Solar Greenhouse design

[bertiefox]

Sorry if there is information already in one of the forums but I couldn't find it using 'search'.

I have just started a solar greenhouse which will be 12 metres long, 3 metres deep and around ten feet tall at the ridge. It has an earth bank at the northern wall.

I have varying advice from friends here, about whether to build the walls out of concrete blocks or wood, with insulation materials. I intend to use 20 litre plastic containers painted red to build a thermal mass inside the north wall.

The southern roof will be polycarbonate panels, the northern roof metal sheet,with insulation beneath, and painted below or silver foiled to reflect the light.

Can anybody who has built such a greenhouse advise me of the main points to be borne in mind? For example, would concrete block walls be better for thermal protection, or would wood, much easier to work with, be just as effective if insulated?

Are there any other problems I'm likely to encounter as I build this?

[Joseph Lofthouse]

Great project.

In my climate, I would use the north wall to store as much summer heat as possible... Thus for me, the north wall would be made out of rockwork... Might even put air channels behind the rockwork to make heat transfer more efficient (and lower the daily temperature swings).

[circumspice]

I sometimes wonder if I could build a greenhouse on an opposite principle. I'd like to extend the cool weather season in my area. I have a very long growing season & for the most part, it is all HOT. My cold weather season isn't mild enough to grow much of anything unless protected. Growing cool season veggies seems to be out of my reach. Everything that requires longer cool weather conditions either bolts straight to seed or just dies.

[oxbowfarm]

I Googled the Loire Valley of France, it sounds like a paradise. If your average minimum temp in January and February is 2degC you actually don't need much of a greenhouse at all to be able to grow cold hardy crops like greens. If you are looking to grow warm season stuff in winter it looks like more than insulation you'd need some kind of supplemental lighting with only average 70 hours of sunlight in January. If you are going to use masonry as thermal mass you need to insulate it from the exterior.

I think it is easier if not prettier to build a wooden wall and then use water in drums as thermal mass. You can build benches right on top of the drums.

Is the greenhouse for propagation or for growing food out of season?

[bertiefox]

oxbowfarm..... Unfortunately I think those temperatures only apply to the actual valley of the Loire where they do enjoy a microclimate! Unfortunately we are 25 km or so higher up and to the north, where we have had temperatures of minus 20C in January and February in some years. Luckily this year so far looks like being mild as minus 6C is the worst so far!
I'm planning to use my solar house to propagate early vegetables and to grow some winter greens, but the main purpose is to have somewhere to put our tender and semi tender plants in winter. We can just about keep a guava alive in a building with a polycarb roof and stone walls in the earth on three sides (and no heating) , but they suffer from the lack of light. I'm hoping the solar house, with a little bit of wood heating from a stove on the coldest nights, will keep a few more plants alive.
Thanks for the suggestion about the walls, Joseph. I'm tending towards building with blocks now, partly because they are a cheaper and more solid and long lasting option, but your idea makes me think I might use some of the plentiful spare stone we have around the place to make a really thick north wall with a cavity filled with rubble, as a thermal mass. Would also make it stronger to resist the earth bank behind it!
I've been costing the project out and coming up with some scary figures, but I am trying to convince myself this would be a great investment for the future, if I build it to last! It will still cost a tiny fraction of a bought greenhouse of this size and which would have nothing like the heat keeping properties.

[richardw]

There is another thread where this subject has been talked about already

alanbishop.proboards.com/index.cgi?board=alt&action=display&thread=6009&page=2

In that thread it shows my tunnelhouse as it was then but since then ive been changing it because of lessons learnt,comparing climates to yours bertiefox you get colder min temps than what i do so if you are going to build a solar greenhouse house you need to build it so you get as much insulation as you can.
The changes i'm making at the moment are to improve the insulation more even though its been pretty good up to now,but i cant keep tomatoes growing all winter because it gets down to about 3-4Cdeg inside when its -8 or -9deg outside,so tomatoes tend to slowly die at that temp,i also plan to and this is something you need to look to as well and that is to have double skin/plastic or glass roof,ive only got a single layer at the moment.
The two end walls get cold and this tends to go through into the inside so i'm building out these two walls for better for thermal protection,in this photo the rock work also connects up to another hothouse thats in the early stages of been built,i plan to build the same on the other side of the door as well.


The other end wall is where i'm putting all the rock and shingle that is of no use,because the tunnelhouse works so wall in summer and that it doent over heat the window does not get opened at all so this window will be concreted up and stone and shingle will come out about 3-4 meters and up to the roof.




The inside is been changed also from growing in old baths to stone wall beds,this also will improve thermal protection.



I'm lucky that have have all the building material i need only a few meters away and later on this hole in ground will be a water gallery as its only another 2-3 meters down to having year round water supply.If you dont have the same access to stone that you are planing to use block,i reckon that would be just as good but any walls need to be earthed up on the outside to work best

[hotwired]

I'll stick my 2-cents in. Cornell University offers free books under the "fair use doctrine". There are three FREE books on greenhouses with lots of good info.

