The problem I am most interested in discussing is on which side you are putting your vapour barrier on.
You need the vapour barrier on the warm side of the exterior walls. But in the winter this is on the inside side of the wall, and in the summer with airconditioning this becomes the outside side of the wall. This is responsible for a lot of mold, rot and related problems developing in Canada and northern US States as airconditioning for summer and heating for winter is more normal.
How are you adapting designs to solve this design dilema for buildings that are heated in winter and cooled in summer?
mag....you have an option as I see it... In the summer, don't turn on the Air Conditioner in the summer and the vapor barrier will work on the exterior in a Cold Winter Climate during the summer, cause it is always hotter on the inside during the summer. That is if you keep all your windows closed, cut down all the trees surrounding the structure to assure maximum solar gain. This is because you can maintain the hottest fricking temperature on the inside year round. On days when it looks like it might be cool on the outside and your concerned about the temperature drop on the interior exceeding the drop of temperature on the outside, just crank up the heat...and you can solve that problem.
kwarch, I worked on a big university project that used poly-spray foam insulation in efforts towards making a "tight" building. I agree, perfectly detailed it appears to solve all the moisture/mold issues of any climate.
Unfortunately, I don't have any faith that it can ever be perfectly detailed. Maybe a very small project where the contractor totally bought in to the theory. The gymnastics we were asking the contrators to go through via our details were ridiculous. I left the office before the project started construction, and never found out how well it worked out.
In Canada we have the traditional wood frame construction. The exterior walls are 2 x 4 wood studs with fibreglass batts insulation between the studs. The Poli vapour barrier goes on the inside side of the wood studs followed by drywall on the interior side.
The batts is in contact with the Poli Vapour barrier and works fine durring the winter season when the warm humid air is inside the building.
However in the summer month if the building is airconditioned, the outside humid air condenses on the poly vapour barrier and is absorrbed by the fibreblass batts which becomes soaked with water and starts to grow mold and rotting the wood studs. The only thing that stops it is the change in weather.
Because the exterior side of the wall is designed with a circulated air space between the brick and the studs the air movement acts to dry out the trapped humidity which limits the amount of rot and mold growth to a few months of the year. The cicle of deterioration works at a pace of about 20 to 30 years before there are noticiable problems.
This old system (in place since before aircondictioning) is now starting to cause many problems with mold and rot caused by use of airconditioning. It was not a problem 20 years ago because fewer buildings has airconditioning and the amount of deterioration has not yet received much attention.
As the homes build 20 years ago with central air but with buildign codes that did not account for the change in tempurature and humidity conditions we are starting to hear of mold and rot a lot more now.
the typical spray-foam insulation we specify has very low vapor transmission / perm rating - therefore it provides vapor barrrier in both directions - we are no longer concerned about which side of the wall the vapor barrier is on - we are more concerned about having a continuous air barrier.
if you are thinking about traditional fiberglass insulation & polyethylene vapor barrier construction, then yes.... you do have a problem. this system does not work very well and is extremely difficult to construct correctly.
I don't know about how much things improve with spray foam. Even if its a perfect seal (which is difficult to obtain and maintain in wood frame assemblies), the due point becomes the surface of the foam on the inside in heating season and on the outside in cooling season.
p.s. recently completed a 95,000 s.f college science building utilizing spray-foam insulation & proper air-barrier detailing - quite successfully.
The Owner now requires this system for all new campus construction.
