Efficient Unified Bathroom Theory

Hyperminimalist Bathroom


A meta-efficient design for a bathroom.


Water in the bathroom: use filtered rain water, otherwise filter water very thoroughly (i.e. remove: chlorine, heavy metals, pesticides, pharmaceuticals, VOCs, radon, and other contaminants).

Channel greywater into a garden.

Air Purification

Purify the air using indoor plants.


Use radiant heat through the floor. Heat via direct sunlight. Otherwise: from direct, renewable source (i.e. wood or sunlight).

Water Heating

Heat water using a point-of-use instant water heater thus reducing water wait time and external tanks. Heat using a renewable source.


Use low-flow aerators, use foot-pedals to control faucets for increased hygiene, water reduction, accessibility (children, elderly). See previous post for more information.


Contain shower heat by sealing entire shower (thus reducing the need to heat water).  Use an ultra-low-flow, aerated showerhead. If the water is not filtered, remove chlorine using vitamin C. Heat water at point-of use, reclaim heat after use. Use non-slip surface reducing injuries (i.e. textured tile). Incorporate handles for accessibility. Make faucets reachable by children. Overall use open shower design.


Choose optimal towels.


Choose optimal soap but incorporate dispensers to converse.


See shower principles. For a tub, recommend an ofuro is recommended, specifically one made of Alaskan yellow or Port Orford white cedar: aromatic, repels bacteria. Or ceramic. Dead sea salt most optimal for bath.


A toilet that combines squatting, cleaning with water (bidet function), urine separation, feces composting (sewer-free). Use sewage to produce biogas (fuel). See my article: The Three Fundamental Flaws Of The Modern Western Toilet.


Natural where possible (suntubes, skylights, opaque glass windows) otherwise use meta-efficient lights. Use LED task lights (motion-sensing), and ambient lights (LED bulb preferred –see 75 watt LED equivalents). Also, use low-wattage LED motion-sensing lights for night-time trips (so as to not wake others).


Design for comfort and sufficient privacy.

Building Materials

Non-toxic, natural, waterproof, mildew-proof. Tile, naturally-treated wood, glass, stone.

Floor Coverings

If needed should be removable, washable.

MetaEfficient Minimalist Bathroom


Smooth, uncluttered surfaces to optimal cleaning.

Optimal cleaning products: non-toxic, organic. Scents: essential oils.

10 thoughts on “Efficient Unified Bathroom Theory”

  1. @Matt: there’s a good reason why it looks twice as long – it’s two units! Interestingly, it looks like they’re parallel paths, which would seem less efficient. The water coming from the lower exchanger would be colder than the water from the upper exchanger. Probably the installation required more flow than the standard unit allowed.

    I don’t get the drive behind open showers, though. It seems like a fully enclosed shower stall would be more efficient. Is it simply an aesthetic / indoor environmental decision?

  2. Matt the Engineer

    [John B] Here‘s a picture of a drain heat exchanger (this is actually about twice as long – and therefore more efficient – than the one’s I’ve seen). It would be a tough retrofit, but easy to install in new construction. All you do is run your cold water line through it to your shower, and you’ll need to use less hot water.

  3. It seems like a lot of thought is being put towards drawing humidity out of the bathroom. The question is, why are you letting the humidity get there in the first place?

    Seal the shower space, making it air-tight. That way, the air reaches saturation sooner, and you lose less heat to evaporation on the way from the showerhead to your skin.


  4. [Matt]:
    I didn’t know they sold smaller heat water exchangers for the waste heat. The whole house ones still don’t make much sense to me.

    Yes, electric heating is a waste of power; however, gas/electric water heaters with tanks wastes power too. Gas is dangerous and requires venting etc unless you put it outside the house (I’m currently working on a wood heater that is outside the house.) I’ve always figured on pre-heating that water source to room temp by greener methods later on. (This reduces heating load on the electric heaters.) I lose a lot from my tank water heater today; the copper pipes from it act as a heat sink even with all the insulation I added and its losing heat 24/7. I’m not sure of stats on this area yet.
    Instant gas heaters are a problem because of venting; long runs of hot water as a work around end up losing heat in the pipe and adds to the amount of piping. I’m not convinced that the greener alternatives are “optimal” in this use case. (again, I’m only thinking it be used to raise above room temp; a ‘cold’ shower for me is around room temp.)

