I am currently working with a homeowner on a home they recently purchased that is having sever moisture problems in their attic. The home, in south Louisiana, is 6500 square foot, 2 story home.

The original owner had radiant barrier installed on the underside of the roof which also covered all ridge and soffit vents making the attic unventilated. The AC handler as well as ducts are installed in this attic.

In addition, the original owner also installed a vapor barrier and insulation above the ceiling which now basically made the attic very oven like. They also have placed dehumidifiers in attic to help reduce the moisture which now takes moisture out but blows hot air.

Before I was called in, the new homeowner had cut away some of the radiant barrier from the ridge vents to allow some air flow. We then had rest of the barrier and insulation removed from the ridge and soffit vents to allow some breathing. Also have run blower door and duct blaster and sealed much of the air leakage.

I am thinking that we remove the vapor barrier from the ceiling as it is causing lots of moisture to form on the attic side of it.

My question is do you think removal of the vapor barrier is the way to go then to determine if we need some outside ventilation help?

Also, what are thoughts on dehumidifer and fact that it blows out Hot Air?

What are your opinions of Radiant Barrier sales guy insistance that the RB has sufficient R value to be installed and considered adequate Insulation to make the attic unventilated and part of conditioned space and that homeowner should not have insulated/ vapor barriered the celing?


Thanks for any and all input.

Also what are thoughts on other ventialation methods here?

Mechanical, turbine??

I suggest you should apply proper ventilation and after that. SPF Roofing will be best to avoid from these problems.

SPF Roofing

Greetings,

Having been a RB contractor for over 30 yrs, maybe I can help. I'm located in the St. Louis, Mo area.

In some areas were you do not have a sealed floor sys you will have alot of moisture passing up thru the house into the attic, not withstanding the ambient moisture. That can over whelm any sys when you do not have adequate attic venting. CK core-a-vent.com. for info and quality prods. Many RV sys are not as effective as the manufacture would have you believe.
Make sure the ratio of soffit vent to RV is adequate.

Normally you do not have moisture problems with RB. I had only one in 30 yrs and it turned out to be my fault, and was correctable.

I would guess that not only was the vent sys sabotaged the RB material was NON PERFORATED. RB are almost perfect vapor barriers and perforated materials should be used to allow any excess moisture to except. The is true for single and multilayer ssys. I never had moisture problems in a residential structure including those with minimal venting, such as, gable vents or cap vents.

Having an AC in the attic can cause problems in high humidity ares because the AC is condensing moisture and if not enough circulation or improper drainage of condensate it can cause problems.

As far as "R" value, RB barriers do not have "R" values. A two layer material is more than adequate for your area. If fact it will out perform any other material.

I would also suggest that you contact fifoil.co. They are located in Florida and may have even sold the insul contractor the material you removed. They will be able to answer any questions you have recommend a suitable installation.

You did not indicate if there was any insulation in the ceiling area. This is where the RB should have been installed. Fi Foil has a two layer material that can be installed from the top.

One thing else. I'll bet they insulated the rafters to reduce the load on the AC components and duct work. That's ok but there is a way to do that and not cause problems. Hopefully they used foil wrapped ducts.

I visited your site rbisys1 fifoil.com. You are providing really good services for homemakers. But SPF Roofing is also a good choice.

IMO, an attic should be well ventilated to either the interior or the exterior. Never both or neither. RB has no R value.

In most of Louisiana the moisture drives are never from the interior, even in winter. Putting the vapor barrier on the conditioned space side was a mistake. Putting an AIR barrier on that side improves efficiency and keeping it vapor-open allows the AC to dry the attic, even through the insulation. But if the moisture drives are too high, it may not keep up.

The relative leakiness of the AC ducts and the pressure balance of the system can be huge drivers of infiltration- if the condition or design of the system is depressurizing the attic it will suck far more outdoor moisture into the attic via the attic ventilation than can be removed by vapor permeation through the ceiling to the drier conditioned space below. In these situations attic ventilation is more the problem than the solution (although massively ventilating the attic is still better than the double-vapor-barrier condition it currently has.) If you take an unvented attic approach using spray foam on the roof deck and remove the interior-side vapor barrier it can reduce the impact of system defects to near-zero by bringing the system entirely within the pressure boundary of the building.

