To vent the ridge or not to vent?
We need to determine whether or not to install a ridge vent when re-roofing and
We live about 12 miles north of Boston, MA, in an English Cape built in 1952, with 3 gables, one at either end of the length and an A-dormer in the front to the right as you face the house. Each gable has a small (9-inch) vent. We need to re-roof and plan to add blown-in insulation (thinking fiberglass at this point) using different professional specialists to do each job.
We have no access above our flat 2nd floor ceilings, but plan to re-roof the house (LATER THIS MONTH!) The roofer proposed a ridge vent, but we have NO soffit vents. The plan is for the roofer to cut the necessary holes for the insulating company to access the “attic”.
I have been told that we may be better off to NOT install the ridge vent since there is no source of venting down low. [Better to have “no” venting, great venting, but NOT poor venting.] We’re unsure whether Prop-a-vents could be installed or how difficult it may be to maneuver in the “attic” area.
Also, our 2nd floor bathroom exhaust fan vents directly into the “attic”. With no access above, we are hoping no problems have developed in the past 53 years! But, we are dealing at the moment with the unknown.
Any suggestions would be most welcomed.
Thanks.
Replies
still...
forget the fiberglass... go cellulose
do you have gable end vents now ? if so, i'd favor the ridge vent over the gable end vents... but you'd have to close the gable end vents
as to ridge vents... if they are not going to use a baffled ridge vent ( best one is ShingleVent II ), then i'd skip the ridge vent
the bath fan HAS to vent to the exterior, i'd go thru the attic to a roof jack
Doesn't ShingleVent make a roof edge venting system that can be installed when reroofing to provide the lower edge inlet?
I'll ask my roofer. Thanks, Bill.
Bill,
there are AT LEAST 2 different syatems available to add air intake as you describe.
Possible problem is that they may not be effective if the kneewall etc. in a cape blocks air flow from the lower roof edge to the ridge.
Stephen
His cape appears to be original, no second floor build out with Knee walls (man, if that's true, I didn't think there were any left that hadn't been built up)
Myself, I'd be pretty leary of those venting drip edges....
I am a little leary myself.
I have used them twice------once with satisfactory results----the other time less than satisfactory----although that was due primarily to a wet, bare earth crawl space puttting huge amounts of moisture into the situation---and beyond my control of the scope of the project.
also saw a couple weeks ago a vented drip edge installation that has appeared to work VERY well---but it wasn't my work---it was a project I was looking at for pricing roof replacement.
Stephen
BTW---there is another product advertised in FHB which I have NOT used yet.
Edited 11/3/2005 10:47 am ET by Hazlett
We do have a knee wall in the Master Bedroom, with access behind. That wall does block access above. However, the entire back of the house has no kneewall.
I have one Insulation company that bid using blown fiberglass and said they would stay about 6 inches in from the outer edges so as not to block any existing airflow (if there is any). The other Insulation company bid blown cellulose and proposed to blow it right up to the inner edges of the "attic" area.
Again, we won't have knowledge of what's above the ceilings until we cut in.
Wonder about the cost vs. the benefits?
OK, you do have a MBR on the second floor...what's on the other side of the room from the kneewall?
BTW, I don't see how you could "stay about 6 inches in from the outer edges so as not to block any existing airflow" without installing baffles of some kind, and before you fill the attic with insulation (and after the roofers have opened up an access hole) it''s a very good idea to find any vent stack ir electrical penetrations & seal them up with spray foam
Great suggestion re. sealing the pipes, etc. while we have access. Think I better have them wrap some insulation on the bathroom ceiling fan vent pipe while they're in there.
There's a storage area behind the kneewall, floored with 8" wide boards. I previously insulated the back of the kneewalls and under the floor boards. In a follow-up visit w/ the Insulation guy, we agreed that he'd install the Prop-A-Vents and I'd cut in the soffit vents -- any suggestion on size? We have 16-inch O/C rafters. There's open rafters outside, so I'm planning to use a hole saw attachment on my drill.
Thanks, Mike. I just discovered this a.m. that there's a second smaller (about 2 inches) vent pipe in our rear roof directly above the 2nd floor exhaust fan -- I wrote the e-mail late last night and hadn't looked closely enough before including that statement. (Shame on me!) So, I assume and hope that it is exactly for the purpose of exhausting the 2nd floor bathroom. It's about 4 feet from the sewage vent pipe.
You strongly recommend the cellulose over the fiberglass -- why? Any opinions about dry vs. sticky cellulose?
I've been told that the ridge vents would potentially be of little value without the soffit vents and prop-a-vents to direct the air flow to the ridge vents. Also, that poor ventilation (i.e., ridge w/o soffit etc) might contribute to moisture buildup and condensation, leading to the insulation getting wet and potential mold problems. Any thoughts?