How about a combination... spray foam with a layer of board material on each side that absorbs and holds the moisture when it condenses and dries out when the system reverses with the swings in the temperatures without sufferng the ill effects of deterioraation, rot, mold, etc?
a detail i can recommend, when dealing with wood-frame construction, is to run horizontal 2x's directly on the outside of your vertical 2x wall framing, prior to sheathing - then spray-foam can be continuous & minimize heat-loss thru the studs - it also makes connection to foundation insulation better.
dew point may not be where you think it is
traditional fiberglass & poly just plain doesn't work
again - www.buildingscience.com - are the gurus on air, vapor, insulation, mold, etc, etc - in all climates
there are many vapor issues with SIPs as well. the details given by the manufacturer require a 4mil vapor barrier on the warm side of the wall. the panels also don't allow enough airflow through the walls - i am assuming you get a similar condition with spray foam - and you get sick building syndrome. you have to detail a HVAC system that circulates the air properly. this becomes a problem when you have a radiant floor heat system.
vapor barriers are so cheap $.01/sf.
why not have one on each side of the wall??? then there can be no seasonal issues.
If the wall studs were properly dried and not soaked on the construction site before installation, then the moisture trapped in the wall will be minimal - 20% or less and then no mold!
For tight buildings (ie most high perfomance structures) the key is designed ventilation to keep the IAQ healthy. It's much better to have air flowing through ducts/intakes then infiltrating through sloppy construction.
typical northern climate residences in my region, not requiring air-conditioning, generally utilize hot-water baseboard or radiant heating systems rather than air systems.
spray-foam & SIPs wall insulation systems create much tighter envelopes than traditional construction. thus - heat recovery ventilators are highly recommended - for controlled ventilation
The warm side of the wall changes with the seasons. Hence the main problem with vapour barriers. You need two. One for cooling and one for heating seasons for the climates where you need both heating and cooling.
treekiller - one of the fiberglass insulation manufacturers actually has a product where the fiberglass is entirely encapsulated within a poly (vapor barrier) bag - a better solution than traditional, but not entirely without glitches
in so cal, they house wrap with plastic (tyvek) and use plastic face fiberglass insulation inside. not that we have extreme in/out temperature shifts. i've never house wrapped to this date.
a lot of it is a big hype coming from lawyers, plastic manufacturers and mid age mothers/fathers of infants.
i mean. i've seen a lot of bldgs with no vpr bar. that have no problem btwn walls and on surface.
but i am talking about so cal. i am aware the temp dif. is much more greater in some other parts. where vpr barriering is a science to be wreckoned.
However in the summer month if the building is airconditioned, the outside humid air condenses on the poly vapour barrier and is absorrbed by the fibreblass batts which becomes soaked with water and starts to grow mold and rotting the wood studs. The only thing that stops it is the change in weather.
Because the exterior side of the wall is designed with a circulated air space between the brick and the studs the air movement acts to dry out the trapped humidity which limits the amount of rot and mold growth to a few months of the year. The cicle of deterioration works at a pace of about 20 to 30 years before there are noticiable problems.
This kind of explains who it generally works today.
m-c
so have you considered increasing your air space (between brick and sheathing) to 4 or 5 inches, and spray-foaming the outside face of the sheathing (before brick goes up) leaving 1.5 to 2 inch air space
the foam insulates, creates drainage plain, air barrier & vapor barrier all-in-one, leaving stud space clear for MEP services
this is a standard system we've used for many years
rigid insulation & tape is an alternative to spray-foam
The idea of having moisure condense on a V.B. and then drying it out with a vent space seems to work. So why not adapt a material that absorbes moisture and then dries out with ventilation without ill effects?
Vapour Barriers and how to deal with them properly
Vapour Barriers and how to deal with them
Architects have considerable difficulties managing the design of vapour barriers into construction assemblies.
Few get it right in every situation.
What are some of the problems and solutions from people on this forum in different parts of the world and climates?
from northeast u.s......cold climate
vapor is just one part of the problem
polyurethane spray-foam insulation solves vapor, moisture, insulation and air barrier all in one.
properly detailed, i think it comes closest to solving most envelope situations
some excellent resources:
www.buildingscience.com
www.eeba.org
www.airbarrier.org
The problem I am most interested in discussing is on which side you are putting your vapour barrier on.
You need the vapour barrier on the warm side of the exterior walls. But in the winter this is on the inside side of the wall, and in the summer with airconditioning this becomes the outside side of the wall. This is responsible for a lot of mold, rot and related problems developing in Canada and northern US States as airconditioning for summer and heating for winter is more normal.
