Exterior insulation retrofit: walls and unvented roof
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- čas přidán 19. 10. 2015
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Wrapping an old house in a blanket of insulation is a no-brainer when you're replacing the roofing and siding anyway
Adding exterior insulation to the roof and walls of an old house can improve comfort and energy efficiency.
It especially makes sense if the rafter cavities are already insulated, and it is most affordable when the roof and siding need replacement.
Step-by-step:
The first order of business is to strip the walls and roof.
Next, cut off the rafter tails so that the connection between roof and walls can be sealed with peel and stick membrane.
Cover the roof with a waterproof barrier or membrane.
Install two layers of foam to the roof, staggering the seams, and offsetting the joints, and tape the seams on the top layer.
New roof sheathing goes on top screwed into the framing an inch and a half
Cover the roof deck with roofing underlayment that will protect against liquid water, but allow vapor to escape.
At the bottom of the wall, bend a piece of coil stock into a J channel to keep the bugs out. The metal is tucked behind the house wrap.
Two layers of insulation go on the walls with the outer layer’s seams taped for an air seal.
Attach a strip of bug screen to the bottom of the wall to keep the ventilation channels clear.
At the corners, weave the foam panels together to disrupt clear air paths between inside and out.
The corners are then wrapped with peel and stick to meet them tight
Furring strips are screwed to the foam an inch and a half into the framing.
The furring provides ventilation space and a solid base for siding.
Box out a soffit at the top of the wall and tie it all together with fascia.
Install the siding, making sure to detail the bug screen tightly at the bottom of the wall.
Continuous insulation, multiple layers of air sealing, and ventilation channels turn a leaky old house into a 21st century home.
The Code:
2012 IECC: SECTION R402 BUILDING THERMAL ENVELOPE
2012 IRC: SECTION R806 ROOF VENTILATION | SECTION R906 ROOF INSULATION
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Well done. Would love to see this done with exposed rafter tails applied (as opposed to boxed soffit).
Thank you for the great video! What is the fastener pattern for those (8"?) lag screws?
I really appreciate this info! I have been remodeling a house we bought 3 years ago and it’s gonna get a new roof, siding, and windows this fall and I have been digging for information about this. I was wondering if it was possible to install foam on top of the existing sheathing and basically making my own site made sips panels a piece at a time to insulate the entire capsule and found this info now so it is possible and has been done ✅.
What have your experiences been on dealing with the building inspectors on this process? Have they been educated on building science yet that you know of? Are you guys having any problems with inspections on this process?
I’m trying to soak up all the info I can from you guys that actually have field experience with it before I start on the exterior. I already stripped the entire inside down to the studs and vaulted ceilings in the kitchen, living room, and dining room. We have rewired and replumbed the entire home. I will be installing a new split ac/heat pump system that’s a 27 deer. All new appliances etc. it will be a new home when we finally complete it all wrapped around a 1940 frame. Goal is to have a comfortable home with extremely low utility bills and many thanks go out to guys like you that are putting out info for guys like me to follow along.
I used to be a custom builder but have been out of the industry since early 2000’s due to a crippling injury that left me unable to continue to build and I just haven’t kept up with everything like I should have and so many changes have taken place in the past 15 years with new methods and products and I really wish I was still in the field cause it seems like an exciting time to be in construction if your into the building science pathway.
Anyways, thank you so much for the info and I will keep my eyes open for more info from you guys.
What about with brick siding?
Super easy!!!
I used this same setup but used a fairly non permeable (not vapor open) roofing underlayment on top of the second osb. Is the vapor permeability primarily for potential leaks or for drying due to potential condensation? Thanks!
I was really hopeful... until it got to the "remove siding" bit. That's a problem when you have a brick house. Can the roof be done alone on a house with a brick facade?
What is the detail at top of siding for rain screen ventilation ? Near the eave.
@@ProTradeCraft this is the video the question was about ;)
When you're running screws through 4" of rigid insulation, can you actually walk on the decking to install the shingles? It seems like the force component that would be redirected down the roof parallel with the sheathing would work to bend or snap off the screws. For that matter, how do you get the 1st layer of insulation to stick while you're adding the 2nd layer? Is there a technique to this that will keep the workers safe?
