Moisture in Attic


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Old 01-08-10, 07:08 AM
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Angry Moisture in Attic

I have significant amounts of moisture build-up in my attic. My home is a split level ranch type with 2-car garage under the west-end ot the house. The roof is 4-12 pitch and is approx 75' long. All of the moisture build-up is on the west 1/3 of the attic, and it is significant enough that the underside of the decking is white with frost from the ridge vent all the way to the soffit area. I can see daylight thru the ridge vent and along all soffits between the rafters thru the entire roof. The roof was re-shingled in Aug 2008. Additionally, I had ice damming earlier in the winter in December. I raked off about 3-4' of snow from the roof line, but all that did was move the ice dams up the roof above the water shield, which them migrated under the shingles and leaked along the ceilings and walls. My decking and rafters are wet, but again it is most noticeable on the western 1/3 of the roof. The rest of the roof and attic appear dry. Also, I have (3) bathroom fans that exhaust into the attic, but they are in a portion of the attic where it appears to be dry. I plan on having an energy audit to determine where the moisture/warm air is leaking into the attic. I have identified some areas of conceren: The attic hatchway is not insulated well and the storage room that it is located in is always cool even though it is heated. In fact, the entire western 1/3 of the home stays cooler than the rest of the house. I have approx 16" of fibreglass batt insulation in the attic with the paper side down on the bottom layer to serve as a vapor barrier. I need to solve the moisture issue before I can remove and dry out the insulation and/or add additional vapor barrier/insulation, etc., etc.., but I haven't seemed to identify the "smoking gun" or main cause of the problem. Beyond this, the mold on the western 1/3 of the house is significant, maybe not a concern in the winter, but certainly will be when it gets above 50deg. Some of the plywood 4x8 sheets are black, as are the rafters about 1" into the wood where they join the decking! Where do I begin?
 
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Old 01-08-10, 07:24 AM
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1st you must get bath fans vented to the outside. This is most likely were most of your issue is. 2nd what is the RH in the home?
 
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Old 01-08-10, 08:22 AM
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Smile Moisture in Attic

Originally Posted by airman.1994
1st you must get bath fans vented to the outside. This is most likely were most of your issue is. 2nd what is the RH in the home?
Thanx for the quick response, I agree totally with getting the bathroom exhausts done, and am planning on venting these thru the soffits. The RH in the home is around 30% depending upon the room you are in. The RH in the attic mirrors the outside after it stabalizes. I was just in the attic and the temp is now 36 (f) with an outside temperature of around 20. The RH in the attic presently is 86% with an outside air RH of 65% according the the Weather Channel. The frost is currently turning to moisture and is only visible along the western gable end of the house.
 
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Old 01-08-10, 08:52 AM
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Venting through the soffit is not a good idea if you have soffit and ridge vents. The moist warm air will just be drawn back in.

Go straight out the roof..its not much more work.

Episode | Show Descriptions/Products & Services | Ask TOH | TV | This Old House Funny, this was just on in the last few weeks.
 
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Old 01-08-10, 09:08 AM
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When writing about humidity the figures mean nothing unless they are coupled with the relevant temperature.
For example 99% humidity at a temperature of 86°f is as wet as it gets – humidities only experienced in places like Singapore.
On the other hand at a temperature of 36f and a humidity of 86%, the humidity is so low it is irrelevant. There is so little water vapour in the air that it is to all intents dry.
Once temperatures get below 40f even saturated air at 99% humidity only holds about 5 grams/cc of water vapour per cubic metre and there are a million cc in a cubic metre.
At zero f and below you cannot find the water vapour.

Buy yourself a Weather Station with an external Hygrometer, or two (preferably) place one outside and the other in the attic, then you can see at a glance what is happening.

Humidity is made by people!
Humidity is the water vapour you and your family put into the air by, cooking, washing, drying things on radiators, breathing.
Keeping the kitchen and bathroom doors closed and “not” using your existing extractor fans will help the situation, especially if you open the windows while cooking and after washing.
Water vapour is able to move between the molecules of air and is attracted to cold things and areas of low pressure.
Do you have a badly fitted trap door into the attic, or perhaps you leave it open at times?
Are there holes and cracks in the ceilings where the water vapour can be sucked into the atic?
Then the water vapour in your home rises into the attic and condenses onto the first cold surface it comes to.
In the normal way a bathroom and kitchen are vented to the outside.
When you replace your existing extractor fans buy fans with a integral heat exchangers, preferably with a built in humidistat/hygrometer, which being automatic will come on when required and vent your water vapour to the outside.
 