    Heat pumps are cool but are costly and take land to install (I got a pro quote on it;) probably best to put in during house construction. If you get one, it would be to heat the house and raise water to room temp; don’t think I’d put in two of them due to the high cost… (I want one but I’ll be fine on wood.)

    [Justin and Matt]:
    In the winter; I need humidity. plants work fine but the bathroom could be adding to it. In summer, I want it gone– in which case a fan and vent is perfect because I don’t want the heat either. The issue with a heat exchanger is a problem with the moisture build up and condensation– but is somewhat moot because of the seasons here– I guess I need to plan on a seasonal vent switch. Not sure what you mean by high powered fan; but it would only be useful in the summer as far as the shower/bath area.

    The plants for odor are really just me trying to avoid the vent fan around the toilet area. I’ve heard about palms as well; but nothing detailed enough to help– I was hoping some culture somewhere figured it out already…

    Batteries for lights! NEVER! (FYI: rechargeable don’t work well for this application either due to their high internal discharge rates.)

    A manual switch can’t be beat for the level of control, simplicity, and cost. As stated in my post, a second switch could/should be used to provide responsible control. The reason for motion sensors or door switches is to solely account for irresponsible users. A toilet room where the low-light switch was tied to the door gives a feeling of loss of control but it shouldn’t bother most people and would cut down on the use of the conventional lighting. Say– can you collect info on DC lighting I’ve been working for sometime trying to find info on it. (big issue there is wire resistance, so you want as high voltage as possible– 48V seems the limit but most the lights are 12V… unless you want to pay for 6G copper wire… don’t have info on DC to DC transformers..)

    I was just wondering would sunlight coming into the shower area make a big enough difference in terms of people not using as much hot water? Would end up fairly diffuse light for privacy…

    Off topic:
    Clothes Dryers eject a ton of heat out from the house and leak plenty of cold from the outside (mine is gas so it has to– and I purposely picked gas because its better than electric heat; although, it has venting issues like all gas heat.) It seems that this would be a great source of waste heat.

  5. Matt the Engineer

    Solar yes, biogas maybe depending on the source.

    Blowing air around doesn’t dehumidify. Are you intending to mix it with air from the rest of the space? That should work, but you’ll need a separate exhaust system. If you’re using your high powered fan to exhaust, then you’re going to need a lot of makeup air – and then you’ll need to condition this makeup air, which will use a high amount of energy. I’m also curious as to what you mean by “high power”. I’d think high volume would be more appropriate than high velocity (what you probably think of as “high power”) unless you’re trying to direct this air in a certain direction. High volume low velocity fans would give you high airflow with very low power requirements.

  6. John B.: The separation of rooms: yes, I neglected to include this efficient Japanese modus operandi. Trigger mechanism for lights: what about battery-powered led lights. I use these in my bathroom currently. But ultimately the switch mechanism is the most direct solution. Odor reducing plants: I like this idea — perhaps a palm would be best?

    Matt the Engineer: At a highly optimized level, indeed electricity is not efficient for the heating. Mostly it’s a convenient retrofit. Solar or biogas heating would be most optimal and renewable, yes?

    Matt and John B.:
    On dehumidification for purposes of mildew elimination using high powered fan, ideally run for 20 minutes after a shower/bath. Is there a better way to dehumidify without heat loss, etc.?

  7. Matt the Engineer

    I can only comment on the energy side of this discussion:

    [John B] “Recapture of heat from waste water is not worth the cost” Not true at all. There are simple devices (basically a shell-tube heat exchanger) that are installed in plumbing to reclaim heat per fixture. This is especially a good idea with instant water heating.

    There are also small heat exchangers that would work well for bathrooms. If nothing else, simply use a shell-and-tube setup – a round metal duct inside a larger metal duct. Make sure to reclaim condensed water.


    In general, I have quite a few problems with the list. But many of them are likely location-based differences.

    Take instant-hot water. Yes, you reduce conduction losses between the hot water heater and the user, but you’re forced to use electric resistance heating. This may be justifiable with a highly green source of electricity (though I’d argue against even this), but in general you’re dumping a huge amount of carbon into the air from coal plants when using electricity in the US or Canada. Natural gas is the way to go for heating, or if you want to use electricity go for a heat pump – you may triple your efficiency. (update after re-reading) Ah, you’ll use renewable energy source for heat. The best way to do this is to use solar hot water heaters. Converting light to energy back to heat is not the most efficient way to go – again, a heat pump will possibly triple your efficiency (i.e. your solar panels would have to be 1/3 as large).

