Passive vs. Powered Attic Ventilation in Florida - Page 2
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  1. #14
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
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    2,990
    Quote Originally Posted by mark beiser View Post
    I'd like to put a white metal roof on my house, but my house would look silly with a white roof, and I'm concerned about the reflection off of it causing problems for my neighbors when the sun is in certain positions.
    I bought my house in 99 because it had great shade, and an aluminum roof... yup, bare aluminum sheeting, the stuff was installed in 1949, and it's in perfect condition... there is no ventilation in my attic other than the small 14x20 gable on one end... basically useless, without soffet or a matching gable on the other end, and my attic is rarely above outside temp... bare aluminum is VERY REFLECTIVE of radiant energy. the reason there is only one gable is due to the other side of the attic being finished... sortof... the room is inclosed, but the roof sheeting and rafters are visible... 1900 tree limb rafters that is... and cedar shakes for sheeting... someone put shingles on top of those sometime after the 20's and then the aluminum was put on.
    I get comments all the time that the rain must sound awesome with a metal roof, but the aluminum doesn't make any noise from the rain, it's a dull metal that's absorptive of impact sound.
    The TRUE highest cost system is the system not installed properly...
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  2. #15
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,274
    Mark Beiser wrote:

    I'd like to put a white metal roof on my house, but my house would look silly with a white roof, and I'm concerned about the reflection off of it causing problems for my neighbors when the sun is in certain positions.
    We looked at other metal options besides the white standing seam. One of them was a "stone coated" metal shingle that is installed on top of battens, allowing the shingles to vent from the eaves to a ridge vent. I liked the idea, and several colors were available that weren't stark white (that would, such as in your case, be more neighbor friendly). However, I could not locate any data stating what the reflectivity was, or if there was reflecitivty/emissivity data, was it, combined with the back-venting, comparable to the standing seam options we were considering?

    If I had no option but to use a "shingle-like" metal product due to neighbor or HOA concerns, I'd seriously consider laying down at least one thickness of foil faced foam insulation sheathing board, then the battens, then the metal shingles. That would likely make for one seriously cool performing roof, even with darker shingle colors.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #16
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by Shophound View Post
    We looked at other metal options besides the white standing seam. One of them was a "stone coated" metal shingle that is installed on top of battens, allowing the shingles to vent from the eaves to a ridge vent. I liked the idea, and several colors were available that weren't stark white (that would, such as in your case, be more neighbor friendly). However, I could not locate any data stating what the reflectivity was, or if there was reflecitivty/emissivity data, was it, combined with the back-venting, comparable to the standing seam options we were considering?
    I really like the way they look, but the good stone coated metal shingles are to expensive for my budget on this house.

    Even with the extreme hot weather the last 2 summers, and 2 computers burning $500 worth of electricity a year doing distributed computing projects for disease research, I use less than $2000 a year worth of electricity at current rates.
    This is in a house with only 2-4" of insulation in the attic, 46 year old single pane aluminum frame windows, and a 15 year old over sized 10 SEER AC system.

    I have to balance the cost of what I'd like to do to the house against the relatively low potential return in real energy savings, and the limit to how much potential to improve the value of the house there is.

    Basically, the problem I have with this house is that if I do much more than a radiant barrier, good passive ventilation, and R-36 insulation, the ROI flips to infinity.
    If more government is the answer, then it's a really stupid question.

  4. #17
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,274
    Quote Originally Posted by mark beiser View Post
    I really like the way they look, but the good stone coated metal shingles are to expensive for my budget on this house.

    Even with the extreme hot weather the last 2 summers, and 2 computers burning $500 worth of electricity a year doing distributed computing projects for disease research, I use less than $2000 a year worth of electricity at current rates.
    This is in a house with only 2-4" of insulation in the attic, 46 year old single pane aluminum frame windows, and a 15 year old over sized 10 SEER AC system.

    I have to balance the cost of what I'd like to do to the house against the relatively low potential return in real energy savings, and the limit to how much potential to improve the value of the house there is.

