Building A Home

[Mass_nerder]

Originally Posted by Shin Pad

You want all insulated walls, ceilings, etc, to be air tight as possible. That means having the vapour re tarder completely sealed (including around openings and penetrations) so that you have no warm moist air from the interior of the house condensing in the insulated space during cold weather. The walls, ceilings etc., should be breathable only from the outside face of the vapour re tarder to the outside (so that any moisture that does get into this space can evaporate to the outside). This will mitigate issues with rotting studs and wood framing, mold, etc., and will make the home much more energy efficient. Bottom line - you want the house to be completely sealed. You can vent the interior through bathroom fans and hood fans when you end up with a lot of moist air inside the house - such as when taking a shower or cooking, You don't want that moist air vented outside through the insulated walls and ceilings.

Not to be pendantic, but the air barrier is what keeps warm moist air from passing through the wall assembly and causing the majority or moisture problems. The vapor ######er just stops vapor diffusion, which is less of a problem (but still important!)
Additionally, the air barrier needs to be on the warm side of the insulation, as the dew point occurs somewhere within the insulation. For most residential construction, this means it needs to be between the gypsum and the insulation (although they really need to start building with the insulation on the exterior of the sheathing like commerical projects).

[RogerWilco]

Originally Posted by Mass_nerder

Not to be pendantic, but the air barrier is what keeps warm moist air from passing through the wall assembly and causing the majority or moisture problems. The vapor ######er just stops vapor diffusion, which is less of a problem (but still important!)
Additionally, the air barrier needs to be on the warm side of the insulation, as the dew point occurs somewhere within the insulation. For most residential construction, this means it needs to be between the gypsum and the insulation (although they really need to start building with the insulation on the exterior of the sheathing like commerical projects).

I don't want to get into a long discussion about this but after reading your comment I feel the need to respond. You have it backwards. The Vapour Barrier need to be on the warm side of the insulation (cold climate dependant) and the air barrier can be pretty mush anywhere in the assembly. For low rise construction 6mil ploy usually acts as both, but once you exceed 4 storeys 6 mil poly cant handle the air pressure and other forms of air barrier must be used. Below is a short article that explains it somewhat.

https://www.ecohome.net/guides/2316/...apor-barriers/

[RogerWilco]

The best suggestion I could make is that no matter who you choose to build your home, even though it will be a few thousand dollars extra, it is a good idea to hire a third party envelope consultant. The third party consultant could be hired to review the construction drawings of the builder and more importantly do field reviews of the installation of the vapour, moisture, and air barriers. They generally care E&O insurance and will provide field reports to keep the builder accountable an add an extra level of liability insurance coverage to your most likely life changing investment.

[CroFlames]

Originally Posted by RogerWilco

The best suggestion I could make is that no matter who you choose to build your home, even though it will be a few thousand dollars extra, it is a good idea to hire a third party envelope consultant. The third party consultant could be hired to review the construction drawings of the builder and more importantly do field reviews of the installation of the vapour, moisture, and air barriers. They generally care E&O insurance and will provide field reports to keep the builder accountable an add an extra level of liability insurance coverage to your most likely life changing investment.

Even for new homes that aren't custom i.e.: estate homes a builder has built 100 times in the same area?

[Mass_nerder]

Originally Posted by RogerWilco

I don't want to get into a long discussion about this but after reading your comment I feel the need to respond. You have it backwards. The Vapour Barrier need to be on the warm side of the insulation (cold climate dependant) and the air barrier can be pretty mush anywhere in the assembly. For low rise construction 6mil ploy usually acts as both, but once you exceed 4 storeys 6 mil poly cant handle the air pressure and other forms of air barrier must be used. Below is a short article that explains it somewhat.

https://www.ecohome.net/guides/2316/...apor-barriers/

Edit*
Not trying to argue, but see article for what I was talking about.
https://www.buildingscience.com/docu...l-in-buildings

[jwslam]

Originally Posted by Shin Pad

Bottom line - you want the house to be completely sealed. You can vent the interior through bathroom fans and hood fans when you end up with a lot of moist air inside the house - such as when taking a shower or cooking, You don't want that moist air vented outside through the insulated walls and ceilings.

