Unfaced or Faced Batts?
- Thread starter Bull
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Torque1st
MEMBER EMERITUS
With a heated structure you need a vapor barrier towards the heated space.
I know that much. So, the vapor barrier can either be the kraft-paper on the faced batts, or the poly spread over unfaced batts, right? Which is "better"?
Torque1st
MEMBER EMERITUS
From your description I could not tell where you were placing the poly.
Which is cheaper and easier? The kraft faced bats will install easier.
Which is cheaper and easier? The kraft faced bats will install easier.
boiler7904
Well-known member
Poly will give a more continuous vapor barrier. Faced batts are easier to install and probably the same cost or slightly cheaper than an unfaced batt and poly vapor barrier combination.
Either is an industry accepted building practice and will give satisfactory results if installed properly.
Probably the most important thing before insulating is to make sure that all of the small voids, cracks, etc. are filled with caulk or a foam like Great Stuff to stop air infiltration. Air moving through a building is what causes the inefficiencies with trying to insulate and heat the structure.
Either is an industry accepted building practice and will give satisfactory results if installed properly.
Probably the most important thing before insulating is to make sure that all of the small voids, cracks, etc. are filled with caulk or a foam like Great Stuff to stop air infiltration. Air moving through a building is what causes the inefficiencies with trying to insulate and heat the structure.
Torque1st
MEMBER EMERITUS
Remember you do need air "infiltration" under the roofing above the ceiling insulation.
Thanks for the replies.
The barn was wrapped with Tyvek/Vortec before the shiplap went up, so hopefully that will take care of most of the cracks and gaps that will cause infiltration. I also do plan on using caulk or foam around windows and doors, too.
I guess I'm leaning towards batts for ease of installation if the poly is not significantly better at doing the job.
The barn was wrapped with Tyvek/Vortec before the shiplap went up, so hopefully that will take care of most of the cracks and gaps that will cause infiltration. I also do plan on using caulk or foam around windows and doors, too.
I guess I'm leaning towards batts for ease of installation if the poly is not significantly better at doing the job.
Torque1st
MEMBER EMERITUS
Watch the foam around windows and doors. I know of a few people that have tried to fill the space with foam and ended up deforming the windows and door frames enough that they would not operate. Foam -expands- and puts a surprising amount of pressure on the frames. It is a tough job to rip out all that foam afterwards. A good flexible caulk is probably a better solution then fill the voids with fiberglass.
Ezzie
Well-known member
I don't think you can even buy kraft faced batts in the "Great White North" anymore - I know I haven't seen them in my area for about 20 years now. Problem is, it is very difficult to get an air tight seal where they staple up. The only way to get a good seal is to put a 6 mil poly and caulk/tape all of the seams and ends. The idea is to make it vitually air tight, and as a result, not allow any moisture to move from the heated space to the cold space.
I just redid the attic insulation in my house - it was done with kraft faced R20 batts about 35 years ago when it was built. The batts were a mess - full of dirt and dust, mice nests, etc. This is clear evidence of air movement from the living space and up through the tiny gaps. I stripped the whole works out, vacuumed the top of the ceiling between the rafters and had 1-2" of urethane foam sprayed in to give a good air seal (especially watch the light boxes, vent pipes, stacks, etc. to get a tight seal). Then I put another 18" of blown celllulose on top - taking the whole business up to about R50-60.
Bottom line - HUGE difference. This winter the house is toasty, no drafts and tight. I'm now going to have to install an air-to-air heat exchanger to keep the winter time moisture levels in check.
Regarding the foam situation around doors and windows, Home Depot, Lowes, etc. sell a low expanding foam specifically for this purpose. Don't ask how I figured that one out!!
I just redid the attic insulation in my house - it was done with kraft faced R20 batts about 35 years ago when it was built. The batts were a mess - full of dirt and dust, mice nests, etc. This is clear evidence of air movement from the living space and up through the tiny gaps. I stripped the whole works out, vacuumed the top of the ceiling between the rafters and had 1-2" of urethane foam sprayed in to give a good air seal (especially watch the light boxes, vent pipes, stacks, etc. to get a tight seal). Then I put another 18" of blown celllulose on top - taking the whole business up to about R50-60.
