Attached greenhouse questions

Hello,

I am not sure if this should go here or in the greenhouse forum. We are not building an Earthship but want to include an attached greenhouse to our build. I've read some posts here about pros/cons but didn't want to hijack someone else's post so sorry if duplicate.

We are building a home and would like to add an attached greenhouse to it. This will not be our main source for growing. The footprint is only 12'x25'. Maybe some  ornamentals or things that do not need direct sun. We would also like to take advantage of any heat source in the winter. We also felt that mimicking a greenhouse like used on an Earthship would be a good idea. However, I am reading posts about not to do slanted windows and do not have an open floor plan into the house. Which is something we really wanted to do.
So, we can accept vertical windows since we feel we will still get good sunlight in. We still would like to have the open concept with nothing dividing the house/greenhouse. In other words, no doors.
We live in northern Arizona. Summers can get into the 90's for a few days here and there. Winters get down into the teens at times but mostly the high 20's. We have a monsoon season(s) where the humidity is high but otherwise it is fairly dry. The greenhouse would be south facing. At this time we are not sure if we will use our grey water for this greenhouse or for everything outside. It would be easier for us to just have everything go outside and just use fresh water for anything inside. We are off grid so only solar/gen and we truck our water in.
Also, we would like to do some sort of RMH for heat and would consider placing it at the edge of the house at the open area between the house/greenhouse and would be open to running any piping into the greenhouse to keep it warm at night during the winter.

So, is it really bad to have an open concept between the house and greenhouse or can we pull it off? If not, would according glass doors work so that we can open it up when we want?
Any pros/cons to doing an attached greenhouse?
Any tips or tricks to make the best out of it?

Thank you for any help

Jim

Jim, I added this to the greenhouse forum for you. I figure it can't hurt to widen your audience a bit.

Curious to see responses, as our current plans for SW Michigan involve an attached south facing greenhouse running the length of the house, with a sloping roof  and near vertical southernmost wall. We're not planning on closing the greenhouse off from the house itself, maybe some curtains, but no solid wall.

We're also planning on using an RMH for heating the house, but it won't be tasked with heating the greenhouse - of course, with no division, we'll be heating the greenhouse intentionally or not, but the focus will be the interior of the house.

I've never had an attached greenhouse myself, so I can only relate a bit of info from my mother, who did. They had a house in southern NJ with a attached glass 8' x 16' greenhouse that was walled off from the living space. Initially it had an open doorway which they quickly added a closeable door to out of necessity. During the winter the temperature would go down to below freezing, killing her plants. So she added a small heater to keep things above freezing. If she left the door open, the house chilled down significantly causing the heater to kick on.

During the summer on a sunny day the greenhouse roasted. Again, if the door was left open it heated up the house and the air conditioning kicked on. So she added a shade curtain and installed ventilation windows with a fan. That kept the greenhouse interior bearable and she could open the door in the evenings.

She used her greenhouse the entire time she lived there, but it didn't turn out to be the pleasant year around oasis that she had planned. But spring and fall her living area was always open to the greenhouse. When I walked into her home during those months, the place smelled pleasantly of greenhouse.

Personally I wouldn't use greywater in an open attached greenhouse because the home would smell like greywater, rather than a pleasing greenhousE.

I don't have experience but some reading.
Build I Solar has some great info on these low mass sun spaces:
http://www.builditsolar.com/Projects/Sunspace/LowMassSunspace/TestsLowMassSunspace.htm

Without a way of separating the living space from the sun space you get solar gain on winter days, but lose heat out of the glazing at night.
On summer days the solar gain is entirely unwanted...

I would use deciduous plants south of the greenhouse,along with seasonal shade cloth barriers to prevent solar gain.
In addition,the greenhouse should have the ability to open windows for cross ventilation.
You might also want to consider a system like the one discussed here: http://forums.gardenweb.com/discussions/1607983/subterranean-heating-cooling-system
It is an air to soil heat exchanger, more efficient because it uses the condensation  and evaporation (phase changes) of water vapor to transfer the heat.

For retaining winter solar gain,  vents can set up a convection current that brings cooler air from the living quarters to be warmed in the sunspace returned to the house proper. One way flaps prevent the convection currents from  reversing during the colder night time hours.
A thermal blanket could be used either on the inside or the outside of the glazing during the night,but it's more work for the occupants.

As far growing things in the space, you can't really suck heat out of a sunspace and still expect it be warm.

So heat the house from an attached yet thermally separated greenhouse,or heat the entire shebang and and mitigate heat lost via the greenhouse glazing.
Summer is just a pain,but can be mitigated.

