Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Halo on October 10, 2008, 06:04:10 PM
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For all you handy persons, what do you think of ridge ventilation for your house roof? I just got vinyl siding on our two-story house and will have to replace the roof within a couple years. This will be total roof refurb since it already has its second layer of shingles.
I'm already concerned about attic heat. A thermostat fan at one end comes on when the attic temp reaches about 90 degrees. That has worked well for many years. But our original soffit was wide ovals covered with inside screens. These became a nuisance as critters learned to butt in the screens. More staples and a few brick weights kept the screens in but restricted some ventilation.
The new vinyl soffit was installed over the old soffit. The new soffit has rows of pinholes about a foot or so apart. Seems like airflow will be considerably restricted over previous oval screens. Already the attic fan seems to come on when outside temp is about 75 degrees instead of 90 degrees.
This has me thinking maybe I better think about replacing my roof shingles next spring and adding a ridge vent as well as getting a new attic fan too since this one has been in about 30 years.
I'm Googling this on other appropriate house sites of course, but am curious what relevant attic ventilation experience and advice you might have to share.
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Do a ridge vent! Up here in NY it lets the attic stay cold so it doesn't melt the snow on the roof which will end up giving you ice dams and can back leak water into the house.
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Ridge vent is the way to go. As hot air rises and is released through the ridge vent, cool fresh air is drawn through the soffit, eliminating the need for mechanical venation. You should have pulled the old soffit off first though...
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(quote) You should have pulled the old soffit off first though... (unquote)
Yeah, I should have questioned that. The contractor seemed knowledgeable (famous last words), and I didn't realize how limited the new vent holes were until he completed the whole back section. When I asked the question, he said that installing the new soffit over the old would be fine.
The contractor was great about repairing deficient underlay throughout the siding, fascia, and soffit. Once everything was satisfactory, he installed vinyl and some aluminum over the existing wood and compressed board, adding insulation beneath all the siding. We kept our storm and double-pane windows, so he meticulously sheathed the frames.
In retrospect, my amateur observation suggests the soffit ventilation must have been reduced by half or more. That guess seems supported by the attic exhaust fan running during outside temperatures about 10 degrees cooler than it used to (it is set to start when the attic temperature reaches 90 degrees, which I think used to happen when outside temp was around 80; today the fan was running when the outside air was 72).
From what I read, apparently an eventual vent ridge won't solve a problem of drawing enough air through insufficient soffit holes. So at the risk of prejudicing your honest answers, I'm hoping information in this thread and elsewhere on Google searches will alleviate my concern so I don't have to worry all winter about too much heat in the attic and a potential moisture and mildew problem.
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You have real concerns. As another post stated, too warm of an attic will cause snow on the roof to melt, then refreeze at the eave causing an ice dam with the potential of serious damage. In southern states stale moist air will cause mildew and dry rot, not to mention increase your AC cost. Adequate ventelation at the soffet is a key to proper ventelation with a ridge vent system. On my roof the only place that snow melts is where the water heater vent is. In the summer my house rarely gets above 75 degrees. I have a ridge vent system and 18 inches of blown insulation in the attic. If you have blown insulation make sure it isn't blown into the eave and blocks the soffet vents. They sell Styrofoam channels at Home depot that you staple between the trusses to allow air flow from the soffet vent in homes where the insulation is too deep to allow circulation.
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I would definitely go with ridge vent here. This will add to the already present ventilation. To this comes many benfits of one of them is the less frequent your attic fan will have to run. Another is one (I am finding out now) is you will thatit will help keep condensation from forming under your tarpaper(underlayment) and allowing it to seep into your attack space in the winter (of course this also depends on the area you live in and how bad the weather typically gets in the winter). A third reason to have the ridge vent is also the preventing of melting ice and snow that can form ice dams.
The condensation issue will present itself becasue of the difference in temperatures between the outside air and the temp of your attic space. This is trouble I am having now and am working to straighten out. While on a tight budget, and when I did the roof I could have done it much easier cheaper and my budget was a little more loose then too. Oh well hindsight is 20/20 so they say.
That thermostatic control on the attic fan is be nice for helping to keep that space cooler in summer but won't be much help with preventing damage during the winter months. This is where the additional ventilation will help.