    Basically, the problem I have with this house is that if I do much more than a radiant barrier, good passive ventilation, and R-36 insulation, the ROI flips to infinity.
    With the work already in place on my house prior to the new roof going on, I don't expect a huge ROI for the roof in terms of energy payback. What we do have is a roof we will never need to worry about again unless a very strong force of nature or a fire damages it (and the house, for that matter). The roof has made the interior of the house considerably quieter against outdoor ambient noise, something we did not expect ahead of time. I have no plans to move ducts out of the attic, so the reduction in heat gain will improve a/c performance, and when it comes time to replace equipment I'm expecting when I run a Manual J again that the result wil indicate I can downsize tonnage. We are also looking at future solar panels, and standing seam is friendly toward installing those units.

    If my decision re: roofing material had been based strictly in ROI for energy payback, I would likely have gone with white colored asphalt with a reflectivity of 0.29 or greater, or the less expensive reflective metal shingle options. I realize standing seam metal is not a viable option for all, and many do not like the look of it. For us it was an opportunity to enhance the appearance of the house, reduce attic heat gain, increase high wind resistance (which may increase structure survivability in a tornado F2 or less), and reduce risk of storm damage in one fell swoop. And...frankly, we needed a new roof...this wasn't a boutique decision.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #18
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    I do want some sort of metal roof when it is time to replace what I have.
    When the time comes, it will be somewhat expensive either way because I'll need to replace the decking too.
    The decking is ok now, but has some delamination, and is a little spongy in some places when I walk on it, so it won't really take another reroof.

    I need a good hail storm so I can get some of my money back from my insurance company to help pay for it.
    If more government is the answer, then it's a really stupid question.

  6. #19
    Join Date
    Aug 2012
    Location
    Florida Space Coast
    Posts
    503
    Quote Originally Posted by mark beiser View Post
    Well, he could be a great roofer and siding installer, but it sounds like he needs to stay away from fans, far far away...
    Finally decided to cut this guy loose over the weekend. I've been waiting on his proposal since July 25th. So far, all I've received is his "commentary" on how happy I'll be with the improved energy efficiency of my home if I hire him and approve all his "suggestions".

    Contacted another siding contractor through the James Hardie website last Monday. He visited on Tuesday, his roofing "sub" visited on Wednesday, and by Friday evening I had detailed proposals in hand for both the roof replacement and new siding, including specs regarding enhanced off-ridge venting to replace the inadequately sized existing ridge vent.

    The siding proposal was quite reasonable, including new vapor barrier, whole house re-paint (primer plus 2 coats), and re-installation of screening that has to be removed to install siding in the atrium. The roofing estimate was a bit higher than I'd received from others, but it does include a 15 year workmanship warranty from the installer compared to 5 years from the others. Unfortunately, the roofer has been in business less than 10 years, so the warranty may not be worth what they're charging.

    I may still shop around on the roof and ask the siding contractor if he will consider using a different sub.

  7. #20
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by Florida Joy View Post
    The roofing estimate was a bit higher than I'd received from others, but it does include a 15 year workmanship warranty from the installer compared to 5 years from the others. Unfortunately, the roofer has been in business less than 10 years, so the warranty may not be worth what they're charging.
    This reminded me of something from a few years ago.
    A friend of mine bought a new car from a dealership that was having a going out of business sale, got a great deal too.
    They even gave him a discount on their in house extended service plan....

    I still haven't let him put that episode to rest.
    If more government is the answer, then it's a really stupid question.

  8. #21
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,274
    I began monitoring my attic temperatures on Sunday, a day that topped out at 96 degrees. On days like that, even this time of year with a reduced sun angle, I would expect normally to see attic temps over 100 degrees at solar noon. My attic was around 82 degrees. When the outdoor ambient temperature finally leveled out at 96, the attic temp caught up and leveled out at the ambient air temp. But it took six hours from the time I got the temp sensor activated to get there. In that time span, the outdoor ambient temp was above attic temp.

    Yeah, there is something to this reflective roofing scheme, after all.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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