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Ridge Vent or Box Vents?
I have heard that ridge vents only work well if there are wide soffits,
like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? |
Ridge Vent or Box Vents?
On Sun, 08 Apr 2012 17:42:42 -0400, DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Don't see how the size of the soffits would matter. The area of the vents (equivalent opening) certainly matters. While they're related they're not the same. A 12" soffit isn't all that wide though. |
Ridge Vent or Box Vents?
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Ridge Vent or Box Vents?
On Apr 8, 5:59*pm, DerbyDad03 wrote:
On 04/08/12 5:48 PM, wrote: On Sun, 08 Apr 2012 17:42:42 -0400, *wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Don't see how the size of the soffits would matter. *The area of the vents (equivalent opening) certainly matters. *While they're related they're not the same. *A 12" soffit isn't all that wide though. It is compared to my 6" soffits. 12" or more was the number that a roofing estimator used when he recommended box vents for my house. He mentioned box vents, I asked why not a ridge vent, he said my soffits are too narrow. He then went on to explain that ridge vents only work well with wide soffits, 12" or more. The principle is that hot air rises. So, you want intakes near the bottom and outlets near the top. Whether the outlets are ridge or box vents isn't going to matter. What's more important is the square footage of each. As to needing soffit vents that are greater than 12" wide, are we talking CONTINUOS soffit vents? If so, the roofer is nuts. Vents even 3 or 4" wide, run continously, are going to provide a lot of intake area. I'd go with the ridge vent. And if the soffit vents aren't big enough, then I'd enlarge them, if possible. Many cases all it takes are one of the small cordless circular saws run down the length. Plus ridge vents, IMO, look a lot better. |
Ridge Vent or Box Vents?
"DerbyDad03" wrote in message ... I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Your roofer sees a problem with using ridge vents and isn't explaining why very well. Perhaps you should talk to more roofers. If you have already hired him perhaps you could get him to elaborate. |
Ridge Vent or Box Vents?
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Ridge Vent or Box Vents?
On Apr 8, 5:42*pm, DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. It seems to me that there might be some failure to communicate here (the forum). The OP is saying (taken literally) that his SOFFITS are 6", not his soffit VENTS. That leaves very little room for vents and maybe the roofer thinks he will need fans to pull enough air through? I don't know enough to offer an opinion on whether that would be correct... |
Ridge Vent or Box Vents?
On Apr 8, 8:02*pm, Larry Fishel wrote:
On Apr 8, 5:42*pm, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. It seems to me that there might be some failure to communicate here (the forum). The OP is saying (taken literally) that his SOFFITS are 6", not his soffit VENTS. That leaves very little room for vents and maybe the roofer thinks he will need fans to pull enough air through? I don't know enough to offer an opinion on whether that would be correct... Thanks for correcting that. Even with 6" soffits, if you ran a 2 or 3 inch wide continuous soffit down it, that adds up to a lot of intake space, 24 or 36 sq inches per foot. The only reason that wouldn't work is if there were something in the construction blocking it. That something in many cases is insulation that gets shoved too far, right over the vents. To do it right, there should be plastic baffles that you can get at HD that get stapled to the underside of the sheating, at the soffits, that form an open channel for a few feet from the soffit so that air can flow. A continuous soffit vent together with a continous ridge vent, IMO is the optimal solution. The ridge vent is typically a couple inches wide. A similar size opening along the soffit and you're all set. |
Ridge Vent or Box Vents?
On Sun, 8 Apr 2012 16:29:15 -0700, "Bob F" wrote:
wrote: On Apr 8, 5:59 pm, DerbyDad03 wrote: On 04/08/12 5:48 PM, wrote: On Sun, 08 Apr 2012 17:42:42 -0400, wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Don't see how the size of the soffits would matter. The area of the vents (equivalent opening) certainly matters. While they're related they're not the same. A 12" soffit isn't all that wide though. It is compared to my 6" soffits. 12" or more was the number that a roofing estimator used when he recommended box vents for my house. He mentioned box vents, I asked why not a ridge vent, he said my soffits are too narrow. He then went on to explain that ridge vents only work well with wide soffits, 12" or more. The principle is that hot air rises. So, you want intakes near the bottom and outlets near the top. Whether the outlets are ridge or box vents isn't going to matter. What's more important is the square footage of each. As to needing soffit vents that are greater than 12" wide, are we talking CONTINUOS soffit vents? If so, the roofer is nuts. Vents even 3 or 4" wide, run continously, are going to provide a lot of intake area. I'd go with the ridge vent. And if the soffit vents aren't big enough, then I'd enlarge them, if possible. Many cases all it takes are one of the small cordless circular saws run down the length. Plus ridge vents, IMO, look a lot better. The goal should be to have free, clear venting in the soffits equal to the top vent area. I can imagine no reason for needing wide siffits for that as long as the isulation can be kept clear of the air flow space. That can be done with smaller soffits, too. My last house had 6" soffits and a ridge vent. The soffit vent was continuous, however. It wasn't the perforated aluminum that I see elsewhere, some of which only has 1/3 perforated. |
Ridge Vent or Box Vents?
DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Basic rule: You can't have too much soffit vents. At a minimum, you should have one sq ft of soffit vent for each 150 sq ft of floor space. This is one sq ft of unobstructed venting. Some screening material consumes as much as 2/3rds of the space. Refigure accordingly. If you have a 1500 sq ft house, you need 100 sq ft of soffits, minimum. Assuming the screening material is hardware cloth or similar that consumes less than 20% of the opening, you should plan on 120 sq ft of soffit venting. Further, assuming small, six inch soffits on a 50 x 30' house, you have 160 feet of perimeter. That means only 80 sq ft, maximum, for available soffit vents. Obviously this is woefully insufficient for the appropriate amount of passive ventilation. You'll have to move up a step in addition to ridge vents. Turbines are the next step and beyond that powered ventilators. |
Ridge Vent or Box Vents?
HeyBub wrote:
DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Basic rule: You can't have too much soffit vents. At a minimum, you should have one sq ft of soffit vent for each 150 sq ft of floor space. (snip) Obviously this is woefully insufficient for the appropriate amount of passive ventilation. You'll have to move up a step in addition to ridge vents. Turbines are the next step and beyond that powered ventilators. When, if ever, do you need to be concerned about having too much negative pressure in the attic? You don't want to encourage air to come up through the ceiling any more than necessary. |
Ridge Vent or Box Vents?
DerbyDad03 wrote:
He mentioned box vents, I asked why not a ridge vent, he said my soffits are too narrow. He then went on to explain that ridge vents only work well with wide soffits, 12" or more. That's a lot of horse ****. I've installed a few ridge vents, and you usually cut maybe a 6 to 8" wide gap in the decking at the very peak of a roof line (3 to 4 inches on either side). To theoretically balance out the size of that ridge opening with a similar soffit opening, then a 6" fully-perforated soffit would work. Also note that sometimes even a 2-foot-wide soffit isin't what it seems, because the bottleneck will be the gap or opening between where the deck passes over the wall header. Usually, the wider the soffit - the lower-slope the roof is, making for a not-so-large header gap. A ridge vent will give you a more even airflow pattern along the underside of the decking compared to a few box vents. |
Ridge Vent or Box Vents?
On Sunday, April 8, 2012 5:42:42 PM UTC-4, DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Huh, if your vents arent big enough they arent big enough no matter which you use. Soffit material is available that basically turns the whole soffit into a vent. Jimmie |
Ridge Vent or Box Vents?
Mike Paulsen wrote:
HeyBub wrote: DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Basic rule: You can't have too much soffit vents. At a minimum, you should have one sq ft of soffit vent for each 150 sq ft of floor space. (snip) Obviously this is woefully insufficient for the appropriate amount of passive ventilation. You'll have to move up a step in addition to ridge vents. Turbines are the next step and beyond that powered ventilators. When, if ever, do you need to be concerned about having too much negative pressure in the attic? You don't want to encourage air to come up through the ceiling any more than necessary. Excellent point! This could easily happen with aggressively powered fans and insufficient, or no, soffit vents. |
Ridge Vent or Box Vents?
