I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

So, here's the deal. The roof consists of 3 seperate
sections. One of those is a cathedral ceiling, so using
a ridge vent there is a given. The other two sections which
are the area of interest a

Section 1 - Currently has a gable vent in one end and
a power fan near the other end.

Section 2 - Currently has a gable vent in each end, with
a power fan blowing air out behind one of those gables. This
section is over the 2nd floor bedrooms where keeping it cool is
very important.

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

Thoughts?

wrote in message
...
I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

So, here's the deal. The roof consists of 3 seperate
sections. One of those is a cathedral ceiling, so using
a ridge vent there is a given. The other two sections which
are the area of interest a

Section 1 - Currently has a gable vent in one end and
a power fan near the other end.

Section 2 - Currently has a gable vent in each end, with
a power fan blowing air out behind one of those gables. This
section is over the 2nd floor bedrooms where keeping it cool is
very important.

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

Thoughts?

Like this?
http://www.benjaminobdyke.com/resour...nt%20Works.pdf

How about both, putting pancake/muffin fans along the peak, to force air out
of the ridge, on a thermo/humidistat?
And controllable dampers at the soffit (point 6 in the pic).
Intuitively, I think on very hot days, some power assist would greatly help.

Also, how bout a double-wall roof, about a 4" gap. This would radically
reduce the heating load in the summer, as well, and could also be controlled
with louvres, dampers. The attic would be more usable, climate-wise.
This may elim the need for fans altogether.
--
EA

On Feb 21, 8:38*am, "Existential Angst" wrote:
wrote in message

...





I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. *I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. *Personally, I
can see advantages and disadvantages to both. *I'm
interested in other experiences and opinions.

So, here's the deal. The roof consists of 3 seperate
sections. *One of those is a cathedral ceiling, so using
a ridge vent there is a given. *The other two sections which
are the area of interest a

Section 1 - Currently has a gable vent in one end and
a power fan near the other end.

Section 2 - Currently has a gable vent in each end, with
a power fan blowing air out behind one of those gables. *This
section is over the 2nd floor bedrooms where keeping it cool is
very important.

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. *His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

Thoughts?

Like this?http://www.benjaminobdyke.com/resour...%20Vent%20Work...

How about both, putting pancake/muffin fans along the peak, to force air out
of the ridge, on a thermo/humidistat?

If you have a ridge vent, then THAT is the vent at the
peak. You don't want other vents in the roof too,
certainly not power vents and especially not anywhere
near the ridge, because then air flows from the other
vent that is nearby, over to the ridge and out.
That doens't do anything to cool the rest of the attic.
With a ridge vent the idea is that air enters the soffits
and exists via the ridge, uniformly moving air.

Also humidity is not an issue with either the existing
approach of going with a ridge vent.


And controllable dampers at the soffit (point 6 in the pic).
Intuitively, I think on very hot days, some power assist would greatly help.

Also, how bout a double-wall roof, about a 4" gap. *This would radically
reduce the heating load in the summer, as well, and could also be controlled
with louvres, dampers. *The attic would be more usable, climate-wise.
This may elim the need for fans altogether.
--
EA


By getting a new roof, I meant tearing down and re-shingling,
not building a whole new roof.

wrote in message
...
On Feb 21, 8:38 am, "Existential Angst" wrote:
wrote in message

...





I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

So, here's the deal. The roof consists of 3 seperate
sections. One of those is a cathedral ceiling, so using
a ridge vent there is a given. The other two sections which
are the area of interest a

Section 1 - Currently has a gable vent in one end and
a power fan near the other end.

Section 2 - Currently has a gable vent in each end, with
a power fan blowing air out behind one of those gables. This
section is over the 2nd floor bedrooms where keeping it cool is
very important.

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

Thoughts?

Like
this?http://www.benjaminobdyke.com/resour...%20Vent%20Work...

How about both, putting pancake/muffin fans along the peak, to force air
out
of the ridge, on a thermo/humidistat?