My point don't skimp get the ridge vent, more of a plus than a negative.
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First question. Hip or gable end? Hip = no Gable is o.k......depending.
Also, decide on one ventilation method and stick to it. They aren't designed to work together. Power vents can easily disrupt a well laid out convection system. Sometimes causing more harm than good.
Tips:
- Make sure you use a baffled ridge vent if you do it.
- Get as much airflow as you can reasonably achieve before you let your siding guy go. Aluminum or vinyl soffit isn't very air tight. You can actually get away without perforated panels if it's installed over unfinished eaves.
- If you have blown in, it's almost certain you have some obstruction. It's important to clear the eaves and if you use the baffles, only run them far enough to clear the insulation. And they have to be installed at every rafter space.
- If you've got varmints trying to move in with you through the eaves, it sounds as though you need to get rid of trees or bushes that are within a few feet of the house. If they went through the screen vents, they'll just laugh at the vinyl soffit.
- dkff49, this one's for you. From what you said it sounds as though you have too much moisture up there, not necessarily inadequate ventilation. The first thing I'd look for is an improperly ventilated bathroom fan.
There's an obvious argument for not cutting more holes in your roof than you need. There are also some practical considerations to look at when designing a system. It's not complicated but it's often ignored. My usual advice is to employ the method that was designed into the original house unless there's a compelling reason to modify.
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I get what you are saying there Thruster. The thing with my roof though is I have no bathroom fan and most of my problem is combination the inadequate ventilation and the attic space is partially finished. I have heated space all the way to the rafters with very little insulation. The space was finished prior to my buying the house and I know it wsa done wayyyyyyyyy back.
The insulation is many years old. I mean how long has it been since you could buy cellulose insulation in bats with paper backing? Unfortunately with my limited budget at this time I am only able to do very little at a time and picking away at it slowly.
Aside from that the problem exist acrossed the entire length of my roof and only on the shade side of my house and only have water in attic on coldest of days and usually with snow on roof.
I did not really think that the forced system would work against the convection system (not arguing just didn't realize). It's just thinking this out the powered system is not going to do much to prevent the winter issues (or so I would think).
To add to that, I am not an expert nor do I do any of this for a living. Jack of many trades but master of none. I know just about enough to make things go around my house with a little experience in what not to do from my own mistakes which is where my information comes from.
I do thank you though for your input with my issue though thruster
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Make sure you get a certified radiant barrier installed as part of the basic roof install, not some spray-on stuff afterwards. It requires replacing the ply sheathing if you really want it done right, but then it will be a lot more effective than the spray-on stuff and cheaper than paying people to install the good stuff from inside the attic.
As for vents, I think a ridge cap is still the way to go. End vents should be replaced and sealed properly or they can be an endless source of leaks and an endless target for more and more roof tar (personal experience). A roofer told me that there are set formulas for how many spinners or other conventional vents you need, based on both square ft of roofed area AND the volume of air under the roof which is determined by how steep the roof pitch is.
In any case, if you do a complete re-roofing, ensure you have good insulation (a couple ft of blown insulation is reasonably inexpensive and can keep home heating/cooling expenses down), get the radiant barrier installed with certified materials and not just whatever stuff comes in the shiniest can at home depot (look it up online), and either use a ridge cap or ensure the roofer makes the calculations to determine how many vents you really need. Original home builders will sometimes completely ignore the calculations and install half or less of the number of vents really required... I have a very tall roofline and the builder put in HALF the vents my roof should have. It doesn't get overly hot due to vents on the end and the fact that my area has a fairly constant breeze, but if I ever had to do a complete re-roof and was going to keep the house more than a few years I would either have them use a ridge cap vent or add another handful of vents based on attic volume.
In terms of pure effectiveness (and assuming you already have somewhat reasonable venting), I think the order of importance is conventional insulation, radiant barrier, and improved venting. Slightly fewer than ideal number of vents won't kill you, but not having enough insulation is a huge problem and the radiant barriers are supposedly really good nowadays as long as they're installed properly and you use the right materials and not just some goop with "teh radient barr13r!!!111one" on the can.
