Vapor Barriers: Need one or not?
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- čas přidán 25. 01. 2018
- Vapor Barriers - When to use them, & when to NOT.. On this special edition of the Build Show Matt takes us on a guided tour through the ins and outs of Vapor Barriers from the studio (Building Science Layer)
buildingscience.com/book-cate...
www.greenbuildingadvisor.com/b...
www.energyvanguard.com/blog/5...
en.wikipedia.org/wiki/Vapor_b...
www.finehomebuilding.com/2010/...
rbservis.com/interior-wall-va...
/ risingerbuild
www.mattrisinger.com
Huge thanks to our Show sponsors USG/Tremco, Polywall, Huber, Dorken Delta, Prosoco, Marvin Windows, Roxul & Endura for helping to make these videos possible! These are all trusted companies that Matt has worked with for years and trusts their products in the homes he builds.
www.Securockexoair.com/en.html
www.Dorken.com
www.Poly-Wall.com
www.Huberwood.com
www.Prosoco.com
www.Marvin.com
www.Roxul.com
www.EnduraProducts.com
Thanks Matt, I have been following your videos for about a year and really enjoy what you are sharing. It is a real pleasure to watch the younger guys like yourself focus on doing a high quality job. I am retired and don't build much in more. I make furniture for fun.
thanks for helping us with concerns on our homes. I'm in the business of knowledge but i'm blowing away with so much more you can learn to protect your home.
God bless matt.
thanks again
Excellent format, including referencing published articles from knowledgeable sources.
Thanks for breaking it down into a simple format. Some of the use of language in most sites get confusing. Very helpful
Matt, from a LEARNING (aka teaching) perspective, I think you produce some of the best videos anywhere. Explaining reference materials, including real examples, discussing conversationally. Keep it up!
I have been researching this for a few weeks and this man just solved all my problems in 8 minutes. Thank you!
I've been in architecture for almost forty years and have automatically been putting a vapor barrier in behind the drywall because "that's how it's done". This was such an eye opening video. I don't know how may more projects I will be lucky enough to do, but my projects in Houston will certainly be done more correctly than they've been done in the past. I learn something from every single one of Matt's videos.
Matt, thank you SO much for what you do. This was perfect information with good links to even more relevant and in depth info. This is the gold standard for these kinds of videos
loved this format! awesome to see pictures and examples while you’re talking about it. i live at the bottom of zone 4. my parents had an addition done in ‘92. had to tear out some drywall on the south side of the house which gets a lot of sun. a plastic barrier was behind it. the pink insulation was covered in mold at about 5% of the 4x8 space. it only affected the area that was a closet with a louvre door.
Totally blew my mind. I've never heard this before. Thanks for the video and for the resources.
Loved this format. Very informative, easy to follow along, and awesome seeing examples from different sources with you talking through them. Do more of these! Thanks Matt!
Oh you read my mind, I have been researching this issue for weeks. Living in Virginia, remodeling a garage into a family room and running Roxul and the question of membrane/barrier is confusing, thank you very much for answering this question. You have helped me so much. As a homeowner/remodeler I have yet to find contractors who's knowledge goes beyond minimal requirements. Thank YOU!
Anne Chovey yes, I’m a relatively clever person, but never specialized in building. I’ve met too many blokes who are nice and have ‘hung out a shingle’ but can’t make convincing logic based arguments to justify why they chose a particular course of action and components for their assemblies. Worst part is when they hear a question they don’t understand they just get blustery and rude instead of being self-confident enough to say ‘I don’t know let’s find out’ really feel like there are more and more CZcams channels like this that allow us all to grow together. Thanks again Matt for being so generous, funny and logical.
This was the perfect video for me, I had a client ask about this yesterday. Thanks!
