Why and How We Install Continuous Exterior Rock Wool Insulation
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- Опубліковано 6 вер 2024
- In this video, I review building science best practices of control layers and the importance and benefit of installing continuous exterior rigid insulation, as well as how we installed four (4") inches of rock wool insulation on the walls and seven (7") inches on the roof of our high performance Marietta project in Georgia.
The report referenced in the video from RDH can be found at this link: cdn01.rockwool...
Insulation by Rockwool North America, www.rockwool.com
- Comforboard 110 on the walls
- TopRock DD on the roofs
Liquid Applied Air & Vapor Membrane by PolyWall, www.poly-wall.com
- Blue Barrier system
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Rain screen furring strips' orientation
The Rain screen furring strips' orientation must be vertical to allow for unobstructed continuous water, air, and moisture flow.
If your siding needs to attach to horizontal furring strips, they must be attached as battens over the required unobstructed vertical furring strips.
Source: Hammer & Hand / Horizontal Rain Screen Furring for Vertical Siding
Was looking for this exact comment. I'd avoid horizontal strips, especially at the window bays. You've made a dam with each one and at the window it will serve as an air dam, so you won't get great airflow through those sections.
Got on the comment section to mention the same thing. From what I can see the horizontal furring strips are insane. Unless he can explain it which I don’t see how he can that horizontals cannot be wood but rather the hard mesh plastic furring strips that allow the water to flow through it.
For the horizontal furring, if you must have it, replace it with Coravent SV5. You've put in place a bunch of air and water dams.
Avoid sections of vertical furring that touch other sections of vertical furring. They will wick water up by capillary action.
Finally, Rockwool isn't rated for use on pitched roofs, only flat ones. The slope is pretty subtle here, so it's probably fine, but I'd check with Rockwool that this install meets their spec.
Yep. Bunch’a dams installed. Love when guys that don’t know wtf they’re doing post video on UA-cam pretending to experts.
Glad to hear about the extra rockwool on the roof - that's what I did for my hermit hut. I did a primitive "double wattle wall" from a 1800 BCE archaeological site design - using on site materials. The roof I added a synthetic rubber pond liner on top of the rock wool - I can REALLY FEEL the difference now! Wow the wood stove heat really stays trapped and absorbs into my wattle and daub side walls, etc. Even though I had lots of air gaps - big leaking air holes and it's sub-freezing arctic cold where I have the hut. So that extra rock wool on the roof - I did TWO layers - yeah it was worth the investment for sure. thanks
@@ducoh2093 I have no idea how standard construction would do it. I wanted a tarp roof to keep my structure as a temporary shelter in case Guvmint got fascist on me. So I have a tarp OVER my rafters - actually willow trees - and the two layers of rock wool - and then another tarp over that. Then when it rained - the rock wool soaked up the water through the tarp - so I put all these clip things attached to the tarp underneath on the inside - so I didn't break through the tarp. Then what? I bought a pool liner - synthetic rubber - to cover on top again - and put a third tarp over that. I used poly-vinyl tarps... At first I wanted my roof to be both breathable AND insulated (hence the rockwool and tarps). The synthetic rubber cut off the breathable part of the roof - and also cut off the Schumann resonance quite a bit. hmmm. Yeah I'm a primitivist.
What a beautiful and thoughtful system.
Thank you for that, Riki
Thanks, Ricki
Hi Chris, thanks for this video. You explained things perfectly. I was wondering if you did some sort of metal "L" trim on the bottom for the insulation to sit on, as well as the furring strips and the exterior wall covering, or is the "coravent" taking care of that?
Also, how did you trim out for the thickness of the exterior for the window openings?
And finally, I'm assuming you put the air barrier, like Tyvek, right under the 4" Rockwool, is that correct? So the layers on the studs are sheathing, Tyvek house wrap, Rockwool, furring strips and finally siding, right?
I think Rockwool is a great product. I will use it on the interior of my last house but for exterior use but it is not cheap. Right now it's about a buck a square foot.
Nice explanation Chris. Why did you put the furring strips horizontal and vertical?