    Another example: dehumidification. A high powered fan may work (why high-powered?) fine in some climates, but in others you may want to actually keep the humidity since you’ll be humidifying anyway. The amount of air you exhaust has to be heated/cooled when supplied back into the space, so using a “high powered fan” might leak quite a lot of energy.

  8. Its your theory so I won’t quibble over differences with my designs with a similar goal. I’ll follow up on a few ideas you liked:

    I will say that the reason I wanted night lighting was not to avoid waking others; it was to avoid eye strain and waking myself up with bright lighting. (plus it uses less power.) A dimmer would be a compromise solution.

    A separate shower room would have full power lighting & fan tied to the door; while the toilet room would be a dim minimal lighting (optional additional lights.)

    I too was into motion sensors for a while and in fact I placed them in areas of my mothers house as a teenager. The problem with them is that the sensors pull an undocumented amount of power 24/7 and they are not smart about turning off when you leave (they work on motion of temp so every X seconds you have to wave your hands around or otherwise have it sit on for minutes after you leave.)
    The end result was more power use than power savings. In addition, they are costly, complex (disposable not fixable,) and contain electronic parts with toxins (do they now?) This is why I prefer simple mechanical solutions like a switch. I plan on having a push/pull rod on the door connected to a horizontal light switch; a really simple solution that will outperform the motion sensor. Its not ideal designer stuff, but hey– some people use toilet paper…

    Oh, my doors are not balanced so each slowly moves to the default position I want (bathroom door is always open, unless it was shut completely.)

    If I used a motion sensor it would be combined with a switch so that nothing could be left on all day. I’d try for a time limit switch but I’ve not seen any I like yet.

  9. Very good! Quite similar to my own list.

    I’ve NOT found plants that help dehumidify– can somebody find any? (I’ve found the opposite, I think in fact I found that one from you.)

    I would add though that some people like to soak as well as clean themselves; you can’t save water separating the two as you have. I’ve not seen any Ofuro that are more like a pool so you don’t have to waste the water; or better insulated etc. (in which case ozone to clean it– no I’m not suggesting cleaning in it– but you can’t do both let alone even use a Ofuro without 100s of gallons of water use.)

    Urinals don’t take too much space; ideal for men. What about a bidet?

    I planned on SEPARATE rooms for sanitation and better use by multiple people. The Japanese don’t combine them either (besides squatting toilets have more trouble with odors.) A simple dividing wall with shared water pipes would actually use less piping; therefore, less heat loss (assuming you are not wasteful enough to have 2 instant heaters in 1 bathroom.)

    I would include towel racks into the design. I like the radiator towel racks… over a heated floor in a small room that has the door open most the time.

    I have also been curious if anybody has made decent fold up washing tub (american style tub.) A walk-in shower that is handicapped accessible is large and also has a seat which could store a folding tub underneath. An Ofuro/Hot Tub can be placed almost anywhere that can take the water.

    Recapture of heat from waste water is not worth the cost if you have instant heating and nobody else is needing hot water at the moment. Sure, it helps for showers… but most I’ve seen are whole house type devices.

    Lighting ideas:
    Switch tied to DOOR; its on when door is shut. a 2nd switch could be allowed. I’m sick of bathroom lights being left on! Vent fan even worse..
    A dim low-light single LED or something for night time bathroom breaks (when one hardly needs to see.)

    Not needed in shower room. Toilet room’s used for flushing; Thermostatic mixer – fixed temperature nothing to wear out and replace – foot pedal is then only needed for on/off (control of water flow rate not important in most cases either.)

    Other issues:
    Room dimensions: I’ve been looking for some handicapped rules (ideally for anywhere not just my current location.)
    Insulation: tubs leak heat. wood should be worst stuff accepted (but wood involves coatings and is only for Ofuro.)
    Venting: loss of heat; air-to-air heat exchangers are too large for just a bathroom.
    Odor: what plants help with odors? (or that smell good and thrive in the environment)

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