Being in a hot-summer climate, you want to build a passive greenhouse with a solid roof in order to minimize solar gain in summer. I'm in the process of building a detached greenhouse right (in California) now that I did a lot of research on to plan it. Building a thermal mass wall below the south-facing windows will help heat the room in the winter. An arbor should be built to extend out from the south wall that will shade the windows in the summer but allow solar access in winter. Grow a deciduous fruit vine on it for better shade. You will need to calculate how far to extend the arbor based on where you live to be able to have the sun hit the windows up until the time in the spring when the weather starts to get too warm. For me that is the end of May. The whole object is to maximize solar gain in winter but minimize it it in the summer! I've attached two images showing a simple attached greenhouse that is suitable for hot-summer areas and a diagram that shows the way to calculate how far the roof or arbor needs to extend to shade the windows in summer. These came from a Mother News article on How to Build a Passive Solar Greenhouse. The problem with the article is that many of the images are for areas with cooler summer climates.

We put one on our house and we love it. I even put a hot tub inside. We did however make an error on the slope of glass.  We built it as if it were an earthship and now we have to change it someday. LOL pay close attention to that slope.

Jim -- and Peter --

I've worked with a lot of greenhouses professionally and seen first hand how difficult it can be to control their climates. Most glazing materials (glass or plastic) are so hugely incredibly inefficient compared to a wall, building an attached greenhouses with no separator is a lot like asking for a climate burden on the home (particularly in Arizona. I think there are more justifications for Michigan). So I would always recommend a separator like sliding glass doors and leave them open when it's nice out. BUT if you realllly want the open floor plan concept, there's a few things you can do:

1. add a ton of thermal mass in the greenhouse. You want something extra to absorb the excess heat, other than the air of your home.  A partial trombe wall between the spaces would be interesting here. I don't have any examples, but have always thought it would be a great idea.

2. Upgrade to really good glazing materials... worth the investment for your future heating cooling bills. Amory Lovins greenhouse / home uses an R-14 windows! Maybe you don't need to go that far, but choose a glazing that is as efficient as possible.

3. As Kit already said Jim should be using an insulated roof, or heavy shading cloth to control heat gain. Basically, alter the structure to reduce direct light into the home. Be sure to make a sketch of the greenhouse with solar angles for different times of the year to ensure you are not getting a ton of direct heat gain into the home in the summer.

The one successful example of an integrated floor plan / greenhouse I have seen is Amory Lovins home from the Rocky Mountain Insitute. I write about it as a case study in my recent book
The Year Round Solar Greenhouse

I'd also recommend the book for other tips... I have a chapter on attached greenhouses and how to build them successfully.

You might consider a solarium, instead of a greenhouse.  

The excessive glazing in a greenhouse (often with roof glazed as well as the walls) is a source of excessive heat gain/heat loss; this is particularly true if the Sunward wall is sloped glass, allowing more summer sun to penetrate.

 With a solarium the glass is often vertical, and sometimes with a roof overhang that cuts out a great deal of the Summer sun.  In this way, the solarium only gains the maximum sun in the winter, when your house could use the solar gain the most.  The solarium is primarily a room on a house with it's Sunward wall made of glass.  All other walls, and the roof, should be insulated from heat loss/gain, and thermal mass could be incorporated on the adjoining house walls to act as heat and cool storage for when it's most needed.  If the solar is closed off somewhat, the solarium acts like a trombe wall that is also a living space.  

The area does not have to be walled off, but it is recommended, so that the heating can be moderated by opening doors and/or windows.  The primary consideration is with moisture, so choosing plants/systems with less water needs/transpiration into your house should be in order... while excess heat/loss could also be big issues with too much glazing if you do go the greenhouse route instead of a solarium.      

Hello,

First, please do not judge my Sketchup talents  

Here is a visual of what we want. I guess technically this would not be considered a greenhouse so I apologize for using the wrong term.

It sounds like you want a greenhouse 50% for heat and 50% for food or greenery?     It looks like your graphic depiction above would work with the following features.

The cons of an attached and open, earth-based greenhouse are:  

- -oven-roasting heat it will provide for the summer if it has a glass ceiling;
-- a lot of water and potentially 12-month wet soil around your foundation and floor;  
-- mold and bacteria issues that are a part of organic food-growing soil, being in the air you breathe
      and tracked into the rest of the house.
-- gnats and other bugs that will be in a greenhouse.
-- the potential for it so be too cold in winter, just when you need the heat.

But double-paned, glass conservatories have been very successful on a concrete slab with a drain, often in the middle, with concrete slanted towards the drain, constructed over a moisture barrier.  Growing plants in large containers (a minimum of knee-high pots/containers keep the mold/bug issues to a minimum, and can provide a lot of food.    I have a passive solar house that works really well, and combining passive solar features, instead of greenhouse features ought to be helpful.   These features work in hot conditions (by blocking out hot sun) as well as allowing heat in in winter, then keeping it in before the sun moves off the windows.  

