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Seeking advice on attached greenhouse - Bioshelter Market Garden or Secret Greenhouse of Survival?

 
Posts: 47
Location: South East Missouri
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I am planning to build a greenhouse on the south-facing end of my house.  It is a perfect solar exposure, and will feature an aquaponics system with Tilapia.  The fish tanks will be in the cellar where I can control the temperature, and the growing beds will be in the greenhouse.  The greenhouse will provide passive solar heating for the living space, and will be augmented with one (maybe two) rocket mass heaters for the night time and periods with minimal winter sun.  I have provided a picture to show the south end of the house, which is about 35 foot wide.  Notice the windows in the cellar and the windows in the living space... rising hot air will easily heat the house.  I am contemplating a building plan based on the book Secret Greenhouse of Survival by author Rick Austin, but am curious if the Bioshelter Market Garden design might offer some advantages.  A concern is the smells produced by the fish tanks.  I am hoping that a veritable jungle in the greenhouse will ameliorate the potential smell, but am not sure.  It will be an experiment.  Has anyone tried this?
Perfect-Southern-Solar-Exposure.jpg
Perfect Southern Solar Exposure
Perfect Southern Solar Exposure
 
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I too have a south facing home, which would lend itself to an attached greenhouse. I have a rocket stove in the house with an attached bench and am considering building a second RMH with bench in the greenhouse for heating.

My question is, how would I deal with excess greenhouse heat in the summer? Will it roast me out of my house?
 
pollinator
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I have the same question Angela! I have a south facing wall of my home that works like solar catch. It also happens to be the side of my house with a massive window. I'm wondering if I design it so that it can have some sort of cross breeze during peak summer heat if that would help.
 
gardener
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I have the similar design challenge, and  I see vines vines and trees as solutions that should offer shade when needed and allow sun when that is desirable.
 
Phillip Stuckemeyer
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I plan to design my greenhouse so that the top edge of the roof structure falls directly below the 2nd story windows.  I will place roof windows strategically below the double-hung windows, and then at the beginning of the cold system I will install a temporary shroud with insulated flex duct that will carry the heat into the windows unless I close them.  I have attached a picture.  With three of these vents coming up from the high point of the greenhouse, the warm air will rise naturally.  I can always install a damper or simply close the window to stop the hot air in the afternoon, or to prevent cold air infiltration in the night time.  In the summer time I will merely open the roof windows to allow the air to vent in the daytime.  The roof windows can be designed with automatic openers, or I can install a vent fan that will draw air into a vent on the west side of the greenhouse and exhaust it on the east side.  Plus, my greenhouse will feature a window wall and all the windows can be opened when it is not raining for cross ventilation.  Should be easy to prevent the house from overheating.
WindowVent.jpg
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Angela Wilcox
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Phillip, I see you have planned a great deal of functional design. I admire the venting into the windows with a damper. What is a window wall?
 
Phillip Stuckemeyer
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When I say window wall, I only mean that the vertical, south facing wall of the greenhouse will be constructed of normal windows that you can buy at Home Depot or Lowes.  Nothing special.  Just windows that can be opened.  The design that is illustrated in the Secret Greenhouse of Survival book is an example.
 
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Here is my green house to get an idea. We roll up the plastic when it isn’t freezing. We have a 12hr freeze tonight I hope it works.
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Phillip Stuckemeyer
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I had a small detached greenhouse in Richmond, Virginia about 5 years ago.  I was a licensed tilapia grower (license required in Virginia) with an aquaponics system.  I lost control of the temperature, and suffered a massive fish kill.  This time I hope to do it right.  However, it needs to be simple and easy, or I will neglect it, or get too old to actually do it.  Planning and good design are a hallmark of permaculture, right?
 
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Greenhouse or sun room?   Even in the winter here at high altitude in New Mexico people with greenhouses have overheating issues on sunny winter days.  I'm thinking that a sun room, one with solid roof, half-walls, and lots of windows might solve the overheating issue year-round.  I wonder how small a pool could be to help even out the temperature.  Having one would to provide humidity in this dry climate.  