On Apr 8, 9:21*pm, "HeyBub" wrote:
DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? Basic rule: You can't have too much soffit vents. At a minimum, you should have one sq ft of soffit vent for each 150 sq ft of floor space. This is one sq ft of unobstructed venting. Some screening material consumes as much as 2/3rds of the space. Refigure accordingly. If you have a 1500 sq ft house, you need 100 sq ft of soffits, minimum. Assuming the screening material is hardware cloth or similar that consumes less than 20% of the opening, you should plan on 120 sq ft of soffit venting. Further, assuming small, six inch soffits on a 50 x 30' house, you have 160 feet of perimeter. That means only 80 sq ft, maximum, for available soffit vents. Obviously this is woefully insufficient for the appropriate amount of passive ventilation. There is an error in your math. Assuming you need one sq ft of venting per 100 sq ft of floor space, then a 1500 sq ft house needs 15 sq ft of venting, not 150. You're off by a factor of 10. Following through with the math, you'd then want 12 sq ft actual. If you did 2" wide vents, you get .16 sq ft per linear foot. Which in turn means those 2" wide vents down just the long sides of the house would give you 16 sq ft total, meeting the min reqt. Also, technically, it's not floor space that counts, but the attic area that is being vented. Some houses don't have just one open continous attic area. You'll have to move up a step in addition to ridge vents. Turbines are the next step and beyond that powered ventilators. Not when you redo the math. |
Ridge Vent or Box Vents?
HeyBub wrote:
When, if ever, do you need to be concerned about having too much negative pressure in the attic? What do you klowns think is happening? You think there is some big vacuum cleaner sitting on your roof, sucking air through your ceiling just because you have too much venting? Excellent point! Stupid point! This could easily happen with aggressively powered fans and insufficient, or no, soffit vents. What are the odds that someone is going to have powered roof fans *and no* soffit vents? And think about this: Even IF you are somehow creating a negative pressure in the attic that IS pulling air through the ceiling - SO WHAT? This is going to be happening ONLY IN THE SUMMER. ITS NO BIG DEAL IF IT HAPPENS IN THE SUMMER. It's in the winter when you don't want that to happen, and who's going to turn on their roof fans in the winter ???? |
Ridge Vent or Box Vents?
On Apr 9, 8:41*am, Home Guy wrote:
HeyBub wrote: When, if ever, do you need to be concerned about having too much negative pressure in the attic? What do you klowns think is happening? You think there is some big vacuum cleaner sitting on your roof, sucking air through your ceiling just because you have too much venting? Excellent point! Stupid point! This could easily happen with aggressively powered fans and insufficient, or no, soffit vents. What are the odds that someone is going to have powered roof fans *and no* soffit vents? And think about this: *Even IF you are somehow creating a negative pressure in the attic that IS pulling air through the ceiling - SO WHAT? *This is going to be happening ONLY IN THE SUMMER. *ITS NO BIG DEAL IF IT HAPPENS IN THE SUMMER. *It's in the winter when you don't want that to happen, and who's going to turn on their roof fans in the winter ???? in the summer with AC sucking cooled air from the air conditioned space is a poor choice, but at the same time its when having a cool attic is most important.... beyond which sucking on the living part of the home will create paths for the air from the living area to follow all the time..... a real lose lose kinda situation. roof fans in the winter help keep the humidity low in the attic which helps prevent mold growth |
Ridge Vent or Box Vents?
bob haller wrote:
in the summer with AC sucking cooled air from the air conditioned space is a poor choice, but at the same time its when having a cool attic is most important.... beyond which sucking on the living part of the home will create paths for the air from the living area to follow all the time... In the summer, if I had a choice between: a) pulling 1000 cfm of air out of my attic using powered vents - with 950 cfm coming from the soffits (and/or gable-end vents) and 50 cfm coming from ceiling leaks - or b) having NO powered vents (only passive vents) and therefore only getting 200 cfm of passive air movement out of the attic (and 0 cfm from ceiling air leaks) - It's a no -brainer which one is better for the house and the roof. And if I can pull more than 50 cfm from ceiling leaks, then the answer is NOT to turn off the fans. The answer is to fix the ceiling leaks (or just live with them) - not sacrifice the life of the shingles by letting attic temperatures soar. roof fans in the winter help keep the humidity low in the attic which helps prevent mold growth I would bet that the vast majority of roof fans don't have humidity sensors - only thermostats (which means they only come on in the summer). I know the theory of ventilating the attic in the winter to prevent mold, but explain to me how discharging cold, humid air from the attic and replacing it with cold, humid air from the outside is going to change anything. If the air in the attic is more humid than outside air in the winter, it's because you have ceiling air leaks (or you're venting bathroom and kitchen exhaust fans directly into the attic). It's a no-brainer that you fix those situations first, eliminating the need for winter attic ventilation in the first place. |
Ridge Vent or Box Vents?
