I’m planning on replacing the wood soffit & fascia on my 20 yr old brick ranch in SE Wisconsin with aluminum. We have owned the house for 5 yrs. Presently there is limited venting in the soffit. Only a small vent 3″ vent above each window in the house. There is a folded batt of fiberglass insulation wedged between the top plate and back of the roof deck to keep the blown in insulation in the attic space from reaching the soffit. Only the roof joist bay above each window has a baffle to let air move to the attic.
In addition to this, the bathroom/kitchen vent fans have been exhausting to the soffit. As you can guess, after 20 years of moist air condensing in the soffit, especially in the winter, the framing in those areas need some attention. It also a appears that there has been some carpenter ants in the same areas.
The soffit perimeter is roughly 300 ft with a 2 ft overhang. My plan is to remove the old 1Xfascia & 3/8 soffit, repair the framing as needed, pull out the folded insulation batt, push in a vent baffle in each joist bay, fill in the void beneath the baffle with the batt, and then install new aluminum soffit. The gutter/drip edge will be replaced during an upcoming roof job, so I might wait to install the fascia until after that. I’m planning on just using the existing 2X6 that spans the rafter tails as the sub-fascia, and covering it when installing the new aluminum fascia.
One concern I have is the correct ratio of soffit vents to the 36 squares of roof to the roof venting. What is a good rule of thumb? Should all the soffit sections be vented, every other one, every third? How many roof vents would be sufficient? How about an additional powered roof vent?
Please take a look at the attached drawings to verify what I have tried to describe. Any comments, installation techniques, or tips will be greatly appreciated….
Replies
I think your plan is a good one and, at a first read sounds pretty comprehensive. A few comments:
1) be aware that breaking metal for fascias is a fairly skilled job. The metal tends to "oil can" (not lay smooth) especially for non veteran installers. Assuming that the metal will eventually be covered by gutters makes this less of an issue. On the other hand on the rakes (I'm assuming you are going to do these too), I'd recommend a 1x4 used as a shingle mold attached to the 2x6 subfascia makes a nice detail and helps to alleviate this "oil canning" problem.
2) Re the soffit material, I'm assuming you mean vented material. They don't sell aluminum soffit around here, or at least not that I know of. Most people use vinyl vented soffit material for your type of installation, and I have installed vinyl soffit that has the ventilation up between the "board slots" to where it is difficult to tell that is vinyl, and the vents don't show. You can even mix un-vented with vented material to get just the right amount of venting, and it doesn't hardly show. See attached pic of porch ceiling. Part is vented, part is not. I used the invivent triple 2". Here is a link:
http://www.certainteed.com/CertainTeed/Pro/Builder/Siding/Prodindex/Vinyl/Wolverine/Soffits.htm
With 2' wide soffits, I'd install some intermediate blocking between your lookouts though to provide an additional nailing points.
Re your venting question, the ventilation is figured on attic floor space, not squares of roofing. The formula used in my state code is that there needs to be 1 square foot of ventilation for every 150 sq feet of attic floor space. (1:150) This ratio can be reduced to 1:300 if at least 50% but not not more than 80% of the ventilation is installed in the upper 1/3rd of the attic space. The combination of soffit vents and ridge vents is ideal. Stay away from gable end vents, as they do not make for even air flow and tend to short circuit the stack effect that makes the soffit vent/ridge vent combination work so effectively. If you already have gable end vents, plan on installing ridge vents and blocking the inside of the gable end vents when you get the new roof. I think my roofer charges around $4 a foot installed for shingle over plastic ridge vent. Get the kind that has external baffles.
http://www.airvent.com/professional/index.shtml
http://www.airvent.com/professional/products/ridgeVents-shingleVent.shtml
BTW - I don't work for any of the above companies. I just like to install whatever works best while keeping an eye on the money.
Thanks for the comments. In regards to item 1, I had planned on using pre-bent fascia which comes in 12' lengths. Since the house has a hip roof, there are no rakes to worry about. Although that leads to the next issue of roof venting. I have never seen ridge venting used on a hip roof. Is that because of the lower pitch? On hip roofs I've mostly seen venting installed on the back side of the ridge, in a similar color to the shingles. The reason I am leaning toward aluminum soffit & fascia is that since the house is brick and the gutters will be aluminum, I did not want to add another material or look to this area. However, the vinyl options sure look good.
ditto to all comments so far .. use the heaviest gauge facia you can get .. oil canning is really bad only on the thin stuff, or really wonky facia boards .. I'm just finishing my project now, added pot lights in the soffit, looks really sharp .. on soffit venting, never heard of too much at the soffit, vent it all!
What gauge do you suggest for the fascia?
the heaviest preformed material you can get ..
Soffit: Compare my vinyl to his vinyl ;-)
Fascia: that's interesting. They don't sell prebent fascia metal around here - or at least not that I know of. Sure would be nice for certain jobs...
Venting and hip roofs: Yes, they are problematic. I'm starting a house with a hip roof next week. I'' be putting "pot" vents on the top of back and side roof surfaces. I guess that is what you were talking about? They are shown on this page and called "roof lovers":http://www.airvent.com/professional/products/staticVents.shtml
My own house is a hip roof - although I also have a few gables so I was able to get in maybe 50' or ridge vent which seems to be working fine (house is now 6 years old).
Based on your situation, I'd definitely not vent all of the soffit. If you were to use that vinyl stuff I recommended I'd maybe make every other piece vented. Again, I've never seen metal soffits (but never really looked for them though) so I don't know what it would be like installing that material. Still, there must be some horizontal ridge to install the ridge vent on. Even 10' would help.
Matt
Edited 7/23/2005 6:12 am ET by Matt
pre-bent fascia is good..
for ventilated soffits we like Alcoa ProBead ventilated soffit... it's a 3/8" profile that looks like bead baord.. the accessory J-mold is only 5/8 so the overall profile is very thin .. it works easy.. looks great, and provides a lot of ventilationMike Smith Rhode Island : Design / Build / Repair / Restore