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senorbungle 01-09-2011 02:32 PM

Ventilating attic with two roofs
I purchased a 1920s-era house in 2009 that has some interesting issues I am trying to resolve on a bit of a shoe-string budget. The issue that I am soliciting input regarding is ventilation for the attic. When a significant remodel and addition was executed in 1970, a new hipped-gable roof was built over the existing nearly flat-pitched roof. Unfortunately, the builders neglected to add any intake ventilation for the resulting attic space created above the old roof. I believe there is sufficient venting into the lower attic (below the original roof), but the air doesnít flow sufficiently into the upper attic area. The existing vents are under eave type, and I believe they allow air to flow horizontally directly into the lower attic. The lower attic is too small to maneuver into, so it is difficult to verify.

After living through first summer I observed that the attic space temperature is quite high compared to the interior of the house. Additionally, Iíve noticed some moisture issues during winter months with condensation appearing on windows in the interior space below the afore-mentioned attics.

I am contemplating several options to resolve ventilation issues. I believe Iíve ordered these from least to most difficult:

1. 1. Cut holes in the lower roof at locations corresponding to the existing vents to allow air to flow from the outside to both the lower and upper attic.
2. 2. Install new soffit vents to allow air flow into upper attic. Leave existing eave vents intact to feed the lower attic
3. 4. Remove the existing eave vents (as they are ugly) and install new soffit vents to flow air into upper attic. Insulate upper attic for greater energy efficiency, relegating the lower attic part of the building envelope.
3. 3. Remove the existing eave vents (as they are ugly) and install new soffit vents to flow air into upper attic. Cut holes in lower roof to allow air flow into lower attic.

Iím pretty unfamiliar with this area of home construction and my research hasnít uncovered any similar scenarios. Iím greatly appreciative of any advice you can provide about my four options, or any that I havenít identified.


Michael Thomas 01-09-2011 03:23 PM

First thing: make sure that all appliance vents, plumbing vents and chimneys are actually venting to the exterior and not into the space between the roofs - I have seen several instances where they were not (!)

senorbungle 01-09-2011 04:17 PM

Thanks for the suggestion, and certainly that's another thing I need to be concerned about. So far the only one I've found that does not vent to the outside is the range hood. To me this roof-over-roof construction seems a bit strange but I do think did a generally good job.

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