Home Guy wrote:
bob haller wrote: in the summer with AC sucking cooled air from the air conditioned space is a poor choice, but at the same time its when having a cool attic is most important.... beyond which sucking on the living part of the home will create paths for the air from the living area to follow all the time... In the summer, if I had a choice between: a) pulling 1000 cfm of air out of my attic using powered vents - with 950 cfm coming from the soffits (and/or gable-end vents) and 50 cfm coming from ceiling leaks - or b) having NO powered vents (only passive vents) and therefore only getting 200 cfm of passive air movement out of the attic (and 0 cfm from ceiling air leaks) - It's a no -brainer which one is better for the house and the roof. As long as you don't care what it costs to run the A/C. Trying to cool an extra 50 cfm of exterior air continuously is going to COST. |
Ridge Vent or Box Vents?
Bob F wrote:
In the summer, if I had a choice between: a) pulling 1000 cfm of air out of my attic using powered vents - with 950 cfm coming from the soffits (and/or gable-end vents) and 50 cfm coming from ceiling leaks - or b) having NO powered vents (only passive vents) and therefore only getting 200 cfm of passive air movement out of the attic (and 0 cfm from ceiling air leaks) - It's a no -brainer which one is better for the house and the roof. As long as you don't care what it costs to run the A/C. Trying to cool an extra 50 cfm of exterior air continuously is going to COST. That cost might be more than offset by the heat load I'm taking away from the interior ceiling area by ventilating the attic with 950 cfm of outside air vs 200 cfm of passive air. Numbers like 1000, 200 and 50 (cfm) are all just hypothetical, but I still assert that interior air leaks into the attic are trivial (for any home built in the last 50 years) - not counting any bad practices like venting bathroom or kitchen fans into the attic. |
Ridge Vent or Box Vents?
On 4/8/2012 4:42 PM, DerbyDad03 wrote:
I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Weird |
Ridge Vent or Box Vents?
|
Ridge Vent or Box Vents?
gonjah wrote:
On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Box vents are way easier to install neatly than soffit vents. |
Ridge Vent or Box Vents?
On 4/9/2012 6:51 PM, Bob F wrote:
gonjah wrote: On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Box vents are way easier to install neatly than soffit vents. So you're saying ignore the problem with the fact there isn't enough total attic airflow? Sorry, I'm a bit new to pitched roofs. |
Ridge Vent or Box Vents?
On 04/09/12 11:24 AM, Home Guy wrote:
Bob F wrote: In the summer, if I had a choice between: a) pulling 1000 cfm of air out of my attic using powered vents - with 950 cfm coming from the soffits (and/or gable-end vents) and 50 cfm coming from ceiling leaks - or b) having NO powered vents (only passive vents) and therefore only getting 200 cfm of passive air movement out of the attic (and 0 cfm from ceiling air leaks) - It's a no -brainer which one is better for the house and the roof. As long as you don't care what it costs to run the A/C. Trying to cool an extra 50 cfm of exterior air continuously is going to COST. That cost might be more than offset by the heat load I'm taking away from the interior ceiling area by ventilating the attic with 950 cfm of outside air vs 200 cfm of passive air. Numbers like 1000, 200 and 50 (cfm) are all just hypothetical, but I still assert that interior air leaks into the attic are trivial (for any home built in the last 50 years) - not counting any bad practices like venting bathroom or kitchen fans into the attic. House was built 56 years ago. There's a pull-down attic staircase in the hallway. |
Ridge Vent or Box Vents?
On 04/09/12 7:51 PM, Bob F wrote:
gonjah wrote: On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Box vents are way easier to install neatly than soffit vents. The discussion isn't about box vents vs. soffit vents, it's about box vents vs. a ridge vent. There are currently no soffit vents now, just 3 gable end vents and 4 box vents (there's 2 sections of roof) The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. ROOF VENTS Install six (6) Lomanco Model 750 aluminum slant back box vents in roof just below ridge line of roof in color selected by client. (That would be 4 on the big section of roof and 2 on the smaller section) |
Ridge Vent or Box Vents?
On 04/09/12 11:51 AM, gonjah wrote:
On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Weird It's a given that I need more intake. There are currently no soffit vents now, just 3 gable end vents and 4 box vents (there's 2 sections of roof) The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. ROOF VENTS Install six (6) Lomanco Model 750 aluminum slant back box vents in roof just below ridge line of roof in color selected by client. (That would be 4 on the big section of roof and 2 on the smaller section) |
Ridge Vent or Box Vents?
