# Insulation Conundrum



## Windows on Wash (Aug 30, 2011)

If you are looking for R-Value, don't be under the misguided impression that the foam backed siding products give you any.

This climate does not require a vapor barrier so the installation of one specifically would be uneccesary and potentially problematic.

If stripping the existing siding, now is your chance to fix a great many issues in the exterior wall insulation.

Pull everything down, air seal the larger gaps and cracks in the interior wall, install proper depth insulation, rigid foam to the exterior (tape and seal all seams) in a sufficient enough depth to prevent dewpoint, new siding.


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## joecaption (Nov 30, 2011)

http://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table


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## Lioncourt (Apr 26, 2012)

Windows on Wash said:


> If you are looking for R-Value, don't be under the misguided impression that the foam backed siding products give you any.
> 
> This climate does not require a vapor barrier so the installation of one specifically would be uneccesary and potentially problematic.
> 
> ...


Stripping the sheathing is probably cost prohibitive and perhaps excessive?


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## Windows on Wash (Aug 30, 2011)

We usually find the fiberboards are trashed on and full of holes. They certainly are not real structural members and are removed pretty simply.

Depending on the structure of the home, you don't need to re-sheet the exterior and can apply the foam directly over the studding.

Dense packing cellulose would be more cost prohibitive than pulling the sheathing and installing traditional batting.

Pulling the board also allows you the ability to foam and seal any penetrations in the interior wall/envelop layer.

I agree with you that it is more expensive, however, I would be willing to bet that if you are doing foam and batting, it would probably be cheaper than foam and dense packing.


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## Lioncourt (Apr 26, 2012)

Interesting, I've never heard of a house without some form of sheathing (not just foam) I know the fiberboard isn't much for rigidity but Shouldn't there be something like an OSB or plywood to reduce stress on the drywall?


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## Windows on Wash (Aug 30, 2011)

Lioncourt said:


> Interesting, I've never heard of a house without some form of sheathing (not just foam) I know the fiberboard isn't much for rigidity but Shouldn't there be something like an OSB or plywood to reduce stress on the drywall?


http://www.buildingscience.com/docu...bracing-requirements-for-insulating-sheathing

You would need to check with your count to see exactly what they require but it can be done with other bracing methods than complete re-sheeting of the walls.

http://www.finehomebuilding.com/des...ns-for-shear-bracing-foam-sheathed-walls.aspx


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## framer52 (Jul 17, 2009)

Correct to the above info. Dense packing Cellulose is much less that fiberglass bats and on top of that it is a better barrier for air infiltration.


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## Windows on Wash (Aug 30, 2011)

framer52 said:


> Correct to the above info. Dense packing Cellulose is much less that fiberglass bats and on top of that it is a better barrier for air infiltration.


Dense packed cellulose is considered and air barrier but the amount of time it will take to do the whole home, and the expense could probably account for the complete stripping of the exterior, sealing, installing batts, and then doing a rigid foam exterior.


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## Lioncourt (Apr 26, 2012)

I believe my house already has diagonal braces so this sounds feasible. Doesn't it make siding more difficult since you have to hit the studs and can't rely on the ply substrate? Wouldn't you use the foam sheets as a vapor barrier and tape all of the seams? any other considerations with this whole method?


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## Windows on Wash (Aug 30, 2011)

Screw the foam board into the studs and use that are your alignment marks for the siding.

You are getting a bit hung up on the vapor barrier aspect. We don't need one in this climate but you do need a proper air barrier.

Tape and stagger the seams. Foam sections that are larger than the tape can cover.


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## Lioncourt (Apr 26, 2012)

Sorry I'm using vapor barrier and air barrier interchangeably


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## Gary in WA (Mar 11, 2009)

1. What type of siding have you decided on?

Check the fasteners on the Celotex fiberboard, many were structural when they first came out. I used it on houses around here in the early '70's, need to use ring-shank nails to get the minimal shear value; http://www.inspectapedia.com/structure/Fiberboard_Sheathing.htm

Check alongside an electrical outlet for fiberglass faced with paper or foil, only R-7-9, worth replacing as WoW said. Leaving it in place will change the exterior sheathing choice....