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Old 01-08-10, 09:48 AM
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Not much to add, but you definitely need to vent those fans out through the roof or gables. Do you bring a lot of snow inside the garage with your vehicles? Garage is west end, moisture is west end??? Look for vent pipes or chimneys and the openings around them.

Ice dams are caused by heat in the attic and can be related to the moist air that is causing the frost. A solution may fix both problems.

Are your soffit vents continuous or just an opening every few feet?

Are all rafter bays open to the attic, noy blocked by insulation?

Here is a link to help: http://www.efficiencyvermont.com/ste...ide_062507.pdf

Bud
 
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Old 01-08-10, 04:30 PM
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Smile soffit vents

Originally Posted by Gunguy45
Venting through the soffit is not a good idea if you have soffit and ridge vents. The moist warm air will just be drawn back in.

Go straight out the roof..its not much more work.

Episode | Show Descriptions/Products & Services | Ask TOH | TV | This Old House Funny, this was just on in the last few weeks.
Actually, that makes perfect sense and I will have the contractor go out thru the roof. I was simply trying to prevent another potential leak source down the road, but what you say makes good sense, thanx!
 
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Old 01-08-10, 04:48 PM
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Smile Moisture in Attic

Originally Posted by Bud9051
Not much to add, but you definitely need to vent those fans out through the roof or gables. Do you bring a lot of snow inside the garage with your vehicles? Garage is west end, moisture is west end??? Look for vent pipes or chimneys and the openings around them.

Ice dams are caused by heat in the attic and can be related to the moist air that is causing the frost. A solution may fix both problems.

Are your soffit vents continuous or just an opening every few feet?

Are all rafter bays open to the attic, noy blocked by insulation?

Here is a link to help: http://www.efficiencyvermont.com/ste...ide_062507.pdf

Bud
We do bring in lots of snow & ice, we drive 2 full size vehicles and do not have a floor drain, so the water pools towards the door. To make matters worse, we have our dryer vented into the very same garage. Above this garage are 2 bedroom and the storage room, with the attic access hatch located in the storage room. These rooms are always cooler and more humid than the rest of the house, I guess that shouldn't be a surprise considering all of the moisture down below. This may well be the "smoking gun" and I will take steps to get it corrected immediately. As to any other vent pipes or chimneys, there is only the stinkpipe and it is high and dry, located approximately 35' east of the problem area. The soffit ventilation is another potential problem. I have aluminum soffits that have small stamped piercings in every 3rd panel, in other words, 1/3 of the soffit area is ventilated, 2/3 is not. I don't think this is enough for a roof area of 75' x 40' (approx). I have an Owens-corning SureVent ridge vent on the roof ridge, but am not sure of the amount of openings - I can see daylight between all rafters and in the area of the ridge vent on both sides. I also have baffles between each set of rafters that keep the insulation from blocking the airflow. On the west side of the house, there is frost from the top of the ridge to the soffits, top to bottom, this morning as it was below freezing in the attic. thanx for your great response!
 
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Old 01-08-10, 04:57 PM
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Smile Moiture in attic

Originally Posted by Perry525
When writing about humidity the figures mean nothing unless they are coupled with the relevant temperature.
For example 99% humidity at a temperature of 86°f is as wet as it gets – humidities only experienced in places like Singapore.
On the other hand at a temperature of 36f and a humidity of 86%, the humidity is so low it is irrelevant. There is so little water vapour in the air that it is to all intents dry.
Once temperatures get below 40f even saturated air at 99% humidity only holds about 5 grams/cc of water vapour per cubic metre and there are a million cc in a cubic metre.
At zero f and below you cannot find the water vapour.

Buy yourself a Weather Station with an external Hygrometer, or two (preferably) place one outside and the other in the attic, then you can see at a glance what is happening.

