Improving Attic Ventilation in less-than perfect remodel
#1
08-08-02, 11:37 AM
Improving Attic Ventilation in less-than perfect remodel
The house I've recently purchased has a finished attic space, basically a large bedroom with two closets and a half-bath. Looks like it was done 10-12 years ago. Home was built in 1948 and faces west.
We've had several >100 degree heat index days here in Indiana, and it's a little warmer than I'd like to be. It's managable, but I'd like to improve it a bit. I'll spill everything I know about the attic in the hope that some easy-to-do priority projects surface.
Attic Space -- Everything outside of the 54" Kneewalls and the peak of the roof (maybe 24" down from the peak tops). I have access ports to the Kneewall parts of the attic, but not the upper space.
Insulation -- Looks like R-19 (yeah, I'd prefer R-38) on the kneewalls. About 18-24" of blown-in on the floor. The insulation on the kneewalls goes up to where it meets the roof, I don't see any baffles or anything to suggest that air easily flows from the lower attic space to the upper.
Venting -- Looked around and found NO soffit vents. They could be installed at the east and west sides, not on the gable ends on the north and south. They'd have to be protected from the blown-in insulation. Two gable vents and two roof vents all are connected to the upper attic space, I don't think they recieve much air from the lower/kneewall attic space.
Windows -- two wooden and one aluminum, all on the gable ends. No skylights.
HVAC -- small duct and return doesn't give me much central air, but a previous owner installed a window unit which cools the room in 10-15 minutes.
Air leakage is probably happening near recepticles, lightswitches, and the attic access ports.
With no soffit vents, inadequate insulation and attic air circulation, it's really not that bad up there due to the near complete shading from a few maple trees. But I'd like to improve it a little, and I'd like to start with the easiest projects. My questions are:
1) How much can I benefit from reducing air leakage?
2) How could I properly install soffit vents and ensure they function?
3) Could I benefit from a radiant or radience barrier?
4) Should I remove the blown-in insulation if I plan to spend a lot of time crawling around behind the kneewalls?
Any and all opinions will be appreciated
We've had several >100 degree heat index days here in Indiana, and it's a little warmer than I'd like to be. It's managable, but I'd like to improve it a bit. I'll spill everything I know about the attic in the hope that some easy-to-do priority projects surface.
Attic Space -- Everything outside of the 54" Kneewalls and the peak of the roof (maybe 24" down from the peak tops). I have access ports to the Kneewall parts of the attic, but not the upper space.
Insulation -- Looks like R-19 (yeah, I'd prefer R-38) on the kneewalls. About 18-24" of blown-in on the floor. The insulation on the kneewalls goes up to where it meets the roof, I don't see any baffles or anything to suggest that air easily flows from the lower attic space to the upper.
Venting -- Looked around and found NO soffit vents. They could be installed at the east and west sides, not on the gable ends on the north and south. They'd have to be protected from the blown-in insulation. Two gable vents and two roof vents all are connected to the upper attic space, I don't think they recieve much air from the lower/kneewall attic space.
Windows -- two wooden and one aluminum, all on the gable ends. No skylights.
HVAC -- small duct and return doesn't give me much central air, but a previous owner installed a window unit which cools the room in 10-15 minutes.
Air leakage is probably happening near recepticles, lightswitches, and the attic access ports.
With no soffit vents, inadequate insulation and attic air circulation, it's really not that bad up there due to the near complete shading from a few maple trees. But I'd like to improve it a little, and I'd like to start with the easiest projects. My questions are:
1) How much can I benefit from reducing air leakage?
2) How could I properly install soffit vents and ensure they function?
3) Could I benefit from a radiant or radience barrier?
4) Should I remove the blown-in insulation if I plan to spend a lot of time crawling around behind the kneewalls?
Any and all opinions will be appreciated
#3
08-08-02, 07:13 PM
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Attic Ventilation Issues
mrchris,
Hopefully these sites will explain alot more than I could here, take a look and it should help you resolve your issues.
http://nrha.web-pros.com/Ace_Learnin.../atticvent.htm
http://www.oikos.com/esb/30/atticvent.html
http://doityourself.com/attic/insatticvenilate.htm
http://www.findarticles.com/cf_fmhym...0_50/67151514/
p1/article.jhtml?term=
Let us know how it's coming!
