baffle distance
#1
05-07-14, 07:24 AM
baffle distance
All the pictures I see of baffles shows them "in between" the roof rafters with one to two inches of air space between the baffle and the roof sheathing. Is there any reason why I can't do it like this (as it is easier for me). There is 7 inches between the roof sheathing and the baffle. Doesnt that "allow" a nice flow of air from the soffit to the attic. I will air seal where needed, then put back the fiberglass that was there and then blow in about 8-10 inches of cellulose. Is this Ok??
#2
05-07-14, 09:40 AM
The primary drawback that I see is the depth of insulation on top of the outside wall. Infrared pictures on the inside of most homes will show that area to be cold. I realize it would be more work but there would be benefits.
2" is considered plenty of space once you air seal and have lots of insulation. I'm assuming a continuous soffit vent and plenty of high venting, ridge, gable, or both.
Your approach is also blocking "wind washing" which keeps that air out of the end of the insulation (good).
Not sure what that flex duct is. I'm thinking rigid duct buried in insulation vented out the side, if that is a bath vent.
Bud
2" is considered plenty of space once you air seal and have lots of insulation. I'm assuming a continuous soffit vent and plenty of high venting, ridge, gable, or both.
Your approach is also blocking "wind washing" which keeps that air out of the end of the insulation (good).
Not sure what that flex duct is. I'm thinking rigid duct buried in insulation vented out the side, if that is a bath vent.
Bud
#3
05-07-14, 03:06 PM
Thanks Bud. You've lost me on your first sentence. Not sure what that means.
"" I realize it would be more work but there would be benefits"" (more work to do what??. there is one "outside wall " up there where the gable is and the 2 sides of the roof. A little lost on what you're talking about?
Read more: http://www.doityourself.com/forum/ne...#ixzz314ObQ400
your Sentence 2....You say 2" is plenty but as I say, this way (as shown) is 7 inches. Is that too much?? Is that OK .. Does that create a problem?? ( It's easier for me doing it that way for two reasons....easier for me to reach and I already did it that way) There is a gable vent only.
your Sentence 3...??wind washing?? but you say "good" so That's good.
your sentence 4.. bath fan Duct (originally just laying in the sofit) will be replaced with insulated duct and run thru the roof ( after I do my research on how to do that)
Thank you
"" I realize it would be more work but there would be benefits"" (more work to do what??. there is one "outside wall " up there where the gable is and the 2 sides of the roof. A little lost on what you're talking about?
Read more: http://www.doityourself.com/forum/ne...#ixzz314ObQ400
your Sentence 2....You say 2" is plenty but as I say, this way (as shown) is 7 inches. Is that too much?? Is that OK .. Does that create a problem?? ( It's easier for me doing it that way for two reasons....easier for me to reach and I already did it that way) There is a gable vent only.
your Sentence 3...??wind washing?? but you say "good" so That's good.
your sentence 4.. bath fan Duct (originally just laying in the sofit) will be replaced with insulated duct and run thru the roof ( after I do my research on how to do that)
Thank you
#4
05-07-14, 06:28 PM
The link below illustrates a cross section of a roof/wall/soffit similar to yours. Note the two 2x4's at the top of the wall. If you bring your rigid insulation down to the top of the wall there will be little or no insulation above those 2- 2x4's. That corner will average about r-2, cold.
If you used traditional baffles they would extend into the soffit and the space below them (above the wall) would be stuffed with batt insulation to provide r-value and prevent the blown-in insulation from filling the soffit. Even better would be a wind washing baffle at the end of the insulation to prevent wind from blowing right through the insulation.
What you have done is the easy approach. Detailing that rigid to fit between the rafters with a wind block at the bottom would be a lot more work.
2" of vent space in plenty, but nothing bad about 7" except it reduces the amount of insulation you can fit into that limited space.
As illustrated the wind would not be blowing on the new insulation, so in a sense that is good, but there should be more insulation and then you need the wind block. That link illustrates wind washing.
I hope I did better that time
.
