage treatment plant can be discharged into a nearby stream or ditch that leads to a stream
- Reed beds, constructed wetlands and willow trenches can deal with foul water and waste water onsite
You can get horizontal flow or vertical flow reed beds. Sometimes they’re called constructed wetlands, although this term can mean different things as explained in Septic Tank Options and Alternatives by Feidhlim Harty (written for Ireland, but relevant to the UK).

Reed beds are sometimes seen as environmentally better options. However, Cath urges people not to put them in just to bring biodiversity on the site, as there are much better ways including bat and bird boxes, planting and hedges.

Horizontal flow reed bed from Building Regulations Part H

Vertical flow reed bed from Building Regulations Part H

You now have to show you’re maintaining your sewerage system

If you have an existing septic tank you will have to prove by 2020 that your system is working and being maintained properly. Right now, however, the Environment Agency is concentrating on new builds meeting regulations.

Maintenance of septic tanks is relatively simple, as they contain no moving parts. Contractors take off the crust at the top, and remove sludge from the bottom. With a package sewage treatment plant, they still ‘de-sludge it’ but also check the pump is working properly.

Find out more

Visit the website of ech2o consultants

Follow Cath on Twitter

Download information from Cath

Download the map of UK water companies

Transcript

Download a transcript of the interview with Cath Hassell

Watch Cath’s stand-up gig: a plumber in a world of engineers

Join the House Planning Help team

We’re always on the look out for talented individuals to join our growing team.

Perhaps you work in TV, radio or for a newspaper, but would love to be making content about eco homes.

Or maybe you’re already in the green building industry but want to turn your hand to teaching.

Or perhaps you’re a teacher who is just drawn to this area.

Well, if you think you’d be a good fit for House Planning Help, please get in touch.

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June 1, 2017
HPH152 : Should you consider the resale potential of your self build? – with Mike Coe
Mike Coe explains what he’s learned while trying to sell his energy-efficient home and how it has made him re-evaluate for his second self build project.

Interview with Mike Coe

Back in 2011 Mike and his partner Lizzie moved into “The Autonomous House” – a self build project described as one of the UK’s most sustainable homes, which we featured in Episode 54. At the time they built it they were expecting to be living there for the forseeable future, but have recently made the decision to relocate to Scotland. Now that they’re looking to sell their house they’re discovering that finding a buyer for such a unique property is not without its challenges.

Visit Cropthorne Autonomous House as part of the Passivhaus Open Days.

The lure of one more project is compelling!

Mike has devoted a lot of time researching climate change, and his own feeling is that in the next few years the temperatures in the south of England will get far hotter. Approaching his 60th birthday he is also starting to get a sense of excitement at the prospect of taking on one more big project, so although it is with a great sense of reluctance to be leaving The Autonomous House, a move to the Isle of Skye and a new self build project is on the cards.

Using a conventional estate agent has not found a purchaser for this unconventional house

Despite having a couple of interested parties, using a traditional estate agent has not secured a buyer for The Autonomous House. Mike believes that it won’t be for another 15-20 years that people will really understand the value of a house like it, with many people being put off by a lack of understanding about some of the features, eg composting toilet, rainwater harvesting system etc.

“So I think the attitude is changing but I think it’s going to be some time before we have the level of awareness that perhaps they do in Germany where there are a lot more low energy houses, a lot more Passivhauses, people understand them, they’re not afraid of them. ”

With the conventional estate agent route not yielding any results, Mike and Lizzie paid to advertise on the Green Moves website, which by its nature attracts people who are genuinely motivated to buy a sustainable home. Through this they are optimistic that they have found a potential purchaser and are now in a chain waiting for them to sell their property.

Despite the systems Mike has built into the house, he explains that it’s actually a very simple house to live in. It might be different to living in a conventional house, but is no more difficult. It doesn’t for example have central heating systems and boilers to worry about maintaining, or complicated electrical systems to understand. He thinks that anyone with a basic degree of DIY knowledge and experience would be able to maintain it without difficulty.

Selling the house will come at a financial loss

When Mike and Lizzie built The Autonomous House, their plan was for it to be their home for the forseeable future. They didn’t build it thinking about potential resale value. Perhaps if they had, Mike says they might have been able to fit a bigger house on the site or done other things a little differently, to create a larger resale value.

