Insulation for basement shop

[Michael Ginsberg]

My soon to be shop which is now bone-dry due to a trench-sump pump system, I think needs to be insulated before I finish with the sheetrock. I was planning on putting a plastic vapor barier on the walls before the studs. I have a choice between pink or purple foam (which needs to be cut to 16 inches), or conventional fiberglass. The basement does not get very cold (or hot). The shop space is 30' x 30', Which insulation would you suggest, and why? Perhaps skip it altogether. Also, the shop will be ducted with heat and AC when needed and will have a dehumidifier.
Thanks for the suggestions.

[Thomas Bank]

I wouldn't use fiberglass in a basement - too much potential for mold to grow in it even with the vapor barrier. I'd stick with rigid foam and another layer of plastic over the rigid foam and studs before the sheetrock. That will keep any humidity in the basement from getting into the wall as well.

And you want a closed cell foam to further limit any chance of moisture in the wall. Not quite sure what the purple foam is - around here I see pink or blue. But ask for closed cell and you should be ok.

[Jim Andrew]

Closed cell styrofoam doesn't absorb moisture, so it is the vapor barrier. You didn't mention what kind of walls your basement is built of, but too bad you have to use studs, you will use up some space. Your foam will glue directly to concrete, if you use the proper glue, careful of construction adhesive, as it disolves foam.

[Michael Ginsberg]

Thanks guys. I want to use sheetrock to give it a painted finished look. The walls are poured concrete. The purple foam is thicker than the other colors. I am also wondering what R-value I need. Do I rip the foam on the table saw to width, or make several passes with a knife? What adhesive do you suggest?

[Jim Matthews]

This is my idea (http://www.finehomebuilding.com/how-to/video/cutting-rigid-insulation.aspx) for cutting rigid foam board...

I stole it from FHB, so now it's MY idea. This really works.
You need a curved taping knife, the thickness of the steel and curved profile make this work so well.

[Gary Pennington]

We're in Maine, near the coast so a little north of you. Part of our basement is my shop, in the winter it's usually 50 degrees for most of the winter and very dry. I had to turn on the humidifier a few weeks after turning off the dehumidifier from the summer. This fall we had the rim joists insulated with spray foam by an insulation contractor. It's made a phenomenal difference in shop comfort, the temp has hovered around 60- 62 all winter and there's been minimal need for humidification. I try to keep the humidity in the 30-40% range year round. Past years the humidifier has run all winter on high speed, this winter I ran it on low and it had no problem keeping up.
We have a perimeter roughly 180 feet long, the cost was $860. I had to give them 3 feet clear around the entire perimeter and cover everything. I also removed the existing fiberglass but they disposed of it for me. I believe that was the best $860 I've spent in quite some time.

[Craig Michael]

1 1/2" foam would be fine. Get the ones that have the grooved edges so they seal well. Don't use plastic between that and the studs, the foam is a moisture barrier and having a second isn't a good idea. Use pressure treated for the bottom sill of your walls and use a foam sill sealer under it to keep it off the concrete. Before you put up anything, check the outside walls and seal up any air gaps with cans of foam. Also make sure you don't close up any silcock shutoffs, etc. And check the insulation in the rim joists and make sure that is sound, fix it if not.

What will really make the space feel much warming is using a product like dri core on the floor. It works well.

[Thomas Bank]

Closed cell styrofoam doesn't absorb moisture, so it is the vapor barrier.

The issue with adding vapor barriers on either side of the foam is that you typically do not get a full seal along the studs and then get moisture travel around the insulation. Vapor barriers on either side of the foam is possibly overkill. But I'd certainly want it on the concrete wall side and another layer under the sheetrock is cheap insurance.

For cutting foam, score it with a utility knife and snap it just like you do with sheetrock. Trying to cut it with a tablesaw is going to result in particles of it everywhere - particularly because it will cling to everything by static electricity! :)

[Jim Falsetti]

Building Science Digest has an excellent writeup on insulating basement walls here (http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements). As others have noted, fiberglass is not recommended. Also, it doesn't appear a separate plastic vapor barrier is recommended.

If you contact the manufacturer of the foam boards they will most likely recommend a suitable glue product for their material.