So I have my house completely sealed, and I turn on the hood fan / bathroom fans. Where does make-up air come from? I draw a vacuum inside my house and my fireplace flames go to fuuuuu

Source: personal experience in 2017 built house

[RogerWilco]

Originally Posted by Mass_nerder

Edit*
Not trying to argue, but see article for what I was talking about.
https://www.buildingscience.com/docu...l-in-buildings

I definitely agree with this part of your post:

"although they really need to start building with the insulation on the exterior of the sheathing like commerical projects"

Uninsulated wood studs for plumbing and electrical with all of the insulation on the outside and a dual vapour/air barrier between the insulation and sheathing is pretty much the perfect wall.

But regardless, your vapour barrier in cold climate needs to be on the warm side of the insulation. Your air barrier is best on the warm side of the insulation but can be on the outside. If the air barrier is on the outside it must be vapour permeable. But as stated above, it wood be best to stick it all on the outside and not insulate the studs at all.

[Mass_nerder]

Originally Posted by RogerWilco

I definitely agree with this part of your post:

"although they really need to start building with the insulation on the exterior of the sheathing like commerical projects"

Uninsulated wood studs for plumbing and electrical with all of the insulation on the outside and a dual vapour/air barrier between the insulation and sheathing is pretty much the perfect wall.

But regardless, your vapour barrier in cold climate needs to be on the warm side of the insulation. Your air barrier is best on the warm side of the insulation but can be on the outside. If the air barrier is on the outside it must be vapour permeable. But as stated above, it wood be best to stick it all on the outside and not insulate the studs at all.

Yep, vapor barrier definitely also on the warm side.
I think my point was just that air exfiltration is the real concern in cases of moisture damage in the wall assembly. Vapor diffusion is less of a concern, but certainly still important.

[Barnes]

Originally Posted by jwslam

So I have my house completely sealed, and I turn on the hood fan / bathroom fans. Where does make-up air come from? I draw a vacuum inside my house and my fireplace flames go to fuuuuu

Source: personal experience in 2017 built house

Even our previous house built in 2007 at least turned on the furnace fan to pull fresh air to balance out the hood / exhaust fans.

If your house was built in 2017, you should have an HRV or ERV to balance air movement. It's required to provide the required fresh air and maintain indoor air quality.

[jwslam]

Originally Posted by Barnes

Even our previous house built in 2007 at least turned on the furnace fan to pull fresh air to balance out the hood / exhaust fans.

If your house was built in 2017, you should have an HRV or ERV to balance air movement. It's required to provide the required fresh air and maintain indoor air quality.

Yes there is an HRV but that does nothing for air recovery when the hood fan is drawing a couple hundred CFM out; especially when there is nothing to tell the heating system this is occurring.

[Shin Pad]

Originally Posted by jwslam

So I have my house completely sealed, and I turn on the hood fan / bathroom fans. Where does make-up air come from? I draw a vacuum inside my house and my fireplace flames go to fuuuuu

Source: personal experience in 2017 built house

Well for sure you don't want it coming through the walls, ceilings, etc. You have make up air coming into your furnace, which should compensate for any exhaust from hood fans/bathroom fans. If you have a vacuum inside your house which affects the fireplace flame, then your mechanical system isn't balanced properly. Also, you have fresh air intake to your fireplace, which may be the problem - ie - not enough fresh air coming in.

[Barnes]

Originally Posted by jwslam

Yes there is an HRV but that does nothing for air recovery when the hood fan is drawing a couple hundred CFM out; especially when there is nothing to tell the heating system this is occurring.

It should be interlocked to the furnace fan at least. My bathroom fans are all run through the HRV, do yours exhaust directly outside?

[Shin Pad]

One other thing - polyethylene is neither an air barrier nor a vapour barrier, it is a vapour re-trader.
https://www.finehomebuilding.com/200...apor-######ers


Anyway, bottom line, in residential construction, it serves as a vapour re-tarder which has a perm rating that is good enough for house construction. Most new houses are built with some sort of wrap on the outside of the sheathing, such as Tyvek or similar product. These act as the air barrier.


In commercial construction, usually the air/vapour barrier is something like a self adhered membrane like blue skin, which has a perm rating low enough to be considered a vapour barrier as opposed to a vapour re-tarder and also acts as the air barrier.

[opendoor]

Originally Posted by Shin Pad

One other thing - polyethylene is neither an air barrier nor a vapour barrier, it is a vapour re-trader.
https://www.finehomebuilding.com/200...apor-######ers

Sure it's a vapor barrier. Anything under 0.1 perms (6 mil poly is 0.06 perms) is Class I which is considered an impermeable vapor barrier.