Housing prices in Worcestershire have remained fairly stagnant since 2007/2008 so they have also been hit by property not being a reliable investment over that time. Mike explains that the only way to not lose money on the property now would be to remain there for several more years and wait for property prices to catch up. Being reluctant to do that, they have decided to accept that they will lose money on the house. He is conscious that, while they intend their new project in Scotland to be their home for the forseeable future with low energy and off-grid features, he will be bearing in mind potential resale values and maybe being a little more conventional, just in case!

“So in some senses it’s going to be a little more conventional and I’m not going to do things like have a whole house basement in order to store rainwater, because it’s a very expensive thing to build. So I’m keeping a little bit more of an eye on those kind of costs and I’m compromising a little I suppose but not very much. I’m compromising a little with an eye on possible future sale.”

The new challenge!

While Mike and Lizzie were looking for potential houses to buy for when they first make the move to Scotland, they were introduced to a plot which they quickly realised was going to be better than anything else they were going to find. With a great deal of financial manoeuvring they were able to buy it and are now looking forward to the new challenge that awaits!

The plot is on the edge of Portree, a principle town on the Isle of Skye, which although not large, does have a good number of facilities for its size. The land is a sloping site which will give them views across Portree Bay, will be close to south facing giving them the option of another solar heated design, and has very little likelihood of further development happening nearby. There is also a stream running down the site which may give Mike the opportunity to run a micro-hydro system which, while probably not justifiable in economic terms, is something he says he has always wanted to do.

The site from above – on the left behind the trees is the roof of a 3 bedroom bungalow that was included in the package

The site from below, looking up the hill

View from the croft, looking back towards the site and over Portree Bay

Find out more

Read the blog about creating The Autonomous House

Follow Mike Coe on Twitter

Transcript

Download a transcript of the interview with Mike Coe

Passivhaus Goes Personal

This is a video we have produced for the Passivhaus Trust which was recently launched at the Passivhaus Conference as part of a campaign aimed at self builders. If you’re a self builder and haven’t made up your mind yet whether Passivhaus is for you, this will provide you with all the clear information to help you with your decision.

The Hub update

Our second video from Buckinghamshire Passivhaus is now available for Hub members. This one is all about how it’s going to be built, with details of the PH15 system along with some of the designs, plus how it’s being positioned on the site.

We also have our second progress call where Hub members can get together to discuss challenges or other aspects of their projects. The recording of the call is available for members to catch up with at any time.

Our latest module in The Hub is all about reclaiming VAT to make sure you don’t miss out on that 20% benefit.

In 4 weeks we will be increasing the price of Hub membership, but if you join now you will pay at a lock-in price for as long as you continue to renew. Check out www.houseplanninghelp.com/join to find out more!

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November 2, 2016
HPH085 : 10 Environmental Design Myths – with Sofie Pelsmakers from UCL
Sofie Pelsmakers, environmental architect and doctoral researcher at University College London (UCL), busts 10 common environmental design myths. This also serves as a good introduction to The Environmental Design Pocketbook.

Interview with Sofie Pelsmakers

Sofie Pelsmakers is passionate about contextual design, with the focus very much on minimising our impact on the planet. She was inspired to write The Environmental Design Pocketbook after realising there was no single resource that had summed up the arguments and also pointed to deeper reading.

Download Sofie’s PDF

In this session Sofie is dispelling 10 environmental design myths. She has also put together this bonus PDF for further reading.

Myth 1: “Climate Change is in The Future”

With Met Office and NASA data showing that all of the UK’s warmest years have been in the last decade, it is evident that climate change is already here. So the notion that we’re designing for the distant future is wrong.

The job for designers is making sure that buildings in the future will still be performing to the standard they were designed for and that they’re fit for purpose. Ideally we should be designing buildings that take into account future changes in climate or that can be adapted if necessary.

How future climates may vary (copyright The Environmental Design Pocketbook)

Myth 2: “What if Global Warming is Not as Bad as Predicted?”

If we’re wrong about climate change then the worst that can happen is that we’ll have designed better buildings that function in this climate and in any in the future.