DerbyDad03 wrote:
The discussion isn't about box vents vs. soffit vents, it's about box vents vs. a ridge vent. If you ask me, box vents are more fussy to install (and shingle around) vs ridge vents, and they don't give you as much ventilation area as you think. In your case, the box vents you're being quoted for actually have a circular opening of about 8" diameter (on the bottom) and the perforated area on the outer side may not add up to a whole lot of actual ventilation area. http://www.lomanco.com/index.php/ven...tic-roof-vents Your vents have a specified ventilation opening or area of 50 square inches. Every running foot of ridge venting will give you between about 24 quare inches ventilation (about an inch worth on two sides) and be faster to install - but I don't know about the cost of ridge venting. Your aluminum Lorenco vents come in a box of 6, and can be had for as little as $20 for a box if this ebay vendor is any example: http://www.ebay.com/itm/140627349384 Bottom line is that a ridge vent is very easy to install, and gives more ventilation capability and more even ventilation than box vents. However, be aware of this: Summer is notorious for having hot days WITH LITTLE OR NO WIND. Any passive vent system really needs a good wind to help ventilate your roof. So you might (or should) consider not having too much passive venting AND have some power vent fans. Going with the lightest-colored shingles you can manage is also better than dark shingles. |
Ridge Vent or Box Vents?
DerbyDad03 wrote:
The discussion isn't about box vents vs. soffit vents, it's about box vents vs. a ridge vent. If you ask me, box vents are more fussy to install (and shingle around) vs ridge vents, and they don't give you as much ventilation area as you think. In your case, the box vents you're being quoted for actually have a circular opening of about 8" diameter (on the bottom) and the perforated area on the outer side may not add up to a whole lot of actual ventilation area. http://www.lomanco.com/index.php/ven...tic-roof-vents Your vents have a specified ventilation opening or area of 50 square inches. Every running foot of ridge venting will give you between about 24 quare inches ventilation (about an inch worth on two sides) and be faster to install - but I don't know about the cost of ridge venting. Your aluminum Lorenco vents come in a box of 6, and can be had for as little as $20 for a box if this ebay vendor is any example: http://www.ebay .com/itm/140627349384 Bottom line is that a ridge vent is very easy to install, and gives more ventilation capability and more even ventilation than box vents. However, be aware of this: Summer is notorious for having hot days WITH LITTLE OR NO WIND. Any passive vent system really needs a good wind to help ventilate your roof. So you might (or should) consider not having too much passive venting AND have some power vent fans. Going with the lightest-colored shingles you can manage is also better than dark shingles. |
Ridge Vent or Box Vents?
On 4/9/2012 7:23 PM, DerbyDad03 wrote:
On 04/09/12 11:51 AM, gonjah wrote: On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Weird It's a given that I need more intake. There are currently no soffit vents now, just 3 gable end vents and 4 box vents (there's 2 sections of roof) The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. ROOF VENTS Install six (6) Lomanco Model 750 aluminum slant back box vents in roof just below ridge line of roof in color selected by client. (That would be 4 on the big section of roof and 2 on the smaller section) I'm wondering why he prefers boxes? I had my ridge vent installed when they tore off the old shingles. Maybe it's easier then? |
Ridge Vent or Box Vents?
On 4/9/2012 8:02 PM, Home Guy wrote:
DerbyDad03 wrote: The discussion isn't about box vents vs. soffit vents, it's about box vents vs. a ridge vent. If you ask me, box vents are more fussy to install (and shingle around) vs ridge vents, and they don't give you as much ventilation area as you think. In your case, the box vents you're being quoted for actually have a circular opening of about 8" diameter (on the bottom) and the perforated area on the outer side may not add up to a whole lot of actual ventilation area. http://www.lomanco.com/index.php/ven...tic-roof-vents Your vents have a specified ventilation opening or area of 50 square inches. Every running foot of ridge venting will give you between about 24 quare inches ventilation (about an inch worth on two sides) and be faster to install - but I don't know about the cost of ridge venting. Your aluminum Lorenco vents come in a box of 6, and can be had for as little as $20 for a box if this ebay vendor is any example: http://www.ebay.com/itm/140627349384 Bottom line is that a ridge vent is very easy to install, and gives more ventilation capability and more even ventilation than box vents. However, be aware of this: Summer is notorious for having hot days WITH LITTLE OR NO WIND. Any passive vent system really needs a good wind to help ventilate your roof. So you might (or should) consider not having too much passive venting AND have some power vent fans. Going with the lightest-colored shingles you can manage is also better than dark shingles. Should I still be using my attic fan during still periods? I thought they were not cost effective. I have a 1500 sf house. How many sf should I have in soffit vents? Jim |
Ridge Vent or Box Vents?