I liked this, and it will help a lot of people; the regional guidebooks are excellent. I live in the interior of British Columbia, and I can see +40 celsius in the summer, and -40 celsius in the winter. When it's cold outside, and you're cooking, breathing, showering, it is essential that there is an interior vapour barrier on homes in our neck of the woods. We have an AC unit too, and in a hot summer, that can introduce its own set of problems. I'm thinking that a good portion of Canadians absolutely need what your neighbours in Colorado, Minnesota, Wisconsin and North Dakota need.
What do you do in the summer? No sure how to cope with humidity coming one direction in summer and another in winter
Do you need a vapor barrier or just an air barrier that lets the building dry to either side depending on the season?
Good one Matt . . . From across the pond . What you have just described is exactly what I have understood for some time now . It amazes me just how many Builders & in particular , Building Inspectors over here just don't seem able to grasp this concept . A bit of physics and common sense goes a long way . . . Great information & videos . . . . Keep them coming & thanks .
I built some house for a bigger chain style log home company they insisted on plastic over the insulation. In Michigan where I'm from we tried telling the gc it was a horrible idea and explained to him the exact points you brought up. Great information and video. Thanks for all the knowledge and new techniques you share.
Love this! As an insulation contractor we often get asked to put up vapor barriers in homes, and I see it on drawings all the time. I have now made a policy to first try and educate the builder / Architect that is making the recommendation, and then refuse to bid the project unless it is changed.
so just tyvex or tar paper on the outside only ? nothing on the inside?
Best content yet Matt!!! Thank you.
Excellent video, thanks Matt. Lots of these 'way things are done' that often aren't the right way to do things that we need the science behind making the right decision. Super helpful.
Thank you for all the great ideas and the educational support you provide. Have a good day.
Getting ready to start the design process and this is the exact kind of video I’m looking for! Great stuff Matt!
How did your project turn out? What method did you go with? I find the more digging you do in vapor barriers/insulation, the more questions come to light. Who's right and what's right for my situation.
@@chrisalister2297 Project went great! We live in a mild climate and code requires that we use, at minimum, a vapor barrier primer paint on the drywall which is the preferred method in our area and probably most cost effective. I’ll let you know If it is the right choice in 30+ years if we ever remodel and find damage or mold. There is,....what is right....what is required by code....and what is done. I can’t answer any of that for your situation. Good luck.
Love the format because the info was great! keep it up, thanks.
Thanks, Matt. This video outlines just one of the things I didn't know when we built our first house, but I'm certainly glad I saw this video while we're still in the planning for our next (and hopefully our last) house.
format was good. precicely what i was searching for. I keep coming back to your channel. you are killing it man!
Thank you very much! I'm building a house, using Rockwool and couldn't find a good answer to the question of interior poly. I put it on and got condensation on the south wall. I'm going to remove all of it now before I sheetrock. Also, don't paint the exterior a dark color. The heat gain is tremendous in a hot climate. I used a dark brown color and I'm repainting it now. Never thought about it, just liked the look. Oh well, pale yellow will be good too.
Thank you! For helping with a do/don't plastic sheeting argument!!
Thank you. You just saved me a full step in my remodel!!!
I love this format. Short, to the point, but well backed up with resources and reason. Much appreciated.
Thanks Greg!
Great format, I like the clear references like the wall cross section. I'd love to see more videos like this. Also, your lighting is spot-on, looks great!!
OMG, this was perfect! I was looking for a book that could help me with the Hot/Humid climate here in Florida and voila, you mention it! Thank you so much!
I'm a homeowner, thinking of building in northern Idaho, love all of your info, esp when you are "super geeky"
Awesome content, delivery, format...this was extremely thorough and definitive. I've asked many builders this question and never got an answer I was comfortable with. Thanks to your video I do not need to ask this question again! Thanks. Great Info. I can't wait to see what else you talk about.
Sorry, I don't think this synopsis was very thorough and definitive. Whether or not a barrier is needed is secondary to what the building code dictates in your state. I would hate to have to tear my job apart after completion to add the barrier afterwards should an inspector come out. I am removing and replacing my under the sink kitchen cabinet and the cabinet next to it and live in Buffalo NY.