If you have a ridge vent, then THAT is the vent at the
peak. You don't want other vents in the roof too,
certainly not power vents and especially not anywhere
near the ridge, because then air flows from the other
vent that is nearby, over to the ridge and out.
That doens't do anything to cool the rest of the attic.
With a ridge vent the idea is that air enters the soffits
and exists via the ridge, uniformly moving air.

Also humidity is not an issue with either the existing
approach of going with a ridge vent.


And controllable dampers at the soffit (point 6 in the pic).
Intuitively, I think on very hot days, some power assist would greatly
help.

Also, how bout a double-wall roof, about a 4" gap. This would radically
reduce the heating load in the summer, as well, and could also be
controlled
with louvres, dampers. The attic would be more usable, climate-wise.
This may elim the need for fans altogether.
--
EA


By getting a new roof, I meant tearing down and re-shingling,
not building a whole new roof.
================================================== ======

Well, when the shingles are off, they could just put some 2x4s on edge, and
tack on the plywood sheathing.
Then you'd have yer air gap. I've always wanted to do this for myself, but
I got slate, which has about another 100 years left on it....

I thnk it's worthwhile looking into, and might not add that much to the
whole roofing job.
Course, you don't want your roof to be a 1,000 sq ft squirrel's nest,
either.... lol
--
EA

On Thursday 21 February 2013 13:25 wrote in
alt.home.repair:

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

Passive venting beats active.

Reason?

Power venting might be "better". Until it goes wrong and stops working.

How many houses have you been into where the bathroom/showerroom fan has
died? Even less people are going to care to mend a building structure fan.
Until something goes rotten...

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Feb 21, 8:40*am, Tim Watts wrote:
On Thursday 21 February 2013 13:25 wrote in
alt.home.repair:

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. *I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. *Personally, I
can see advantages and disadvantages to both. *I'm
interested in other experiences and opinions.

Passive venting beats active.

Reason?

Power venting might be "better". Until it goes wrong and stops working.

How many houses have you been into where the bathroom/showerroom fan has
died? Even less people are going to care to mend a building structure fan..
Until something goes rotten...

That's a valid point, but not an issue here, because I'm
only dealing with what I do. And if a fan craps out, I'll
fix it.

On 2/21/2013 8:48 AM, wrote:
On Feb 21, 8:40 am, Tim Watts wrote:
On Thursday 21 February 2013 13:25 wrote in
alt.home.repair:

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

Passive venting beats active.

Reason?

Power venting might be "better". Until it goes wrong and stops working.

How many houses have you been into where the bathroom/showerroom fan has
died? Even less people are going to care to mend a building structure fan.
Until something goes rotten...

That's a valid point, but not an issue here, because I'm
only dealing with what I do. And if a fan craps out, I'll
fix it.




I agree with passive.
My fan stopped working and I replaced it with a passive vent when I got
new shingles.
My neighbor was not so lucky. His caught fire. He might have died had
other neighbor coming home late at night had not noticed it and alerted him.

On Thu, 21 Feb 2013 05:48:41 -0800 (PST), "
wrote:

On Feb 21, 8:40*am, Tim Watts wrote:
On Thursday 21 February 2013 13:25 wrote in
alt.home.repair:

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. *I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. *Personally, I
can see advantages and disadvantages to both. *I'm
interested in other experiences and opinions.

Passive venting beats active.

Reason?

Power venting might be "better". Until it goes wrong and stops working.

How many houses have you been into where the bathroom/showerroom fan has
died? Even less people are going to care to mend a building structure fan.
Until something goes rotten...

That's a valid point, but not an issue here, because I'm
only dealing with what I do. And if a fan craps out, I'll
fix it.



As my brother in law told me once... why pay to move the air? Having
lived in Long Island, I think ridge vent is better. And more
important, if 2 outa 3 roofers like ridge vents where you are, I'd
give that serious consideration.

And FWIW, I once had one in Texas and it stopped working... problem
is, I don't know for how long before I discovered it.

On Thu, 21 Feb 2013 13:40:13 +0000, Tim Watts
wrote:

On Thursday 21 February 2013 13:25 wrote in
alt.home.repair:

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

Passive venting beats active.