Yup, I am also interested in these more practical questions. The youtube search continues while I try to find someone who filmed the real life process.
You should probably add blocking too the bottom course of the insulation at the bottom and top of the roof.. do the same to the next course of insulation.. at the bottom of the roof where the gutters are add blocking to keep the insulation from sliding down.. I hope that kinda makes sense.. I'll try to send you a little to a good video
How would you design a shed office with a single-slope, lean-to roof with overhangs? Specifically, how would you finish the exposed insulation faces on the sloped edge of the roof? Speaking of a construction with continuous exterior insulation.
The exact same what as drawn in this animation, which only shows half a gable, so technically, a shed roof.
It is best to add overhangs outside the insulation instead of letting them protrude through it.
So what happens to the build-up of vapour within the house.....I’m hoping ventilation will be added or a industrial dehumidifier installed.
Of course 'Ventilate right' is the second half of the building scientist's battle cry, Built Tight, Ventilate Right!
This animation covers one small aspect of the 'build tight' part!
If I’m building a new house. How much extra am I throwing at my house using this method?
Any example will work, by sq ft or comparing apples to apples. 1500 sq ft home with traditional insulation vs. this new stuff.
Michael Howell This is seemlier to SIP technology.. Take a look at Structural Insulated Panels. You can build twice as fast cutting labor cost and higher R Values and air tightness. www.premiersips.com or sips.org
Hi, how do you do this with a concrete block house?
Do you have a video?
We do not have exterior insulation over concrete, but I assume it would be easier than wood framing.
Looks great! So, does "Install two layers of foam" total about 4 inches? Thanks.
Exactly 4" yes but take the additional decking into account.
In this hypothetical instance, it does.
In Georgia, the answer will be different than in Minnesota.
Where's the Windows?
(Recessed at least 4 inches)
Seems like a fairly important detail that this video ignores
Also how do you do with the gable ends ?
Add a board to cover the insulation. Google says to use a board that is 18 mm or 3/4" thick and treated wood will last longer and is preferred. Think about it before you start the project and write down what you are going to do. I am about to do this and I think I'm going to extend the decking out 3/4 " to attach the fascia board to from below and then I'm going to tie it into the old existing fascia board vertically and add a metal aluminum fascia strip on the whole perimeter of the house if I can find the right stuff or else Ill just paint it. Make a video and post it here when you do it. I've been looking for this answer too.
do you even need that top layer of osb? the foam boards are hard enough
If you want to use shingles for roofing, you'll need a mailing base.
that first wall sheathing is just overhanging the foundation unprotected? seems like a great way for mice to get in. also not sure that bug screen would be enough for mice either.
Look at 1:13 where the coil stock protects the underside of the insulation.
Yes, how do you install windows and doors outside of all that insulation? The insulation will not support them
I am glad you asked, Mike! Here are a couple of projects showing how to install windows in a house with exterior foam:
Installing innies: czcams.com/video/V7_2IOLhDi4/video.html
Trimming innies: czcams.com/video/G5-T3VsF87I/video.html
Installing Outies:
czcams.com/video/KjCy2yjzOVQ/video.html
czcams.com/video/o9P0ifcBXIc/video.html
czcams.com/video/DAwFSxxpIk0/video.html
czcams.com/video/4I0tydrCyvE/video.html
There is also a series on installing in-betweenies, but I'm gonna make you search for it!
thanks for watching,
Dan
@@ProTradeCraft Oh wow! Where did you get normal European windows from?
I’m curious if we can also use spray insulation to cover the outside of the house. On my deployment to Afghanistan we covered a massive metal building on the outside with spray insulation. I came back to Afghanistan years later and it was still holding strong.
No exterior protection! Extreme winds and dust! It snowed so much that year I built an igloo! It wasn’t beautiful. Just insulation vs. nature and that stuff held up amazingly.
Make sure you use closed cell spray insulation. Open cell acts as a sponge and absorbs as much moisture as it is possible. Closed cell insulation does not absorb moisture.
