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Attic Insulation Advice


Briant73's Avatar
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06-02-10, 08:59 PM   #1  
Attic Insulation Advice

Currently pondering the best way to better insulate my attic.

Live in NW, PA in a house built in the 1970s. Have a high eff furnace and ac unit. My guess is Attic is insulated with 6" fiberglass currently. Vents in the roof and sofit (though not as much as it should be). Attic area is accessible with pull down door/folding stairs. When home was inspected inspector suggested adding more insulation and having better ventilation.
Currently attic is used for storage about 1/3rd of it the rest is open and unused, not high enough to stand in but enough room to crawl around in easily. Roof shape is side gabled and i would say low to normal slope.

Getting icicles for sure and ice damns since the addition of gutters with leafguard. Rather not give up leaf guard since our gutters would require cleaning a lot.

So far had two contractors come out and give ideas. Everyone say's it would be easy to do if we didn't want to use it as storage, just blow in insulation and up the ventilation but we want that storage area and their isn't enough space to build a raised floor area.

So the suggestions have been -
1) Frame off directly near attic stairs and blow in insulation everywhere else.
2) Spray Foam (open cell .5lb) around 5.5 inches covering the underside roof and rafters and pretty much seal off the attic making a condition space. (one uses SEALECTION 500)

The second solution sounds better but costs a bit more and I have read there could be issues with - Smell, moisture/breathing issues, and possible heat of the shingles.

I'm a novice at this and the more reading I do the more confused I am getting so any suggestions or advice?

 
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06-03-10, 03:14 AM   #2  
Energy Savers: Construct an Attic Stairs Cover Box

This is a link that shows you how to insulate your pull down attic stairs.

The conditions that must exists for Ice Dams to occur are:
1. There must be snow on the roof.
2. The outside temperature must be below freezing
3. The temperature in the attic must be above freezing.

While inadequate ventilation may cause ice dams to occur because its function is not only to extract moisture from the attic but also to keep the temperature in the attic the same as the temperature outside during the winter, it is a less common cause for ice dams. A more common cause for ice dams is known as the "Attic By-pass Phenomena".

The two most common causes of this are uninsulated/poorly sealed attic entrances and bathroom exhaust that terminate in attics. In your case it may be heat from the house accesses the attic through your pull down stairs causing the temperature in the attic to rise above freezing. Though this is a common cause for ice dams, the most common cause is bathroom exhaust into attics. This is because the amount of heat energy that is released when moisture vapor condenses, which can easily raise the temperature in the attic. This is known as the "Latent Energy of Vaporization".

Adding more insulation to your attic is advisable but you must address the source of the ice dams first and adding more insulation does not.

 
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06-03-10, 05:56 AM   #3  
Posted By: resercon Energy Savers: Construct an Attic Stairs Cover Box

This is a link that shows you how to insulate your pull down attic stairs.

The conditions that must exists for Ice Dams to occur are:
1. There must be snow on the roof.
2. The outside temperature must be below freezing
3. The temperature in the attic must be above freezing.

While inadequate ventilation may cause ice dams to occur because its function is not only to extract moisture from the attic but also to keep the temperature in the attic the same as the temperature outside during the winter, it is a less common cause for ice dams. A more common cause for ice dams is known as the "Attic By-pass Phenomena".

The two most common causes of this are uninsulated/poorly sealed attic entrances and bathroom exhaust that terminate in attics. In your case it may be heat from the house accesses the attic through your pull down stairs causing the temperature in the attic to rise above freezing. Though this is a common cause for ice dams, the most common cause is bathroom exhaust into attics. This is because the amount of heat energy that is released when moisture vapor condenses, which can easily raise the temperature in the attic. This is known as the "Latent Energy of Vaporization".

Adding more insulation to your attic is advisable but you must address the source of the ice dams first and adding more insulation does not.
I do have to vent the bathroom vent (been suggested side gable), as to the stairs I can do that or is the Owens Corning solution a good one to try? Also what about lights/fans that are installed for the floor below but sit on the attic floor?