+1

Reason?

Power venting might be "better". Until it goes wrong and stops working.

No, it's not better. It's noisy and doesn't work nearly was well as
ridge vent with the appropriate (amount of) soffit vent.

How many houses have you been into where the bathroom/showerroom fan has
died? Even less people are going to care to mend a building structure fan.
Until something goes rotten...

Some are nearly impossible to get to (both bathroom and attic). Go
passive.

my home had just a gable vent at either end, no soffits so no soffit
vents and no ridge vent.

inside attic temperature around 140 degrees, used my fluke recording
temp meter highly accurate...

got eve vent installed high attic temp dropped to 115 degrees.......

my ridge vent worked great

Per :
Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

I am about 23 miles west of Philly.

We had two installs of power fans: one was in the roof facing upward and
the other was in a "window" in one end of the attic.

Never again. The noise/vibration was not worth any increase in
effectiveness.

With the roof mount, I mitigated it somewhat by detaching it from the
roof and hanging it on bungees... but it was not enough of an
improvement for me.
--
Pete Cresswell

On Thu, 21 Feb 2013 10:17:03 -0500, "(PeteCresswell)"
wrote:

Per :
Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

I am about 23 miles west of Philly.

We had two installs of power fans: one was in the roof facing upward and
the other was in a "window" in one end of the attic.

Never again. The noise/vibration was not worth any increase in
effectiveness.

With the roof mount, I mitigated it somewhat by detaching it from the
roof and hanging it on bungees... but it was not enough of an
improvement for me.

I've had 2 roof power vents in this house in the 16 years I've owned
it. The original was replaced with a new one when I re-roofed about
10 years ago. Attic is about 1200 sq ft and batted. Neither one
was loud.or vibrated.

I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

So, here's the deal. The roof consists of 3 seperate
sections. One of those is a cathedral ceiling, so using
a ridge vent there is a given. The other two sections which
are the area of interest a

Section 1 - Currently has a gable vent in one end and
a power fan near the other end.

Section 2 - Currently has a gable vent in each end, with
a power fan blowing air out behind one of those gables. This
section is over the 2nd floor bedrooms where keeping it cool is
very important.

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Two of the roofers say to go with ridge vent on both of
these roofs, get rid of the existing power fan.

One roofer insists that I should stay with using fans on
the two roofs as it is now. His argument is that a power
fan moves a lot more air than a ridge vent system can.
Climate is NJ.

Thoughts?


The ridge vent and other passive venting will only provide a minimal amount
of air movement. If you want to be able to cool down the attic space in
order to lessen your air conditioning load, then you need a powered fan. I
have a ridge vent and also a mushroom type attic ventilator fan on the roof
which definitely lowers the temperature of the attic in the summer.

Years ago, I was helping install AC in second
floor of a house. Air handler in the attic. We
had a power vent put in by a roofing company.
The day they put it in, I wired it to a temporary
source of power. Turned it on, and the attic
temp dropped many degrees, nearly instantly.
I was really impressed how much good it did.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"John Grabowski" wrote in message
news:51264a8a$0$6848

The ridge vent and other passive venting will only provide a minimal amount
of air movement. If you want to be able to cool down the attic space in
order to lessen your air conditioning load, then you need a powered fan. I
have a ridge vent and also a mushroom type attic ventilator fan on the roof
which definitely lowers the temperature of the attic in the summer.

I skimmed Stormin Mormon's post, and while I understand many people in the southern US view attic ventilation as something needed to cool a house (or upper floor of a house) in summer, but the truth is that an unbearably hot attic won't harm your house at all, and so in those cases attic ventilation is desirable, but not necessary.