Hobby Greenhouses
- Types of Greenhouses
- Locating Your Greenhouse
- Designing Your Greenhouse
- Types of Frames
- Beds for Growing Small Plants
- Greenhouse Heating
- Greenhouse Ventilation and Cooling
- Other Greenhouse Necessities
- List of Plans

Greenhouses for Homeowners and Gardeners
It is a 200 page free digital book (6.9MB) or $30.00 if you print it. Whether it means tending to a collection of exotic houseplants or cultivating a year-round crop of vegetables, greenhouse gardening appeals to many people for many different reasons. A greenhouse can help garden enthusiasts get through the cold part of the year; it fills a void during winter, when weather prohibits gardening outdoors. Home greenhouses are ideal for introducing children to nature and showing them how seeds develop into flowering plants or nutritious vegetables. Retirees often adopt greenhouse gardening as a hobby to enjoy during their retirement years.

Greenhouse Engineering
It is a 212 page free digital book (2.5MB) or $30.00 if you print it. This manual contains current information needed to plan, construct, and control the commercial greenhouse. Major sections describe various structures, methods of materials handling, the greenhouse environment, and energy conservation. Other topics include plans for noncommercial greenhouses, access for the handicapped, and remodeling existing greenhouses. A large appendix includes conversion tables, worksheets for performing calculations, and sources of greenhouse construction materials and contractors. (1994)

One thing I would seriously consider is installing mirrors on the North wall to increase light during the Winter's low sun. www.hotwiredgardens.com/pdf/Capturing_More_Sunlight_with_Mirrors_on_North_wall.pdf

Good Luck with you greenhouse efforts. you're going to love having one.

Hotwired NY 5b
www.HotwiredGardens.com

[mountaindweller]

Richard you have the pretties greenhouse ever!
To the question: there are two different things, one is the thermal mass, more or less the heat what a material can store the other is the insulation value. Those material with high thermal mass do insulate very badly. The insulation value of concrete is lousy, but uf you use blocks you can fill some insulation inside, but you will still have thermal bridges. Unfortunately, insulation value is much much more important to the temperature inside than thermal mass if not the medieval castles (you might even live in one given you location) would have been nice and warm.
Timber in a greenhouse, I don't know. It does not like moisture. To get any insulation you will need sandwiched walls with with insulation in between (believe me that I live in a timber house without insulation).
The thermal mass comes inside, were it can heat up during the day through glass or whatever you choose and the heat is trapped because the walls are insulated.
Second you must really watch for condensation, plants do produce a lot of moisture, that means first you need good ventilation and second you don't want crannies or layered materials were moisture can enter and condensate.
If you can get secondhand windows from supermarket freezers they have good insulation.

[steev]

Richardw, I'm so impressed by the functional beauty of your greenhouse; it's a blessing to see the value of grunt labor enough to actually carry it off to such a fine result.

[bertiefox]

FABULOUS greenhouse! The use of all that stone gives me ideas too as we have plenty of local stone around the place that could be used to beautify the structure and add mass.

[richardw]

Thanks fella's,my nephews think i'm completely mad that i'm digging all the rock out by hand,"why dont you get a digger"?,i said "show me a digger that can sort out all the different sized rocks,some with flat faces,others for in-fulling,some with two flat faces for corners and then also screen &wash the shingle",the problem is the young ones today are afraid of hard work.
I'm about 100km from the nearest place that you can buy mortar sand and the premix concrete shingle so if its right under my feet,its only a matter of getting outa bed early and grabbing the pick and shovel.

[richardw]

Jan 30, 2013 21:19:42 GMT -5 mountaindweller said:

If you can get secondhand windows from supermarket freezers they have good insulation.

Thats a dam good thought........... ;D ;D

[steev]

Don't want to crab about the young today too much, having been largely useless as tits on a boar into my forties, but I never paid to go to a gym and walk on a treadmill.

[YoungAllotmenteer]

Jan 31, 2013 13:20:08 GMT -5 richardw said:

Thanks fella's,my nephews think i'm completely mad that i'm digging all the rock out by hand,"why dont you get a digger"?,i said "show me a digger that can sort out all the different sized rocks,some with flat faces,others for in-fulling,some with two flat faces for corners and then also screen &wash the shingle",the problem is the young ones today are afraid of hard work.
I'm about 100km from the nearest place that you can buy mortar sand and the premix concrete shingle so if its right under my feet,its only a matter of getting outa bed early and grabbing the pick and shovel.

Worth the work, stunning greenhouse.

[steev]

"Why don't you get a digger?" differs only in degree from "Why don't you buy the materials and hire someone to build it for you?". Unclear on the concept.