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dk,
I'm not clear on exactly what your situation looks like but here's the general idea.
If you're getting condensation, you have too much humidity, obviously. A lot of rehabs forget to include HVAC mods to compensate for new living space. Unless you keep the house intentionally hot and wet (yeah, yeah, I know. I said "hot and wet") there's a shortcoming with the interior moisture control. A new cold air return may help. But you do need to separate the attic from the living area and get the moisture out for sure. Vapor barriers can be helpful but poorly thought out can cause even more problems. If you have a vaulted ceiling with just the rafter depth between sheetrock and deck you need to make sure you have airflow. If it can't dry out you will grow mold.
The ridge vent issue is more straightforward. the first thing to consider is the ridge. If you have hips, the math won't work. Otherwise, a good rule of thumb is 1 breather vent per 300 sq./ft. of living area with an equal if not slightly larger area dedicated to inflow. Hot attics in most homes are more a problem of perception than anything. Roofing materials are pretty robust and heat usually travels up. If the living space is holding heat (attic insulation) then the issue is more about air exchange. It has to be balanced and adequate. Ridge vents do look nicer but sometimes they are not the solution. Of course sometimes they are the best solution but usually the whole roof system has to be set up right.
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Since I have you here Thrust and you seem willing to help, I will try to clarify for you what is going on here.
First I will start with a link to another forum that I have posted this problem before.
http://www.handymanclub.com/Community/Forums.aspx?g=posts&t=29474 (http://www.handymanclub.com/Community/Forums.aspx?g=posts&t=29474)
I am however aware that the biggest part of my problem is insulation but the ventilation is a start and the least expensive and least time consuming of all of them. I also am aware that I have not fully taken care of the ventilation issue yet either.
Here is a "VERY" basic drawing of a cut away of my house, looking at it from the front. The left side is shaded most of the time and also shielded from wind most of the time as well.
(http://i295.photobucket.com/albums/mm146/dkff49/diagramofhouse.jpg)
always open to suggestions, unfortunately my pocketbook is not nearly as open as I am right now. I do note all and take care of those that seem legit and those that I can not afford at this time I note to make changes to later.
Thanks for your time.
edit: I neglected to mentiont that in the winter (during the coldest days) all the deck boards on that left side of the house are wet. Now I don't mean just a little damp, I mean so wet that they drip onto the totes below, inside the crawl spaces. Looking in through those rafter spaces from the crawl space (remember I said that there was very little insulation)I can see that all the wood is wet all the way to the peak. The deck is also wet the entire length of the house (28 ft long). One end of the upstairs is insulated but not vented it is equally wet in that end in the winter.
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<---is a contractor and I do mainly roofs.
What part of the country do you live in? What type of roof is it? (as asked by someone else) Can you post a pic of the house? Besides the fan and soffit is there any other roof ventilation ie: old style box vents or other in roof vents? I still like the box vents...they are easy to install, fool proof, and they work. You can get ridge vent but there are allot of different styles. If your going to spend the money get good ones! Not the cheap rolled corrugated plastic type. The type you are looking for are a hard plastic with some sort of screen on the back side to stop larger dust from getting inside the roof.
Ridge vents are very popular but are not right for every app.
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Also when they install the ridge vent ensure they have cuts (openings) on both sides of the peak. The company that put mine in only cut about 2 inches off of one side. So I lost half of my potential air circulation out thru the vent. Weird!
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dk,
Can I call you dk? I hope it's not too informal.....
Whatever. Anyhow I saw your other thread and can see you've gotten a bit of advice already. Let me make one clarification. Felt is the waterproofing, shingles are the weatherproofing. They armor the felt. It's important.
I read somewhere that a family of four can put as much as 2 gallons of condensation into the household airspace every day. Years ago homes were extremely porous and moisture usually found a way into or out of a house through all the myriad gaps around windows, doors, attic penetrations and the like. For the last 30 years or so we've been focused on sealing up every dollar wasting crack and adding vapor barriers wherever we could find a spot to cover up. In a lot of cases we've created problems where indoor humidity gets trapped and causes all sorts of unwelcome conditions. You should probably get an indoor air quality assessment when the budget allows.