I am going to be building several rental homes and wanted to educate myself about multiple topics regarding construction. Your site is simply the best. I learn so much by listening to the topics you present. Many thanks.
I have been in residential construction for 47 years and I find your videos very informative. I thought I had all the information necessary for building houses but your videos have showed me that all that information was based on the codes and recommendations from the old school. Thank you for showing me there is always something new and information to learn in this fastening industry. I am 72 years old and getting ready to self contract our retirement home in the panhandle of Florida. This video will help me with important decisions. Thank you.
Dave, Its this attitude that I wish I could find in the North Ga Mtns where I live. Builders always say this is the way my daddy did it etc. Good for you for not being to old to use your brain and speak out. We are never to old to learn.
Dave im 53 and I can only hope I still have your attitude when im your age. Stay young brother
Thanks very much. I've been planning a redo, but could never talk myself into installing a vapor barrier. It always seemed counterintuitive.
Happy Friday Matt! Amazing free information! Thank you.
Thanks so much... I'm an old house carpenter in New England who has had multiple disagreements with building inspectors on this topic . Keep up the good work!
Thanks for the explanation.
Living in Australia 🇦🇺 I struggled to understand the difference between all the different types of barriers used and when you should use them. Some on the inside some on the outside, some in use both inside and outside in some areas. When you add closed cell foam into the mix too it’s just confusing.
You wouldn’t believe the relaxed “standard” used down here. I’m living in a house (one I’m sure that was built by first year apprentices) it has only a single single brick wall with a 25- 50 mm air gap to a 2x4 wall frame with gyprock (Sheetrock). Yep no wall insulation at all. And this property was built in 2005.
In the roof cavity I have 10 mm gyprock and corrugated iron (tin roofing). That’s in.
There’s now a standard to adhere to which requires us to build stud walls with R1.5 batts. I’m not sure of the required R value in the ceiling cavity but what ever it is, it’s very relaxed.
I built an investment home in 2002 and I asked the builder to use anticon under the roofing iron together with R3.6 batts on the ceiling. My builder told me I was just waisting my money with the anitcon. (Anticon is a anti condescending insulation. It’s a quite thick foil type material with fibreglass insulation attached to it, R1.5) to purchase it in large roles.
As an electrician I loved working in this ceiling cavity, others without the under iron insulation were crazy hot, you could only work in that space for a limited time as it was so hot. But my property was was warm but not overwhelmingly hot.
I can’t understand why we don’t try to better insulate our home’s.
Thanks for the great content.
Cam.
Thanks for sharing Cameron. We're looking to buy our first Aus home, coming from the UK the lack of insulation here is shocking. We're basically resigned to the idea of needing to install insulation in whatever we buy. Did you find any good Aus specific resources regarding vapour barriers? The wide temperature variation here made us think we'll need it on both sides. Cheers
Great format! I used to be a home inspector in Michigan, and building my own house in Norway, #jarleifhouse, sure is different from the houses I inspected in Michigan. Balanced ventilation is required on new construction over here, as is a vapor barrier, as the houses are pressure tested prior to finalization and COO. The only exception; Log homes. Keep the great content coming! :)
That was one of your better videos, Matt. Appreciate you walking through these topics.
Matt, this video is excellent. A pleasure to watch, very well explained ( like always) and contains a lot of great information.
I really appreciate your guidance, and the time you spent making this video.
Best Regards,
Peter
What I get out of this is that you should try to have slight negative pressure in your house during the winter and slight positive pressure during air conditioned periods. That way, anywhere there's an air leak it will be cool (dryer) air which will be able to absorb and carry away moisture as it moves into a warmer part of the wall, floor, or roof.
that is an inspiring thought
Nice video buddy, & yeah the format was cool!
I love every way you bring content because of its high value.