Copyright Joel Pitt

Myth 3: “Green Roofs – Are They Green?”

This depends on the kind of green roof, in which part of the country and how well shaded and protected it is. There isn’t one solution suitable for all situations in all regions.

Much of the sedum is imported which will have an environmental impact, and even more so if killed off from being used in the wrong position (perhaps being unable to survive on a thin roof in the south east of England during a drought) and needing to be replaced.

Sofie states the current fashion is of thinking if a building “looks green”, such as with green roofs, green walls, or renewables then surely it must be, however it is just not as simple as that.

An example of a biodiverse and intensive green roof (copyright bere:architects)

Myth 4: “Green Walls”

While they have aesthetically pleasing qualities, a massive amount of energy is actually used in circulating water and nutrients around the plants to keep them alive. Systems can fail because they’ve not been maintained properly, the plants are in very exposed areas, or exotic imported plants are used that are just not suited to the climate. With considerable resources and energy being used to keep them alive or replace them if they die, Sofie suggests a much more robust way of creating a green wall is to use plants from the ground up and along trellises and buildings.

A green wall at Paradise Park

Myth 5: “Micro-Renewables Such as Micro-Wind Turbines Are a Great Idea in Urban Areas”

Sofie feels that there is a danger in sustainable design of going towards gimmicky “look at me” type renewables. In fact the energy used to make and transit a wind turbine to site can actually be greater than the energy it will ever generate, particularly if erected in an urban setting where there isn’t enough consistent wind. And despite millions being spent on renewables there can be unintended consequences, for example in some cases turbines have even been switched off because of complaints about their noise.

The sustainability of wind turbines in urban areas (copyright The Environmental Design Pocketbook)

Myth 6: “Greywater and Rainwater – Is it Always Environmentally Sound?”

If your sole concern is about saving water then these systems will succeed in that objective. Depending on the system used however and when you consider the embodied energy in the extra pipework, the energy used for pumping, the chemical cleaning components etc, you could end up saving very little water for a great energy cost.

A far more effective solution would be a gravity fed system with short retention recycling which would not need the cleaning to be done mechanically.

Myth 7: “Eco-Measures Lead to Energy Savings and Reduced Bills, Right?”

Using a greywater recycling system like the example above, it is evident that bills could actually increase from the costs of energy used to pump the water around, clean it and feed it back.

An unintended consequence is that we think that eco-measures will save energy but actually in a lot of cases people then behave differently.

Myth 8: “Does a Zero-Energy Building Mean its Environmental Impact is Zero?”

While we may save carbon from energy generated onsite (and if offset with allowable solutions), a building has more environmental impacts which cannot all be measured in carbon (health, biodiversity etc.).

Also the current definition of zero carbon acknowledges that you’d have to build at low densities. This in turn makes public transport and walking to services less viable, and increases dependence on cars.

Myth 9: “If I Have Clean Renewable Energy it Doesn’t Matter How Much I Use”

There are around 27 million buildings in the UK, many of which are built to appalling standards. While a lot of people think that there’s no need to upgrade them if we can just decarbonise the grid, they neglect to consider that the high energy demand requires considerable money and finite resources for the substantial array of renewables that would be required. There would also be ridiculous amount of space required to enable those renewables to offset an energy-inefficient building.

[Tweet “Sofie Pelsmakers: “Energy efficiency should be the first consideration before renewables.””].

Myth 10: “Retrofit of Existing Buildings = Unneeded and Boring”

With such a large number of buildings built to a poor standard there is a fundamental need for them to be upgraded in order to meet our 2050 carbon budgets and to address the problems of fuel poverty.

Sofie feels that many architects find retrofitting unrewarding and complicated due to limitations such as expense and existing structure. She argues that actually it brings the architect back to the base principles of insulation details, airtightness and thermal bridging that are often forgotten.

Find Out More

Find out more about The Environmental Design Pocketbook

Follow Sofie Pelsmakers on Twitter (Sofie tweets so much great stuff!)

Transcript

Download a transcript of the interview with Sofie Pelsmakers.

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March 12, 2015
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.

Find Out More

Follow Cath Hassell on Twitter

Transcript

Download a transcript of the interview with Cath Hassell.

Please Connect With Me
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January 11, 2015