[Strawbale] attached greenhouse questions

[Sherwood Botsford]

SArjuna at aol.com wrote:
>      We'll be starting work on our SB house this spring, and still don't have 
> the info. we need about an attached greenhouse.   I've borrowed a passle of 
> library books on the subject, only to find that one writer contradicts another.
>
>      Take the angle of the glazing, for instance.   Most seem to say that at 
> 43 degrees of latitude in WI, USA the angle of the glazed surface should be 
> about 53 degrees, to get the most winter sun.   But one expert insists that 
> vertical is far better because with sloped glazing there will be severe 
> overheating in late spring and fall.   She also says that in midwilnter the vertical 
> glazing may actually yield more light, as it picks up refleccted llight from 
> snow.   Even without that reflection, she says that in Edmonton at Christmas the 
> average daily solar radiation striking a south-facing vertical wall is only 14 
> watts per sq. yard less than what strikes a wall at 60 degrees.
>
>      Vertical has the advantages of:
>      - being easier to install and seal
>      - being cheaper as the glass need not be tempered
>      - being less prone to overheating
>      - being more energy-efficient
>      - allowing you to stand up in a larger area
>
>      I'd appreciate hearing from some experienced attached greenhouse users.
>
>   
Another advantage of vertical is that it doesn't get as dirty.  At 43 
degrees, a window that is at right angles at solstice would be only 24 
degrees from vertical (90- Lat - Orbital Inclination).   To go vertical 
would decrease insolation proportional to cosine of the incident angle.  
Better than 90%.  My not very humble opinion:  the dirt would make up 
for it.

Over heating in green houses is almost always the problem. 

My suggestion:  Pour the foundation for the greenhouse, but don't build it.
Instead build a cheap PVC and sheet plastic summer greenhouse and play 
with it for at least two years.  Then revisit the idea of an attached 
greenhouse.

Energy efficient and green house are an oxymoron.

I have one green house built with scrap windows and an old shed.  We are 
still eating frozen bell peppers from it.  My next one will be designed 
to get warm in April, and try to stay warm until October.  In winter it 
is so dark here, that nothing will thrive.  But I can use a green house 
to turn a 3  month frost free season into a 5 month one.
And THAT is worth doing.