Thanks. I have to read between the lines so to speak as I am building in The southern Philippines about latitude 9. Attaching to the outside of concrete brick walls is tricky. Also obtaining rockwool there is going to be an adventure. NO one in our small town knows anything about insulating any structure. I would like to use rockwool.
Aerated concrete might be better for your location
Interesting! -- QUESTION -- The one thing I can't figure out, is this. Rockwool reminds me of a wool sweater, which is great as long as you wear a wind breaker over the sweater. Otherwise the cold air blows through the sweater and the insulation value of the sweater is zero. Why is Rockwool not the same? To my mind the cold will pass right through it unless you have an air tight covering such as Delta Vent SA or that other one from Siga that is hanged over the exterior insulation.. What are your thoughts on that? Just seems like Rockwool is very porous to air.
Hello, Coleen. Great question. The simple answer is that the rigid mineral/stone wool products are made dense enough to prevent convective loops that cause a reduction in thermal resistance, and it be in direct contact with the continuous air & vapor control layer. VERY loose (density) insulation and poorly installed cavity insulation led to the focus on six-sided encapsulation.
There is additional research regarding "Wind Washing" with exterior insulations in vented rainscreen cladding assemblies done by RDH (John Straube). Here is a link to the report in case you, or another reader, is interested.
www.rockwool.com/syssiteassets/o2-rockwool/documentation/research/white-paper/wind-washing-of-air-permeable-insulation-2018---white-paper.pdf?f=20201024215341
More published info from Building Science Corp (Joe Lstiburek) touches on the science of insulation and best installation practices that may add to my answer to your question. Here is the link to that.
buildingscience.com/documents/information-sheets/installation-of-cavity-insulation
Let me know if I have not answered your question, or if you have additional questions.
@@LGSquared ..after reading the Wind Washing study, I am convinced more than ever, that a WRB be placed over exterior Rockwool and sealed properly. In fact, It would probably be best if there was solid Zip sheathing used. Certainly no downside except for cost. It seems that cold will otherwise make its way behind or through it under almost all installations. I did look up the density of Rockwool since density was focal in the study. I can see why in Matt Risnger's Vancouver BC Canada series, the builders used Siga?? wrap over exterior Rockwool - they never left it uncovered even when there was exterior clading used.
I like the details of the furring strips on the corners; very nice. What type of cladding is going on? Hardy? That wrb liquid looked super thin; that isn't polywall is it? Also interesting you ran the bug screen run the distance at the top of the furring strips. Very nice details! So glad to see these details becoming more prevalent!
Thanks, Consciously Conservative! We used Nichiha brand fiber cement cladding. We find it more stable, with a higher cement to fiber ratio. The liquid applied membrane IS PolyWall Blue Barrier. The minimum thickness throughout ended up 40 MIL, despite aiming for the recommended min. 25-30 MIL. There were some spots as high as 60 and 80 MIL.
Please!! I have the same question. Your roof assembly is exactly what I am doing on the house I am building myself, and I would really appreciate a sketch of how you handle the edging and the core-a-vent on the standing seam metal roof. I also have a low sloping shed roof with no hips or valley to deal with. Thank you.
Good morning, Thomas, check out this video about how we built the overhang withOUT penetrating the building enclosure. If these are not the details you're asking about, please let me know! ua-cam.com/video/ITwTukfd-6U/v-deo.html
Whew Expensive!!
How are you achieving air flow in the areas with horizonal strapping like the two story section and at the corners? Also what happens when you need to get on that roof? The assembly although functional from a building science perspective seems rather delicate.
Good questions, Julian.
The only reason we are using horizontal strapping on that middle section is to have a way to attach the vertically oriented cladding. That cladding is attached with clips that are mounted to the furring strips, and the clips provide a 1/4" - 3/8" gap between the furring strip and the back of the cladding, which is more than adequate for ventilation of this assembly.