If the ducts aren't sealed and insulated to at least R8 with an air-impermeable material (as in not-fiberglass) they can be below the dew point of the outdoor air in a vented attic. But if the attic is sealed to the outdoors yet vapor-open to the interior, the dew point of the attic air will track that of the conditioned space- it can't condense on the outside of the duct unless it's also condensing on the inside as well.

A minimal 1" flash-foam of closed cell on the roof deck and any gables/soffits with tightness verified/rectified with a blower door fans will solve this problem, provided the interior vapor barrier is removed. The closed cell foam also provides a non-wicking moisture tolerant condensing surface for those 21 hours/year where the roof deck might be below the dew point of the conditioned space air. If you re-install the existing radiant barrier after the foam, have it stop 4" below the ridge and 4" above the soffits to allow internal convection-drying of the cavity. The relative economic value of that r.b. will be somewhat lower with R6+ or more at the roof deck- it depends on the roofing type & orientation, the insulation values on the ducts & airhandler, and the total R values of the roof deck + attic floor. It may or may not be worth the labor costs of keeping it. See:

http://www.ornl.gov/sci/ees/etsd/btric/RadiantBarrier/RBFactSheet2010.pdf

Greetings,

QUOTE>I visited your site rbisys1 fifoil.com. You are providing really good services for homemakers. But SPF Roofing is also a good choice.

This is not my website. I have no website. This is the Fi Foil mfgrs. site. Fi foil has been on the market for at least 60 yrs that I know of.

SPF is a good choice compared to FG or Cel. Foam is about 20 % eff against radiant energy, RB 97 %. There is no legitimate comparison unless you want to pay the premium for foam plus its draw backs. That being said I can see where SPF would be the only option.

In this case it's the air-sealing, more than the R value of the SPF that we're after (although the ~R6 would be sufficient to prevent condensation even at the 99th percentile heating season design conditions with a code-min R30 on the attic floor.) It's easier to air-seal reliably with closed cell than open cell, even though you'd get more R/$ out of open cell.

The expression "Foam is about 20% eff against radiant energy..." is devoid of meaning, since the foam is in direct CONDUCTIVE contact with the roof deck, and effectively ZERO percent of the heat transfer between the roof and foam being radiated. Closed cell polyurethane foam is opaque to infra-red radiation (so is cellulose, but low-density fiberglass is somewhat IR-translucent), so the heat transfer from the roof deck side to the interior side of the foam is WAY more than 80% conduction.

The emissivity of the interior face of the foam is much higher than foil, true, but the temperature is also lower resulting in a lower convective drives, etc. Radiant barrier is more useful for blocking heat transfer between objects with dramatically different temperatures, separated by more than an inch of space, such as a 140F roof deck above 50F uninsulated ducts, and if the ducts ARE uninsulated, re-commissioning the existing r.b. after foam-sealing may be cost effective, provided it comes off cleanly. There might be better payback in just insulating the ducts than r.b. across the whole attic, either with perforated foil-faced fiberglass or closed-cell foam. Sealing the ducts is at least as important than insulating them, even with a sealed semi-conditioned attic.

Greetings,

QUOTE>IMO, an attic should be well ventilated to either the interior or the exterior. Never both or neither. RB has no R value

I mentioned earlier that RB have no "R" rating although some bubble/foil manfr's have had there prods test so as to be listed in the national code. BIG MISTAKE.

By the way, to my knowledge FG is not listed in the code as a thermal insulator because they would have to submit their product to insitu testing and that would reveal the REAL "R" factor. something they do not want you to know. When pressed for a reason they give some convoluted, bs reason.

The energy industry ( all inclusive ) including the Gov wants you hooked on "R" factors. It's easy for them to control your choices with "R" factors. If you only knew how really manipulative the sys really is, you would rise up in revolt. Energy policies are used to obtain massive unearned monies from the consumer. Does everyone know the word fraud?

Greetings,

QUOTE>I visited your site rbisys1 fifoil.com. You are providing really good services for homemakers. But SPF Roofing is also a good choice.

Thank you for your comments.

This is not my website. I have no website. This is the Fi Foil mfgrs. site. Fi foil has been on the market for at least 60 yrs that I know of.