It wouldn’t be straight. You would have wavy walls when you went to put up the siding.
Your neighbors will surely hate you if they can see it.
I’m building a new house with an unvented roof but my contractor just backed out of doing the roof because the shingles warranty doesn’t cover unvented roofs. Looking for a solution. What shingles do you recommend on this build?
czcams.com/video/JmsosK2My6o/video.html
How much R-value are you adding? What is the dimension of the ridged foam?
The foam is 2". The R-Value is R-10 per sheet so 2 sheets = R-20
At about R-5 per inch, we added four inches of foam to the roof (R-20) and walls. But the amount of insulation and the ratio of R-value on the outside to the R-value in the cavities depends on your climate zone. Minimum ratios are in the IRC.
I have a house in the mountain I replacing the roof so I am considering adding foam as described, However there is no attic space all open beam vaulted ceilings, Is there a problem with condensation or moisture in this situation,
Yes there will be a build up of vapour within the ceiling or loft space, you will need to install roof ventilating if it’s a hot roofing system.
Hello,
Is it also the best way to build a NEW house, or is it only to improve an old one ?
It is way better to build a new house with 2x10's or 2x12's and add the insulation in the rafters before you finish the interior. Closed Cell spray foam insulation seems to be the best option but do your own research if you want to do this.
Check out Matt Risinger's channel; he has built a number of new homes with exterior layers of insulation. Apparently it is becoming standard building code for northern areas. Exterior insulation has many benefits, but does increase construction costs.
This is an excellent way to build new houses. In fact, people have been doing it for years. go to buildingscience.com for the best information.
Exterior insulation is better at stopping thermal bridging than cavity insulation, so even if you deepen the studs to 2x8, there are still thermal bridging issues.
@@computergroove cavity insulation doesn't stop thermal bridging. Continuous insulation does.
@@ProTradeCraft I figured that was implied.
The big issue I have with this video is that they aren't showing what happens to the doors and windows. Now the foam is four inches to far out. You have to now move the windows out and have a proper sill for the the windows. What a pain that would be!!!!!
As for the roof, it could be done. My older house has insulation in the rafters but no way to vent off the heat so it absorbs to the upstairs
You have two options. You can do an innie or an outtie opening. For an outtie you just buck out the width of the insulation. Thermal buck is designed for this purpose. Or you could install normally and frame out an exterior jamb.
@@Adm_Guirk thanks
Bee Bob, There are a few options for windows, innies, outies, or in-betweenies.
Innies: czcams.com/video/7OX1_q-P5xw/video.html
here's actual guys building it: czcams.com/video/G5-T3VsF87I/video.html
Outies: czcams.com/video/yTlYthfnoeQ/video.html
in-betweenies: czcams.com/video/w4dN1mSC4O8/video.html
Dig around the channel for superinsulated sunroom for a video series about how to install outies and here's an in-depth playlist of a retrofit with innies: czcams.com/video/-ICsETRWfow/video.html
Does that make the attic unventilated now?
Well, if there are no gable vents and the windows are closed, yes. It is now almost living space.
What if your cladding is brick and mortar?
Then it is a LOT more difficult and expensive to remove and replace. Superinsulating from the inside may be a better option, though I have seen builders spray foam the outside of a masonry block home with a system of 2x2s bolted to angle brackets screwed into mortar joints to create a space for three inches of high-density spray-foam insulation plus an air space. The 2x2s were used to fasten Hardy Plank siding into.
An unformatted page explaining the system is on green Building Advisor, here: www.greenbuildingadvisor.com/green-homes/deep-energy-makeover-one-step-at-a-time
Thanks for your video.
I live in AZ and I'm looking for a SUPER cheap and easy options.
Like spraying another 2-3 inches of stucco/chicken wire onto the exterior walls.
Or simply attaching another layer of asphalt roof shingles over a new layer of rigid foam + foil ?
Probably not as effective, but maybe close, at a fraction of the cost?
