Hi. As a follow-up to my earlier, somewhat open-ended post, attempting to solve my cold bedroom problems.
My house has a hydronic hot air heating system. The ducting to these rooms runs through an unheated attic (although mostly buried in blown-in fiberglass.) There are the insulated flex-type. There is a continuous ridge vent and 1-1/2″ plug soffit vents in every bay. Is it possible that there is cold air coming in through the gable vent, and then blowing out the ridge vent and in the process cooling down the ductwork? And also bypassing the whole purpose of the soffit vents? WHat happens if I close up the gable vent and there isn’t enough inflow through the soffit vents?
I live on Long Island, NY. Thanks.
Replies
bar.. two things...
the gable end vents should have been blocked when the ridge vent was installed..
they fight each other..
the flow is supposed to be in from the soffits vents and out the ridge vent..
the gable end vents interfer with this flow...
2d thing..
you should add insulation to your duct work one way or another.. blankets on top.. or blowing enough additonal to cvompletely bury the duct..
you might want to smoke test or pressure test you ductwork to make sure it isn't leaking also..
Mike Smith Rhode Island : Design / Build / Repair / Restore
Thanks, Mike.
I was kind of hoping you would tell me not to bother closing it up, since it's going to be a PITA to do it - can't get into the attic. Maybe somebody (Outwater?) makes a triangular decorative panel out of plastic that I can nail and foam into place from the outside. Otherwise I guess I could make something up out of plywood.
Soffit vents ,ridge vents, gable end vents,..they all let air in and air out. Its called circulation.
The gable vents do NOT intrefere with any ventilation streams of a soffit/ridge.In fact, as long as there is sufficient insulation in the attic floor area you can NEVER over-ventilate an attic. The more openings (high, low, sides,etc) the BETTER.
Live and Learn.
hube... what do you base that on ?
if the gable end vent is left in place you will get a little transfer from the gable end straight to the ridge vent..
there will be no drive on the soffit vents.. so they become useless.. and the area in the middle of the house becomes undervented..
the gable end vents do,in fact, interfere with the flow pattern that ridge vents are based on..
in from the soffit... out of the ridge..
course you may have some website that will show that not to be true.. but i doubt it
now.. if ... you want to debate the question of vent vs. no-vent... i'll buy into thatMike Smith Rhode Island : Design / Build / Repair / Restore
Rule of thumb, your vented attic should be as cold as the outside temperature, never block any circulation in your attic. Warm air ducts should not be installed in a vented attic in the first place if you can help it. You are asking for trouble if the attic isn't well insulated. Pile on the insulation but do not block any ventilation.
One problem that can happen is that heat from the ducts will melt roof snow, this water will flow toward the roof edge and freeze because that edge is cooler. Ice builds up causing "damming" this moves under your shingles melts again from the roof heat or warmer weather and flows into the building. Good venting prevents this cycle.
david... it sounds like you are advising NOT to block the gable end vents..
which means that you will ACTUALLYU reduce the amount of ventilation
a well balanced soffit / ridge vent system is the maximum amount of ventilation yoiu can acheive..
if you leave the gable end vents to short circuit that flow.. you will be reducing the ventilation in the atticMike Smith Rhode Island : Design / Build / Repair / Restore
You will have to explain Mike because I just cannot see how opening up the attic for air circulation from gable ends, roof vents and soffit vents will cut down on the air flow. If you are saying that the air flow from the soffit vent and the ridge vent will be interfered with if you install gable vents then I would say that overall the airflow is still adequate.
On this particular house I think the '1-1/2" plug soffit vents in every bay' are too small, the soffit has to be vented more than that, I prefer perforated soffit material.
My experience is that the attic space should be as breezy as the outdoors.
Regards, David
here's one..
http://www.airvent.com/professional/whyVent/evaluate.shtml
and here's another... even better..
http://www.airvent.com/professional/whyVent/evaluate.shtml
the one i'm looking for but haven't found is the one that shows gable end vents short circuiting the flow..
instead of ventilating the attic.. they blow air in the windward end and right out the adjacent ridge vent..
all of the other vents in the attic become dormant because the short circuit takes over all of the drive..
the last link above starts to get into the other part of the equation.. which was always FredL's contention.... that ventilation is useless.. all of the effort should go into controlling the moisture source and sealing the heated space from the attic
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 11/14/2004 8:05 pm ET by Mike Smith
Mike,
I agree with you...........ah..........sort of............
