Guest User
6/7/2012
Previously, I wrote in about the effeciency of soffit and ridge vents with a new metal roof. Attic temperatures hover around 100 degrees on a bright, sunny 80 degree day. Temperatures seem to drop fairly quickly after sundown or after clouds roll in. We reinsulated the attic floor two years ago with open-cell foam and installed baffles to protect the soffit venting. A new ridge vent was installed during the re-roofing. I stumbled upon " ridge-vent-booster fans " marketed under the name TJURNLUND. They install under the ridge in the attic and consist of a metal box with fans that apparently force air through the ridge vent and subsequently draw more air through the soffit openings. Based on their formula I would need two such vents installed several feet apart. Are you familiar with such products? The soffit vents appear to be clear and clean but I intend to either scrub or vacuum them this weekend. Thanks in advance, RgN
Todd Miller
Isaiah Industries, Inc.
6/8/2012
I am not aware of such fans but I do not think there would be any negative impact from them.
Guest User
6/8/2012
Thanks! I'll investigate and let you know what I find. RgN
Eric Novotny
An informed customer is the Best Customer!
6/8/2012
Is this what you are referencing? http://www.tjernlund.com/Roof-Vent-Booster.htm I would say no. A 100 degree attic is nothing in the greater scheme of things and your insulation and envelope layer is at the attic floor. If you have properly sealed it (sounds like you have with the spray foam and other measures) than the communication between the conditioned and unconditioned spaces should be nil. Attic ventilation is all about controlling moisture and not about temperature. If you go into the attic and feel convection across the back of the sheathing heading to the ridge, that is proper and your ridge vent/soffit combo is working. Soffits should always be aimed at about a 60/40 split to ridge venting in terms of volute and area. This will keep the attic from getting negatively pressurize and contributing to air exfiltration. Negatively pressure in the attic (via a fan sucking air out) is not a good thing and contributes to exfiltration while consuming energy to do it. As said before, a 20 degree delta between ambient and attic air is not bad and well within the normal range for a properly vented attic. Make sure you have an R-50 on the attic floor and you should be perfect.
Guest User
6/8/2012
Thanks for getting back. I called the company and was advised that the fans are NOT intended for use below a ridge vent. They are intended for use under square vents, what the guy referred to as " roof jacks. " He advised to simply stick with the soffit and ridge system and not add fans. The name of the product is somewhat misleading. Anyways, this morning, just to play it safe I went up to the attic and blew air through the baffles just to make sure that the soffits are not blocked. As expected, I didn't get much out of them since the whole attic was cleaned out thoroughly before the spray foam was installed two years ago. This is a ranch house in the shape of a letter " T " as per a room addition. The main section measures 25' X 65' X 6' high. I counted the baffles as I was cleaning and found 32. However, most of them are in what amounts to about half of the area. Because of the addition, which has a cathedral ceiling, there are fewer in the other area. When the room was added the carpenters cut an opening between the rafters leading to the cathedral area. This opening is about 16" X 40." Half of the cathedral ceiling is just below the roof deck--( 2x8's with 6" of fiberglass insulation. ) The other half is a large open cavity which gets a lot of ventilation as it extends over a covered porch. Would it be wise to increase the size of the existing opening by cutting between the rafters or even cutting a few more openings to enhance the communication between the open area above the covered porch and the original attic. I'll try to send a picture in another posting for clarification. Using Demilec's values, I should have about R-45 on the attic floor. They claim 4.45R/inch. Air sealing appears to be very good. The winter after going with the foam we had NO icicles and as I think I mentioned in another posting, heating bills have shown about a 22-23% reduction in cubic feet of gas used. Regarding the negative pressure thing--- are you saying that the soffits should represent the 60% and the ridge 40%? Do we NOT want to draw the warm air out via the ridge vent? I am not sure if I can feel air moving up the sheathing. I may invest in a container of " canned smoke " to test it. Humidity readings seem to hover around 50-60% but I have only had a hygrometer up there for a few days. I realize that a lot of this may be overkill on my part, but I just want to maximize the situation. Thanks again, I've learned a lot from you guys! RgN
Eric Novotny
An informed customer is the Best Customer!
6/9/2012
Post a picture (both inside the attic and from outside) or just email one to me and I will let you know what I think. Convection will push the warm air out of the ridge. Nothing is getting sucked out of the ridge. The issue with most venting is that people have more exhaust than intake and when you do that, you drive negative pressure in the attic and create a scenario where you suck more conditioned air out of the space. 50/50 is perfect but people never get to that so by saying 60/40 on the split with the high side being intake, it makes it a safer bet that you are closer to the 50/50 split. More intake vs. exhaust also does not drive negative pressure and therefore does not create more air loss.
Guest User
6/9/2012
Thanks again. I'll get some pictures tomorrow and send them. I understand about the effect of negative pressure drawing conditioned air from the living space. However, allowing that the spray foam has done a pretty good job of air sealing, would this be much of an issue? I was thinking that more exhaust at the ridge would draw cooler replacement air through the soffits. I think that what you are saying is that the air movement is more dependent on higher pressure at the soffits than lower pressure at the ridge----Yes? RgN
Eric Novotny
An informed customer is the Best Customer!