I would suggest not trying to do this super cheap. Best way to get it cheap is to do it yourself - IF YOU HAVE EXPERIENCE DOING THIS KIND OF WORK. You have 2 options, What the video above says or a tear out of the interior walls and ceiling of the upper floor/roof area and insulate. I just did the later and I am going to now do the former. You need an R-value of R-38 or above on your roof level. The above will only add R-20 to what you already have.
Sell your house and rent
Also add rockwool when u have the wall cavity open
The drywall is not removed in this animation, but when the siding id off, it is CERTAINLY a good opportunity to blow insulation into the stud cavities.
@@ProTradeCraftor just do 3" of closed cell spray foam with ZIP-R for sheathing! this is what i'm planning to do to replace my EIFS stucco soon
do I need to vent the roof?
Not for an unvented design, but there is also a vented version of this if you dig around.
Your house needs windows?
Will there be problem with rot or mold since old were meant to breathe
dieselpower456 No. The sheathing is in the conditioned space with this method. Most of the water will never make it past the siding, furring strip gap, foam layers, then house wrap. Interior moisture won’t have a cold surface to condense on. You will need power ventilation for indoor air quality.
That L channel on the bottom will just become a water bowl. Need drain holes, otherwise any condensation or wind driven rain will just accumulate in there and cause the sheeting to rot.
No it won't it is taped to the face of the foam. and there is a 3/4 inch drainage channel in front of the tape.
@@ProTradeCraft Rain screen and tape don’t change the fact there’s no drainage in the channel. There is internal vapor drive from inside of the house and the insulation can also be vapor permeable if it is EPS/XPS. It also requires the assembly to be 100% perfect for bulk water not to get in, which is never the case on a real job site.
@@mintheman7 I too fear this. Is there an easy way to perforate the aluminum? Also don't want mice in foam
I'm cutting into my wall of my room to make an exit.
Alien Slayer ok
I would’ve made an entrance, but that’s just me....
This system would be much better with ventilation between the foam and roof plywood. Easily done by adding 1.5” sleepers between the foam and roof sheeting. Then you can run them down to help with the overhang construction.
Funny you should say that: czcams.com/video/o5uGtQNi7gs/video.html
:)
@@ProTradeCraft so why post this video? I watched it and did most of my house just like your video showed. Then I see your next video saying how much better it is having a vented roof over the hard foam .......not so funny you should say that
bottom of wall plywood needs to be capped otherwise there's going to be dry rot traveling up the plywood
There is no such an anomaly as "dry rot". Rot has to have moisture to start.
Jay Brown I think he means if that plywood is touching the ground it will soak up water by capillary action. It shouldn’t touch the ground and yes needs something to block water.
@@mjlyco9752 Even just inches from the ground will result in so-called "dry rot." Each time it rains, water flows over the siding and wets the exposed lower edge. Then it dries. This cycle produces swollen and crumbling siding near the ground. A better strategy is to use moisture proof products, especially near the ground.
This is relatively simple on a house with no windows or doors. Dont we need to know what we do there?
Well, according to engineers, the perfect building has one door, a fridge with beer, and no windows to dramatize you during the inevitable hangover. That being said, buildings usually have windows. Here are a couple of options for windows, but search through the channel, there is a TON of stuff about how to do this.
Innie windows in the thick wall: czcams.com/video/7OX1_q-P5xw/video.html
Outie windows in a thick wall: czcams.com/video/yTlYthfnoeQ/video.html
There are also videos of carpenters doing it. Search for 'superinsulated sunroom'
@@ProTradeCraft I watched the outie one. My interest is adding 4 inches of foam....2+2 to an EXISTING home. Again... its easy on the flats... what about doors and windows that NEVER EVER want to trap water. Thats what i want to do to my home... remove and replace vinyl with 4 inches foam to add R20. Thanks
@@rogerwhiting9310
czcams.com/video/19p35Owyd4c/video.html
czcams.com/video/X-YowdOsTP8/video.html
@@ProTradeCraft thanks... I watched both of those. I will have to replay them 10 times to get the tape, flashing, pan, etc details correct. Interesting the job is about 45 minutes from my home. After watching them pinch panels in to be super tight... would there be a downside to just foaming between panels to be tight... and watertight? Thanks for your help. It is a doable project now.