Jim

[Will Winder]

I used rigid foam up against the foundation, framed over that, then special ordered some "Stone Wool" insulation at the big box store instead of fiberglass.

[Dan Hintz]

I DryLok the walls/floor, then put rigid foam over the top.

[Jim Andrew]

Your building center should know what adhesive works, but be sure to read the instructions, because some sales people just don't have a clue.

[Craig Michael]

I used rigid foam up against the foundation, framed over that, then special ordered some "Stone Wool" insulation at the big box store instead of fiberglass.

Why would you insulate between the studs? The rigid serves several purposes, it's a vapor barrier, it's very good insulation with a high R value, air seal, etc. If you do 1 1/2" or 2" rigid, that is plenty of insulation and since the basement is below grade it's even better. Putting anything between the studs is a waste and will make no difference at all.

[Will Winder]

Why would you insulate between the studs? The rigid serves several purposes, it's a vapor barrier, it's very good insulation with a high R value, air seal, etc. If you do 1 1/2" or 2" rigid, that is plenty of insulation and since the basement is below grade it's even better. Putting anything between the studs is a waste and will make no difference at all.

I don't claim to be an expert, but from my research it seemed like no two people do basement insulation the same way. If it wasn't a shop I would have used thick foam and no framing. For my shop I liked the idea of doubling up two types of insulation, with thin XPS excess moisture can slowly get out and shouldn't bother the stone wool.

I only left a 1" gap between the wall and the framing and decided to put some rigid foam in the gap. Then I read about the fire concerns regarding XPS since I was using OSB instead of drywall so I added the fire resistant stone wool. Maybe next time I'll drop the XPS and just use the stone wool (cheaper, easier, and lets me build the wall thinner).

The building science document here (http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems) seems to suggest the way I went as an option:

Walls with 3.5 inches of extruded polystyrene (XPS) and no
vapor barrier performed the best in this analysis. However,
walls with 0.75 inches of extruded polystyrene and 3.5 inches of
fiberglass batt insulation in the cavity would perform well as
long as interior humidity was controlled below 50 percent
during the summer. Increasing the extruded polystyrene to 1.0
or 1.5 inches would improve performance even with higher
interior relative humidity during the summer months.

[Doug McClentic]

Vapor barriersshould only be put on the warm side of insulation. This is because as moisturemoves through the wall from warm tocold it condenses and will damage insulation. It is true that CLOSED cell foaminsulation will act as a vapor barrier but you have to have an air tight seal aroundthe foam to make that happen. The ideas of attaching it to the concrete walland then framing inside of it are good. This will create a complete thermal break between the source of the cold and your shop. You would still have to seal around allthe edges etc. to make to completethe vapor barrier. Open cell foam will not be able to be used as a vaporbarrier.

In a basement situation I would not use typical drywall / gypsum board. It is amold magnet and will be very tough to keep the humidity low enough to preventmold growth especially in a closed area like the walls against concrete. Iwould use mold resistant drywall instead. Make sure to pressure treated wood atall contact points with concrete and insulate a couple feet around the perimeterof the floor at the rim joists.
.

[Mike De Luca]

No two people have the same method on basement insulation. I've been researching it for two years...

This is bar-none the best article I've found on the subject:

http://www.buildingscience.com/documents/information-sheets/basement-insulation

I plan on using the closed cell spray foam method.

229073

Read the discussion on convected air, condensation, and mold potential.

Hope this helps.

BTW... I wanted to use Dry-Lok but the experts abandon it, and any other paint-on product, out of hand...

[phil harold]

We Have a Winner!!!!
here is another way to do it, too

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_004c/0901b8038004cb8e.pdf?filepath=styrofoam/pdfs/noreg/179-07873.pdf&fromPage=GetDoc




This is bar-none the best article I've found on the subject:

http://www.buildingscience.com/documents/information-sheets/basement-insulation (http://www.buildingscience.com/documents/digests/bsd-012-moisture-control-for-new-residential-buildings)

I plan on using the closed cell spray foam method.

229073

Read the discussion on convected air, condensation, and mold potential.

Hope this helps.