Hopefully these sites will explain alot more than I could here, take a look and it should help you resolve your issues.
http://nrha.web-pros.com/Ace_Learnin.../atticvent.htm
http://www.oikos.com/esb/30/atticvent.html
http://doityourself.com/attic/insatticvenilate.htm
http://www.findarticles.com/cf_fmhym...0_50/67151514/
p1/article.jhtml?term=
Let us know how it's coming!
#4
08-09-02, 06:30 AM
All the articles seem to stress that I need soffit vents. I think the best way I can get 'em in is to cut open the soffit, let some blown-in insulation fall on my head, slide up a baffle in the hole (it'll need to be about 2' long)
They won't be super effective due to the partially blocked flow where the kneewalls meet the roofline, but it's not airtight and should improve things a lot.
They won't be super effective due to the partially blocked flow where the kneewalls meet the roofline, but it's not airtight and should improve things a lot.
#6
08-09-02, 07:01 AM
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Improving Attic Ventilation in less-than perfect remodel
mrchris,
You don't need 30 grand and the cost to do these installations is not great. Cheer up...things could be worse!
Since you mentioned about the access ports in the space available behind the kneewalls upstairs, you should be able to get in there and install air baffles, yes it is tight but it can be done. Have any small children? Just don't put a hole in the ceiling - use some plywood or planks to spread across the ceiling joists.
Option: Air baffles come in cardboard or styrofoam. You could use round cardboard mailing tubes and insert these through holes that you cut for the soffit vents, depending on the distance from soffit line to top of your plates. if you can get 2" or 3" tubes, you may be able to push this into the cavity between plate and roof sheathing. It is possible for the money to even consider cutting PVC pipe (it's cheaper than tubes) - 2" and make the tubes about 16" long, and use 2 per cavity or every 4 feet. Basically placing the tubes or baffles directly at the soffit vent location. This would eliminate some headaches working within the attic space.
It is true that some insulation may drop on your head so wear goggles and an air mask, long sleeve shirt. The holes you need to make would only be that of the vent size used.
Regading the space between the top of the kneewall and rafters, there should be space there as well too install baffles. I assume that this attic space on the lower part is unfinished.
Believe me, the improvements to air flow will be great and this will help lower some bills!
Hope this makes you feel better!
You don't need 30 grand and the cost to do these installations is not great. Cheer up...things could be worse!
Since you mentioned about the access ports in the space available behind the kneewalls upstairs, you should be able to get in there and install air baffles, yes it is tight but it can be done. Have any small children? Just don't put a hole in the ceiling - use some plywood or planks to spread across the ceiling joists.
Option: Air baffles come in cardboard or styrofoam. You could use round cardboard mailing tubes and insert these through holes that you cut for the soffit vents, depending on the distance from soffit line to top of your plates. if you can get 2" or 3" tubes, you may be able to push this into the cavity between plate and roof sheathing. It is possible for the money to even consider cutting PVC pipe (it's cheaper than tubes) - 2" and make the tubes about 16" long, and use 2 per cavity or every 4 feet. Basically placing the tubes or baffles directly at the soffit vent location. This would eliminate some headaches working within the attic space.
It is true that some insulation may drop on your head so wear goggles and an air mask, long sleeve shirt. The holes you need to make would only be that of the vent size used.
Regading the space between the top of the kneewall and rafters, there should be space there as well too install baffles. I assume that this attic space on the lower part is unfinished.
Believe me, the improvements to air flow will be great and this will help lower some bills!
Hope this makes you feel better!
#7
08-09-02, 07:15 AM
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attic ventilation
mrchris,
By the way, based on the age of the home, you may have to knock out some blocking at the plate line to insert baffles/tubes. If you're lucky, you may not have any.
When you insert the tubes from the outside, you may have to take a broom handle or a rubber hose and clear any insulation that might obstruct the air flow inside the tube.
Good luck!
By the way, based on the age of the home, you may have to knock out some blocking at the plate line to insert baffles/tubes. If you're lucky, you may not have any.
When you insert the tubes from the outside, you may have to take a broom handle or a rubber hose and clear any insulation that might obstruct the air flow inside the tube.
Good luck!
#8
08-09-02, 07:35 AM
Gotta love these old homes
55 years, probably has never had a soffit vent, attic seems to hold up fine. Neighbor on one side has no soffit vents, he doesn't seem to care. Roof decking doesn't have a single sag or dip in it. However, I'd like to get the upstairs a little cooler and add some life to the shingles.