The idea of a modified bioshelter attracts me and I'm hoping that Darrel Frey's book will provide guidance for me.  I don't want to try to reinvent the wheel, but I know that a real greenhouse would be a solar oven most of the year where I live.
 
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Location: Zone 5B, NB, Canada
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One major concern about the fish tanks in the basement, much more important than smell, is moisture management. You will need to have a lot of active ventilation or the humidity will cause big problems with mould, mildew and eventually rot. It can definitely be done but it is important to do it right. Another option for you might be to place the tanks in the floor of the greenhouse, under your grow beds. Then they would be shaded from the sun and the earth would buffer against temperature swings. Commercial fish hatcheries in the north place their tanks at least partially below grade for this buffering effect. How big are your tanks?
 
pollinator
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I would be very careful when taking house ventilation from a greenhouse. You're courting mould issues, especially if you're retrofitting a standard-build structure of matchsticks and (god-I-hope-it-stays)drywall.

You compound that with the addition of fish tanks.

Don't get me wrong, I love virtually all of your ideas. But sometimes, when we get into function-stacking mode, we compound unintended consequences.

Without changing much of what you want, I would see what is possible with regards to dehumidifying the air coming in from the greenhouse, and filtering it for any disease vectors. With moisture issues, you also court increased spore counts. I would probably have an allergen filter on the incoming air, and if it were possible to have a dehumidifier going in the second-floor air intake room, that might head off some problems.

You might also, if you haven't already, rip out any moisture-sensitive finishings and replace with tile, laminate or linoleum, and see what is recommended for sealing drywall up against the threat of increased moisture in the air.

Conversely, you could figure out if there's a heat-transfer method that you could use that would enable you to benefit from the heat of the greenhouse without actually taking in the greenhouse air. Such might be a closed-system hydronic setup, but perhaps with a more suitable transfer fluid. You could also look to see if there are filtration setups that allow you to dehumidify without dropping the air temperature, and in-line with an exhaust. Then, absent excess moisture and having passed through a good particulate filter, it would be safe to use to augment the heating capacity of the home.

As to excess greenhouse heat in the summer, first off, if it's getting that hot in your greenhouse, chances are you're boiling your fish, your plants, except perhaps tropicals, are dead, and any soil not kept perpetually damp will have reverted to lifeless dirt. In my opinion, you need to be able to vent your greenhouse to the outside at need, and via automatic vents, preferably, or it won't work as a greenhouse, except for tropicals. And even those have maximum temperatures.

It is recommended that shade be included in the design, as if you design your greenhouse to utilise minimum winter solar energy to maximum effect, there will most probably be instances in the summer when you need to provide shade to block out some of the solar energy, for fear of heating it more than the vents can manage to cool it. So if you have shadecloth on rollers that you pull down when it's too hot and sunny, that could do it.

I think the best way to proceed is to build your greenhouse attached to your house as you have indicated, but to wait on the use of the greenhouse as a tool to heat your house, at least until you get a handle on the temperatures and humidity. It seems straightforward, but there are so many tricky variables in what is proposed here that something would definitely die. I'm betting on your plants, or possibly your fish, but if you get really unlucky... well let's just say that you don't want to get really unlucky. Do you know what it costs to clear a house of a full-blown mould infestation? Do you know to what extent your insurance company will cover mould damage from a scenario as described here?

If you want an auxiliary heat source, you've already mentioned RMHs. Why not simply build one in your basement rather than introducing excess humidity and agents of decomposition into the living space where you breathe?

-CK
 
Phillip Stuckemeyer
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I use the readily available IBC (Industrial Bladder Container) in a 275 or 320 gallon capacity.  I have attached a picture.  The fish prefer the dark, and so a lid that fits well can help contain the moisture.  Also, I will consider lining the bottom of the floor joists with foil backed insulation, and seal the joints with silicon RTV.  You are correct that an abundance of caution is needed.
FishTanks.jpg
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Phillip Stuckemeyer
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Chris, you raise many valid issues.  I have thought about all of these issues, with the exception of Insurance.  That is a good one!  The smell is what my wife will be immediately concerned about.  This will require some experimentation, and quick action to avoid the problems.  A heat exchanger is certainly one option, although this will require an active system, rather than passive.  This is not really a problem, as I have a huge solar system, and so I have plenty of power to run the fans.  I would prefer passive, however.
 
