Ducted Air Intakes and Increasing Passive Ventilation In Vehicles

Air Quality Management Goals

The ASHRAE recommends that the air inside a human inhabited space should cycle 30% of air volume every hour. The lions share of energy expended in an HVAC system is traditionally conditioning the air coming in from outside to replace this air mass. Using heat exchangers, thermal mass, pressure differentials, and other natural features in a space to preform these tasks based on the passive impact of the environment will significantly decrease overall air quality management energy costs.

Thermal Chimney Effect

As an air cavity warms up it becomes more buoyant, causing the warm air to rise and create a vacuum behind it. This affect can be harvested to create meaningful passive air movement inside a space and is technically called natural convection.

See the source imageOne of the simplest ways to get natural convection in a vehicle is to puncture the roof at the highest point and at a lower point, preferably at a shaded point (underbody). By simply protecting the intake vents from direct sunlight and insect intrusion just simply adding a few vent holes will create a noticeable change in air quality. As the sun heats up the vehicle air will naturally be sucked into the vehicle and exhausted out the top. Adding a fan on the roof duct obviously adds to the effect, and the solar heat actually decreases the amount of energy required to run the fan. 

Creates a cavity on the roof as a plenum
A basic vent hood
You can further increase this effect by creating an airspace on the roof, called a plenum, and painting it a dark color. This creates a solar chimney effect by producing a hot zone which produces more suction the warmer it gets. One simple solution is to use a vent cover painted black to produce a serious differential. This cavity also provides a waterproof cavity that allows the roof vent to be open even in rain or other inclement weather. Puncturing a vent hood and ducting to the outside allows other zones to directly vent out without being drawn through the living space as well, which is how I prefer to ventilate non-living spaces such as under beds and inside cabinetry. The taller the vent hood is the more vacuum it will create. 

Image result for solar chimney
A wall cavity driven chimney
A more compact and effective method of producing natural ventilation is to produce a cavity that runs the entire height of the structure. By merely ducting a vertical cavity that accepts air from the climate controlled space at the low side and exhausts at the top the solar chimney can
produce MUCH more vacuum. This can easily be a cavity inside of an insulated wall, or just a ducted chimney much like a home downspout. You could combine both of these effects by ducting the chimney out the top of the vent hood. By placing intake vents all around the vehicle you can ensure that wind helps assist air through the space; there are various ways to direct intake air as well such as omnidirectional wind scoops.

Simple PVC ducted intake vents

No automatic alt text available.I've decided to duct my intakes with simple PVC pipe, which is vastly inferior to repurposed rectangle SUV vent which will be my future material for this. PVC will be run inside all cabinets and underneath furniture. This airflow is to combat mildew and mold growth while also giving me a central point to place an air exchanger, dehumidification equipment, particulate filters, and the like. 

Louvered metal insect screened vents are attached to the PVC pipe and run through the space directing air from outside into various air zones.

Trailer-Based Modular Plumbing System Plan

I was tasked recently to design an entirely off-grid plumbing system for an intentional community that housed 10 individuals. This project was only partially constructed but I thought some of the research done was interesting. Here it is presented with light editing, hopefully it is useful to someone.
Objective Statement

Currently we have immediate needs of a functional, self-contained, plumbing and water management system to support the project. This includes vendor provided grey and white water tanks, a kitchen support assembly, and a single bathroom assembly, and the following design decisions reflect this use case. At it’s very core, the proposed systems are the scaled-up recreation of boat plumbing systems. We are placing heavy emphasis on point-of-service processing, such as debris grating, in order to decrease our dependence on process filtering at the holding system.