Humidity is made by people!
Humidity is the water vapour you and your family put into the air by, cooking, washing, drying things on radiators, breathing.
Keeping the kitchen and bathroom doors closed and “not” using your existing extractor fans will help the situation, especially if you open the windows while cooking and after washing.
Water vapour is able to move between the molecules of air and is attracted to cold things and areas of low pressure.
Do you have a badly fitted trap door into the attic, or perhaps you leave it open at times?
Are there holes and cracks in the ceilings where the water vapour can be sucked into the atic?
Then the water vapour in your home rises into the attic and condenses onto the first cold surface it comes to.
In the normal way a bathroom and kitchen are vented to the outside.
When you replace your existing extractor fans buy fans with a integral heat exchangers, preferably with a built in humidistat/hygrometer, which being automatic will come on when required and vent your water vapour to the outside.
Thanks for the detailed explanation of humidity and temperature. You are right on in the explanation and I have taken your advice to purchase a weather station. I currently have it hooked up with the station in the bedroom and the remote sensor in the attic. I need to put another sensor outside so that I can compare the difference. The attic hatchway is also a problem area that I am currently addressing. It is simply a 1/2" piece of oak panel that has been fitted to the opening with some window casing nailed to the sealing to hold it in place - you simply push it up and out of the way to access the attic. It has 2 pieces of 8" loose batting insulation on top of the board with no weatherstripping. I will add polystyrene insulationboard and weatherstripping to tighten this up right away. We never leave it open. Another area of concern is the garage area located below the main portion of my home, see reply to previous responder. Thanks for your input!
 
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Old 01-08-10, 05:53 PM
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You also need to get that clothes dryer vented to the outside also. That is a BIG source of moist air!!!
 
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Old 01-08-10, 06:17 PM
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Along with all the other very good points...... That soffit venting is probably lacking. Compare the hole pattern to these and figure your NFVA: http://www.fureyco.com/content/image...ng_The_Air.pdf You want about 9 sq.inches per foot of soffit.

Fix the attic access: Energy Savers: Attic Access Insulation and Air Sealing

And air/vapor seal (with a primer vapor barrier paint- .45 perms.)the garage, as mentioned.

Be safe, Gary
 
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Old 01-08-10, 07:03 PM
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Smile Moisture in Attic

Originally Posted by GBR in WA
Along with all the other very good points...... That soffit venting is probably lacking. Compare the hole pattern to these and figure your NFVA: http://www.fureyco.com/content/image...ng_The_Air.pdf You want about 9 sq.inches per foot of soffit.

Fix the attic access: Energy Savers: Attic Access Insulation and Air Sealing

And air/vapor seal (with a primer vapor barrier paint- .45 perms.)the garage, as mentioned.

Be safe, Gary
Thanks for the excellent feedback - just got back from Home Depot with insulation and weatherstripping for the access hatch. Good common sense articles you linked to as well. I have come to the conclusion that I have insufficient soffit venting/ridgevent combination. I think the ridge vent is ok, but the soffits are not letting enough air thru to properly vent the moisture out of the attic. I also need to solve how the moisture is getting into the attic, and I think that the combo of the bath fans, lack of vapor barrier, attic hatch, poor ventilation, etc., etc., cause ice dams, which create leaks, which create moisture and lot's of it, which create mold and lot's of it! Thanks for the great help all of you!!
 
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Old 01-09-10, 05:55 AM
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Stopping an ice dam, making your home warm.

I read your blog to Bud and noted the dryer vented into the garage – perhaps you can extend the pipe to the outside?

Once you have solved the problem areas, where the water vapour is produced, then there will not be a need to address the vents in the roof as these will then be more than able to cope with the small amount of water vapour produced in normal living.

Going back to your original blog.

Ice dams are caused by warm air rising through the home, making its way through the insulation in the atic, warming the roof and melting the snow.

The overhang, round the home stays cold, as it has cold air both below and above, and this traps the melted snow on the warm roof, and of course the water finds its way into the home.

The solution to this is effective insulation between the joists of the ceilings and a layer of insulation below the ceiling.

When you lay insulation between the joists, it leaves the joists themselves as the weak link in your insulation. Wood is not a good insulator and it conducts the heat from your home into the roof – causing the snow to melt.

Traditional insulation's fibre glass and cellulose are to be honest, useless, as the warm air moves through these.

