[Greenbuilding] Fwd: air barrier recommendations

Tue Jul 12 18:44:30 CDT 2022

Hi, Reuben—

I only saw John’s first message. I have heard of the idea of foam panels but have not encountered any example here in Portland. Usually they are used under slab-on-grade construction. 

We had a big discussion about insulating under our slab. Me: the climate will shift from heating to cooling dominant. Heating guy: Maybe but that’s far off, you need insulation under the hydronic pipes. Compromise: R-3 foam sheeting. During the heat dome the house stayed comfortable, but does cost more to heat in winter. I’m mentioning this history as I am not sure why John suggests foam under a crawl space?

Best, Mike
Sent from my iPhone

> On Jul 12, 2022, at 3:54 PM, Reuben Deumling <9watts at gmail.com> wrote:
> 
> 
> 
> 
>> On Tue, Jul 12, 2022 at 7:31 AM Mike O'Brien <obrien at hevanet.com> wrote:
>> Hi, Reuben—
>> 
>> Thanks for that clarification. I assume there will be a moisture barrier on the ground? Will that be a poly sheet? You OK with plastics? If so what about stapling poly to your joists to create an air barrier? Kraft paper might work too.
> 
> I am familiar with plastic sheeting laid on the ground of a crawl space, and even the version that involves attaching cleats to the perimeter (foundation). I'm not clear on whether that is considered preferable to what I had imagined, which was to bring that barrier up (in this case) about a foot and attaching it to the underside of the joists. 
> Poly was where I started, but John has been suggesting that wouldn't be as good as rigid foam panels. 
> Have you seen his messages? They are marked up with SPAM, but I've been getting them even so. They went to the whole group.
>> 
>> Best, Mike
>> Sent from my iPhone
>> 
>>>> On Jul 11, 2022, at 10:14 PM, Reuben Deumling <9watts at gmail.com> wrote:
>>>> 
>>> 
>>> Full dimension kiln dried Douglas-fir 2x6 joists with 5/4 decking nailed on top. At this point that is the anticipated extent of the floor. 
>>> Because the crawl space is so low I was planning to build the floor in two sections upside down, and staple whatever barrier to the underside of the floor before flipping each section over and attaching it to the sill plates.There may be a better way to do this?
>>> 
>>>> On Mon, Jul 11, 2022 at 9:41 PM Mike O'Brien <obrien at hevanet.com> wrote:
>>>> Hi, Reuben—
>>>> 
>>>> Say more about the floor? What’s the material? Will have a finish floor?
>>>> 
>>>> Best, Mike
>>>> Sent from my iPhone
>>>> 
>>>>>> On Jul 11, 2022, at 3:58 PM, Reuben Deumling <9watts at gmail.com> wrote:
>>>>>> 
>>>>> 
>>>>> Portland Oregon, dry hot summers; high humidity in the winter. 
>>>>> 
>>>>> I should have mentioned that I am skipping the plywood altogether. I am putting up rough sawn board-and-batten siding over the studs and blocking. My thought was to put that air barrier between those. 
>>>>> 
>>>>>> On Mon, Jul 11, 2022 at 3:35 PM John Straube <jfstraube at gmail.com> wrote:
>>>>>> Hey there Reuben.  A description of your climate would be helpful before I weigh in..
>>>>>> In most cases taping up the plywood or osb sheathing would often be a great solution. 
>>>>>> 
>>>>>>> On Mon., Jul. 11, 2022, 18:15 Reuben Deumling, <9watts at gmail.com> wrote:
>>>>>>> I hope there are still a few of you smart people out there. This list used to be so fun!
>>>>>>> 
>>>>>>> I'm a little rusty on this stuff. So your thoughts are much appreciated. 
>>>>>>> 
>>>>>>> I am building a 250 sf shop in my back yard. I am insulating the floor right away (R19 FG batts) and the walls and 12/12 metal roof plane sometime in the future. My hope is to affix a barrier of some sort (6 mil plastic?) to the underside of the joists (ca. 12" unvented crawl space beneath), and wrap the walls and roof plane with some sort of air barrier, but am not sure what a good product choice would be for 
>>>>>>> - under the floor
>>>>>>> - the walls
>>>>>>> - the roof
>>>>>>> 
>>>>>>> Thanks for all suggestions. 
>>>>>>> 
>>>>>>> Reuben
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