1:10 - SIGNIFICANT thermal bridge there - a widespread problem.
I'm thinking a "Z" channel tap-conned into the concrete wall would be better...it also would serve as a bug barrier for the sheathing. Also should consider air sealing the base of the wall sheathing to the concrete
@@mattcantrell5640 That metal Z-channel would also be a significant thermal bridge. Steel conducts heat 300 times better than wood. If the relevant metal could be replaced with PVC flashing, the thermal bridge would vanish. Ideally, insulation in the wall should hook up with the insulation in the floor. More than one way that can be achieved.
@@elbuggo I understand metal conducting heat, but it would be conducting it to the concrete, not the wall. The concrete would likely be insulated on the interior prior to finishing.
@@mattcantrell5640Studied this again. The flashing is fastened to some OSB board(?) there. That will reduce the thermal bridge significantly. Something green behind that OSB too. Insulation? Well, maybe not so terribly bad solution, but not ideal either.
This roof is not ventilated. Since snow is an insulator, the gutters will fill with ice and an ice dam will be created. It MIGHT not leak into the house but it'll be there none the less. Also, this house it too tight not to have controlled air exchanges, such as would be provided by a HRV.
One other thing... will the warranty on the new shingles be valid with a system like this? That roof decking if going to get very hot if the shingles are dark, with no ventilation to cool it.
They've been doing the ventilated version in Boston, or the version shown here?
I mentioned the HRV because this video is basically saying, "do this" next time you do your roof and siding. There's more to it.
I've read a fair amount and watched a number of videos on building science and tight houses, and the one thing that seems to always be missing is how do you get makeup air for exhaust fans and the dryer? No resource I've seen really tackles this subject, and IMO, it's the elephant in the room. A single, affordable HRV doesn't seem like enough for the bathrooms. I currently have 3 bathroom exhaust fans, 2x 120 CFM and 1x 80 CFM. That's a lot of CFM for an affordable HRV and it doesn't touch the kitchen exhaust or the dryer... and I really don't see an HRV being practical for a dryer because of all the lint. Can you please shed some light on how this is done in this type of house?
Either will work if constructed by a pro? If either works, how can the more expensive option be better? Lol. Just messing with ya. You cannot get away from physics and physics says that if it's freezing cold outside. And warm inside, the unvented roof deck will be a temperature somewhere between the inside air and outside air. This temperature will be determined by the ratio of the R values of the insulation and snow covering the deck. I'll admit there is probably a narrow band of temperature vs snow thickness that would be problematic but it exists nonetheless. Vented also suffers this problem but to a lesser degree.
The makeup air needs to be all fleshed out. Simply saying temper the air isn't enough because, for example, when you bring in cold winter air to a more humid warm interior, and mix the air, condensation can and often does form. In summer, bringing in outside air may dump a lot of humidity into the house. IMO, due attention has not beeg given to the details of this subject and how to mitigate the issues that can arise.
In winter, a product in the makeup air vent that acts like a hair dryer, warming the incoming air to 70 deg, would probably suffice for intermittent needs. A temperature sensor on the heated air could control the heating element. Summer is more difficult and humidity would have to be removed quickly without freezing the air. I'm not sure of a good way to do that. Maybe it's enough to just knock it down a bit. Anyway, details details details. The building industry readily supplies details for everything else, but this subject is sorely lacking.
WRONG!, you should of added 2x2 furring on top of the two layers of roof insulation and then put the OSB ON top to give you a vented space. If you live in a cooling zone you can also put radient foil down to reflect the heat or just use white shingles. or metal roofing.
Well, no, not wrong. One way.
Here's a vented option: czcams.com/video/o5uGtQNi7gs/video.html
It actually does show that @1:19. I was going to comment on the discrepancy.
If you've got a house that has some character and architectural quality this idea is a disaster. But.....there were a good many homes built in the 1970's and 80's that were poorly built and are typically devoid of architectural features of any merit that would be good candidates for this approach.
no way.never ever
Narrator has spit in mouth and is impossible to listen to.