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Homeowner Forum / Construction / July 2008Ventilation Problem – Attic
Picture two roofs – a major and minor – with the minor 1/3 the size of the major T-boning into the major at the middle on one side only. The space between the roof and ceiling of the minor is about 200 cubic yards; too small to move air with a gable fan according to several supply houses I’ve called. The problem may be caused by the fact that the sheathing of the major roof runs about a foot below the level of the ceiling of the minor. I had to get on all fours and stoop under the end of the sheathing before I could stand upright and enter the minor roof to add insulation. A possible solution may be (this is question) to cut the sheathing of the major roof where it meats the minor to create a large opening and permit air flow (will it?). I could always replace the sheathing if it doesn’t solve the problem. Phrased another way, by enlarging that opening at the junction where these two roofs meet, would the air flow improve (there are gable vents at all ends of both roofs) in the minor roof or would I simply disturb the air flow in the major and create an additional problem for myself? P.S. House is in Ohio. Cold winters. What about a continuous ridge vent? A possible solution may be (this is question) to cut the sheathing of the major roof where it meats the minor to create a large opening and permit air flow (will it?). I could always replace the sheathing if it doesn’t solve the problem. Phrased another way, by enlarging that opening at the junction where these two roofs meet, would the air flow improve (there are gable vents at all ends of both roofs) in the minor roof or would I simply disturb the air flow in the major and create an additional problem for myself? P.S. House is in Ohio. Cold winters. Picture two roofs – a major and minor – with the minor 1/3 the size of the major T-boning into the major at the middle on one side only. The space between the roof and ceiling of the minor is about 200 cubic yards; too small to move air with a gable fan according to several supply houses I’ve called. The problem may be caused by the fact that the sheathing of the major roof runs about a foot below the level of the ceiling of the minor. I had to get on all fours and stoop under the end of the sheathing before I could stand upright and enter the minor roof to add insulation. A possible solution may be (this is question) to cut the sheathing of the major roof where it meats the minor to create a large opening and permit air flow (will it?). I could always replace the sheathing if it doesn’t solve the problem. Phrased another way, by enlarging that opening at the junction where these two roofs meet, would the air flow improve (there are gable vents at all ends of both roofs) in the minor roof or would I simply disturb the air flow in the major and create an additional problem for myself? P.S. House is in Ohio. Cold winters. 200 cubic yards is a tremendous area. Are you sure about that measurement. In my opinion if the space is big enough for you to crawl through, it is big enough to pull air through. If the area that you want to cool down is really 200 cubic yards, you may want to consider installing a whole house fan as that will certainly have the capacity to move air. If you are talking about an existing gable fan, the problem may be that it is pulling air in from the nearest gable vent and any air that comes from further away gets heated by the time it gets to the other end. > Picture two roofs – a major and minor – with the minor 1/3 the size of > the major T-boning into the major at the middle on one side only. The [quoted text clipped - 27 lines] > air in from the nearest gable vent and any air that comes from further away > gets heated by the time it gets to the other end. A ridge vent would be one solution... possibly the best. However, I'm wondering if I can accomplish the same thing by simply increasing the open area at that junction of the two roofs. And by the way, the area under the minor roof is less than 200 cu.ft.. Sorry for the confusion. >>if the space is big enough for you to crawl through, it is big enough to pull air through.<< But would a larger opening increase the volume of air flowing into or out of the major roof area? And which way is the direction of the flow? I Assume right now the air flows from one gable vent to the other in the major roof ... or is it air flowing out both vents due to difference in pressure? I don't know how the air flows under the minor roof. I just know it's not flowing sufficiently to avoid a buildup of ice from time-to-time on my rain gutter on the North side. On Jul 13, 10:08 am, "John Grabowski" <jgrabo...@optonline.net> wrote: > "jaygreg" <jaygre...