The best available insulation is polystyrene, polystyrene is a closed cell product, that is both wind proof and waterproof.

If you fit sheets of polystyrene between the joists right across the cold part of the attic, about four inches (more is better) thick will do. Make sure they are a tight fit, cutting them by hand with a knife saves a lot of mess.

Then the messy part. Pull down the ceilings and fit closely butted two inch thick sheets of polystyrene across the ceilings wall to wall. Then finish as you wish.

This last layer of polystyrene will keep the heat in the rooms, make the home a lot warmer and stop the snow from melting. Plus it will reduce your heating bill considerably. Perfect!
 
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Old 01-09-10, 08:12 AM
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Perry...
Do you really think the average person is going to pull down all the sheetrock on their ceilings, lower the ceiling by 2 inches with the poly, extend all the electrical and venting, then reinstall sheetrock? It's just not realistic unless you were doing a bare to the studs remodel or in new construction.

Could you layer poly over the existing surface..then install sheetrock over that...wouldn't the benefit be the same or even better?

Air sealing, vapor barriers, poly where you can..etc etc...I agree all make great sense and can be easily done over time.
 
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Old 01-09-10, 08:35 AM
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Balloon Framing and Stack Effect: Is open cell foam the answer?

sorry! didn't mean to post here.
 

Last edited by wavy_glass; 01-09-10 at 08:36 AM. Reason: accidental post
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Old 01-09-10, 10:36 AM
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Perry...
Do you really think the average person is going to pull down all the sheetrock on their ceilings, lower the ceiling by 2 inches with the poly, extend all the electrical and venting, then reinstall sheetrock? It's just not realistic unless you were doing a bare to the studs remodel or in new construction. etc;

You are right of course! And yes it can be done your way!

On the other hand there are some very clever people out there..........who given the opportunity. And the information... will get stuck in and then enjoy the benefits. Once they know what can be done, what better way of passing a summer.....sorting out a room and then sitting in the middle of winter..enjoying the comfort........and the thought of those miniscule heating bills in the future! ..
 
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Old 01-09-10, 12:56 PM
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Question Moisture in Attic

Originally Posted by Perry525
I read your blog to Bud and noted the dryer vented into the garage – perhaps you can extend the pipe to the outside?

Once you have solved the problem areas, where the water vapour is produced, then there will not be a need to address the vents in the roof as these will then be more than able to cope with the small amount of water vapour produced in normal living.

Going back to your original blog.

Ice dams are caused by warm air rising through the home, making its way through the insulation in the atic, warming the roof and melting the snow.

The overhang, round the home stays cold, as it has cold air both below and above, and this traps the melted snow on the warm roof, and of course the water finds its way into the home.

The solution to this is effective insulation between the joists of the ceilings and a layer of insulation below the ceiling.

When you lay insulation between the joists, it leaves the joists themselves as the weak link in your insulation. Wood is not a good insulator and it conducts the heat from your home into the roof – causing the snow to melt.

Traditional insulation's fibre glass and cellulose are to be honest, useless, as the warm air moves through these.

The best available insulation is polystyrene, polystyrene is a closed cell product, that is both wind proof and waterproof.

If you fit sheets of polystyrene between the joists right across the cold part of the attic, about four inches (more is better) thick will do. Make sure they are a tight fit, cutting them by hand with a knife saves a lot of mess.

Then the messy part. Pull down the ceilings and fit closely butted two inch thick sheets of polystyrene across the ceilings wall to wall. Then finish as you wish.

This last layer of polystyrene will keep the heat in the rooms, make the home a lot warmer and stop the snow from melting. Plus it will reduce your heating bill considerably. Perfect!
I just had a contractor up in the attic reviewing the area. His assessment is that the cold/moisture is seeping up thru the walls (exterior) due to poor insulation or no insulation over the sill plate. He recommends removing all of the batting insulation and putting spray foam polystyrene insulation at R-49 value in it's place, thereby providing adequate insulation, sealing up all of the cracks, voids, etc., and providing a vapor barrier at the same time. In addition, vent the dryer outside thru garage wall, vent bathroom fans thru roof, although he felt soffit should work equally as well. He also gave me tips on insulating the access hatch for the attic.
 