How are you adapting designs to solve this design dilema for buildings that are heated in winter and cooled in summer?
here in the middle we go by the rules of the south: behind the siding/roofing but outside the insulation of exterior walls and roof.
winter doesn't seem to have as many mold issues as summer.
mag....you have an option as I see it... In the summer, don't turn on the Air Conditioner in the summer and the vapor barrier will work on the exterior in a Cold Winter Climate during the summer, cause it is always hotter on the inside during the summer. That is if you keep all your windows closed, cut down all the trees surrounding the structure to assure maximum solar gain. This is because you can maintain the hottest fricking temperature on the inside year round. On days when it looks like it might be cool on the outside and your concerned about the temperature drop on the interior exceeding the drop of temperature on the outside, just crank up the heat...and you can solve that problem.
kwarch: spray-foam insulation is a Problem in NEW ENGLAND:
It causes the paint to peel on exterior Clap-board siding.
It is a Bitch in renovation projects when one is snaking electrical wires in a wall filled with spray-foam insulation.
kwarch, I worked on a big university project that used poly-spray foam insulation in efforts towards making a "tight" building. I agree, perfectly detailed it appears to solve all the moisture/mold issues of any climate.
Unfortunately, I don't have any faith that it can ever be perfectly detailed. Maybe a very small project where the contractor totally bought in to the theory. The gymnastics we were asking the contrators to go through via our details were ridiculous. I left the office before the project started construction, and never found out how well it worked out.
In Canada we have the traditional wood frame construction. The exterior walls are 2 x 4 wood studs with fibreglass batts insulation between the studs. The Poli vapour barrier goes on the inside side of the wood studs followed by drywall on the interior side.
The batts is in contact with the Poli Vapour barrier and works fine durring the winter season when the warm humid air is inside the building.
However in the summer month if the building is airconditioned, the outside humid air condenses on the poly vapour barrier and is absorrbed by the fibreblass batts which becomes soaked with water and starts to grow mold and rotting the wood studs. The only thing that stops it is the change in weather.
Because the exterior side of the wall is designed with a circulated air space between the brick and the studs the air movement acts to dry out the trapped humidity which limits the amount of rot and mold growth to a few months of the year. The cicle of deterioration works at a pace of about 20 to 30 years before there are noticiable problems.
This old system (in place since before aircondictioning) is now starting to cause many problems with mold and rot caused by use of airconditioning. It was not a problem 20 years ago because fewer buildings has airconditioning and the amount of deterioration has not yet received much attention.
As the homes build 20 years ago with central air but with buildign codes that did not account for the change in tempurature and humidity conditions we are starting to hear of mold and rot a lot more now.
the typical spray-foam insulation we specify has very low vapor transmission / perm rating - therefore it provides vapor barrrier in both directions - we are no longer concerned about which side of the wall the vapor barrier is on - we are more concerned about having a continuous air barrier.
if you are thinking about traditional fiberglass insulation & polyethylene vapor barrier construction, then yes.... you do have a problem. this system does not work very well and is extremely difficult to construct correctly.
I don't know about how much things improve with spray foam. Even if its a perfect seal (which is difficult to obtain and maintain in wood frame assemblies), the due point becomes the surface of the foam on the inside in heating season and on the outside in cooling season.
p.s. recently completed a 95,000 s.f college science building utilizing spray-foam insulation & proper air-barrier detailing - quite successfully.
The Owner now requires this system for all new campus construction.