Rob Clinch
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IBC work perfectly well for small set ups and are a great upcycling use (as long as you know what was in them first!). Having them in the cellar is fine as long as precautions are taken. Foil on floor trusses definitely doesn’t hurt but there is no substitute for proper ventilation, if the lids are preventing moisture from escaping the tanks then they are also preventing gas exchange between the water and the atmosphere. If they are are loose enough for proper gas exchange then they are loose enough to allow moisture out. Even a single medium size  aquarium with a lid can cause mould problems in a room with out good air exchange, I found this out the hard way, a long time ago, as a teenager, in my bedroom at my parents house!
 
William Bronson
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The OP mentioned locating the fish tanks in the basement.
That will keep the fish safe,  and keep the tanks from adding to the greenhouse moisture.

Instead of bringing moist hot air into the upper floors,  where the inhabitants and furnishings won't appreciate it,   maybe use  a (bathroom) fan to push that air down to a relatively cool water resistant surface in the basement.

The basement floor might work,  or blow it past copper coils that thermo-siphon from the tanks.
The condensation could be kept or drained away,  most of the heat will have transferred during the process of condensation.

You are still making the house air wetter,  but the fish like it hot and wet( up to 85 f)  and the basement should probably  be fitted out for humidity anyway.

The majority of escaping heat will head upward,  the humidity with it,  so a vapor barrier between the first floor and basement will be needed.

A RMH in the greenhouse might skirt building/fire regulations, and/or insurance requirements.
It will also produce a lot of dry radiant heat from the barrel as it it is actively fired,  and even, long lasting heat from the mass when it has been put out.
That heat might keep moisture in the greenhouse from being a problem at all.
If this is to be a green house and not simply a giant  low mass solar collector ,  we need to retain some heat in the space, to keep it above freezing at night.
Even if we stripped as much heat from the space as possible,  we  could choose to return some of it, assuming we have stored it.

The greenhouse might carry the house during the day,  the house carrying the greenhouse at night




A simple way to move heat into the second floor windows without bringing the humidity with it might be a window  air conditioner with the  heat pump switch.
Or an actual mini-split could be located inside the greenhouse, but that is pricey.

The structure that a greenhouse has lends itself to growing deciduous vines for spring/summer shade, but using shade cloth or even Mylar might be worthwhile.
I like the vines because they potentially deploy and store themselves every year,at seasonally appropriate times.
 
Phillip Stuckemeyer
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Another option that I have toyed with for a  while is three (3) trombe walls that circulate air from inside the living quarters through the greenhouse.  I have attached a picture.  The top of each Trombe wall would feature a vent for the summer time, and the window would be kept closed for air conditioning.  This would complete solve the problem of both moisture and smell, and I could build the trombe walls now and add the greenhouse later.
Trombe_Walls.jpg
Trombe_Walls
Trombe_Walls
 
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Phillip Stuckemeyer wrote:I am planning to build a greenhouse on the south-facing end of my house.  It is a perfect solar exposure, and will feature an aquaponics system with Tilapia.  The fish tanks will be in the cellar where I can control the temperature, and the growing beds will be in the greenhouse.  The greenhouse will provide passive solar heating for the living space, and will be augmented with one (maybe two) rocket mass heaters for the night time and periods with minimal winter sun.  I have provided a picture to show the south end of the house, which is about 35 foot wide.  Notice the windows in the cellar and the windows in the living space... rising hot air will easily heat the house.  I am contemplating a building plan based on the book Secret Greenhouse of Survival by author Rick Austin, but am curious if the Bioshelter Market Garden design might offer some advantages.  A concern is the smells produced by the fish tanks.  I am hoping that a veritable jungle in the greenhouse will ameliorate the potential smell, but am not sure.  It will be an experiment.  Has anyone tried this?


