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Ice Dams & Ice Melting

Post in 'DIY and General non-hearth advice' started by Don2222, Feb 16, 2011.

  1. Hogwildz

    Hogwildz Minister of Fire

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    Insulating directly up to or on the bottom of sheathing, especially planks or plywood, is going to cause the wood to rot &/or dry rot.
    Venting is needed to allow hot air escape in the hotter months, lessening the load on the living space below. It also keeps moisture from building up.
    Overhangs serve several purposes. Depending on size, it helps shield the house from the sun in summer months hence helping keep cooler and helping keep cooling costs lower.
    Also in the even of melt. freeze on the roof, if the gutters do back up, or even an ice damn at the edge, it allows any run back that drips in at the gutter to run into the soffit area and drip out, and not back into the house or wall.
    See many, many homes with no soffit of overhang damn up and the water runs directly into the wall space. Better to drip out of the soffit, then run into the wall or house, causing mold, rot and serious issues.
    After 13 years of roofing I have see many of these issues, time & times again. Replaced enough plywood decking due to no breathing. Not something I would recommend, but hey in 5 or ten years you can find out for yourself.
    Have fun.

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  2. Don2222

    Don2222 Minister of Fire

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    Hello Hogwildz

    I have 2 neighbors that own split entry homes like mine on the street behind me that put Fiberglass insulation between the rafters in the inside of the roof. They both had rotted plywood in the roof from doing this. I actually saw one of them. After replacing the roof and some rotted sheets of plywood on the roof he had most of the insulation torn out of the roof and it was left on the attic floor. When I was up in the attic I removed 2 pieces of Fiberglass still in the roof Rafters and guess what? The plywood was getting dark moldy and ready to rot! So then I installed those pink rafter vents and Reflectix foil.

    So Hogwildz you are definately right when Fiberglass is in the Rafters. Is Urathane Foam any different? Mike Holmes on Holmes on Homes stated on more than one of his shows that Roofs need ventilation and the underside should be a cold zone.

    Just happen to have pic of it. Ew!

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  3. SolarAndWood

    SolarAndWood Minister of Fire

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    The foam guys and the architects that listen to them around here would have you think that. My new roof is 12/12, full rain/ice, big overhangs, generous ventilation and no stinkin gutters. Guess what, no ice dams.
  4. doubledip

    doubledip Member

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    I'll agree with you 100%. Once the roof and sheathing become the vapor barrier the roof is destine to fail. The hot roof concept is a different animal but not without consequence if a leak develops.

    The pro vents are used to hold off blown in insulation not to block soffit vents, that’s it. No need to take them all the way to the ridge vent as seen in one of the photos above.

    Its no wonder why there are so many issues with ice damming and or premature roof failure.
  5. Reggie Dunlap

    Reggie Dunlap Feeling the Heat

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    If a "hot roof" is done correctly the only way the sheathing will be exposed to moisture is if the roof leaks. Urethane foam acts as a vapor barrier, forming a shell or a skin when it cures. As long as the foam has no voids or cracks this eliminates any chance of condensation forming on the sheathing.

    I recently did some renovation work on a house I built in 2001. The roof had been foamed right to the underside of the sheathing and when a few sheets of plywood had to come off I scraped the foam off to take a look. It took some work to get the foam off but the plywood looked like new.

    That's not to say all foam projects are immune to problems. I've seen issues caused by improper mixing of the chemicals and from foam being sprayed in temps that were too cold. Both ended with cracks within 48 hours. Every job I do with foam I like to wait a minimum of a week before I cover it with sheetrock or wood.

    I've used a few different foam contractors and the company I've been using for the last few years is very educated about the products they use. We wouldn't be insulating expensive houses the way we do if there was any chance of moisture issues down the road.
  6. woodgeek

    woodgeek Minister of Fire

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    a stupid question for the OP--did you airseal the floor of your attic space? If you did, how is all the heat escaping to the attic? If you didn't could you do that AND have a vented attic?
  7. Don2222

    Don2222 Minister of Fire

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    Hello
    Here is a roof I worked on last year. The picture was taken after a light dusting of snow. The right side has more melting and moisture because more heat from the home is escaping thru the roof.
    The left side has pro vents and reflectix foil from the soffits all the way up to the ridge vent.
    The right side has no pro vents or foil.

