Rooftop Harvesting
Table of Contents
According to a South African case study, "Small, local solutions can crack water crises"
Before you get started on any project, always be careful to check your local legal codes and policies. Some types of water harvesting are forbidden in certain places for a variety of reasons.
Some water capturing methods may pose a hazard if they overflowed or broke, so proper site investigation and materials should be used.
North America
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Learn about which activities use the most water, to develope a plan on curring your own water footprint. In many cases consuming less will have a greater impact than harvesting water, though water collection may be your first step in your water conservation journey.
How safe is roof-water to drink?
Rainwater Research in Australia & New Zealand This research shares a lot of information about the basics of how beneficial increased use of collected rain water would help fulfill our water needs, and that as long as the suggested safety measures are followed "You are more likely to contract illness from drinking mains water compared to rainwater." then it explains the main sources of contamination and disease including lack of proper maintenance. "In South Australia, 42% of residents mostly drink rainwater in preference to mains water without any apparent effect on the incidence of gastrointestinal illness (Heyworth et al. 1998)."
Types of Rooftop Harvesting
There are several ways to harvest water on a roof, these include:
Air Conditioner Drip
Blue Roof
Green Roof
Hydropanels
Turning the Roof into a Condenser
These work with two different methods.
Condensation of atmospheric water into liquid water, which can then be stored in water butts or cycerns.
Capturing water directly (or snow which later melts into water). Either:
Storing the water for later release or use.
Watering plants that grow directly on the roof.
Air Conditioner Drip
One simple and cheap way to harvest water if you already own or work in a place with an air conditioner, is to divert the condensed water that drips out into a flower pot or flower bed.
Life Expectancy: A portable AC unit may only last 5-10 years, while a home unit is expected to last 20-25 years if properly maintained.
Pro: Simple solution of diverting condensed water to plants or a container, instead of letting it go to waste or causing damage to any structures it might drip on.
Con: Relies on a functioning air conditioner, which costs money, and produces dangerous emissions: both air pollutants as well as excess heat.
Solution: Switch to a green energy provider if possible to reduce emissions, and try to supplement your water harvesting options, so you don't have to rely on an A/C for the small amount of water it provides.
Fuel Types: Electricity and refrigerants which act as green house gases.
Blue Roofs
"In the past, blue roofs were conceived as storage tanks for rainwater harvesting. Today, they form part of SuDS best practice and are designed to facilitate controlled attenuation following heavy rainfall or storms. Blue roofs are suitable for a wide range of building types from domestic to commercial. They place storm water attenuation within the building footprint, making them ideal for urban environments where ground space is limited. Blue roofs can be situated above the waterproofing membrane in a warm roof system or above the water flow-reducing layer in an inverted application, at both roof and podium levels. There is a case to be made that green roofs are a form of blue roof, because they hold water and control run-off; but green roofs cannot do this in a truly controlled way such that the attenuation capacity can be relied upon to be available for a statistically derived storm event. Specifiers may like to consider the hybrid blue/green roof, which combines the aesthetic and ecological benefits of a green roof, with the high-performance water-attenuating properties of a blue roof." - https://architecturetoday.co.uk/roofing-in-detail-blue-roofs-best-practice/
Life Expectancy: 10-25 years, but some components made from certain materials can last 50-100 years. Green Roofs are expected to survive for 40-50 years.
Pro: Captures precipitation that might have otherwise contributed to run off and flooding.
Con: Relies on precipitation, meaning it may be unreliable in drier climates.
Solution: People who receive seasonal rain should build ample storage space to help capture as much rain as possible, ensuring more water will be saved for later in the year. They may also want to consider other options such as a well with recharging infrastructure, a grey water system, etc.
Fuel Types: Water Cycle + Gravity
"Green roofs are being increasingly used in urban areas where space constraints limit the use of other stormwater management practices." - EPA: Soak Rain Green Roofs
Green roofs need to be installed on roofs pitched at no more than 30°.
These can serve a number of purposes from increasing pollinator or veggie space, to reducing pollution and run off into our water ways. They can even help buildings stay slighter warmer in winter but are better at keeping things cooler in hotter months. According to this source "it is quite common to harvest water from green roofs in Germany and Switzerland." Thought some designs function as zero discharge sites, where "All water is reused within the development, either to irrigate intensive green roofs and landscape at ground level or is used to flush toilets throughout the development."