The unfinished space behind the kneewalls is really tight. Anything you can stand up in was finished (which was the idea). I can barely fit through the port, and once I'm in, I've got 18" of blown insulation over the joists and not a lot of headroom. Just getting the planks so I can move around will be a chore. Getting baffles in between the insulation and the roof won't be easy.
No kids, but the task would be best performed by somebody 4' tall. Any "little" insulation contractors out there?
I like the idea of using tubes on the soffit vents. I don't know if I can reach the soffits through the attic, I may have to slide the baffle in through the outside.
I think this is going to be fun.
The unfinished space behind the kneewalls is really tight. Anything you can stand up in was finished (which was the idea). I can barely fit through the port, and once I'm in, I've got 18" of blown insulation over the joists and not a lot of headroom. Just getting the planks so I can move around will be a chore. Getting baffles in between the insulation and the roof won't be easy.
No kids, but the task would be best performed by somebody 4' tall. Any "little" insulation contractors out there?
I like the idea of using tubes on the soffit vents. I don't know if I can reach the soffits through the attic, I may have to slide the baffle in through the outside.
I think this is going to be fun.
#9
08-09-02, 08:30 AM
Geetings,
If install soffit vents without a ridge vent then the air can blow directly on the insulation. Bad, bad, bad,
The fact that it's as hot as you say should tell you something about the FG insulation. It's about 10% efficient. It is also about 95% airspaces,so the radaint energy goes right thru, plus the energy that is stored in the fibers AND moisture for later release. So doubling the thickness is a waste of time since you would have more mass and will store more energy to be released later.
The other BIG problem that builders don't think of is that you have stright thru conduction from the 200 deg + shingles thru to rafters. As of now you have a no win situation, unless you want to do something different and reduce the loads dramatically.
For existing homes I would suggest that you check the radiant paints. You would paint the interior of the exterior walls and ceiling. They are about 70% efficient and would help reduce the amount of energy radiang from the surfaces now.
You can also install a single layer of RB on the interior side of the dry wall ( I'm doing this now on a foam panelized home we bought. I expect the energy costs to drop about 30 -40% ) and install 7/8" steel furring strips across the rafters and then new drywall. You do not have to tear out the existing. If you do this then I would recommend removing as much FG as possible and insulate the knee walls with 2 layer RB. Since the RB is only emitting about 5% of the energy you can see that if you have a 120 deg ceiling drywall temp now the radiant barrier will only radiate about 6 degess instead of the 130.
If you intall the RB and remove the FG you probably will not have to in stall soffit vents.
More detailed info will have to be exchanged if you chose this method.
Thank you for considering my opinion.
If install soffit vents without a ridge vent then the air can blow directly on the insulation. Bad, bad, bad,
The fact that it's as hot as you say should tell you something about the FG insulation. It's about 10% efficient. It is also about 95% airspaces,so the radaint energy goes right thru, plus the energy that is stored in the fibers AND moisture for later release. So doubling the thickness is a waste of time since you would have more mass and will store more energy to be released later.
The other BIG problem that builders don't think of is that you have stright thru conduction from the 200 deg + shingles thru to rafters. As of now you have a no win situation, unless you want to do something different and reduce the loads dramatically.
For existing homes I would suggest that you check the radiant paints. You would paint the interior of the exterior walls and ceiling. They are about 70% efficient and would help reduce the amount of energy radiang from the surfaces now.
You can also install a single layer of RB on the interior side of the dry wall ( I'm doing this now on a foam panelized home we bought. I expect the energy costs to drop about 30 -40% ) and install 7/8" steel furring strips across the rafters and then new drywall. You do not have to tear out the existing. If you do this then I would recommend removing as much FG as possible and insulate the knee walls with 2 layer RB. Since the RB is only emitting about 5% of the energy you can see that if you have a 120 deg ceiling drywall temp now the radiant barrier will only radiate about 6 degess instead of the 130.
If you intall the RB and remove the FG you probably will not have to in stall soffit vents.
More detailed info will have to be exchanged if you chose this method.
Thank you for considering my opinion.
#10
08-09-02, 08:30 AM
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Old homes
Yeah mine is 82 years old and never had ANY venting (in take or exhaust) until 2002 and yet there is no damage
Guess the plywood/waferboard used these days isn't as durable as the old 1x6's
Venting the attic HAS made it a lot cooler though !!!
