attic damp

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Old 12-05-12, 03:47 PM
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Question attic damp

I have a problem --new roof ,ridge and gable and soffit vents --- north side damp south fine????
 
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Old 12-05-12, 04:13 PM
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Hi windridge and welcome to the forum,
Many possibilities so we will need more information. Here are some questions.

1. Did the house have a problem before the new roof was installed?
2. What was there before and after the new roof for ventilation?
3. Are there any exhaust devices, like bath fans, kitchen fans, venting into the attic? And have you checked to be sure they are venting to the outside after the construction?
4. Are you along the coast with ocean spray to deal with?
5. Below the moisture, is there anything that would contribute to the problem, like a chase way to the basement around a vent pipe?

We will start with these.

Bud
 
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Old 12-05-12, 04:25 PM
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Tx Bud
1] yes had same problem with old roof
2] old roof ridge vent,4can vents and gable vents
3] no and yes
4] no
5] have a triple wall for wood stove with chase to roof ---nothing to crawl
 
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Old 12-05-12, 04:44 PM
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You had ridge vents, can vents, and gable vents, and now have added soffit vents and eliminated the can vents?? Are there soffit vents below the problem area?

Is there any air leakage around that chimney where inside air can get into the attic?

Are the vents to the outside up near the soffits? And is the moisture issue in the same proximity as the vents?

Would you consider your home to be dry, normal, humid? Dry RH < 25%, Normal 30% to 50%, humid > 50%

What living space is below that problem area?

How old is the house and what is in the ceiling for insulation?

Describe your house, ranch, 2-story, hip roof or what?

Bud
 
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Old 12-05-12, 04:59 PM
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]true --though I added the gable and cans when I noticed problem in old roof --soffit vents are below problem area. lower area on roof = more moisture
2] no has metal cape on out side wood chase
3]ridge vent and gabbles are high
3] home is humid above 50% --- have installed dehumidifier x2weeks, to date no change in attic moister
4] bedrooms and bathrooms
5]18yr,r46 combination blown- in fiberglass and bats
6] rambler one story 6/12 with crawl
 
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Old 12-05-12, 05:48 PM
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With the problem area over a bathroom I start to think about long showers and short fan run times. They make timers for the fan switch that allow it to run for 20 or 30 minutes after being turned off. The high humidity is also an indicator of a tight home, not typical 18 years ago, or a high source of moisture. A dirt floor in the crawl can generate gallons of water per day and space around a plumbing vent can deliver it directly to the attic.

Where is your dryer vented? Could that moisture be pulled up into the soffits?

You should start by identifying the source of moisture in the house.
You obviously don't run a humidifier if you purchased a dehumidifier or is this house new to you and maybe there is a humidifier. Dumb question, but I'm a long ways away .

Other sources of moisture beyond the long showers and 3 daughters would be storing firewood inside, fish tanks, tons of house plants, drying cloths inside, or non-vented gas heater.

Is your heat forced hot air or baseboard hot water?

Bud
 
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Old 12-05-12, 06:05 PM
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] long showers ,not a problem --kids are all on there own! ---well kind-a
2] very tight home--built it myself -- I run the dehumidifier now, but like I say no change to date
3] heat with wood --store a small amount in wood box inside (day or two supply)
4] we do dry cloths around wood stove in winter
5] some plant---heat with wood with el baseboard that we only use in winter if we are traveling ---no dryer
 
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Old 12-05-12, 06:14 PM
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Might want to consider blocking off the gable vents.

Having both ridge and gable vents creates an easy path for air to flow between them.

This reduces the draw or stack effect needed to pull air through the soffit vents.

You need that draw to create the air exchange required to get rid of the moisture.

Like all liquids.....air will choose the easiest and shortest route.



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Old 12-05-12, 06:59 PM
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Tx Halton
Yes I have considered that --- though I had same problem when I only had ridge and soft vents with old roof?
 
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Old 12-06-12, 12:05 AM
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With less air circulation than forced hot air heat, a humidistat could lead you in the direction of the source of moisture. Just test different areas and adjust for any temperature change.

So far the problems look like a very tight home, drying cloths inside, no extra run time on the bath fan, and the resulting higher inside humidity. BUT, we haven't seen a path into the attic and it sounds like you have plenty of venting up there.