Gary


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## Lioncourt (Apr 26, 2012)

No fiberglass at all. I need to rip some siding off to take a look at whats under. I'm thinking someones vinyl siding, not sure of brand etc yet.


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## Windows on Wash (Aug 30, 2011)

Lioncourt said:


> No fiberglass at all. I need to rip some siding off to take a look at whats under. I'm thinking someones vinyl siding, not sure of brand etc yet.


Alside Prodigy is my favorite in the foam back family of product.

If you put a rigid foam over the exterior, you can just as easily go with a hollow back.


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## Perry525 (Jan 10, 2010)

The important thing is the water vapor that you and your family create in your home.
Water vapor comes from cooking, washing, breathing, indoor plants, fish tanks, chikdren, animals.
Water vapor always moves from warm to cold.
If the inside of your walls and roof are cold, water vapor will condense on the wood and if it cannot dry, will create mold and in time wood rot.
If you fix polystyrene sheets, or some similar closed cell insulation over the outside, you will keep the frame and everything else inside warm.
Close fitted sheets of polystyrene are both wind proof and water proof.
If you fit water vapor proof plastic sheets between the frame and the polystyrene you will have a cosy dry home.


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## Windows on Wash (Aug 30, 2011)

Perry525 said:


> The important thing is the water vapor that you and your family create in your home.
> Water vapor comes from cooking, washing, breathing, indoor plants, fish tanks, chikdren, animals.
> Water vapor always moves from warm to cold.
> If the inside of your walls and roof are cold, water vapor will condense on the wood and if it cannot dry, will create mold and in time wood rot.
> ...


Perry,

With all due respect, this last statement is completely wrong and terrible advice.

This clients climate zone does not require a Class 1 vapor retarded and putting one to the exterior of the home is both unnecessary and ill advised.

Not only will you be created a double vapor retarder between the foam and the plastic, but you will actually be trapping any accumulated moisture inside the space between the foam and the framing and/or the interstitial wall space and the foam.

Air barrier detailing on the foam should be very careful, redundant, and perhaps duplicative.

If the homeowner removes the fiberboard, they can quite easily air seal the entire interior wall and therefore reduce (probably by about 100X) the amount of moisture coming into the inside space of that wall via bulk air transfer.

Putting a well applied and seal foam to the exterior (provided of sufficient depth and R-Value) will keep moisture from entering from the outside and keep the framing well above dew point and eliminate the potential condensation problem.

Putting plastic between the plastic foam and the home is not recommended.

Everything else that you said was spot on with the exception of that last statement.


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## Lioncourt (Apr 26, 2012)

Well I'm curious to see what the various contractors I have coming to give me quotes have to say. We'll see if they know what they are talking about or just blowing smoke.


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## Gary in WA (Mar 11, 2009)

They may tell you cellulose doesn't need a vapor barrier: http://www.applegateinsulation.com/CEDocuments/Downloads_GetFile.aspx?id=249418&fd=0

http://www.cellulose.org/HomeOwners/AirVaporBarriers.php

Gary


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## Lioncourt (Apr 26, 2012)

So I've got 1 company striping the house to the sheathing and installing the Prodigy insulated siding over Rain Drop house wrap. I've got another that wants to leave the asbestos cement tiles and side over it with brigade board insulation and Mastic XL55 (i think the brigade board replaced the fanfold he suggested when i said i wanted more insulation). Thoughts?


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## AllanJ (Nov 24, 2007)

Lioncourt said:


> Interesting, I've never heard of a house without some form of sheathing (not just foam) I know the fiberboard isn't much for rigidity but Shouldn't there be something like an OSB or plywood to reduce stress on the drywall?


I have  . Example: studs with some diagonal bracing, foam or rigid fiber glass insulation. Vinyl siding on the outside, the usual drywall on the inside.

(Vapor barrier on the inside just behind the drywall if the insulation itself is not impervious.)


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## Windows on Wash (Aug 30, 2011)

We always prefer to strip the exterior walls and get the asbestos off and done.

Insulated siding doesn't add any real appreciable amount of R-Value as compared to what is quoted.


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## Lioncourt (Apr 26, 2012)

Windows on Wash said:


> We always prefer to strip the exterior walls and get the asbestos off and done.
> 
> Insulated siding doesn't add any real appreciable amount of R-Value as compared to what is quoted.