Thanks again.
You asked why someone suggested cellulose instead of fiberglass and I don't think you got an answer, so--from what I understand, cellulose will let water vapor through--and any that condenses will find its way back out to the dryer side. Fiberglass tend to trap the condensation and when the fiberglass gets wet, it isn't as insulating and it can also lead to mold and rotting of the studs or joists. The cellulose, supposedly, has more capacity to sort of hold the moisture and let it back out without these problems.
Gosh! I'm feeling a bit confused! I had a Utility-provided energy consultation back in 1994. The fellow indicated that if condensation does take place, once cellulose gets wet, it's "gone", whereas the fiberglass can "regain its usefulness". I asked the insulation salesman the question "Why not cellulose" and he essentially said the same thing! He also indicated that the newer fiberglass provides a much denser insulation, essentially equivalent to that of cellulose.
A lot of smoke and mirrors going on here to put down a very good product but not so high tech and shiny as the new types. We have been using cellulose for centuries. In the Northeast, seaweed (another type of cellulose) batts called "Cabot's Quilt" were patented in Boston in the mid 1890's!!!!
I can't agree with that. Cellulose I have sen get damp stays damp long enough to cause mold. Chopped FG is more likely to let the moisture right through and dry itself.
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Based on what I've been told, I agree with you. See my reply 65365.21.
My opinion is that without soffit vents, a ridge vent will accomplish nothing but possibly be a place for snow to blow in. But change that fan duct so it vents somewhere besides the attic!
Just a question but is it possible to add both the soffit vents and Ridge vents? Clearly coming from someone that doesn't know how difficult this is to do so hopefully others will comment on it. (Selfishly asking as I may be in the same situation in a few years when we go to reroof).
We do have some venting however with Windows at each end and we have total access to the attic (1935 English Colonial). I agree with the others though to go with blown in Cellulose (supposed to be better at stopping air leaks as well as insulating).
Curious where you're located as I am also 12 miles North of Boston.
How big is this attic? If there's enough room to crawl around up there, you might do well to create a permanent access hatch in the ceiling of a closet someplace.
-- J.S.
Unfortunately, it's only a couple of feet of clearance - maybe 2.5 or three at most - no usable storage, so no reason to open it up from inside. Over the front gable, there's probably no more than 18 inches. We've decided it's not worth opening the roof to add insulation to this area.
An opening from inside a closet could be well worth having. Not for storage, but for access. If you ever want to run some new wire or find a leak, 30" is plenty of room to work in.
-- J.S.
I won't get into any arguments here on this without walking through the house, but one thing that is true, is that a ridge vent with no makeup at soffits CAN ( not always, but often) in an older house create the kind of suction that will draw warm moist air from the living space, into the atic space, where it is likely to condense and cause more rather than less trouble.
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Piffin:
No arguments here!! Sometimes adding any ventilation to attics can increase the attic moisture. Without first curing the possibly high RH's in the house from wet/damp basements, etc; internally venting what should be vented and then airsealing the attic appropriately, any hole high in the house creates suction in some winds.
Read this article from Canada's national housing agency: http://www.cmhc.ca/en/burema/gesein/abhose/abhose_ce13.cfm
I've been reading this post with great interest. I am having a home built and am a little concerned with the way the attic is being vented. The plans call for ridge vents on the roof. They also show louvered vents on the sides of the house, however when the siders put in the louvered vents, they did not cut out the hole, in other words, they are just decoration. This concerned me, but after reading this post is it my understanding that if you have ridge vents you should not have vents on the sides? I am also having an attic fan installed to get rid of the moist hot air. The soffits the siders have installed are not vented, they are solid.
Thanks,
Wolfman
For venting to work, air has to go in the lower end - the soffit- and out the ridge. Sounds like the siding guys werre ignorant - or that those pop ventsw were for a rainscreen wall systeem and you hhave other ventilation in plan for your attic vent system. It is not hard though to add pop in vents in the soffit after the fact with a hole drill.
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vented ridge requires vented soffits ..
forego the power ventMike Smith Rhode Island : Design / Build / Repair / Restore
Mike and Piffin,
Thanks for your replies. Sounds like I need to have the siders back........again.
Wolfman
Thanks for the comments. I had the Insulation salesman back yesterday and he agreed to install the Prop-A-Vents (I'll be putting in the soffit vents) at a reasonable charge. If the job is done properly (no pun intended!), I suspect that all will be well. As I understand it from other replies, we need to also block off the existing gable vents.
It looks as if it may not be worth blowing insulation into the front gable (at a right angle to the length of the house). The inside ceiling is about three or four inches lower than in our center hallway, so the gable was probably added after the roof on the main part of the house was completed. I guess we'll know for sure when they open the roof.