Size of eaves on a Barn - looking for input

[stumax]

Morning All,

I am at the point in building my 40 x 40 monitor barn that I am ready to start building a simple gable 4/12 roof.    I have see barns with almost no eaves (roof overhang) and I have seen some with 18 inch eaves.  I am more concerned with function over form.  What you think of no eaves versus eaves and if there are eaves how big of an eave do you need?

I am located in the mountains of Virginia on the border with West Virginia.  We have average rain and snow. 

[OneWithWood]

I like 18-24" eaves for the protection from sun and rain.

[Raider Bill]

I agree with OWW.

[thecfarm]

I like the look of a overhang,on the gables.
My house is like that. Looks good to me.

[Brad_bb]

One of my considerations (especially when designing the house), is to consider the angle of the sun.  Many designers today will design the length of the eaves, especially on the south side, to not allow direct sunlight in summer.  There are cad design programs which can incorporate the angle of the sun during the summer relative to your latitude.  You don't want sun shining in  the windows in summer.  The angle of the sun is lower in winter when you may want the sun to shine in to create passive heating.

[stumax]

Thanks for everyones input. The reason for the angle of the sun seems like the most logical.  I dont have a cad program so I used the NOAA Solar Position Calculator.  It gave me a solar declination of 23.1 degrees for a equinox around June 20th.  Using a triangle calculator this gave me an overhang of 20.4 inches.  since my windows will be slightly higher than the lower roof line, I am going with a 18inch overhang.  Plus 18 inches is an easier number for me to deal with than 20.4.  That of course relies on that the previous math is all correct :D

[Brian_Weekley]

I dont have a cad program so I used the NOAA Solar Position Calculator.  It gave me a solar declination of 23.1 degrees for a equinox around June 20th.

In case you're interested, "Sketchup" is a 3D CAD program you can download and use for free.  Many people on this forum use it for their designs.  Since Sketchup was originally developed by Google, it has a lot of really neat features.  For example, you can use Google Earth to import the actual geographic location and the satellite images into your drawing.  Another great feature is that you can use it to study the effect of light/shadows based on the location, time of day, and time of year.  This is extremely useful for evaluating overhangs as you describe or other things like how the location of trees or outbuildings might impact solar panels.

[stumax]

It might be time to learn Sketchup.  I have heard it has a steep learning curve so i have avoided it. 

[canopy]

It gave me a solar declination of 23.1 degrees for a equinox around June 20th...

Sounds like you will only have sufficient shade on one single day out of the year then. I would think one would want to look at the desired start and end dates rather than just the peak day?

I found sketchup easy enough to learn as some do and some don't. The high quality training videos and q&a's available were straight forward enough for me. I'm at the point now that I simply will not embark on any sort of DIY project without first drawing it in sketchup. Just invaluable and yet it's free!