RE: Roof design - Check out our video about the outrigger framing that supports the overhang. "Roof Overhangs with Continuous Exterior Insulation" - ua-cam.com/video/ITwTukfd-6U/v-deo.html
The overhang is designed for the same roofing loads as the rest of the roof. Also, if you're asking about whether the insulation is adequate to support a roof load (walking, snow, etc.), here are the Compressive Strength numbers for the product used. The combination of this and the weight distribution provided by the furring strips, the assembly exceeds the design criteria for roof loads in all areas of the country.
COMPRESSIVE STRENGTH (per ASTM C165 &
EN 12430):
Top Layer - 20psi (140kPa) @ 10%, 37psi (250kPa) @ 25%
Entire Board - 11psi (75kPa) @ 10%, 15psi (105kPa) @ 25%
Point Load @ 5 mm Compression - 30psi (205 kPa)
Aha, good to see you have a plan for the horizontal furring sections. I still think you have some problem areas, but part of it makes sense now.
Excellent video Chris! I would like to pick your brain about a modified pier and beam foundation, because we do not want a slab foundation!
Feel free to reach out through the “contact us” page on our website - www.lgsquaredinc.com/contact-us
@@LGSquared Done.
Thanks for the video! This looks like the assembly we're planning on with either 6" or maybe even 8" of exterior Rockwool Comfortboard (we're in Wisconsin so our winters are chilly). I'm wondering how difficult it is to hit the studs accurately when you're sending screws through the furring strips, comfortboard, and sheathing. Was that hard? Any tips for getting that right?
10,000 screws mentioned in the video and to hit rafters through a 1x and 7 inches of insulation is some marksmanship! I have looked into using fiberglass girt clips. You have some slight spot bridging but mounting a bracket to the sheeting and a short screw to the battens is going to be a lot easier to execute and the clips will hold the insulation so you don't need the buttons.
I get the idea of at least 1” embeddement. Since rockwool is compressible how do you achieve flat wall? I would imagine you have to keep checking with level all the time in order to stay flat. My point this must be super time consuming
Do you have a detail or information for your horizontal 1×3's that you used for your wall rain screen. Does it allow bulk water to drain?
William, the cladding is the bulk water management system. So, if bulk water is getting behind the cladding, there are larger issues that would need to be addressed. The moisture that will be behind the cladding is going to be vapor, which will never enough to need drainage off of the 1x4s.
@William - Any moisture that gets behind the siding is airborne, and is usually a vapor. Also, since the assembly is well ventilated, that small amount of moisture dries out very quickly. Bulk water is kept to the outside surfaces of the cladding via the proper installation of cladding and flashing. Any vapor that gets on top of the horizontal strips is trivial and is eliminated through evaporation (expedited by ventilation) before it can even start to build up and become a concern. If bulk water ever enters the cavity in these areas, it would most likely be short-lived and would dry out quickly because of adequate ventilation in the rain screen cavity.
@@LGSquared Why do you think it would only be vapor? It could be wind-driven water.
The furring just floats over the Rockwool ?
Where did you get the screws?
Did the rockwool go down the foundation? How did you protect the exposed rockwool above grade? If stucco, how did you secure hardware cloth or wire? If sheet good, any brackets attached to wall? Good point about the corner trim backing. Thanks. (Working on my 1984 built house, looking to squeeze a few pennies from the heating and cooling bill..)
@LG Squared: What was the brand and type of screw for installing Rockwool? How did you hold up the first layer? Can you describe the assembly for steel cable hung overhangs - looks fantastic!
We used a local company called Triangle Fasteners, and we used their "1/4” DP3 CONCEALOR
With TRI-SEAL® Long-Life Coating"
Chris, excellent, keep up the good work.
Does the liquid applied air/vapor barrier prevent the wall assembly from drying to the outside? As you mentioned, you want to avoid trapping vapor.
Interesting fact. Rockwool is a subsidiary of an oil and gas company. They will allow you to pay them upfront like this building or after the fact in higher energy cost in a standard home. Either way you are going to pay someone’s high prices to own a home.
It all looks great. I wonder how much the insulation for this house costs? I bet it costs more than the whole house I want to build.
