increasing attic ventilation

[maverick06]

Without starting an argument about attic ventilation, as its not germane to the question.

I am looking at increasing my attic ventilation.

I have a whole house fan and think I could use more. And more well spaced. I was in my attic yesterday and noticed a modest amount of dust was actually imbedded into the inside of the ridge vent.

I have a ridge vent across the entire roof. I also have some soffit vents. What is strange is that when you open up the soffit, there is drywall (or something similar to it) above the vents... seems to minimize the venting action, but it still vents (you can smell the "attic" smell coming out when the fan is on). I don’t have any idea if they are working properly, but some venting action is happening. I also have 2 gable vents (I have 3 gables).

I am thinking about putting a large roof vent in, maybe another gable vent in the 3rd gable.

Any recommendations? Larger = better in my opinion as the venting is really intended for venting out the whole house fan as opposed to standard attic ventilation.

Thoughts?

 

[woodgeek]

It is normal to have a horizontal board covering the soffit. On my new (vented) roof, we picked a nice looking perforated vinyl piece to cover the soffits--I thought that was all there would be. In fact, they just drill ~2" holes in the soffit boards, and then sling the vinyl underneath. Traditionally, one 2" hole per joist cavity. Online sources recommend the same free section area in the soffits and the ridge--in my case one hole per cavity was less that 50% of the ridge free section. So I complained, and they drilled me two holes per cavity.

If you still have solid soffit boards with perforated product under them--then someone cut a corner on the install! Depending on the vented product, it might be easy to pop out, cut the holes and pop it back in??

 

[Frozen Canuck]

From what you describe you have very good roof ventilation. That only leaves the soffit as a potential choke point stalling that circulation (in at the low point) soffits (out at the high point) ridge/roof vents. When you look up from the soffits you should see an insulation stop with a space at the top of it 1.5-2" for the full width of the stop to allow air in. That's it nothing in the way to slow down air movement what so ever. This drywall or something that you mention, if it is above the soffits it should be removed as it can only slow down/stop air movement. If on the other hand it has been installed on the outside wall to act as an insulation stop then it needs that gap 1.5-2" at the top. Either way I would bet the sofffit holds the key to your problem. That smell you mention is likely the beginning of a mold formation & I suggest you make this issue a fall project for this year not the next. Roof rot is pricey to fix & you will likely have to hire it out, fixing soffit issues even if you have to relace all the soffits (which I highly doubt) is much cheaper & is something you can DIY in your spare time (evenings/weekends). Hope this helps & that the weather holds for you to get this done.

 

[peakbagger]

I agree open up the soffits they open area should equal the area of the ridge an gable vent. Rarely do the rectangular or even worse the round ones have anywhere near the area. A continuous strip the length of the soffit is the way to go, just makes sure it has metal slots outside and screen inside to keep the critters out.

 

[joefrompa]

Have more intake area than exhaust area by 10-15%.

You can tell if your attic is venting properly based upon moisture, signs of build-up, and attic temp on a sunny day. If you have no signs of moisture, the air feels not overly stale/moist, and the temp is within a normal range, then you are probably good to go and additional steps may not be necessary.

Gable vents + soffit vents + ridge vent is not an ideal design. You only want 2 of those ideally - soffit & ridge or gable & ridge. You want a clean intake to exhaust pathway to maintain air flow. o I don't think adding another gable is going to do much. I believe soffit to ridge is the best of breed, but that's another argument for another day.

From what you've described, if you think you have a ventilation problem it is almost certainly due to too much exhaust and not enough intake. Your soffits should have a clear pathway from soffit up into the attic along the roofline to the ridge. If it's obstructed by drywall or insulation, it's restricted.

Last thing I'll add is that MORE ventilation is mostly desired during the summer (unless there's a definite moisture problem, in which case of course year round is desired). Have you considered adding a gable-vent fan on a self-actuated switch or timer? Turn it on during the hot sunny days, turn it off at night or whenever. There's also solar powered gable vent fans, though those are a mixed bag.

 

[Highbeam]

You have a whole house fan that dumps house air into the attic to then be forced through the roof vents right? There are also attic fans that kick on at a preset temp and blow the hot air out.