 
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06-03-10, 06:12 AM   #4  
I should of added this in my first response -

I was also told adding 5.5 inches of .5lb open cell spray foam (sprayed under the roof decking and covering the rafters) could do these things for me

Claims it will make us hit the r-50 performance level recomended for our region even though the math says it's only r-20 or so. Would remove the need to seal off the attic stairs and/or lights and extra ventilation for the area would not be needed.

Now of course my concerns are - Will it cause moisture issues, could it lessen the life of the roof decking/rafters wood? Might I have an odor issue from that point on cause of the foam?

 
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06-03-10, 07:54 AM   #5  
Attic ventilation is a misnomer. What attic ventilation does is by-pass the low vapor permeability of your roofing shingles. In other words, roofing shingles are designed to keep moisture out of the attic that same moisture function of shingles prohibits moisture in the attic from leaving. If you spray the underside of the roof decking, you defeat the purpose of attic ventilation. Please keep in mind that all building materials must maintain a certain amount of moisture to remain stable, especially structural components and roof decking is a structural component.

"Battic Door" is something you can search for the cover the stairs, but building one is simple.

Recess lights are also a major source for ice dams. If these lights are "IC" rated (should say on the can) then you can air seal the lights. This is done in much the same way the stairs are done. You make a box out of rigid board insulation that is large enough to keep a distance of 3 inches from the light on all sides. Place it over the recess light and spray foam it in place to make it air-tight.

 
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06-03-10, 08:24 AM   #6  
Posted By: resercon Attic ventilation is a misnomer. What attic ventilation does is by-pass the low vapor permeability of your roofing shingles. In other words, roofing shingles are designed to keep moisture out of the attic that same moisture function of shingles prohibits moisture in the attic from leaving. If you spray the underside of the roof decking, you defeat the purpose of attic ventilation. Please keep in mind that all building materials must maintain a certain amount of moisture to remain stable, especially structural components and roof decking is a structural component.

"Battic Door" is something you can search for the cover the stairs, but building one is simple.

Recess lights are also a major source for ice dams. If these lights are "IC" rated (should say on the can) then you can air seal the lights. This is done in much the same way the stairs are done. You make a box out of rigid board insulation that is large enough to keep a distance of 3 inches from the light on all sides. Place it over the recess light and spray foam it in place to make it air-tight.
I have found the Battic devices and may just get one of them, though the box idea is good too. I definitely need to get the bathroom fan vented outside and sealed up better.

So are you saying spray foaming might lead to possible issues with the structure? I believe open cell foam is supposed to allow some moisture to go through but again I'm going of what I have read. Just want to make sure I understand everything because I rather pay a bit more in heating/cooling bills than have to spend money repairing my roof (other than shingle replacement at the normal time).

 
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06-03-10, 09:15 AM   #7  
Just to add to what resercon is saying, my normal advice is to stay with the traditional vented attic, unless there is no other reasonable option. Unfortunately the sales force promoting sealed attics like what you are hearing may use unfounded statements like "it will make us hit the r-50 performance level recommended for our region even though the math says it's only r-20 or so". Give me a break! Remember, their first and probably only objective is to sell their product. Yes, there are applications where the underside of the roof and gables are insulated with spray foam, but since the exposed area increases by over 50% (gables plus slope) you need 50% more insulation to just get back to where you want to be. Since your attic is not sealed, you technically can't include the insulation you have in the calculation to reach that R-50. So, instead of the 4" they are talking about, you will need more like 14". And, it will be some independent energy auditor 10 years from now who says, "who ever told you that 4" of foam was R-50 must have been a salesman?" Too much sales pitch and not enough facts.

By staying with the traditional approach of insulating your attic floor and installing the correct ventilation, you know it will work and there will be no surprises 20 years down the road.

If you want to keep the area you have for storage, do an extra good job of air sealing, install barricades to allow you to over insulate the rest of the attic, seal and insulate those pull down stairs, and you're all set. leave the storage area as it is. If you or the next owner feel you need those last few BTUs escaping where you have the storage, it can easily be done and the savings can be calculated in advance to tell you if it is worth the effort.