    Which would you rather have?

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  8. woodgeek

    woodgeek Minister of Fire

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    Don,

    I think the issue here is pretty simple--is the airsealing envelope inside the insulation (ideal for cold climate) or outside it (rot hazard)? I get that you are venting the sheathing (good), but it seems you have two leaky envelopes in your attic (the floor and the ceiling), and two insulation barriers (floor batts and rafter reflectix) rather than one envelope with good airsealing and insulation. If you are losing a lot of conditioned air into your attic (and out the gable vents), wouldn't airsealing the floor with 10 cans of spray foam or 10 tubes of caulking be more cost effective than the vents, reflectix, gable vent covers etc?

    If you are not satisfied with the performance of floor airsealing alone, then you can up the insulation over the floor. Now, with two envelopes, if you up the insulation on the floor you might cause a problem with condensation of humid conditioned air on the inside of the reflectix, etc.

    I suspect that you have thought about your attic sitch a great deal, but with no slight intended, you seem to have taken a 'non-standard' approach. I really don't know enough about your project to have a real comment, but I am concerned whenever I see a non-standard approach...

    Speaking as a DIY myself, the fatal error that many DIYs get drawn into is to make an effective fix to an obvious problem, which turns out to only be a 'band-aid' that creates a problem somewhere else, which mandates its own 'band-aid', and before you know it, you have done a whole bunch of 'non-standard' mods, rather than a more standard 'systemic' improvement. Of course, the band-aids might collectively work great (e.g. in energy savings), and not lead to problems like rot (if you are lucky/vigilant/or band-aided that effectively). But even if successful the non-standard is a problem--the 'standard' approaches are just that because they are the most cost effective way to achieve a desired goal, as well as the ones that are most reliably not going to cause problems down the road (e.g. when a different part of the house 'system' is modified during a retrofit, or the next homeowner installs a really big humidifier).

    Can a DIY innovate a real advance in building science? Sure, I guess. But for every one of those DIY non-standard innovations that is superior to the conventional approach, there must be scores of DIY serial band-aid messes that will need to be ripped out wholesale when the next homeowner hires a professional to fix a problem (rot/odor) or achieve a higher energy performance (e.g. air-seal the attic floor carefully and blow in a couple feet of insulation).
  9. Don2222

    Don2222 Minister of Fire

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    Hello woodgeek

    Air sealing is the 1st item I took care of. I used Great Stuff insulating foam in all the electrical wire holes coming into the attic. The professionals are limited to what they can do for a days work that will pay.
    Around here the only choice seems to have those quote "Professionals" blow old shreaded newspaper treated with poison (borax) so the bugs will not eat it as high as possible because when it settles the performance and R value will decrease when they are long gone! This does not seem like the best option to me. What happens when the poison wars off? Some people have a bad reaction to it. How do I know if that is someone living here until it is too late? Also the performace of Fiberglass increases as the temperature falls where the opposite is true for the paper blown in stuff.

    So the performance of fiberglass and the fact that it is fire retardent and bug proof and the least expensive option is a very good solution. To me the only better solution is Roxul comfort bats but that is double the price! >> http://www.roxul.com/residential/save energy with comfortbatt

    To do even better, I added 2x2s to the 2x4s in the Attic floor to make 2x6s and keep the electrical wires out of the way. Then rolling down Reflectix for R4 and a very good moisture barrier, I then rolled down R19 and crisscrossed it with R30 for a total of R54!!

    Now you must know heat travels by different methods. Sure air sealing prevents heat loss from convection but heat also travels thru conduction between the molecules of one media to another by exciting the electrons that orbit the nucleus so they travel faster and at higher orbits. So even the sheet rock in the ceiling and wood rafters in the attic will conduct heat right thru the roof!

    Therefore after all the air sealing and insulation, blocking of the gable vents still could be easily felt by making the house more comfortable especially on windy cold winter days and nights!!