Where you really NEED attic ventilation is in the winter when warm moist air rises up into your attic and forms frost on the cold roof rafters and roof sheathing up there. That frost doesn't do any harm......until spring when it melts and drips off onto the ceiling insulation. Fiberglass and cellulose insulation work by keeping air stagnant, so wet insulation takes forever to dry out, and wet insulation in contact with wood ceiling joists is a recipe for wood rot growing on those joists. And, as the cherry on the cake, the vapour barrier between the wet insulation and the ceiling plaster or drywall is going to prevent the ceiling from showing any signs that it's wet, thereby lulling the homeowner into a false sense of security that there's no serious problems up there until the joists are so rotted that the ceiling starts to sag under it's own weight and it's too late to avoid major costly repairs to the house. I myself have seen a picture of one house in Winnipeg that was used as a marijuana grow operation that had 3 inches of frost coating the roof rafters and sheathing in the attic.

If you live where it gets COLD during the winter, then read on...

If it were me, I'd go up to my attic today or this weekend and snoop around for any signs of condensation or frost on the roof rafters or underside of the roof sheething. If you don't see any frost, condensation, or mold on the underside of the roof, or dark, dirty looking areas on the top of your ceiling insulation, then you've already got enough ventilation already and adding a ridge vent is only going to waste some money.

(The dark spots on top of your ceiling insulation will have been caused by water dripping off the roof and depositing dust and dirt from the roof onto the ceiling insulation. Check under and around any dirty spots on the insulation for moisture, and if it feels damp there, check for wood rot of the ceiling joists.)

If you don't see any evidence of condensation or frost forming in the attic, I wouldn't mess with success. The evidence there is that you've already got enough attic ventilation so adding a ridge vent is just gonna waste some money.

(I'd put the ridge vent on the cathedral roof cuz you can't get in there to inspect it, so it's better to ventilate the he11 out of that part of the roof rather than risk insulation getting wet up there. Also, if you've had any problems with ice damming on your eves, you'd do well to add more attic ventilation to keep the roof cooler in winter.)

If you do see any evidence of moisture up there, then I'd leave all your existing holes in place, and add the ridge vent when they're doing the roof.

My thinking on this is that once the warm humid air from your house rises into your attic, it's not going to do you any good any more (by being warm and comfortable to be in), it can only do you harm.

So, since there's no benefit in retaining that escaped air, in my humble opinion, the more holes in your attic to allow that warm moist air to escape, the better.

But, I'd be concerned that without the power vents, if you didn't have enough ventilation, there'd be no way to increase the amount of ventilation, so that's the reason I'd keep the power vents. But, if you only had power vents, then you might have a problem at night with those power vents keeping you awake cuz of their noise and vibration, so my gameplan would be to allow for natural ventilation and keep the existing power vents so you have use them when and if needed.

Either way, if you live in the south where the heat in attic spaces can get unbearable, I'd want to keep the power vents to cool the attic in the summer if and when needed too.

Ridge vents, IMHO, are a bit of a scam. You should know that the only claim to fame ridge vents have is that they THEORETICALLY allow 100% sweep efficiency of the attic space because the unavoidable heat loss through your ceiling insulation drives a convective air current that draws cold dry air in the soffits and pushes warm moist air out the ridge; keeping the attic dry in the process. Or so they say.

THE PROBLEM IS that it only works that way on a perfectly calm day. 99 percent of the time, there's some wind outside, and cold dry air blows in the soffits on one side of the attic and pushes any warm moist air in the attic out the soffits on the other side of the house. That is, MOST of the time your soffits are ventiling the attic cuz of the wind through it.

Do this:
Take a cotton shoe lace, pop up to your attic, get one end of the shoelace burning and blow out the flame so that it smolders. Now use that smoldering shoe lace as a poor man's smoke pencil to see how the air is moving up there. If there's any wind outside, then that smoke will be blowing all over the place rather than rising calmly up to the ridge. So, if that smoke isn't rising up to the ridge then adding a ridge vent isn't gonna help very much at ventilating the attic.

(Some people argue that the wind blowing over the ridge of the roof sucks air out of the attic through the ridge vent, but a triangular roof is hardly the right shape to generate aerodynamic "lift" like a wing profile does, so how much good that does is probably negligible.)

Your contractors are gonna say: Don't keep the gable and power vents cuz that will screw up the theoretical 100 percent sweep efficiency you would supposedly get with soffit and ridge vents alone. But, the answer to that question is that you only get that 100% sweep efficiency on a few perfectly calm days every year. The rest of the time the wind outside is causing drafts in the attic that don't give that weak heat loss driven convective air current a chance to become established.

