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Building Science- Perfect Wall Questions

 
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Old 03-03-2013, 11:00 PM   #41
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Re: Building Science- Perfect Wall Questions


yea home slicker/cedar breather,this product was created because builders were not using as much of those product as the company wanted

it's more reasonably priced and the low profile 1mm spacers are practically unnoticeable when installing over it
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Old 03-04-2013, 06:01 AM   #42
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Re: Building Science- Perfect Wall Questions


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yea home slicker/cedar breather,this product was created because builders were not using as much of those product as the company wanted

it's more reasonably priced and the low profile 1mm spacers are practically unnoticeable when installing over it
Home Slicker/ cedar breather is made with Typar, correct? If it is I looked into using the product.

I found it interesting that when I talked to a representative for Obdyke he said it could be applied with staples. When you install regular Typar, Typars specs call for cap nails.
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Old 03-09-2013, 01:46 AM   #43
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Re: Building Science- Perfect Wall Questions


FJN - I think you nailed it about the older homes...we are heading that way in a roundabout way by rainscreening. Older homes were sieves, and consequently, they could dry out inside the wall assembly with balloon framing. Now, we push out the wall, the siding now takes the punishment, gets wet, but now it can dry out, because there is an air gap on the backside. So, we have taken care of water egress. Now, we have to worry about vapor.

Now Typar indicates their housewrap has the 'ideal' perm rating to allow vapour the house creates to escape, but it blocks vapor from coming in. This sounds good, but I think in a climatic zone such as ours, we have distinct summer and winter climes, and varying vapour loads. I suspect we have vapour trying to escape in summer and vapour trying to enter in winter. Then you have our air tight houses. An air tight house creates pressure differences (drives vapour) at different times of year. Not sure a house wrap can cover all the bases.

I bet we get to the point where we have a rainscreen layer, as we do now, and we will have a vapourscreen layer (much like rainscreen, but will be a controlled system). That vapourscreen layer will be controlled by an HVAC system which will monitor humidity. So, in a nutshell, we will have a leaky house, but the leak will be controlled...

Just off the top of my head, my perfect house, would have (exterior to interior) Hardi, 1/2" PT furring strips with insect guards (rainscreen), XPS (4" - taped, caulked), 1/2" ply painted with a low perm barrier, 2x6 studs filled with Roxul (minus 1/2"), 1/2" cavity (have to figure out to maintain the cavity), 6mil vapour barrier (min perms), backer board/gyproc...that cavity would extend from basement to ridge beam (drill holes in plates to maintain flow). That space would be hooked up to a HVAC system so humidity levels be kept at a min either by dehumidifying and/or driving dry air through the walls. Any hot air (like mine) would be recycled via heat exchanger. This way, the wall assembly can stay dry from the inside, and any vapour leaks from outside or inside can be handled.
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Old 03-09-2013, 02:27 AM   #44
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Re: Building Science- Perfect Wall Questions


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Originally Posted by Mellissam View Post
FJN - Older homes were sieves, and consequently, they could dry out inside the wall assembly with balloon framing. Now, we push out the wall, the siding now takes the punishment, gets wet, but now it can dry out, because there is an air gap on the backside. So, we have taken care of water egress. Now, we have to worry about vapor.

Now Typar indicates their housewrap has the 'ideal' perm rating to allow vapour the house creates to escape, but it blocks vapor from coming in. This sounds good, but I think in a climatic zone such as ours, we have distinct summer and winter climes, and varying vapour loads. I suspect we have vapour trying to escape in summer and vapour trying to enter in winter. Then you have our air tight houses. An air tight house creates pressure differences (drives vapour) at different times of year. Not sure a house wrap can cover all the bases.

I bet we get to the point where we have a rainscreen layer, as we do now, and we will have a vapourscreen layer (much like rainscreen, but will be a controlled system). That vapourscreen layer will be controlled by an HVAC system which will monitor humidity. So, in a nutshell, we will have a leaky house, but the leak will be controlled...