Bottom line - HUGE difference. This winter the house is toasty, no drafts and tight. I'm now going to have to install an air-to-air heat exchanger to keep the winter time moisture levels in check.
Regarding the foam situation around doors and windows, Home Depot, Lowes, etc. sell a low expanding foam specifically for this purpose. Don't ask how I figured that one out!!
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They do sell the kraft faced batts here, in any of the home stores. I have used them in the walls of my house in the rooms that I have remodeled so far.
I do use the blue-can Great Stuff expanding foam, specifically designed for doors and windows. It is much softer when it dries, and seems to yield to the surfaces that it contacts, rather than pushing them out. Don't get it wet, though, or it will disintegrate.
Funny how many opinions there are about this. Some say the kraft batts are good. Others say the poly is fine, but don't bother to tape the seams. Still others say you need to meticulously tape every seam and caulk every joint. Hard to decide what is "right" or at least "right enough" for the job.
I do use the blue-can Great Stuff expanding foam, specifically designed for doors and windows. It is much softer when it dries, and seems to yield to the surfaces that it contacts, rather than pushing them out. Don't get it wet, though, or it will disintegrate.
Funny how many opinions there are about this. Some say the kraft batts are good. Others say the poly is fine, but don't bother to tape the seams. Still others say you need to meticulously tape every seam and caulk every joint. Hard to decide what is "right" or at least "right enough" for the job.
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Torque1st
MEMBER EMERITUS
Please understand it all depends on your entire construction "system". No individual component is "best". With kraft faced insulation you must use a standard sheetrock cover or equivalent over the studs/joists to hold the seam seals together. You must decide what you need to do the job and the parts must work together.
Junkman
Well-known member
The 6 mil clear poly will be a lot better than the paper faced bats. One difference is that you still need an air space between the insulation and the finished surface. I did this in the cathedral ceiling in my home by using the unfaced bats, and poly. Then I put a layer of blue foam over the poly, and strapped the ceiling with 1" x 2" furring strips. Sheet rocked over that. That is the best insulated ceiling in the house. Should have done it in all the ceilings. There is also an air space that is required above the insulation, so make sure that you have that also. The cost of insulation is a lot less than the long term of heating costs, so give up a little space for more insulation. In the end, you will be a lot happier. If you can find someone to do the spray foam insulation, that is the very best. It is a lot more expensive, but in the end, you will have a product that is 300% superior to fiberglass. There is someone on the site from NH that does this. I visited his site once, and was quite impressed with it. Possibly he will chime in and make suggestions. Junk...
rburke65
Well-known member
why do you need an air space between the insulation and the finished ceiling?
Junkman
Well-known member
The dead air space is part of what insulates. Think of why you have storm windows, or double pane glass. The dead air space is an insulator of cold from warm.
Hmm, even more to think about, then. Do you need that air space in a wall, too, Junk?
At the moment, I am favoring the idea of using vertical barn boards for my interior wall surface. I think it will look good, be easy to install (I hate drywall) and be easy to remove in the future for inner-wall access.
At the moment, I am favoring the idea of using vertical barn boards for my interior wall surface. I think it will look good, be easy to install (I hate drywall) and be easy to remove in the future for inner-wall access.
rburke65
Well-known member
I thought you were saying that it was required or mandatory...."you still need an air space"......You don't "need" it....may be nice to have, but don't "need" it.
Junkman
Well-known member
If you are going to be using barn boards for the inside wall surface, then I would even more strongly recommend the spray insulation. Barn boards are not very tight fitting, and you want a tight seal between the insulation and the wall surface to stop infiltration of air. I know that your barn is wrapped with Tyvek, but even that isn't 100%. The more insulation, and the better the quality of the insulation and its installation, the less it will cost to heat the building.
