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What To Do With Those Bare Walls

Here you can see the final foam layer; under here is the radiant barrier, and behind that is the air space. In the stud bay to the right, you can see a foam block spacer above the outlet.

You’d probably rather be cutting tenons or curves on the bandsaw, but something you’re overlooking is right in front of you.  Those bare shop walls.  Whether it’s concrete block or un-insulated wood framing, it’s letting in the hot summer radiant energy and letting out your expensive heat in the winter.  And, if it’s wood framing with empty stud bays, there is nothing stopping your loud tool noise from annoying the neighbors or the people inside your house.

If you could get your shop envelope under control, you’d solve so many problems.  There are days when I know I can’t go in the shop because it’s way too hot or cold.  And as you know, shop time can be a rare commodity.  So walk out into your shop and take a look—what can you do to stop air infiltration, block and absorb noise, block the sun’s radiant heat (depending on your climate), and keep in your shop’s warm air in the winter?

To avoid the overwhelm feeling, just map out your wall and roof layers (gyp. board, plywood, insulation, sealant strategy, etc.), and then just do a little bit at a time.  I do a few stud bays several days a week.  It’s a permanent investment so each one you do will pay you back session after session!

My Overall Wall Strategy

My wall strategy has to accomplish two things:

  • Sound Attenuation

o         Keep sound from escaping the shop to the neighbors

o         Absorb sound to keep those echoes to a minimum for your sanity

  • Temperature Control

o         Keep the summer heat out

o         Keep the winter heat in

I have a 2×4 framed wall with a stucco exterior.  You may have a 2×4 wall but with a different siding material, such as wood shingles or clapboard siding.  Or, you may have an exterior wall in your basement made of concrete.

If you do have a concrete wall, then you don’t have to worry as much about sound escaping, but it will bounce back to you and annoy your ears.  Also, you’ll benefit from insulation to keep the shop’s heat inside.

Keep in mind what your conditions are.  What’s your weather like?  Dry most of the time?  Humid?  Or a mix of both?  If you have enough humidity, then you need to be careful of moisture migration, vapor barriers, and condensation to avoid mold issues.  Do some research; there are plenty of forums.  But be careful—everyone has an opinion and they all don’t agree, so be aware that your situation may be somewhat unique.

Sealing all gaps has 3 benefits: Temperature control, Sound control, and Insect control.

The Walls…The Walls…The Walls are on Fire!!

If you have a wood framed wall, the firebreak should be maintained in place.  This is the horizontal 2×4 that divides a stud bay roughly in half.  Speaking of fire, you should do things to reduce the chance of fire while you’re inside the walls.  Check your electrical connections, and test each outlet to see if there any mis-wired or loose connections with a tester.

Also, you might as well brush on a fire retardant chemical on the studs to make it harder for a fire to ignite.  I bought a few gallons of this stuff which I’ll be brushing on each stud bay before it gets sealed up.

Prior to the installation of any insulation, I spray-misted fire retardant on all the studs. This helps the wood to be less combustible. When I tested a sample 2x4 piece sprayed with this, I let it dry and then tried to ignite. It basically self-extinguished. This chemical is why the wood studs in these photos appear to be discolored.

Finally, to complete your fire protection enhancements, seal up any stud and top plate utility penetrations with fire-caulk.  This caulk is more money than plain ol’ acrylic caulk, but you’ll only do this once.  There are several types of fire caulking available depending on exactly where you’re applying it.  There is one type that is meant for sealing wall seams, which I’ll be applying to the fire breaks and top plates of each stud bay.  Then, there is the intumescent type, which is designed for actual penetrations by wires and pipes.  This stuff expands when heated, so if a plastic pipe burns away during a fire, the intumescent material expands to fill the hole and blocks the fire from getting through.

To prevent fire from jumping from one bay to the other, where I have an electrical outlet I’ll use a fire sealant to seal up the stud bay.  If I’m applying drywall over the studs, I’ll run beads of fire sealant on the studs before screwing the drywall in place.