Halton, leaving gable vents in place will actually increase the total venting with the added concern that it can introduce snow or rain when the wind blows. It is the cold air pushing into the soffits (low vents) that moves warmer air up and out of the attic, as hot air cannot rise all by itself. But that is another discussion .

Can lights and bath fans will often leak air and fiberglass is noted for allowing air to move right through it. Electrical boxes in the ceiling and drops over cabinets can create a path as well.

I didn't see a reply to the dirt floor in the crawl?

Bud
 
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Old 12-06-12, 07:04 AM
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"It is the cold air pushing into the soffits (low vents) that moves warmer air up and
out of the attic, as hot air cannot rise all by itself. But that is another discussion"



hmmm......the outside cold air is the exact same at both the soffit and ridge.

But somehow only the cold air at the soffit chooses to push into the attic?

You're right.....we disagree and that's a whole other discussion.....



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Old 12-06-12, 09:18 AM
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crawl is isulated and has 4mil covering dirt floor. I have not noticed any place where air might be introduced ---but I will go over everything again ------ still, puzzling that only north side is damp??
 
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Old 12-06-12, 10:11 AM
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We are doing well. As we eliminate some of the common problems, what is left becomes more likely.

We know the north side gets much less sun, so here is a thought. Whatever is happening in the attic, that cold side is either getting more moisture, less ventilation, colder temperatures, or some combination of the three. Passive attic venting is powered by height and a temperature difference between inside and outside. As the venting process does part of its job, removing the excess heat, it removes the very force that is powering the venting.

I'm going to have to make this short and skip all of the theory and go to my conclusion:
The north side of the roof stays colder on the underside due to a lack of sun. It then cools further once the sun goes down from radiant cooling. The end result is more cold air on that side of the attic which shuts off the ventilation, cold inside and cold outside equals no air flow. Then whatever moisture has made it into the attic from what we know is a humid house, finds a cold roof and thus condensation.

There was a recent paper of vinyl siding sweating from a similar occurrence of radiant cooling, but I have not seen a paper on this north side issue. There are however some people far advanced from myself I can ask and will do so, since this has come up before.

Give me some background. How long has this been an issue and what steps have you taken to resolve it? I will be back.

Halton, I'll send a PM and we can talk.

Bud
 
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Old 12-06-12, 10:29 AM
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1] problem has existed for at least 5yr
2] have added more soffit vents[birdmouth],new roof with higher profile ridge vent and gable vents, run dehumidifier last 30 days
3] have a storage shed coming of north side of home --- that I plan on removing this month ---just in case that may be slowing air movement to attic
 
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Old 12-06-12, 11:18 AM
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"Halton, I'll send a PM and we can talk"


Not necessary......you won't convince me otherwise......




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Old 12-06-12, 05:10 PM
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When you say very tight and you built it yourself, how extreme did you go in making it tight? A tight home that does not exchange enough air will often have very high humidity. Do you know anyone who can run a blower test to tell us just how tight?

If very tight, one solution for the humidity would be an air exchange system, HRV. You can test this approach by simply opening a window somewhere and monitoring the humidity.

Once you have the inside humidity in the 40% range, the moisture should, I say should, go away. If not, then you need to look for an air leak from house to attic. This link from Efficiency Vermont discusses a variety of air sealing locations and might point you in the right direction.
http://www.efficiencyvermont.com/ste...ide_062507.pdf

Bud
 
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Old 12-06-12, 07:28 PM
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I did pay attention as I was building but did not go overboard. I did install a air exchange fan as it is code in our area, however it never worked from day one --- I am working on getting it up and running. Do not know anyone to do a blower test. thank you for the link
 
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Old 12-06-12, 07:45 PM
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Windridge,
I think Bud is giving you good advice
If your house is reasonably "tight" but you did not go overboard....
you may not have a complete air barrier system between your ceiling and attic...
Like the examples illustrated in the link Bud Posted

and you should for sure get your ventilation system "working"
 
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Old 12-06-12, 07:50 PM
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Halton said:
"the outside cold air is the exact same at both the soffit and ridge"
I disagree
Pressure is unique among atmospheric variables in that it ALWAYS decreases vertically.
The outside absolute pressure at the soffit will be greater than the outside absolute pressure at the ridge.
If the air in the attic is warmer (less dense) than the outside air....
The Colder(denser) outside air will indeed push in at the soffit and move the warmer(less dense) attic air up and out
[exactly as Bud described]
 
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Old 12-06-12, 07:56 PM
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Too funny.....