BTW... I wanted to use Dry-Lok but the experts abandon it, and any other paint-on product, out of hand...

[Peter Perrello]

I had a professional spray closed cell foam in my 32 x 52 basement shop. It's incredibly warm and dry now.
When I removed the 20 year old fiberglass blanket I found some spots where there was mold.

[Carl Beckett]

No two people have the same method on basement insulation. I've been researching it for two years...

This is bar-none the best article I've found on the subject:

http://www.buildingscience.com/documents/information-sheets/basement-insulation (http://www.buildingscience.com/documents/digests/bsd-012-moisture-control-for-new-residential-buildings)

I plan on using the closed cell spray foam method.

229073

Read the discussion on convected air, condensation, and mold potential.

Hope this helps.

BTW... I wanted to use Dry-Lok but the experts abandon it, and any other paint-on product, out of hand...

I did a basement and very much like this same article (and another DOE article). Spent a LOT of time researching it, and learned that some common practices are a BAD idea, depending on your environment.

Take some time to read some of the references here - most likely will change your approach. Trapping air pockets can be a problem (so vapor shields must be carefully considered and put on the right side of the temperature gradient). Its not always obvious to the untrained eye.

I do like the idea of spray foam directly on to the concrete wall. It attaches to the surface and is closed cell, so prevents any air pocket where moisture could get in and grow mold (remember concrete is porous so moisture can come from the outside as well). I have seen some DIY kits for this but havent talked to anyone that has used them.

[Michael Ginsberg]

Guys, I am svery confused about all this...
It seem s that some of you are suggesting that I put the rigid foam directly on the concrete wall uninterupted, and then the 2 x 4 studs on the faom, then the sheetrock. I am not sure if I am understanding this right. How do the studs get attached to the concrete walls? Are you suggesting I glue the faom to the concrete wall and then glue the studs to the foam, then screw the mold resistant sheetrock to the studs? How do the stus get anchored to the actual concrete wall to support the weight of the cabinets?
You are saying that if I go with the closed cell faom, skip the plastic sheathing that I bought altogether... thanks for clarification.

[David Gutierrez]

The diagram above is suggesting "SPRAY FOAM" not rigid foam boards. the concrete in basement walls is porus and wicks moisture in from the outside. the foam sprayed directly on the concrete effectively seals the concrete walls from wicking moisture to the inside. the wall studs would be attached to plates top and bottom as any wall would be constructed. the negative is this system takes up a bit more space.

some one above sugested Drylock paint on walls and floor prior to wall construction that is a good solution because it will seal the concrete from the main source of huimidity in a basement which is the coming from the concrete.

[Michael W. Clark]

Guys, I am svery confused about all this...
It seem s that some of you are suggesting that I put the rigid foam directly on the concrete wall uninterupted, and then the 2 x 4 studs on the faom, then the sheetrock. I am not sure if I am understanding this right. How do the studs get attached to the concrete walls? Are you suggesting I glue the faom to the concrete wall and then glue the studs to the foam, then screw the mold resistant sheetrock to the studs? How do the stus get anchored to the actual concrete wall to support the weight of the cabinets?
You are saying that if I go with the closed cell faom, skip the plastic sheathing that I bought altogether... thanks for clarification.

I didn't use the foam on my finished basement, sounds like I am in the minority. My basement has a walk-out so part of it is above grade. All the walls are poured concrete. The outside portion below grade is sealed from the outside (some kind of black tar stuff). 1/2"thick foil-backed foam was already in place on the wall portions above grade. It was installed with some type of Hilti fastener with a washer. All the builders told me to frame with wood studs, insulate with fiberglass, kraft face insulation. No plastic barrier on the inside because it would trap moisture and cause a mold problem. They wanted to walls to breath in case there was an issue. I also asked the inspector about the construction method, and he confirmed. It may be area specific, not sure, but I haven't had any problems. This is the way all the basements here are finished if you buy new from the builder. If you are not sealed from the outside, probably a totally different story. I would put some type of moisture barrier on the inside, but not directly on top of the concrete, it will trap moisture and sweat.

Regarding your framing, the bottom plate (pressure treated) would be anchored to the floor. The top plate would be nailed to the bottom of your floor joists running perpendicular to your wall.