Fire caulking is what I used at the fire blocking (horizontal framing members) and in bays where there is an electrical outlet or junction box. The adhesive you see to the left is great for sticking the foam spacer blocks to the tar paper, and also the radiant barrier foam sheets to the spacers.

Do You Remember the Bugs After You Squish Them?

You may as well take care of your insect problem too.  I’m sealing up each and every stud bay, along the sill plate and top plate.  Basically every nook and cranny is being sealed up completely.  This will help prevent insects from getting in your shop, starve any fire for oxygen, prevent sound from transmitting as easily, and prevent thermal transfer by minimizing convection and air movement in the cavity.  As you can see, sealing up your stud bays has a ton of benefits.

You can review your structural as well.  If you want, you can have a structural engineer take a look at your walls to see if there are any deficiencies that need correcting.  I may look at adding sheets of plywood in some areas for added shear strength, and adding more metal clips to beef up the joints between rafters and the top plate.

To increase the amount of insulation (R-value) you can fit in the wall, consider furring it out to make it a thicker wall.  For my walls, which are 2×4 to start with, I’m adding a 2×2 to make a total of 2×6.  Now I’ll be able to fit at least R-19, and even more if I use foam.

The sill plate is important to seal; this way you prevent air infiltration and insects from getting into your shop or behind the drywall. By obsessively sealing every gap in your shop, you get to control the entry and exit points.

 

This caulking takes a bit of time but it’s really satisfying imagining all those bugs frustrated that they can’t get in for some shop time!

Wall Layers

Write down exactly what you want your wall to do for you.  For mine, I want it to prevent radiant heat from entering the wall cavity during the summer, keep out the cold and drafts, absorb sound on the inside, prevent sound transmission to the outside, keep out bugs, and be able to support some cabinets and shelves.

Starting with the above goals, I came up with a layering system.  I divided my walls into two categories:

  • Exterior Walls
  • Interior Demising Wall (between my house and garage)

For the exterior wall, temperature control is the most important thing to me, and for the interior wall sound control is the most important.

Before I go into the layers I chose, I’ll mention what my climate is.  I live in Southern California, inland.  The weather is similar to desert weather; hot in the summer, and moderately cold in the winter.  Being CA we don’t have snow, but it can get slightly below freezing, maybe 25 deg. F.  Summer temperature can be 100 or 105 deg. F easily. The overall climate is fairly dry, with only occasional rain.

So, the following is the wall construction I came up with.  Yours will vary of course, since your wall construction and requirements are probably different to some degree.  I’ll discuss what I would do if I had a concrete wall below.

This cutaway view shows my planned wall layers for the exterior. Drawing this forced me to slow down and think about the best order of each layer and what was cost effective.

The following are my wall layers, from Outside to Inside, of an Exterior Wall:
  • Stucco Finish Coat and Scratch Coat

This is an existing layer that I don’t plan on removing.  It’s basically a 1” layer of concrete.  It holds and absorbs the sun’s radiant energy, the so generously gives it back to me.  This radiant energy needs to be reflected back outside, which I discuss below.

  • Tar Paper/ Building Paper, ship-lapped

This is another existing layer.  I don’t feel like ripping apart the exterior of my house right now, so I’ll leave it.  Any tears in this layer (and there are a few) I’ll seal up before I proceed.  Its function is to shed water that gets through the stucco layer.  It’s ship-lapped such that water can run down the wall without getting inside.

  • 1” Airspace

I need at least a ¾” air space (with 1”x1” foam block spacers) to support the radiant barrier’s function.  Since I want the radiant barrier to reflect the radiant heat from the stucco layer back outside, I want it  close to the stucco layer.  However, if you put foil side of the radiant barrier smack up against another surface, it just won’t work.

Since I have to have this airspace, I want to make sure to prevent air movement both to stop convective heat transfer and sound transmission.  That’s why I’m sealing around the edges of the stud bay and the radiant barrier foam sheet with caulking, isolating it.

  • 1” Rigid Foam Radiant Barrier, sealed airtight

They sell several different kinds of radiant barrier.  You can get the foil bubble-wrap type, rolls of foil, or foil-faced rigid foam sheets.  To me, I like the idea of the foam providing extra thermal conduction protection, and I can cut it to fit in a stud bay as well as easily caulk and seal around it.