    Since the last day in Sept of last year I still have 1/2 tank of oil and I like waiving to the oil trucks as they pass by. My are still neighbors complain that they are spending $500 a month on oil because these homes are old! Sure I use a wood pellet stove I installed myself, but the location where it is installed can and does heat the whole house! Again, The pros could not install it there. Too much work to make money!!

    So I will continue to make improvements that the professionals cannot do because there is not enough money in it for them and save more energy!

    So what did you do for insulation and how does it work?

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  10. Hogwildz

    Hogwildz Minister of Fire

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    Yeap, running fiberglass directly up to the bottom of the decking can rot the wood.
    As far as the urethane. If it is closed cell and lets no air in, it might not rot the decking in most cases. But the other possible issue is, without the ventilation space underneath, the shingles prematurely age from the excess heat due to lack of ventilation. Think of it as a heat shield wall behind a stove. They call for a 1" air space, this is a cooling buffer zone between the original wall & the stove. Same for the a roof. Accept your air space is under the decking between the decking & the attic itself. Now take that away and although the foam may help insulate any heat from entering the attic space, or even possibly keep the attic cooler, which again may or may not happen, it does not let the heat from the roof on & from the roof transfer and cool from the ventilation below, as now there is none. Roofing gets hot, real hot, in the summer at times you can't even touch it. So when it is 90 or 100 outside air temp, guaranteed the roof is 150+. Anything that helps transfer or move that heat extends the life of your roof.
    I have seen plywood that was so dry rotted, no mold, no staining, just plain dry rotted from excess heat. You could practically break it up with your hands. Not that this happens more than not. Sometimes you have to consider the outside as well as the inside, as is what I always did with roofing. Of course, I don't know everything. If I did, I would be rich on some island somewhere, not really giving a crap about any of this LOL.
    As with anything, everyone has their own experiences. So nothing is gospel. I only know what I have seen when I roofed for a living. In my mind, I want lots of ventilation, and no water infiltration. That makes for a longest life of a roof. The trick is to keep heat from the house from escaping into the attic. Which in many cases is impossible to do 100%. Then the ventilation takes over from there.
    The baffles you sued are a great thing. They let the air circulate and also promote flow as the natural flow will come in the bottom at the soffit and flow up & out the top.
    There has been conflicting reviews on reflective surfaces in the attic. I can't lean one way or another, as I don't have any experience with foils & such in an attic. Some say the foil keeps heat in and from escaping. Others say it reflects the UV's from the roof keeping that heat out. Others say it cooks the shingles from below die to the heat reflective nature. I just don't know there.
    I thought a couples years ago someone here posted a thread on an article on that. But I just can't remember when & where.[/quote]
  11. Hogwildz

    Hogwildz Minister of Fire

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    Amen ;-)

    Gutters are the cause of ice daming. Unfortunately, many homes need the water from the roof collected and diverted away.
    It can get pretty messy underneath the eaves without gutters. Splashing, dirt on the walls, water infiltration of the basement etc. At minimal you would need hardy, tough plant life or a good stone based under where the water would fall.
  12. seige101

    seige101 Minister of Fire

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    [/quote]

    This is partial myth, studies have shown shingle and sheathing temp only different a few degrees vented roof vs hot roof or unvented roof. Shingle manufacturers are still standing by their warranty if a hot roof is installed.

    "However, preliminary research
    data from the University of Illinois
    show that roof ventilation has
    remarkably little effect on shingle
    temperature. The Illinois research
    is supported by experiments at the
    Florida Solar Energy Center
    (FSEC) which showed only a few
    degrees difference in shingle temperature
    between vented and
    unvented roofs." 1

    1 http://www.jlconline.com/cgi-local/...e.storefront/4d5ae0cf0aae86e927170a32100a0694
  13. seige101

    seige101 Minister of Fire

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  14. SolarAndWood

    SolarAndWood Minister of Fire

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    40 yards of stone and a few hundred feet of 4" pipe did the trick. Got rid of the other evil in this game, the sump pumps. Its all gravity now. No more ice dams, no more wet basement.
  15. Hogwildz