Just off the top of my head, my perfect house, would have (exterior to interior) Hardi, 1/2" PT furring strips with insect guards (rainscreen), XPS (4" - taped, caulked), 1/2" ply painted with a low perm barrier, 2x6 studs filled with Roxul (minus 1/2"), 1/2" cavity (have to figure out to maintain the cavity), 6mil vapour barrier (min perms), backer board/gyproc...that cavity would extend from basement to ridge beam (drill holes in plates to maintain flow). That space would be hooked up to a HVAC system so humidity levels be kept at a min either by dehumidifying and/or driving dry air through the walls. Any hot air (like mine) would be recycled via heat exchanger. This way, the wall assembly can stay dry from the inside, and any vapour leaks from outside or inside can be handled.



This is what I'm talking about.

Well written!

I have a couple ideas about this:

"1/2" cavity (have to figure out to maintain the cavity)"



This would have to be engineered, IMHO.

"That space would be hooked up to a HVAC system so humidity levels be kept at a min either by dehumidifying and/or driving dry air through the walls."

I, to this day, have not seen a model like this yet. I like where you're heading.

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Old 03-09-2013, 09:42 AM   #45
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Re: Building Science- Perfect Wall Questions


There is this thing called fire blocking & required for a reason

The pressures are not the issue, nor is diffusion, it is the air leakage that allows the moisture to travel into the cavities

The reason the rain screen space is nice is it allows the water to drain out quickly removing the issues with solar drive, capillary action, etc... That is not an issue inside the house
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Old 03-09-2013, 11:09 AM   #46
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Re: Building Science- Perfect Wall Questions


If it were simple, there wouldn't be any problems. Even something as basic as whether it's baseboard hot water of forced air makes a big difference.
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Old 03-09-2013, 11:55 AM   #47
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Re: Building Science- Perfect Wall Questions


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There is this thing called fire blocking & required for a reason

The pressures are not the issue, nor is diffusion, it is the air leakage that allows the moisture to travel into the cavities

The reason the rain screen space is nice is it allows the water to drain out quickly removing the issues with solar drive, capillary action, etc... That is not an issue inside the house
Yeah, the fire break issue will have to be addressed. However, BI's are concerned with fire not reaching wall cavities (hence drywall being rated), not so much once the fire gets there...could always get complicated and put fire rated mechanical pressure valves in at floor plates. I gave it some thought last night and I was thinking of a piping system, like drain tiles, but much smaller (really small - so fire cannot spread easily)...maybe I am going overboard here, but if one gets the vapour out of the walls, even miniscule amounts, then your heating load goes down...takes more energy to heat moisture laden air than dry air. Heck, what about using those same pipes to heat the home...a whole house heating system....hmmm. Can make the system passive, using thermodynamics of air to help circulate (not only by heating, but pipe size etc.).

Totally agree with your last paragraph, except no house is perfect...at least I haven't seen one. If you forget to turn on the bathroom fan after a steamy shower or like me, boil water sending a cup or two of vapour into the house or use a humidifier, then you'll eventually have an issue. As we quest to get houses more airtight, minor amounts of vapour become an issue. We used to get away with it because houses were sieves, but I cannot tell you how many newish homes I've been into with vapour/water damage.

Having a cavity system will allow one to 'grow' with the house, as aged caulking, shifting etc., will introduce leaks, but the HVAC system can adjust to handle it.

Ok, maybe I am going overboard somewhat, but I like the idea of the wall assembly being isolated from exterior and interior.
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Old 03-09-2013, 01:05 PM   #48
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Re: Building Science- Perfect Wall Questions


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Typar indicates their housewrap has the 'ideal' perm rating to allow vapour the house creates to escape, but it blocks vapor from coming in. This sounds good, but I think in a climatic zone such as ours, we have distinct summer and winter climes, and varying vapour loads. I suspect we have vapour trying to escape in summer and vapour trying to enter in winter. Then you have our air tight houses. An air tight house creates pressure differences (drives vapour) at different times of year. Not sure a house wrap can cover all the bases
an Air barriers stop vapor transmission by an order of magnitude more than so called vapor barrier installations that don't take air sealing into account.
Quote:
it takes more energy to heat moisture laden air than dry air
.
Humid air is more comfortable at lower temperatures than dryer air so you don't have to heat it to the same levels.
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Old 03-09-2013, 10:40 PM   #49
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Re: Building Science- Perfect Wall Questions


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Ok, maybe I am going overboard somewhat, but I like the idea of the wall assembly being isolated from exterior and interior.
Well then, eliminate all the insulation in the wall cavity, put more outside the sheathing as required & you are done... No need for specialty pipes or fittings or anything else. If Joe L's perfect assembly doesn't sell you, check out BensonWood that has been marketing panels like this, etc...