What happens when the ridge vent becomes covered in snow??
BTW, I HATE ridge vents. I think they look awful. And I don't think they work all that well even when properly installed which isn't a whole lot.
But, back to the issue. The gable vent is just below the ridge vent. By having both, the area of open ventilation is increased dramatically and theoretically should be sucking the crap out of the sophitt vents; provided they are not blocked.
My lesson in attic ventilation came as a newlwed, renting a ranch house with small windows at either end of the attic. being por as we were, i decided that the windows should be closed up in the winter; that is until I went up there one frosty day and discovered 2" icicles hanging of the roofing nails.
I do agree that he needs to insulate his ducts well, and it wouldn't hurt to have them tested.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
i've never seen them get blocked... but i guess i t could happen..
that 2d link says that if that does happen , the flow will be from soffit to soffitMike Smith Rhode Island : Design / Build / Repair / Restore
If you've never seen ridge vents (or any other type of roof vents for that matter) covered, you've never seen snow before either.
" I,ve never seen them get blocked, but I guess it could happen" ...
lol. duh. ya, they do get blocked,especially after a 2' snow storm.
no... no.. no.... it doesn't increase the flow .. it short circuits it.
i've seen pics of smoke test..
if you leave the gable end vents it decreases the overall flowMike Smith Rhode Island : Design / Build / Repair / Restore
Now smoke tests I understand, if they show the air flow being short circuited then I am a believer. Thanks, DT
Now see; if you were right here in front of me, I would say "Really!..........hhmmm!"
That's interesting, and something I will look for in the future anytime I read about attic ventilation.
Thanks Mike.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
i had a partner that used to use a similar phrase.." i hear you"..
what it really meant was "BS.. i've listened to you, and you're wrong, but we're not going to discuss it"..
it took me a long time to figure out that he wasn't agreeing with me... hah, hah, hahMike Smith Rhode Island : Design / Build / Repair / Restore
.." i hear you"..but we're not going to discuss it"..
nnaahh, I politely agree, but I would still like to form my own opinion based on my own research! ;~)
I think what Blue said made it home. I hear you're a gambling man.........maybe we should make a wager............seems you're not doing to well lately...........hmmm!
Eric
I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
I think he owes me some hard cash on that Kerry Bush race...I gotta go check the archives.!
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
I think Pete and Buck have pretty much cleaned him out!I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
I recently had a new roof with ridge vents added....Had to ask for soffit vents, nobody puts them in unless asked.... My point: I have a window that's been stuck closed for 50 years and I thought of getting it open/replacing so I could open it in summer and get some ventilation.... ahem, well, even with ridge vents and soffit vents, the attic is as hot as ever in summer time.... This article and your argument are, leave it closed, that stuck window is your friend?
I gotta agree with Mike on this one. Closing the gable vents isn't new knews. They started doing studies back in the early eightys as a result of severe energy crisis .
The theory is that the hot air will rise, escaping out of the highest outlets, while drawing in cooler air from below. If the "below" source of air is the gable vent, then the soffits will not deliver as much as they would in the absence of that gable vent. Additionally, gable vents are prone to creating positive and negative air flows when the wind direction is hitting them. They will actually suck in substantial amounts of blowing snow under some wind conditions.
Just plug them up and balance your lower and upper vents.
Food for thought....the last house I lived in on the Lake had no vents..high or low. I checked in occasionally and saw no frosting...
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
Worked on an old early 1900s two storey with an attic.
Absolutely no venting whatsoever gabel, soffit or ridge.
There amidst the old poured insulation and remenants of knob and tube wiring was nothing but dark charred wood from heat build up.
That and some sweet old victorian vine embrossed gold leaf trim pieces of interior molding which I was given.
Must have been like an oven in the summer.
