# frost under porch roof ? check out video



## die hard (Jan 10, 2013)

hello i am wondering if any one can help... i have a steel roof on top of plywood and ice and water sheild where my porch roof over laps my maine roof it builds up heavy frost ? (check out video )the porch is not enclosed the main roof is cathdral ceiling 18 foot 2x10 with rafter mate tungue and grove pine board and plastic vapor sheild ..if you look at the video i made you will see the green board at the bottom of the main roof with 3 inch vent hole those holes also fill up with heaavy frost . this porch is located on the north side of the house... i live in northern maine temps get below zero almost every night .i heat the house with wood very dry heat live alone take one shower a day .not sure if its condensation or what .thanks for reading my post .. most of the frost melted today before i made video http://www.youtube.com/watch?v=u9je-HudHs4


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## Tinstaafl (Jan 6, 2008)

Hard to say where the moisture is coming from, but that pocketed area between the two roofs should be vented.


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## die hard (Jan 10, 2013)

Tinstaafl said:


> Hard to say where the moisture is coming from, but that pocketed area between the two roofs should be vented.


thanks how would i vent it it is wide open to the air ? i was thinking of filling that area with spray foam . i tried removing that bottom board to let more air flow that did nothing ..every time the frost melts i try something different and it frost backup again


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## Tinstaafl (Jan 6, 2008)

It might look wide open to you, but it's a dead air pocket. Air needs to flow through and out the top. They make shed roof vents for that.


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## LCG (May 30, 2011)

This is a long post, sorry.

On your main roof. Do you have some kind of ridge vent or gable venting?

Here are my thoughts:

I think the most likely answer is that when the roof was installed the transisition was inmproperly installed. My guess is that the installer actually sunk screws into the middle of the transition. This pretty much renders ever the best underlayment useless.

Back to the first question: I think you may be losing heat from the those holes in the fascia. I always see mold/fungus growing on the underside of sheathing along the eves of the homes. This is typically viewed from the attic. I have seen this hundreds of times on home inspections. Heres why.

That potion of the attic is ALWAYS under insulated! The heat from the home raises more rapidly in these areas thus creating condensation on the underside of the sheathing. This condensation turns to frost in the winter and mold in the summer. Either way it is not getting enough ventilation to pull the warm air through the atiic and out the top side vent.

It could be a combination of installation, ventilation, and insulation. Also you may want to look in your attic for a heat source in this area. Mabye there is a plumbing/HVAC/Range vent, god forbid a hot water heater vent that was cut off inside the attic to allow for easy installation of that transition. All of which would aid this issue.

Also, as a certified Home Inspector I can tell you if you ever sell your home and it is inspected you will be forced to completely remove the roof covering and install new plywood. If the inspector is a good one he will actually crawl the attic space and take pictures of the 6' of black mold growing inside the attic at the eve's.

Take the roof completely off. Replace the plywood on the overbuild and the main roof. My guess is you will also need to treat the top side of the drywall and some framing members inside your attic for mold/fungus. I hate to be the bearer of bad news but if you don't get this fixed it can become an even bigger headache. Literally! 

I have seen this too many time's. One lady was having health issues on a home inspection I was doing in Utah. Her house was pristine insdie and out. The crawlspace had a few mold spots but nothing major. I crawled inside her attic and it was FULL if toxic mold. I was wearing a hepa respirator and coveralls so I investigated. She must have had 3000sf of mold growing in her attic. She had no idea. 20yrs of poor health and she was selling her home to help cover the medical bills. Turns out it was her home that killed her.

Get this issue dealt with. PLEASE


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## Dirtywhiteboy (Oct 15, 2010)

Condensation is a big problem with metal roofs that are not properly vented. I have been under metal roofs that were raining inside from the condensation formed from temp. differences.


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## greg24k (May 19, 2007)

Like others said, definitely vent issue and the cause for your problem is the warm air escaping from the house into the attic and gets trapped at the eve were roof pitch is reduced causing the warm air go from the dew point to freezing point...and as you can see it's starting to deteriorate sheeting.

You have to make a design to create a cold roof condition in the attic space. Try to make better attic ventilation so you can keep the attic space cooled with the outside air, which will move the escaped warm air to the outside, instead of trapping the warm air inside the attic. If you would have a snow fall, you will have some major Ice Dam issues and they will destroy your roof.

In addition you should make sure you have sufficient ceiling insulation, to prevent as much as possible heat loss from inside the house.

Good luck


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## die hard (Jan 10, 2013)

I built the house my self . the attic is more of a crawl space and have to remove a few pine boards to get in there ..it is completely sealed off from the house I have 2 8x12 vents on the A part of the attic wall. ..last winter this problem was driving me crazy I climbed up in the attic to so see what was going on up there every thing looks like new no frost/signs of water..I shined my flash light down the rafters threw the rafter mates the roof that also looks frost free . .the only place I'm getting frost is under the porch roof and around the fascia board vents .i think you are right about the air not being pulled up threw I need to find a way to correct the problem.... Before the last time it frosted i stapled a couple rater mates where It is frosting up one on the porch roof and one on the main roof and both sides of the styrofoam rafter mates frosted up ...thanks so much for all your help no need to be sorry for your long post ...sorry I can't type that good


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## LCG (May 30, 2011)

No worries man. I was just concerned for your health. I have seen too many of these go bad so I was naturally alarmed.

It sounds like you have gotten pretty lucky with getting ahead of this issue and I think you can resolve this pretty easily at this point. If you can post a few pics of the roof itself, especially the transition we may be able to help you out a little further.


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## die hard (Jan 10, 2013)

Thanks for getting back here is a couple picture of during construction and finished


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## die hard (Jan 10, 2013)

Only let me post one picture ? So here's another one


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## die hard (Jan 10, 2013)

One more picture ..what I am thinking is this summer fill that dead air space solid with spray foam ?


