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Winter is coming and building inspector won't let me insulate my unvented roof!?

Winter is coming and building inspector won't let me insulate my unvented roof!?


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Old 10-30-15, 08:23 PM
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Winter is coming and building inspector won't let me insulate my unvented roof!?

Hi everyone, I'm putting 2 bedrooms and a bathroom in the undeveloped attic space of my small 900 sq foot home so we aren't so crowded. The rafters are just 2x4 and headspace is very limited, so I need to just fill the space between the rafters flush with spray foam and cover with drywall. But the building inspector is saying 9.19.1.1 of the Code won't allow me to do this. Is anyone familiar with this? Does anyone know a way I can get around this part of the code? People in Ontario and BC have, but not I'm not sure how to here in Alberta. The only option I've been told might work by one spray foam company is to hire a "building envelope professional engineer" to write the inspector a letter to say it's ok to have an unvented roof. We just put a new metal roof on (metal over 1x4 strapping over impermeable membrane over 3/8" plywood decking over existing plank board sheathing) with no vents. We were assuming we could do the insulation as planned. We've also already done the framing as shown below and suspended an new floor in the space from the large beams running the length of the house. We we're stuck being unable to insulate our house and winter is coming!
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We planned to spray foam from the peak to the eaves:
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Here are the relevant parts of the building code:

9.19.1.1. Required Venting 1) Except where it can be shown to be unnecessary, where insulation is installed between a ceiling and the underside of the roof sheathing, a space shall be provided between the insulation and the sheathing, and vents shall be installed to permit the transfer of moisture from the space to the exterior. (See Appendix A.)

A-9.19.1.1.(1) Venting of Attic or Roof Spaces. Controlling the flow of moisture by air leakage and vapour diffusion into attic or roof spaces is necessary to limit moisture-induced deterioration. Given that imperfections normally exist in the vapour barriers and air barrier systems, recent research indicates that venting of attic or roof spaces is generally still required. The exception provided in Article 9.19.1.1. recognizes that some specialized ceiling-roof assemblies, such as those used in some factory-built buildings, have, over time, demonstrated that their construction is sufficiently tight to prevent excessive moisture accumulation. In these cases, ventilation would not be required.
 
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Old 10-30-15, 08:42 PM
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Weren't the plans submitted to the building dept. for approval before the construction started? Does the code require soffit vents, ridge vents or both? . In a way, the inspector is correct since moisture can get trapped without vents. You could install the dry wall & do the spay foam after the job is approved.
 
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Old 10-30-15, 09:05 PM
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Here is an article by Dr Lstiburek, who's credentials should satisfy any building code official and he has experience with Canadian codes, which I suspect are much the same across Canada since most use the same energy performance software.
Understanding Attic Ventilation | Building Science Corp

Read that article and then review the many other articles referenced from it.

Bud
 
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Old 11-04-15, 07:08 PM
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Thanks for the help. I am going to get an engineer to approve the insulation against the decking.
 
 

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