# How to vent a balcony with finished living space below?



## bnymbill (May 4, 2020)

I have a 10'x12' balcony with half-walls on three sides and a full wall with a sliding glass door to living space on the 4th side.  Below the balcony is finished living space. 

My concern is how to appropriately vent the balcony since it is technically a roof and subject to the same conditions.  The framing is 2x10's at 16" OC running front to back with 1/4" slope per 1'.  There is a vent channel at the top of the 2x10s which is open at the low end to vent through the 2x4 half wall at the front.  However, I cannot add vents at the high end, where the sliding door is, because the framing is solid.    

The current vent opening in the front 2x4 wall is 12"x6" and is centered on the wall.  I am considering adding a 4" round vent on both ends of the front wall to at least create more air movement.  Am I doing more harm than good by over venting on the low end without being able to add anything to the high end?  

I have included the URLs for two pictures - one a drawing of the current situation and the second a picture of the house to give the drawing some perspective.


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## classicT (May 4, 2020)

Go with full depth insulation and no vent. IBC 1203.3


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## cda (May 4, 2020)

bnymbill said:


> I have a 10'x12' balcony with half-walls on three sides and a full wall with a sliding glass door to living space on the 4th side.  Below the balcony is finished living space.
> 
> My concern is how to appropriately vent the balcony since it is technically a roof and subject to the same conditions.  The framing is 2x10's at 16" OC running front to back with 1/4" slope per 1'.  There is a vent channel at the top of the 2x10s which is open at the low end to vent through the 2x4 half wall at the front.  However, I cannot add vents at the high end, where the sliding door is, because the framing is solid.
> 
> ...




You can direct post pictures and stuff, If you are a forum supporting Sawhorse..

Other method, make the picture a link and post the link


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## bnymbill (May 4, 2020)

I decided a video was best to scroll through two pictures of the house, specifically the balcony, as well as a sketchup drawing.  

I did read IBC1203.3 and I know that the insulation does have a vapor barrier on the ceiling side, so that's already non-compliant.  

It seems like there was an attempt to meet 1203.2 by having cross ventilation in each joist bay but air can only enter/exit through the low side.  Since I have no way to add vents to the high side, would I be doing more harm than good by increasing the vents on the low side?


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## ADAguy (May 4, 2020)

Duh? You want to vent the floor of the balcony eh?

Not typically done, no? Does need waterproofing and flashing though.


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## bnymbill (May 4, 2020)

It's got a vent at the low side, up through the wall for great weather protection.  I do not plan to vent the balcony floor, such as by adding two-way vents on the floor, at the high side for weather and tripping hazard reasons.

My question is, given that the only vent is 6"x12" at the top center of the front wall, am I helping at all by adding 4" round vents at each end of the front wall?  Will this help circulate air by at least creating a cross vent through the air gap in the front wall?


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## classicT (May 4, 2020)

bnymbill said:


> It's got a vent at the low side, up through the wall for great weather protection.  I do not plan to vent the balcony floor, such as by adding two-way vents on the floor, at the high side for weather and tripping hazard reasons.
> 
> My question is, given that the only vent is 6"x12" at the top center of the front wall, am I helping at all by adding 4" round vents at each end of the front wall?  Will this help circulate air by at least creating a cross vent through the air gap in the front wall?


Go unvented per 1203.3

*1202.3 Unvented attic and unvented enclosed rafter assemblies*
Unvented attics and unvented enclosed roof framing assemblies created by ceilings applied directly to the underside of the roof framing members/rafters and the structural roof sheathing at the top of the roof framing members shall be permitted where all of the following conditions are met:

The unvented attic space is completely within the building thermal envelope.
No interior Class I vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly.
Where wood shingles or shakes are used, not less than a 1/4-inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing.
In Climate Zones 5, 6, 7 and 8, any air-impermeable insulation shall be a Class II vapor retarder or shall have a Class II vapor retarder coating or covering in direct contact with the underside of the insulation.
Insulation shall be located in accordance with the following
5.1. Item 5.1.1, 5.1.2, 5.1.3 or 5.1.4 shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.

5.1.1. Where only air-impermeable insulation is provided, it shall be applied in direct contact with the underside of the structural roof sheathing.
5.1.2. Where air-permeable insulation is provided inside the building thermal envelope, it shall be installed in accordance with Item 5.1.1. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing in accordance with the _R_-values in Table 1202.3 for condensation control.
5.1.3. Where both air-impermeable and air-permeable insulation are provided, the air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing in accordance with Item 5.1.1 and shall be in accordance with the R-values in Table 1202.3 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
5.1.4. Alternatively, sufficient rigid board or sheet insulation shall be installed directly above the structural roof sheathing to maintain the monthly average temperature of the underside of the structural roof sheathing above 45°F (7°C). For calculation purposes, an interior air temperature of 68°F (20°C) is assumed and the exterior air temperature is assumed to be the monthly average outside air temperature of the three coldest months.​5.2. Where preformed insulation board is used as the air-impermeable insulation layer, it shall be sealed at the perimeter of each individual sheet interior surface to form a continuous layer.​

*Exceptions:*​
Section 1202.3 does not apply to special use structures or enclosures such as swimming pool enclosures, data processing centers, hospitals or art galleries.
Section 1202.3 does not apply to enclosures in Climate Zones 5 through 8 that are humidified beyond 35 percent during the three coldest months.


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## e hilton (May 4, 2020)

That’s not a balcony, its roof top space.  I don’t see any drainage scuppers ... unless they are hidden by the brickwork.


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## Keystone (May 4, 2020)

Are


bnymbill said:


> I have a 10'x12' balcony with half-walls on three sides and a full wall with a sliding glass door to living space on the 4th side.  Below the balcony is finished living space.
> 
> My concern is how to appropriately vent the balcony since it is technically a roof and subject to the same conditions.  The framing is 2x10's at 16" OC running front to back with 1/4" slope per 1'.  There is a vent channel at the top of the 2x10s which is open at the low end to vent through the 2x4 half wall at the front.  However, I cannot add vents at the high end, where the sliding door is, because the framing is solid.
> 
> ...


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## Keystone (May 4, 2020)

Are you certain what your describing as a vent is actually a rooftop drain? The front picture and video while limited in view does not appear to show the rooftop drain and this would be required in such an area.


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## bnymbill (May 5, 2020)

There are 3 drains flush with the balcony/roof surface as well as a raised drain (emergency drain) in the even the other 3 become blocked.

The air vent is at the top/center of the front wall, 6" x 12" screened opening with a cover for weather protection.  It is directly behind the couch.  

It's already built, so I can't comply with 1202.3 because the insulation has a vapor barrier on the ceiling side.  Short of removing the ceiling and vapor barrier, then replacing drywall, it can't comply.

My question is, will adding 4" vents at the left and right edges of the front wall be of any significant help?  Given that the only vent is at the top/center of the front wall, there is no other form of circulation.  Would adding vents at each end of the front wall increase cross ventilation or just being spitting into the wind?


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## Keystone (May 5, 2020)

In order to know if adding vents will be a benefit, try and seek the municipal permit paperwork from when this was constructed. See how it is constructed to determine beneficial or not. 

If no paperwork exists, doesn’t seem likely it would cause harm.


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