I don't follow your second comment. Each system seems to add about R4 which is better than nothing


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## Windows on Wash (Aug 30, 2011)

Lioncourt said:


> I don't follow your second comment. Each system seems to add about R4 which is better than nothing


Insulation only works when it is in direct contact with the substrate and the contact is 100%. The reality is that your exterior walls are less than plumb, level and true. As a result, most homes with insulated siding will only have what we refer to as intimate contact at about 50% (or less) of the wall surface area. 

This means that you will only have 50% of the intended R-Value realization.

Couple that with the fact that the quoted R-4 is also misleading (they are measuring the R-Value at the thickest section of the foam and the foam is actually tapered so the overall R-Value is closer to about 60-70% of that in most cases) and you are lucky if you are going to get and R-2 average improvement. 

Foam backed siding was invented for rigidity and not for the supposed R-Value improvement. Once the "green" movement took off, the ability to cross promote took off.

If you are really looking to thermally break the exterior wall, the only way to do it is with rigid foam installed and properly fastened to the home.

Sorry if that is a bit of a let down but having seen before and after IR images of homes with insulated siding, the improvements are less than fantastic.


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## Lioncourt (Apr 26, 2012)

Ok so here is what I'm thinking. With the budget I have strip off the siding including the tiles down to the sheathing. cover the foundation/silplate/rim joist/flooring area in ice & water shield to seal up all air infiltration there. Follow with the brigade board and xl55 siding. I know it's not ideal but I'm afraid adding much more in the way of foam would make me build out my window frames a lot. Any thoughts on this whole system? would you replace the brigade board with something different? (I think the alside prodigy is too costly)


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## Perry525 (Jan 10, 2010)

If you stand in front of a mirror in your bathroom and breath slowly onto the mirror you will see condensation, even though the mirror is 22C/70F or more degrees, this is because or breath is saturated with water vapor at body temperature.


From the scale below you will see that condensation forms as the result of both temperature and humidity.......if you take into account your expected indoor average temperature and average humidity this will give you the dew point at which condensation will form.


From this, you can ascertain how much insulation you need on the outside of your frame, to ensure the frame is always above the expected dew point.


Keep in mind that some of us expect to use our heating for at least some of the year, and some of us keep the inside of our homes warmer that the outside, in these circumstances as heat always moves to cold and water vapor always moves from warm to cold or to an area of low pressure , there is no possibility of water vapor moving into a home that is warmer than the outside air.


Down south where it is warmer all year round, or in homes where air conditioning is used to keep the inside air temperature lower than the outside air temperature, then the warmer outside air and higher water vapor will move inwards where there is insufficient insulation. 


If you are fitting a water vapor proof membrane without sufficient backup insulation, this requires extreme care as water vapor molecules are very tiny and they will find there way through the smallest crack or hole.


Drywall is invisible to water vapor, water vapor moves easily through drywall, at a temperature of 30C/86F and 100% humidity indoors and an outdoor temperature below dew point something like a litre of water vapor can move through a 8x4 sheet of drywall in 24 hours.


While timber may be kiln dry when installed with a water content of between 6 and 12% over time it will adjust to its local environment. Getting wet and then drying again does little harm, and with a typical uninsulated home, full of drafts this isn't a problem. Create an almost air tight well insulated home where the timber cannot dry may cause a problem. 


While the water content is below 16% there is no mold, below 19% there is no rot.

Dew Point Calculation Chart (Fahrenheit)
%RH AMBIENT AIR TEMPERATURE IN FAHRENHEIT
20 30 40 50 60(70)80 90100 110 120
90 18 28 37 47 57 67 77 87 97 107 117
85 17 26 36 45 55 65 75 84 95 104 113
80 16 25 34 44 54 63 73 82 93 102 110 
 75 15 24 33 42 52 62 71 80 91 100 108 
 70 13 22 31 40 50 60 68 78 88 96 105
65 12 20 29 38 47(57)66 76 85 93 103
60 11 19 27 36 45 55 64 73 83 92 101
50 9 17 25 34 43 53 61 70 80 89 98
50 6 15 23 31 40 50 59 67 77 86 94 
 45 4 13 2 29 37 47 56 64 73 82 91
40 1 1 18 26 35 43 52 61 69 78 87


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## Lioncourt (Apr 26, 2012)

Lets take this in a new direction. What if I hold off on the siding and start tearing into the inside. If I take my 2 back cold rooms and strip the drywall from the inside I can replace the windows, air seal and insulate(other rooms to follow as money allows). In this scenario would you use un-faced or faced batts? would you install a vapor/air barrier between the insulation and the new drywall? anything to watch out for?