Ron, the insulation would cost more than the house you want to build if the house you want to build is under 150 square feet. For this house, the material (insulation, furring strips, screws) and labor cost of the insulation was approximately 7% of the total cost of the house. Being continuous on the outside of the framing, it adds additional value over typical cavity insulation installations. It provides much greater thermal lag, moisture control, thermal break, and protects the structure from expansion and contraction in all climates, even "HOT".
Chris, I have a question. Not a builder, but interested in doing this kind of work on my home. For the roof in particular, how is the air barrier beneath the Rock Wool protected against water intrusion due to condensation at the points that the 9" screws penetrate it?
The wrb is gasketing, that's not the full answer but it's definitely part of it
this channel is gold!
Hi, how are you detailing the seven inches of exposed insulation at the edges of the roof? Any chance you have SketchUp files to share?
Good morning, Helman, check out this video about how we built the overhang withOUT penetrating the building enclosure. I believe these are the details you're asking about, but please let me know! ua-cam.com/video/ITwTukfd-6U/v-deo.html
How does water exit w the battens running horizontally?
Would you recommend this for older homes in California?
I definitely would, Floyd! In fact, we have a client in Boulder, CO, with an existing home in the foothills, that we are planning to remove all cladding and sheathing, and give a "new skin" which would include a continuous layer of exterior rigid stone wool insulation, just like the new house in this video. The house is in a WUI (Wildlife Urban Interface) area, where forest fires threaten the home, much like in California. One of the supreme advantages of having this assembly, with stone wool insulation on the outside, is that is extremely durable against fires. It has the potential to make the home "fire-resistant", when done properly.
Let us know if you have any other questions!
great video. Can we just sheet the house again over the Rockwool ? Instead of the strips?
It won't work as well. You could sheet it AND do the strips, but the strips serve a purpose. The are a rain screen that promotes drying behind the siding. A flat layer of sheathing won't provide a channel for liquid water to move through. It also won't provide a path for air to flow though and remove water vapor.
Very informative video, thanks
How does the water behind the siding drain with horizontal straps?
Excellent. Two questions: What about dB reduction without the inner insulation? Looks like that some of the screws used for the exterior strips are not flushed, not being a problem for the final siding?
@Oaklejant - Answer to your first question - sound transmission happens through the air and the materials in the assemblies (plywood, framing, windows, etc.). This house is extremely air-tight (0.05 ach50), and having the sound absorption layer (rock wool) on the outside of the wood framing (sheathing, studs, etc.) is a HUGE benefit. This helps reduce sound so much better than having it in the cavities because it is controlling sound travel through the air and through the material (vibration, etc.). The cavity insulation would supplement the exterior insulation, but most of the work is being done by the exterior.
Answer to your second question. IOn all other jobs, we countersink all screws. On this job, the framing/siding crew (same crew) decided to risk it, and NOT countersink any of the screws. In the case where there was conflict, they made the adjustments. Turned out that less than 5% of the screws were in conflict with the siding. So, it required very little adjustment.
Thank you for sharing your process. Would you share a name or link of the particular vented starter and end flashing used in the assembly?
Cor-a-Vent SV-5
Is that type of system strong enough to take a stone/brick veneer... traditional setup: Paper/Ply/lath/mortar/veneer? Or is this more setup for fiber-cement/manufactured sidings to install directly to the 3/4 furring? If no, what would be needed to make the strips strong enough to handle veneer
Yes, you would attach brick ties to firing strips, still leaving a 1” gap
Why are the batten strips on the roof diagonal? Would this work for stucco?
They are diagonal as a 3 way compromise to attach to the rafters or joists (instead of perpendicular to them) AND vent upward (instead of blocked) AND to be a screw base for vertically oriented metal roofing panels.
I have CMU wall... finding a tapcon screw that long is going to be painful. At least every place is a stud.
ifs-300 ramset?
What's the trick to attaching continuous external rock wool to a steel framed building? What's the recommended way to fasten?
Rockwool has a guide for several substrates including steel framing. I'd look that up. It's only a couple page pdf.
Hi Chris. Great share. Did you use any membrane/WRB on this project with tis insulation approach? What siding/cladding will you be using?
