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Rocket mass heater converts to cooler/air conditioner  RSS feed

 
gardener
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     With a little bit of management and possibly some ducting and a fan your RMH could be used for cooling in the summer. In many locales summer days are hot but the nights are much cooler. Of course any sensible person in this environment will ventilate heavily during summer nights.

   I once lived in a house with a large stone fireplace and chimney running up the center. The draft was open completely on summer nights and the natural chimney effect sucked hot air from the house as cool evening air flowed in to replace it. During the day the baffle was closed and stone which had been cooled by the night air became a large heat sink with cooled air currents constantly flowing toward the floor. In the heat of late afternoon this fireplace was by far the coolest surface in the house since this building was otherwise lacking adequate thermal mass.

   The horizontally built  RMH will not have the same natural draft as a vertical fireplace but this draft can be created. An insulated chimney could be installed adjacent to the RMH exhaust and the two could be joined during the cooling season. The top few feet of this vertical pipe could be of uninsulated pipe painted black. This would allow for a stronger chimney effect in the early morning when outside temperatures are still quite low.  Cold air could also be ducted into the feed door and fan driven. By ducting air to the feed door the incoming air can be selected from the coldest part of the natural environment whether that be the north side of the house, air from just above the pond or from earth tubes. Ducting the air to the feed door would also prevent the house from becoming uncomfortably cold during thermal mass cooling as sometimes happens in desert and mountain environments. My girls have often complained bitterly when my night ventilation has brought the temperature down to a frigid 68°F. The fact that they are being protected from the 90° heat of the next day has no bearing at all on their attitude towards my activities . Ducting to the feed door would alleviate this problem.

   Many people live in areas where summer nights are hot and muggy and where it feels like there is no relief in sight from the oppressive heat. I lived in such a place in Ontario. Hot summer nights were accompanied by zero wind speed so that opening the windows did almost nothing. But because we also had cold winters, ponds on the north side of buildings which were shaded by trees would reach peak summer temperatures in the mid-60s Fahrenheit. This cold water could be used within the radiator system for air conditioning purposes or air piped through water could be brought to the feed door of your RMH and to the rest of the house.

   When done properly all of this night ventilation can make the home too cold in the early morning for the more timid inhabitants. An insulating blanket covering your now frigid RMH could save this stored cooling potential until late afternoon when everybody returns from school and work. Now these same complaining ninnies can enjoy laying on the cool cob with their hands and feet pressed against it for maximum effect

   Let's discuss this to see what other steps can be taken to turn your RMH into an air conditioner.



   
 
Dale Hodgins
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    Concerning condensation. Since the air moving through the RMH is being warmed it would tend to gather moisture from the thermal mass during the night when cold air is running through it.  During the day when the feed door and baffle are closed there would be no opportunity for condensation on the inside of the thermal mass.

    On the exterior it would be a different story. Since it's a cold surface any air which is cooled beyond the dew point would lose its moisture. Just as a cold glass of water will become damp on the exterior, your mass heater will condense quite a bit of moisture unless you're in a very dry climate. Therefore any absorbent cushions should be removed during the cooling season and some sort of water catchment could be placed along the joint between the floor and mass heater. It might be advisable to give some slope to the seating area just as a flat roof still requires a little bit of slope. This moisture doesn't have to be viewed as a negative. It just means that our TMCooler is also a dehumidifier. Naturally any bench or other household structure whose surface is being used for cooling would need to have an oil finish or some sort of varnish to prevent the moisture from being absorbed by the cob.
 
Dale Hodgins
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We've started talking about the air-conditioning function on another thread which talks about the firewood feeding slide. So I'm bringing this to the top now so Brad can post his graphics concerning air conditioning. Thank you Brad in advance.
 
gardener
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Here ya go, not my graphic though got it from the internet. I did just see something about a solar chimney some where, a video maybe. I watch too many things about Alt. energy and they all end up bleeding together in my mind, if I remember the site or video I'll post a link.
Solarchimney.jpg
[Thumbnail for Solarchimney.jpg]
 
Dale Hodgins
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During the day, ventilation could be accomplished as shown in the drawing. Air to be exhausted would be taken from the ceiling area where temperatures are highest and new air could flow into the house through the earth tubes or pond tubes or through shaded north windows if air temperatures on that side of the house are acceptably low.

At night, the home could be ventilated until it reaches an equilibrium with the outside temperature. Once this happens, natural convection ceases. But the mass heater will stay warmer longer and can thus be used to continue ventilation until its temperature is brought down by the incoming air.

Now suppose the house is reaching a point where it will become uncomfortably cold. The mass heater could still be allowed to be cooled off with air piped directly to it. It would cool faster if this air were drawn through a swamp cooler.