SPF is a good choice compared to FG or Cel. Foam is about 20 % eff against radiant energy, RB 97 %. There is no legitimate comparison unless you want to pay the premium for foam plus its draw backs. That being said I can see where SPF would be the only option.

Sorry about the repeat my computer out foxed me.

Greetings,

QUOTE>conditions with a code-min R30 on the attic floor.)

Code does not mean it's efficient. 3-4" of any bulk insulation is about maximum for savings vs investment. Any suggestion that any amount above that is going to save a significant a mount of energy is deception.

QUOTE>The emissivity of the interior face of the foam is much higher than foil, true, but the temperature is also lower resulting in a lower convective drives, etc.

What conductive drives? Internal of foam?, attic? Please clarify.

QUOTE> Radiant barrier is more useful for blocking heat transfer between objects with dramatically different temperatures, separated by more than an inch of space, such as a 140F roof deck above 50F uninsulated ducts.

Now you used the subject of ducts, but that statement is true of roof deck to drywall. Although the RB would be above the drywall. I just wrap a RB around the duct with spacers to maintain air space. How ever it's best if foil wrapped duct is installed. An aside. I've run across several cases where the home owner specified foil wrapped ducts and the contractor installed "plain" FG insulated ducts AND the contractor refused to change them.

In retrofit cases where the duct was covered with FG I just went over the FG over ducts with RB. Luckily I never had a problem with this.

Since headw didn't specify insulation type or density or give any R-values, what's the fascination with fiberglass (which nobody recommended)?? Just about everybody and their brother has kicked the stuffing out of that low-density fiberglass straw man over the last 30 years, and the deficiencies thereof aren't exactly a hot news flash, eh? The moisture problems in this attic are in no way impacted by use of fiber insulation of any type. They may have been somewhat aggravated by a low-perm r.b. layer, but that's the least of the problem.

For thinking about moisture traps condensation & heat gain issues in attics in any gulf state climate, this is a good place to start:

http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1496-05.pdf

Bottom line, attic ventilation is far more useful for purging moisture in climates much colder than Louisiana, and is counterproductive for both energy use and moisture accumulation within the structural wood when the AC distribution & mechanicals are in the attic.

But as for that flimsy fiberglass scarecrow, it's all a big conspiracy between the manufacturers & government, yup, I'm convinced... ;-)

In-situ testing of multifoils to compare to standard guarded-box test methods in the UK pretty much demonstrated that multifoils perform at best to only ~1/4-1/3 of their marketing claims relative to comparisons with mineral fiber products (as in "fraud"). But I'm sure the fact the slimy-limey corrupt UK gummint, iso manufacturers, and mineral wool manufacturers all ended up sponsoring similar tests of multi-foil products and the fact that they ended up with similar test results only proves that it was a conspiracy, eh? :-)

http://www.foam-insulation.co.uk/customer_resources/BRE-multi-foil-insulation-measured-u-values.pdf

http://www.communities.gov.uk/documents/planningandbuilding/pdf/multifoil.pdf

Everyone from Texas A & M to Oak Ridge & Lawrence-Livermore Labs and the Florida Solar Energy Center are in cahoots too, and have all had their thumbs on the scale when testing ( in-situ and laboratory) efficacy of reflective films and fiber insulation in building assemblies too, despite strong correlation between excellent improved theoretical models & empirical results too- it's an INTERNATIONAL conspiracy, I tell ya, and even the PassiveHouse Institute is in on the game! All o' that funny math & stuff they throw atcha is just a ruse to throw you off!

Nobody in the high-performance building biz gives a ratzazz about the code-min R values that corrupt gummint demands, only the whole envelope performance. Funny thing, R-values used in the building-energy-use models actually work, and real building U-values and predicted energy use based on modeling of R-values & masses of the structural & insulating materials do too. And designing a building that performs well generally requires higher-R/lower-U than a code-min building does- go figure!?! Better models even factor in non-linearities of foam & fiber insulation at different temperature averages & delta-Ts, but for most of the lower-48 climate averages, simple 1-number derating/uprating for the application is sufficient to get "close enough" to real performance. R-value is not a perfect metric of anything, nor is it presumed to be. But it's a relevant part of the design (more relevant than reflectivity or emissivity values in most building components.)

