passive solar green houses

we want to put in a passive solar green house- a few questions.
i have seen pictures of them being built with tyres etc, but what would the best thermal mass be for the north, west and east walls. is concrete feasible- then soil banked up outside- how thick concrete- ? paint the concrete black??
should the two wings ( west and east walls) optimally be angled out at say 45 deg, to the back wall- so as to optimize on the early and late sun?

i am sure there will be many more question as this thread gets unpacked.
plan to have internal compost pits to add heating- heated water pipes running through the compost , into the plant area.

many thanks
cheers
wayne

The first question is if you have enough winter solar gain to overcome the loss on the glazing. Us West-Coasters tend to suffer in winter solar gain, one of the disadvantages of this side of the cascades as opposed to the eastern side.

hi Kyrt,
yup sure you are quite familiar with the PNW weather.
we are opting to build a greenhouse of sorts- but the passive solar ones the chinese have been building for years - really seem to have so many advantages- i know we dont get the light that other areas get. but the passive solar would be a huge benefit over the standard greenhouse.
we did also plan on a blanket to shroud the glazing ( plastic sheeting)at night.
my wife klikes the idea of it being attached to the south side of the house- with a small swimming pool- then i guess its going to be a rocket stove for heating the water - getting it to a mild tepid temp- no hot tub temps
cheers
wayne

If and when you build this, post a project thread! Would love to see how it comes together. We've got similar solar conditions to you guys here in the new england area for a large portion of the winter months...just gets WAY colder in the middle

Tristan Vitali wrote:We've got similar solar conditions to you guys here in the new england area for a large portion of the winter months..

You... do?

Huh, guess I just always assumed Eliot Coleman's work was less applicable here because of how low our solar gain is, but perhaps I was mistaken.

The only time I put a small compost pile in a greenhouse, it contaminated the air so badly that I couldn't stand to be in the greenhouse.

have seen some videos of the chinese set up- wonder how they are dealing with the compost?
i think the swimming pool idea is a bit far fetched- especially the heating thereof- but the thought is grand!!

Kyrt Ryder wrote:

Tristan Vitali wrote:We've got similar solar conditions to you guys here in the new england area for a large portion of the winter months..

You... do?

Huh, guess I just always assumed Eliot Coleman's work was less applicable here because of how low our solar gain is, but perhaps I was mistaken.

Hopes somewhat damaged.

I just looked this up. I can't speak to your [meaning Tristan] specific area, but at least in the case of Eliot Coleman's work, Harborside Maine averages 43 more days of sunlight per year than my hometown does, and over here on the west coast our summer is pretty much 100% sunny days. So I'm figuring an average of about 10 more days of sun in each of spring and Autumn and about 20 more days of sun in winter. While not massive that is significant, especially in the context of passive solar where that solar energy is being captured and held very well.

I wonder about the usefulness of modeling the solar gain for a greenhouse by using tables designed for generating solar electricity.

I have a standard greenhouse, with gaps around the glazing panels, windows, and doors. It is overcast today, snow is covering the roof. Temperature inside the greenhouse is 53F. Outside temperature is 34F. The only significant thermal mass inside the greenhouse is the dirt floor. I daydream about someday building a greenhouse into a hillside to take advantage of earth storage of heat, but even my rinky-dink greenhouse stores a lot of heat in the floor, and it captures significant heat even on overcast days.

I finished building the greenhouse about the day before our winter snows arrived, so I haven't had warm weather available to do caulking or weather stripping. I intend to get those done first thing in the spring before I need the greenhouse for starting tomatoes. Caulking won't help much with heat gain during the day, but it keeps night-time temperatures warmer.

Last year I put row-covers and cloches over plants in a greenhouse. That worked wonders for protecting frost sensitive plants.

Even without solar gain, the temperature in an an ideal carefully thought out passive solar greenhouse would approach the temperature of the earth. So perhaps around 50 F. Add day/night, and seasonal banking of heat, and a passive solar greenhouse like the one being contemplated is a really prudent way to build a greenhouse.

ok some more questions. with regards to R value versus light transmission%

1. i plan to have a stowable interior insulating blanket - to help retain heat at night( a roll up insulating mat )

2. so my two options for roofing material are-
a. triple polycarbonate 16 mm thick -R2.5 and light transmission of 74%
b. double polycarbonate only 6mm ( 1/4") R1.6 and a light transmission of 85%


bearing in mind that we dont have the bright sunny days here in the PNW. its our rainy- stormy season- so can be overcast- but the good thing is while its raining its not freezing!!!


any ideas
thanks wayne

ok seem to have found my own answer
a new type of double wall polycarbonate- R value 1.7 with a transmission %99 and a diffusion % 80
and its about as local as we can get on island here- its only 1000 miles away
cheers
wayne

wayne nicol wrote:ok seem to have found my own answer
a new type of double wall polycarbonate- R value 1.7 with a transmission %99 and a diffusion % 80
and its about as local as we can get on island here- its only 1000 miles away
cheers
wayne

Care to share what brand that is? It sounds great!

Kyrt Ryder wrote:Hopes somewhat damaged.

I just looked this up. I can't speak to your [meaning Tristan] specific area, but at least in the case of Eliot Coleman's work, Harborside Maine averages 43 more days of sunlight per year than my hometown does, and over here on the west coast our summer is pretty much 100% sunny days. So I'm figuring an average of about 10 more days of sun in each of spring and Autumn and about 20 more days of sun in winter. While not massive that is significant, especially in the context of passive solar where that solar energy is being captured and held very well.

Yeah - Eliot Coleman is a ways south of here, closer to coast. They tend to have less sun in the spring through fall due to the marine layer effect while we have less in the winter due to Canada (thanks guys! ) We probably do get a little more sun over the winter on average (mostly in February when the really cold/dry airmasses come to play), but it comes with nighttime temperatures in the below zero territory (in *F). For example, last february I think we had around 4 nights that didn't drop below zero and maybe 5 of those didn't drop below -10*F! That kind of nighttime temperature is a hard battle for a low sun angle and short day length to win when talking passive solar.

You might not get quite as much protection as we get here with the layers of plastic hoop house and row covers (I believe Eliot calls for roughly 1 full USDA zone per layer), but you're most likely working from a higher baseline, too

hi Dave
yup found it down in the vancouver area
http://www.bwgreenhouse.com/ link to their business- speak to James- say wayne from the queen charlotte islands sent you!!
he may be able to put you on to someone closer, or they may have a branch out there
the product is called "solar soft"
cheers
wayne