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Old 01-10-10, 03:03 AM
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Your guys assessment of the situation is interesting.
Obviously the cold is outside after all that's where it is.
However he is wrong in saying that the cold is coming in through the walls.
The laws of nature are that hot always moves to cold.
As for the moisture coming up through the walls from the outside, well that is also wrong, as again water vapour which is a very fine gas always moves from hot to cold and from areas of high pressure to areas of low pressure. The water vapour is indeed rising within the walls but only after escaping from the comfort zone inside the home where it is created.
It you think about it for a moment, you will have noticed (if you are up early enough) that about two hundred times a year you have a frost or a morning where the ground is covered in dew.
What happens is that the ground is cold and an area of warm wet air moves in, the ground cools the air, the water vapour drops out as frost or dew. You may have frost on the outside greenhouse or your car but, it does not come indoors.
The vapour barrier is an interesting one.
A external barrier to keep out the wind and rain is always a good idea, a barrier that is water vapour permeable is even better – as it stops the wind and rain from entering the wall and at the same time allows the water vapour that always starts inside the home, where it is warm to move through the wall on its journey to the cold outside.
The idea of sealing the outside ie: with spray on foam is good as it will indeed seal all the holes in the wall and therefore make the home warmer, but the foam should be sprayed on the inside of the outer wall covering to work, not on the outside of the inside wall.
The recommendation of recent times is that the water vapour produced inside the home, should be kept inside the comfort zone and not allowed to move inside the walls.
The recent practice of filling walls with fibre glass and similar things has been proven wrong as water vapour moves into these types of insulation, gets towards the outside where it is cold and then freezes, when the outside warms up the ice inside the fibre glass melts and makes the fibre glass wet. Wet fibre glass provides an express route out for your expensive heat and makes the installation a liability rather than an asset.
That is why things are changing.
 
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Old 01-10-10, 03:25 AM
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Hi Perry, "The recent practice of filling walls with fibre glass and similar things has been proven wrong " That needs a little more explanation, as all fiberglass in walls does not get soaked with water from moisture. The statement, I believe, is an isolated combination of vapor barrier and not enough foam insulation on the outside, essentially placing a vb on the outside.

Bud
 
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Old 01-10-10, 06:20 AM
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Bud you are right of course!
There are many types of building, of different ages, built by people with varying skills.
On top of which there are people who take a shower and the room is full of steam, and then they leave the door open, and others where you wouldn't know they'd had a shower. Some boil a kettle with a cup full of water and others fill the kettle and forget it.
All this makes a difference.
The key thing is that polystyrene being a closed cell structure does not allow either wind or water to affect its insulation properties, whereas other things like sheetrock are basically transparent to water vapour and while this is good in the case of fire, holding back the flames for 30 minutes, it does not help keep a home, roof, wall dry.
 
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Old 01-10-10, 10:19 AM
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Question

Originally Posted by Perry525
Your guys assessment of the situation is interesting.
Obviously the cold is outside after all that's where it is.
However he is wrong in saying that the cold is coming in through the walls.
The laws of nature are that hot always moves to cold.
As for the moisture coming up through the walls from the outside, well that is also wrong, as again water vapour which is a very fine gas always moves from hot to cold and from areas of high pressure to areas of low pressure. The water vapour is indeed rising within the walls but only after escaping from the comfort zone inside the home where it is created.
It you think about it for a moment, you will have noticed (if you are up early enough) that about two hundred times a year you have a frost or a morning where the ground is covered in dew.
What happens is that the ground is cold and an area of warm wet air moves in, the ground cools the air, the water vapour drops out as frost or dew. You may have frost on the outside greenhouse or your car but, it does not come indoors.
The vapour barrier is an interesting one.
A external barrier to keep out the wind and rain is always a good idea, a barrier that is water vapour permeable is even better – as it stops the wind and rain from entering the wall and at the same time allows the water vapour that always starts inside the home, where it is warm to move through the wall on its journey to the cold outside.
The idea of sealing the outside ie: with spray on foam is good as it will indeed seal all the holes in the wall and therefore make the home warmer, but the foam should be sprayed on the inside of the outer wall covering to work, not on the outside of the inside wall.
The recommendation of recent times is that the water vapour produced inside the home, should be kept inside the comfort zone and not allowed to move inside the walls.
The recent practice of filling walls with fibre glass and similar things has been proven wrong as water vapour moves into these types of insulation, gets towards the outside where it is cold and then freezes, when the outside warms up the ice inside the fibre glass melts and makes the fibre glass wet. Wet fibre glass provides an express route out for your expensive heat and makes the installation a liability rather than an asset.
That is why things are changing.
Thanks for the feedback, I didn't mean to say that he is saying that the moisture is coming thru the outer walls, but rather that the walls, both outer and inner are allowing warm air to escape into attic area, along with the other factors, garage at that end of the house, lack of vapour barrier, poor insulation for the attic access door, dryer venting and bath exhaust venting, together these are creating the frost that is noticeable from behind the baffles in the soffit area, all the way up to the ridge vent and along the entire west gable area. I am not certain I understand whether you agree or disagree on the spray-on foam? What we were planning on was to remove all of the batting insulation in the attic and completely spray-foam the entire area with the equivelant of R-49 value, thereby not only giving us a vapour barrier, but also sealing up cracks, joists, rafters, etc., along with the additional insulating properties. Do you agree with the approach or disagree, I am confused?
 