Bud
http://inspectapedia.com/interiors/1328s.jpg
If you used traditional baffles they would extend into the soffit and the space below them (above the wall) would be stuffed with batt insulation to provide r-value and prevent the blown-in insulation from filling the soffit. Even better would be a wind washing baffle at the end of the insulation to prevent wind from blowing right through the insulation.
What you have done is the easy approach. Detailing that rigid to fit between the rafters with a wind block at the bottom would be a lot more work.
2" of vent space in plenty, but nothing bad about 7" except it reduces the amount of insulation you can fit into that limited space.
As illustrated the wind would not be blowing on the new insulation, so in a sense that is good, but there should be more insulation and then you need the wind block. That link illustrates wind washing.
I hope I did better that time
.Bud
http://inspectapedia.com/interiors/1328s.jpg
#5
05-08-14, 04:02 AM
You did better.Thanks
. Sooooooo if I cut "my" baffles to fit between the roof rafters and basically just push them ""deeper"" into the sofit ( just enough to cover that 2x4, then that would be much better). This is what I'm interpreting,,,, Yes???
Also, all I have is the sofits and a gable vent, . It's not a continuous soffit vent so I will be adding little round vents to be placed along the soffit.
I was thinking about putting at the ceiling of the attic either an additional air vent (or 2)..... "or" possible a vent with that revolving portion that gets air "INTO" (* I'm assuming it brings air "into" as why else would it have a revolving top)
......"or" a small solar powered exhaust vent. Butttt, I was reading about the in and out should be balanced .. If I put additional vents at the ceiling of the attic, could I be doing more harm than good. Thanks for your help
. Sooooooo if I cut "my" baffles to fit between the roof rafters and basically just push them ""deeper"" into the sofit ( just enough to cover that 2x4, then that would be much better). This is what I'm interpreting,,,, Yes???
Also, all I have is the sofits and a gable vent, . It's not a continuous soffit vent so I will be adding little round vents to be placed along the soffit.
I was thinking about putting at the ceiling of the attic either an additional air vent (or 2)..... "or" possible a vent with that revolving portion that gets air "INTO" (* I'm assuming it brings air "into" as why else would it have a revolving top)
......"or" a small solar powered exhaust vent. Butttt, I was reading about the in and out should be balanced .. If I put additional vents at the ceiling of the attic, could I be doing more harm than good. Thanks for your help
#6
05-08-14, 07:31 AM
When they fit the rigid between the rafters they cut a strip of foam to place on each side to prevent the foam from being pushed all the way up against the bottom of the roof (spacers).
Total vent area (net free area) is roughly 1 sq ft for every 150 sq ft of attic floor. Half that if you have a very good air seal between the house and attic along with a vapor barrier at the ceiling. Note "net free area". each type of vent will have a rating and from memory those little round pop-in vents are among the lowest. 19% as I recall for one I searched. Typically I use 75% for most others but best to check something similar.
"a vent with that revolving portion" is called a turbine vent and they are used up high for exhaust purposes. A ridge vent would be best or additional gable vent if there is another location. Passive roof vents can also be used.
Balanced venting is not something to get too precise with as long as you have a total near their recommendation. Venting is calculated for a worst case of no wind, where just natural draft pushes the warm air out. But when the wind is at work, the location of the vents is less important as the wind will drive right through the attic.
Air sealing is important to keep your conditioned air inside your home.
Bud
Total vent area (net free area) is roughly 1 sq ft for every 150 sq ft of attic floor. Half that if you have a very good air seal between the house and attic along with a vapor barrier at the ceiling. Note "net free area". each type of vent will have a rating and from memory those little round pop-in vents are among the lowest. 19% as I recall for one I searched. Typically I use 75% for most others but best to check something similar.
"a vent with that revolving portion" is called a turbine vent and they are used up high for exhaust purposes. A ridge vent would be best or additional gable vent if there is another location. Passive roof vents can also be used.
Balanced venting is not something to get too precise with as long as you have a total near their recommendation. Venting is calculated for a worst case of no wind, where just natural draft pushes the warm air out. But when the wind is at work, the location of the vents is less important as the wind will drive right through the attic.
Air sealing is important to keep your conditioned air inside your home.
Bud