Great video!! Thanks for the info. Very helpful! Really liked the format too. The articles and diagrams were very helpful. Enjoy all your vids and the resources you site.
I am in building zone 7 , Winnipeg Canada, All houses her have poly vapor barriers. I remember our old house that had no barrier and the humidity would go in the attic and freeze on the underside of the roof and in the spring time huge chunks of ice could be heard falling and banging on the ceiling , wetting all the insulation in the attic and ruining it. Since all houses have basements , there is usually no problem with ground rain water seeping in from the bottom. So all the houses are up a couple of feet above grade.
I put my sofa up against the outside wall and the sofa had a straight back. it was -35 outside and I have R30 walls. so I pulled the sofa away from the wall to vacuum and there was Ice on the wall. The Insulation in the sofa up against the wall brought the freezing point to the inside of the house and the humid air froze on the wall. That is when I realized how important the vapor barrier was.
What if you had a tight air barrier but not a vapor barrier- would diffusion still be an issue?
@@rsmith02 As far as I know the Tyvek and other brands of air barriers are designed to allow water vapor to pass through so it doesn't get trapped in the middle of the wall. You still need a vapor barrier inside the house walls. If it is an old house with no vapor barrier , you can use oil based enamel paint on the walls and ceilings and that works. If you live in a hot climate then you need the vapor barrier on the outside of the house to stop humid air from entering the walls and condensing in the middle of the walls to which could form mold. That happens when you have A/C making the inside air colder than the outside.
Matt, love this video, and I absolutely encourage you to do more like it. Maybe even a monthly video formatted like this called Nerding Out With Risinger and talk solely about a building science concept. What do you think about Lstiburek’s idea about a vapor retarder over your water control layer but behind your vented cladding. That way any condensation can gather on your water control layer and safely drain out. Hope I’m not misquoting him!
This is an excellent idea!
Yep, love the format. Love learning the technicals.
loved this video as well
Your video is very helpful. Literally 100's of opinions on this topic. You sound clear and concise. I like the references.
So good to see you addressing this correctly. I fight with builders and the occasional inspector over this regularly. Building Science for the win.
Hey Matt I’m currently building a new construction home and after watching some of your videos and others I decided to air seal and insulate my home myself. I have a vaulted great room area and I didn’t want to have to try and walk on that to blow cellulose and a local surplus store listed some R49 unfaced batts for 30$ a bag so I snagged some up for that portion of my attic. I live in climate zone 4 in central KY. If my ceiling is properly air sealed will the unfaced batts be okay?
Crazy humid in Central Florida for about 7 months a year. I had a “over “ wrapped wall that couldn’t breathe and it couldn’t release trapped water as a vapor.
Major rotting occurred.
It’s not so much water getting into the wall here or there (it’s going to get in somewhere) question is, can it get out?
It needs a way out on the less humid side.
I would think in HIGH humidity areas, spray foam would be your friend. That seals the wood and stops air flow all together.
Thank you for taking the time to explain this logically. Building inspectors simply parrot what someone told them and never check the science behind what they prescribe. I once had a building inspector tell me that my new patio needed to be able to remain standing if the house fell down. I asked him to explain to me under what circumstances he could envision my my house falling down and not the patio with it, and he just stared at me and then finally said, "well, that's what they told me we needed to look for."
That's insane. So many building inspectors just follow what they were told (as you already stated) or got it from a manual, but don't fundamentally understand any of the science behind the "why". Or, and the worst, is a perpetuated myth in building science that gets passed from inspector to inspector that becomes the norm, when it was never based on fact.
Great video! It is something I've come to suspect in recent years. It's nice to know that someone more experienced than I am has come to the same conclusion.
Good job Matt, I've wondered about this subject. Keep it go'in.