We used a liquid applied WRB, Homero. Check out the video, “Liquid Applied Air and Vapor Barrier (a.k.a. WRB) - Poly Wall® Blue Barrier™ - ua-cam.com/video/VG-837UQLJM/v-deo.html
Great video! How do you handle the added roof thickness caused by the insulation plus stringers? Do you use wider drip edge flashing?
Yes, all of the flashings are made and trims selected to accommodate the thick insulation.
What’s the pitch of the roof? It looks low slope, and if so I’m curious what membrane you used for water and vapor management
Check out his video titled “Roof overhangs with continuous exterior insulation”.
Why do you need to be careful about not having only exterior insulation and no cavity insulation?
So how much do all those 7 inch screws cost??
What about rain during the installation process? Does it damp the rockwool?
Rockwool is unaffected by water. It will just dry out.
In reference to the four control layers identified where does "acoustic" fit in or is it an additional requirement based on environment?
Rockwool does a pretty good job of it already
The airtightness (0.05 ach50) and the continuous exterior stone wool insulation make this a VERY quiet assembly and structure.
Great details!
How far down does it go on the walls? Did you cover the outer band joist? Did you go down onto the foundation?
Thank you! This house has a slab-on-grade foundation, and we wrapped the thickened edge with insulation and continued it under the slab. Here is another video showing how we built it. ua-cam.com/video/Gjz4xPvLYJg/v-deo.html Let me know if you have any other questions about it.
For a basement or crawlspace foundation, we continue the insulation down to the footer. Sometimes, we will install insulation under the basement or crawlspace slab, and we will always install a continuous layer of insulation at the perimeter, where the slab meets the below-grade wall. This helps control heat loss, but mostly it's there to structurally isolate the slab, to allow expansion and contraction. Because it is below grade, and the walls are insulated, the thermal control is not as critical for the slab, as it is for the walls.
@@LGSquared
Thanks for the quick response this is interesting stuff
Can i ask, your supplier of Mfg for the long screws? We need self tapping through our external rockwool and into steel truss and steel wall framing.
Nice project Sir.
@David Bruce, we have been using #14, DP1 pancake head fasteners, by Triangle Fasteners, in both wood and metal frame construction, for years. They have a distributer near us, and they are all over the southern and eastern US, plus Washington State. Here's a link to the fastener on their site. www.trianglefastener.com/Products/CONCEALOR-Pancake-Head-Screws
@@LGSquared Thank you Chris. I have a new build with a concrete firewall wall seperating a duplex. What would be my best way to maintain continuous insulation on roof? It maybe an engineer question but i wonder if i could pour the wall, until under the roof deck and place rigid foam and then carry on the pour. Poking the foam through the rebar. Ive seen commercial cantilever decks with a foam insert. It was a Halfen Kit. Thanks for your assistance.
10,000 screws at 1/4 inch makes about 4.5sqft of thermal bridge. Is that good or bad or the best you could ask for?
It's the best you can do. Stainless steel screws would perform better, but no one makes any long enough.
Also, you can screw 1 screw every 16 inches of linear furring for lightweight cladding, which he's going to use here, so he's put more screws than is necessary. Overkill isn't always better. Rockwool has an install guide that gives screw placement for various thicknesses and cladding weights. Look it up before you decide on a screw pattern.
Just so I understand, you just laid those furring strip just right on top of the roof and wall insulation?
Justin, we installed long roofing screws through the furring strips @ 12” and 18” o.c. In to the wall and roof framing. This holds the insulation in place, and the strips become the substrate for the cladding.
@@LGSquared dumb question but if those screws are going through the air control layer to get to the structure, do those penetrations result in air leakage?
@@tubulartuber The screw that caused the hole also plugged it very tightly. The blower door test results of 0.05 ach50 proved that they did not create leakage.
Great video, thanks.
Can your explain your comment at 14:26 about being very careful only having insulation on the outside with none in the cavity? That's the way we do warm deck roofs in the UK, which is the preferred method as it avoids interstitial damp (condensation at the 'dew point'), because with the insulation outside, the timbers are the same temperature as the inside of the building.