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## Perry525 (Jan 10, 2010)

Keeping in mind that heat always moves outwards towards 
cold.
And that we typically open a window or door to cool down, or 
close the window or door to warm up, it follows that the outside 
is nearly always colder and drier than the inside. In heating 
zones.
When it comes to insulation, the inside of a room, will require 
much less insulation at lower cost, to do a better job, than fitting 
insulation to the outside, with the adjustments to windows and 
doors leading to an odd looking building.
When you add up the amount of timber in the average wall, 
(more than 1/8th is solid timer) and take into consideration , 
that usually the warm inside air is directly in contact with a 
surface that connects directly to the outside cold air, providing 
a solid path for conducted heat, you quickly realize that adding 
a poor quality insulant between the frame, will have a poor 
result.
A better consideration is, drywall, backed by a water vapor 
proof plastic sheet, backed by at least three inches (preferably 
more) of tightly butted polystyrene board, this will provide a 
workable surface, followed by a water vapor proof plastic 
sheet, backed by insulation that will ensure the inside surface 
of the plastic sheet is kept above "dew point" to avoid 
condensation. Should any water vapor find its way through the 
plastic and polystyrene, it will move onwards and outwards.
If you stop and consider that most heat is lost through holes, 
then by conduction through the frame, then think how one might 
create a sealed room, like a plastic airtight/water vapor tight 
box, then add to this three to ten inches of sheet polystyrene 
over the inside and between the sticks, of the outside walls, 
ceiling and floor (a floating insulated floor is very worth while) 
then you can begin to understand how to save money on 
heating and cooling.
Of course you have to consider controlled ventilation, which 
tends to spoil things, or you can open a window and or use a 
dehumidifier to soak up the trapped water vapor.
A well insulated home is something you will enjoy, no only in the 
coldest nights and hottest days, but through out the year - there 
will be many days and nights when you will be comfortable, 
without cost.
And this continues for the life of the building! Dow have been 
selling Blueboard/Styrofoam/polystyrene for 51 years and the 
stuff installed in the early days is still as good a new. I started 
using it to insulate homes 40 odd years ago.
This can be done a bit at a time, starting by finding and filling all 
the holes and cracks, then insulating the ceiling, followed by the 
outside walls and finally the floor.


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## ocfd47543 (Jun 12, 2012)

*foam insulation and hvac*

hello my name is jason, 

i am working closely with a friend(builder) building a 3000 sq ft home. i opted for foam insulation and zero clearance wood burning stove. the idea being to heat most of the house with the stove. the hvac contractor (supposedly knew) i was foam insulating but now says he didnt know. we went with an 80% lennox unit with the thought we didnt need a 90% due to the stove. the insulation guy told me i needed a 90% because of the foam and fresh air issues. i have the feeling my builder and/or the hvac guy wont say they made a mistake. now my builder states i can build plywood boxes over my units and pipe in fresh air for the 80% unit. sounds funny to me.

if anyone knows what i need to do please help?! thank you


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## Perry525 (Jan 10, 2010)

Jason, I've tried heating a home with a wood burner, I've had it red hot to five feet up the chimney, when you could'nt stand within 6 feet, it was so hot -but the heat didn't travel into the other rooms.
The best form of heating is hydronic, water is better at moving heat than dry air. Its 4,000 times better.
A hot water system with base board heating works best, its quick to cool down, when the sun comes out.


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## Lioncourt (Apr 26, 2012)

anyone use a slow rise spray in foam?


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## Windows on Wash (Aug 30, 2011)

You mean drip foam?

i.e. for filling walls and stuff or do you mean low pressure foam?


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## Lioncourt (Apr 26, 2012)

drip. foamit green has a setup


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