Thanks Matt. Might be worth mentioning the article “how to kill an old house” for those of us renovating homes. My PNW vintage craftsman was redone years ago and every wall I open has pink stuff in plastic from that reno, all beginning to turn black. Removing as I go. Short of removing all the historic cedar siding to insulate the envelope ala green building or perfect wall, I don’t think I have found any good choices for insulating walls of an historic house. None seems the consensus; that’s a hard pill to swallow in a hundred year old house. I’ve used some rockwool and bo barrier, in hopes it will hold up better over the next 20 years and make the house a bit more comfortable.
He’s got another video where they insulated a 100 yr old house in Texas. They use something called Delta Dry to create a cavity next the siding so it can breathe. Then they put a weatherproof sheet over that, THEN insulation goes in. I did it on my old house.That might work for ya!
This is fantastic, love the science in your building science posts, thank you so much for this! And all the others too!
Great video! Answered all my questions and didn’t focus on one specific zone. PERFECT!
Loved the reference material as well.
Matt, you forgot to mention that the driving force moving moisture through a wall is vapor pressure. Why else would moisture move? Secondly, temperature differential is what drives heat through the wall. One can calculate for a wall composite, given inside and outside temperatures, what the temperature gradient is in the wall and if condensation could occur.
I have seen a PTAC placed such in a building that it was blowing fully saturated 55F air on drywall. While the room side of the drywall looked fine, guess what was on the other side? The blackest mold you have ever seen. The learning is to never have HVAC vents directed against a wall. Lastly, I have seen in hotels where a conditioned guest room (cold) over an ambient work room created mold on the ceiling of the unconditioned and vented work room. The room above made the concrete floor slab so cold, moisture was condensing on the ceiling of the work room.
As a mechanical engineer, I need to find the scientific root cause why there is a problem or what the solution should be. Just using a general chart for certain areas is not always the best method. Using science and physics will always give the correct answer.
30 year builder here ,, thousands of units,, I will tell you exactly what poly on the inside of a house will do,, (in most of the USA)it will rot and or mold and mildew your walls and ext sheathing, rot your studs if wood ,, rust your framing if metal, soak your insulation if fiberglass , especially at bottom of walls effectively making fiberglass batts or any insulation virtually useless when damp.(( mineral wool and closed cell foam excluded)) . We figured that out in the late eighties,. Had many of discussion with unknowing bldg inspectors,, but I always won. But it was always a battle. Best to build a house with the major share of insulation rigid in two or more overlapping layers on exterior,, on top of a water/ air barrier ,, then clad exterior with whatever as long as there is a sufficient drainage plane between cladding and insulation,.. but still place mineral wool inside stud cavities , but i like at least a R 20 or so in exterior overlapping foam,, ((This method I KNOW works most everywhere .. AND DONT PUNCH HOLES IN YOUR WALLS ,,lol ceilings either for that matter . Air sealing from inside is key to thermal performance ,, do not need three dimensional airflow inside wall cavities or ceiling cavities .
BTW good video
Nate, if you were called to finish a basement, and the existing construction did not have the 2 layer of rigid isolation on the exterior, how would you go about framing the basement walls in regards to insulation and vapor barrier. This is for the new england area.
Nate. Same question about basement vapor barrier
I love that u address building strategies vary greatly in different parts of the country !! So many DIY channels dont say where they are located. They are only telling people 1 way to do a project and that may not be the best way given location of viewer...
Great coverage of an important topic. I've been building an 8x12ft RV and following your vlogs and have found them valuable for everything from wall construction, window openings and of course moisture control including vapour barriers. I've found that a lot of what goes into home construction can be applied to RV construction. I've also found that a lot of ready made RV's don't do a lot when it comes to vapour control. My RV's walls are made with 2x3 wood studs with plywood sheathing covered in Soprema Sopraseal Stick VP. Walls are insulated with Rockwool insulation and the decision was made to forgo the vapour barrier completely knowing that RV's especially can become really humid really fast. Thanks for detailed content and real world examples in all of your videos.
I too am here wondering what to do with my van build. I live in hot humid south but plan to go north west…but don’t really plan to do long-term in snow climates.