Bud

 
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06-03-10, 10:11 AM   #8  
Posted By: Bud9051 Just to add to what resercon is saying, my normal advice is to stay with the traditional vented attic, unless there is no other reasonable option. Unfortunately the sales force promoting sealed attics like what you are hearing may use unfounded statements like "it will make us hit the r-50 performance level recommended for our region even though the math says it's only r-20 or so". Give me a break! Remember, their first and probably only objective is to sell their product. Yes, there are applications where the underside of the roof and gables are insulated with spray foam, but since the exposed area increases by over 50% (gables plus slope) you need 50% more insulation to just get back to where you want to be. Since your attic is not sealed, you technically can't include the insulation you have in the calculation to reach that R-50. So, instead of the 4" they are talking about, you will need more like 14". And, it will be some independent energy auditor 10 years from now who says, "who ever told you that 4" of foam was R-50 must have been a salesman?" Too much sales pitch and not enough facts.

By staying with the traditional approach of insulating your attic floor and installing the correct ventilation, you know it will work and there will be no surprises 20 years down the road.

If you want to keep the area you have for storage, do an extra good job of air sealing, install barricades to allow you to over insulate the rest of the attic, seal and insulate those pull down stairs, and you're all set. leave the storage area as it is. If you or the next owner feel you need those last few BTUs escaping where you have the storage, it can easily be done and the savings can be calculated in advance to tell you if it is worth the effort.

Bud
Both quotes have recommended foam under the deck, over the expose roof rafters and the side gables and sealing down to wall level. I believe both are saying 5 and half inches under the roof. If it's open cell it seems to be about 19-22 R value.

 
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06-03-10, 11:19 AM   #9  
I do not agree with insulating the underside of a roof for several reasons. Just to mention a few;

1. Perm Ratings of the 3 materials non-conducive. Roofing shingles will have the lowest, roof decking will have the highest and the open cell foam will have one higher than the shingles, lower than the decking.

2. Insulation retards heat flow and in this process the insulation retains heat. When the sun goes down in the summer because of this and #1 "Dew Point Temperature" is highly probable in decking

3. Insulation under roof decking causes shingles to reach higher temperatures than manufacturer's recommendation. This temperature causes the shingles to expand more than normal. This results in the loss of granules on the shingles. These granules have a single purpose and that is to reflect UV light. The loss of the granules on shingles dramatically reduces the life expectancy of the shingles.

4. Roof decking is "Load Bearing". The condition of the decking determines the ability to disperse Live and Dead Loads.

I can go on and on, but I hope you are getting my point.

 
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06-03-10, 12:54 PM   #10  
I think I will go over everything again and maybe call one or two more insulators in for ideas then. I do get a lot of ice in the winter especially since adding leafguards to my gutters.

The foam solution according to the salespeople sounds like it would solve all the issues but like you say it could some serious new issues.


Last edited by Briant73; 06-03-10 at 01:17 PM.
 
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06-03-10, 06:15 PM   #11  
I'm surprised this hasn't been mentioned yet. For the area where you want to use as storage, lay foam sheets down to get your desired R value. Put batts or blown in the joist bays below. Then you can have your subfloor on top to store items. Use blown insulation in the rest of the attic.

 
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06-03-10, 06:52 PM   #12  
Posted By: drooplug I'm surprised this hasn't been mentioned yet. For the area where you want to use as storage, lay foam sheets down to get your desired R value. Put batts or blown in the joist bays below. Then you can have your subfloor on top to store items. Use blown insulation in the rest of the attic.
Currently the storage area has I believe fiberglass batt down and plywood on top of it. Are you suggesting pulling the plywood up, throw down some foam sheets and then some fiberglass and then the plywood? I believe I have only 5-6" of space.

 
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06-03-10, 07:10 PM   #13  
I was thinking you pull up the plywood, leave what is there as long it fills the cavity and put foams sheets down over the joists. Then put the plywood back down.

 
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06-03-10, 07:40 PM   #14  
Posted By: drooplug I was thinking you pull up the plywood, leave what is there as long it fills the cavity and put foams sheets down over the joists. Then put the plywood back down.
That may be doable, what kind of foam sheets were you thinking? I see a lot of different kinds and thickness. Also the insulation in there is probably original with the house, is it as good as today's 5-6" fiberglass?