The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. Nowadays 16" or more attic insulation is required by code. It may be difficult to prevent the insulation from blocking the air flow from soffit vents. If you install baffles to hold the insulation back you may be putting a flow of cold air next to your ceiling. A cold spot on your ceiling allows mold to grow. Might be better to install roof vents just above the insulation at the bottom of the roof and again at the top. When you have continuous venting at the soffit and ridge the venting can be reduced by 50%. Since you do not have continuous soffit venting a ridge vent may be undersized by 50%. |
Ridge Vent or Box Vents?
gonjah wrote:
Should I still be using my attic fan during still periods? I thought they were not cost effective. I try to not have my attic temperature exceed 100 degrees F. So I'll turn on my attic fan when-ever the temp hits 100, wind or no wind. I have a 1500 sf house. How many sf should I have in soffit vents? You should have a soffit vent hole between every rafter joist. If you have aluminum soffit, there's no excuse for not having perforated aluminum soffit along the entire length of the eves. If you have mostly (or totally) solid aluminum soffit, take it all down and replace with 100% perforated soffit: http://www.biytoday.com/Soffit2.jpg Just cut a hole the size of your hand with a jig saw in the existing plywood soffit every 16" before you install the perforated soffit. And remember that anything you do to improve soffit ventilation is wasted if you have attic insulation jammed into the eves blocking air flow. |
Ridge Vent or Box Vents?
On 4/9/2012 10:29 PM, Home Guy wrote:
gonjah wrote: Should I still be using my attic fan during still periods? I thought they were not cost effective. I try to not have my attic temperature exceed 100 degrees F. So I'll turn on my attic fan when-ever the temp hits 100, wind or no wind. I have one of those fans that blows out the vent under the gable. I think that's the right term. Wouldn't it just pull right from the ridge vent directly above it making it practically useless? BTW: We had 42 days of +100 degrees last year. All time record. I have a 1500 sf house. How many sf should I have in soffit vent You should have a soffit vent hole between every rafter joist. If you have aluminum soffit, there's no excuse for not having perforated aluminum soffit along the entire length of the eves. If you have mostly (or totally) solid aluminum soffit, take it all down and replace with 100% perforated soffit: http://www.biytoday.com/Soffit2.jpg Just cut a hole the size of your hand with a jig saw in the existing plywood soffit every 16" before you install the perforated soffit. And remember that anything you do to improve soffit ventilation is wasted if you have attic insulation jammed into the eves blocking air flow.e to Not good. It's ply-board and the vents (about 6" x 12") are a good 5' apart. Replacing some of the ply-board will be difficult. |
Ridge Vent or Box Vents?
On 4/9/2012 7:23 PM, DerbyDad03 wrote:
On 04/09/12 11:51 AM, gonjah wrote: On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Weird It's a given that I need more intake. There are currently no soffit vents now, just 3 gable end vents and 4 box vents (there's 2 sections of roof) The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. ROOF VENTS Install six (6) Lomanco Model 750 aluminum slant back box vents in roof just below ridge line of roof in color selected by client. (That would be 4 on the big section of roof and 2 on the smaller section) Pat: How much are you being charged per vent? What is the soffit made of? |
Ridge Vent or Box Vents?
On 4/9/2012 10:47 PM, gonjah wrote:
On 4/9/2012 7:23 PM, DerbyDad03 wrote: On 04/09/12 11:51 AM, gonjah wrote: On 4/8/2012 4:42 PM, DerbyDad03 wrote: I have heard that ridge vents only work well if there are wide soffits, like 12" or more. On houses with narrow soffits, box vents are recommended. Any truth to this? I'd ask why? Seems to make no sense to me. Sounds like he's saying you need larger intake vents regardless and he likes box vents. Maybe that's all he knows how to install? Weird It's a given that I need more intake. There are currently no soffit vents now, just 3 gable end vents and 4 box vents (there's 2 sections of roof) The estimate includes: SOFFIT VENTS Install ten (10), 6" x 16" size, in client selected color screened soffit vents in overhangs. ROOF VENTS Install six (6) Lomanco Model 750 aluminum slant back box vents in roof just below ridge line of roof in color selected by client. (That would be 4 on the big section of roof and 2 on the smaller section) Pat: How much are you being charged per vent? What is the soffit made of? Oops! Make that DerbyDad. |
Ridge Vent or Box Vents?