Even in the best of conditions, it can take 4-5 hours for morning sun to raise the temp inside 5 degrees on a cold day through windows.  It's not a miracle worker,  but by afternoon it can supplement the heat source, and be quite warm going into nighttime.  The bright light is a psychologically pleasant feature, even if the day is gray and overcast.  I am sometimes astonished at how well my passive-solar setup works, yet it doesn't turn the house into an oven in the summer.

The passive solar features for a conservatory on a concrete slab could include:


-- living area is a long, narrow rectangle running east to west, ideally 15 feet wide in cold areas, 20 feet wide in moderate areas  (lowest temp 32 F for fewer than 20 days a year)

-- kitchen on north (coldest) side of house because it produces its own heat, and we are on our feet, being most active in the kitchen

-- bedrooms in coldest area, since we are under covers and probably don't want bright sunlight coming in.

-- longest wall is south-facing in Northern Hemisphere

-- Western wall is also full of windows to catch heat in late afternoon, also has thermal curtains to close out summer heat, keep in winter heat

-- solid, well-insulated roof over conservatory (R-30 to R-60 )

-- tall double-pane windows with insulated walls between, 75% windows, 25% well-insulated walls.  Not Low-E windows, which cut out too much heat.  In some areas Low-E are to code, so you may have difficulty finding just plain double-pane windows.

-- windows start 2-3 feet from the floor, wall insulated below them

-- small eave, 6" or so" projection from the roof so there is no shade on windows from eaves.

-- no trees or shrubs that block sun, preferably all day.

-- thermal curtains and shades for the inside, on windows, to be closed at or before sunset in winter to keep heat in, and closed on summer afternoons to keep heat out.

The only thing I would add about your depiction is that putting a door in the conservatory area is a big heat loser.  Opening and closing it many times during a day could potentially lose more heat than it can produce.   An area that is trying to amass a lot of heat should not be disturbed.

To keep things easy, it helps to put an entry area into another part of the house where wet coats, muddy boots, shoes can be hung so they don't make a mess, with enough room to take them off and store them.

Thank you for the replies and suggestions. I think we will be accomplishing many key points that were suggested. Also, the house will be 3' off the ground on piers with skirting. We will need to build up the ground in the greenhouse or will have to step down into it from the house. Not sure which way is best. (Combo of both?)
We are debating placing the RMH at the south part of the house at the meeting of house no greenhouse. If this can be done efficiently (never built one) we think it will help heat the greenhouse too. I will post a separate thread about that in the RMH forum but any feedback on this?

Jim

I've lived in houses heated solely by attached greenhouses for the past 20 years. It's a high desert climate with much colder winters than yours and not as hot summers. I'm really glad our system involves removing the glazing entirely for the summer, as the plants would be roasted by early summer if the glazing were to stay on. The greenhouse on my living space is only 7 x 40 feet, and covers the whole south side of the house, exactly south facing. It would make a good solar cooker in midsummer if left on, I think. THough ours is a sloped glazing, whereas a vertical glazing is less prone to overheating. But overheating is a real issue in Arizona, so really do design so that you can open up the sunspace to maximize ventilation, and can close the sunspace off from the house. I second the suggestion for thermal mass, but you really should have more than "a ton of thermal mass"!

I'm building a new house and have a similar decision to make as the outside ground is 2 feet lower than the floor of the house. I vacillate between thinking raised beds or a recessed path would be best for comfort and ease, and thinking if I put the beds at ground level, I'd get an additional 2 feet of solar heat collecting area, and can more easily grow a small tree or two in there.

In our case, the other piece of the puzzle is John Hait's passive annualized heat storage.  We want the excess heat in the summer, so that we can pull it down into the subsoil beneath and around the house, raising the ground temperature and providing a substantial portion of our winter heating.

I am mildly disturbed by the suggestion that it is a bad thing to have healthy soil in our human living environment.

I had one and loved it, we ended up removing it because we put an addition on due to a growing family, but intend to build another real soon. Yes we loved it that much.

I do not have much to add except that I saw nothing about building it to ward off snakes. I HATE SNAKES and I live in Maine, the only state in the nation that does not have poisonous ones. You might want to ensure it is snake proof as they are attracted to greenhouses.

Jim, putting the house 3 feet up in the air will lose a ton of heat out the floor unless it is very thickly insulated.  My passive solar setup works because the floor is near the constant temp of 50 degrees of the soil underneath it.   Having the floor 3 feet up allows freezing air underneath it, and it will take extra heat to heat the interior, even in a conventional house.  