 
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06-04-10, 10:05 AM   #15  
The blue or pink rigid foam. The stuff that has the silver coating on it is a vapor barrier and you want to avoid that. The thickness depends on your R value needs. I believe it runs about R-6 per inch.

I would replace the current insulation if it started to fill with dirt or if you have room to get a thicker batt installed. I would probably just replace it with the blown in cellulose if I decided to go that way.

 
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06-09-10, 12:00 PM   #16  
Radiant Barrier Foil Insulation Do-It-Yourself Radiant Barrier Tips
Cheapest, easiest solution to keep the heat out. Add insulation after installing foil.

 
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06-10-10, 10:38 AM   #17  
Bryant This is the second time your have raised this project, ( although you have provided more information this time) and it looks like you have hit the jackpot , with many and varied ideas.

Lets go to basics, the idea of insulating, is to be comfortable at a lower cost, without damaging the building.

Ice dams are caused by warm air rising from the home, moving through the 6" of useless fiberglass insulation, crossing the attic space, warming the roof and melting the snow.

The snow on the overhang stays cold and stuck to the roof, the melted snow as water backs up and enters the roof.

The solution is simple either turn the heating off, or use some sensible form of insulation that does not allow the warm air to pass through it and melt the snow. And insulate that pull down door and make sure its airtight, and build an insulated box over it to keep the heat in the home and not allow it to escape to the sky.

Contractors are basically lazy people, they only want to do things that make them money and are easy to do.

They are not interested in doing a proper job, as this will be difficult to do, messy, and expensive.

Insulating a roof (properly) is time consuming awkward and best done DIY.

The best way to insulate, is to keep the insulation as close to your warm air as possible, this means removing the dry wall, and replacing it with polystyrene sheets.

Please be aware that most of your heat is escaping through the drywall and then through the fiberglass (so called insulation) but, also be aware that the wood framing makes up about 40% of your ceiling and wall surfaces, and this amount of wood provides a very significant heat loss by both conduction and convection.

The way to do this is to empty the attic, then close board it with 3/8" waterproof plywood, screwed down. Try to avoid leaving any holes.

Then pull the drywall off the ceilings and walls, and fill the spaces with sheets of polystyrene, cut to size a tight fit, pushed up from below or from inside the room, taking care to leave no holes. Then fix more sheets of polystyrene at least two inches thick tightly butted on the room side of the framing, followed by replacement drywall.

A total of five inches of polystyrene will raise the room temperature by 6 or 7 degrees f and will mean that there will be many more days and nights that are comfortable, without the heating, or the fan blowing, both of which will cost more to use in future, where the insulation once fitted, will pay for itself over and over.

Spray foam under a roof is not a good idea, it will suit the contractor, its relatively easy to apply, it provides a good air tight seal, it is the best available insulation. But, if the roof should leak?
Then the leak will go unnoticed for years, until the roof has gone rotten and it collapses giving you a very large bill.

The disadvantage you have at the moment is, that water vapour created inside your home, is moving through the drywall and fiberglass of the ceilings and walls into the attic, where it condenses on the cold wood, potentially leading to mould and wood rot.

Polystyrene is both wind proof and waterproof, it will be warm on one side at room temperature and freezing and covered with ice on the other and it will continue to work for the rest of the life of your home keeping you warm in winter and cool in summer.

 
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06-13-10, 06:22 PM   #18  
Posted By: Perry525 Bryant This is the second time your have raised this project, ( although you have provided more information this time) and it looks like you have hit the jackpot , with many and varied ideas.

Lets go to basics, the idea of insulating, is to be comfortable at a lower cost, without damaging the building.

Ice dams are caused by warm air rising from the home, moving through the 6" of useless fiberglass insulation, crossing the attic space, warming the roof and melting the snow.

The snow on the overhang stays cold and stuck to the roof, the melted snow as water backs up and enters the roof.

The solution is simple either turn the heating off, or use some sensible form of insulation that does not allow the warm air to pass through it and melt the snow. And insulate that pull down door and make sure its airtight, and build an insulated box over it to keep the heat in the home and not allow it to escape to the sky.