Green roofs can absorb up to 70% of the water that lands on them. So if you want to harvest drinkable or reusable water, then these may not be the best choice. However they will still preform the other functions just fine, and are a great solution to helping reduce flooding or run off.
Life Expectancy: 40-50 years.
Pro: Captures precipitation that might have otherwise contributed to run off and flooding. Increases biodiversity. Reduces energy costs associated with heating and cooling buildings. Extends roof life. Reduces emissions not just by reducing energy use, but the plants can sequester greenhouse gases.
Con: Relies on precipitation, meaning it may be unreliable in drier climates. Plants need a small amount of care, including occasional trimming, removal/replacement of dead plants, and removal of invasives. Water collected by these roofs may not be appropriate for drinking or other domestic activities.
Solution: People who receive seasonal rain should build ample storage space to help capture as much rain as possible, ensuring more water will be saved for later in the year. They may also want to consider other options such as a well with recharging infrastructure, a grey water system, etc. Special filtration will be needed if people want to drink water collected from green roofs.
Fuel Types: Water Cycle + Gravity
According to this article "There are three basic types of green roof: intensive (thick), extensive (thin) and semi-extensive (somewhere in between).
Intensive systems consist of a thick layer of soil (50-200mm+) in which a variety of grasses, herbs, flowers and shrubs can grow. These need to be accessible gardens (for maintenance) and can even be used as a recreation space. They provide a valuable habitat for wildlife but place significant weight on the building and need substantial roof support. They offer good insulation and better water absorption than the thin types, but need a lot of care.
Extensive green roofs are generally made up of a shallow layer (20-100mm) of substrate planted with low-growing, stress-tolerant grasses, mosses and sedum. These lightweight systems require little maintenance. The insulation quality is relatively low and extensive systems always incorporate conventional insulation.
Semi-extensive Systems have slightly greater depth than extensive systems (100-200mm) but constructed on the same principles to allow for a greater diversity of plants. It is also relatively low-maintenance."
Hydropanels
These can be set on the ground or on rooftops.
14:06 minute video about solar-powered, rooftop condensers.
Source Hydropanels from Zero Mass Water These 350 lb water harvesting panels contain solar panels, an air filter, a mineral cartridge which adds calcium and magnesium, and a 30 liter water collection storage tank, which can be connected to a pipe which can be connected to your home spigot. A 2 Hydro Panel Install can cost between $5,500-$6,500, with shipping from Arizona, USA. The panels can produce up to 8 liters of water per day. They are warrantied for 15 years, and need around $100 of maintenance work every 5 years to replace the air filter and mineral cartridge. There is an app to monitor how the panels are working, for example how much water they are holding. These should work where outside humidity is anywhere above 10%.
Cons: These can be noisy, but have a quiet mode to reduce the fan speed and noise of the fans, but consequently this reduced water production. The mineral packs can also create a strange citrusy flavor, which is said to subside after a few weeks. During freezes the panels go into hibernation, which turns off the pumps and completely stops access to the drinking water.
Life Expectancy: Warrantied for 15 years with repairs/maintenance ever 5 years at roughly $100 per service.
Pro: Uses sunlight and atmospheric humidity to condense water out of air.
Con: Requires solar energy, meaning they may not work during the night or in cloudy weather. Requires humidity, so may not work properly in particularly dry climates.
Solution: Consider pairing this system with back-up options such as rain barrels, a grey water system, and/or a well with ground recharging infrastructure.
Fuel Types: Solar Panels
Additional Equipment
Rain Barrels/Butts & Cisterns
How to Install a Rain Barrel in Under an Hour, for Less Than $200 This step by step guide encourages you to check your planned installation site before buying parts and getting started, so you can find out ahead of time if the area is unsuitable for any reason (for example slope, plants, pipes or other things). Uses US metrics.
How To Install A Water Butt Explains solutions to attractive vs functional design needs, including for small gardens. Uses standard metrics/Non-US. Includes tips for maximizing your water savings while watering plants.
How To Install Your Rain Barrel (PDF) simple diagrams and instructions for installing a barrel and what the important parts of the barrel are (in case you are making your own) from the Conservation Foundation.