Hi Phillip
The smell of the fish will add to the other moisture of the greenhouse. Good air flow is always needed through the greenhouse during the warn season to keep algae from growing everywhere. You can use heat exchange tubes to capture heat but I would not flow greenhouse air directly into the house. The best use of greenhouse heating I have seen is a double envelope house designed back in the 60's or 70's by NASA engineers and not a suitable retrofit for existing homes.

You will also need to watch how the heat and moisture of the greenhouse will affect you house directly. It appears you have siding which is covering something. Any siding will retain moisture and cause problems. A dry sun room with mass storage may be better directly against your house. Vent the top of the sun room during summer months to keep the house cool. You can put a greenhouse adjacent to the sun room to vent hot air into the greenhouse.

Mark
 
Chris Kott
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Depending on how the house is built, you might be creating moisture and condensation issues within the walls adjacent to the greenhouse.

I would bury the IBCs in the floor of the greenhouse. I wasn't kidding about adding excess moisture within the building envelope. Your drywall will rot away, virtually guaranteed, unless you spend a disproportionate amount of time and effort into combatting the moisture issue you're introducing.

For someone who prefers a passive approach, I would think you'd want to do all you can to avoid causing problems first.

-CK
 
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Sounds like an interesting project.  I've visited the aquaponics set up at the local collecge multiple times, which has the plants & fish in the same greenhouse.  It's never smelled bad to me.  
 
Rob Clinch
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In my experience with aquaculture on both home (300 gallons) and commercial scale (1 million+ salmon smolt/ year) it’s not the actual fish that cause a smell, it’s fish feed, dead fish and moisture issues caused by poor air circulation that causes any bad smells. If your water stinks it most likely is caused by inadequate aeration or using high fat feed that leaches oils onto the surface of the tank which will then make its way to your grow beds. Red wiggler worms will help breaking it down in beds but it could still have some smell.
 
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I am not familiar with the smell produced by aquaponics, but I do suggest incorporating mass into the greenhouse to stabilize temperatures. A deep growing bed made of concrete block with rock storage underneath a deep layer of soil has multiple benefits. Air circulated from aquaponics area and the greenhouse will condense in the rock storage and help dehumidify the rest of the system. Be sure to allow for adequate ventilation of the greenhouse in summer!  Passive roof vents are the best options and they should be sized to maintain the airflow and desired temperatures in summer.
The deep soil beds provide a year round growing space and provide thermal mass to help stabilize the greenhouse temperature
 
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I've lived in houses in the high desert heated by attached south-facing greenhouses for about 25 years. Our greenhouses are detachable. They are just UV-resistant film, so we put them up in October and take them down in April or May when it gets too hot and/or windy. Otherwise, as somebody said above, all the plants would be killed by the heat, and it would make the house unliveable.

It's also important to have large areas of door and window in the east and west ends, so that in the shoulder season of spring and autumn, you can open the ends in the daytime and close them up in the night.

 
Phillip Stuckemeyer
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I have been conducting an experiment.  I am building the mini-trombe wall that I envisioned earlier in this thread.  This is the first of 3 solar collectors that draw cool air from the house and recycle hot air into the house.  By incorporating this design into the greenhouse that I eventually will build on the south-facing side of my home, I will be able to capitalize on passive solar heating, without worrying about the smell of an aquaponics system (fishy smell) as well as avoiding the potential for fungus growth and mold damage with the attendant health consequences.  Since this is an experiment, I suspect that the lessons learned will inform a modified design for the 2nd and 3rd trombe walls as I work toward optimizing efficiency.
HouseSouthSide.jpg
HouseSouthSide
HouseSouthSide
 