Specification :

Design and implement a plumbing system that is housed entirely on mobile platforms. System needs to support the lives of 6-10 users. This includes a fully functioning bathroom and a kitchen. The holding tank module needs to be close enough to the entry of the space for servicing by our ‘pump out’ service, until such time as we find a way to do our own. Freshwater delivery, herein referred to as ‘whitewater’ is starting at 300 gallons per week. Do not mix septic and grey wastewater systems. Attempt to provide at least 5 minutes of non-shower use of the system ‘in reserve’ before a pump initiates. Dampen the noise impact of the plumbing system to a reasonable degree. Expect to purchase a handicap-capable portapotty shell in the near future and convert it to a second bathroom. Maintain a modular design approach and implement no techniques. Collate every component datasheet and create an installation protocol that conforms with documented requirements, while also creating a maintenance schedule. This document will serve as part of this effort.

Phases -

Due to budget constraints this project is being broken up into phases.

Phase 1 - Freshwater system active and circulating. Hot water is provided at point of service. Grey water is collected in a holding tank. Kitchen and Bathroom zone serviced.

Phase 2 - Recycling shower system installed. Second shower installed. Hot water low-flow solution implemented. Quick connect system installed.

Phase 3 - Black water holding tank system installed. Toilets activated, maceration system installed. Portapotty service cancelled.

Phase 4 - Placement of modules on trailers. Extension collection basins and pumps installed.

Project Milestones -
Finalize Feature Specification / First Draft Schematic
Populate BoM Feature Matrix / Mathsman Feedback / Final Draft Schematic
Finalize BoM / Assemble Installation Instructions / Final Schematic / Order

CSV System Description -
Currently I am building a csv file that describes elevations, diameters, lengths, closures, and materials for each length. We also need to describe the number of elbows and T’s (straight and bend/branch). This is being fed to a MathCAD dude for optimization. Once this is done we will be populating a worksheet that describes what diameters, materials, and locations for sourcing components against.

This description also includes an outlets and inlets description; describing pressure, diameter, gpm flow ranges, mins and maxes.

These descriptions and the maths will give us hard criteria for component features needed, which will give us guidance for filling the BOM.

Holding Tank System -
Holding tanks should be leveled on a platform in a space against the 'back wall/fence' allowing plumbing to stay concentrated against the back of the space. Tanks require vendor access and must be within 15 or so feet from the pull-in driveway; providing the rationale behind placement in the gravel to the left of the pull-in. Secondary sites for tanks include the right side of the pull-in behind the current 'kitchen bus'; which would limit future relocation of vehicles in the front end of the lot. Another more esoteric option is to create a vendor pump out station outside of the fence behind a lock box with access conduit running to the inside of the IBC's located just inside the fence. This installation would require breaking the visibility and sound barrier provided by the street-side bus-wall, and was rejected.
Holding tanks should be blocked for visibility if possible, with a simple enclosure being a likely option. Power service for pumps and sensors to the holding tank assembly is categorized as Critical, and a lack of power should indicate fault.