  • 3” Rigid Foam, sealed with expanding foam between studs (in lieu of batt insulation)

After the radiant barrier foam, I want to fill the rest of the 2×6 stud cavity with more rigid foam, and use expanding spray foam to seal it up and completely fill the cavity.  This has the advantage of stopping air movement in the cavity, while being relatively immune to moisture that may get in there.  I’m a bit worried about fiberglass insulation getting moist and not being as effective.

I could also use a spray foam just by itself, but I don’t like the idea of burying all of my electrical wires in this stuff.  What if I had to get in there to fix something?  At least with rigid foam sheets I can remove them if I had to.

  • 5/8” Drywall with beads of construction adhesive separating the drywall from the studs

For sound transmission prevention, I want to acoustically isolate the drywall from the stud framing. This is so sound vibrations can’t pass from the drywall to the wall studs and on out to my neighbors.  So by absorbing the vibrations with beads of caulking, I effectively create a cushion to absorb the drywall’s vibrations.

I’ll put “squiggles” of caulk in the middle of each stud and let it dry.  On either side of each caulk squiggle, I’ll put a bead of fire sealant on either side of each stud.  This will isolate each stud bay.  Then I’ll carefully screw the drywall to the studs.  Yes, the vibrations can transmit via the screws, but it’s vastly better with the caulk beads than with full contact with the studs.  Thermal conduction is also slowed significantly as well.

  • 1/2” Sound Board

For sound absorption, I’ll sandwich this between the two gyp. board layers.  Keep in mind that you don’t want to expose a combustible wall surface to your shop if you don’t have to.  Drywall is a good layer to use to protect combustible layers such as the fibrous sound board, or foam insulation.

  • 1/2” Drywall with beads of caulk separating the two layers for a sound cushion

This will be fun…making caulk squiggles all over the wall…the whole wall. Should I spell a message?  Wanna help?  Now, the reason for the two different sizes of drywall is that I want different resonant frequencies in each layer for sound-proofing reasons.

Varying the layer thicknesses is way better than two of the same thickness layers.  Over this last layer I’ll put some primer, and maybe a layer of paint.  Later on I’ll do some decorative treatments, like three-dimensional sculpted walls and paint-fades for aesthetic appeal.  I’m weird like that.

  • Decorative, sculptural layer, w/ sound-absorbent properties if practical

For aesthetic purposes, I’ll add a non-structural, non-functional layer here.  I want a sweeping, three-dimensional shape.  You could also add fire-retardant cloth-covered sound board panels for sound absorption, or do a paint-fade effect, or hang wall sculptures.  Your cabinets can be designed to integrate the overall look.

Some other things you can do are add a soundboard layer, add mass-loaded vinyl for sound-proofing, or add plywood for extra shear strength.  If I was building my shop from scratch (I’ll be building my finishing outbuilding from scratch), I’d add exterior plywood instead of having just a lath-embedded stucco scratch coat and tar paper.  I’d also use a good quality housewrap.

This section view shows the wall between my house and workshop. Acoustical considerations are the main driver here, which is why I'm going through the trouble (oh, come on, it's fun!) of creating a second wall. Note the use of resilient channels on the innermost drywall layer. This acoustically separates it from the structure, but makes it inadvisable to attach heavy objects to this wall. But it's ok, the wall is along a walk path.

The following are my wall layers, in order from House side to Shop side, of the Interior Demising Wall:

 

  • 5/8” Type ‘X’ firecode drywall (existing) on the house side

This is an existing layer, part of the 1-hour fire wall that I don’t plan on removing; later on if I remodel the adjacent room I’ll seal all the stud bays and maybe add a second drywall layer to the house side and firecaulk any utility penetrations.

  • R-11 Batt Insulation (existing) in the stud cavities

This is another existing layer.  If I remodel the adjacent room, I’d like to replace the insulation with a better quality R-15 batt.