I want to do this on the outside of my own timber siding (existing) house and am hoping just to take the cedar off, add breathable membrane onto the old OSB sheathing, then the Rockwool (3 or 4 inches), screw some wood battons/strips into the OSB (possibly into the structural wooden studs that behind too) and then nail the cedar boads externally onto those battons. Cor-a-vent top and bottom for insect free flow. But no insulation in the stud cavity.
Does that sound OK?
Many thanks.
Yeah... I'm wanting clarity as well. My initial reaction is that he saying to make sure the material you use is intended for outside use, and if you run out, to not supplement with interior insulation? But is he also saying that if the house has bat insulation and you decide to also install exterior insulation that it could cause problems?
What brand were your roofing screws?
Joshua, we've been using SENTRY PLUS FIVE Low Slope Roofing Screws from Triangle Fasteners
@@LGSquared Thank you
LOVE IT!! Would love to have you here in Texas. I'm in zone 2 climate, I believe in central Texas...What would be the cost difference with labor and materials with putting all the insulation outside vs doing both (external and interior)? (I know that the perfect wall would outperform the other of course). I'm planning on building a small house.
This would be grossss overkill for zone two.it would be the biggest waste of unrecoupable money ever
I wouldn't do the same R value, just the appropriate amount for my zone, but on the exterior..
@@MrsLilLady86 you would be wasting money. in texas they tax based on the outside dimensions. that exterior insulation could end up saving you $10 a year in energy but costing you $100 a year in extra taxes
@@MrsLilLady86 read this
"More information on optimal wall insulation
I decided to look into John Brooks’ question of whether thicker wall foam makes sense in Florida. It turns out that doubling the thickness of the wall foam from R-10 to R-20 would save only $20 per year.
I discussed the issue with Danny Parker, a senior researcher at the Florida Solar Energy Center. Using EnergyGauge software, Parker calculated the savings for a 1,600-square foot single-story slab-on-grade house in Tampa, Florida.
He assumed that the house had fairly good specs, roughly along the lines of the house I described above. He assumed that ducts were inside the thermal envelope, the house had 3 ACH @ 50 Pascals, the windows were U-0.30 with a SHGC of 0.30, and the thermostat is set at 77°F in summer and 68°F in winter. He assumed that electricity costs $0.15 per kWh - higher than the current retail rate there of $0.12 per kWh. (Assuming a higher electricity rate tends to exaggerate the value of increasing insulation thickness.)
If the house has 2 inches of rigid foam (R-10) on the walls, the heating and cooling costs [Later note: should be "total household energy use" - see discussion below] will be $1,794 per year. If the wall insulation were doubled to R-20, these costs go down only $20, to $1,774 per year.
Is it worth it to double the thickness of the foam to save $20? Well, it depends. You could also save the same $20 by buying a photovoltaic (PV) array costing $857; that 114-watt PV array would produce about 166 kWh per year, valued at about $20. So, if you can double the foam thickness on a 1,600-square-foot house for $857 or less, the foam insulation will cost less than PV. If doubling the foam thickness costs more than $857, then PV is cheaper."
www.greenbuildingadvisor.com/article/hot-climate-design
@@jl9678 THANKS! I love greenbuilderadvisor.com...Have done a TON of research, but the property tax aspect never crossed my mind which is double here vs other places. Definitely would prefer PV. Thanks for taking the time to point me to proven research! This is the article that made me want to consider doing 2" exterior in the first place...www.energyvanguard.com/blog/going-beyond-2x4-walls-warm-climate
👍😊
Its okay to take the camera off your face and focus on the thing you are talking about.
A bit on the nose but yes, I agree.
Omg , blah, blah, blah. I want a four layer turkey club , with no vapors, hold the thermal controls and the condensation, extra mayo, salt and pepper, stud. Toasted , no r value necessary.
Rockwool is 3x as expensive vs rigid foam board. Dum dum dum.
and what % of the total home construction cost is that?
@@rsmith02what % is it of the gdp of Istanbul? Bc that’s just as relevant