Posted By headw on 25 Aug 2011 06:14 PM
I am currently working with a homeowner on a home they recently purchased that is having sever moisture problems in their attic. The home, in south Louisiana, is 6500 square foot, 2 story home.

The original owner had radiant barrier installed on the underside of the roof which also covered all ridge and soffit vents making the attic unventilated. The AC handler as well as ducts are installed in this attic.

In addition, the original owner also installed a vapor barrier and insulation above the ceiling which now basically made the attic very oven like. They also have placed dehumidifiers in attic to help reduce the moisture which now takes moisture out but blows hot air.

Before I was called in, the new homeowner had cut away some of the radiant barrier from the ridge vents to allow some air flow. We then had rest of the barrier and insulation removed from the ridge and soffit vents to allow some breathing. Also have run blower door and duct blaster and sealed much of the air leakage.

I am thinking that we remove the vapor barrier from the ceiling as it is causing lots of moisture to form on the attic side of it.

My question is do you think removal of the vapor barrier is the way to go then to determine if we need some outside ventilation help?

Also, what are thoughts on dehumidifer and fact that it blows out Hot Air?

What are your opinions of Radiant Barrier sales guy insistance that the RB has sufficient R value to be installed and considered adequate Insulation to make the attic unventilated and part of conditioned space and that homeowner should not have insulated/ vapor barriered the celing?


Thanks for any and all input.

I occurs to me that some questions remain unanswered.


Easiest first: Dehumidifiers MUST blow out hot air in order to work. They can only remove moisture by lowering the temp of the inlet coil to below the dew point of the incoming air.  To do that they raise the temp of the exit-air coil by pumping heat from the inlet coil to the exit coil with a refrigerant compressor.  It's essentially an air conditioner with both coils on the same side, but the exit air stream will always be above the temp of the surrounding air stream since it's putting the heat-of-vaporization for the condensed water into the exit air stream.

But I also didn't note any recommendations to check for (not code-compliant but too often done) kitchen & bathroom vents exhuasting into the attic.  Even if exhausting through the roof, if there there are any kitchen or bath vents passing throught he attic they need to be checked for leakage and sealed.

Posted By headw on 25 Aug 2011 06:14 PM
I am currently working with a homeowner on a home they recently purchased that is having sever moisture problems in their attic. The home, in south Louisiana, is 6500 square foot, 2 story home.

The original owner had radiant barrier installed on the underside of the roof which also covered all ridge and soffit vents making the attic unventilated. The AC handler as well as ducts are installed in this attic.

In addition, the original owner also installed a vapor barrier and insulation above the ceiling which now basically made the attic very oven like. They also have placed dehumidifiers in attic to help reduce the moisture which now takes moisture out but blows hot air.

Before I was called in, the new homeowner had cut away some of the radiant barrier from the ridge vents to allow some air flow. We then had rest of the barrier and insulation removed from the ridge and soffit vents to allow some breathing. Also have run blower door and duct blaster and sealed much of the air leakage.

I am thinking that we remove the vapor barrier from the ceiling as it is causing lots of moisture to form on the attic side of it.

My question is do you think removal of the vapor barrier is the way to go then to determine if we need some outside ventilation help?

Also, what are thoughts on dehumidifer and fact that it blows out Hot Air?

What are your opinions of Radiant Barrier sales guy insistance that the RB has sufficient R value to be installed and considered adequate Insulation to make the attic unventilated and part of conditioned space and that homeowner should not have insulated/ vapor barriered the celing?


Thanks for any and all input.

You cannot have ridge vents and soffit vents in an unvented attic space, just covering up with reflective barrier is not good enough. I believe you have hot humid air inthe space with conditioned air and thus condensation is occuring

Greetings,

QUOTE>You cannot have ridge vents and soffit vents in an unvented attic space, just covering up with reflective barrier is not good enough. I believe you have hot humid air inthe space with conditioned air and thus condensation is occurring

I didn't quite get what you meant until I reread the original info.