Must have had atleast one hole for ventilation tho'. That bat had to have gotten in there from somewhere.
Hmmm. We had same. 1914 house, no venting anywhere. But when we explored it, we determined that it was probably smoke from a poorly maintained coal furnace drawing up the balloon framing and out when that roof was covered with cedar shakes. Rafters were original, never had been replaced. (Still had the builder's numbers on 'em...they match the numbers on the back of the molding pieces we found in the rafters of the garage.)
I was originally alarmed enough during the inspection to look into it because I wondered if there had been a fire in the house we hadn't been told about.
Either that, or the five raccoons living up there were smokers :)
They weren't smokers. They were building bonfires on really cold nights.
The convection currents will try to go out the highest point or line (exhaust), but if there isn't enough air flow coming in at the low places (supply) due to lack of vent area, there will be a net heat gain in that space. It's just back pressure. If the gable vent stays, that will be the main supply and will keep air from coming in through the soffit vents because there won't be as much negative pressure above them, caused by the air rising out through the ridge vent. If the ridge can flow more air than the soffit vents, it won't flow as well as needed. You want the soffit venting to be able to pass more air than the ridge, so that whatever the ridge wants to release by convection, the soffit vents can supply.
Mike,
I recently purchased a home (Cape-style) that has a ridge vent, and gable vents at each end of the roof, and also soffit vents but only on one side of the house. I was puzzled by the soffit vents only on one side. When I look at the roof trusses it seems that they were placed on the house biased to only one side giving an overhang for the soffit vents. Should I block up the gable vents in this case too? Or since I only have soffit vents on one side should I leave the gable vents there? It gets really hot up on the second floor in the summer and I recently installed central air whose ducting runs thru the kneewall space. Thanks in advance for any reply.
pizza.. more important than the vent queston is sealing the living space from the attic space.. once you have all of the leaks sealed into the attic, you can increase your insulation levels..
this will do more to keep your 2d floor cool in the summer than trying to optimize your vents.
and .. where the A/C ducting runs thru the kneewall, if you can get in there and bury the duct work in insulation, this will make your A/C run more efficiently..
naturally.. i'm assuming your ductwork was tested for leaks ( smoke test or pressure test )...
before you increase your insulation around the duct.. you should make sure any leaks have been sealed
as to the vents .... the best thing would be to add soffit vents to the side that doesn't have them.. but good luck with that .. i'd concentrate on the sealing and insulationMike Smith Rhode Island : Design / Build / Repair / Restore
What kind of venting should there be in a small cape cod style house with a slate roof in Northern New Jersey? I just read the Slate Roofer's Bible and learned a lot about my slate roof, and that answered my question about why there is no ridge vent, but it did not talk about what kind of venting it does need. I looked in my attic, and the only vents I see are louvered gable vents at each end. One was almost blocked with a huge bird nest. I got that removed and had wire screening nailed over the inside so the birds don't come back in. Will the screening block too much air flow? The attic is unheated and unfinished with no floor and there's an old attic fan up there which is not connected to anything so I don't know if it works. I also think the insulation is installed wrong. It looks like there was some original insulation of some kind (maybe rock-wool?) then someone added a layer of the pink fiberglass stuff over the top, but the vapor barrier is on the top. I don't think that's the way it's supposed to be. I'm now wondering if there are a lot of air leaks because I do get some ice dams forming on the edges of the slate roof. I have also seen frost on the underside of the roof and it gets pretty hot in the summer. Do I need a vapor barrier? I just called an insulation company and asked for advice. I thought the best thing to do would be to take all the old insulation out, seal up the air leaks and start over with new insulation. But he said he does not remove the old insulation, he just blows the cellulose stuff on top of the old stuff and he thought that would take care of any leaks. That doesn't sound right to me. It would probably be a real hassle to get the old stuff out since the only access is through a 20" x 30" hatch in my upstairs hallway. A handyman said for $600 he would remove the old insulation and turn the pink stuff upside down so the vapor barrier is on the bottom. From what I'm reading though, I don't think that would do the trick. What should I expect from a professional insulation contractor? Will they find the air leaks and seal them or just add another layer of insulation?