@hotmail.com> wrote in message > [quoted text clipped - 33 lines] > away > gets heated by the time it gets to the other end. A ridge vent would be one solution... possibly the best. However, I'm wondering if I can accomplish the same thing by simply increasing the open area at that junction of the two roofs. And by the way, the area under the minor roof is less than 200 cu.ft.. Sorry for the confusion. >>if the space is big enough for you to crawl through, it is big enough to >>pull air through.<< But would a larger opening increase the volume of air flowing into or out of the major roof area? And which way is the direction of the flow? I Assume right now the air flows from one gable vent to the other in the major roof ... or is it air flowing out both vents due to difference in pressure? I don't know how the air flows under the minor roof. I just know it's not flowing sufficiently to avoid a buildup of ice from time-to-time on my rain gutter on the North side. I'm not sure what you are trying to accomplish and what you have now. Do you have a gable fan installed right now? Are you trying to cool the house down? If your only problem is a build up of ice on your rain gutter, more air flowing into the attic will not help that. You need some heat tape for that since the north side probably doesn't get hit with any sun. A ridge vent will not provide significant cooling to your attic. It is the bare minimum required to get some air movement. If it is a cool attic that you want, a whole house fan is the way to go. If you want to bring the temperature down in the attic a few degrees and also have good air circulation, an attic ventilating fan on each roof section should work out well. If you just want a passive system you should have plenty of soffitt vents installed for air to flow naturally. Heat rises and will exit out at the highest point, but you must have make up air in order for the air to flow. > On Jul 13, 10:08 am, "John Grabowski" <jgrabo...@optonline.net> wrote: > [quoted text clipped - 72 lines] > installed for air to flow naturally. Heat rises and will exit out at the > highest point, but you must have make up air in order for the air to flow. >>If your only problem is a build up of ice on your rain gutter, more air flowing into the attic will not help that. You need some heat tape for that since the north side probably doesn't get hit with any sun. > Sorry to disagree, John, but I've been through this with a lot of different opinions. The minor roof is insulated all the way to the ridge with baffles underneath to permanent small air flow. There are no soffit vents nor do I want any unless I can't move that air at the top. If I can alter the pressure in the minor roof just enough to move air a bit more, I'll have my problem fixed. If not... I'll be forced into a ridge vent. on 7/13/2008 9:23 AM jaygreg said the following: > Picture two roofs – a major and minor – with the minor 1/3 the size of > the major T-boning into the major at the middle on one side only. The [quoted text clipped - 8 lines] > insulation. > Cut the sheathing. That will allow more hot air to enter the major roof, besides allowing easier entry. > A possible solution may be (this is question) to cut the sheathing of > the major roof where it meats the minor to create a large opening and [quoted text clipped - 7 lines] > P.S. House is in Ohio. Cold winters. > I may be confused, but how are there gable vents on both ends of the minor roof when the major roof extends into the minor roof? I have a similar roof structure and there is no way to have a vent on the minor roof since there is no gable where it meets the major roof. _______________ | Major | < gable vents both sides | |_________ | no gable >| Minor | < gable vent | | | |_____________|________|  SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ > on 7/13/2008 9:23 AM jaygreg said the following: > [quoted text clipped - 41 lines] > In Hamptonburgh, NY > To email, remove the double zeroes after @ Sorry for the confusion, Bill. The major roof has a gable vent at each end. The minor roof has one gable vent at one end but none at the other because that is the end that joins the major roof. And I tend to agree with you that the hotter air from the minor roof will escape to the area under the major roof, dissipate, and flow through the gable vents at either of the major roof. But I'm really not sure... yet. on 7/13/2008 3:20 PM jaygreg said the following: > >> on 7/13/2008 9:23 AM jaygreg said the following: [quoted text clipped - 53 lines] > vents at either of the major roof. But I'm really not sure... yet. > Ok, it is like mine then. :-) Even with gable vents, there is that hot dead air above the vents, and unless there is a breeze blowing, it will stay up there. I do have a thermostatically controlled gable vent fan in the minor roof. I made a mistake when I built the house 24 years ago. I had black roof shingles installed, and there is no rafter insulation in either attic. The lower attic is unbearable in the hot summer, even with the vent fan. The upper roof has unpowered gable vents on both ends and is less hotter than the lower attic, but the AC handler is in that attic, and even though the