Guess the plywood/waferboard used these days isn't as durable as the old 1x6's
Venting the attic HAS made it a lot cooler though !!!
#11
08-09-02, 09:19 AM
Appreciating all your knoweldge!
Rbisys,
I've read nearly all your posts on the need for blocking radiant heat transfer on this board prior to making my post. I do plan to get proper soffit --> ridge vent airflow at some point in time regardless of what else I may install in the attic.
From what I've observed in the house, I believe all the extra blown-in insulation in the attic floor does increase the cooling time of the house at night, it seems to stay warm until around 11pm.
My questions/concerns about radiant barriers follow:
1) If I paint the underside of my roof, won't that cool my room but destroy my shingles? If the heat from the roof has nowhere to radiate to, won't it just accumulate there? I do not have a cold roof/cathedrial ceiling, the roof was designed to cool itself into the unfinished attic space.
2) Would it be possible to apply this RB paint to the finished attic space and block heat transfer from the unfinished space to the finish space? [If that's what you meant in your post, sorry for misinterpreting you.]
3) Would the installation of a RB in the unfinished space be effective, or would it immediately be rendered useless by dust and blown-in insulation? Would the RB create a vapor barrier "sandwich?"
The idea of adding a second layer of drywall with a RB between it is interesting, but I'd prefer not to shrink the space up there.
You guys have been very helpful. The people that sold me the house lived there 3 years and just ran the window AC unit a lot. I don't think they even knew what a soffit was and I doubt they ever poked their head in the unfinished parts of the attic. Can't help but wonder who had the smarter approach. . . . .
I've read nearly all your posts on the need for blocking radiant heat transfer on this board prior to making my post. I do plan to get proper soffit --> ridge vent airflow at some point in time regardless of what else I may install in the attic.
From what I've observed in the house, I believe all the extra blown-in insulation in the attic floor does increase the cooling time of the house at night, it seems to stay warm until around 11pm.
My questions/concerns about radiant barriers follow:
1) If I paint the underside of my roof, won't that cool my room but destroy my shingles? If the heat from the roof has nowhere to radiate to, won't it just accumulate there? I do not have a cold roof/cathedrial ceiling, the roof was designed to cool itself into the unfinished attic space.
2) Would it be possible to apply this RB paint to the finished attic space and block heat transfer from the unfinished space to the finish space? [If that's what you meant in your post, sorry for misinterpreting you.]
3) Would the installation of a RB in the unfinished space be effective, or would it immediately be rendered useless by dust and blown-in insulation? Would the RB create a vapor barrier "sandwich?"
The idea of adding a second layer of drywall with a RB between it is interesting, but I'd prefer not to shrink the space up there.
You guys have been very helpful. The people that sold me the house lived there 3 years and just ran the window AC unit a lot. I don't think they even knew what a soffit was and I doubt they ever poked their head in the unfinished parts of the attic. Can't help but wonder who had the smarter approach. . . . .
#12
08-14-02, 09:20 AM
Greetings,
You've asked some good questions. The problem with home owners not getting the maximun results from RB is because they do not get the right info.
RBs DO NOT affect the shingle life. That law suit has already been settled.
If you use paint you can do both the sheathing and interior wall, BUT.
Again the BIGGEST problem, is energy CONDUCTED thru the rafters. Paint will not stop this. In this type of situation you could probabaly get more energy thru the rafters than thru the FG. The reason I'm stessing this is I getting that you have a 1 1/2 story house and if that is the case then you will have rafter exposure on the slanted walls. Now, if you have a rafter/ joist system where the rater/joist is seperated by an air space, then that is a different situation. In that case you merely install a type 3 RB over the existing insulation.
I'm glad you mentioned the add'l a/c run time. I try to explain that to people and they don't believe. Installing R19 over R19 MAY/MIGHT reduce your heating bills a little. BUT it will probably increase the a/c bills.
The inside method I described does not take that much room. You have your 1/2" x4x4 osb plates attached to the rafters 24" c/c thru the drywall, the RB to the plates( about 4 mil), the 7/8" steel furr'g strips and the drywall.