cynthia.. does your state have an energy office ?
if they do , they will test your house for leaks.. you can do a blower door test and smoke candles.. this will tell you just where the leaks in your house are..
you don't have to remove the insulation to seal the leaks.. once you have the leaks sealed the ventilation needs will become moot.. and your gable end vents will continue to function as they have in the past..
if you don't have warm air leaking out of your heated space, you won't have ice dams either..bet your house is about 75 to 100 years old , right ?
and if your roof / attic is hot in the summer / and cold in the winter... who cares?
certainly not your slate.. once you have the attic sealed.. you can slash the vapor barrier on the fiberglass batts ( or not .. you could ignore them ) and you can have an insulataion contractor blow a cellulose cp right over everything.. leave the rock wool there.. leave the fiberglass.. blow a cap..
the only thing you have to watch out for is fine snow blowing in thru your gable end vents
PS: you actually could have a ridge vent with a slate roof.. but it would be useless without balancing soffit vents.. and then you'd have to block the gable end vents..
ignore all that and concentrate on controlling moisture in your crawl space / basement, sealing the heated areas from the attic, testing your combustion heaters for CO and backdraft
garsh... where is fredL when you need him ? andy says he moved to Florida.. Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,Thanks for your suggestion about the state energy office. I finally found a number and called them but they only do tests for low income people and I don't qualify. I asked them if there was a way I could pay for it, but no. So, then I started calling the insullation contractors. Most of them had never heard of a blower-door test. One said he didn't want to answer a bunch of questions, but if I figured out what I wanted done, I should call him. Yeah, right! It took about six or seven calls before I found someone who would come out and do an evaluation. One guy actually came out and looked in the attic and all around the house. He discovered what I think is the problem. There's a small unheated (and uninsulated) storage space in the kneewall behind the closet. This space is right where the biggest ice dams have been forming, right over my front door. There has probably been a lot of heat escaping up through this space.He is going to seal up the leaks, take the vapor barrier off the top of the insulation in the attic and blow in a layer of cellulose on top. Then he will blow insulation into the floor and insulate the wall of of that storage area. I think that will take care of the ice dams. It's a lot of work finding someone who will do decent work around here. With my slate roof, I had 4 contractors come over to give me estimates, but only one got a ladder and went up on the roof and actually looked around. Since this guy knew about the Slate Roofer's Bible and was listed on Jenkin's site I decided to hire him. I ended up spending about an hour talking with him. It turned out he has a background in art, loves old houses, antiques...long walks on the beach...just kidding.I hope these guys work out. Thanks again.
amazing ain't it ?
guys call it a career and don't know the first thing about weatherizing houses
i like the long walks on the beach.. nothing like a sensitive insulator.....
keep us posted on this thread about how it comes out..
Mike Smith Rhode Island : Design / Build / Repair / Restore
I've looked at several thousand attics.In my area, the strongest correlation to moisture problems (rot, decay, mold, mildew, iced nails in winter) is a very wet crawl space. A very wet basement comes in second. Third is a bathroom with no fan, where there will often be mildew mold above the bathroomI don't care what kind of venting you have, if you get too much moisture up there from down below, you'll have problems.You get the worst problems if you don't have soffit vents and have a relatively low pitched roof. The problems will be more pronounced on the north roof slope.No soffit vents (or blocked soffit vents) and gable and through roof vents, maybe yes, maybe no.High pitched roof, chances of problems are significantly less.The only house I see with no venting are very old houses, with very steep roofs, and I have never seen one of those with moisture problems.Heat buildup - rarely are there visual signs of that problem.Rez reported a charred attic in an old house with an unvented attic.I'm betting fire - I just don't believe attics could get hot enough to char wood, at least in my area.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
That is what I like about this site, lots of good information from experienced people. You did mention "heat buildup - rarely are there visual signs of that problem." I take it you are talking about the appearance of the inside of the attic. My question is, have you seen shingles that curl up so much that the appearance of the roof is changed. I always thought this was from an non-vented attic becoming solar heated and that internal heat curling the shingles. What do you think Bob?