Freshwater tank is provided by the vendor and is filled 300 gallons once a week on a monthly service contract.
Septic IBC should be ventilated, nontransparent, and can be the smallest of the holding tanks. Following the UN refugee program guideline for amount of septic produced by a human and targeting a 10 person population onsite eventually, an absolute maximum of 336 gallons a week can be anticipated. This dramatically decreases with the inclusion of water saving design decision such as 'flushless' urinals.
IBC containers fed by slightly buried sump pump basins. One for black and one for grey water each. Each basin has a sump pump or ejector pump inside said basin that is activated by float switch. These pumps are disabled via overfill sensors in the IBC tanks to ensure no overfilling, also indicating fault. The septic basin should be as small as possible and serves primarily as a lift pump into the IBC from the horizontal run from feed line, and should be sourced as a vented sealed unit. Grey water basin serves as a collection point for disparate grey water sources as well as lifting pump.
Black water IBC should be installed with through-hole flushing spray nozzles allowing filtered greywater to be pumped through the nozzles cleaning the inside of the tank immediately post-servicing. This can be a manual or automatic feature. Nozzle can be rotating or static type mounted high in the tank, and shouldn't be operable without ventilation or pressure relief to avoid backpressure.
IBC containers should be fitted with specialty lids that allow sealed connection to liftpump intake pipe and a sealed accessible service hatch for contractor pumpout.
An optional faultstate response to greywater being full and blackwater having space is to send greywater to blackwater holding via spray system until greywater levels are lowered out of fault state.
Kitchen -
Sink is plumbed very normally to sinks via freshwater system. Insulated hot water lines deliver hot water from the hot system. Greywater from the kitchen is particulate filtered at the up-to-5 drains and gravity feeds downward towards the bathroom greywater collection system or is pumped from the sink to the ejector pump basin at the greywater holding tank.
Drainage could be assisted by including a waste processor/ garbage disposal as well, but sluicing and removing particulate still needs to happen.
Bathroom System Summary -
Shower -
Shower is outfitted with recycling shower system and low flow showerhead. Inside shower is a control switch of valve that initiates recycling shower. When activated water drained from the shower, and ONLY from the shower, is accumulated in an expansion tank via recycling shower pump. Hand valve control shuts off freshwater feeds and grey water outlet. A pressure regulated valve allows fresh hot water to be added to the system as required to keep the pressure up, which is pressurized by a small pump. A check valve between the pump and pressure valve ensures fresh hot water doesn't drain into greywater. A check valve after the toilet reserve tank ensures other greywater doesn't drain into recycling system. (refining this based on the design of the showerloop open source design).
Sink - Standard sink is plumbed already and just needs a low flow aerator. Connects to ejection system on the wastewater side of the check valve.

Toilet -
Low flow rear-drain toilet is installed parallel to rear-mounted macerator outside of bathroom on stand. Urinal is also piped to macerator unit via 2in port. Other ports are sealed. Outside mounted greywater reserve tank/expansion tank used in recirculating shower is used to feed into toilet flush reserve, falling back to freshwater in the toilet reserve tank as needed. When recycling shower control valve is in the 'off' position the recycling system gravity drains into the toilet water reserve tank. Toilet bowl is always filled with water from the reserve tank with no direct freshwater inlet. Reserve tank has a float sensor for indicating when full, closing the reserve tank inlet via solenoid and forcing further greywater into the ejection pump system via shower drain. Float sensor also indicates when levels hit 'low storage' and open a solenoid valve to release enough freshwater into the reserve tank for 'a few' flushes.

Optional Urinal changes some but not much of this calculus and is tapped into the reserve tank just like the toilet if it flushes. Is connected to the macerating pump elsewise.

Macerating Pump-

Initial maceration unit was planned to be a SaniFlo unit. Somewhat exhaustive research into how this unit functions has opened up the possibility of recreating the unit at a fraction of the cost. Home-made maceration units can be found on youtube and in RV forums, being gravity fed by a black water system and macerated by a garbage disposal; which has a BoM of around $100. This is an interesting system but ignores a few problems that are somewhat easily rectified. First and foremost the grinding unit in a garbage disposal is NOT a pump and any forward head pressure created by the unit is a combination of incidental pressure from the centrifuge and the reverse pressure from the gravity feed of the black water tank. One could easily attach a collection vessel to the outlet of said garbage disposal that includes a sump pump, giving meaningful pressure to the output in a sealed unit. Another problem with the ‘garbage disposal’ unit is that it is always on, which can ALSO be solved by having a secondary vassal with a sensor that indicates fluid level to initiate grinding pump.

Lets look at an example unit, shall we. The SaniPro:
The macerator pump is actually an impeller with a slightly extended motor shaft, creating a single unit that grinds AND pumps after attaching standard blender-style stainless cutting blades to the shaft. The impeller picks up from the basin and ejects to the outlet. The pressure vessel (#14) is a sealed unit that provides the on/off switch mechanism, hidden behind a membrane. Impeller-driven pumping action ejects materials from the bottom of the motor out via #8. The cutter is only run when the impeller is active, meaning the colander tube holds solids until enough liquid is collected in the larger basin to trigger the switch.

