[LittleBoPeak]

I have question for all you construction wizards out there . . .

I have a 12x20, 2 story shed with a gambrel roof that I would like to convert to a "cabin" for living space. The shed is 2x4 construction, 16" oc, with 24" oc 2x4 roof trusses and ridge vented. It has OSB siding.

How do I insulate and install vapor barrier to insure that I don't set myself up for water damage down the road. I'm sure it is not as simple as just putting in some insulation and sticking up wall board.

Any insights will be most appreciated.

[frankthetank]

Wouldn't you wrap it with Tyvek and then insulate between the studs???

OSB for siding!? What? Is it painted? I would've used plywood and then side it with vinyl (cringes), steel, Al, cedar, etc...

[HeckuvaJob]

Honestly? Ask the very same question over at BreakTime. Having endured my own insulating nightmare this fall, I can attest that there are more factors to consider than you can imagine.

If it isn't sided yet, I agree with frank about the Tyvek. However you have to be careful about how you overlap and tape, especially around windows.

Fiberglass has to be installed with the skill of a surgeon or it will lose most of its value. Blowing cellulose into wall cavities will offer you the advantage of stopping air infiltration.

The best of both worlds? Spray foam like Icynene. This will also server as your vapor barrier. And as you probably already guessed, you'll pay for it.

Please let me know how this turns out. Make sure you mention foundation type, heating source and window type when you post over there.

Edit: Dunewalker mentions an important factor - your climate! Wet-blown cellulose is also an option if you wanted to do the drywall at a later date.

[dunewalker]

What Frank said. OSB is not very weather-proof anyway, even painted. Depends on your climate. If you live in the desert, this is all easier. Wrap the walls in tyvek or tarpaper, for wind protection (tyvek is not a vapor barrier as I understand it) then put another layer of siding, like plywood or planks, whatever. Then install fiberglass R-11/13 (fiberglass bats have a vapor barrier built-in)between the wall studs and put some interior boards on, pine t & g is nice. The roof ought to already have a vapor barrier like tarpaper under the shingles, so just install fiberglass bats & sheath the ceiling same as the walls. If it was mine, I'd do a woodstove installation at the same time. This treatment presumes you have access to cash & supplies. Total cost to upgrade, not including the wodstove, probably will run over $!,000, maybe $2,000. If you're short on cash, just put another good coat of paint on the outside, install fiberglass bats between the 2 x 4s and put some inexpensive wallboard inside.

[kpeavey]

With ease of installation and cost, the Tyvek, pink fiberglass, drywall is right in line with the latest trade secrets. While I've not used it the spray foam is NICE.

I would want to cover the OSB exterior with something more durable. Left exposed, the OSB will begin to swell and decay within 5 years, especially near the ground and close to the eaves. RB&B or T-111 are plywood coverings that will hold up longer. Hardiboard will take the elements, bugs, is fire resistant, and it's as easy to install as OSB. I've used it, I recommend it. Again, you get what you pay for.

Looking through the lens of Peak Oil, the extra you spend on quality and durability can make a considerable difference in the future.

[LittleBoPeak]

Thanks for the responses so far, guys. I know there is a lot to consider.

The shed has been up for several months so it already is finished, at least as much as a storage building usually is. The exterior walls are the OSB sheeting that looks like plywood panels (with the vertical lines etched in it). It has a good paint job on it.

I had thought of the tyvek, but the exterior sheathing is already in place and I'd rather not take it off to wrap it. But if the tyvek is worth the trouble, I'll do it. Unfortunately, money is a concern. So with that in mind, would it make sense to go ahead with the insulation and wallboard in order to get liveable space now and then go back and do the tyvek maybe next year?

The building is in the SE US. Not real wet climate, but high humidity. It is up off the ground about 1 foot on concrete block piers. I do plan to put in a wood stove for heat.

It is the classic dilemma. I want to do it right, but I have a limited budget.

Thanks again for your suggestions!

[kpeavey]

If you had to skip the tyvek, your cabin won't fall down because of it. You can always make up some of the difference with extra caulking, extra paint, and attention to maintenance issues as soon as they present. Extending the eaves by a couple of feet would be handy. Keeps the rain out better and offers shade in the summer.

If what you are calling OSB (Oriented strand Board) has grooves, it is probably not OSB but RB&B or T-111, which is a much better product.