>>have you seen shingles that curl up so much that the appearance of the roof is changed. I always thought this was from an non-vented attic becoming solar heated and that internal heat curling the shingles. What do you think Bob?I should have noted I am in a fairly temperate part of the country (NW Ohio) and roof conditions and shingle problems vary widely around the country, I understand, based on conversations with other inspectors.In my area curling isn't common, and most cases where I see it apparently is the result of multiple layers as opposed to unvented attics.But I haven't seen enough unvented attics (I only see a handful each year, usually very old houses with pretty steep pitches) to draw a firm conclusion - it is entirely possible that in many warmer/hotter areas that would be a significant contributing event.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
There are studies that show a vented roof is less than 5 degrees cooler than an unvented roof - ventilation doesn't extend the life of the shingles
I'm a proponent of unvented roofing systems but I would like to correct your statement if I may. There is info out there that confirms your statement and if it was accurate, then your statement would be also. There have been more accurate and unbiased studies published which show greater differences, as much as 18 degrees. The tests show that it is hard to get accurate results due to the wide range of variables in the field such as color, orientation, climate, and level of shading.
The bottom line is that there is some degradation that occurs but it is less of a factor than roof color and in the worst case, the impact is a couple of years. It is basically a very small tradeoff for what you get out of it and the shingle manufacturers are no longer penalizing warranties for homes built in this manner, but check the individual product guidelines to be sure.
Personally, I've never seen a roofing manufacturer pay off on a warranty anyway.
In NJ it appears that the energy programs are run through the local utilities companies.http://www.betterinsulation.org/energy/NewJerseyIncentives.htmhttp://www.njcleanenergy.com/html/1residential/6_njes_nexus.htmlIn my area if I did a google using the location and Energy Star I would find some links to local groups and people that do Energy Star ratings, but when I try that for NJ I kept coming up with the different utilties and BPU (NJ Cleanenergy). Either Cleanenergy or the local untility company should be able to give you a list of people that do energy star testing.
Bill,
I did check out those sites. Unfortunately, they both led to the same place...the NJ Comfort Partners. They would do all kinds of testing, blower-door test etc., if I had a yearly income under $17,000.
I had tried talking to them to ask if I could pay for the audit, but they said no.
I did learn some stuff from completing the "home energy analysis" on-line though. I filled out some info about my house and my monthly utility bills, and according to their info, my energy bills are about $1,000 per year less than the average home my size. That was good to know.
So I think the main thing for me to concentrate on is eliminating that ice dam on that roof over the front door. That is really hazardous when the huge icicles start melting and the water freezes on my front steps. I'm hoping proper insulation in the kneewall behind my closet (which is over the front door) will help prevent the ice dam.
There is also a real draft in my kitchen. I discovered that when I had new kitchen cabinets installed there'e a space between the top of the kick plate (I think that's what it's called) and the bottom of the lower cabinets. Since I think there is no insulation in the walls of my house, there is a real breeze that comes out from under the cabinets.
I may talk to the insulation installer and ask if it's feasible to blow insulation under those cabinets.
I know I also need new weather stripping on the kitchen door too. There had been metal weatherstripping that kind of interlocked. That worked great to seal out air, but it was so tight I could not get the door open. So I took it off. I tried that stick on foam strip stuff, but that looks terrible and doesn't last very long. I'll have to explore different solutions to that...especially since that is a west facing door and there's real breeze coming through there in spite of the storm door.
But thanks for the links, I learned more stuff from their energy library.
He is going to seal up the leaks, take the vapor barrier off the top of the insulation in the attic and blow in a layer of cellulose on top. Then he will blow insulation into the floor and insulate the wall of of that storage area. I think that will take care of the ice dams.
I'm just a 'muddler, but it sounds like he's on the right track. I don't think rock wool is inclined to mold issues, but I would have been hesitant to introduce a vapor barrier between it and the fg (so I wouldn't have recommended flipping it over). My suggestion would have been to remove the paper from the fg (and thereby remove the vapor barrier), but Mike's suggestion of slits would probably have worked as well.
