Ecobuild: Grey Water Harvesting

Notes from Ecobuild expo talks on Grey Water use:

  • Greywater is waste water from showers, baths, washbasins, washing machines and kitchen sinks.
  • Greywater reuse is the use of untreated greywater.
  • Greywater recycling is the use of treated greywater.

Key technical issues to overcome using Grey Water:

  • The age of the water..
  • Stagnant water generates bioforms leading to unpleasant odours.
  • User interaction.
  • Anticipating users bathing habits.
  • Low level of maintenance.

Ecobuild: An “air tight” building

A principal of modern buildings to achieve thermal efficiency and improved health is to make an “air tight” building .

The aim is to head towards and perhaps meat the Passivhaus standard of air change rate of no more than 0.6 air changes per hour @ 50 Pa. (UK Building Regulation Standard is 10m³/m²/hr @ 50Pa).

Then to control / manage the air, by a mechanical ventilation heat recovery system (MVHR) that exchanges inside air with outside air, BUT heat exchanges the outgoing air with incoming air, so you don’t loose the warmth.

The idea worries people, “I want to sleep with the window open ….”. But reading more and more about this, even sceptics rapidly find the air quality is better in these buildings than those with open windows. And, you can just open the window if you want to ! (eg in summer).

Notes from  the Ecobuild expo talks:

I’ve read elsewhere, that the builders being on-side re the thermal, sealed objectives is key.



Rainwater harvesting

If there is going to be rainwater harvesting:

  • “Green / grass” roofs may mean little roof water run-off.
  • It seems that people tend to either go for a Grey Water recycling or a Rain Water harvesting system, not both. Have to cost these both up.

Anyway, if there is going to be a rainwater harvesting system, it would seem that putting the storage tanks for this on the west side of the house could be ideal.

  • This side of the house should have little if any people traffic.
  • The roofs could all be sloped to drain to the west so that the drain pipes could flow down to a single rain water harvesting tank.

Eco Building Products: Spring health check for green roofs

Spring health check for green roofs

An extensive green roof has the potential to bring many benefits – such as saving money on air conditioning, supporting wildlife, increasing the value of a building and improving its appearance – but none of these benefits apply to a green roof that is poorly maintained.

Most green roofs are low-maintenance, but ‘low-maintenance’ is not the same as ‘no maintenance’. A little bit of TLC carried out this spring need not be time-consuming or expensive and will pay dividends.

Enviromat offers a competitively priced green roof maintenance service, but if you prefer to care for your green roof yourself, here are some reminders of what needs doing this spring:

1. Do a quick check to make sure that any waterproofing you can see is in good order, that fall restraint systems are in place and in good condition, and that walkways, etc are as they should be.

2. Remove any rubbish or fallen leaves from the roof.

3. Ensure all drainage outlets are clear and that rain can run off freely.

4. If you have pebble edgings on your green roof, pull out any vegetation that may be growing through them.

5. Check that you do not have any unwanted vegetation on the living part of the roof. Be on the lookout for tree seedlings and pull them out – their roots could damage the waterproofing.

6. If you have any bald patches on the roof, now is a good time of year to replant these areas. On a sedum roof, simply break pieces off healthy, well-established plants and push them into the growing medium. Keep them well watered and they will soon take root.

7. Apply fertiliser. Enviromat recommends using Nutrifusion Spring/Summer feed. Follow the manufacturer’s instructions carefully.

8. If no rain is forecasted, give your green roof a nice long drink of water. This will activate the fertiliser and help new cuttings to establish.

EcoBuild: Toilets (waterless urinal & sensor on water tap)

Two toilets and a commercial tap sensor stood out at the Ecobuild expo:

One of the efficiency and eco objectives is a house that is water efficient.

Two slides, from different sources on domestic water use / water consumption:

My initial straw polling, is getting a strong reaction to the idea of a urinal, let alone a waterless urinal, from  at least 50% of the girls reacting!

Waterless Urinal

This has the potential to drastically reduce the amount of water used in the house.

They are marketed as “clean, green, odour free and waterless”.