A continuous ridge vent is pretty much excessive so the top is covered. You now need to open up the soffits. You want a flow of air and since the ridge is on top, it will exhaust. The soffits will typically be the control and you have nothing to lose by opening them up.

Your whole house fan is a different issue. Is it not funtioning properly due to a lack of roof outlet area?

 

[Don2222]

Hello

In my opinion if you have a good working Soffit vents and Ridge Vent then the gable vents are not needed in the Winter and should be closed up! Also I remove the fan blade from my whole house fan in the fall and cover it with 6 inches of insulation for the winter! The winds really howled thru my gable vents sucking the heat out of the house like crazy. So I made plywood doors with foam insulation and weather seal to close them up tight in the winter and wow what a difference it makes. The house is sooo much more warm and comfortable in the winter time. Then of course I open them back up in the summer!

 

[joefrompa]

Don,

Huh, I kinda like that idea. Never saw that before. You have a ridge vent?

I'd consider that in the winter myself but have no ridge vent, so I'm wondering if I can get away with it

 

[Don2222]

Don,

Huh, I kinda like that idea. Never saw that before. You have a ridge vent?

I'd consider that in the winter myself but have no ridge vent, so I'm wondering if I can get away with it

Yes, I do have a ridge vent and strip soffit venting.

Also I have rafter vents that go all the way to the ridge vent so the cool air for the roof does not short circuit with the attic air!!

It is simple, the Roof is cool so no ice damns

The attic air is warmer so the air in the house stays warmer!! I save 10% on heating costs in the winter.

Also by adding the Home Depot reflectix foil over the rafter vents the house is 10 degrees cooler in the summer!! Saves alot of air conditioning costs!

See pics below. Last pic shows peak inside the attic roof.

 

[maverick06]

Fascinating responses.

I figure I have about 80 ft of ridge vent, and an equal amount of soffits. The soffits are not continuous, but are every third panel is perforated. The smell is the typical "insulation smell" or so I would call it. I have issues with airborne insulation, and i have rock wool and fiberglass up there, so I wear a respirator in the attic. I do not think it gets overly hot, nor overly humid. I have a VERY shallow pitched roof so have had minor ice dams (2" in a BAD snow storm, no problems caused, this happened once).

With the fan running I can feel the air moving from the attic, through the walls, and out some of the outlets. its not much, but its noticeable. I really didnt like the appearance of dust beginning to plug up the ridge vent. I also think the ridge vent was probably a pretty cheap one.

The fan is a 5700 CFM 30" belt drive (which I love love love!)
http://www.ronshomeandhardware.com/...campaign=comparison_shopping_feeds&Click=1014

Which needs 1095 SQIN Of Open Exhaust Vents In Attic Space. I have about 1600 - 1800 sqft of attic... (my guess) Some ridge vents are about 18in^2/linear ft of vent. If I have 80 ft of vent, then I have about a free area of 1400in^2, plus 2 gable vents at about 60 in^2 each, and some soffits....

So I guess looking at those numbers I have plenty of free area. I always assumed that the backpressure through the switches was a bad sign, and the dust in the ridge vent would plug it up... but it looks like I have tons of ventilation. I am uncertain about how well the soffits are done... likely very poorly. but I have no idea. My soffits are all nailed together so removing them would be a massive job, probably destroy them. And the roof is so shallow that, although there is a gap between the insulation and the soffit for sure (I snaked a vent that way once) its impossible to see how much venting is done. I could buy a borescope, but thats too much money.

I do have a powered vent in one of the gable vents for those hot days.

I havent had any signs of moisture in the attic, that I know of... and frankly the worst moisture in the attic is probably from me leaving the attic fan on when I shouldnt because it is too humid (but cooler) outside.

So in short.... I guess everything is normal with the attic and I shouldnt complain nor try to solve a problem that isnt there?

 

[joefrompa]

You can drill holes up through your soffits, or crawl into them and cut downwards a bit.

If you have no issues though, I don't see what the gain could be. Plug up that house fan in the winter, if you are crazy maybe take a leafblower or something up there and blow out the ridge vent (first thing that came to mind) if you want. Otherwise it sounds perfectly normal.