How about a combination... spray foam with a layer of board material on each side that absorbs and holds the moisture when it condenses and dries out when the system reverses with the swings in the temperatures without sufferng the ill effects of deterioraation, rot, mold, etc?
a detail i can recommend, when dealing with wood-frame construction, is to run horizontal 2x's directly on the outside of your vertical 2x wall framing, prior to sheathing - then spray-foam can be continuous & minimize heat-loss thru the studs - it also makes connection to foundation insulation better.
dew point may not be where you think it is
traditional fiberglass & poly just plain doesn't work
again - www.buildingscience.com - are the gurus on air, vapor, insulation, mold, etc, etc - in all climates
cheers !
http://www.civil.uwaterloo.ca/beg/Downloads/ASHRAE%20Journal%20Jan%202002%20Moisture.pdf
www.civil.uwaterloo.ca/beg/index.htm
www.corbond.com
http://www.civil.uwaterloo.ca/beg/links_and_downloads.htm
mold. the asbestos of the 21st century. is my nose bleeding?
throw a door over the hole and pile on a few shovel fulls of dirt...
whoa, wait. how do i get into the hole once the dirt's piled on?
i wonder about this condensation topic in regards to the (northern european?) solid foam prefab type walls (sorry i'm ignorant of brand names)
oh, and haybale construction :-)
there are many vapor issues with SIPs as well. the details given by the manufacturer require a 4mil vapor barrier on the warm side of the wall. the panels also don't allow enough airflow through the walls - i am assuming you get a similar condition with spray foam - and you get sick building syndrome. you have to detail a HVAC system that circulates the air properly. this becomes a problem when you have a radiant floor heat system.
vapor barriers are so cheap $.01/sf.
why not have one on each side of the wall??? then there can be no seasonal issues.
If the wall studs were properly dried and not soaked on the construction site before installation, then the moisture trapped in the wall will be minimal - 20% or less and then no mold!
For tight buildings (ie most high perfomance structures) the key is designed ventilation to keep the IAQ healthy. It's much better to have air flowing through ducts/intakes then infiltrating through sloppy construction.
typical northern climate residences in my region, not requiring air-conditioning, generally utilize hot-water baseboard or radiant heating systems rather than air systems.
spray-foam & SIPs wall insulation systems create much tighter envelopes than traditional construction. thus - heat recovery ventilators are highly recommended - for controlled ventilation
The warm side of the wall changes with the seasons. Hence the main problem with vapour barriers. You need two. One for cooling and one for heating seasons for the climates where you need both heating and cooling.
treekiller - one of the fiberglass insulation manufacturers actually has a product where the fiberglass is entirely encapsulated within a poly (vapor barrier) bag - a better solution than traditional, but not entirely without glitches
in so cal, they house wrap with plastic (tyvek) and use plastic face fiberglass insulation inside. not that we have extreme in/out temperature shifts. i've never house wrapped to this date.
a lot of it is a big hype coming from lawyers, plastic manufacturers and mid age mothers/fathers of infants.
i mean. i've seen a lot of bldgs with no vpr bar. that have no problem btwn walls and on surface.
but i am talking about so cal. i am aware the temp dif. is much more greater in some other parts. where vpr barriering is a science to be wreckoned.
Because the exterior side of the wall is designed with a circulated air space between the brick and the studs the air movement acts to dry out the trapped humidity which limits the amount of rot and mold growth to a few months of the year. The cicle of deterioration works at a pace of about 20 to 30 years before there are noticiable problems.
This kind of explains who it generally works today.
m-c
so have you considered increasing your air space (between brick and sheathing) to 4 or 5 inches, and spray-foaming the outside face of the sheathing (before brick goes up) leaving 1.5 to 2 inch air space
the foam insulates, creates drainage plain, air barrier & vapor barrier all-in-one, leaving stud space clear for MEP services
this is a standard system we've used for many years
rigid insulation & tape is an alternative to spray-foam
The idea of having moisure condense on a V.B. and then drying it out with a vent space seems to work. So why not adapt a material that absorbes moisture and then dries out with ventilation without ill effects?
Lawsuits, again.
http://www.kstrom.net/isk/maps/houses/igloo.html
http://home.no.net/gedra/igloo_bg.htm
ventilation
http://www.benmeadows.com/refinfo/Tips/Article1.htm
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