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Old 01-11-10, 03:25 AM
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What we were planning on was to remove all of the batting insulation in the attic and completely spray-foam the entire area with the equivelant of R-49 value, thereby not only giving us a vapour barrier, but also sealing up cracks, joists, rafters, etc., along with the additional insulating properties. Do you agree with the approach or disagree?

Your proposal is good.
One question. Intention to spray the underneath of the roof?

Roofs are best treated by fixing polystyrene sheet between the joists. And leaving a one or two inch gap between the polystyrene and the underneath of the roof for any water to run down.

The reason for this is: If you should have a leak at sometime in the future, it will take a long time before the leak shows, by which time a large area of the roof will be rotten. Trying to find where the leak is will involve trying to remove the sprayed on foam – this will not be easy.
 
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Old 01-11-10, 06:24 AM
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Thumbs up Moisture in Attic

Originally Posted by Perry525
What we were planning on was to remove all of the batting insulation in the attic and completely spray-foam the entire area with the equivelant of R-49 value, thereby not only giving us a vapour barrier, but also sealing up cracks, joists, rafters, etc., along with the additional insulating properties. Do you agree with the approach or disagree?

Your proposal is good.
One question. Intention to spray the underneath of the roof?

Roofs are best treated by fixing polystyrene sheet between the joists. And leaving a one or two inch gap between the polystyrene and the underneath of the roof for any water to run down.

The reason for this is: If you should have a leak at sometime in the future, it will take a long time before the leak shows, by which time a large area of the roof will be rotten. Trying to find where the leak is will involve trying to remove the sprayed on foam – this will not be easy.
This makes good sense, one other question is how to get rid of the mold that has built up on the underside of the plywood decking - there is a significant amount of it, particularly on the west 1/3 of the roof area? Do I need to hire a mold abatement service or can this be taken care of myself?
 
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Old 01-11-10, 08:22 AM
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ptho....there's really no need to quote the reply each time. Most people will remember what they wrote...lol.
 
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Old 01-11-10, 11:20 AM
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Mould needs food and water, the food it gets from the cellulose in the wood and the water comes out of the air (for the moment).
Once you have sorted the place the mould will die back.
To speed things up, clean it off with soap and water, or a mild bleach.
You will read a lot of tosh about needing special suits and the dangers of mould.
Mould spores are everywhere from the North to the South poles, we live with them all the time. They only settle and grow where the conditions are right for them - otherwise everywhere would be covered in mould.
 
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Old 01-11-10, 03:10 PM
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Red face Protocol

Originally Posted by Gunguy45
ptho....there's really no need to quote the reply each time. Most people will remember what they wrote...lol.
Sorry, being new to this website I am unfamilar with the protocol. Perhaps you can give me a quick lesson on how I do reply without adding the quote? I have been clicking on the quote button, should I be hitting a different one?
 
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Old 01-11-10, 03:44 PM
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No prob...I knew that. The "post reply" is at the top of the thread, just below the general topic...or the "quick reply" down near the "quote" button, in the post you are replying to. They look like a roll of parchment with a quill pen?

The first gives you access to more features like smileys..the second is basically just text..but still allows editing, pictures, and such.