In desert or mountain environments the thermal mass could be insulated in the evening. It could become quite frigid if lots of cold air is moved through the system. At some point convection would become weak and it might be necessary to force cold air, along with a fan.
 
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Location: Foothills north of L.A., zone 9ish mediterranean
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If lacking a cold pond, tap water is always cooler than summer air temps. Would it be possible to route all water used in the house through the mass when in summer AC mode? That way, during the night you can use the cold outside air, and during the day, when household water use is naturally likely to be higher, you have a second source of cool.

Maybe tough in a retrofit, but easier when building new. Perhaps it's just too complex, and easier to have a separate 'cool radiator'? Though if you already have an air exchange mechanism (solar chimney, convection or fan), I figure it makes sense to take advantage of that?
 
Dale Hodgins
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It would be quite simple to route all incoming water through the thermal mass. This would make use of all of the cooling potential from cold well water. This might not work so well in Southern California since quite often the incoming water could be at 75°F or more.

During the winter it would not be wise to route all incoming water through the thermal mass since this would result in flushing warm water down the toilet.

The water headed for the hot water heater should pass through the thermal mass year-round. During the winter it will be preheated by the fire, and during the summer it will aid in air conditioning and it will also be heated somewhat.
 
Jonathan 'yukkuri' Kame
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Location: Foothills north of L.A., zone 9ish mediterranean
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I doubt our cold water gets up to 75f in summer, but I haven't spent a full summer here yet. But even if the water was those temps, wouldn't 75f water be better than outside air which could be well over 100f, or indoor air that could be 90f? This little old house isn't too well insulated.

I'm probably better off with a swamp cooler and a pop-can solar air heater, but I love the idea of a dual purpose mass heater/cooler.

If I don't put together a swamp cooler by this summer, I will play with some cheap ways to take advantage of evaporative cooling. Mop the concrete floor with cold water at the heat of the day to drop the floor a couple of degrees. Cool toes in summer are almost as good as a butt warmer in winter.



 
Dale Hodgins
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I once lived in a hellishly hot, south facing apartment building in southern Ontario. Same latitude as Northern California. Although we're much further north than you, the long summer days and the bowl effect of being in the lake basin make this an awful place in the summer. Farmworkers from Trinidad complained that they felt like they were going to "rot" from the heat and humidity.

Poor Man's Swamp Cooler
I covered our concrete balcony with old carpet which I hosed down every day. I also threw water on the bricks in the early evening to facilitate evaporative cooling. The bricks were hot to the touch by late afternoon.--------- Inside, I hung wet laundry and and constantly kept hanging towels and sheets moist. I used a pressurized spray bottle to mist the air and I also dampened wall and ceiling areas. I had zero respect for the building or for the landlord so I just did whatever it took to survive the heat without regard for the building which was 30 years past its best before date. My daughter was two at the time and even with these efforts I still had to take her to the Park sometimes so she could sleep. We encountered other families who were also escaping the heat. At first the cops bothered us a bit but as it got hotter they turned a blind eye. I don't recall seeing one homeless person or alcoholic. Different times in the early 90s.

During the hottest conditions we seldom had much wind and being an apartment there were only openings on that southern surface so no cross ventilation was possible. It was a crap building with mostly smokers so we sealed ourselves off from the hallway. In order to get some airflow I would leave the kitchen fan and the bathroom fan running throughout the night.

It was an awful summer but these efforts made it much more bearable for us than for many of our neighbors. The oppressive heat of summer is part of what sent me to live on Vancouver Island where 80°F is quite hot.
 
Dale Hodgins
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Snooping through some old threads tonight. This one never got much traction, but many have joined the party since then.
 
pollinator
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Dale & Permies Cloud: A couple of thoughts, rob roy tried to make the solar chimney work for him at ~ 44*~N. Latitude, and found that he got poor results,
though he still remains open to further exploration by other people !

As Erica Wisner has pointed out, if the thermal mass is located within the building deeply enough to be shaded by overhanging eves, in summer it will be a
cooling thermal mass. Later when the more horizontal winter rays of the Sun reach back into the building, the Thermal Mass is there waiting to be warmed
by the rays of the sun, and just like a trombe wall benefit from being a dark color !

Your location can get very humid and water condensation is a problem in such conditions. I have lived where, if you did not use a window squeegee on the
walls of your shower immediately after, it 'grew things'. In such locations the benefits of swamp coolers rapidly diminish. But, though I would seal the top of
the cob, I would leave the sides unsealed as Cob is always Soaking up water vapor and releasing it again depending on the relative humidity and its present
state of hydration! Maybe I am assuming to much for your location, but It should work in many areas, similar to your Swamp Cooler! Y.M.M.V. Big AL !
 