So, if it were me, I would check the attic for evidence of condensation, and only install a ridge vent if you find any, or have had problems with ice dams on your eves in the past.

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your soffit
vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of attic
space. If your house, for example, is 50 x 50 feet (2500 sq ft), you need
about 20 sq ft of soffit, or At your 2" wide existing soffits, and ignoring
dimunition for screening, you'd need (mumble, mumble, carry the three...)
2880 sq inches of soffit. At 2" wide, that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well, yep, you're
under-soffited!

There IS a fall-back rule and it's this: You can't have too much soffit
venting.

--------
* I think this "standard" is for passive ventilation. If you have fans that
are putting the big suck on the attic, you can probably get by with much
less.

On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your soffit
vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of attic
space. If your house, for example, is 50 x 50 feet (2500 sq ft), you need
about 20 sq ft of soffit, or At your 2" wide existing soffits, and
ignoring dimunition for screening, you'd need (mumble, mumble, carry the
three...) 2880 sq inches of soffit. At 2" wide, that works out to be 1400
linear feet.

Now since this example house's perimeter is only 200 feet, well, yep,
you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much soffit
venting.

--------
* I think this "standard" is for passive ventilation. If you have fans
that are putting the big suck on the attic, you can probably get by with
much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent area. As
this is obviously bad for letting mice in, it's usually implement as a 2"
wide series of slots (50/50) or a 1" wide slot with mesh.

That's the soffits - obviously it needs to be balanced with vents up top.
--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Thu, 21 Feb 2013 21:19:20 +0000, Tim Watts
wrote:

On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your soffit
vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of attic
space. If your house, for example, is 50 x 50 feet (2500 sq ft), you need
about 20 sq ft of soffit, or At your 2" wide existing soffits, and
ignoring dimunition for screening, you'd need (mumble, mumble, carry the
three...) 2880 sq inches of soffit. At 2" wide, that works out to be 1400
linear feet.

Now since this example house's perimeter is only 200 feet, well, yep,
you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much soffit
venting.

--------
* I think this "standard" is for passive ventilation. If you have fans
that are putting the big suck on the attic, you can probably get by with
much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent area. As
this is obviously bad for letting mice in, it's usually implement as a 2"
wide series of slots (50/50) or a 1" wide slot with mesh.

That's the soffits - obviously it needs to be balanced with vents up top.


Funny you mention this... I recall one of my homes has this continuous
venting in the soffits, my own residence does not.

Tim Watts wrote:
On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your
soffit vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of
attic space. If your house, for example, is 50 x 50 feet (2500 sq
ft), you need about 20 sq ft of soffit, or At your 2" wide existing
soffits, and ignoring dimunition for screening, you'd need (mumble,
mumble, carry the three...) 2880 sq inches of soffit. At 2" wide,
that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well, yep,
you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much
soffit venting.

--------
* I think this "standard" is for passive ventilation. If you have
fans that are putting the big suck on the attic, you can probably
get by with much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent
area. As this is obviously bad for letting mice in, it's usually
implement as a 2" wide series of slots (50/50) or a 1" wide slot with
mesh.

That's the soffits - obviously it needs to be balanced with vents up
top.

I strongly disagree, for reasons I worked out above using real math.

Further, the notion of "balance" is foolish. If you have too little soffit
vents, you're not getting maximum ventilation. If you have too much, they're
not doing any good.

Remember, you can't have too many or too much soffit vents.

On Thursday 21 February 2013 23:40 HeyBub wrote in alt.home.repair:

Tim Watts wrote:
On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your
soffit vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of
attic space. If your house, for example, is 50 x 50 feet (2500 sq
ft), you need about 20 sq ft of soffit, or At your 2" wide existing
soffits, and ignoring dimunition for screening, you'd need (mumble,
mumble, carry the three...) 2880 sq inches of soffit. At 2" wide,
that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well, yep,
you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much
soffit venting.