  • 3/4” Plywood or OSB shear wall (existing)

This layer is existing and serves to provide shear strength (prevent side-to-side sway motion of the house).  The structural engineer will indicate how much shear wall you’ll need for your house if you’re starting from scratch.  Another place you’ll find shear walls is on either side of the garage door, usually a pre-manufactured product such as Simpson Strong-Wall.

  • 5/8” Type ‘X’ firecode drywall (existing) with new radiant barrier foil applied

This is the final layer of the existing firewall, facing the inside of the shop.  I’ll be creating a second, non-structural wall independent of this wall.  I’ll just seal the hell out of this layer before starting the adjacent wall, separated by a 1” airspace.  This means I’ll have a fire wall that’ll do its job independent of the 2nd inside wall starting next.  I want a radiant barrier to protect the house from the shop if it happens to get really hot in there.  I don’t want that radiant heat to make its way into the house.

  • 1” Acoustical Airspace, sealed

This is the separation between the two walls for acoustical purposes.  By decoupling the two walls, sound will have a hard time making it from the shop to the house.  I may put a time capsule thing in there for the heck of it.  Any suggestions?

  • 5/8” Drywall with beads of caulk separating the drywall from the studs

The first layer of the inner wall.  This will be tricky to install since I won’t have access to it from the back.  So, I think I’ll make the wall on the ground and then raise it into position.  I’ll have think carefully about the order of operations here.  I’ll be sealing each stud bay prior to adding insulation also.

  • 2×4 Studs with Batt insulation, R-15

I don’t want to eat up too much room in the shop, so a 2×6 wall here would be excessive.  2×4 will be plenty to do the job I want it to.  When the shop is unconditioned (hot or cold), I don’t want this to transmit into the house so the insulation and these two walls will help quite a bit.

  • Soundboard layer with dry caulk beads as cushioning layer and thermal break

I’ll add a ½” layer of soundboard and seal it.  This will provide some sound absorption, and a tad bit of thermal insulation.  Again, I’ll use caulking to act as a cushion for vibrations and to provide a thermal break.  I’ll screw it to the studs after the caulking beads dry.  I’ll probably add a fresh bead of construction adhesive just to seal it better.

  • Resilient Channels supporting 5/8” drywall

For this interior demising wall I’m more concerned about acoustical performance than thermal performance.  So, I’ll use resilient channels to anchor the drywall to the soundboard.  These are horizontal channels with a cross-section shaped like a ”Z”. This way the drywall isn’t directly screwed to the soundboard.

The reason I don’t use construction adhesive here is that the sound board is fibrous and a bit fuzzy, so I don’t think it would stick very well.  Keep in mind that you don’t want to screw cabinets to any wall where you use resilient channels, or you short-circuit the sound path.  This is why I’m not using them on the other walls.  For this demising wall, I don’t want cabinets on this wall because it’s a walking path to go from the house to the side yard, and the loft will be above that.  Also, the 1 hour fire wall is the one on the other side of the 1” air space.

  • Decorative, sculptural layer, w/ sound-absorbent properties if practical

For aesthetic purposes, I’ll add a non-structural, non-functional layer here.  I want a sweeping, three-dimensional shape.  You could also add fire-retardant cloth-covered sound board panels for sound absorption, or do a paint-fade effect, or hang wall sculptures.  Your cabinets can be designed to integrate the overall look.

If I had a concrete wall, I’d consider using a radiant barrier on the inside to keep my winter heat in the shop, and prevent it from being absorbed by the concrete walls.  I’d probably use a product like Drylok to waterproof the concrete, then add furring strips to the concrete (with a moisture break like construction adhesive).  I’d research vapor barriers and see if it’s the right thing to do for my outside vs. inside temperature and humidity conditions.  Then, I’d probably use foam insulation (maybe spray foam) and then finally drywall or plywood on the innermost layer.  If you use plywood, you can screw cabinets to the wall more easily, or use French cleats.

A pack of 10 of these roof-rafter radiant barriers is about 50 bucks at Lowes. It comes with 10 48”x24” sheets. Actually, these are a bit wider than 24” so that they flex to fit within the bay.