Moisture issues are almost always seen in attics. Mold/mildew on wood, damp wood, staining, or even dripping. Doesn't sound like an issue for you!

 

[maverick06]

cool, love it....

too bad you mentioned the leaf blower... I might have to do that from time to time... maybe in another few years....

Thanks!

 

[peakbagger]

I dont agree that gable end vents be closed off in winter if the house is in a heavy snow zone. My house in northern NH will build up snow on the ridge vents completely blocking them for weeks at a time. One of the worse times of the year to have marginal flow up the soffits is when there is snow on the roof and the sun is out as thats when ice damming occurs. The gable end vents dont fill up with snow, although I do have plastic lined trays inside below the vent to keep any fine snow from blowing up in the attic and melting. I agree that during windy conditions, the gable end vents do introduce a lot of air in the attic but if its insulated properly that should not impact the interior of the house.

 

[joefrompa]

Maverick -

One other idea I forgot about is adding a roof turbine vent. If you even get a light breeze up there regularly, it'll do an absolute miraculous job at venting the attic. If you go that route, get a quality one. A good quality one will operate silently - a cheap one will get out of balance, get bearing wear, or otherwise start making noise.

Now, traditionally, soffitt vents + gable vents + ridge vent is already almost overkill - so with the wind turbine it'd really be kicking it up

I'm going to guess that in an ideal world you'd want soffitt vents, ridge vents, and maybe a turbine on the roof. That keeps plenty of air moving along the attic, but it doesn't introduce the things that seem to occur more often with gable vents.

 

[Swedishchef]

Maverick...

Ever hear of Maximum Ventilation? From what I was told, they are the cat's meow. Tons of people in Canada are now installing those on almost every house.
http://www.ventilation-maximum.com/English/products.html

Andrew

 

[Hogwildz]

There should be nothing blocking the soffit vents. Get the drywall or whatever is above it, out of there. All that does is hinder the airflow.
Gable vents are not needed with soffit venting & ridge venting. They can actually also affect the flow of air from the soffit to the ridge vent.
What happens is the gable vents let air in from them direct to the ridge vent. Thus taking away from the flow of the soffit vent. The gable vents are typically high near the peak part of the wall, so the air flows in high and vent close up through the ridge vent. Now the air that typically would be pulled low from the soffit is lessened.
Also, the plywood at the ridge vent should have been cut back 1' to 1-1'2" away from the peak/ridge pole. The ridge pole eats up 1-1/2" off area as it is. This is area under the ridge vent that has no air flow space.

As far as your set up Don. I have never seen a set up like that in the years I roofed. Not saying it won't work. As it may work fine, and if it does, kudos.
The one issue I see that may be possible is while yes you are channeling the cooler soffit air through them to the ridge, but your not taking or as much any heat from the attic open area to the ridge vent.
Not sure how well the foil insulation works to keep the open attic area cool. If it stays cool, then your set up may be a winner. If they are only keeping the roof surface cooler, but still letting heat from the open area to affect the roof, it may be working against itself as far as keeping the roof cooler.
Never seen it, so won't agree or disagree with you setup. But pretty cool idea if it works.

 

[Don2222]

Hello Hogwildz

Yes, The foil does keep the attic air cooler and it works believe me or I would rip it all out!

Also you can see there is a gap in the rafter vents at the peak to let any build up of really hot attic air out!

Yes I agree you have never seen this, this is my idea, so me and one neighbor have it. He paid me to do it!!

The reason no one else will have it is because the building codes only require rafter vents 4 feet up from the soffits to prevent any insulation from blocking the soffit air flow! So no roofer or any builder will spend EXTRA money out of their own pocket to do anymore!!

So thanks for the Kuduos and like I said, this passive solution puts money in my pocket winter and summer from now on with the heating and cooling energy savings. Since my wife and my neighbors wife can actually FEEL the difference we know it really is working every day

 

[peakbagger]

A local builder in Berlin NH used to install handbuilt devices that look like the maximum ventilation units on commerciual buildings. They do work as the snow doesnt build up hihg enouhg to block them and warm air exhausting form the unit usually clears them out. The units he installed are 3 to 4 feet hihg and are definitely an acquired taste.