Microhouse Winterization

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If Microhouse is not in use over the winter, it will freeze inside, and water pipes can burst.

Water pipes may include hydronics, hot water heating, showers, toilets, and sinks. Moreover, since the main water line runs next to the house under the shallow insulated footer - care must be taken to assure that the pipes next to the house are not exposed above the shallow insulated footer insulation- or that sufficient insulation is present so that the edge next to the house foundation is not exposed to the cold. The outside connection is on the west side of the house, by the old bathroom.

To prevent risk of burst pipes, this is the recommended procedure:

  1. Hydronic system, once installed, should be filled with antifreeze, at least 30% concentration, and should be circulated through the system before shutting off water supply.
  2. Shut off water to the Microhouse by turning off a 1" valve in the outside pit by Hablab.
  3. Next, open the sinks, showers, and flush all toilets so water drains out in the house.
  4. Break one side (hot or cold) on the water heater to make sure that water drains out of the hot water heater.

Filling a Jacketed Hydronic Stove with Antifreeze

30% minimum. Volume of water in jacket is 50 gal, and volume per 250' of 1/2" PEX circuit is 2.5 gallons. There are 4 circuits in the house, 2 in the aquaponics, and another full house circuit with 2 Buderus radiators, approximately 3 gallons of water each (Buderus Model 22 - [1]). Total water volume = 50 + 15 + 6 = 71 gallons. About 25 gallons of 100% antifreeze does it.

  1. Shut off water supply at the pit by Hablab
  2. crack a fitting on top of the water jacket stove (air inlet for purge)
  3. Crack the bottom inlet with the heater element to drain into buckets.
    1. Note - bottom must be emptied through a valve - the pressure through a raw 1" opening is quicker to empty than 5 gallon buckets can handle.
    2. Either equip the bottom with a valve - or siphon out from the top.
  4. Drain one bucket at a time, and empty it as a second bucket fills, and so on until all water is drained (first time only, to verify that the volume of the stove is indeed 50 gallons)
  5. Once we know that it is indeed 50 gallons, it suffices to drain 25 gallons only before plugging the drain back up.
  6. Fill with antifreeze from the top, using a funnel
  7. Turn water supply back on, so that all air is pushed out, and escapes out the air purge on top of the hydronic system.
  8. Run the circulator pump for a day to circulate fluid through the system and prime the system
  9. It is a good idea to heat the stove after a day of circulation, to verify that the system was primed correctly - by touching all the water pipes to make sure they are circulating if they are hot.

Tools needed:

  1. 1 Pipe wrenches
  2. 1 Adjustable wrench
  3. Funnel
  4. [2] 5 gallon buckets

Alternative to Antifreeze

  • The alternative is to run the water pump all winter long - but that does not protect the expansion tank or any volumes of dead water space, so it's a risky solution, and one that costs $6/month in energy cost at 14 cent per hour electricity cost.


  1. If there are no use in winter, Microhouse should be winterized Nov 1 of each year - which is prior to the first frost date.
  2. If there is use in winter, winterization is not necessary as long as there is indoor heat.


  1. The hot water heater can not explode in Microhouse in extreme cold gettin in through the exhaust because the exhaust pipe is quite long, and air in it warms up in a heated building before it gets a chance to freeze like it can do in HabLab.
  2. The best solution for a water heater design is an open source, freeze proof, drainable design. Or one that is integrated with the hydronic stove, so in winter, no extra water heating gas is necessary when the stove is running.