Macro to get the default roof overhang?

[ACADuser]

Is there a ruby variable that would return the default roof overhang value?

I'm using this in a roof ventilation calculation text object. 

I used 1.4' as a constant in the version.

 

Ventilation Requirement Calculation

Attic %$attic_area.round(0)% sq ft / 150 = %($attic_area/150).round(1)% sq ft. required ventilation area

%$soffit_Length% lineal feet of soffit x 1.4' width vented area

= %($soffit_Length*1.4).round(2)% sq ft vented soffit x 0.08153 (11.74 sq.in. vent per sq ft / 144)

Soffit Vents Total %($soffit_Vent=$soffit_Length*1.4*0.08153).round(2)% sq ft

Off ridge Vents 3 ea 4' = 414sq in / 144 = %$ridge_Vent = 2.9% sq ft

%($ridge_Vent.to_f + $soffit_Vent.to_f ).round(2)% sq ft vent area provided (%$soffit_Vent.round(2)%+%$ridge_Vent.round(2)%)

 

 

[Joe_Carrick]

You could use the:

• projected_overhang_area

NVP's for each roof plane to determine the amount of soffit vents.

Of course with a gable end roof plane that might not be 100% accurate since you would only want soffit vents at the eave and not at the rake.

 

[Joe_Carrick]

Here in California with the wildfire problems I like to design "Unvented Attics".  

 

Basically that means the roof is the thermal barrier and there are a couple of additional code requirements.  See IRC/CRC R806.5.

 

Typically I would use an HRS (Heat Recovery System) for energy conservation - this actually requires an unvented attic.

[ACADuser]

Thanks Joe.

BTW what insulation type & R value are you using for roof plane?

[Joe_Carrick]

2 minutes ago, ACADuser said:

Thanks Joe.

BTW what insulation type & R value are you using for roof plane?

Usually SIPs.  R value depends on the energy calcs which can require a thicker SIP.

[ACADuser]

Is the open or closed cell spray foam any cheaper in your are?

 

[ACADuser]

I tried this in a text object without success:

"Projected Overhang Area: #{projected_overhang_area}"

[Joe_Carrick]

It would have to be in a macro accessing a roof plane. (Roof Label or Roof Plane Schedule)

 

This requires a more sophisticated approach than just a text box. - but might work if the text box has an arrow connected to a roof plane.

[ACADuser]

OK Thanks

 

[Renerabbitt]

11 hours ago, ACADuser said:

Is there a ruby variable that would return the default roof overhang value?

I'm using this in a roof ventilation calculation text object. 

I used 1.4' as a constant in the version.

 

Ventilation Requirement Calculation

Attic %$attic_area.round(0)% sq ft / 150 = %($attic_area/150).round(1)% sq ft. required ventilation area

%$soffit_Length% lineal feet of soffit x 1.4' width vented area

= %($soffit_Length*1.4).round(2)% sq ft vented soffit x 0.08153 (11.74 sq.in. vent per sq ft / 144)

Soffit Vents Total %($soffit_Vent=$soffit_Length*1.4*0.08153).round(2)% sq ft

Off ridge Vents 3 ea 4' = 414sq in / 144 = %$ridge_Vent = 2.9% sq ft

%($ridge_Vent.to_f + $soffit_Vent.to_f ).round(2)% sq ft vent area provided (%$soffit_Vent.round(2)%+%$ridge_Vent.round(2)%)

 

 

I have a soffit vent calculator built into my pro plan which works well, it works along side specifying high low venting or just soffit venting etc. and works with auto or manual built roofs by building it into the roof defaults.

One of the challenges of building a system like this is that projected overhang does NOT work if you are not supplying a soffit in the case that you are trying to build a vent calc for open eave block venting.

 

[ACADuser]

I'm sure you had to do a lot if work to get that macro to work properly. Mine is adequate for me even if I have to manually enter the overhang amount. I draw a polyline to get the total length even though it will not work in all cases.

 

Thanks for your input.