Phillip Stuckemeyer
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I built the prototype using 2X10 dimension lumber, which turns out was very heavy and way too large a box.  The cool air falls down the back side of the collector, in a channel that is 34 inches wide and about 4 inches deep, fashioned out of insulating styrofoam.  The front side is also 34 inches wide, and 4 inches deep but I constructed this out of metal ductwork.  I think this is a bad design, however, and the result is that the warm air takes a long time to start flowing into the house.  I think that it takes a long time to warm up such a large volume of cold air, and this cold air is contained in a cold metal box.  I suspect that I need to ditch the metal ductwork, and build the collector out of a styrofoam backing with foil surface painted black, that is no more than 1 inch in depth.  This should result in a much smaller thermal mass and a much lower volume of cold air, and a much more energy efficient design.  The 6-mil plastic that currently covers the collector will eventually be replaced with 2-ply polycarbonate greenhouse panels, but I want to get this prototype working better, more efficiently, before I spend the money on the greenhouse sheeting.
MiniTrombeWall.jpg
MiniTrombeWall
MiniTrombeWall
 
Phillip Stuckemeyer
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4-inch insulated flexible ducts carry the air through the window in a box fashioned from white PVC sheeting.  Two pipes draw in cool air, while three pipes return the warm air.  The PVC panel consist of two separate sheets with a 1-inch styrofoam insulating layer between them.  Right now it seems like it takes over an hour of direct sunlight before I can feel the hot air rising into the house.  I can feel air entering the lower 2 vents, and cool air rising in through the three upper vents, but it seems like it take over an hour for the air to feel warm.  I like the basic design layout, and a coat of white paint on the collector's wooden components will make the collector much more visually appealing, but I must rethink the basic design and get it right.
WindowVent.jpg
WindowVent
WindowVent
 
Lif Strand
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Phillip Stuckemeyer wrote: I can feel air entering the lower 2 vents, and cool air rising in through the three upper vents, but it seems like it take over an hour for the air to feel warm.  


Can you close the vents?  Maybe there should be no airflow for a while until the whole thing is properly warm.  Venting cool air into the house for an hour when you want warm doesn't seem like a wonderful thing.
 
Phillip Stuckemeyer
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I am considering a foil backed, insulating blanket.  By closing the shutters on the blanket it should stop the airflow for all 5 vents.  I am also considering a temperature actuated damper in the bottom of the box activated by a thermo-bulb mounted in the riser duct.  However, all these options seem like a waste of effort until I reduce the volume of air in the heating chamber.  Week after next I will cut the box down to size and post an update with pictures of the inner workings.  Traveling on business this week.
 
Lif Strand
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Phillip Stuckemeyer wrote:I am considering a foil backed, insulating blanket.  By closing the shutters on the blanket it should stop the airflow for all 5 vents.  I am also considering a temperature actuated damper in the bottom of the box activated by a thermo-bulb mounted in the riser duct.  However, all these options seem like a waste of effort until I reduce the volume of air in the heating chamber.  Week after next I will cut the box down to size and post an update with pictures of the inner workings.  Traveling on business this week.


Putting a block over the vents for a hour in the morning seems to me a small effort compared to cutting the box down!  

As to cutting the box down:  the more volume of air there is to heat, the better I think.  Maybe this isn't an accurate way of describing what I'm talking about, but the incoming cold air coming through your heating chamber will cool down the volume of air at the same time that the sun is heating it.  You have to balance the amount of flow against the volume to be heated.  In the morning when the air in the box is cool, then the sun's got to warm it up plus warm up the air that will come in soon as the box air starts warming up.  That's what blocking the vent fixes.

If you block the air flow, then the box air gets hot.  You open the vent at that point and air comes out the vents, incoming cold air comes in the bottom of the box.  But since there's already hot air in the box, the amount that the incoming cold air can cool the volume already in the box is less.  I think that makes sense, but maybe not!  I don't know the math/engineering language to describe what I'm saying but experience has told me this is the way it works.
 
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Also take a look at wax filled automatic vent openers Automatic Greenhouse Window Opener, Univent.  There are also very little ones that are used in washing machines and other appliances.  These work through expansion of wax in the cylinder.