WoodChip Tip: If you have a wood stud wall, when you add your foam sheet or drywall over the studs, mark where the studs occur either on the floor or ceiling.  Then, when your wall is fully drywalled, add thumbtacks near the ceiling or floor to indicate where the studs are.  You can paint them the same color as your wall.  Also, take a digital photo of the wall and maybe draw an elevation view with dimensions for future reference.

These are the spacer blocks being installed. This ensures that I have the appropriate air space between the stucco layer and the radiant barrier.

Why I Need a Radiant Barrier

The main reason I’m so motivated to get my shop temperature under control is the searing blasting heat during the summer.  During July, August, and September, it’s really impossible to do woodworking after lunch.  I start sweating right away as soon as I enter.  That’s no fun.  And it’s a colossal waste of valuable shop time.  This is why your shop envelope is an investment with a super-high return.

What happens in my case is the sun blasts on the stucco layer all morning and early afternoon.  This layer is about an inch of concrete.  Concrete absorbs this heat, but it takes several hours for this heat to make it through to the inside.  This is known as Time Lag.  For example, metal has an extremely short time lag, and concrete has a much longer delay.

During the early afternoon and evening, this absorbed energy in the concrete layer is re-radiated toward the workshop, making it feel like an oven from all sides.  What I want to do is reflect this radiant heat right back outside.  This is exactly what a radiant barrier does.

Behind each of these radiant barriers is a 1” air space.

Generally a radiant barrier is a foil-like surface.  It needs about a ¾” airspace in order to work.  The radiant barrier can face either direction and it still works.  For example, you can face the foil downwards on the underside of your roof and it’s going to do the same thing for you, which is keep the radiant heat from coming in.  You just need that airspace; don’t cram it up against another surface.

I want my radiant barrier to be right near the stucco layer, so the rest of the wall doesn’t get heated up by the re-radiated energy.  So, I’m putting the foil side of the rigid foam adjacent to the tar paper/ stucco layer, separated by a ¾” airspace.  I’m sealing this so that I get no air movement in order to enhance the thermal barrier of the airspace, and to help with sound-proofing.

Incidentally, for my roof, I found a product called Enerflex Radiant Barrier that I’ll be installing between the truss-bays.  I’ll fire spray the sheathing first, then seal all the sheathing seams with fire-caulk before installing the radiant barrier.  Don’t forget to leave a channel for airflow from your soffit or eave vents to your gable or ridge vents!

Each stud bay gets sealed, and then every electrical wire or piping penetration through the studs gets fire-caulked. I want to make sure that I minimize air convection within the air gap.

Here’s a Video on Radiant Barriers from Enerflex that you will find useful.

[youtube]http://www.youtube.com/watch?v=_kR3IBWOCjk&feature=channel_video_title[/youtube]

Overkill?

What?  Me?  Ok, I admit, what I’m doing here may seem nuts.  But to me it’s also fun.  Really.  The research is interesting to me, and then narrowing down my design is even more exciting.  Some of the things I’m doing here have a larger return on investment than others; the good news is you can decide what’s right for you.  And, don’t forget to run things by other experts.  I did; I went to forums with my proposed design and asked my HVAC co-conspirators plenty of questions.  Just because I have a P.E. license doesn’t mean I know everything.  I changed my design quite a bit from my original thoughts.

Don’t Neglect This

Once you’ve devised your best wall layering strategy, check with a contractor to see if what you’re about to construct is up to code, and just as important, won’t cause you moisture problems down the road.  There is plenty of debate on what to do about vapor barriers (which you Google around for and find tons of forum comments), but you must make sure that your climate conditions are compatible with how you are layering your walls.  If you totally seal a wall with a plastic vapor barrier layer, and your climate conditions combined with your indoor conditions cause condensation to form on the plastic, you could create a breeding ground for mold, especially if the area the condensation forms can’t dry out easily because it’s sealed.  How’s that for a run-on sentence?