    Hogwildz Minister of Fire

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    [/quote]
    As in any debate, a link and research, articles & such can be found for both sides of any debate.
    I hardly know everything. But I know what I dealt with first hand in 13 years a s roofer. I know what my own eyes saw, and my own hands tore up.
    I'll tell you what. Make a box with a pitched roof on it. Shingle it in to manufacturer's specs. Add no ventilation in the soffit area or roof ridge. Sit in there on a 90 degree day for even 10 -15 minutes.
    Build another box same as the first, accept add soffit & roof ridge vent. Go ahead and measure the difference in inside temps and the roof temp of the underside of the deck. I guarantee there is at least a 20degree difference if not more.
    I have been inside enough attics that I know this from experiencing it first hand. Ask any insulation mechanic and I bet they will confirm.
    If you bothered to read the entire article from which you just searched , found and posted in an attempt to substantiate your side of the debate, you would notice the article's author's last sentence.....

    Quote:"In my opinion, roof ventilation is cheap insurance against expensive callback problems. Why gamble?" End quote Which in my opinion, now negates all the previous BS he spewed forth. Can't be on both sides of the fence at the same time.

    Partial myth? Which is it, a myth or not? Partial??? LMMFAO
    You can post all the articles you want to try and solidify your side of the debate. When you have the actual experience under your belt, come back and let us know.
    When you actually have first hand experience at something, there is no need to go copy & past someone else's theories.

    P.S.
    If you take the time and go to the various shingle manufacturers websites, and do a little research, you will find that is the roof fails dues to improper ventilation, the warranty is void.... see attached warranty link....
    http://www.gaf.com/Roofing/Resident...ents/System_Plus_Ltd._Warranty-45-1497-v4.pdf
    Notice Pg 2, bottom center under "What is not covered", then go up on pg 2 to the top right, section"1-C", "inadequate attic ventilation".
    If you go to any other manufacturer's websites, and read their warranties, you will find the same thing over & over.
    Hands on brings wealth of knowledge. No charge.......
  16. woodgeek

    woodgeek Minister of Fire

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    Again, no offense and I agree totally that a lot of little jobs are better done DIY than by a pro. That said, I am doing the same general 'knocking off the worst offenders' one at a time approach. I have just learned that there are usually reasons for doing things the conventional way--and usually google a problem I find before I attack it.

    I am **still** on the airsealing step. My own observations convince me that the heat loss I have through these openings is huge, and much larger than what conducts through the joists and fiberglass. I should get the last of the openings tomorrow (haha). On the first couple passes, I saw a few recessed can lights, and a few cracks around the plumbing stack. After digging around, I started to find open stud bays along the line b/w the split levels in my house. There was about 6 ft^2 of opening (in a 50 yr old house) I also found a few more square feet around the plumbing stack and another couple square feet around the interior masonry chimney (the latter sealing with sheet metal and high temp silicone). Then I thought I was done. Turns out I missed the last couple square feet, which consisted of ~180 linear feet of 1/8-1/4" wide gaps along the tops of interior load bearing walls. There are a dozen wire penetrations and a couple boxes and that's what 15 sq inches? Haven't hit those yet. FYI, I am at about 5-cans of spray foam and close to 20 tubes of silicone at this point, and I can also see a big energy savings, currently ~200+ gals oil/yr.

    My insulation is the fiberglass blown-in in 1964 (now only about 2" deep) and some 4-6" unfaced batts laid crosswise over the joists, probably 20-30 years ago. With thermal bridging and convection effects, I figure I am getting R-15, maybe, but prob not a lot more. IF my attic floor is 1500 ft sq at R-15, with my 5000 deg day climate, the seasonal conduction drain is ~100 gal oil equivalent. Going to R-30 would save me half--the equivalent of 50 gals. So the airsealing has been a much easier, cheaper low hanging fruit.