Dale Hodgins
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Hi Al. I'm seldom designing with only my own location in mind. The need for cooling here is generally not an issue for anyone with a lick of sense who lives in a decent house. The fact that evenings almost always include cool sea breezes, makes diurnal temperature control as simple as night ventilation for most. My place is on high ground 8 miles from the ocean and any sort of evaporator would work better there than on the coast.

Funny that you mentioned Rob Roy's location. My stone chimney that worked so well as a cool thermal mass, was in Ontario, just north of him. The chimney effect was generated within the home at night by allowing air to flow into the fireplace and up through the chimney. A large portion of that chimney was in a hot attic. In several homes, I've removed the attic hatch cover at night to allow hot air to be sucked up. Doors left open allow cool outside air to replace it. Many houses have roof vents near the peak, but soffit vents are covered with insulation or are non existent. Because of this, the attic remains hot well into the evening. The open attic hatch works like a giant soffit vent. The moment the hatch is opened, air begins rushing out of the peak vents. Not only do we lose heat with the cool air being sucked through the house, the attic is cooled and less heat is available to be radiated downward. In the morning, the attic is completely cooled. If an earth tube were used to supply incoming air to the lowest floor, most attics beneath asphalt roofing could serve as solar chimneys during the day as well. I see no reason to build a solar chimney when most houses are already capped with one. Asphalt shingles are terrible things, but for the millions who have a home covered with this garbage, here is a way for them to use the stiflingly hot conditions they foster to cool their homes.

I didn't know how to link pages two years ago when I started these topics. Better late than never. http://www.permies.com/t/9598/wood-burning-stoves/RMH-Air-Conditioner-Trombe-Wall
 
allen lumley
pollinator
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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Date & 'The Permies Cloud' ; Rob Roy loves his personal vision of a living roof, over membrane, and rarely receives more heat energy than he can handle with
just the use of insulated window curtains

On the other hand his solar chimneys are very conventional builds, now that you reminded me of the difference in builds I can see where he would need to
generate a lot of heat first, to pump just a little more heat out, so not much return on investment ! No matter how we play with it, Air is a poor storage medium
for Heat ! For the Good of the craft ! Big AL

P.S. When we use our search engine to access our Forum Threads we Are accessing our own Permies Cloud ! If Apple can have their own iCloud, Permies certainly
can too ! A. L.
 
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I'm thinking of trying a solar chimney this coming year - a simple 4" diameter pipe painted matte black and attached to the south side of my house and extending up about 4 ft above the roofline. I then have a conveniently located cat door on the north side (cool side) of my home that I could prop open for cool air intake.

I've seen things about simple solar chimneys like this in the past but I'm not sure how high on the wall to place the outtake vent - should it be high on the wall? (hot air rising?) I also thought that I could use the existing hole in my exterior wall where the dryer vents. As I use my dryer maybe 4 times a year - always in winter - perhaps I could make that hole do double duty - air outtake for the solar chimney in the summer - venting for the dryer in the winter. What do you think? If I can get away with not drilling another large hole in my double-bonded brick construction - that would make me a happy camper.

Also thinking of adding some kind of low basin filled with water/water and charcoal to place outside the cat door to increase the cooling effect. This would work until our monsoon season hit - then it's just too hot and humid.

From: http://sustainabilityworkshop.autodesk.com/buildings/stack-ventilation-and-bernoullis-principle





 
Dale Hodgins
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With most houses, the dryer vent hole is at a low point on the wall. This would make it make it a good candidate as an air intake. If the bricks and soil outside aren't shaded, they should be, so that the incoming air can be as cool as possible. A clothes drying rack placed in the same room as that hole and placed in the stream of incoming dry air, would work as a clothes dryer and swamp cooler. If the towels come out a little stiff, they could be run through the room vented dryer with it set to air fluff and the moist air would be quickly transported throughout the house. This arrangement would be a little more tricky if done by the cat door which is not in the room where clothes racks and water are generally welcome.

Laundry is unlikely to be done in great enough quantity to keep the swamp cooler going. A rack covered in burlap or some other fabric, could be set in a water trough and a small fish tank pump could keep it moist for a penny a day. Some water will wick up the fabric from the trough and the pump could intermittently pour water over the upper fabric.
 
Jennifer Wadsworth
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Actually the dryer vent is on the south (sun) side so I was thinking of using that hole as the outtake vent for the solar chimney. The INTAKE hole would be the cat door which is on the north side of the house with additional shade from a screened in porch. That screened in porch is also where my washing machine is (so the greywater can go out to the landscape) and where my clothesline is. So in fact, if I had laundry hanging, air would (presumably) be moistened by the laundry.