It isn't required or mandatory as a matter of the building code, but as a good building practice, it should be done. If you look at the instructions on the faced bats of insulation, you are supposed to staple the paper to the sides of the framing, not the face of the framing. When you properly install the faced insulation, you are creating this air space.
boiler7904
Well-known member
Tyvek and other building wraps do a good job of minimizing air infiltration in wide open wall areas where there are no penetrations and the material is kept in good condition without tears or holes. The two big problems are that a lot of builders (even the most quality driven guys) let Tyvek sit and flap in the wind for days or weeks before installing siding and they also don't do all of the Tyvek recommended detailing at penetrations like windows, doors, electrical boxes, etc. Those areas are where you will get small gaps and air infiltration which cuts the effectiveness of any insulation / vapor barrier system. Since fiberglass insulation is basically spun glass fiber and air, adding any amount of pressure (from a gap or hole) moves cold air from outside the building into the insulation and eventually into your conditioned space.
A couple of tubes of caulk and some foam will make the building that much more comfortable and energy efficient when you go to heat it later on.
A couple of tubes of caulk and some foam will make the building that much more comfortable and energy efficient when you go to heat it later on.
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BTT with a new question.
Home Depot had a sale on insulation. It was cheaper for me to buy the R-19 kraft faced vs the same amount of unfaced insulation, so I did. Now, I also bought some 6 mil poly. Can I use BOTH kraft paper batts AND the poly for a vapor barrier, or is that going to cause some moisture pocket in the wall, between the two materials, that will cause me grief?
Home Depot had a sale on insulation. It was cheaper for me to buy the R-19 kraft faced vs the same amount of unfaced insulation, so I did. Now, I also bought some 6 mil poly. Can I use BOTH kraft paper batts AND the poly for a vapor barrier, or is that going to cause some moisture pocket in the wall, between the two materials, that will cause me grief?
BooUrns!
Well-known member
There is a vast difference in the building systems used betwen the US and Canada as we live in a much more extreme climate zone. It has become the national building code standard to use minimum 6mil poly vb with R-20 insulation in the walls and a air barrier system on the exterior subsurface.
If you look at a climatic map of North america you will notice that most of our country is in a different zone the the US (with the exception of certain parts of southern ontario and BC).
Properly installed poly VB (lapped/taped/acoustically sealed) is far superior to kraft-faced batts as a vapour barrier system. The question becomes will the OP need this system in his climate zone? I would presume that it would do no harm.
Keep in mind, these systems are only effective when all leaks are sealed. I'm a little curious how he would expect to achieve a perfect seal around a barn door?
I don't have any barn doors, just insulated garage doors.
So, can I use the poly that I purchased in conjunction with the kraft faced batts?
And, is there any special tape I need to use on the poly? I purchased heavy duct tape.
So, can I use the poly that I purchased in conjunction with the kraft faced batts?
And, is there any special tape I need to use on the poly? I purchased heavy duct tape.
Ezzie
Well-known member
Should be just fine. There is a special tape for taping the poly seams - it is very thin, red and is really sticky stuff. Some people refer to it as "Tuck" tape which is a brand name - available at most home improvement stores at about $10 a roll.
Here's a link to the stuff - it is amazing!!
http://www.can-save.ca/index.php?option=com_content&task=view&id=195&Itemid=93
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BooUrns!
Well-known member
Throw out that duct tape. The only thing duct tape is good for is for hog-tieing your neighours yappy little poodle the next time you catch it crapping on your lawn...
Use the red 'Tuck" tape mentioned by Ezzie. It's meant for sealing airbarriers/vapour barriers. Those systems are worthless unless they are lapped and taped thouroughly. Also ensure they are adquately stapled into place with the right type of staples (T-50 I believe). Finally, seal the poly along the bottom plate with acoustic sealant. It's nasty stuff but is the best way to ensure a good tight seal against the framing.
Garage doors will leak... especially when they're open...
Use the red 'Tuck" tape mentioned by Ezzie. It's meant for sealing airbarriers/vapour barriers. Those systems are worthless unless they are lapped and taped thouroughly. Also ensure they are adquately stapled into place with the right type of staples (T-50 I believe). Finally, seal the poly along the bottom plate with acoustic sealant. It's nasty stuff but is the best way to ensure a good tight seal against the framing.
Garage doors will leak... especially when they're open...