As for the prior item on water vapor from boiling water & showers - yes that can be an issue. I would dare say it is even more of an issue in a house that is leaky as you just don't see it until you rip open the walls. In a tight house where it is raining inside... well if that doesn't give the HO a clue, nothing will
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Old 03-09-2013, 11:06 PM   #50
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Re: Building Science- Perfect Wall Questions


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As for the prior item on water vapor from boiling water & showers - yes that can be an issue. I would dare say it is even more of an issue in a house that is leaky as you just don't see it until you rip open the walls. In a tight house where it is raining inside... well if that doesn't give the HO a clue, nothing will
People do stupid things, and it's almost impossible short of temp and humidity control with good airflow to make anything idiot proof. Like the person who set up half a dozen clothes drying racks in her living room because her dryer stopped working....
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Old 03-10-2013, 12:24 AM   #51
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Re: Building Science- Perfect Wall Questions


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...
.
Humid air is more comfortable at lower temperatures than dryer air so you don't have to heat it to the same levels.
I thought it was the other way around...what do they call it, specific heat capacity of moisture laden air is more than dry air at same temp.
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Old 03-10-2013, 12:37 AM   #52
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Well then, eliminate all the insulation in the wall cavity, put more outside the sheathing as required & you are done...
Haha, I agree to a point, but I just figured the wall cavities should be put to use...have a lot of pocket bookcases?

I also figured that 4" of exterior XPS is enough for me...don't want Hardi hanging off the ends of 10" GRK's (2" in stud).

Reminds me that all those GRK screws are a potential point of entry...I made about 90% into rafters when I did a little roof with 8" GRKs...which means I made a dozen holes through XPS into sheathing...backed out and tried again. Normally, I'd have said fine, but the guy wanted no visible screws for the exposed rafters...
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Old 03-10-2013, 12:21 PM   #53
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Re: Building Science- Perfect Wall Questions


Atricle....The Trouble With Building Science.






http://www.finehomebuilding.com/desi...g-science.aspx
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Old 03-10-2013, 02:30 PM   #54
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Re: Building Science- Perfect Wall Questions


I think the crucial factor in wall construction is ventilation, without it problems will occur. In a perfect scenario the vapor barrier would eliminate the migration from the living space and a rain screen would eliminate water from the outside, but in reality neither of these layers can be 100% perfect. The wall must be constructed with the notion that there will be water intrusion and a system must in place that will deal with it.

I have always thought it odd that we have a different construction method for a roof with insulation against it, where you need to have an air space between the outside sheathing and the insulation, usually accomplished with the spacers stapled to the outside sheathing between the rafters. Isn't the roof in this situation just a wall that is not vertical. If the same thing was done on vertical walls I think it would eliminate water retention.

Air circulation is the key, leave room for the air to travel and vent and the wall will be fine.
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Old 03-10-2013, 11:17 PM   #55
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Re: Building Science- Perfect Wall Questions


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Atricle....The Trouble With Building Science.






http://www.finehomebuilding.com/desi...g-science.aspx
Long story short, it's complicated and not well understood by many.
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Old 03-24-2013, 05:55 PM   #56
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Re: Building Science- Perfect Wall Questions


been thinking of doing walls batt then cc foam.
i have used cc batt on most of my builds over the last ten years.
have opened a few walls of stuff that i built and have not found no bad stuff yet time will tell.
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Old 03-25-2013, 08:01 PM   #57
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been thinking of doing walls batt then cc foam.
i have used cc batt on most of my builds over the last ten years.
have opened a few walls of stuff that i built and have not found no bad stuff yet time will tell.
Which side will the CC foam go on?
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Old 03-25-2013, 08:27 PM   #58
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Which side will the CC foam go on?
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