--------
* I think this "standard" is for passive ventilation. If you have
fans that are putting the big suck on the attic, you can probably
get by with much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent
area. As this is obviously bad for letting mice in, it's usually
implement as a 2" wide series of slots (50/50) or a 1" wide slot with
mesh.

That's the soffits - obviously it needs to be balanced with vents up
top.

I strongly disagree, for reasons I worked out above using real math.

Feel free too - but you are disagreeing with established government
regulations[1] and not my personal opinion (OK, it's the UK, but the physics
and aim of preventing condensation on timbers remains the same).

25mm or 1" is obviously an arbitrary rounding for convenience, but they will
not be far out from whatever was worked out as "ideal".

[1] This branch of regulation is actually quite sane and deviating from it
would require actually thinking "why do I think i know better?".


--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Tim Watts wrote:
On Thursday 21 February 2013 23:40 HeyBub wrote in alt.home.repair:

Tim Watts wrote:
On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.


Without a bit more info, I can't say for sure, but I'm betting your
soffit vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of
attic space. If your house, for example, is 50 x 50 feet (2500 sq
ft), you need about 20 sq ft of soffit, or At your 2" wide
existing soffits, and ignoring dimunition for screening, you'd
need (mumble, mumble, carry the three...) 2880 sq inches of
soffit. At 2" wide, that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well,
yep, you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much
soffit venting.

--------
* I think this "standard" is for passive ventilation. If you have
fans that are putting the big suck on the attic, you can probably
get by with much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent
area. As this is obviously bad for letting mice in, it's usually
implement as a 2" wide series of slots (50/50) or a 1" wide slot
with mesh.

That's the soffits - obviously it needs to be balanced with vents up
top.

I strongly disagree, for reasons I worked out above using real math.

Feel free too - but you are disagreeing with established government
regulations[1] and not my personal opinion (OK, it's the UK, but the
physics and aim of preventing condensation on timbers remains the
same).

25mm or 1" is obviously an arbitrary rounding for convenience, but
they will not be far out from whatever was worked out as "ideal".

[1] This branch of regulation is actually quite sane and deviating
from it would require actually thinking "why do I think i know
better?".

From the International Code Council:

---begin quote
R806.1 Ventilation required.
Enclosed attics and enclosed rafter spaces formed where ceilings are applied
directly to the underside of roof rafters shall have cross ventilation for
each separate space by ventilating openings protected against the entrance
of rain or snow. Ventilation openings shall have a least dimension of 1/16
inch (1.6 mm) minimum and 1/4 inch (6.4 mm) maximum. Ventilation openings
having a least dimension larger than 1/4 inch (6.4 mm) shall be provided
with corrosion-resistant wire cloth screening, hardware cloth, or similar
material with openings having a least dimension of 1/16 inch (1.6 mm)
minimum and 1/4 inch (6.4 mm) maximum. Openings in roof framing members
shall conform to the requirements of Section R802.7. Required ventilation
openings shall open directly to the outside air.

R806.2 Minimum vent area.
The minimum net free ventilating area shall be 1/150 of the area of the
vented space.
http://publicecodes.cyberregs.com/ic...2_8_sec006.htm
--- end quote

Evidently, reliance on the UK "code" (not cited) is a recipe for disaster.

On Feb 21, 6:40*pm, "HeyBub" wrote:
Tim Watts wrote:
On Thursday 21 February 2013 20:52 HeyBub wrote in alt.home.repair:

wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Without a bit more info, I can't say for sure, but I'm betting your
soffit vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of
attic space. If your house, for example, is 50 x 50 feet (2500 sq
ft), you need about 20 sq ft of soffit, or *At your 2" wide existing
soffits, and ignoring dimunition for screening, you'd need (mumble,
mumble, carry the three...) 2880 sq inches of soffit. At 2" wide,
that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well, yep,
you're under-soffited!

There IS a fall-back rule and it's this: You can't have too much
soffit venting.

--------
* I think this "standard" is for passive ventilation. If you have
fans that are putting the big suck on the attic, you can probably
get by with much less.

