Spray foamed attic with visible window

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Is it an acceptable practice to have a visible window in a spray foamed attic?

2024-07-22-10:34:28:359
2024-07-22-10:34:28:3593024×4032 2.51 MB

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why do You think it would be wrong ?

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Unsealed area if the window leaks air. Spray foamed attics are not supposed to have any ventilation.

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Spray foam attics are within the building thermal envelope. A window in that space will have the same consequence as a window in your bedroom provided it is installed correctly.

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Received, thank you

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I would disagree with that, Dr. Joe has been talking about for years…

https://buildingscience.com/documents/building-science-insights-newsletters/bsi-116-interior-spray-foam

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There may be some confusion. Per Dave’s link, they recommend that unvented conditioned attics have a moisture removal system utilizing a balanced intake/outtake mechanical exhaust. The terms exhaust and ventilation are not interchangeable in this design.

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That article is old. The IRC recognized the issues with spray foam insulation in2018 (?).
Florida Building Code Residential R806.5 finally recognized it in 2020.

R806.5 Unvented attic and unvented enclosed rafter assemblies. There are several options of venting outlined/

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

  1. 1.The unvented attic space is completely within the building thermal envelope.
  2. 2.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.
  3. 3.Where wood shingles or shakes are used, a minimum 1/4-inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing.
  4. 4.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.
  5. 5.Insulation shall comply with Item 5.3 and Item 5.1. As an alternative, where air-permeable insulation is located on top of the attic floor or on top of the attic ceiling, insulation shall comply with Item 5.3 and Item 5.2.
  6. 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.
    1. 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.
    2. 5.1.2.Where air-permeable insulation is provided inside the building thermal envelope, it shall be installed in accordance with Section 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 R806.5 for condensation control.
    3. 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 R806.5 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
    4. 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.
  7. 5.2.In Climate Zones 1, 2 and 3, air-permeable insulation installed in unvented attics on the top of the attic floor or on top of the ceiling shall meet the following requirements:
    1. 5.2.1.An approved vapor diffusion port shall be installed not more than 12 inches (305 mm) from the highest point of the roof, measured vertically from the highest point of the roof to the lower edge of the port.
    2. 5.2.2.The port area shall be greater than or equal to 1:600 of the ceiling area. Where there are multiple ports in the attic, the sum of the port areas shall be greater than or equal to the area requirement.
    3. 5.2.3.The vapor-permeable membrane in the vapor diffusion port shall have a vapor permeance rating of greater than or equal to 20 perms when tested in accordance with Procedure A of ASTM E96.
    4. 5.2.4.The vapor diffusion port shall serve as an air barrier between the attic and the exterior of the building.
    5. 5.2.5.The vapor diffusion port shall protect the attic against the entrance of rain and snow.
  8. 5.3.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.
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What is a vapor diffusion port? Ridge vent?

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2024-07-22_152006

https://buildingscience.com/documents/guides-and-manuals/gm-2101-guide-building-conditioned-unvented-attics-and-unconditioned

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Thanks for that, JJ. I am seeking the recommended ventilation for an unvented space that David alluded to. I may be splitting hairs here, but I do not consider a vapor diffusion port to be ventilation. In fact, the port is covered with foam. What do you think?

image

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Yes basically…
https://buildingscience.com/documents/digests/bsd-012-moisture-control-for-new-residential-buildings
Dr. Joe explains it here…
https://buildingscience.com/documents/insights/bsi-088-venting-vapor

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In a ‘nutshell’, I have seen more arguments/disagreements with that Joseph Lstiburek guy than most anyone else! For some unknown reason, Florida inspectors seem to love him.
Now for my opinion about the OP’s situation… remember that I am in the Upper Midwest (Minnesota) where our climate varies/swings from one extreme to another within a short period of time. Our summers often reach high 90’s to low 100’s with 90+% humidity… and our winters drop to minus 20 to minus 30’s and windchills often drop to minus 40f to minus 50f.
With that being said, when our (modern) attics are encapsulated in foam, they are completely sealed and Conditioned via Supply/Returns from the HVAC. Rarely if ever is there exterior venting in place.
“Century” homes (multi-story) are built with minimal box venting (IF ANY) and no gable or soffit venting at all. Most of these are passive conditioned, such as with staircases in closets, not open staircases, and usually no direct venting from a HVAC unit.

FYI… Since most of us are aware that different regions have different methods of building systems, and since the OP didn’t specify where he is located… here is his website: https://offdutypro.net/

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I am in Austin Texas

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In my opinion, the attic should now be viewed just like any other conditioned room in the home. And that means, it should be conditioned. A supply and return vent would be great. Or passive venting to the room(s) below would suffice I suppose. I have also seen bath fans installed to discharge stale air in the sealed space to the outdoors. You just need to make sure there is a make-up air source. If there is an air exchanger in the home, that opens up other possibilities as well.

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When the attic is insulated, the question to ask is, “where is the thermal barrier and where is the air barrier?” The air and thermal barrier define the “building envelope”. If the air and thermal barrier are defined by the closed cell foam in the attic, then the attic becomes conditioned space within the building envelope. If there is no heat source in the attic, it’s the same as a bedroom with the door closed and no heat source present in the bedroom. That bedroom with the closed door, like the insulated attic, is part of the building envelope. BTW, both can have windows in them, and both should have the same quality windows.

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A vapor diffusion port — also known as a vapor diffusion vent, a diffusion vent, or a vapor vent — is located at the ridge of a gable roof or at the hips of a hipped roof.

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Gotta say that I am a big fan.

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도움이 되었으면 좋겠습니다.

I hope I can be of help.

Building Code Considerations

  1. Fire Safety:
  • IRC R316.5.3 - Attics: According to the International Residential Code (IRC), spray foam insulation in attics must meet specific fire safety requirements. If the attic is used for storage or contains HVAC equipment, the foam must be covered with a thermal barrier, such as 1/2-inch gypsum board or an equivalent material, unless the foam itself is specially formulated to be fire-resistant.
  1. Ventilation:
  • If the attic is unvented and fully encapsulated with spray foam insulation, proper ventilation is typically not required. However, if there are windows, they should be sealed properly to maintain the integrity of the insulation and prevent air leakage.
  • IRC R806.5 - Unvented Attic Assemblies: This section outlines the requirements for unvented attic assemblies, ensuring that the insulation is applied directly to the underside of the roof deck and that the assembly is designed to control moisture.
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