Kevin54
MEMBER EMERITUS
Check this on the batts http://www.insulate.org/ckpts.html
http://www.energy.ca.gov/efficiency/qualityhomes/insulation.html
http://www.energy.ca.gov/efficiency/qualityhomes/insulation.html
Kevin, those two links were great, thanks.
I was at Home Depot today buying some stuff. I asked a guy in the building materials dept. for that Tuck tape. He had no clue about it, and could only show me Tyvek tape. I bought some, to tape my Tyvek seams from the inside. Can I use Tyvek tape for the 6 mil poly? The only thing is, it's like $10 for a 165ft roll. I checked HD online, Lowes online, and Amazon and do not see that Tuck Tape for sale.
I was at Home Depot today buying some stuff. I asked a guy in the building materials dept. for that Tuck tape. He had no clue about it, and could only show me Tyvek tape. I bought some, to tape my Tyvek seams from the inside. Can I use Tyvek tape for the 6 mil poly? The only thing is, it's like $10 for a 165ft roll. I checked HD online, Lowes online, and Amazon and do not see that Tuck Tape for sale.
ripsnortMN
Well-known member
I heard that using poly over craft faced insulation will put moisture between the poly and craft paper. And make the paper rot out over time from being wet.
boiler7904
Well-known member
You are correct. Wet fiberglass loses its insulating value as it is saturated. Also creates a place for mold to grow. Warm, moist environment with a paper food source is a guaranteed place to grow mold.
Use poly sheeting behind the drywall OR faced batts. Not both.
That is EXACTLY what I needed to know, thanks to the both of you 
I guess I have some poly to return. It's cheaper to buy the kraft faced stuff, so that is what I'll be doing, and just taping my Tyvek seams as good as I can from the inside.
I guess I have some poly to return. It's cheaper to buy the kraft faced stuff, so that is what I'll be doing, and just taping my Tyvek seams as good as I can from the inside.
eieio
Member
Well, Bull, walls and ceilings are treated differently.
First the walls: if you have 2x6 studs, then R-19 is perfect; so stuff it in. But a double vapor barrier (kraft & poly) is no good. 6 mil poly is the BEST anyway; so, using it is good. In the construction industry we often install the kraft faced, then put multiple knife cuts into the kraft paper to allow "breathing" (thus defeating its vapor barrier quality) followed by 6mil poly overall. Makes a great, tight wall.
Level ceiling (MA climate): R-38 insul, NO vapor barrier, ventilated soffit and attic. Pay close attention at the eaves; install draft chutes in every cavity to allow air flow from the soffit to the attic unobstructed. Blown cellulose is the best value in this case.
Cathedral (angle) ceiling (MA climate): fill the rafter cavity as with as much as space permits up to R-38, NO vapor barrier, but maintain a 1" air space beneath the roof sheathing and be sure the air space affords air flow from the soffit to the ridge unobstructed. This air space by design is to inhibit condensation formation on the bottom of the roof sheathing...very important. Of course, you need soffit vents and ridge vent for this program to work.
You'll be able to heat this building w/ a candle!
eieio
First the walls: if you have 2x6 studs, then R-19 is perfect; so stuff it in. But a double vapor barrier (kraft & poly) is no good. 6 mil poly is the BEST anyway; so, using it is good. In the construction industry we often install the kraft faced, then put multiple knife cuts into the kraft paper to allow "breathing" (thus defeating its vapor barrier quality) followed by 6mil poly overall. Makes a great, tight wall.
Level ceiling (MA climate): R-38 insul, NO vapor barrier, ventilated soffit and attic. Pay close attention at the eaves; install draft chutes in every cavity to allow air flow from the soffit to the attic unobstructed. Blown cellulose is the best value in this case.
Cathedral (angle) ceiling (MA climate): fill the rafter cavity as with as much as space permits up to R-38, NO vapor barrier, but maintain a 1" air space beneath the roof sheathing and be sure the air space affords air flow from the soffit to the ridge unobstructed. This air space by design is to inhibit condensation formation on the bottom of the roof sheathing...very important. Of course, you need soffit vents and ridge vent for this program to work.
You'll be able to heat this building w/ a candle!
eieio