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## Mr Latone (Jan 8, 2011)

When does the frost first show up? And under what conditions? If the roof is clean and dry and the temps fall hard at night, does new frost accumulate? When does it dissipate? 

In your first post you said it was a cathedral sealing, but you also said there was an attic space. Is it a vaulted ceiling?

You said the circular vents frost up. I would take the fascia board (green) off and see what it looks like under there. Do it while they are frosty and see where the frost appears to end.


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## die hard (Jan 10, 2013)

It first appears in when temps go from above freezing to below freezing and yes if the roof is dry and clean the frost will accumulate and will start to melt on a warm winter day if it does not completely melt more frost will build up the next night..I remove the fascia board light frost appears in the first 2 or 3 feet more towards the fascia board seams to be where the ice and water shield is in the picture ..with a little signs of moisture further up the rafter mates look dry and dusty for the most part..


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## die hard (Jan 10, 2013)

This picture will give some idea of the size of crawl/attic space and it vented with two 8x12 vents on the side wall...thanks for taking the time to reply to my problem


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## oldfrt (Oct 10, 2007)

Only a theory,but bear with me on this.

I'm thinking that maybe your venting is getting "short circuited".
Being that warm air always moves towards the cold,those open
rafter bays(shed roof)and the unfinished ceiling area are keeping the area
above the ends of the propa vents cold enough to draw the escaping 
heat from the ceiling out the bottom of the rafters.
Since the area above the propa vents is probably all about the same
tempature,the colder area(near the facia) is creating the short.
If that area(porch ceiling), was sealed off then there may be more
of a chance for the venting to work properly.

When soffit vent are working properly there is a slight vacuum created
by the ridge/gable vents pulling that warm moist air upwards.
Since the nearest cold area is that open shed roof,this may be allowing
that air to escape before it gets to the ridge/gable vents.
Kind of following the path of least resistance

It looks to me that the facia extends up past the face of the roof sheathing.
Look how wet it looks at the bottom edge of the plywood.When the facia
was on this may have been where the heat/moisture was getting out and onto
the underside of the shed roof.

Good luck
Let us know how you make out.


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## LCG (May 30, 2011)

I think the short circut is possible. It looks like you have pretty good insulation at your eve areas or at least better than some I have seen so I don't think heat loss/draw at your eves is a problem. Even if heat were being drawn out of the vented rafter space it should have enough open air to disipate.

As oldfrt said. Heat is drawn to cold air but more importanly is the fact that heat rises. With that said you may have a blockage somewhere between the insulation and sheathing. I think this is the only way the heat rolling out of the bottom is feasible. 

What do you have for a top vent? Ridge vent or gable. Is it sufficent enough to draw the air from the bottom to the top?

I think your problem is your ice and water guard. I have seen Grace condensate in the summer months under metal roofing. I have NEVER seen it in the winter but it makes sense. It seems that the only areas this is occuring is under the ice guard. Was this ice guard a "High Temp" ice and water guard? 

You could do a VERY simple test:

First, scrub off the existing frost and mold. It doesn't need to be perfect. Just enough to know your starting with a fresh test area.

Next, block off the eve vents for a day or two and see what happens.

If the frost continues you will know it is the ice and water guard or at least a "Top side of the roof" problem.

If it stops, it's a ventilation/insulation problem.

Keep us posted as I am curious how this will turn out. We are called for allot of high mountain roofing issues. Almost all of them are condensation issues. So please keep us posted. Things like this are the reason I linger around these parts.


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## LCG (May 30, 2011)

BTW, It looks like the Moose hunting is pretty good up there:clap:, Is it hard for an out of stater to draw a tag? We're good on Whitetail, Elk and Mule deer here in Wyoming but the moose hunting sucks!

A bit off topic but I am just curious.


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## die hard (Jan 10, 2013)

oldfrt said:


> Only a theory,but bear with me on this.
> 
> I'm thinking that maybe your venting is getting "short circuited".
> Being that warm air always moves towards the cold,those open
> ...


 ya that makes a lot of sense and thats why it is moist near the bottm and dry towards the top ..the bottom of the plywood is soak cause the frost from the to roof melts on it..i held a lighter near the fascia vent to see what way the flame would burn (give me a second to explain) with the porch cold it just does it's own thing .now we are having a january thaw so i inclosed the porch with a tarp and heated it to melt all the frost with the porch warm the flame is being sucked towards the vent up to the ridge (it's only a small flame not going to burn my house down)


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## die hard (Jan 10, 2013)

LCG said:


> I think the short circut is possible. It looks like you have pretty good insulation at your eve areas or at least better than some I have seen so I don't think heat loss/draw at your eves is a problem. Even if heat were being drawn out of the vented rafter space it should have enough open air to disipate.
> 
> As oldfrt said. Heat is drawn to cold air but more importanly is the fact that heat rises. With that said you may have a blockage somewhere between the insulation and sheathing. I think this is the only way the heat rolling out of the bottom is feasible.
> 
> ...


does not apear to have any blockage i can see all the wat to the top with flash light am surprised how well the rafter mates keep the insulation from touching the ply wood.
i have 2 vent on the exterior wall of the crawl space now i am wondering if there big enough.....not sure if its high temp ice and water?....
now if you read what i replied to oldfart i heated the porch and melted all the frost ..........i am going to section it off now that its frost free .....am going to do what you said in one section .in another section i am going to stuff moving blankets to fill that dead air space . in an other section am going to have a fan blowing on it to keep the air circulating ..i almost think i am dealing with 2 different problems one ice and water and one ventalation .. going to be warm the next few days will keep you posted ..thanks again to everyone for all your help for all your help...


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