If you are thinking of putting a "skirt" around it to block air, unless that sits on a foundation of some sort, rats, mice, rabbits will dig under it and nest under it, leaving dangerous droppings, tearing away at insulation, getting into walls and chewing through pipe openings to get into subflooring and possibly inside.   If you put decking up against the house it gives them a hidden place to hang out, dig, come and go in safety where you won't even see it happening.   I've had all of this happen, I am not speculating.

I have all decking 18" away from the wall of the building.  with deck "bridges" out each door, and I still have to watch under the bridges.  The 18 inches gives me room to work, as well, and I can easily keep an eye on things.

Having the greenhouse lower than the house would work because heat rises, so it might actually move more quickly into the living area, and you could take advantage of the hotter air at the top of the greenhouse, as long as your ceiling in your living area is not too high.

------------------
Peter, healthy soil contains extremely high levels of bacteria, mold, and fungi, which are "healthy" for plants, but not for human lungs, especially in a zone where there will be a lot of heat.  Yes, some people can do okay with attached greenhouses.  But I would not put babies, small children or the elderly in a situation like that.  Even as Rebecca mentioned, they removed the glass in the summer, I assume they had screens, and there was a serious airing out of the area for probably more than 6 months out of the year.  The air coming off the soil had a way to escape, and all of it didn't go inside where they were living.

Have you ever seen that TV show where they English ladies go in and clean houses where people haven't cleaned in years?  They have done a few farms where the houses didn't look too bad.  But when they took bacteria readings they were off the charts and in the unhealthy limit for humans.  Not to be mororse, but that's why we bury things, so the soil critters will get rid of them.

Our greenhouses are flexible plastic, so we just roll them up and keep them tied under the eaves all summer. The south wall of the house (like all its other walls) is nice thick adobe with windows and doors, so in summer it's a conventional external wall, and in winter, it's a massive thermal mass storage for the greenhouse. No screens. In my personal greenhouse I don't plant the whole floor area so it doesn't happen to get very damp. In some other greenhouses at our school, the planting area is much larger, and the attached house much smaller, so it does get damp, with wood frames swelling and everything. That building is a long (E-W) row of tiny single rooms, but I've never noticed any lung infections or breathing problems in the people living there. They seem to be a healthy bunch.

I think it's just a matter of what you individually feel is a healthy living environment. If it bothers you, don't do it. It doesn't bother me, and I'm looking forward to increasing the growing area in my attached greenhouse when I move to a place with running water. I'm actually excited about it! (...filling notebooks with possible layouts for the planting beds and path...)

Lindsey Schiller wrote:Jim -- and Peter --

I've worked with a lot of greenhouses professionally and seen first hand how difficult it can be to control their climates. Most glazing materials (glass or plastic) are so hugely incredibly inefficient compared to a wall, building an attached greenhouses with no separator is a lot like asking for a climate burden on the home (particularly in Arizona. I think there are more justifications for Michigan). So I would always recommend a separator like sliding glass doors and leave them open when it's nice out. BUT if you realllly want the open floor plan concept, there's a few things you can do:

1. add a ton of thermal mass in the greenhouse. You want something extra to absorb the excess heat, other than the air of your home.  A partial trombe wall between the spaces would be interesting here. I don't have any examples, but have always thought it would be a great idea.

2. Upgrade to really good glazing materials... worth the investment for your future heating cooling bills. Amory Lovins greenhouse / home uses an R-14 windows! Maybe you don't need to go that far, but choose a glazing that is as efficient as possible.

3. As Kit already said Jim should be using an insulated roof, or heavy shading cloth to control heat gain. Basically, alter the structure to reduce direct light into the home. Be sure to make a sketch of the greenhouse with solar angles for different times of the year to ensure you are not getting a ton of direct heat gain into the home in the summer.

The one successful example of an integrated floor plan / greenhouse I have seen is Amory Lovins home from the Rocky Mountain Insitute. I write about it as a case study in my recent book
The Year Round Solar Greenhouse

I'd also recommend the book for other tips... I have a chapter on attached greenhouses and how to build them successfully.

I was going to recommend the above book,  but the author has done a better job than I could, so I'd just like to add as a disinterested party that this really is an excellent book and one well worth reading if you're thinking about building a greenhouse to maximise solar energy appropriately for your climate. I particularly like the emphasis on data, rather than mere opinion.

I was also going to note for people not in your area, that some building codes forbid open plan greenhouse to house. Here in the uk, we have to have external quality doors between greenhouse and house, with good reason. Even in our relatively moderate winters, you lose a lot of heat.

I used to have a house with a fairly basic south facing attached greenhouse for passive solar gain. In theory it should have been great. It was south facing, with vents/windows high up, opening directly into the upstairs bedroom. In practice though, I was unconvinced that it added much heat to the building in winter and it made the room going on to it darker. I'd consul peoplein your climate with exemplars before building myself:-)