I had it all explained to me on the Odourwise and Twyford stands. The module that fits into the bottom of the urinal converts all uric acid to a form that prevents lime scale, clogging up the system, takes away the smell etc. It seems that urine and water are a big source of limescale and other loo waste pipe problems, hence trying to dilute this away with (usually) lots of water.

All you need to do, is a few times a year (depending on use levels) replace the cartridge. In this photo the plastic bit on the top is the device to extract the Odourwise bit so that it can be replaced with a new cartridge.

A google search reveals there are a few alternatives, so more research needed.

My current thought is a urinal in the bathroom  off the main living area and also one in the bathroom off the study.

Also on show at Ecobuild 2012 will be the Odourwise™ Waterless urinals. Twyford Bathrooms offers the revolutionary Odourwise™ Waterless system for two of its urinal ranges, Centaurus and Galerie Plan. Centaurus is the first hybrid urinal that is truly waterless, combining maximum water savings with enhanced hygiene. The cutting-edge Odourwise™ Waterless technology requires neither chemicals nor electricity, keeping it eco-friendly as well as economical. The urinal is also entirely rimless, making it easy to clean (both within and outside the bowl). Installed with the Odourwise™ Waterless system, Galerie Plan offers the same cost-effective and eco-friendly benefits as Centaurus.

Toilet Sink Taps to be Sensor Driven?

Why use your hands to touch the tap to get the water flowing, before you’ve washed your hands ?

Why have the water running when hands aren’t beneath the taps ?

I need to check out the cost and any other implications. I assume they use a tiny amount of electricity, but best to check.

Combine the Sink and Loo ?

This great combined unit captures (there is an optional bypass if you don’t want it to, eg if you’ve cut your hand) the water you use to wash your hand and then stores this to flush the loo. Integrated 1 unit grey water system.

BUT, £2,500 !!!!!

I’m pretty sure I can have an entire house grey water system for a similar amount.


Green Roof

The Silver Spray plan includes some flat roof areas that will have a “green roof”.

There were a wide variety of these at the  Ecobuild show. It seems there are lot of options in terms of:

  • What plants are in the green roof. All the way from tall grasses, shrubs to lower and thinner sedum matting.
  • The base system that the green roof sits on and in. These range from egg cup looking sheets to matting that the plants grow into.
The main reasons, beyond aesthetics seem to be the  biodiversity increase, sound and thermal insulation and rainwater absorption (with slow release).

I asked Robert from ra-studio about his experience with green roofs:

I have done a couple, one in Cornwall (Sea house) and one on the Lancashire moors!

Green roofs are often used to combat heavy rainfall, and stop massive water run-off into the surface water sewers.  With more and more people removing garden spaces (lawns etc) and replacing with hard paved terraces, the green roof system acts as a way holding the water back and allowing it to drain into the RW sewers far more slowly.

We used a Bauder roof at Sea House.  Bauder do basically 2 types of green roof system – an intensive and extensive system.
The intensive system is a fully blown grass roof system that allows you plant lawn, shrubs, trees etc up there, and due to the thickness of the soil (normally a min of 250mm thick), it is quite a heavy build-up.
The extensive system is basically a sedum mat that is the thin / lightweight solution.  It uses sedum / succulents in the form of a sedum mat (approx 25 – 30mm thick), and although the plants on the roof will take up some water it is far less that the full grass roof.
There is a drainage layer under the sedum mat, and any excess water that the plants don’t take up, is released into the drainage system.  See Bauder’s website

Roof Insulation

Under the green roof, there will still be thermal and water insulation. This a lot of other products were at the Ecobuild expo, “Stone Wood Slabs for a flat roof”.

EcoBuild: Thermodynamic Panels (Heat Exchanger)

Thermodynamic Panels

These black panels were on display:

These black aluminium panels have refrigerant fluid pumped into them. The heat absorbtion of the black panels changes this to a gas, that is sent to a compressor, which releases heat energy in the heat exchanger where the heat goes into the water. The gas then goes through an expansion valve, putting it back to a liquid before it goes back to the panel. (See explanation & figures below forum comments below).