    So, with all due respect, I think you might have missed some major openings in your attic floor or interior framing. IF you have R-50+ AND you are getting noticeable savings blocking the vents, you are actually proving that you have leaks, IMO.
  17. doubledip

    doubledip Member

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    I would rather not have the roof and sheathing as a moisture barrier.
  18. seige101

    seige101 Minister of Fire

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    I do have first hand experience with a hot roof, my own house. built in 81/82 so 29 years old. No issues with my roof decking rotting!
    No issued with the asphalt shingles prematurely failing either. (Installed in 2005, first roof was cedar shingles)

    I have looked at several warranties for singles, hot roof are covered.
  19. Hogwildz

    Hogwildz Minister of Fire

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    Cedar & slate roofs almost have plenty of air space by their very nature. Also makes for great bat nests. But they are not comparable to asphalt shingles. Although same deal, soffits or some form of ventilation is always appropriate. A cedar roof should last much, much longer than 29 years. Why the need to replace already? Most cedar shingled roofs last 50+ years when properly maintained? So why such a short life? Interesting.
    Very short life for one of the more expensive roofs.

    Not sure where other than the article you found you learned the term "hot roof". But in roofing industry, a "hot roof" is a flat roof with hot tar or "pitch" as roofing.
    Just to make sure others don't get the too confused.

    You are fortunate with you roof decking then. So congrats. There are many others who are not. Of course your asphalt shingle roof is now only 6 years old, time will tell.
    The unventilated, contained heat in your attic also keeps you home warmer in the summer months. But I know, your going to tell us that that is also not the case in your home.
    To each their own.

    Very well. Look forward to you posting link(s) to those manufacturer's websites warranties showing that "hot roof" is covered.
    Post away.
    Actually, you should have a copy of the warranty for your new roof. Who is the shingle manufacturer?
  20. Don2222

    Don2222 Minister of Fire

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    You have a good point. Air sealing is very important and a good DIY job. I had a spot where I rolled up the old insulation and there was no sheet rock! Talk about air sealing!! It was between an interior closet and the chimney so it was not in any room to see! That had to be air sealed with a big piece of plywood!

    I too had to air seal around the chimney and insulate but if cold winter air does blow into the attic thru the gables, then the heated air goes somewhere?

    Keep up the good work. What will you do to improve the insulation?
  21. Don2222

    Don2222 Minister of Fire

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    Hello doubledip

    The moisture barrier in the picture of the roof is in the attic floor like it should be with insulation on top!
  22. woodgeek

    woodgeek Minister of Fire

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    The questions is: why does your attic have heated air in it? That is--if the floor is R-54, and the top is R-5 (reflectix) or less, why is your attic warm--it should run just a few degrees warmer than outside even with the gable vents closed off.

    As for my insulation: I will try to get up to R-30 or higher an the next year or so, as my elec rates double. I was going to pull up the cross batts temporarily, rake the 2" of blown FG in into every third 2x6 joist space (filling it), put new R-19 FG batts into the other 2 out of three joist bays, and then lay the cross batts back down. I figure that would get me something like R-35 or so. If I feel like it--I might do something more like what you did--double up the existing cross batts in half the area, and lay R-30 batts crosswise in the other half. Any better ideas?
  23. Don2222

    Don2222 Minister of Fire

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    Hello woodgeek

    I just saw Mike Holmes do a show where he completely rebuilt an old room off the back that almost fell down. Anyways, when he checked the blown in insulation it was completely broken down and had to be vacuumed out and totally replaced! So you may want to check the condition of yours.

    As far as the attic being a little warm I want to explain what I have learned. First of all I have found that the knowledge of good building practices drops off sharply after the building codes have been satisfied. For example only putting pro vents in the lower part of the rafters to allow soffits to vent. That satisfies the code. I asked the roofer that did my neighbor's house about continuing the pro vents up to the ridge vent? He said it is only required for cathedral ceilings and did not even think about doing it for any other type of roof. The reason I continued the pro vents can be seen by the pic of the roof I worked on in a prior post. It stops the snow from melting and adding to ICE Dams, water and moisture problems.

    So after doing that I measured the temps in the Attic. A good remote sensor on a Digital Thermometer works well and you guys may want to do that for your attics to show how your work is progressing. The temps with all that insulation were going down to below 25 Degrees F on cold winter nights with 70 degrees F in the living room below! That is good insulation!! Then I tried blocking the gables and found the temps did not go below 35 degrees F anymore!