Contractors are basically lazy people, they only want to do things that make them money and are easy to do.

They are not interested in doing a proper job, as this will be difficult to do, messy, and expensive.

Insulating a roof (properly) is time consuming awkward and best done DIY.

The best way to insulate, is to keep the insulation as close to your warm air as possible, this means removing the dry wall, and replacing it with polystyrene sheets.

Please be aware that most of your heat is escaping through the drywall and then through the fiberglass (so called insulation) but, also be aware that the wood framing makes up about 40% of your ceiling and wall surfaces, and this amount of wood provides a very significant heat loss by both conduction and convection.

The way to do this is to empty the attic, then close board it with 3/8" waterproof plywood, screwed down. Try to avoid leaving any holes.

Then pull the drywall off the ceilings and walls, and fill the spaces with sheets of polystyrene, cut to size a tight fit, pushed up from below or from inside the room, taking care to leave no holes. Then fix more sheets of polystyrene at least two inches thick tightly butted on the room side of the framing, followed by replacement drywall.

A total of five inches of polystyrene will raise the room temperature by 6 or 7 degrees f and will mean that there will be many more days and nights that are comfortable, without the heating, or the fan blowing, both of which will cost more to use in future, where the insulation once fitted, will pay for itself over and over.

Spray foam under a roof is not a good idea, it will suit the contractor, its relatively easy to apply, it provides a good air tight seal, it is the best available insulation. But, if the roof should leak?
Then the leak will go unnoticed for years, until the roof has gone rotten and it collapses giving you a very large bill.

The disadvantage you have at the moment is, that water vapour created inside your home, is moving through the drywall and fiberglass of the ceilings and walls into the attic, where it condenses on the cold wood, potentially leading to mould and wood rot.

Polystyrene is both wind proof and waterproof, it will be warm on one side at room temperature and freezing and covered with ice on the other and it will continue to work for the rest of the life of your home keeping you warm in winter and cool in summer.
Not sure when I posted here before since I just joined in June of this year. Saying that I want to say thanks for the advice from everyone.

As to removing the drywall ceilings for the main living floor and then doing what you suggest sounds like a major undertaking as you said.

 
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01-27-11, 05:48 PM   #19  
Been awhile since I posted but now that it's mid winter thought I'd come back with some more information and questions. Still getting ice dams and icicles.

Some quick information about the house mid 70s ranch, probably r-19/20 insulation in the attic, overhangs measure about 22" from the siding.

Steps I have taken - sealing up the bathroom fan better, sealing up the attic stairs better, getting an attic stair cover.

Now the bathroom fan is still vented to the attic area. I want to get this vented outside and soon but I have been told many ways to vent it, started a thread for it actually http://forum.doityourself.com/ductin...l#post1818625I

So today I climbed up into my attic and did my best to figure out how the ends were, it seems from my checking it out best i could (ran out of space to get real close). I pulled a piece of insulation out and what I found is the ceiling (attic floor) below was smooth all the way out, then I could see the edge of the roof in the space where the wall/ceiling stopped. It seems the fiberglass isulation is too close to the edge of the roof. Should I look into new soffit vents with the plastic attic vent pieces also? I also put a thermometer in the attic today when it was 27-28f degrees out and it seemed to be around 40-42 degrees. So am I right in thinking the attic is the culprit?

I wish open cell spray foam didn't have so many unknowns, it seems the easiest solution that would fit our needs for use of the attic area for storage and also for insulation.


Last edited by Briant73; 01-27-11 at 06:32 PM. Reason: Added thread link
 
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01-28-11, 04:00 AM   #20  
Well the time has not been wasted as you now know the cause of the problem, that fan discharging hot air into the attic.
It is good that you have taken the matter up with various builders, who have looked, discussed and decided on what they think is the best solution.
From here the view is not so good, a few pictures may help.
Any of these proposals will work!
I can understand your wish to keep the front uncluttered.
Your concerns regarding the build up of ice in the pipe can be solved by, running a heated ribbon the length of the pipe, this is controlled by a thermostat and will only come on when the air temperature drops to 3C/36F.
In a previous home I had a similar arrangement where the exhaust pipe left the ceiling of the bathroom and crossed the attic venting out of the overhang at the side of the house, it is invisibule. I fitted a one way flap inside the pipe, just inside the roof edge to allow the warm air out pushed by the extractor fan and to keep the cold out. This works perfectly and provides some 40 odd inch icicles every winter.

