attic ventilation with open soffits
#1
09-04-02, 01:55 PM
attic ventilation with open soffits
I have a 1950's ranch (~2300sqft) in northeast Ohio that is shaped like a 'T'. The roof has a 4/12 pitch roof with 2 & 3 foot overhangs with open soffits. About 6 years ago the previous owners reroofed and installed a ridge vent and one power vent (of course the motor needs to be replaced). The top section of the 'T' has gable vents on both ends and really has no problems. The long leg of the 'T' has the garage on the end of it with no gable vent to the outside, although there is a screened opening between the living area and the garage where a gable vent would be. The power vent is in the middle of this section of the house. This is also the area where I have problems with ice dams in the winter. The attic and walls contain blown-in insulation. The attic insulation has become compressed and is too shallow. As I stated before, the soffits are open on the exterior and closed off above the wallplate between the rafters. So, in the winter there is no cold air flowing up through the soffits, along the underside of the roof and out the ridge rent. In addition to this there are several recessed ceiling lights that help heat up the attic. All are rated for insulation contact but I don't think they are supposed to be completely covered?
So before I have a parade of contractors come through with an equal number of contrary opinions on what the "proper" solution is, I like to gather comments and suggestions from members of this forum. I also need to keep in mind that my wife may try to impose restrictions on anything that is visible from the outside.
My ideas:
1) Add soffit vents. This would involve drilling/cutting holes in the vertical member that closes off the rafter and covering them with louvered vent covers. From the equations that I've found it would be necessary to place a vent in between every rafter. This is one of the things my wife does not like.
2) Add baffles inside the attic to keep the insulation away from the soffit vents.
3) Have more insulation blown in to increase the attic insulation depth to 6 to 8 inches. I don't remember the recommended thickness for my area.
4) Not sure that there is anything I can do about the recessed lights. Not sure how much they contribute to the ice dam problem.
5) Replace the motor in the power vent and possibly replace the thermostat with a humidistat. Wife does not like the looks of this vent, no way she goes for a larger turbine vent.
6) I also need to properly vent the drier and 2 bathrooms. The bathrooms vent directly into the attic and the drier into the garage. I need to find a way to keep the roof from looking like a vent farm.
Thanks,
So before I have a parade of contractors come through with an equal number of contrary opinions on what the "proper" solution is, I like to gather comments and suggestions from members of this forum. I also need to keep in mind that my wife may try to impose restrictions on anything that is visible from the outside.
My ideas:
1) Add soffit vents. This would involve drilling/cutting holes in the vertical member that closes off the rafter and covering them with louvered vent covers. From the equations that I've found it would be necessary to place a vent in between every rafter. This is one of the things my wife does not like.
2) Add baffles inside the attic to keep the insulation away from the soffit vents.
3) Have more insulation blown in to increase the attic insulation depth to 6 to 8 inches. I don't remember the recommended thickness for my area.
4) Not sure that there is anything I can do about the recessed lights. Not sure how much they contribute to the ice dam problem.
5) Replace the motor in the power vent and possibly replace the thermostat with a humidistat. Wife does not like the looks of this vent, no way she goes for a larger turbine vent.
6) I also need to properly vent the drier and 2 bathrooms. The bathrooms vent directly into the attic and the drier into the garage. I need to find a way to keep the roof from looking like a vent farm.
Thanks,
#2
09-04-02, 09:13 PM
Ice damming occurs when heat from the home manages to get into your attic and warms the underside of the roof. If snow is on the roof, the warmth will melt the snow from underneath the snow. The melted snow will go down your roof and when it reaches that part of the roof where the overhang is, the melted snow freezes and begins to dam back up the roof. This can occur with inadequate ventilation, but by your desciption, you do have adequate ventilation.
Recess lights have been known to cause this problem and bathroom and dryer exhaust vents almost certainly do cause this problem. The way to determine which one is causing the problem, is to go into your attic where you have the ice damming problem and look at the attic floor in that area. If you find recess lights in that area, then it is the recess lights that is causing the ice damming. If you find a bathroom exhaust there, then it is the exhaust. In other words, if the recess lights are on the other side of the attic, the heat from the lights could not travel accross the attic to create the ice damming. The heat would just travel straight up and cause the ice damming above where they are located.
If it is a exhaust from a dryer or bathroom, it has to exhaust out of the attic. The best way, if feasible, is to run a duct to your gable and attach it to a through the wall vent on the gable. Another way is to run the duct to one of your soffits. You cannot use the soffit vent for the duct. You have to install a dryer vent and it must go through the soffit to exhaust out of the attic.
If it is the recess lights, take out the bulb and then pull down the cover to expose the canister. You will notice that the hole in the sheet rock is larger than the canister and you can probably see into the attic. The best way to correct this is to use foam. YOU DO NOT WANT TO GET FOAM ON YOU, FURNITURE OR FLOORING!!! The best way to do this is from the attic. First use masking tape to cover the gap between the sheet rock and canister, making sure it is secure. Then go up into your attic and foam around the canister. Let dry according to the instructions and you can move back the insulation. Cut back the tape on the sheet rock (ceiling) enough so that when you put back the cover, it will cover the tape and will not be visable. Do not remove the tape.
I strongly advise, that if you have never used foam, practice first outside where you won't mind if you create a mess. Also, before you come down out of the attic, check your clothing and the bottom of your shoes. You do not want to go into the house with that stuff on you. The only thing I know that will clean up foam is acetone, nail polish remover. So buy yourself a great big bottle of the stuff. And mind you, it doesn't clean up that well, even with the acetone.
Recess lights have been known to cause this problem and bathroom and dryer exhaust vents almost certainly do cause this problem. The way to determine which one is causing the problem, is to go into your attic where you have the ice damming problem and look at the attic floor in that area. If you find recess lights in that area, then it is the recess lights that is causing the ice damming. If you find a bathroom exhaust there, then it is the exhaust. In other words, if the recess lights are on the other side of the attic, the heat from the lights could not travel accross the attic to create the ice damming. The heat would just travel straight up and cause the ice damming above where they are located.
If it is a exhaust from a dryer or bathroom, it has to exhaust out of the attic. The best way, if feasible, is to run a duct to your gable and attach it to a through the wall vent on the gable. Another way is to run the duct to one of your soffits. You cannot use the soffit vent for the duct. You have to install a dryer vent and it must go through the soffit to exhaust out of the attic.
If it is the recess lights, take out the bulb and then pull down the cover to expose the canister. You will notice that the hole in the sheet rock is larger than the canister and you can probably see into the attic. The best way to correct this is to use foam. YOU DO NOT WANT TO GET FOAM ON YOU, FURNITURE OR FLOORING!!! The best way to do this is from the attic. First use masking tape to cover the gap between the sheet rock and canister, making sure it is secure. Then go up into your attic and foam around the canister. Let dry according to the instructions and you can move back the insulation. Cut back the tape on the sheet rock (ceiling) enough so that when you put back the cover, it will cover the tape and will not be visable. Do not remove the tape.
I strongly advise, that if you have never used foam, practice first outside where you won't mind if you create a mess. Also, before you come down out of the attic, check your clothing and the bottom of your shoes. You do not want to go into the house with that stuff on you. The only thing I know that will clean up foam is acetone, nail polish remover. So buy yourself a great big bottle of the stuff. And mind you, it doesn't clean up that well, even with the acetone.