As for the roof it looks as though you may be in what we call a "Cape Cod" style house, ( commonly single story, tall pitch, gable end roof line, sometimes a dormer or two) which has a converted attic. It's common to insulate the walls/ceiling of the conversion and often there's plastic sheeting or plastic backed insulation acting as a vapor barrier. That's what they told us to do back in the 70's when this whole new methodology emerged. Problem is your house was probably not designed to have it's attic taken up by bedrooms. The ventilation got short-circuited, the original air volume where condensation would normally dissipate went away and now what was not a problem is a big issue.
Assuming the shingles went down as per directions ( I read about the felt issue, BAD dk) and you don't have any dormer roofs, vent collars, or chimney flashing causing water to enter from the roof we have to look inside to find the cause of all that condensation. I still wonder if it's a bathroom ventilator. If your house is like the million or so I've seen with a converted attic, the baths are usually still on the first floor. Unless it's an uncommon design it will be, like the kitchen, in the "back" of the house. Over them is usually attic space/wet wall since the plumbing vents rarely get moved. If you can say the there is no "fart fan" in the bathroom or that it has a proper duct and roof vent then we have to look at more complicated fixes.
If there's no fan or it's installed properly (which is rare) then you need to look at your heating system. Forced air units usually have a humidifier which can be turned up too high delivering too much vapor into the home (happens a lot). Also fairly common is the lack of cold air returns installed in attic conversions. You need to pull air from rooms with supply vents if only to effect adequate circulation but also to get moist/cool air back to the furnace which will de-humidify. Often this condition telegraphs itself with the creation of mildew, not always but often.
If you have a radiant system then it can be that a bleeder is leaking, another common problem but that usually manifests right where the problem radiator sits.
There's also the issue of humidity bleeding up via a chimney or duct chase from the basement and causing the condensation but I doubt it. It really sounds as though you have a source of uncommonly humid air being introduced into your attic spaces.
It just occurred to me that you may have a power attic fan. There's an outside possibility that it's equipped with a humidistat controlled switch. If so, disable it. One problem with power vents is that they move around 300-400 cfm. or more and since most inlet vents can't support that much free airflow they suck air in from every gap in the roof. Sometimes the humidistat triggers during high outside humidity periods (rain) and can actually suck water into the attic. There's also a small chance your roof install is causing some water intrusion but I doubt it.
Now, as far as attic ventilation is concerned what I typically do on houses like I've described is install gable-end vents at the peak and vents at the ends of both front and back crawl spaces. That means three vents per side. Once that's done you can usually insulate and vapor barrier until the cows come home. You've created airflow and if you have any breeze at all, Mr. Bernoulli will handle the rest.
Sorry for the wordy reply, now you see why my kids ask their mom most of the "where do babies come from?" type questions.
But seriously, look for the bathroom vent. The number one cause for the condition you describe in my limited experience. I've had homeowners tell me the same thing (no vent) and sure enough, we look and there it is. I've gotten to the point where I can tell how many females are in a home just by the size of the ice sheet forming on the underside of the deck. Just don't wrap up the living area until you've addressed the venting. That can be a nightmare.
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I am assuming the ridge vent will be running the length of the house. From what i know about them, they work quit well. Do some search on them and see what you can find out.
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dk,
Can I call you dk? I hope it's not too informal.....
Whatever. Anyhow I saw your other thread and can see you've gotten a bit of advice already. Let me make one clarification. Felt is the waterproofing, shingles are the weatherproofing. They armor the felt. It's important.
I read somewhere that a family of four can put as much as 2 gallons of condensation into the household airspace every day. Years ago homes were extremely porous and moisture usually found a way into or out of a house through all the myriad gaps around windows, doors, attic penetrations and the like. For the last 30 years or so we've been focused on sealing up every dollar wasting crack and adding vapor barriers wherever we could find a spot to cover up. In a lot of cases we've created problems where indoor humidity gets trapped and causes all sorts of unwelcome conditions. You should probably get an indoor air quality assessment when the budget allows.