The UK guideline for building regs is 1" continuous equivalent.

That means a 1" wide slot all the way around - or the equivalent
area. As this is obviously bad for letting mice in, it's usually
implement as a 2" wide series of slots (50/50) or a 1" wide slot with
mesh.

That's the soffits - obviously it needs to be balanced with vents up
top.

I strongly disagree, for reasons I worked out above using real math.

Did you see my post? Your math had one substantial error
and one whopping 12X error. Applying the 1:150 ratio, you claimed
your 25x25ft attic needed 20 sq ft. It only needs 16.6. A bigger
mistake
was when you came up with 1400 linear FEET. It's not feet, it's
INCHES. Doing the math correctly, that attic would need 200 sq in
of venting. Further, that is TOTAL venting, ie it's split between
intake at the soffits, exhaust at the top. So, to meet the 1:150
ratio, you only need 100 sq in at the soffits. With a 25x25 attic,
that would be met by 1" wide openings run along the two
sides of the roof, 2x25x1=100.

What Tim is saying is done in the UK would easily exceed that, if
it's done on all 4 sides, with 1". Or using 2" on just the two sides
would do it too. Curiously, that is what I have here in the USA.

Also, I see your reference to the current Intrnational Code being
1:150.
I agree that's sounds like a desirable number and it's recommended.
I think it's a good idea for a number of reasons.
However the roofing manufacturers who are giving a very long, if
not lifetime warranty on their products, say 1:300 is the acceptable
minimum. At least the ones I've looked at in detail.





Further, the notion of "balance" is foolish. If you have too little soffit
vents, you're not getting maximum ventilation. If you have too much, they're
not doing any good.

Remember, you can't have too many or too much soffit vents.- Hide quoted text -

- Show quoted text -

I agree erring on the side of having more is better than having less.
But going nuts and putting in 10x what is needed doesn't make any
sense to me either.

On Feb 21, 3:52*pm, "HeyBub" wrote:
wrote:

All sections have continous soffit venting, about 2" wide.
All 3 roofers say that is sufficient and doesn't need to be
improved.

Without a bit more info, I can't say for sure, but I'm betting your soffit
vents are woefully too small.

The "standard" * is 1 sq ft of soffit vent for every 150 sq ft of attic
space. If your house, for example, is 50 x 50 feet (2500 sq ft), you need
about 20 sq ft of soffit, or *At your 2" wide existing soffits, and ignoring
dimunition for screening, you'd need (mumble, mumble, carry the three...)
2880 sq inches of soffit. At 2" wide, that works out to be 1400 linear feet.

Now since this example house's perimeter is only 200 feet, well, yep, you're
under-soffited!

You might want to recheck that math. At the ratio of 1 sq ft for
every 150 sq ft of attic floor, you need 16.7 sq ft, not
20. That is 2400 sq in. With a 2" wide vent, you'd need
1200 linear INCHES, not feet. In feet it's 100 feet.

But there is another thing missing here. That ratio of
1 sq ft of venting for every 150ft of attic floor is for TOTAL
venting, which is supposed to be divided between intake
and exit. So, for the example, you'd need only 50 ft of
soffit venting. Using soffit venting on both halves of the
roof, you'd have twice that. I was making this mistake
earlier today when I was doing the math too.

And the minimum acceptable venting ratio is 1 sq ft for
300 sq ft of attic floor, so I should have plenty.




There IS a fall-back rule and it's this: You can't have too much soffit
venting.

--------
* I think this "standard" is for passive ventilation. If you have fans that
are putting the big suck on the attic, you can probably get by with much
less.

If anything, you probably need more with big fans. One
big issue with attic fans, and why most experts are against
them is that they create negative pressure in the house.
This winds up sucking air conditioned air through any
available route, eg ceiling recessed lights, up into the attic.
So, you're increasing the cooling load on the house.

" wrote:
I'm getting a new roof which of course has lead into
the age old discussion of how best to vent it. I've
got 2 contractors saying ridge only is best, the other
insisting that power fans are superior. Personally, I
can see advantages and disadvantages to both. I'm
interested in other experiences and opinions.