So, I propose purchasing an impeller pump with an extended shaft, attaching some grinding stainless steel blades via a likely woodruff cut shaft. I propose placing it in a basin with around 2 gallons of capacity, installing a float switch triggered at 1.2 gallons and air vent. Additional inlets into the system can be fed into the chopping colander or, if filtered for sediment to the impeller spec, directly into the tank.

Freshwater System -
Freshwater is pumped out of the holding tank by a pump that pressurizes the entire freshwater system to 45psi after pulling fluid through a particulate filter. Water pressure is normalized via accumulator tank creating at least a few gallons of use without initiating the freshwater pump as well as removing water system choppyness. Immediately after the accumulator a check valve is installed after a 50psi pressure relief valve and an optional garden hose attachment. The pressurized line then splits into cold and hot water lines. The hot water line runs to the fresh hot water system. The cold water system runs to a manifold and is split to separate service zones, in this case being the kitchen and bathroom. This manifold should have at least one if not a few sealed ports for later expansion, and at least one garden house connection.
The shower recycling system is kept pressurized to 45psi via freshwater intake where required to maintain pressure.
Hot Water System-
Hot water system is pressurized by the freshwater system. Hot water system starts at a check valve to ensure hot water doesn't infiltrate regular freshwater system. Instant-hot water heater is propane fired. A possible solar thermal heater loop connection is left as two sealed connections in the line between the water heater and the hot water check valve with a shutoff valve between the two connectors, making this valve a temporary hot water shutoff and an eventual solar heater bypass valve. A hot water manifold provides distribution to the shower, shower recycling system, sink, and kitchen via insulated line. This position can be reversed with the hot water tank installed at the kitchen and insulated line run to the bathroom; or the kitchen can have it's own water heater if desired (this is not an idle thought, it would be preferable for the kitchen hot water to be hotter than the rest of the system). Hot water should be set to 110 degrees, allowing comfortable hot water to be available using only hot water valves. Because of the low flow of all fixtures care must be taken that enough flow is happening to initiate the hot water heater. Hot water heater temperature can be increased linearly based on the flowrate of the lowest fixture in our system. (eg: if the water heater has a .5 gpm flowrate and a .6gpm faucet is opened as 'only hot' the heater will engage, but if the valve is opened for half cold half hot only .3gpm would flow through the water heater and would NOT initiate)

On the New American Dream

In the New American Dream, mobile life is about more than just phones. It's about vans, too. 

A white G20 van parked in a sunny lot in front of colorful trees
Any van could be hiding a home 

When it comes to glamorizing a traveling way of life, there is often a lack of real discussion about the socioeconomic conditions that lead people to live in vehicles, the stereotypes they face, and almost no reporting about what it is actually like to live in a vehicle. There isn't a cohesive place to learn practical steps and warnings.

Millennials, specifically, are often mentioned as a group that is embracing a vehicle living lifestyle. 
Many millennials have convinced themselves that living out of vehicles is the new American Dream partially because it's so far from the previous ideal. They reject rent seeking behavior more strongly than previous generations. Not being able to afford a house, having useless degrees, working for free, taking up as little space as possible, living in a van, sleeping in the parking lot at the office… that is a stereotypical Millennial. No doubt, lots of people choose such a life for fun, travel, because it sounds cool, to reduce their footprint and costs, or because it IS their dream, but often, the reality of why and how most people live in their vehicles stands in stark contrast to the stereotype of a young, healthy Millennial embarking on an adventure.

A 2011 report by the National Alliance to End Homelessness found that among those not living in shelters, almost 4 in 10, or 243,701, were living on the streets, in cars or abandoned buildings. It's hard to get an accurate count of how many homeless are living in cars, due to the way that homeless surveys and counts are conducted, and the obvious reluctance of people to self identify as vehicle dwellers.

There are a lot of children living with a parent, often a single mother, out of sedans and minivans.  A lot of displaced people, many with disabilities,  and otherwise disenfranchised people live in vehicles and a car may be their last choice of how to live. Industrious people with larger vans and the skill sets needed to make upgrades to their vehicles are way better off than three people in a sedan, but reliable information about how a person or a family actually goes about improving their vehicle living situation is hard to come by.