Before You Do Anything

Prior to starting to seal up stud bays and insulating, there is some prep work that you need to do.  The first thing I did was take a shop vacuum brush attachment and clean out all the cobwebs and dust.  Then, you can use a compressed air nozzle to further clean it.  When it was super dry and hot out, I blasted the stud bays that were really dirty with a garden hose.  It dried out in less than a day, but I let it sit for a week just in case.  But now I know it’s clean.  That’s important so that the caulking sticks properly.  I want those stud bays to be truly sealed.  Otherwise you’ll get air movement inside, negating the insulating effects, and also sound can travel more easily.

This is how I applied the fire retardant. All studs are getting this treatment. When I do the roof rafter bay radiant barrier, I’ll be spraying the underside of the roof sheathing and the truss bays. Eventually my whole house will be treated as well.

The other thing you’ll want to do is seal every exterior penetration by electrical outlets, hose bibs, and conduit.  You can spray-foam around electrical outlets, or smear caulking until it’s totally sealed.  Be careful of spray foaming around electrical wiring; turn it off and test it with a sniffer first.  Where I’m concerned about fire spread, I used intumescent fire caulk to seal.  Also, look for any exterior watershed or housewrap layer rips and tears; fix those while you have access.

WoodChip Tip: Prior to insulating and doing all the above craziness, really check your electrical layout.  Is that what you want?  If you want any extra outlets in the future, run the proper gauge wire now, and simply provide an outlet box and cover plate for now.  This way all you have to do is hook it up to a breaker or junction box, and connect the outlet at the other end.

If you’re working on your shop’s exterior envelope, read these two posts:

Some Additional Photos of my Insulation Installation

I found a cheese knife is really helpful at cutting foam insulation. I used a straightedge as a guide to cut clean lines flush.

I got a bit ambitious and started installing the roof radiant barriers. I discovered that even on a mildly sunny day, the underside of this sheathing can get to 100 deg. F. Prior to installing these, I spray-misted the roof sheathing and trusses with fire retardant.

This is what I want to prevent. As my roof tiles heat up during the day, they re-radiate this to the roof sheathing. As I put my hand up to the OSB, I can feel the heat. When you have over 500 sq. feet of roof it can really make the shop unbearable. I start beading sweat immediately when I enter the shop in the summer.

Foam spacer blocks being glued to the wall. The blue fire sealant to the left was smeared on a rip in the tar paper. I want this bay to be protected from unnecessary water intrusion.

Yum!

Random penguin.

To maximize the amount of radiant barrier foil surface in the 1” air space, you’ll want to get creative about cutting around obstructions. The lazy way would’ve been to cut the radiant foam short and fill these areas with spray foam, but instead I’ll carefully seal around the electrical boxes and conduit (seen in the lower part of the stud bay) and maintain the air space.

For more guidance in assembling your Woodshop Design, click on the Starting? Go Here! category and read those first.

Connect with me on Facebook, and follow me on Twitter for more ninja tips to Optimize Your Woodshop!

 

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5 Responses to “What To Do With Those Bare Walls”

  1. Andrew says:

    Thanks for the highly detailed information. This is a great post, and finally, I have some sense of direction with finishing my basement wall. Thanks for the start.

  2. Informative post but how did you get the penguin to come over to your house. :)

  3. Chris says:

    Bobby, you sure do do things to the max! VERY impressive!

    You say you installed the foil clad foam with the foil facing the exterior, but in some pictures, it appears the foil is facing in… is that just an illusion?

    Chris

    • Bobby says:

      Thanks, Chris! Things take longer when you go deep into doing it right, but as you know it’s well worth it. I enjoy the process too.

      Yeah, the rigid foam sheets (1″ thick) come with both sides foil-faced. I put the side with the blue printed words facing toward the shop because I want the “clean” foil side facing the stucco and 1″ air space. That 1″ cavity with the radiant barrier is the focus of this whole thing–to reflect that nasty heat from the stucco layer back outside.

      The side with the printed words will be directly covered with regular 2″ or 3″ white foam sheets, then spray-foam will be used around the edges to seal it air tight. The photo under the subheading “Why I need a Radiant Barrier” shows one of the stud bays with this foam installed. The goal is to reduce air movement since that will hurt the R-value of any insulation, and it’s good for sound attenuation too.

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