handler and ducts are insulated, I feel that the AC will be more efficient in a cooler attic. When I need to have the roofs reshingled, I'll get the lightest color available, and install ridge vents on both. I have two foot overhangs which have the continuously perforated vinyl soffit, so that part of the attic is adequately vented. SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ > on 7/13/2008 3:20 PM jaygreg said the following: > [quoted text clipped - 71 lines] > In Hamptonburgh, NY > To email, remove the double zeroes after @ >>dead air above the vents<< My vents are right at the peak; can't go any higher. That's why I'm fairly certain that making the opening larger at junction of the two roofs will improve air flow and move air out the tops for both roofs through their gable vents. I have two neighbors who got interested in my insulation project of that minor roof. We compared gas consumption for about two years before one the neighbors passed away. I was consuming the most at the onset. By the time I completed the project, I was beating both of them. The room immediately under that minor roof (and above my living room in a Cape Cod style home) was always too cold in the Winter and too hot in the Summer. I took two construction courses at Ohio State's Tech College in Wooster, Ohio (as a senior guest at no charge) and the teacher (a guy with a degree in physics) got interested in my project. After showing him photos of all angles and thoroughly explaining all that was involved, he concluded the solution would be to make the areas beyond the knee walls "hot areas". So I stapled insulation baffles to the roof from the bottom all the way to the ridge then placed fiberglass insulation on top held in place with wire rods made for that purpose. Bingo! I solved my temperature problem right away and my gas consumption plummeted. Of course there were other contributing factors like added insulation above the ceiling under both roofs and caulking throughout ever outside wall including utility outlets. Despite all that, the minor roof will still show heat loss over time, usually a full day after a heavy snow fall. If the snow stays several days and the temperature is very cold outside forcing higher fuel consumption, I'll get ice in one area. It's an area where the furnace duct rises to deliver heat to that room. It's also right above the kitchen which delivers more heat. I finally concluded the air simply gets trapped under that minor roof and eventually melts the snow. If the air were moved - even slightly - I suspect I'll no longer have the problem. Of course the air is moving now but obviously not enough. I'll know if I'm right soon. I'll cut the opening larger this week. I should have a feel for how effective that was by the temperature in the room without the air conditioners running. > on 7/13/2008 9:23 AM jaygreg said the following: > [quoted text clipped - 41 lines] > In Hamptonburgh, NY > To email, remove the double zeroes after @ Hi Bill. I'm the guy in Ohio that's trying to fix his ventilation problem and you offerred suggestions on the construction forum. We both have houses with a minor roof teeing into one side of a major roof. You said yours was like mine. I forgot to ask... is the openning of you minor roof fully exposed so you can see into the major roof area from the minor? Mine is not, which is the problem I feel. I'm about to cut the sheathing to creat that openning and you came to mind. I'd feel a lot more comfortable if I knew you could see through to the major roof are. I have nightmares of my house caving in on itself. :-) on 7/16/2008 2:21 PM jaygreg said the following: > >> on 7/13/2008 9:23 AM jaygreg said the following: [quoted text clipped - 58 lines] > of my house caving in on itself. :-) > No, I cannot look into either attic from the other one. There is a stairway that runs up to the second floor that is in the minor roof part of the house, but then takes a left turn and up one step into the major roof part to the second floor rooms. There is a flat ceiling at the top of the stairwell, and from the minor attic, I can reach over the top of that flat stairwell ceiling, which is just below the minor roof peak. This next part is hard to describe. I have an unconventional split level arrangement. The second floor is above the garage side of the house, so from the ground up, it is garage on ground level slab, bedrooms, then major attic. On the minor side it is, half basement below ground level, living room, dining room, kitchen on ground level floor, then minor attic. When I had the Central Air installed, I had to open up the hallway wall just above that one step left turn and run the major attic's AC handler ducts from the major attic through that newly created hole and over the stairwell ceiling in the minor attic, then into the LR, DR, and kitchen. I hope the above makes some sense to you. SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ |
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