There is no appropriate infrastructure to support people living in vehicles, either. People have little idea how to go about vehicle living, since there are few resources to learn from. Cities desperately need public bathrooms, shower facilities, optional designated parking areas, and garbage collection, for both people who are homeless and vehicle bound people alike. Some places are attempting to work with their local communities to supply designated parking, though it is often presented as  a mandatory place to park, with a non compliant occupant being subject to fines, impounding, or other legal measures.

A blue and white sign shown in front of a row of parked cars displays an image and text that says "No Sleeping".
© Copyright Chris Downer
Many cities across the country have passed laws making it outright illegal to sleep in a car. A 2014 report by the National Law Center found, in a survey of 187 cities,  a 119 percent increase in such laws since 2011. There is plenty of hostility towards van dwelling culture, and vehicle living in general, from those in traditional dwellings. There's no better way to spread shame than making people feel like their existence is unlawful, or worse, immoral. Some attitudes are changing, with the tiny house movement has somewhat changed the cultural outlook on mobile living, but unless they are driving around a trailer that looks like a miniature version of a standard house, or are vacationing in a decked out RV, people are looked down upon for going about their lives the only way they know how.

(In response to: Living Out of a Van Is The New American Dream )

Passing On Sarasota Florida

Betty's Hot Wet Yacht Slots

I saw an ad on craigslist with a marina for rent. "22 slips for 3700/mo in Sarasota FL, texts work best". Suddenly I'm swimming in a sea of red flags and shudder at the prospect of trying to enter an arrangement with someone that thinks initiating discussion about renting an ENTIRE MARINA is best done over sms. I shout out at him, he shouts back that he doesn't know anything about anything and doesn't want to find out for me. "I'm going to have to be ready to go before I deal with this guy", I think to myself. He didn't even know how deep the slips were, yowza!

Better Put Eyes On It

I have a guy that needs to start a company in the area anyway, and investigation shows the marina is part of a large multi-unit property. I convince my associate to do a scout around for me and find the cheapest property in the landlords portfolio. I want to spy on that marina!

Forward Scout Location Rented

So the landlord enters arrangement with a fellow willing to split the space with me for a few months while I scout around. I spent some time talking to neighbors and getting an idea about how the community would handle a bunch of transhumanist boat squatters with magnet implants and sexual interest in D-Rings. The marina itself was poorly maintained and the community would hate us, without a doubt. I spied and watched the boat traffic and the people traffic and a little on the radio traffic, and the AIS traffic nearby; for a month darn near!


The marina was built in 2001 as part of a restaurant that wanted to cater to boat folk. It apparently didn't work out. As you can see in the videos most of the slips are empty, the landscaping overgrown, and apparently up to 6 craft may be considered abandoned (and maybe collectible with the property, with some work). The property is fully private and as such falls into a neat loophole the doesn't require USCG inspection, for good or ill. There was hand-wringing with the neighbors from day 1, including fake 'we will tow your car' notices put on windshields and passive aggressive questions about the holidays.


Unfortunately I deem Sarasota Florida to not be where I want to start a boat community. I will gladly pass the address to anyone interested if you email me. For now, it's off to New Orleans by way of Mobile Al. There are a lot of great craft in NOLA and a TON of great spaces in Mobile. I got a friend set up with a new business that might sink it's toes deep and sprout an eCommerce operation that I can still work with over time and saw a bunch of cool birds. This is a place to sell boats and not to buy them, but high end accessories might be common here.

Marine Surveyor Hands-On Forensics Lab Rant

One of my current projects is creating a map of known boat graveyards. Establishing a boat workshop in an area that is dense with such businesses makes a lot of good sense and creating relationships with such businesses is high on my reconnaissance priorities, along with touring dozens of marinas and yacht clubs. Once I find a boat graveyard with an appropriate attitude towards indiscriminate hull core sample collection and liberal application of chainsaws I have an idea. I would like to hire a marine surveyor to do a hands on lab on preforming hull forensics and grading, including demonstrating discovery techniques.

