I have an old leaky old house, about 130 years old, in Northern Michigan. I can grow some huge ice dams in the winter. The house has gable vents and ridge vents but no soffitt vents. I’ve tried to figure out a reasonable way to create soffitt vents but can’t. My question; what about gable end fans, should I use positive pressure, negitive pressure or both with one fan blowing in and one fan blowing out.
What about automatic controls that turn them on when the attic is too warm in the winter, and when it is too hot in the summer.
Replies
It is difficult to help with your problem without some additional information. Why can't you vent the soffits.
By installing a power vent, there is the potential to short circuit the air through the ridge vents and or pull conditioned air from the house, causing more ice dams.
Is this a ranch style? What is the inside of the attic like?
Pazz; I appreciate your interest.
The house is a two story, very high, soffits about 25 feet above grade. the house has four gable ends, with 4 wings and 4 valleys, 3 of them are about 12 feet wide at the base, the other is about 20 feet wide at the base. Actually the height is my biggest problem in venting the soffits. There is a deck over the porch, which is set between 2 of the wings of the house. Working from this deck I was able to vent 2 sections of soffit at the intersection of on small wing and the larger one. I still had a large ice dam in this valley.
One thing that I think adds greatly to the problem is that the heat runs, (forced air) for the second floor run thru the attic, the attic is insulated with shredded cellulose. I have piled cellulose high over the runs but I' m pretty sure there still is a good deal of heat generated by these runs.
The inside of the attic is fairly open, I can walk nearly upright under the ridge line.
All and any advise apreciated. Jamie
"One thing that I think adds greatly to the problem is that the heat runs, (forced air) for the second floor run thru the attic, the attic is insulated with shredded cellulose. I have piled cellulose high over the runs but I' m pretty sure there still is a good deal of heat generated by these runs."Looks like a good option to go with an unvent attic where insulation is placed on the bottom of the roof and the gable end walls.
I noticed that you mentioned that you had the cellulose piled high. Make sure to keep an appropriate air space between the insulation and the roof deck and or the valley rafter.
It is very difficult to insulate this type of home. There are several methods of insulating the duct work in the attic space. Do you have any bathroom vents discharging into the attic?
Any pictures of your home?
Pazz;
The insulation is not in contact with the roof or rafters. There are no vents dischargeing into the attic space. I've read some of the disscussions in the archives about venting attics with fans. I'm retired from a fire department (30 years) ventilation is an important part of fighting a fire in a structure. Positive pressure ventilation (fan blowing air in) was by far more effective than negtive pressure (fan blowing out from inside).
I'm thinking this is the method I might try, or one blowing in and one blowing out. I have four gable ends with gable end vents.
I have pictures but no way to post them.
What ya think.
Jamie
Fans like that could make matters worse by speeding up the stack effect, and sucking expensive conditioned air from your home. You may get moisture problems in the attic, more drafts in your living space, and higher heating bills. If you abosolutely had to, positive pressure would be better that negative pressure.
The best cost/benefit ratio is to seal air leaks through the attic plane. Push the insulation aside, and find all of the holes. Also look for leaky hatches, gaps around chimneys (use metal), open stud bays, etc.
Next, look for leaks in the ductwork. Seal with mastic or foil tape. Wrap ductwork with insulation.
Someone mentioned sealing and insulating at the rafters, which is another strategy. Brings the ductwork inside the weather boundary.
Sorry for delay in responding. I guess you all have convinced me not to use fans. I guess I'll have to get up there and get to work.
Thanks for the help,
Jamie
One problem with fans is that they are a significant maintenance problem. Though occasionally one will still be going after 10 years or so, often they fail in 3 and need to be replaced. The heat really gets to the bearings and dries them out.
Thanks Dan; I've decided not to use the fans.
Jamie