    Therefore the house was more comfortable and the roof is still very well ventilated. I think that the heated air will escape thru the roof no matter what you do. If all heating devices in the house are turned off, then after a few days the inside temp will equal the outside temp. Where did the heat go? Heat rises and will still go through the roof!

    However I am still open to suggestions if you guys have any other ideas?

    One item I will be working in is the main vent stack from the bathroom is copper and conducts alot of heat out. Plus the height of the vent stack per the latest code should be 12" off the roof and mine seems to be 6" !! So heated gases escape the pipe before condensing!! The gases condense on the roof spilling moisture! I hope to cut the pipe in the attic and go thru the roof with PVC up atleast 12 inches to keep moisture off the roof!! So you may also want to check your stink pipes??
  24. woodgeek

    woodgeek Minister of Fire

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    Yeah, maybe I should just pull the old stuff out--I'll decide later when I price out new FG...

    I would encourage you to push some numbers on this conduction thing....

    I worked out that in my climate, one square foot of R-1 (e.g. a single pane window) loses 110 kBTU/yr, about what I would get from 1 gallon of fuel oil at 80% eff. With this mnemonic, a 10 sq ft, R-2 window (i.e. double pane) will cost me 5 gals/year, a 20 sq ft wooden entry door (R-1) will cost me 20 gals, adding a storm door (now R-2) will save me 10 gals/yr, etc. Adding up all the conductive loads on my house, i.e. areas in sq ft of each window/door/wall/ceiling divided by the estimated R-value of the assembly, I got a number like ~500 gal/year max. Yet the first year I moved in, I burned close to 1100 gallons (not counting DHW), or 2.2X the conduction load! The difference (55% of total demand) was all stack-driven air leakage. After tweaking the weatherstripping in my windows and airsealing my attic floor, I got my usage down to ~650, without adding ANY new insulation at all. It was amazing to think that these insignificant little cracks around my windows and in the attic floor could lose more heat than 1000 sq ft of crappy FG batts, but there it was. An IR thermometer told the tale--by slow scanning it around in my attic, I could find hot spots and lines across the top of the FG batts--you might try that rather than a single remote probe.

    I am still troubled by your warm attic--I get that closing the gables makes it warmer, makes sense. My idea is that IF the floor insulation and the sheathing insulation have the same area and R-value, and there is no air movement, then the middle air space should be halfway in between the inside and outside temp. IF the floor is R-54, and the sheathing is R-5 (i.e. the reflectix between the attic interior and the pro vent, assumed to be at outside temp), then the attic should run 1/12th of you inside-outside temp differential above the outside temp. If it 70 inside and 10 outside, your attic SHOULD be 15°F, with no air movement--just conduction. IF the attic is vented it should be even colder!

    Stated another way, if your attic is 40°F at 10F outside, then that is halfway to between 70 and 10, and your attic floor insulation is --effectively-- no better than the sheathing insulation. IOW, your current attic floor assembly is losing as much heat (somehow) into the attic as if is were R-5, not R-55. Not surprising that you can 'feel' the attic temp in the house below. Conduction through your FG, your plumbing stack and framing elements can't account for that much heat. The only plausible candidates are conditioned air leakage, either stack driven through floor openings or from HVAC ducting in the attic (do you have some of that?).

    Thus, I am not trying to tell you that the pro vent/reflectix/gable blocking etc doesn't work--it effectively doubles the effective R-value of your attic from R-5 to R-10. I am just saying that airsealing under all that lovely FG you installed could take you from R-5 to the R-55 you paid for.
  25. Don2222

    Don2222 Minister of Fire

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    Hello

    Remember there are 3 ways heat travels through a medium like air.

    1. Radiate (Radiant heat from a strong heat source beating down on an object)

    Foil works well to stop the heat transfer.

    2. Conduction (Heat traveling thru something like a metal such as copper. That is used in FHW baseboard)

    Insulation like fiberglass that greatly impedes the flow of heat.

    3. Convection (Heat traveling through the air using wind currents)

    Stopping Air leaks with Foam and caulking.

    So you need to attack all 3 when insulating an attic!

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