Since I live in Wisconsin and going to insulate my garage I think I will use a plastic sheet for vapor barrier.
You point out that in the colder zones that the sheet rock slows down the movement of moisture through the walls and that is enough except in zone 7. But then you point out that air leakage through cracks, crevices or holes in the sheet rock can allow seriously damaging amounts of water through the walls. In my opinion, this is exactly why you need a vapor barrier that can flex and stretch and cover cracks due to settlement and a barrier that can be sealed around electrical boxes such as receptacles switches land lights etc. such that a little movement won't rupture the barrier. As the house ages and some home owners drive nails and screws into the sheet rock to mount artwork, these holes are penetrations through the surface and interior of the sheet rock that allow air to flow through. in modern times many people are using humidifiers to maintain a comfortable and healthy humidity in their home in the heating seasons in the north. You can build a theoretical case to allow you to say that under perfect and new conditions, you don't need a vapor barrier; but but with the practicalities of a home as it ages, why not put in the added protection? Of course you can do a lot with flexible caulking to seal around boxes and you still may need that at the boxes when you use a membrane type barrier; but a tough, flexible membrane will be there during most typical structural movements caused by settle-ling or holes made by the home owner. As you pointed out, one thing you do not want is a hole in the wall that allows the warm humid air to continuously flow out through the wall and form condensation in the colder side of the wall; that is big trouble.
Nice video Matt. Very informative and some great references in the description.
Good stuff! Thanks for clearing up the misconceptions.
Most houses I’ve done established a vapor barrier using the paint on drywall. But I’m doing a cabin now with a plywood interior (so no paint). We’re in climate zone 4 and had planned to use plastic behind the plywood but after watching, it seems like the plastic would just encourage mold on the back of the ply. Right?
Yes. Use "Kitchen and Bath" paint in high moisture areas. I do wish more builders would use green board in bathrooms, too many do not.
Thanks Matt I love the geeky stuff!!
Like the format. Like the display references too. Always great info.
Thanks!
Thanks James!
Great video Matt! This is a good addition to your video cache, love to see more building science geek stuff.
It was nice chatting with you at IBS, I’ll keep you posted on my passive house build on Vancouver Island and shoot some video for you. Love your work, Rob.
So no plastic sheeting on my wall but what about closed cell? I’m planning on spraying my walls with closed cell but won’t that be adding a vapor barrier?
Closed cell is a vapor barrier
So when building my post frame structures with metal siding and no plywood or osb sheeting... still no vapor barrier? Great video matt
The answer in my research is “no vapor barriers” for your steel building but an air barrier usually in the form of closed cell foam spray or sheet works best.
Also following both RR and Matt ... What's the answer for my new 40x60 heated post frame building?
I have the same question
Great videos from here and RR. I think it all depends on location but I am not an expert which is why I am here. We just completed the dry in of a large pole barn structure. We are about to begin finishing the interior which will have both conditioned and unconditioned space. We have metal exterior siding over top of general house wrap. We will then bat insulate the interior and cover the walls with drywall. We have been told not to put up any plastic. We are located in northern South Carolina where summers are hot a humidity seems to be year round. I look forward to hearing the reply from Matt.
Depends on your climate. The vapour barrier should go on the warm side if the in/out temperature delta will allow condensation to occur. I live in the north and our typical wall assembly inside out is drywall - furring (allow some air movement to dry out any vapour that diffuses) - vapour barrier (p-e or closed styrofoam panels that will have less than 1 perm) - insulation in the wall cavity - open styrofoam panels( high perm to allow moisture to escape) glued on the back of your sheating - air barrier (tyvek or similar) - furring for air movement to dry any moisture - siding.
I’ve watched this video multiple times now. Super helpful. Thanks!
Good info. Having built and rebuilt several houses, it's nice to know that I did it right! Thanks, Matt
I'm doing a wood floor over a slab that doesn't have a vapor barrier under it. This is in the basement of an old house. I put down one of the new dimpled plastic barriers made for just such an application. I'm wondering if they will really help, or if you have had any experience with this sort of thing. Maybe a subject for another video?