The amount of dust on a side wall is minimal to non existent. Example, the maximun reduction in ceiling dust coverage is about 20%, leaving 80% efficiency, still about 10x more efficient than FG If you are using a type 4 ( 3 layers) that leaves you with two permanently unaffected layers. On the exposed side walls the effect, IF ANY, would not affect the performace. Remember the inside foil is not affected. Actually one layer is all that is necessary, but 2 layers is about the same cost and if one nail is good, let's put in two or thee more just in case. The competition uses the dust scare to keep customers from using RB. Same with the statement that RBs are less efficient in the winter than in the summer.
Not knowing the layout of your roof sustem. a drawing would help, and you indicating that you have access to the side walls, taking out the FG and replacing with a type 3 RB would be your best solution. In other words, if insulating from ther attic side is possible then either remove the FG and replace with RB solution, or go over the existing insulation.
Keep in mind that a RB is to energy what a mirror is to visible light. The RB reflects the AVAILABLE amount of heat energy, the mirror visible light energy. Moer light , more reflection, less light, less reflection. FG more energy more transmitted.
Either I've answered your questions or thourghly confused you. Let me know which.
If you want some samples to see how they work, let me know.
Thank you for considering my opnion.
You've asked some good questions. The problem with home owners not getting the maximun results from RB is because they do not get the right info.
RBs DO NOT affect the shingle life. That law suit has already been settled.
If you use paint you can do both the sheathing and interior wall, BUT.
Again the BIGGEST problem, is energy CONDUCTED thru the rafters. Paint will not stop this. In this type of situation you could probabaly get more energy thru the rafters than thru the FG. The reason I'm stessing this is I getting that you have a 1 1/2 story house and if that is the case then you will have rafter exposure on the slanted walls. Now, if you have a rafter/ joist system where the rater/joist is seperated by an air space, then that is a different situation. In that case you merely install a type 3 RB over the existing insulation.
I'm glad you mentioned the add'l a/c run time. I try to explain that to people and they don't believe. Installing R19 over R19 MAY/MIGHT reduce your heating bills a little. BUT it will probably increase the a/c bills.
The inside method I described does not take that much room. You have your 1/2" x4x4 osb plates attached to the rafters 24" c/c thru the drywall, the RB to the plates( about 4 mil), the 7/8" steel furr'g strips and the drywall.
The amount of dust on a side wall is minimal to non existent. Example, the maximun reduction in ceiling dust coverage is about 20%, leaving 80% efficiency, still about 10x more efficient than FG If you are using a type 4 ( 3 layers) that leaves you with two permanently unaffected layers. On the exposed side walls the effect, IF ANY, would not affect the performace. Remember the inside foil is not affected. Actually one layer is all that is necessary, but 2 layers is about the same cost and if one nail is good, let's put in two or thee more just in case. The competition uses the dust scare to keep customers from using RB. Same with the statement that RBs are less efficient in the winter than in the summer.
Not knowing the layout of your roof sustem. a drawing would help, and you indicating that you have access to the side walls, taking out the FG and replacing with a type 3 RB would be your best solution. In other words, if insulating from ther attic side is possible then either remove the FG and replace with RB solution, or go over the existing insulation.
Keep in mind that a RB is to energy what a mirror is to visible light. The RB reflects the AVAILABLE amount of heat energy, the mirror visible light energy. Moer light , more reflection, less light, less reflection. FG more energy more transmitted.
Either I've answered your questions or thourghly confused you. Let me know which.
If you want some samples to see how they work, let me know.
Thank you for considering my opnion.
#13
08-14-02, 10:51 AM
You're not confusing me, I think.
Rbisys,
Your time and knowledge is appreciated. At this point, my plans are to install soffit and roof vents to vent the pre-kneewall attic space, and continue to use the gable vents for the attic space at the peak of the roof. Not so much for me, but for the life of my roof and attic.
Although I will consider RB installation, I didn't find the 100+ days painful enough to jump at it. If the next few summers and winters are rough up there, it's something I will further research. The attic space isn't easy for a 6' tall guy to crawl around in.
Your time and knowledge is appreciated. At this point, my plans are to install soffit and roof vents to vent the pre-kneewall attic space, and continue to use the gable vents for the attic space at the peak of the roof. Not so much for me, but for the life of my roof and attic.
Although I will consider RB installation, I didn't find the 100+ days painful enough to jump at it. If the next few summers and winters are rough up there, it's something I will further research. The attic space isn't easy for a 6' tall guy to crawl around in.