6/10/2012
With SPF on the floor, the envelope should be tight as a drum and air leakage should be a non issue. You need a balance and additional square footage at the ridge will not speed up intake and air changes of the attic. A powered fan would accomplish that, however, at what cost of energy and installation. If you have sufficient insulation in the attic, attic temps are largely inconsequential. Attic ventilation is about moisture control and not roof surface temperatures. Convection is what drive the air changes (i.e. warm air rising and leaving the attic creating the negative pressure in the attic and driving intake air in).
Guest User
7/13/2012
Previously, you commented on the 60/40 or even 50/50 split for the soffit and ridge venting. I came up with the following values: Continuous ridge vent is 88 feet. There are 42 soffit baffles and light is visable from most of them. I have a large tree in the front yard that may be blocking the light to a few. There are two 16" X 60" openings between the original roof and the roof of an added room and porch. There is a large open cavity over the porch and again, light is visible through the soffit areas. The soffit itself is vinyl with every third panel being vented with small circular holes. I don't think that the negative pressure deal would have much impact on drawing conditioned air from the living quarters since the attic floor has several inches of open-cell sprayed foam insulation and should be pretty well air sealed. As per your request, I still intend to send pictures. Any thoughts would be appreciated. Thanks again, RgN
Eric Novotny
An informed customer is the Best Customer!
7/14/2012
I would prefer to see a continuously vented soffit because vinyl soffit is notoriously stingy on air flow. With that kind of layout, I would guess that the attic is more than ventilated and openign up the eaves a bit more will give you all of the venting you need. I still would not go with the fan option personally. Don't like the additional penetrations in the roof or the power to run it.
Guest User
7/15/2012
Thanks for getting back. I'll look into increasing the amount of perforated soffit and forget about the fans. Now for a new question if you don't mind. I thought that I did pretty exhaustive research going into the metal roof. One thing that I may have overlooked concerns fasteners. I knew that they were using 1 and 1/2 inch galvanized roofing nails but I never gave a thought to whether they would be hot-dipped or electro-galvanized. While I had them leave an extra box of shingles ( 1/2 square ) I do not have any left over nails. I can see almost an entire nail between the sheathing boards in two locations that were " misses. " The nails have what looks like a barbed portion in their upper 1/2 inch next to the head. They are somewhat shiny so I assume they are EG. When I emailed the installer he said that they usually use hot-dipped, but that they might be EG. Should I be concerned? I've read where the EG nails deteriorate quickly if exposed. None of these are exposed as per the interlocking panels. The " architectural installation manual " on Futureroof's site says that, " All fasteners are to be supplied by Futureroof. " One would think that would mean that the nails that they used are appropriate. Interestingly, I checked the box stores and local places and found very few hot-dipped roofing nails available. My builder customers tell me that they use EG routinely on asphalt shingles and have no problem, but the metal may be different. Thanks again.
Paul Lyons
sunroom roof "pops" when sunny and/or windy
7/29/2013
Two years ago I had a 17x19 sunroof addition put on my house. From the get go the roof (foam sandwiched between aluminum sheets) has "popped" and banged like fireworks going off when the sun comes out around 10 AM and continues until early evening. Windy conditions can cause this as well though not usually as noisy or long in duration as the sun. The sunny part of the problem is obviously an expansion/contraction thing...not sure what's going on when it's windy. Anyway I am looking for someone- anyone - who might help fix this or point me in a direction....the noise is very annoying. The original contractor who built the room did a very nice job other than this issue and he is just unreachable...I am in southeast lower Michigan and would appreciate any thoughts.
Todd Miller
Isaiah Industries, Inc.
7/29/2013
Paul, thanks for your questions. This, though, is a horse of a different color compared to residential metal roofing. I would suggest contacting someone local with extensive patio enclosure experience.
Eric Novotny
An informed customer is the Best Customer!
7/30/2013
Paul, Who is the manufacturer of the sunroom? Is the structure aluminum or vinyl? What type of metal roofing system is down on the roof? Eric
Guest User
7/30/2013
I have come to this forum sort of as a last resort...I have called other sunroom folks and because it's not theirs they want nothing to do with it. I have talked to our township inspectors etc. and they have no idea. I know it's different from what metal roofs you folks deal with but I was hopeful there might be some similarities, enough anyway that someone might point me in a direction. I don't know the name of the manufacturer....the people I bought it from, Mr. Enclosure have been in our area forever 40 years and you would have thought that meant they stand behind their work....but it hasn't meant that in this case. The owner always maintained he was going to fix this but has been virtually unreachable for almost two years now....though still in business. He spends most of his time in Tennessee these days....thus the difficulty finding him. He made comments to me back in the early days about the manufacturer being in New Jersey...but never said a name I can recall. The main structure of the building is vinyl clad aluminum. The roof is constructed of aluminum top and bottom with some form of Styrofoam in between. The roof consists of several pieces of this roughly 20'x 3 1/2' "sandwich" material running parallel to each other. Any thoughts appreciated.
Todd Miller
Isaiah Industries, Inc.
7/30/2013
There are a lot of companies that have produced these sort of structures over the years. I sure can't imagine how disconcerting this must be. The big reason I am shying away from this though is I think the problem here may be related to movement of the structure itself rather than just the roof panels. I just feel out of my league on this but noise like this I am concerned could be coming from the structure moving and banging into the house.
Eric Novotny
An informed customer is the Best Customer!
8/2/2013
Paul, What color is the roof? The popping noise can be the result of the panels expanding against one another as well but I would be equally concerned with Todd's assessment about the room movement. Is there a local contractor that might be a family friend or resource that you can have take a look at it. Where in NJ are you?

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