Tom, I think you did right by putting the barrier down, especially over concrete which always will have moisture. Use pressure treated joists also.
august, Yes, I agree there is always moisture. I put down two layers of 1/2" osb glued and stapled together over the barrier. Didn't really have the ceiling height for sleepers.
Tom, I have the same type of house, 1870's and 6' 6'' ceiling. I still think you did all you could other than doing the first layer with pressure treated but there are issues with that so...
august, Yes, it's hard to know how far to take things. I know two layers of ply would have been a lot better than the osb. I guess time will tell.
Watched flooring company do following. 6mil plastic on slab, tape seams properly, pressure treated 2x sleepers on layout of choosing (16 o/c or 24) ply then flooring
How about a video on how to make the walls breath the best? To let any moisture escape
Brent, that was the idea behind houses built in the early 20th century, they just didn't have the science to back it up. Laughing loudly.
Good format and useful information. I encourage you to do more videos like this.
Thanks, Matt, for putting a ton of great information into a short, easy to understand video!
In Canada it is recommended to have a vapour barrier with insulation 2/3 on outside and 1/3 inside. Rim joists or concrete should have R10 rigid insulation on outside to prevent cold from being transferred through the structure.
Like the format, however use either bigger fonts in your browser or lower resolution for your monitor. This will produce more readable screen shots and will require less zooming.
I do like this format, very informative. Lots of facts, well presented. Thanks!
Nice, Great format, trusted resources and most important Information anyone can Understand
What about in basements?
Big problem is actually the use of pink fibreglass insulation as it absorbs moisture and grows black mold. Roxul or isocyanate do not absorb moisture
Thanks for a 'laser clarity moment' on this topic. Cuts right through the gibberish and gets to the point. I really like the format of this presentation over your flashy intros on the your other topics (not to get perspicuity).
Good information and I liked the format. Thanks for posting
What about a vapor barrier on walls in a basement in a zone 6?
shutterassault1 what is the verdict?
I've worked on a few basements in what would be zone 8, except Canada uses different zone numbers. (Go to Fargo, and keep going.) I think Matt is correct about air barriers being more important than vapour barriers. The main problem I see with fibreglass insulation in basements is the sometimes extreme difference in temperature between the footings and the top of the foundation. (Currently about 50 degrees Celsius/ 90 degrees Fahrenheit right next to me.) If you don't have an obsessively tight seal everywhere, this will pull air in at the top of the wall, cool it, and force it out at the bottom. I've been in a lot of houses where you can feel cold air being pushed out of unsealed electrical outlets. In a couple of cases, we had to use heat guns to melt ice that was holding the old insulation solid to the top of the foundation wall. I believe rockwool stops this vertical air movement better than fibreglass, but not as well as Tuck Taping the heck out of every possible opening. Foam insulation works a lot better in basements, but the only area it's really worth the money on a DIY job is in bathrooms.
Get yourself some rigid polystyrene insulation. There’s a lot of options out there. Preferable one with a thermal barrier on the inside. The polystyrene, when installed correctly, will act as a vapor/air barrier in a basement without absorbing the collected moisture. Still, if you end up finishing, drywall and wood studs are a bad idea. You’ll never stop water from coming into the basement. Galvanized steel studs and one of the many cement board brands are the way to go. If your not finishing the basement, remember to never store things in cardboard and get yourself a good, energy star rated dehumidifier.
P.S. do not put an exhaust in a basement. I’ve seen some contractors and waterproofed who put those in. All you end up doing is creating a vacuum for more wet air to fill the space. It’s a never ending battle.