Now in Phoenix in May, Jun and Sept especially (less chance of monsoons and humidity) my laundry is dry on the line in about 30-45 mins - it's actually faster to dry clothes on the line than in the drier set on high! (gotta love Phoenix). So that residual humidity doesn't last too long. However, possibly a low basin filled with charcoal and water and covered with a wet cloth might last longer to provide that swamp cooler effect.

Basically what I needed to know above is how high on the wall the OUTPUT hole should be. I theorized that because hot air rises, it should be higher on the wall. However from the few pics I've been able to gather, it looks like the output hole is also located close to the ground. I'm not sure that quite makes sense to me. Anyone have any thoughts on that?
 
Dale Hodgins
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Jennifer, I completely understood your first posting. I was stating how this would normally be done in a house that has a north facing or otherwise shaded and cool area outside of the dryer vent hole. Here in the north, south facing space is not where we normally put the laundry room. ----------------------------------------------------------------------------------------------------------------
You want to draw the air from the highest spot that it can be done from. If the house has cathedral ceilings, it would be best to remove the hot air that accumulates at the peak. A 4 inch pipe is not likely to move as much air as you'd like. Something a foot in diameter would probably move 10 times more air. If you have an attic, the very simplest way to reduce cooling loads is to ventilate. Special attention should be paid to making sure that there is plenty of soffit venting. Upper and lower gable end vents can help greatly if soffits are difficult to vent. No matter how you remove air, the incoming air will do more good if it is forced to travel an indirect path to the exit vent. Several small inlets spread out from one another are better than one large one of equal volume. With only one incoming source, some areas of the house are bound to be poorly ventilated. Houses with an open concept are much easier to ventilate that are homes that are broken into many sealed compartments.

How far is your vent from the top of the wall ?
Is your attic really well ventilated ?
Are there any cathedral ceilings ?
Is your vent a long way from the cat door ?

I have ventilated some very hot demolition sites. For a regular wood framed house, the removal of the brick chimney generally leaves a hole between 4 and 15 sq ft. from basement, through to the attic to the sky. Once the first row of bricks below the attic is removed, the lower air wafts upward and attic temperature can be reduced by 30 F on a hot summer day. This is something that I like to get over with by 9 am, before it gets too hot. I remove the attic hatch before I start, so that when I break into the attic, hot air can rush out of the chimney hole and be quickly replenished by cool air from within the house. Flow rates of 20 cubic feet per second are typical of smaller chimney holes. I doubt that a 4 inch pipe would suck even one FPS.
 
Jennifer Wadsworth
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Dale - gotcha. See answers below.

--How far is your vent from the top of the wall ?
The existing dryer vent for heat OUTPUT (south side of house) is about 6-8" above the floor (My house is double-bonded brick, built in 1939, slab foundation)
The existing cat door (north side of house) is about 2-3" from the floor.

--Is your attic really well ventilated ?
Yes - My house is 1100 square feet and there are 5 vents in the attic that were added when I upgraded the insulation to the recommended R38 for our area. The vents made a HUGE difference. I can't remember what they're called by they are not ridge or gable vents, they are on the long, flat planes of the roof (I have a hip roof and they are on the north and south sides which are the long sides of my house)

--Are there any cathedral ceilings ?
No - standard 8' ceilings

--Is your vent a long way from the cat door ?
The dryer vent hole is about 30' away from the cat door and is not in a direct line - the air would flow through the cat door into my office and then have to dogleg in my central hallway, flow into the kitchen, make another slight dogleg and flow through the kitchen foyer area where the dryer is located.
 
Dale Hodgins
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A pipe would need to be run up to within 6 inches of the ceiling, so that warm air can be drawn from there. For best results, it would be great to have vents placed near the ceiling in the laundry room so that the hottest air from adjacent rooms can flow into that room and ultimately, up the chimney.

Suspend one thermometer from the ceiling at 6 inches from the top and suspend another at top of door height, to see how much temperature stratification you're dealing with. If air must flow through a door opening, the hottest air from adjacent rooms will remain trapped against the ceilings in those rooms.
 
Jennifer Wadsworth
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That's pretty much what I was thinking too and was surprised when the pics showed otherwise (or didn't show it at all).

Thanks Dale - I'll be pondering this project some more through winter and probably get off my butt and do something about it in April/May when it starts to get HOT. I'm with you on multiple pipes and air outtakes (but will probably install one first to see how it goes). That seemed like the best way to increase airflow as well throughout the house.
 
Do not set lab on fire. Or this tiny ad:
five days of natural building (wofati and cob) and rocket cooktop oct 8-12, 2018
https://permies.com/t/92034/permaculture-projects/days-natural-building-wofati-cob
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