But anyway, if your guy does what he says he will, you should see a substantial improvement.jt8
This is a great discussion, the question that it raises in my mind is: what if there is no "attic" to speak of. Has been converted to living space, insulated cathedral ceiling, no insulation in floor (to lower section of house), ridge vent, old house, "ventilated" soffits, steep roof (10 in 12?)... That space is warmer than the rest of the house (because heat rises). Moisture level in winter well under control. Any potential for problems down the road? Different considerations?
Thanks,
charles in metro Boston
John,I'm glad to hear you think that will work, 'cause he just finished the job yesterday. I did have to prod him to do some stuff he didn't seem to think was necessary, like sealing around the opening of a vent pipe going through the attic. He said the layer of blown cellulose would seal any air leaks. He may be right, but I wanted it done anyway. I also asked him how he was going to keep the new layer of loose stuff from falling down into the attic access (scuttle hole) He wanted to just surround the hole with fiberglass batts, but I talked him into using some 2 x 4s I had to build a higher edge around the hole and then weatherstripping the cover (with foam weatherstripping I already had) so there was no draft. I also wanted some boards put back up there on the attic "floor" just in case I ever needed to go up there. With the new layer of cellulose, I can't tell where the ceiling joists are anymore. He couldn't understand why I would want to go up there, but you never know...I may need to get to the eve vents to clean out more birds nests or whatever. Now, I'm trying to decide if it would be worth it to have him blow some cellulose into the ceiling of my garage which runs under my kitchen. The kitchen floor is cold. The garage is not heated and has a plaster ceiling. I don't think there is any type of insulation in there, or in any of the walls of this house. The idea of blowing insulation into all the walls is a little too daunting. Since the exterior is brick, I'd have to go through the interior walls and two of the rooms have wallpaper which I don't want to wreck. I don't know if it makes sense to do just some of the walls. This stuff is a bit daunting for me as a first time homeowner. I'm sure glad I have all of you on Breaktime to help me figure it out.
Thanks again.
I also wanted some boards put back up there on the attic "floor" just in case I ever needed to go up there. With the new layer of cellulose, I can't tell where the ceiling joists are anymore. He couldn't understand why I would want to go up there, but you never know...I may need to get to the eve vents to clean out more birds nests or whatever.
I think Mike Smith is a big fan of the cat walks too, although I think he might call them something different. To me it is just common sense that for whatever reason you're gonna eventually have to get up there again. And its SO much easier to put the walkway in BEFORE the insulation obscures everything.
Now, I'm trying to decide if it would be worth it to have him blow some cellulose into the ceiling of my garage which runs under my kitchen. The kitchen floor is cold. The garage is not heated and has a plaster ceiling. I don't think there is any type of insulation in there, or in any of the walls of this house. The idea of blowing insulation into all the walls is a little too daunting. Since the exterior is brick, I'd have to go through the interior walls and two of the rooms have wallpaper which I don't want to wreck. I don't know if it makes sense to do just some of the walls.
Try posting this into a new thread. You'll probably get a lot more feedback.
This stuff is a bit daunting for me as a first time homeowner. I'm sure glad I have all of you on Breaktime to help me figure it out.
They have saved me a lot of time and grief as well. Good resource.
jt8
Edited 12/6/2004 12:38 pm ET by JohnT8
Mike Smith is right on the money about gable end vents at least being ineffective, and that they tend to short circuiting a ridge/soffit vent configuration. There is a roughly 20 page .pdf booklet entitled "The principals of attic ventilation" that anyone should give a quick read if they want to claim that he/she knows about attic ventilation. The web site used to have some graphics that more readily depicted what I said above, but the info is summarized in the booklet:
Go to this page:
http://www.airvent.com/professional/resources/literature.shtml
It is the second link:
http://www.airvent.com/pdf/literature/PAVbooklet.pdf
Another great "feature" of gable end vents is that they can let wind driven rain and other precipitation in you attic which results in soggy insulation... great!