gonjah wrote:
Should I still be using my attic fan during still periods? I thought they were not cost effective. I have a 1500 sf house. How many sf should I have in soffit vents? According to my corrected calculations, you need one sq ft of soffit vents per 150 sq ft of floor space, or 10 sq ft. This is ten UNRESTRICTED sq ft. Some of the screening on soffit vents take up a considerable amount of space, so figure on 20-50% more actual venting. Looking at the commercially available vent covers, I decided to make my own. Here's what I did. 1. I got a roll of gutter screening. Plastic, 6"wide. Actually, several rolls. 2. Using 1/2 x 2 furring strips, I constructed a number of 4' long frames to hold the screening. A pneumatic staple gun is a great labor-saver here. 3. After trying all manner of saws, I ended up using a pruning chain saw(!) to cut the 5" by 4' sections out of my 1/4" plywood soffits. 4. I installed the aforementioned frames with sheet metal screws. The soffit screens were painted before installation*. 5. I installed a LOT of these home-made soffit screens. The perimeter of my house is about 200'. At least 100' of that contains soffit vents. That works out to 2.5 times the recommended minimum. Of course I live in a hot, humid, town (Houston), so my needs may greatly exceed yours. -------- * Before painting my house the last time, I investigated the available colors of spray paint available at the box store. I found one that was acceptable ("Camouflage") and bought several cans. I then painted the tip of a wood paint stir-stick with the spray paint and asked the paint department to match the color with several gallons of exterior paint. Now, when a bit of the house needs a touch-up, I spray it. Anyway, the spray cans came in handy when painting the soffit screens... |
Ridge Vent or Box Vents?
gonjah wrote:
So I'll turn on my attic fan when-ever the (attic) temp hits 100, wind or no wind. I have one of those fans that blows out the vent under the gable. I think that's the right term. You mean you have a fan like this: http://woodheatstoves.com/images/solarstar_gable.jpg Wouldn't it just pull right from the ridge vent directly above it making it practically useless? Yes - that's the problem someone could have if they have a lot of passive roof venting near the fan. I don't have ridge vents on my house (I don't have enough of a ridge line to make it worth while). BTW: We had 42 days of +100 degrees last year. All time record. Yea, that's a killer for shingles. Not good. It's ply-board and the vents (about 6" x 12") are a good 5' apart. Replacing some of the ply-board will be difficult. So you don't already have aluminum-clad soffits then... ? |
Ridge Vent or Box Vents?
On 4/10/2012 7:45 AM, Home Guy wrote:
gonjah wrote: So I'll turn on my attic fan when-ever the (attic) temp hits 100, wind or no wind. I have one of those fans that blows out the vent under the gable. I think that's the right term. You mean you have a fan like this: http://woodheatstoves.com/images/solarstar_gable.jpg Yup. It's unplugged and will probably stay that way. Wouldn't it just pull right from the ridge vent directly above it making it practically useless? Yes - that's the problem someone could have if they have a lot of passive roof venting near the fan. I don't have ridge vents on my house (I don't have enough of a ridge line to make it worth while). BTW: We had 42 days of +100 degrees last year. All time record. Yea, that's a killer for shingles. Not good. It's ply-board and the vents (about 6" x 12") are a good 5' apart. Replacing some of the ply-board will be difficult. So you don't already have aluminum-clad soffits then... ? Looks like this w/o all the dirt http://www.radiantbarrierguru.com/wp...offit-vent.jpg |
Ridge Vent or Box Vents?
HeyBub wrote:
I have a 1500 sf house. How many sf should I have in soffit vents? According to my corrected calculations, (...) I think it's a complete waste of time to mess around with calculations for roof venting that is probably based on ad-hoc forumulas to begin with. Rule #1 for roofs/attics is that you can't have too much ventilation. Beyond that, assuming that you have eves in the first place, any logically-designed roof and eve system will have an eve vent-hole located between every roof joist (assuming the eves were originally finished with plywood on their underside instead of aluminum). Now it's probably the case for new construction (new = anything younger than 20 years) that the eves were not finished with solid plywood but instead were simply clad in aluminum - and if so it should have been 100% perforated aluminum. |
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