[Shin Pad]

Originally Posted by opendoor

Sure it's a vapor barrier. Anything under 0.1 perms (6 mil poly is 0.06 perms) is Class I which is considered an impermeable vapor barrier.

Throughout the building community, the term vapor ######er is often used interchangeably with the term “vapor barrier,” which refers to any material that bars the transmission of water vapor through walls, ceilings and floors. Most of the materials referred to as vapor barriers, however, will permit some vapor transmission, making the label inaccurate. Even 6-mil polyethylene, one of the most common vapor barrier materials, has a 0.06 perm rating and can therefore be considered a vapor ######er in spite of its extremely low permeance.



https://www.certainteed.com/insulati...re-management/



Calpuck won't allow the use of the word re-tarder, so in the above link you have to insert it - Anyway, the above paragraph sums it up. No one in the building design community would consider polyethylene to be a vapour barrier.

[opendoor]

Originally Posted by Shin Pad

I disagree. Layfield plastics which is a major manufacturer of 6 mil poly, lists the perm rating at 0.16 which above 0.1, therefore it is a vapour re-tarder.

You might be mixing up metric and US perms (Class ratings are based on the latter). Or you might be looking at the thickness in metric (6 mils is pretty close to 0.16 mm).



Regardless, here are test results for Layfield 6 mil poly showing a US perm rating of 0.044 perms:



https://www.layfieldgroup.com/Conten...t_Results1.pdf

[opendoor]

Originally Posted by Shin Pad

Throughout the building community, the term vapor ######er is often used interchangeably with the term “vapor barrier,” which refers to any material that bars the transmission of water vapor through walls, ceilings and floors. Most of the materials referred to as vapor barriers, however, will permit some vapor transmission, making the label inaccurate. Even 6-mil polyethylene, one of the most common vapor barrier materials, has a 0.06 perm rating and can therefore be considered a vapor ######er in spite of its extremely low permeance.



https://www.certainteed.com/insulati...re-management/



Calpuck won't allow the use of the word re-tarder, so in the above link you have to insert it - Anyway, the above paragraph sums it up. No one in the building design community would consider polyethylene to be a vapour barrier.

By that logic, vapor barriers essentially don't in building, unless you have a perfectly sealed glass box.


More commonly, the term is used for materials that are below 0.1 perms and are considered vapor impermeable for all intents and purposes. Poly sheeting fits that bill.

[Shin Pad]

Originally Posted by opendoor

By that logic, vapor barriers essentially don't in building, unless you have a perfectly sealed glass box.


More commonly, the term is used for materials that are below 0.1 perms and are considered vapor impermeable for all intents and purposes. Poly sheeting fits that bill.

Exactly - you never get a completely sealed building - ever. Even in high end construction, such as high rises, etc., you never get a perfect seal. The idea is to get it sealed as well as possible. Polyethylene may be ok in a house, or even some smaller wood framed commercial buildings or wood framed condos, but it isn't good enough for most other types of buildings. Even if the perm rating is low enough to be under 0.1 perms, would you use a polyethylene vapour ######er in a high humidity, high performance project like a hospital? Not a chance. As per my link in a previous post, polyethylene is still considered a vapour ######er even if it is below 0.1 perms. It just isn't robust enough to be considered a vapour barrier.


In my specifications, I make sure I distinguish how I call up the materials, whether they are vapour ######ers, air barriers, air/vapour barrier. Neither I nor any of my Architect clients would ever call polyethylene a vapour barrier.

[topfiverecords]

Specifications and architectural details aren’t really relevant for a suburban home builder. For the last hundred thousand homes there has been zero thought beyond:

- Paint
- Primer
- Mud/Tape
- 1/2” Gypsum
- 6mil Poly
- Various R-Value Batt insulation
- 2x6 Studs (2x4 long ago)
- Sheathing
- Tyvek or equiv. (Tar paper long ago)
- Rainscreen in very exclusive situations
- Exterior finish

Repeat, repeat, repeat, repeat, repeat for the next hundred thousand homes.

In Calgary, stucco without a rainscreen, poorly thought out architectural details, and lack of proper window installation techniques are the real problem not air barriers or vapour re-tarders.

[RogerWilco]

Originally Posted by CroFlames

Even for new homes that aren't custom i.e.: estate homes a builder has built 100 times in the same area?

It is worth protecting the largest investment of your life. Many of these tract homes/condos are the worst culprits.