Might look a bit different depending on your browser and how you have the view set up.

Wasn't criticizing...just informing..
 
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Old 01-12-10, 10:27 AM
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Thumbs up Protocol

Thanks for the quick lesson, I didn't take it as criticism, just someone trying to help me, again! Now if I can get my attic issue solved that quickly! I have a guy coming Friday, along with the contractor that reviewed the attic, to give me an estimate for removing the batt fibreglass insul and putting down spray-foam. Not sure if there are any issues with doing this in the winter, temps currently are in the low 20's here, but from what I know, it can't hurt. I suppose the attic will dry out on it's own after we cure the moisture problem. I don't imagine this will be cheap, but it needs to be done.....again, thanks to you and everyone else for your responses.
 
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Old 01-12-10, 10:33 AM
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Question Mold Clean-up in Attic

Thanks for the info on mold. Do you see any issue with spraying a mixture of bleach and water 50:50 in the attic now during winter or should I wait until spring when it is warmer? Is the mixture too strong?? I'm not worried about protective clothing, might wear a facemask due to the bleach, but other than that, not worried about it. If I ever decide to sell the house down the road, this has to be cleaned up and for health reasons alone, my wife is ready to move out already, I keep assuring her that it is in an area that is closed off with plastered walls and ceilings, but...............well, to keep the piece, I need to get it cleaned up quickly.
 
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Old 01-12-10, 11:10 AM
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I wont comment on the cause of your problems with moisture, but I can tell you that venting a bath fan through the soffit to the outside is more than adequate, and done all the time and approved by inspectors if you think about it that fan motor will easilly push the air through and out its not getting back in. secondly, your only exhausting a little steam from the shower and unwanted odors I would not penetrate the roof unless absolutely necessary for example vent tubes for plumbing pipes, any penetration is a potential for possible water leak problems not near worth it.Beer 4U2
 
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Old 01-12-10, 11:30 AM
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I measured the attic area (65' x 30') and the soffit area. The soffits are 65' long on both sides of the roof area - the aluminum soffit panels are made with a vented area consisting of a series of small perforations in the panels approximately 4" x 20". Of course this is not all ventilation because these are just small perforations about 1/2" long and 1/8" wide at best. There are around 120 of these perforations for every 16" of soffit area. On the south side of the house roof, there are 46 of these perforated sections and on the north side there are around 50 - the difference being I have a box window on the south side that extends thru the soffit. I have an Owens Corning Ventsure Ridge Vent that your link indicates is giving me 12.5sq inches of ventilation per linear foot - this vent is approximately 60' long - it does not go all the way to the gables on either end of the roof. Based on all of this, if I did the math correctly, I should have adequate ventilation in the attic, do you agree or did I not calculate this correctly?
 
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Old 01-12-10, 12:17 PM
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Actually, after re-calculating, it would definitely appear that I have 75% of my ventilation at the ridge vent and only 25% at the soffit area, meaning I need to add substantial soffit ventilation. Do you agree?
 
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Old 01-12-10, 01:14 PM
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IMO, you have identified several serious moisture issues, garage, bath vents and dryer vent. I would first correct those and then check the attic. Although your numbers may be technically a bit low, that is better than most and with most, there is no condensation.

Air sealing leaks into the attic will help on heating costs and moisture. In fact, attention to details on the sealing would reduce the ventillation requirements, so that would be a better place to put your time and money. Again IMO.

Bud
 
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Old 01-12-10, 01:43 PM
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Originally Posted by Road King
... venting a bath fan through the soffit to the outside is more than adequate, and done all the time and approved by inspectors if you think about it that fan motor will easilly push the air through and out its not getting back in.
In my opinion - and around 75% of my "troubled building" consulting involves moisture intrusion problems - "code compliance" is a very poor basis on which to access the adequacy of insulation, ventilation, air barriers, etc. For example its likely that in this case the AHJ issued a certificate of occupancy despite the fact as we know based on the evidence that in combination they are insufficient to prevent moisture problems at this property.

---------

Real world, the problems with soffit vents as compared with roof vents usually involve installation issues, including:

1) They often involve longer runs that through-roof vents.

2) By their nature, they involve horizontal runs.

3) They are more often run in flexible ducts.