The logic of soffit vents is somewhat in error.
The idea is that the passing wind will create a low pressure area to the lee of the building, that will suck the warm wet air from the attic/roof space, and replace it with cold drier air. Unfortunately, that air is often freezing and chills your home.

From time to time is does just that, and pulls the heat from your home at the same time....not good.

At other times when it is very cold and there is an area of high pressure, there is no wind.....and it does not happen. At these times that warm wet air in the attic chills and turns to ice, that melts, spoils the insulation. And provides an express route out for your expensive heat, water being a better conductor of heat than air...its 4000 times better at removing your heat than dry air.

It is much better to keep your heat inside your home by using a closed cell insulation, like polystyrene. Polystyrene is water proof wind proof and ice can form on it while it still does its job, insulating your home.

Spray foam is indeed a problem.
If the surface it is sprayed on, is not at the right temperature, if the humidity is wrong, if the mix is wrong......and it can be any of these things.
Spray foam will shrink back, leaving gaps in the insulation, gaps equal heat loss.
All spray foam shrinks by 15% over the first five years.
Most people never notice as they don't study what happens in their roofs walls and floors.

Heat always makes its way to those gaps and cracks in your insulation to escape. If spray foam is not perfect, you waste your money and it is very expensive to provide a four to seven inch thick layer of foam insulation.

As warm wet air always rises, it is quite common for exhausted wet air to be pulled into the roof by the suction of the wind.

So, there you have it, you do not have a problem, that has not been solved previously, elsewhere.

 
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01-28-11, 09:54 AM   #21  
I don't think the exhaust fan is the total issue though but a contributor. The ice dams/icicles go from on end of the house to the other both front and back.

I'll try to better describe my house, it's a ranch going about 55-60' long, the front and back are the same design for the roof. Here is a link to a picture of a house in similar style Raised Ranch Style - House Style Pictures - Raised Ranch House (subtract the roof ridge vent). I have standard fiberglass batts laid on the attic floor probably r-19/20 or so.

I know the exhaust fan needs taken care of and sounds like roof or gable end for exhausting is best but the smaller run you can make the better. But as to the rest so many different ideas to fix it. I have a roofer/insulator coming tomorrow to check things over so hopefully I get a better idea of what can be done.

 
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01-28-11, 11:00 AM   #22  
Ice dams are caused by warm air entering the roof, from the home, heating the roof causing the snow above to melt.

The dam effect is due to the overhang, this is not warmed by the warm air entering the roof.

The overhang remains frozen, stopping the water from escaping downwards.

The warm water gradually climes up the outside roof until it finds an opening, then runs in to the attic.

Most roofs are designed to shed water, they are not built to stop water rising under the tiles/slates/shingles whatever that comprise your roof.

The solution is simple, keep the warm air out of the roof space by filling and blocking all the holes in the walls and ceilings. Then insulate to a level where the warm air does not leak through the insulation. Or build the roof so that it is watertight, and rising water cannot get through.

You can keep a check on the roof temperature by buying a wireless remote sender temperature gauge/humidistat.

I have eight inches of polyurethane insulation in my sun lounge ceiling, the snow does not melt from escaping heat above this part of my home. Where I fitted only five inches of polystyrene in the ceilings of our bedrooms it does melt, albeit very slowly.

Going back to your icicles, you have a badly installed extractor fan in your bathroom, you have a poorly insulated ceilings/attic floors, you have openings where the warm wet air from outside can enter the roof space and condense and freeze.

It gives you something to do over the summer months, all this is DIY territory.

 
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01-29-11, 10:24 AM   #23  
Had the latest roof/insulation guy out. He pretty much came in and said need to blow fiberglass insulation in, bafflies for soffit with more soffit vents, and a roof ridge vent and stop using the attic as a storage space. He didn't say much about sealing up the attic other than maybe covering up light fixtures. I had nothing to disagree with his solution and it probably will solve most of the issues but one thing - We use the Attic for storage of various things and really have no where else to store them in the house. I rather not rent a storage facility for items that are seasonal or needed on various occasions and an outside storage shed in our backyard really isn't what I want on my property especially since those in our area are notorius for bugs/rodents.