  • 55 degree C water output.
  • Can provide 100% of hot water and heating, 24/7, 365 days a year.
  • Works day or night, as it absorbs heat energy from the atmosphere. It is presumeably helped when it’s sunny !
  • Works when temps are down to -15 degrees C
  • Can be wall installed, which would work well for the Silver Spray proposal.
  • Co-efficient (COP) rating of 4.5 to 7.
  • Distributed by Jewson.
  • 1 panel system (with the boiler and reverse refrigeration bits) is about £4,500.
  • Can have multiple panels in a “toast” stack. Expo figure for that was about £6,500.

Forum Comments:

  • “Looks like it’s a heat pump with a solar-assisted air to liquid heat exchanger on the outdoors end.” seems to sum it up pretty well !
  • “depending on the heat pump, it’ll be better (better COP) than an ashp in sunlight, but probably worse at night unless there’s much wind to move air across it, although it will have a bigger surface area than in most ASHP’s which will compensate for this to some extent. “
  • “It also has the advantage of not needing (potentially noisy) fans”

Also from the forum, from their N. Ireland distributor:

The system is not new technology; it is basically a freezer “in reverse” and like a freezer consists of a heat collecting panel(s), refrigerant piping and an integrated electric heat pump.  It is a clever application of well tried and tested technology that has been around for almost 100 years.  The panels are made from weather protected anodized aluminium and are not vulnerable to extremes in hot or cold. They are light, weighing only 8 Kg and may be mounted in virtually any orientation or angle.  It has been estimated that 25% of the energy absorbed by a panel comes from solar irradiation, the balance taken from air and rain. Both sides of the panel are available to collect energy. The company that manufactures the system is based in Portugal and to meet growing global demand they have just built a second factory reflecting their 25 year history of success with the product.

You can check them out at

The Energie system is fully scalable from 1 – 2 panels for domestic hot water, to 4 – 24 panels for central heating right up to 40 panels for large volume hot water requirements. Note that additional panels simply mean faster water heating times, not higher water temperature which is set to between 55 and 60 C maximum.  A typical domestic installation for domestic hot water will have a 250L cylinder with a single panel mounted on the roof.

The heat pump is integrated directly into the Energie cylinder so an existing hot water cylinder cannot be used in this configuration. For central heating and large volume hot water requirements the heat pump (Solar Block in Energie speak) is a stand-alone device. Energie cylinders are either stainless steel or enamelled steel and can come with an additional coil for connecting into a backup heat source if desired. Sizes range from 200L to 6,000L.

All Energie Thermodynamic Systems are accredited under the MCS scheme.

The system uses 407A refrigerant and doesn’t need topping up. The only maintenance may be the occasional replacement of the sacrificial anode in the cylinder should you live in an area with soft water.

Another point raised concerned the panel frosting over in winter. This is possibly best addressed by personal experience.  I installed a 300L single panel system in my home at the start of this year, and although there was some frosting in the very cold weather at that time on the top surface of the panel, the bottom side was clear, and we always had enough hot water. Eight months later we have never had call to revert to either our central heating boiler which has been turned off these past 5 months, or the small integrated immersion that comes with the Energie cylinder. I estimate from measurements I have taken that the Energie system has used an average of 3.6 KWh of electricity per day over the 8 months January to August for our 4-person household at a COP of just over 3.

Hundreds of Energie systems have been installed successfully throughout Ireland over the last 4 years and having come through last winter are well tested for the vagaries of the UK and Irish climate.

Finally some additional information as supplied by Energie can be found using the link below.

More Information from ThermoGroup


1. Aluminium Panels
Refrigerant fluid circulates through the panels and absorbs heat energy from the atmosphere. This increase in temperature changes the fluid into a gas.

2. Compressor
The gas then passes through a compressor and the temperature increases.

3. Hot Water Cylinder
The hot gas then flows through a heat exchanger in the Thermodynamic Block which transfers the heat into the water, which can be used for sanitary hot water, space heating or larger applications such as swimming pools.

4. Expansion Valve
The gas then passes through an expansion valve, reverts back to a liquid and flows back to the panels to
repeat the process.