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Old 12-06-12, 10:47 PM
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I was also thinking of painting north side bed room and bath top with a vapor retarding paint ---- ????
 
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Old 12-07-12, 05:18 AM
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Hi windridge,
Your problem is more likely an air barrier problem....
and a lack of proper source and dilution ventilation
(drying clothes indoors, storing wood indoors and burning wood are adding extra moisture and making things worse)

A high volume of warm moist air is finding a shortcut to the attic...

the flaws in your air barrier may or may not be concentrated on the North side of the house and may or may not be in the vicinity of the wet sheathing

the reason you are not seeing wet sheathing on the south side is probably because the south facing roof is just warm enough to evaporate the water before it accumulates

Do you have an airtight attic hatch?
 
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Old 12-07-12, 05:33 AM
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Hi Halton
glad you have a sense of humor
BTW air is not a liquid
Air is a gas and a fluid but not a liquid
 
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Old 12-07-12, 07:58 AM
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The moisture on the north side of the attic is like the canary in the mine, the symptoms are just showing up there first because it is a colder area. Although moisture can diffuse right through drywall, it is a slow process compared with moisture being transported through an air leak.

Sheetrocked walls provide a lot of leakage area for air to move from inside to attic. If you flipped your house upside down and filled all of the wall cavities with water, it would pour into the attic. Air sealing all walls involves trawling mastic or other appropriate goop over the top 'drywall to top plate seam' of both side of each wall UG! Since that is a huge undertaking, especially with all of your insulation in place, we look for the isolated big leaks that might make enough of a difference to avoid the complete air sealing of the attic floor/ceiling, at least for now.

The other approach is to address the high humidity in the house. The vapor barrier on the crawl floor needs to be near perfect. Taped at all seams and continuing up the foundation walls about a foot, also sealed to the walls. If you have radon issues, then this well sealed cover may also serve as a captive space to be vented to the outside. Another project. If the crawl walls are a source of moisture as well, then a layer of rigid foam glued all the way around can help and insulate. Run your bath exhaust fan for 20 minutes after showers, and make sure bath, kitchen, and dryer vents are not feeding moisture into the attic through the soffits.

Take a bunch of RH readings around the house and in the crawl space and correct them to the same temperature, say 70. that gives you a better comparison. On-line calculators are available for this.

Adding a vapor barrier paint will not do a lot as all paints help, thus what is already there is probably enough. It is the air leakage that is 98% of the moisture path.

Bud
 
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Old 12-07-12, 08:47 AM
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"Hi Halton
glad you have a sense of humor
BTW air is not a liquid
Air is a gas and a fluid but not a liquid"





Thanks for my morning smile.....



.
 
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Old 12-07-12, 08:57 AM
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Tx John and Bud
yes, have a air tight attic hatch. The crawl is dry but no vapor barrier on walls,I could try insulating the walls with ridged ins. and do another inspection from bottom to top for air infiltration
 
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Old 12-07-12, 09:17 AM
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Here is one of the temp, RH, dew point calculators. If you pick up a humidistat, not expensive, and take reading all around the house with temp readings, and then adjust each to one reference temperature, you will get a map that points to the highest moisture area. Take an outside reading as well, as outside air is constantly flowing through the house. This is a bit of low cost detective work that may give you a hint as to the source.

Also, the readings from the crawl space will tell you if it is a contributor. Since the crawl is mostly outside air leaking in, it is not influenced by moisture you are contributing in the house. If the crawl adjusted RH is significantly lower than the house adjusted RH, no further work down there is needed at this time. Insulation is always good. If it is equal or higher, even though it looks dry, it is a source. Since the moisture is evaporating it may not look wet, until it gets to the attic.

Just to double check, soffit vents are substantial, and not just the small round pop-ins. Since the soffits are feeding both gable and ridge vents, they need to be continuous the length of the house on both sides.

Bud
 
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