As far as you all who are talking about your 70 or 90 year old house with no attic ventilation, well, let me ask you this: Does a piece of Swiss cheese need to be ventilated to let air through? :-)
Matt
Edited 12/1/2004 7:09 pm ET by DIRISHINME
How do you exactly go about sealing the leaks? Is it with caulk and rigid board insulation on the back side of the knee wall and fiberglas insulation? Combination of all three?
Unfortinately, it takes about 1 hour to seal air leaks into the attic in a new - under construction house - and about a week to do it on an old house. The problem is that in an existing house, many of the leaks are not easily accessable anymore. Look at that attached pics, and it will give you some ideas of where to start. A can of spray foam would probably be your first purchase. Look around plumbing penetrations and any chimneys, or chases too.
Also, something that I do not believe was mentioned above is that the absolute worst thing with respect to moisture in the attic is an bath fan that dumps warm damp air into the attic. Matt
If you're going to air-seal your old house, might be worth investing in a foam gun. About $200 at http://www.efi.org.Re old houses and swiss cheese: try, no house wrap. No tar paper. No tyvek. Nada. Rien. Peek through the sheathing and you see the shingles. I'm told this was done in the 20s to save money....
Dirishinme, I was going to comment on bagging the ceiling fan and sealing it to the vapor barrier but is it just me or is there no ceiling vapor barrier in those pictures?
We don't use ceiling vapor barrier here in central NC. I am aware that it is used up north, but not here. Never seen it, except when someone used fiberglass batts with the paper vapor barrier which I think was really just a means of attachment. Even this is very rare. 98 % of new construction ceilings are blown with either loose fill fiberglass or cels right on the sheetrock.
The sheetrock acts as the air barrier, and as we know, moisture most readily travels on air currents. Contemporary thinking is to stop the air leaks, and thereby stop the moisture transfer.
Here in NC even sidewall (poly) vapor barrier is not as popular as it used to be. It's rather humid here and I guess people are concerned about trapping moisture and having mold problems. Many/most builders are now using the paper sidewall vapor barrier, which is marginally effective - IMO.
All this per local building scientists. Matt
Stick to your belief, you are on the right track technically.
what you are implying is, if you were to remove the entire roof, the wind may effect the venting. ROFLMAO
Mike is right. HO needs to either block the gable vent or the ridge one.
I tagged along with an inspection a few years ago. HO of a 1970's era house had moisture problems in the attic. Fiberglass insulation had gotten moldy and the black mold was working on the sheathing and rafters. Inspector traced it to moisture due to bad ventilation. HO fusses that, "hey I've got soffit, gable, and when I had the roof redone, I had them put in ridge vents."
HO thought he was improving airflow, but as Mike said, he actually short circuited it. This ain't hydrodynamics, this is airflow. Inspector lit up a Marlboro and proceeded to puff out smoke towards the gable vent. It drifted right up to the ridge and on out. He puffed smoke over top of the FG batts and it just kinda hung there. Maybe not a scientific experiment, but it was good enough for me (and the HO).
Nowadays, I'd have worn a mask up there in mold country. Didn't really know its potential problems back then.
The real question I had was how to determine HOW MUCH venting you need. I've been in attics with soffit-ridge venting that just didn't seem to have enough airflow. Mike's links might help there too, I need to go back and read through them.jt8
More holes isn't necessarily better!
Ventilation isn't just a matters of openings and so the more the merrier. It's a matter of airflow and the placement of the intakes and exhaust ports are critical. Badly placed openings can cause air to enter or leave where it shouldn't and although the amount of lfow is high, the location and usefullness of the air flow might be very poor. With ridge vents, if you have gable vents, air will tend to be sucked in the gable vents INSTEAD of the soffit, which means you will reduce the air flow from the soffit vents. In effect, you short circuit the airflow, bypassing the soffit vents. If you are concerned about having enough airflow through the soffit vents, having gable vents won't help that siutaiton but make it worse. If you need nmore airflow through the soffit vetns, definitely close the gable vents. If still concerned, consult a building engineer to calculate the amount of soffit opening you need to ventilate your attic -- but if you have typical soffit vents an the wa around the eaves, yoyu are probably all right.
You can also contact your municipality and as them what the building code requirements are.