Also I felt sealing up any air leaks/heat sources should be done before blowing in any insulation and he seemed more to feel vent/insulation was the answer. I understand most of these pros have a way to do things and they believe in it, but also they push their product to accomplish things regardless how it fits the homeowners needs.

I did notice today the slope of the roof there is not much room near the edges.

I want to keep storage - option 1 Seal up any air leaks best I can, minimize the storage area and put 1-2" foam underneath the flooring to add r6-10 value to that area, add insulation where I can, installl more soffit ventis with baffles to get air flow into the attic.

Option 2- 5 1/2-6" of open cell spray foam on the roof deck underside, and create a conditioned space. Now this is solution would allow me to use the attic as storage easily without a lot of changes. But it seems most people feel this raises concerns with breathing, moisture, and structural support issues. Of course spray foam advocates say these are not issues to worry about. Also spray foam is being used more widely and the technology is evolving so could it be viable?

Am I missing anything, is there someone else I should talk to about making sure I get the best solution for our home and the way we want to use it?

 
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01-29-11, 12:20 PM   #24  
Reading your latest post, you are basically back where

you started.

Perhaps you should look at this a different way?

Why not think about leaving the attic as it is, useful for

storage? And solving the problem another way?

Think instead about the falling price of natural gas and

how this will impact the future, the US has discovered

masses of gas and with it masses of oil.

In many places they have to get the gas out, to get at

the oil, companies will start exporting gas at a loss to

get rid of it, the price of gas is not going up.

Your heating and cooling costs may not come down,

but they are not going up.

Think about comfort, is your home warm enough in

winter cool enough in summer, do you want the

heating and cooling to cost less?

If the answer to these last questions is yes, insulate!

This will save you money and will make your home

more comfortable.

This doesn't mean insulate in the roof space, it means insulate the

upstairs ceilings, to keep your heat in your comfort zone during the

winter and the heat of the sun out during the summer.

Placing a closed cell insulation between the joists and

below the joists, doesn't impinge on the storage

space, the loss of three inches of ceiling height in your

rooms will not be noticed, but the effect on your

heating bill will be, plus you solve the problems of

working in the cramped roof space, icicles and ice dams in one

move.

Inch for inch closed cell insulation provides a much better insulation

than your existing fiberglass, being air tight, waterproof and

windproof. And it is installed from the room below.

 
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01-29-11, 01:06 PM   #25  
To Perry and everyone I want to thank you for your responses since this is one of those things I want to do right the first time.

My major goal is to stop the ice dams and also help control heating/cooling costs which hopefully can be tied into together.

Perry - You're solution of closed cell (spray foam (?) ) in every ceiling and lowering 3" actually might be noticeable I think considering my ceilings in the main living area are only 8' high. Also I have to believe the cost would be a lot higher though if it was the only way cost is not going to stop me.

Now I am wondering what is the difference if I spray foam on the attic floor (open or closed?) and then lay some flooring down over it? Of course this brings up the question how to insulate any intrusions like lights, pipes, wires that I would need to access in the future for any type of changes or repairs.

As for thinking outside the box, I was coming here to post a though I had that may be way off base but figured it was worth asking since it will at least rule it out.
One of the issues I hear about using spray foam on the underside of the roof deck is there should be an inch of space between the shingles and insulation. Just wondering what would happen if those soffit/roof baffles I see recomended to help ventilation were placed underneath the areas being foamed, wouldn't they allow the roof to breath some and still allow the spray foam to do it's job? I guess in my mind the foam would seal off the attic, but having these baffles attached from the soffit area up to the point would allow the roof deck to breathe a bit.

 
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01-30-11, 10:19 AM   #26  
Spray foam is marketed as being being the perfect

insulation. A thin layer will seal all the cracks and at the

same time provide a small amount of insulation.

