Still seeing frost in attic...!


#21

[quote=“Mono”]

To Ed - I respectfully disagree that simply adding more soffit intake is going to solve the problem without doing anything to the exhaust side. My issue seems to be worse on days with very little or no wind.[/quote]

It wasn’t my assumption that I was posting about, but that of William Rose, who is either the, or one of the, most revered researchers studying attic ventilation. Although I may challenge some aspects of some of their conclusions on occasion, I will still respect his opinions.

Instead of diagnosing the problem after the barn door has been closed, this would have been a simpler matter to deal with during the initial installation by using a product like the Smart Vent that we had discussed initially. At that time, you had informed me which route you were going to take as far as your choice of who to do the job, you stated that the other party had everything included exactly as I had specified.

Now, the intake ventilation was not addressed properly utilizing the entire perimeter, or even half of it.

15 # felt was used in lieu of 30# felt.

3-ply plywood was substituted for 4-ply plywood.

A less regarded style of Ridge Vent was used, which was the Cor-A-Vent product, which does not contain the external baffle like the Shingle Vent II or the Cobra Snow Country.

That version of ridge vent is notorious for not being able to properly exhaust the internal air, firstly, because it functions Only on thermal buoyancy, and secondly, because it is prone to being clogged up due to the lack of internal warm air being released, therefor not melting the fresh snow fall. I posted photos of the Shingle Vent II, the following morning after a 14" snowfall, depicting how the external baffle trough was clear and properly functioning.

In hindsight, did the cost of going with lesser specifications solve the problems?

Even with that said, there is no guarantee that the suggestions for doing the job to a higher level of specification would have alleviated your current concerns, but it would have at least ruled out several distinct possibilities.

DaveB,

I never have seen Solar Powered RIDGE VENTS before. Are you sure about that, or were you referring to Solar Powered Attic Ventilators or Powered Fans?


#22

[quote=“ed the roofer”]

Hi Ed, Yeah just solar powered vent that look like they could be mounted up near the ridge? I was thinking the mechanical induced airflow would be nice in a stable temperature low wind situation?
What’s with all the quality issues you brought up? I din’t see any question of his roof quality or soffit intake capacity?..DaveB


#23

Ed – As I and others have pointed out, William Rose’s theory assumes there is wind.

How does using 15lb felt paper and 3 ply ½â€Â


#24

reading through the thread I noticed the home owner said

Is it possible that the depth of snow has restricted the air flow from the ridge vent?


#25

[quote=“Bill6208”]reading through the thread I noticed the home owner said

Is it possible that the depth of snow has restricted the air flow from the ridge vent?[/quote]

I have noticed the ridge vent blocked after a snowfall. If it’s windy enough, the snow does not last at the ridge very long. However, if we get 2 or more inches of snow and have very little wind, my ridge vent is blocked for a while.

To make matters worse, the snow does not melt around the vent because my attic air is so close to the outdoor air temp.


#26

Firstly, I pointed out the discrepancies in the finished product as an overall view of the entire situation. Those items may not have been typed in this thread, but they were posted nearly concurrently along with this one, so the lack of adhering to the specifications that you yourself pointed out are a valid concern to analyze the full overview of the current predicament.

Also, I even pointed out that even if each of those specifications were done to the higher standards, that they may not have influenced the current resultant observations made by the home owner.

I do not have time right now to find the precise information, but I do recall these statements on an Alcoa learning center site regarding forces at work including the intake ventilation at the soffits.

Quote:
mastic.com/LearningCenter/Ar … offit.aspx
*How weather effects ventilation
Two natural forces – wind pressure and thermal effect – cause air to move into and out of an attic. When wind strikes the end, corner, or roof of a house it will be forced in another direction (usually upward), because wind can not pass through a solid structure. When this happens, a vacuum effect is created near the ends of the structure. As this happens, this newly directed wind enters the attic via vents within the areas and it exits through the other pressure zones around the ends of the structure, acting almost as a natural fan in an attic. The pressure caused by these misguided winds will greatly depend on the speed of the wind itself.

Wind changes direction constantly, sometimes up to 30 degrees within a matter of seconds. Pressure in certain spots causes the vents to either from intake vents to exhaust vents or exhaust vents to intake vents. When this occurs, effective ventilation is minimal.

A home’s exterior can also effect the ventilation of an attic. Wind produces a cooling effect on the outside of the home, which in turn causes the interior to cool a couple of degrees as well.

Thermal effect on ventilation
The second major natural force affecting attic ventilation is the height-temperature difference, or thermal effect. This force results from the difference in temperature of the air in the attic and that outside, combined with the difference in elevation between the lowest, and the highest vent opening. Also, winter temperature differences are small in a well insulated house. Under these circumstances, this force is very limited. In summer, if the vent openings are in the soffit and at the ridge, the air moves adjacent to the hot surface of the roof sheath.

The combined effect of both forces
Wind pressure and thermal effect operate separately or in combination. When both forces are equal, the total air flow will be approximately ten percent greater than for either force operating independently. This percentage decreases rapidly when either force increases over the other.*
End Quote:

Now, as far as wind being a non-factor recently, I have observed very strong winds on a regular basis in our area, especially this past weekend, Friday through Monday. Therefor, the addition of additional under soffit vents would have functioned as stated in the previous quoted reference.

If winds of the forces we had could not have influenced the internal air flow, according to the information I just quoted from, then they must be wrong.

Ed


#27

Just thought I’d ask this. Was the aw used to cut the vent set at an angle to fully open the ridge? About an inch or more opening on each side of the ridge board. Can you see the vent from the attic? Or the mesh? Just curious, because once in a while, that happens, or the opening gets felted over for the night, or whatever, and then doesn’t get cut back.

I apologize for butting in and I haven’t seen the other thread either.


#28

[quote=“tinner666”]Just thought I’d ask this. Was the aw used to cut the vent set at an angle to fully open the ridge? About an inch or more opening on each side of the ridge board. Can you see the vent from the attic? Or the mesh? Just curious, because once in a while, that happens, or the opening gets felted over for the night, or whatever, and then doesn’t get cut back.

I apologize for butting in and I haven’t seen the other thread either.[/quote]

I can see daylight through the ridge vent. It’s cut about 1 ¼â€Â