You might be able to find one that will keep your setup closed until it heats up hot enough to automatically open.  When I did some research into these before I found that there are a few manufacturers which make waxes with different set points and will open at different temperatures.  That said, I have not figured out how to get ahold of these specialty waxes.  So you are likely stuck with opening temperatures in the 70F to 80F, which would likely be perfect for you.
 
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When I first saw your trombe wall sketch I thought it was brilliant and I still do.  I thought you were going to provide the cold air from the lower window, let it sink to ground level and then let the greenhouse effect heat and raise it to the upstairs window.  I think that would really help it to move air.  The people at Builditsolar.com have lots of examples of people doing solar thermal air chimneys (maybe I have the name wrong).  The depth of the chambers is important to get it right.  And having a flapper to let air move up during the day but not fall back down at night is important.  Otherwise it would just run in reverse.

I have a modestly big greenhouse and it's very humid inside at times.  I wouldn't want to attach it to my house.  I've heard many warnings against joining greenhouses to houses for moisture infiltration and rot reasons.

I use Gigavent openers on my greenhouse since my vents are huge.  They work great.  One up high and one down low keep things under control during the shoulder seasons.  I keep the lower vents locked open and the upper ones just vent as needed during the summer.  My greenhouse still gets up near 100 degrees on a bright sunny January day when it's 0 outside.
 
Ebo David
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@Mike, you might want to look at increasing the bottom, and possibly the top vents.  I read in a greenhouse design manual that the total ventilation area needed might be as large as 30% of the the floor area (ventilation area includes both bottom and side vents as well).  I know the standard recommendations is 15 to 20%, but look around and some of the others that have much more with either active controls or lots of area can control their temperatures better.  Do you have indoor(near peak and near ground) and outdoor temp data?  With the vents opening up at 70F, but you are still getting shoulder height measurements of 100F and  0F outside, my guess is that carefully added vents might allow you to control this better.  As a side note, a 100F inside/outside differential would be spectacular, and I know a few folks that would love it if they could maintain that much heat gain in the dead of winter.  Also, the flapper idea is interesting.  I would be concerned that the weight of the flapper is to much to allow the warm air to push the flap out of the way.  The interesting thing here is that you might be able to use a simple bi-metal spring to push the flap out of the way if it is light enough.

BTW, I have been wanting to use some of the open-source building performance tools to model greenhouses and greenhouse design.  If you know any students who understand this, I would love to work with them to apply some AI optimization techniques which are applicable to generative building design.  Then, if it is not to difficult to model up, we can build a simple model of your greenhouse and have the AI do some optimization on a design modification.  If anyone can help with the thermodynamics and building design, I can handle scraping the env data for your location, and the AI.  We would have to collaborate on the AI/thermo API so that they would work together, but I really am interested in this.
 
Mike Haasl
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Sorry, I was just mentioning the 100 degrees on sunny winter day as a warning that even on a cold day, if a greenhouse isn't vented it can get pretty darn hot.

My greenhouse is pretty tall and I can vent wonderfully with pretty small vents.  On an 85 degree sunny day I can keep it under 105 with three 4x8' vents up high that are open about 18" and two 2.5' by 6.5' vents down low that are fully open.  I'm not sure if you calculate based on the frame size of the vent or the amount of daylight when the vent is open.  Assuming the latter, I'm venting very well with 74 square feet of venting for an 800 sq ft greenhouse.  I'm sure it's heavily influenced by my 15' height difference between the vents.

The flapper for the solar thermal systems is fairly well detailed on Builditsolar.  They typically put a hardware cloth across the upper opening and then use a piece of garbage bag plastic as the flapper.  It lifts up effortlessly and once the airflow tries to reverse it gets sucked down onto the mesh and blocks airflow.
 
Ebo David
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I have not read, and really have wondered, if you should use the vent area or the max vent opened area.  If I find something on that I will let you know.  Please let me know if you find something.
if it is the former you are more than good enough.  If latter, 74 sq.ft. is roughly half the recommended area.  Is there some way to increase the distance opened for a test?  I would love to hear about the results.