I'd also want that crawlspace buttoned up and insulation under the floor.

Have you given any though to a mirror ball? My sister just loves 'em.

[dunewalker]

I'd also want that crawlspace buttoned up and insulation under the floor.

I disagree with that. Having your building up on blocks promotes air circulation underneath, discouraging dampness & rot. Since you're not in a cold climate, it's not a big issue for heating either. An easy-to-install compromise on the floor insulation issue could be covering your existing floor with 30# roofing felt (heavy tarpaper), followed by another layer of boards for a floor: rough-sawn planks, whatever. It beats crawling around in the mud & spiders underneath trying to staple insulation between the floor joists which will just create mouse/rat habitat anyway.

[HeckuvaJob]

Unfortunately, money is a concern. So with that in mind, would it make sense to go ahead with the insulation and wallboard in order to get liveable space now and then go back and do the tyvek maybe next year?

Here is my advice based on your last post:
1. It was originally constructed as a shed so I'm assuming it's leaky. Therefore you can't choose between blocking air and insulating - you need both.
2. Dense-packed cellulose* is a cheap way to do both.
3. Use a double coat of primer like Zinser 123 on the interior drywall - this should be a sufficient vapor barrier for cold weather if you minimize internal moisture sources.
4. Skip the Tyvek. Since it's been standing for several months, you should be able to judge how weatherproof the exterior is and if any water is getting inside.
5. The upstairs ceiling/attic may be the most important factor in this equation and one that we don't have enough information on.

*Edit: this is a totally different technique than blowing it into the attic. A plastic tube is attached to the end of the nozzle and is fed into the wall cavity through a hole in the drywall. You slowly fill up the stud bay, densely packing in the cellulose and blocking any air leaks.

[Quagmire]

.
A good way to insulate the windows is to cover them from the inside with bubblewrap.... flat side toward the glass. This also provides privacy without losing light.
.

[StormBringer]

I cant stress enough about the OSB siding its a temp siding at best the home i bought has a 1 car detached and it has osb that is falling apart, 6 yrs old.

[uNkNowN ElEmEnt]

I ahve learned recently that the spray foam insultation is a great home for wood bugs.... no joke, it looks like an ant farm.

[LittleBoPeak]

Unfortunately, money is a concern. So with that in mind, would it make sense to go ahead with the insulation and wallboard in order to get liveable space now and then go back and do the tyvek maybe next year?

Here is my advice based on your last post:
1. It was originally constructed as a shed so I'm assuming it's leaky. Therefore you can't choose between blocking air and insulating - you need both.
2. Dense-packed cellulose* is a cheap way to do both.
3. Use a double coat of primer like Zinser 123 on the interior drywall - this should be a sufficient vapor barrier for cold weather if you minimize internal moisture sources.
4. Skip the Tyvek. Since it's been standing for several months, you should be able to judge how weatherproof the exterior is and if any water is getting inside.
5. The upstairs ceiling/attic may be the most important factor in this equation and one that we don't have enough information on.

*Edit: this is a totally different technique than blowing it into the attic. A plastic tube is attached to the end of the nozzle and is fed into the wall cavity through a hole in the drywall. You slowly fill up the stud bay, densely packing in the cellulose and blocking any air leaks.

Heck,

The building has been through several torrential rainstorms and I've seen no evidence of water getting in.

Are you saying that the cellulose is used instead of regular insulation? Is it an equivalent R rating to a comparable thickness of regular insulation?

As far as a vapor barrier, how about putting up plastic sheeting over the insulation, but under the wallboard? Would that be effective or would that create additional problems?

[gnm]

The building has been through several torrential rainstorms and I've seen no evidence of water getting in.

Are you saying that the cellulose is used instead of regular insulation? Is it an equivalent R rating to a comparable thickness of regular insulation?

As far as a vapor barrier, how about putting up plastic sheeting over the insulation, but under the wallboard? Would that be effective or would that create additional problems?

That exterior sheeting you have on is pretty good stuff - just make sure and give it a coat of waterseal (like for decks) and it will last a long time. I wouldn't use plastic sheeting under the insulation. It doesn't breathe and can "sweat" under the insulation due to temp differentials. But I'll bet tyvek would work well in the same place. You could get a roll of the 3 foot size and tack it in vertically perhaps? Just cut in half lengthwise and it should fit perfect - make sure and put the "outside" towards the external ply sheeting.