As most heat is lost or gained through cracks and

gaps in the home, this barrier produces good results,

(for a time) compared with most peoples existing

fiberglass, that rarely fits properly and allows the wind

to suck your heat and water vapor though and round it.

The difference between closed cell and open cell

insulation is as mentioned above a closed cell

insulation is water and wind proof, it can be covered in

ice and still does its job.

Open cell (like fiberglass) lets water vapor and air and

your heat, through, on its way the water can freeze,

when it melts, the product is wet and wet insulation is a

disaster.

The next in line is conduction losses via the frame

work, the wood is connected to the inside comfort

zone and the cold outside and when you add it up the

total amounts to about 1/8th of your walls, ceilings and

floors.

As your home is insulated at the moment the (small)

benefits of the fiberglass are nullified by the losses

through the wooden frame, and I would guess that you

have down lighters or other light fittings that also loose

vast amounts of heat and water vapor into the roof.

What the foam companies don't tell you is that foam

shrinks by 15% over the first five years.

Most people never open their walls or study their roofs

to see what has happened.

A worst problem is that foam can go wrong when it is

sprayed onto a cold surface or the humidity is wrong

or the mix is wrong, it can collapse and separate from

the surface its supposed to insulate.

These gaps cost you good money as the heat goes

through them.

You can fit ceramic or plastic pots over light fittings

and spray over. However, halogen lights do prefer to

run cool, if they run hot, then their life expectancy is

very much less.

That brings us back to the heat loss through the wood.

Wood used to be considered a good insulation, not

any more, with the advent of insulations like

polystyrene that is 98% air or Icynene 99% air, all

products that are serious insulations use tiny balls of

air to insulate

There are two ways to deal with this, take the roof off

and cover the rafters with a SIPS composite. This is a

sandwich of oriented board and five or more inches of

polystyrene. The benefit of this is that when you put

the roof back on, it is entirely separate and insulated

from the wooden frame of your home. There is no

conduction of heat either way. You have a sealed and

comfortable roof space and the benefits are enjoyed

in the home. This is expensive.

The last is to separate the comfort zone from the

wood frame by covering the bottom of the joists in the

ceiling with sheets of polystyrene, tightly butted, they

to a lesser extent do the same job as the SIPS panels.

You can fit more polystyrene between the joists, or

replace the fiberglass, you do not need to loose head

height in the roof.

There is a long term problem with spraying foam on

the underside of the roof. You can ignore the idea of a

gap, to let the air circulate across the roof, that cannot

be done, unless you first create another plywood layer.

The original idea was that air circulates under the roof

and dries out any small leaks, this idea worked well

when homes were heated by open fires, and there

were lots of drafts. (hence the fixated idea of roof

ventilation at the eves and crown)

The problem is that should you develop a leak, the

leak will remain un noticed for years, with the water

being trapped in the fabric of the roof, you will only

discover the problem when a large part of the roof

collapses.

 
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01-30-11, 11:03 AM   #27  
Thanks for responding and the suggestions. I have learned a lot about what used to be a simple process but now with so many products, ideas and differing opinion it's harder to do know what to do.

Spray foam - Would using open cell negate the water/collapsing issue? Also something else came up in my research, I have been reading about people who do a retrofit on an existing home and they seem to have chemical smells afterwards that linger for months to years.

Blown in insulation as an option but from what I have read this doesn't really allow the attic to be used at all for storage and still be effective.

Venting with fiberglass batts. I am leaning this way but now comes the big questions.

1) Baffles on the roof deck to the soffit, I will need to install these but do I also need some kind of air blocker near the edge of the wall and roof instead of just the fiber glass batts? If I do need it, what products/items work well? Also is foam, plastic or cardboard better for the baffles? I would think foam/plastic are better in case of any moisture.

2) Fiberflass unfaced r-30 over the existing fiberglass going the opposite way?
2a) Any particular brands or are they mostly comparable and buy what's best price?

3) Air sealing - what products should I use to cover/seal things like wires, pipes, electrical boxes for lights/fans that are not recessed?
3a) And then are they any products for recessed lights that aren't IC rated? If I can replace with ic rated lights anything other than IC rated I should look for?

 
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