I have pulled many walls apart over the years. Plastic on the inside is a bad idea. That guy Holmes on tv loves it, what a joke. Up here in NY old school tar paper lasts 40 years and looks like new under the siding. Original Tyvek becomes like string from the acids in cedar. If you want a super tight house closed cell foam sprayed would be my choice with 30lb tar paper over plywood. To tight of a house isn’t as good as it sounds. You will have to ad make up air after the fact.
daversj
Tar paper is Ole School. Tyvac is just to keep the inspector happy. Use Zip, Delta or one of the liquor applied. Mat is in to excellence and building science, building home to last centuries, not Twenty years!
I like felt i.e. tar paper for the outside it breaths VS some house wraps that do not breath. Fact I was talked into using high tek roofing underlayment instead of felt, the roofing decking buckled in spots from moisture.
In Holmes defense, he is in Canada which is where Matt is saying you need a moisture barrier. Perhaps not plastic but that is the older school thinking of course.
Agree. I just pulled plastic down an hour after putting it up. Western NY, 90 degree day stapled 6mil plastic after Roxul. It started building moisture immediately. Glad I didn't put drywall up yet. Thank you for this video.
Super-helpful. Thanks. I liked the way you showed us the various reference sources.
I forgot to mention how great your info on poly barriers, great video for sure.
...and the debate rages on! As an architect, people in our industry beat this topic to death about where, when and what type or vapor barriers to use. Problem is we don't know the weak points or flaws until a building is renovated or torn down many years down the road.
In Canada, ALL THE TIME
Yes. But not in the US
how about seattle?
Zone 6 would be the same weather as Alberta and Saskatchewan, and vapour barriers are used 100%. Dont see how a line on a map changes the weather where it "might be" used
audex, You just need a good roof :P
how about a hrv
Keep these vedios running. I'm learning much. Thanks
Thanks Matt, love your format it's very helpful.
Ok, so you don't *need* It, but if you want it, will it cause more problems than it solves?
The answer has to be less because millions of homes have been built using a vapor barrier. If a vapor barrier caused this much mold, mildew, you would be seeing it everywhere, yes ? Not saying which way is right but...
My father used it against the basement foundation so when the concrete weeps it doesn’t go to the insulation.
Probably yes. Read Martin Holladay's thoughts on the subject as pointed out in the video.
I rip houses apart everyday. I almost always see mold when a vapor barrier is used, and almost never when it is not used.
abacab87: Precisely. The vapor barrier has been doing its job - trapping moisture that would otherwise leak into the structure and potentially cause mold. In cold climates, you want these between your insulation and drywall. Unless the home has significant air leaks or moisture issues, the vapor will be trapped on the outside (cold side) of the poly, protecting the interior of the structure including the air you breathe.
This is somewhat dangerous advice to be giving without enforcing how important air sealing is. The 30 pint scenario is very realistic given the way most houses are not sealed at the drywall level, or the weather barrier level on the outside for that matter.
Air sealing is critical, and traditionally it’s done with a plastic sheet in the inside and a housewrap on the outside. Changing that requires a lot of planning ahead and communication between the builder and trades.
Plastic sheet does little to nothing for air sealing. You have holes all over due to things like staples and you have big outlet holes that are rarely if ever sealed around the outlet or at the back wire penetrations, possibly vents, small cracks between the joists and drywall that aren't sealed like at the floor, and my other things other things. The house wrap on the outside has little to nothing to do with air sealing either. Moisture at the surface they are covering, but not air and not the moisture that moves through those cracks and gaps.
Thanks for the information........this is exactly what I needed to know.
Great information!!! I really like this format.
Always good information! Thank you for these awesome videos!
Learned more in your videos in 30 min than all the DIY videos put together thanks!!
Perfect format. Great information from you as usual.
Matt , I like the format that you used I like the way you showed it it was easy to understand not a lot of unnecessary information in there got to the point I’m a do it yourself or 70 year old guy who still working and got some major construction going on my house I’ve been referring to for last year almost 2 years for a lot of my updated what I feel necessities to repair what was wrong with my 17 year old house thanks buddy I think you do an awesome job