As for the roof it looks as though you may be in what we call a "Cape Cod" style house, ( commonly single story, tall pitch, gable end roof line, sometimes a dormer or two) which has a converted attic. It's common to insulate the walls/ceiling of the conversion and often there's plastic sheeting or plastic backed insulation acting as a vapor barrier. That's what they told us to do back in the 70's when this whole new methodology emerged. Problem is your house was probably not designed to have it's attic taken up by bedrooms. The ventilation got short-circuited, the original air volume where condensation would normally dissipate went away and now what was not a problem is a big issue.
Assuming the shingles went down as per directions ( I read about the felt issue, BAD dk) and you don't have any dormer roofs, vent collars, or chimney flashing causing water to enter from the roof we have to look inside to find the cause of all that condensation. I still wonder if it's a bathroom ventilator. If your house is like the million or so I've seen with a converted attic, the baths are usually still on the first floor. Unless it's an uncommon design it will be, like the kitchen, in the "back" of the house. Over them is usually attic space/wet wall since the plumbing vents rarely get moved. If you can say the there is no "fart fan" in the bathroom or that it has a proper duct and roof vent then we have to look at more complicated fixes.
If there's no fan or it's installed properly (which is rare) then you need to look at your heating system. Forced air units usually have a humidifier which can be turned up too high delivering too much vapor into the home (happens a lot). Also fairly common is the lack of cold air returns installed in attic conversions. You need to pull air from rooms with supply vents if only to effect adequate circulation but also to get moist/cool air back to the furnace which will de-humidify. Often this condition telegraphs itself with the creation of mildew, not always but often.
If you have a radiant system then it can be that a bleeder is leaking, another common problem but that usually manifests right where the problem radiator sits.
There's also the issue of humidity bleeding up via a chimney or duct chase from the basement and causing the condensation but I doubt it. It really sounds as though you have a source of uncommonly humid air being introduced into your attic spaces.
It just occurred to me that you may have a power attic fan. There's an outside possibility that it's equipped with a humidistat controlled switch. If so, disable it. One problem with power vents is that they move around 300-400 cfm. or more and since most inlet vents can't support that much free airflow they suck air in from every gap in the roof. Sometimes the humidistat triggers during high outside humidity periods (rain) and can actually suck water into the attic. There's also a small chance your roof install is causing some water intrusion but I doubt it.
Now, as far as attic ventilation is concerned what I typically do on houses like I've described is install gable-end vents at the peak and vents at the ends of both front and back crawl spaces. That means three vents per side. Once that's done you can usually insulate and vapor barrier until the cows come home. You've created airflow and if you have any breeze at all, Mr. Bernoulli will handle the rest.
Sorry for the wordy reply, now you see why my kids ask their mom most of the "where do babies come from?" type questions.
But seriously, look for the bathroom vent. The number one cause for the condition you describe in my limited experience. I've had homeowners tell me the same thing (no vent) and sure enough, we look and there it is. I've gotten to the point where I can tell how many females are in a home just by the size of the ice sheet forming on the underside of the deck. Just don't wrap up the living area until you've addressed the venting. That can be a nightmare.
I want to start by thanking you for taking the time to read my other post and for taking the time to put your input here. You have given me some other things to think about as I will describe a little further down.
You can call me dk for short :D
You are right about the cape cod style house only no dormers (wishes he had enough money for full length on one side of the house). It does have high pitch as well. With my limited experience and best guess I would say 10/12 (or whatever is the right way to type that), very difficult to walk with out some sort of support.
The house was built in 1948 and the only insulation that has been added since then was when they added the living space with that batted cellulose insulation and 9 years ago when I remodeled the one end up stairs for my then newborn daughters bedroom which was done with fiberglass insulation.
Air quality testing is not a bad idea though. I have changed 3 of 8 windows downstairs and both windows up stairs, but that was well before these problems started.
I am 100% sure that I have no fart fan because I have changed out the fixture in my bathroom a few years ago and there is no duct work or venting system above the fixture. The bathroom is located on the left side and in the middle of the house but yes it is next to the kitchen which is (believe it or not) in the front left side. The problem area is on the same side as the kitchen and bathroom though and the crawl or attic space is above those.