If you have a RB installed on the bottom of the rafters and a RV/soffit vent is installed the air will be channeled between the RB and sheathing. Actually even with out a RB the soffit air flows under the sheathing. If you're in an attic on a hot day and put your hand by the sheathing you can feel the air flow. By the way you can have TOO MUCH soffit opening which will result in a hurricane in the attic.

I still contend that if a 2-3 layer of RB had been installed in the cord spaces and the ducts RB protected that there would not have been any problems. I have seen this type of installation many times with no problems. But then, I'm up in the St Louis area. The excess moisture in that area might/must have mitigating circumstances.

I haven't seen a VB installed in the ceiling for ages. They cause nothing but problems as the condensate puddles on the VB. I have seen VB pulled down from weight of condensate in framed houses in winter time. I can't say if same happens in summer. Also, the commercial FG batts you see in commercial buildings use to have a lighter plastic envelope. I have seen those pulled out of the ceiling even though the plastic was suppose to be a VB. The industry went to a much heavier plastic to prevent this.

ALL INSULATION MATERIALS are subject to some type of condensation effect. It occurs either within the material and/or at the contact point of the material and adjacent material (wood, metal, ect)

I have seen excessive moisture with sprayed and cut foam at the sheathing and rafter contact points and if the moisture exceeds 15% it will support rot. You can't stop moisture migration unless you take unusual measures and even then it's probamatic. Moisture will ALWAYS look for a way out and to condensate at a dew point. I use the term ( like a magnet, which dana1 doesn't like the term) but is picturesque as the moisture is drawn to this point. Vapor is like the energy we talk about, it moves from a high moisture area to a low moisture area.

RB under some atmospheric conditions have some moisture at the contact area of a dissimilar material, but it is minimal
( no damage ) and DOES NOT affect the performance.

DANA1 questioned way we talk about FG as it is not very effective. I would say because it is still the most widely used material and the people looking for info here do not know that. GENERALLY i would say that are "R" counting and want what APPEARS to be the best investment for their dollar. They need to be educated even if it means repeating ourselves many, many times.

According to the independent (?) data put out by the various bulk insulation mgfr's they are only up to about 15 % more eff than FG. Considering how inefficient FG is that isn't much of an endorsement. Don't ask for sources it's been too many years since I read those reports. I would guess they are somewhere on line.

Keep in mind all these materials are test under conditions THAT DO NOT represent the installed condition. If they were you wouldn't buy them.

And speaking of tests, just because it says independent lab, someone had to pay for those tests and it is their prerogative to INTERPRET the data any way they see fit. This is why I try to only use data from a mechanical engineering handbook.

Sorry about the wordiness. One idea/subject leads to another.

rbisys1; what I am saying is a conditioned atic is NOT to be vented AT ALL!!! The air conditioned air is coming in contact with a warm radiant barrier and causing consensation. A conditioned attic space is to be completely sealed up with insulation to the underside of roof deck and truss heals - no open vents at all , no insulation on ceiling. Whom ever did the house, did it all wrong

Greetings,

Got it. BUT. You don't want bulk insulation against the sheathing, it will rot out.
This now becomes a similar to, vaulted ceiling sys.

Two layer RB between rafters. This will allow space between RB and sheathing for RV/soffitt sys.
One layer RB to facing rafter surface. 7/8" stl furring strips across rafters, moisture resistant dry wall.
Gable ends must be done also. Go to: fifoil.com

And, nothing in the attic floor especially VB.

Posted By rbisys1 on 20 Sep 2011 11:54 PM
Greetings,

Got it. BUT. You don't want bulk insulation against the sheathing, it will rot out.
This now becomes a similar to, vaulted ceiling sys.

Two layer RB between rafters. This will allow space between RB and sheathing for RV/soffitt sys.
One layer RB to facing rafter surface. 7/8" stl furring strips across rafters, moisture resistant dry wall.
Gable ends must be done also. Go to: fifoil.com

And, nothing in the attic floor especially VB.

Yes you do want insulation against the roof deck, the roof deck will not rot out, drywall is not required in any of the conditioned space. Tour problems stem from letting in hot humid air into your conditioned space. The same condensation would occur in your house if you left the windows open in your house with the HVAC running, eventually something will have water droplets on it. Quit trying to ventilate an unvented conditioned space. Close everything off! The Fi Foil radiant barrier is not your insulation