What Does A Marine Surveyor Do?

A marine surveyor is likely to be preforming your pre-purchase survey, first and foremost. This is an independent study done on a craft at your request, usually charged by the foot of the vessel. I've been ballparking the price at 15-20$/foot but obviously ymmv. This person is trained in the mystic arts of 'tapping a hull and knowing what a bad sound is', recognizing symptoms of problems, and gives a complete report on condition. They also preform other various tasks including inspecting cargo and other official services. 

Who Died And Made YOU A Marine Inspector?

A marine surveyor also makes money preforming such services and the road to being an official inspector is extremely easy. A written mailed-in test and $150 seems to be the entry level for those aspiring to take the mantle. Reputation seems to be EXTREMELY important in this field but as always it is hard to say for sure. The subject matter itself is very accessible but people with dozens of years hands on experience aren't. You have to know a lot about boats, that's for sure!

A Marine Inspector Certification Curriculum Would Be Useful

I'm tempted to say that I would want to do a one on one session with an inspector, cutting into hulls and decks investigating strange bulges and cracks in some boat graveyard. I want to sand the paint off the bottom of more than a few different wood hulls to learn what I would learn. I have learned long ago that such a session without a curriculum and more than 3 people becomes a disaster. I personally will cram for months before doing something like that but many people cannot. Using an established curriculum out of a community center to get everyone up to speed before outings with our inspector for hand on labs would be my preferred SOP if operating out of a hackerspace.

Other Possible Hands On Lab Opportunities

Plan B, which is the most liberating, is to take shitty work at a string of boat recycling operations and spend some time destroying yachts. If I want to see what different kinds of balsa-cored hull failures look like from the inside I can probably even nail down a simple internship for access. Even dumpsters full of post-removed panels would be invaluable. I want to see what the actual delamination looks like from different kinds of water ingress firsthand before I ever have to worry about it, that's for sure! I'd settle with being able to study the post-compacted cubes of yachts after they went through a 2 story shredder. I'm also VERY interested in seeing what different kinds of wear patterns form on the main drive shafts.

Just Sounds Like You Are Short-cutting A Lifetime Of Boat Exposure

I AM! Famous last words, INDEED.

Bilge Basics

What is a bilge?

Basic Sailboat Bilge System
The bilge is a chamber at the lowest point of the ship that resides under the waterline. Water that is spilled in the craft, makes it past a through hole fitting, or makes it past the vapor barriers during rain all makes its way into the bilge via engineered channels. This is also often where grey-water ends up, though usually a septic tank is in place to catch water from the head.

All boats take in water and all boats have a bilge to collect said water. The stations and bulkheads often have holes in the bilge area to allow fluid to flow to the lowest point. This is where the primary pump is located. The pump then pushes the water up above the waterline and out an exterior drain through a seacock.

How does a bilge pump work?

Basic Bilge System Components
Modern boats usually have two electric pumps and a manual pump. The bilge pump is a class-A critical system and usually has a second pump as a backup, often running off it's own backup battery. The manual pump is in place as a last resort in an absolute emergency. The pump has a float sensor much like a toilet that detects when the bilge is full enough that the pump can initiate. When this happens the pump begins moving fluid out the outside drain hole and into the water.

Environmental Concerns

Typical Through-Hull Seacock
It is against the law to pump black water or oily discharge into the public waterspace. Cleaning, treating, and segregating fluids that can contaminate the environment are absolutely critical. This concern has driven the development of numerous waste treatment systems to be placed inline to manage bilge contamination. As one could imagine such systems vastly complicate the bilge.

Bilge System Importance

There is NO MORE IMPORTANT SYSTEM than the bilge management system! It is expected for you to maintain redundancies, functional alarms, and backup power to ALL bilge systems! If your bilge monitoring or management system fails you can VERY easily lose your craft to the inky seas.