Figures for Thermodynamic Atmospheric Energy Panels

I read or heard at the show, that increasing the number of panels increases the speed at which the system works. So I think you could add a panel to make the system work faster at grabbing the optimum conditions? (Need to ask them)

Air Source Heat Pump Vs Thermodynamic Atmospheric Energy Panels:

 Air source heat pumps  Thermodynamic
• COP of around 4
• Outputs of 6-18kW
• Outdoor noise pollution
• Requires regular maintenance
• Efficient to just below 0 degrees C
• Fixed sizes
• Fan assisted, low active surface area
• COP of up to 7
• Outputs of 1.7 – 53 kW
Silent outside
• Only one moving part
• Works down to -15 degrees C
• Total flexibility
• Active surface area of 3.2m2 per panel
 Standard Solar Thermal Panel  Thermodynamic
• Provides up to 70% of your hot water
• Must be mounted south facing for best results
• Needs backup from a boiler or immersion heater
• Needs sunlight – low performance in winter/night
• Can only assist central heating
• Fragile glass panels
• Provides up 100% of your hot water.
• Can be mounted south/west/east/north on a wall
• No backup required – Not connected to boiler
• Works in the dark and down to -15OC – 24/7
• Can provide 100% of your central heating
• Aluminium – tough, long lasting, anti corrosive
They can work on a north facing wall, but work best the more direct solar exposure they get.

Case Studies and Cost

Running Cost:


  • 4 bed house, one panel & 280 L cylinder, for hot water only = £109.50 pa
  • 3 bed house, 6 panels & thermodyanmic block for central heating only = £346.75 pa

So how much would a central heating and hot water system cost per annum ?
– those figures have an assumed electricity tariff of £0.14/kWh. If the system is part driven by my own solar panels, the cost would be reduced (although you need to factor in the capital cost of the solar panels.)

Purchase Cost:

Need to add in the cost of having it all installed and signed off to the level that’ll hopefully get the Renewable Heat Incentive.


Thermodynamic kits ship pre-gassed, ready for installation and include the following:

  • Thermodynamic Panels/s
  • Panel Fixing Kit
  • Hot Water Cylinder with Thermodynamic Block
  • 30m Copper Pipe
  • 30m Low-loss Lagging

The above thermodynamic kits are suitable for supply of sanitary hot water in domestic applications. Thermodynamic systems for Ambient heating or larger applications require a more detailed specification to ensure we provide you with the right solution.

I’ve emailed them for a rough quote.

EcoBuild: Photovoltaic, PVT Vs PV or PT

Photovoltaic Thermal:: EcoBuild Expo Update

At the Ecobuild expo, there were a LOT of companies who had photovoltaic elec or water heating systems.  Few were combined PVT (both electricity and heating water). So I started asking why. Speaking to those that make the panesl and installers / advisors the consistent reply was that the reduction in output of both systems was more than 50% down on what you’d get if each was stand alone. One company that produced PV and PT panels said that:

  • A PV panel could produce around 280 Watts  of elec, a PVT panel about 120 Watts
  • A PT panel over 200 (I think degrees) water, but only 40 degrees from PVT.

Yes, it’s still good to cool down PV panels, with ventilation, or even surrounding green roofing. But it seems that cooling them, by linking in pipes to generate hot water doesn’t work. It seems that the temp hot water panels work at is so high to be efficient, that takes out too much electricity production. Or you compromise the amount of hot water production by having the panels at a much lower temp. ie to be efficient they both operate at vastly different temperatures.

So that means looking at seperate systems for electricity production (PV), hot water productin (PT) and something for when the sun isn’t shining for hot water (for taps and heating).


EcoBuild: Air Source Heat Pumps

Air Source Heat Pumps

The installers / advisors to projects that were speaking at the lectures for self builders were all very positive about air source heat pumps in terms of how they work and how they stack up from an environmental / energy / sustainable point of view.

There are now automated systems for (for example) an air source heat pump to kick in when Photo Voltaic (PV) panels are producing more electricity than the house is using, and so at those times top up the water thermal store in the building. This can then be used for hot water or heating (under floor works at lower temps) at other times (if needed).