Another option (slightly more expensive but totally waterproof) is to cut 2 inch EPS foam to fit and press in between the joists. I did this in an attached greenhouse (because of obvious exposure to water) and it has worked well. Then just a little spray foam in the cracks and your done.

-G

[HeckuvaJob]

The building has been through several torrential rainstorms and I've seen no evidence of water getting in.

Great. Think of Tyvek as a Gore-Tex windbreaker and your insulation as a sweater. It certainly wouldn't hurt to install Tyvek, but I think you can safely skip it since it's not leaking and also to save money. Plus the cellulose will take care of air infiltration. Note: I would heed the advice of the above posters who have concerns about the durability of the actual sheathing being exposed to the elements.

Are you saying that the cellulose is used instead of regular insulation? Is it an equivalent R rating to a comparable thickness of regular insulation?

You sound like me before my insulation odyssey (i.e. pink fiberglass = regular insulation). I'd actually purchased $600 of fiberglass but after doing more research, I decided to switch to cellulose (luckily my dad used it). Cellulose will give you R=3.4 per inch. Fiberglass R=3.2, but only when installed by the book. A typical installation (with gaps and compression) gives an R=1.8 When you think about it, fiberglass installed inside of a drafty stud bay is really just an air filter.

Cellulose is “green.” It’s made of 80% post-consumer recycled newsprint. The fiber is chemically treated with non-toxic borate compounds (20% by weight) to resist fire, insects and mold. The common standard by which insulation is measured, R-value, is the level of resistance to heat flow. R-value measures conductive resistance – the ability of a material to impede the flow of heat along the continuous chain of matter that makes up a solid material. Most of a home’s heat is typically lost through conduction. Cellulose is not unusual in this regard. Like many insulation materials, it provides an R-value of approximately R-3.5 per inch of thickness. But, air leakage through cracks, voids, and gaps is important, responsible for approximately one-third of an average home’s heat loss. Cellulose is a superb air-blocker. Heat and comfort are also lost through convection; when drafty currents of air within the house, wall cavities or attics, move heat to other locations. This is technically different from air leakage where the heated air mass is actually expelled from the home. Tightly packed cellulose provides a thermally efficient, cost effective, and comfortable solution.

Blowing fiber into enclosed wall and cathedral framing cavities is different. Here a smaller 1- or 2-inch diameter fill tube is attached to the end of the larger hose. The fill tube is inserted into enclosed cavities through a series of strategically placed holes. The general idea is to drill a series of 2-inch holes horizontally across the structural surface so that the holes are centered in each framing cavity. One or more holes per framing bay are required depending on the length of the framing cavity and the applicator’s fill technique.

As far as a vapor barrier, how about putting up plastic sheeting over the insulation, but under the wallboard? Would that be effective or would that create additional problems?

I'd be very leery of putting any plastic inside of a wall cavity for fear of mold. My job was a remodel so I didn't have a way of adding a vapor barrier (the Kraft paper of Kraft faced fiberglass batts) but I think the Zinser 123 primer is good substitute (I waterproofed a sheet of paper with a single coat as a test).

Cellulose Insulation – A Smart Choice
a great book see page 79
How to Retrofit Cellulose Insulation -not really applicable to your situation, but a good overview

[LittleBoPeak]

There is a lot of info to digest here. So much for my "simple" insulating job! Thanks to all for the info. And thanks, Heck, for the links . . . Interesting reading. The sprayed cellulose sounds like the way to go.

Like I always say, you learn something new everyday, whether you want to or not!

[uNkNowN ElEmEnt]

Actually after all this talk I am thinking more about a kind of polyliner (its like bubble wrap) and reflects heat back in and acts as a vapour barrier. its supposed to give an R value of 9.5 for 2.5" thickness. for thinner walls that might be the way to go.

[LittleBoPeak]

Actually after all this talk I am thinking more about a kind of polyliner (its like bubble wrap) and reflects heat back in and acts as a vapour barrier. its supposed to give an R value of 9.5 for 2.5" thickness. for thinner walls that might be the way to go.

Got a link for more info?

[JRP3]

Try googling "reflective bubble insulation".