.... snip ...

Thoughts?

One unasked for thought...

If you have pull down attic stair or even just an access panel, built one
of these to insulate the opening:

http://m.youtube.com/#/watch?v=8POZvK9QB6k

I just recently built one and realized I should have done it 25 years ago
when I first moved in. When I pull down the attic stairs and put my head up
into the box, I can feel the heat that the box is keeping from going up
into the attic.

When I had my roof replaced last year, I had full soffit vents cut and a
ridge vent installed. I also added baffles to improve the air flow. No
icicles on my house when other houses had them. Snow remaining on my roof
after other houses had none.

Prior to the new roof, I had no soffit vents and only gable end vents.
Icicles every year, ice dams kept at bay with heat wires. This year, no
wires, no icicles. I'm pleased.

So, the vents let out the heat, instead of your heat staying in? That could
be a bad thing. You have insullation to keep the heat in while the roof is
cold?

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"DerbyDad03"
wrote in message
...

When I had my roof replaced last year, I had full soffit vents cut and a
ridge vent installed. I also added baffles to improve the air flow. No
icicles on my house when other houses had them. Snow remaining on my roof
after other houses had none.

Prior to the new roof, I had no soffit vents and only gable end vents.
Icicles every year, ice dams kept at bay with heat wires. This year, no
wires, no icicles. I'm pleased.

"Stormin Mormon" wrote:
So, the vents let out the heat, instead of your heat staying in? That could
be a bad thing. You have insullation to keep the heat in while the roof is
cold?

Christopher A. Young
Learn more about Jesus
www.lds.org
.

"DerbyDad03"
wrote in message
...

When I had my roof replaced last year, I had full soffit vents cut and a
ridge vent installed. I also added baffles to improve the air flow. No
icicles on my house when other houses had them. Snow remaining on my roof
after other houses had none.

Prior to the new roof, I had no soffit vents and only gable end vents.
Icicles every year, ice dams kept at bay with heat wires. This year, no
wires, no icicles. I'm pleased.

The soffit vents, ridge vents and soffit baffles keep the roof surface cool
to prevent the snow from melting down to the cold overhang and freezing,
causing ice dams. That's one of the reasons for adequate attic
ventilation.

If you have no insullation in your attic, that could mean more heat used. If
you hvae insullation between you and the vents, then the vents are a good
thing.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"DerbyDad03" wrote in message
...
"Stormin Mormon" wrote:
So, the vents let out the heat, instead of your heat staying in? That
could
be a bad thing. You have insullation to keep the heat in while the roof is
cold?


The soffit vents, ridge vents and soffit baffles keep the roof surface cool
to prevent the snow from melting down to the cold overhang and freezing,
causing ice dams. That's one of the reasons for adequate attic
ventilation.

On Feb 22, 7:39*am, "Stormin Mormon"
wrote:
If you have no insullation in your attic, that could mean more heat used. If
you hvae insullation between you and the vents, then the vents are a good
thing.

Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"DerbyDad03" wrote in message

...

"Stormin Mormon" wrote:
So, the vents let out the heat, instead of your heat staying in? That
could
be a bad thing. You have insullation to keep the heat in while the roof is
cold?

The soffit vents, ridge vents and soffit baffles keep the roof surface cool
to prevent the snow from melting down to the cold overhang and freezing,
causing ice dams. *That's one of the reasons for adequate attic
ventilation.

Well, I guess I just assumed that we were discussing a typical house
with at least some attic ventilation.

I don't think too many people would pay to have soffit vents, ridge
vents and baffles installed if that meant the heat would just fly out
through the roof.

On the other hand, keeping the heat in (assuming there is no
insulation) - especially in the summer - would mean that you were
cooking the roof from underneath.

Bottom line: Insulation and ventilation are both required for energy
efficiency, comfort and roof longevity.

Here's what I know: The new venting and baffles have significantly
improved how the snow acts on the roof. The attic stair cover I
mentioned in another post is limiting the amount of heat lost via the
stairway access opening. All in all, I'm happy with the upgrades.