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Old Farm House Metal Roof - What to do?

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Alisha Hirsch
2/14/2011
We purchased a 100 year old farm house. The building inspector said the roof should last 10 years and just needed some screws retightened. The builder we hired for the renovation agreed. We had the screws retightened, more screws added and the roof painted and insulation added. It's an aluminum sheet metal roof with wood barn board and rafters. You can stand in the attic and it has a peek. There is a vent in the north and south walls. Brick walls go up to the start of the roof (so no ventilation). There is also no ridge vent. There is insulation on the floor of the attic but no vapor barrier. This is our first winter and the metal roof is white underneath from frost and the wood is wet and insulation on the floor is wet. How do we fix this? Please see the picture. (Also I have been told the bathroom vents were done incorrectly by our builder).
Eric Novotny
An informed customer is the Best Customer!
2/16/2011
You mention in the other thread that the roof was spray foamed. Is that the insulation that you are referring to in this thread (i.e. spray foaming the underside of the roof and rafters) or was insulation applied to the topside of the roof deck?
Alisha Hirsch
2/16/2011
Bat insulation was laid on the floor in the attic in this section of the house.
Eric Novotny
An informed customer is the Best Customer!
2/16/2011
You can one of two things: -supply more ventilation to the attic to help remove the moisture and help keep the attic air temperatures closer to ambient or -insulate the attic properly in conjunction with air sealing the attic floor. The typical response to this situation will be to "add ventilation" however that does not address the source of the moisture or reason for its movement into the attic. Extra ventilation just helps remove it from the attic. What you need to realize is that with that moisture, so it heat lost. The home lived for 100 years previously without rotted framing as a result of moisture because we, as occupants, produced less (less showering, washing of clothes, space heating) moisture. There is also the fact that the attic layer has been further penetrated as a result of retrofitting of HVAC, plumbing, etc. Contract with an Energy Auditor to do a building evaluation and air seal the attic floor, penetration, and balloon framing of the home. That will make the home more efficient, more comfortable, and solve moisture/frost issue.
Ronnie Allen
2/17/2011
Imagine that their are thousands of old farm houses with metal or slate roofs that are decades old with attics that don't look like yours. First thing I would do is identify source of moisture in the attic and remedy it. This could be from the bathroom vents, dryer vents, roof leaks, etc... Even the type of heat you use. I would check the roof thoroughly during rains. Tightening screws does not work. Loose screws should have been removed and a new over-sized screw installed. It does no good to tighten back a screw on what is likely a deteriorated washer. I am only guessing that the roof was painted with an aluminum type coating. This does not help with leaks at all. As far as ventilation goes, it would take some work to get your roof vented properly. You do have ventilation now, just probably not adequate. The idea now is that air will enter one side of attic and exit the other through the gable vents on the north and south walls. Adding a ridge vent without the proper soffit vents would be bad. You can do some investigation now to identify the problem yourself. Grab a temperature gauge that also measures humidity and mount it in the attic. Compare this to humidity in the house and outside. The temperature in the attic should be within about 10 degrees of the outside temperature. You don't want to be passing the humidity from inside the house to the attic from any source. If you redo any ducting for the bathrooms or anything else you should use rigid pipe if you can, shortest run possible. Then insulate the pipe. Going out side walls is much better than going through the roof. Good luck.
Eric Novotny
An informed customer is the Best Customer!
2/18/2011
Good recommendations Ronnie. Definitely want to see short runs of rigid pipe on the bathroom vents with insulation wrap around them. I would renew my suggestion for an energy audit. I guarantee that attic has a very high level of connectivity with the living space below and therefore is allowing a tremendous amount of moisture into the attic. Fix the connectivity with proper air sealing and insulation, I would be willing to bet your moisture issue will be solved. The added comfort of the home and the energy efficiency are just bonuses at that point.
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