tyvek vs felt/paper in uninsulated bldg
i read fhb and breaktime everymonth, but its my first post: thanks in advance.
i know this topic must be argued dozens of times around here, but here i go again.
we are building a freestanding garage with a pool changing room addition.
so there is the 28’x28′ uninsulated and unheated garage shell and a 20’x6′ fiberglass batt insulated bathroom/changingroomaddition. the addition is unheated and the plumbing will be drained in the fall/winter.
we are in st louis, mo where humidity and temperature swings quite drastically.
we are assuming tyvek is appropriate for the insulated addition.
is tyvek also the answer for the uninsulated garage with taped sheetrock walls and clgs?
to make it be more specific we will have a ‘rainscreen’ detail of hardi-siding over 1x spacers to try to delay the first ‘repaint’ of the siding, etc.
i called dupont and of course they wouldnt give me a reason not to use tyvek in the uninsulated space, do you guys have any concerns about that situation?
and if we choose to use tyvek in the insulated space and paper or felt for the uninsulated garage, am i correct in assuming there isnt an argument for using wrap between the garage and the insulated space? [at the connection of insulated addition to uninsulated garage]
thanks in advance guys.
: jr
Replies
You need to look at exactly what each one does.
Felt is a weather barrier. That is that blocks the flow of direct water.
Tyvek is also a weather barrier, but it is also a air barrier, but it does allow moisture (vapor) to pass through.
Heated or unheated either could be used.
I'd say to use felt on the uninsulated portion of the building to save a few bucks since you don't need an air barrier there anyway, but here is another way to think about... It sounds like you are already buying a roll of Tyvek for the heated/insulated portion of the building... Won't the roll be enough to do the whole building? What are you gonna do with a leftover 1/2 roll of tyvek? The stuff is a bit expensive to waste...
>> the addition is unheated ...
Is it also not air conditioned? If you're not heating or cooling it, why are you insulating it?
A big argument for Tyvek is that (properly installed) it will greatly reduce air infiltration into the building. This will significantly increase the comfort level in an unheated building.
If ya use tarpaper , you can buy more beer.
I'd use felt for both. It's cheaper, has very long track record, and assuming you're sheathing the buildings, the plywood or osb will provide an adequate air barrier.
Andy Engel
Senior editor, Fine Woodworking magazine
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
It's amazing how much air can leak through supposedly "tight" sheathing. Even brownboard sheathing that's stapled every 4 inches.
What is "brownboard"? I'm guessing it is the fiberboard stuff that is made of sugarcane - or at least it is around here - and around here it is black...
Matt
I've heard it called "beaverboard" locally, but that term is apparently used for some other product elsewhere. Anyway it's the felt-like sheathing board -- presumably made with wood fibers, but only lightly compressed, so that it breaks and crumbles about as readily as drywall. Generally a dark brown/black in color. Pretty much replaced by foamboard now, I suppose, for structures that will be sided to the studs, or with OSB, for structures that will be sided with vinyl.
Cover it with tarpaper, and you'll keep a lot more air out. Use a decent insulation like foam or cellulose, and the housewrap's contribution to preventing air infiltration becomes moot. On repair jobs, I've seen plastic housewrap from the mid 80s that was like tissue paper, both in strength and water repellency. I'm sticking with #30 felt.
AndyAndy Engel
Senior editor, Fine Woodworking magazine
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
I've never seen felt in 9-foot rolls, and I suspect that tape doesn't stick to it too well. The advantage of a housewrap like Tyvek is that it lets you achieve a truely seamless "shell", without leaky (to air) joints anywhere. The difference is significant, at least on our retrofit of a mid-70s home. (And if rainwater is getting to our Tyvek I'll eat my caulking gun.)