If your home was built in 1923, you probably do not mind completely replacing your soffit. With years and years of peeling paint, etc., it may be time to replace it.
- If that is the case, it is best to remove the soffit and install a new wood soffit with a continuous soffit vent.
- If replacing the soffit is not an option, they do make round vents that are easier to install. Simply drill a hole and push in the round vent. Remember, if you are installing soffit vents, it is important to have a ridge vent as well.
In MN, I'm not sure I would wait until after winter to install the vents. Remember, the main reason for roof ventilation is to allow moisture to escape the attic. The main concern in your climate is hot air leaking through your ceiling and coming in contact with a cold roof deck - this could lead to condensation on the roof deck and, eventually, rot.
You mentioned you have a partially finished attic. Does that mean that you have clipped ceilings (sloped ceilings)? If you have this condition, it is important to be sure you maintain a ventilation gap between the insulation and the roof deck.
When insulating your knee walls and ceilings, be sure to maintain a continuous air barrier around your thermal envelope.
- Block under your knee walls between the floor joists.
- Back up your knee walls and seal all seams.
- Block the top of your knee wall.
- Air seal around all top plates and ceiling penetrations in your ceiling.
- Be sure all of this is in good shape prior to installing any insulation.
- Be sure to install baffles at the perimeter of the building to prevent wind wash from your new soffit vents.
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