The Builditsolar sounds good.  I would try something like that before going the termoacutuator route.
 
Phillip Stuckemeyer
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Thanks for all of the comments and suggestions.  I have been making some alterations in an attempt to increase the surface area of the collector and to improve the flow of hot air.  Here are some pictures.  You can see that I have added wings to the large stationary collector, and these wings can be pointed to the east in the morning, to the south in the mid-day, and to the west in the evening.  This seems to be working very well.  I am planning to use a garage door opener with an industrial computer to trigger the timed movement of the panels.  The main panel will always point South, and is too large and heavy to manipulate.  The garage door opener will only need to move a lever along a straight line about 2.5 foot in order to move the panels from one extreme to the other.  I am very excited about this modification.  I am also planning to replace the plastic sheeting with polycarbonate panels next year, and to build two more collectors for the other two windows.  Eventually, all three will be enclosed inside the greenhouse, which will improve efficiency.  On days when there is no sun, I plan to use a Rocket Mass Heater and to use the three collectors as an air duct to move the RMH heated air into the house.
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Phillip Stuckemeyer
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Mike Haasl wrote:When I first saw your trombe wall sketch I thought it was brilliant and I still do.  I thought you were going to provide the cold air from the lower window, let it sink to ground level and then let the greenhouse effect heat and raise it to the upstairs window.  I think that would really help it to move air.

Mike, you are correct about my original intention.  However, the bottom windows open to the cellar, and there is no direct air flow path from the house interior to the cellar.  I plan to house tilapia tanks in the cellar for an aquaponics system once the greenhouse is built, and the smell of the fish tanks is another concern.  I was a licensed tilapia grower in Virginia, but a sudden freeze in my detached greenhouse killed all the fish.  My current plan is to locate the fish tanks in the cellar, and the growing beds in the greenhouse, and to pump the water through the wall.  A Rocket Mass Heater (maybe two) will be added to keep the greenhouse within temperature tolerances in the nighttime and on cloudy days.

 
Ebo David
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An idea and a word of caution:

Take a look at thermoactuators (wax motors).  You may be able to come up with an arrangement where a couple of them push/pull a control rod to track the sun across the sky without the use of electronics...  I  know of some dead simple analog circuits that basically do the same thing, and require no computers.  If interested, hit me up in a couple of days and I'll see if I can find reference designs on the net.

Most fire-codes require that there be at least 2x egress points from each room.  You are effectively blocking off the emergency access out of the bottom window.  In case of fire you or someone might need to crawl out that window.  Please think about how you will accommodate that..  Someone could get hurt, the fire marshal could cite you, or nothing ever happen, BUT...
 
Ebo David
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@Phillip, look into heat exchangers.  I am not sure if there is some way to do it with a passive, or self powered system.  I'll have to cogitate on this one a bit...
 
Phillip Stuckemeyer
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Ebo David wrote:An idea and a word of caution:

Take a look at thermoactuators (wax motors).  You may be able to come up with an arrangement where a couple of them push/pull a control rod to track the sun across the sky without the use of electronics...  I  know of some dead simple analog circuits that basically do the same thing, and require no computers.  If interested, hit me up in a couple of days and I'll see if I can find reference designs on the net.

Most fire-codes require that there be at least 2x egress points from each room.  You are effectively blocking off the emergency access out of the bottom window.  In case of fire you or someone might need to crawl out that window.  Please think about how you will accommodate that..



David, I appreciate the thought, but I will go with what I know.  Building Automation and Control is my specialty:  Niagara Framework.  I have plenty of controllers, and I have been teaching field engineers how to design the control logic for the last 15 years.

Finally, emergency egress is not an issue.  The cellar also has windows on both the East and the West sides of the house.  There are 5 windows total, in addition to the large exterior exit door on the West.  Plenty of escape routes.
 
Ebo David
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@Phillip.  Sorry, I did not know about your background in control systems.  I am also glad to know that there are extra windows in that room.  I was just thinking of safety -- which I now know you took into account.
 
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