4) These three conditions mean that they are usually much more subject to low spots and other causes of condensation problems.

5) Because they are on the attic floor, and usually in flexible duct, they are considerably more likely to experience mechanical damage.

6) Under a 4/12 roof it will be somewhere between difficult and impossible to correctly install the duct and terminations, during my inspections this is a very common location at which to find disconnected or damaged ducting.

The bottom line is that assuming a properly pitched vent is run in properly insulated hard pipe and correctly and permanently connected to a properly installed termination, and as long as the attic is not negatively pressurized (for example by a powered attic ventilation fan) and exhaust air is not drawn back in through the soffit vents, then a soffit vent is fine - but at least in my area (Chicago) the chances of finding such an installation are pretty slim.

Originally Posted by Road King
... secondly, your only exhausting a little steam from the shower and unwanted odors...


Fig 1 "A little steam" observed at a winter inspection here in Chicago.
 
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Old 01-12-10, 01:52 PM
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Thanks for the good response, I have made my mind up and am going thru the roof as originally planned. Yes, it is another potential leak down the road, but I believe the trade-off is worth the risk if done correctly and I have faith in my contractor.
 
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Old 01-12-10, 01:59 PM
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Thanks and I agree wholeheartedly with you and the others. And now for another question: Assume that I plan on venting the exhaust fans thru the roof, the dryer vent thru the wall to the outside, correctly insulate and seal the attic access hatch. What is the liklihood that I would solve the moisture issue simply by adding a 3rd layer of 8" batting fibreglass insulation over the existing 2 layers? Would that cure the problem, it might not be the best solution, but it probably would be considerably cheaper than removing all of the insulation and putting in spray-on foam poly? Just a question hoping for response(s).
 
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Old 01-12-10, 03:05 PM
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The spray foam or dense pack cellulose do offer better air sealing, but if you dig around and seal what you can find, plumbing vents, around any chimneys, (review the thread on air sealing to be sure there isn't a big leak hiding somewhere), then you should be good enough to take a chance on what you have. Note, what you have. Adding more insulation prevents heat loss which is a cause of ice build up. So add the insulation if that is an issue.

I think you will have enough winter left to see how the moisture issue evolves. If it goes away, then re-group and decide the merits of your next options.

Bud
 
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Old 01-12-10, 03:39 PM
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I think that is good advice - I believe the moisture is being caused from condensation because I just don't have enough insulation in the attic. Add to that, the moisture from the unvented bathroom exhausts, dryer vent and the fact that I know I had water coming in under the shingles earlier due to the ice dams, and I believe the moisture issue will go away by adding an additional layer. If I don't see any improvement, I can still go with the spray-on foam poly this spring or later during the winter. It's worth a shot. Thanks again for all everyones help and stay tuned.........!
 
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Old 01-12-10, 04:10 PM
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Just to review again. The condensation is not caused by a lack of insulation. It is caused by the cold temperatures outside cooling the roof and then the moist air in the attic contacts the roof and cools to the dew point and deposits its water. Eliminating the sources of the moist air/moisture, such as the exhaust fans, air leakage into the attic (which carries a lot of moisture), water in the garage (which is drawn into the frame of the house by stack effect), and the dryer, will reduce or eliminate the condensation.

The ice dams could have contributed, and they can be reduced by more insulation AND the air sealing which not only reduces the moisture but the heat which is causing the snow melt and ice dams.

So, adding the insulation is good for the ice dams and therefore may also help with the condensation. But, air seal, air seal, air seal. And you have got it .

Bud
 
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Old 01-12-10, 04:35 PM
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Talking Moisture in Attic

Bud, you are a gentleman and a scholar and I thank you for all of your valuable input. It is a pretty straightforward task as the attic is quite simple. No chimneys, no additional roof lines, and only (1) current penetration thru the roof (stink-pipe) with (2) more to be added (bathroom exhaust fans) and (1) attic hatch which I have already insulated using previous link suggestion(s). I basically have a 65' x 30' area to add another layer of insulation on. I may even just do 1/3 of the area just to see if it makes a difference (the area I am having the problem with now). I don't think I have much to lose at this point and everything to gain. Thank-you and to everyone for all their fine suggestions. Again, I will keep you all posted!
 
 

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