Rain Barrels and Cisterns Described the practical features and functions of each, talks about material options, and includes helpful diagrams. Provided by the Low Impact Development (LID) Urban Design Tools Website
Life Expectancy: 20 years.
Pro: Safely stores rain or grey water for later use.
Con: An turn into a breeding ground for mosquitoes, or be contaminated with dead animals that can fall/get trapped inside. I've found dead frogs who might have hatched but not been able to get out. Dead leaves can build up, leaching tannins into the water.
Solution: Install fixtures that will help keep wildlife and leaves out of the system. Make sure to clean these to prevent plugging and backups. Empty and clean out the container periodically.
Fuel Types: Water Cycle + Gravity
Alternative At-Home Water Harvesting Options
Water Recycling
Grey Water
Simple Greywater Systems For Your Home "A greywater system is used to take water that has already been used from places like your laundry, shower and sink and divert it to use in another purpose like watering gardens or landscaping instead of flushing it down into the sewer. Greywater is different from blackwater (aka sewage) because while it may have some residuals like dirt, hair, grease, etc from it’s first use, they aren’t toxic to the environment and the water can be reused in some applications." When using a grey water system for irrigation, it is important to be very careful in choosing "bath soaps, used homemade shampoos and biodegradable dish soap so as not to damage the soil, plants or watershed." Link talks about legal issues, installation costs, and design elements such as filters.
Toilet to Tap Water Recycling
Toilets can use grey water, function without water, or be a source of water depending on the type you choose, and the infrastructure around it.
Tools & Resources
Landscaping Know-How
This may give ideas for how to capture and redirect water on the land, which can integrate well with rooftop water harvesting.
Greener LAND "This tool helps you decide which landscape interventions are best suited towards landscape restoration for the landscape you operate in. Start by selecting the characteristics of your landscape on your left."
Organizations
International
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
Africa
Warka Water "Every drop counts" To date they have worked in Ethiopia and Cameroon.
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
Asia
India
Rainwater Project "So far, Rainwater Project has restored six historic water structures in Telangana — Kokapet Well, Goshala Well, Kondapur Well, Gachibowli, Baaram Bavi and Bansilalpet Well." "It also offers rainwater harvesting and water conservation consultancy services for individual homes, gated communities, farms, resorts, schools and other institutions." - Kalpana Ramesh: The architect leading restoration of Telangana’s historic stepwells
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
Europe
UK
North America
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
Mexico
Isla Urbana "has designed an environmentally, socially, and economically sustainable rainwater harvesting system that collects and cleans rainwater for households, schools, and health clinics.
The system is inexpensive, easy to install, and provides individual residences with about 40% of their annual water supply. If implemented on a large scale throughout Mexico City, this simple technology could provide 30% of the city’s water and help give a sustainable water source to the 12 million Mexicans who lack access to clean water."
USA
American Rainwater Catchment Systems Association (ARCSA). Offers trainings and accreditation for rainwater installers. They also have a comprehensive list of rainwater resources here.
DigDeep "Water-storage barrels with pumps or household rainwater catchment solutions to reduce the reliance on single-use bottled drinking water in Chichiltah, NM, supported by community education around plastic pollution and sustainable alternatives to bottled water."
Watershed Management Group. (Tucson and Phoenix, Arizona). Offers classes, a “water harvesting coop” and more.
Oceana
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
South America
WASH "curriculum has been developed and integrated in schools (Shikshaniketan, Residential Bridge Schools & Solar Bridge Schools) run by Barefoot College International. Every year, new activities and methods are included which makes learning interactive. Area covered include Water, Sanitation, Health, Hygiene and Environment."
Maps
North America
USA
Stormwater Management and Restoration Tracking (SMART) Tool (Interactive) Tool tracks storm water management practices in the Chesapeake Bay Watershed which spans, Delaware, New York, Pennsylvania, Virginia, and West Virginia
Grants & Funding
Oceana
Australia
Western Australia
The Sustainability Grants Program (in the City of Cockburn) "offers funding for projects related to six sustainability themes. Open to small businesses, schools, not-for-profits, and collective households, successful applicants can receive up to $4,000 for their project."