I have forced air system but it is hardly used. It night 4-5 times a day due to the fact that I burn wood and it mostly heats the house during the day leaving the furnace to run only at night. There also is no system on the furnace or in the house to add humidity into the house. The only exception to that is the pot of water on the woodstove in the basement. The house is usually very dry and dusty during the heating season though.
Now when you mentioned the chimney this got me thinking about some of the changes since the new roof was put on.
The change with the new roof was the elimination of the chimney from guess where, the left side of the house or same side as problem. This chimney was used for the old furnace. I removed it because the new furnace is a high efficiency furnace and uses pvc pipe through the wall for exhaust (which is working fine). When I changed the furnace I placed cold air exchanges in the bedrooms and they are definitely positioned in a location to get amximum airflow (trust me when the furnace runs you here the airsucking through them). The furnace opening in the chimney is blocked with (don't know technical name) foam rubber insulation in the basement. The plan for the chimney was to remove it as we remodeled t each floor (of course starting upstairs for obvious reasons).
Now originally there was no ventilation in the attic spaces or the upstairs anywhere but there was also a double layer of shingles on the roof when I bought the house (thinking probably has nothing to do with current problem other than it may have masked the problem prior to changing the roof).
I noticed that you suggested gable end vents. The only problem with that is the walls of the house are built entirely out of 6 cinder block, which makes this even more difficult to do without the use of ridge venting. I do mean entirely to (subtracting the interior surfaces), the block goes to the rafters even on the end walls. I can see the block in the crawl space.
After reading your post though it seems as though I have added to the problems already there (through the age and prctices at that time) with a few of my own and finally placed the straw that broke the camels back (I know I now show a little age here).
Again thanks for your time and advice here it is appreciated.
I know now I am not the only one who likes to make long posts. :D
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Probably one of the first questions should have been "when did this start?" then, "did anything change immediately prior?".
If your new furnace is venting straight through a wall and not borrowing the chimney, it's safe to assume it's not a culprit. BTW I believe that style of house is called a cottage if it's oriented sideways, my fault for not paying closer attention to your detail earlier. The vintage suggests that the original attic ventilation was probably two windows, front and back. The original furnace was probably a gravity system, in Pa. probably oil burning. Big ducts, but still not suspect. I did notice your mention of hearing the returns suck air. I'm not an A/C guy but I don't think you should be able to notice any substantial noise, if the system's airflow is well balanced it should be fairly quiet.
The fact that water collects in the attic still suggests that there's too much humidity but you'll have to chase that mystery, maybe a poorly vented clothes dryer? Otherwise, and don't take this the wrong way but I'm noting you decision regarding the felt, the fact that there's no humidifier installed on your new furnace and questions regarding air circulation when the basement wood stove is being used as a primary heat source, you may have to "start over". I'm thinking maybe installing (properly) a bathroom ventilator, double checking your furnace vent (high efficiency units generate a lot of condensation) and dryer, and maybe just running the furnace fan when the stove's generating the heat. Then it may be time to consider re-doing the roof.
Around here most homes of that style have little or no overhangs. If that describes yours then you'll need a gutter edge vent to complement any ridge system you install. Just make sure the rafter spaces are clear. One of the nice things about ridge vents is that air passing over the structure causes air to be moved through the system (Mr. Bernoulli again) and will get moisture out even in the winter when convection isn't really happening. The other solution is a High/Low array of breathers.
Good Luck.
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The only change I can note that happened immediately prior to noticing the problem was closing up some holes in the soffit and facia boards (created by rot and animals). To offset this once I found the moisture I drilled those 3" holes in the soffit and placed round vents in there (as described in other forum). The only thing I have not done yet was add the vent in the ridge. Hopefully this will have helped with my problem and it won't show this winter.
Nice guess on the old furnace though. Most of them on my street are or were gravity systems but coal. The others are or were forced hot air and burned oil (this was mine). I spoke with some of the original residents and they said that when our houses were built these were the 2 options available.
The air sucking really is not that obvious but is audible and I was simply trying to stated that there is definitely air moving through the vents.
Thanks again though I will be watching very closely this winter and I have watched it through this summer with no signs of water. Crossing fingers and holding breath (well not really) hoping that winter has same result as the summer has.
Thanks again always worthwhile to get another opinion.
:salute