If your floor joists are parallel, you can install sleepers between the first joist and sill plate (pressure treated 2x that your joist and band board sit on). I laid my sleepers flat and face nailed them into the first floor joist, then used an impact driver and deck screws to attach them to the sill plate. Then all you do is face nail your wall top plate to the bottom face of the sleepers. I put my sleepers on a maximum of 24" centers, mostly 16".

If your first parallel floor joist is very close to the wall, you can take a 2x and nail or screw it flush to the bottom of the first joist. The 2x would need to be wide enough to cover the gap between the first joist and front of the wall, and catch the top of the wall top plate. I prefer the sleepers, but this technique is also very strong and stable. You can add some stiffeners between the first and second floor joist if you are concerned with the bottom of the first floor joist flexing.

My inspector told me I had to make sure there were no gaps between the studs and the wall for every 10'. Also no gaps behind the top plate and the next floor up. This is to reduce the propagation of a fire. I had to use insulation (compressed fiberglass), drywall, or fire-retardant spray foam ($$) to fill in any gaps. I used standard drywall in most of the basement, except for the bathroom where I used the mold resistant stuff, and the ceiling over the workshop where I used 5/8" fire rated sheetrock. My workshop is finished with 1/2" OSB on top of the studs, slick side out. I attached it with lots of Liquid Nails, and finish nails to help hold it and to help me find studs later. Heavy stuff, I attach it to a stud, and lighter stuff gets a hanger in the OSB.

Mike

[Thomas Bank]

It may be area specific, not sure, but I haven't had any problems.

You don't say what area you are in - that would help with the discussion somewhat. And have you opened up the wall at all to see if there are any problems? Or just that from inside the basement no problems have come through the wall? I'd be willing to wager that if you opened up the wall you'll find mold in the fiberglass unless you are in a fairly dry area.

[Michael Ginsberg]

Thomas,
I am in CT.
My concrete walls are bare, untreated, dry and uninsulated. I am starting from scratch.
The basement used to be VERY WET with a high water table the water came up through the lolly columns like a stream.... The basement now is bone dry due to a new trenched waterproofing system. I am going to use a dehumidifier in the humid summer months.



You don't say what area you are in - that would help with the discussion somewhat. And have you opened up the wall at all to see if there are any problems? Or just that from inside the basement no problems have come through the wall? I'd be willing to wager that if you opened up the wall you'll find mold in the fiberglass unless you are in a fairly dry area.

[Michael W. Clark]

I am in the Cincinnati area. We have good site drainage and there was no water or moisture problems before finishing the basement. We do have the drain setup as shown in the sketches that drains out the back of the property. The bare concrete walls never had any moisture or condensation issues. The only place I noticed condensation was on a egress window beside the walk-out door. It was due to leaking air around the perimiter. I sealed that inside and out before finishing. I have not opened the walls, its been finished for a couple of years now. The space has always had some HVAC. I installed an additional return and three additional supply registers when finishing. This was at the direction of the builder and original HVAC installer.

Mike


Mike

[Michael W. Clark]

Thomas,
I am in CT.
My concrete walls are bare, untreated, dry and uninsulated. I am starting from scratch.
The basement used to be VERY WET with a high water table the water came up through the lolly columns like a stream.... The basement now is bone dry due to a new trenched waterproofing system. I am going to use a dehumidifier in the humid summer months.

Michael, Sounds like you may have a different situation than mine, but you may have made a big improvement with the waterproofing system. If you have any doubts, the foam and/or dryloc like was mentioned previously may give you some piece of mind. I think the comments I made about wall framing would still apply. I built my walls in 12' sections. You have to take into account the floor being un-even to get the height. I had to cut every stud. The first section is the most difficult, then you plumb and square off of that one. For me, square was not as important as plumb, but I tried for both, the best I could.
Mike

[Dan Rude]

229291I'm just finishing up this type of project. My first room I did with 1" foam, built a stud wall and put another 1" between the studs. Started connecting the vertical studs to the wall using 4 in tapcons. This worked but my drill bit was too short and was a pain to line up the studs. I then changed methods in my new shop area, put 2" foam on the wall and 2x4 studs flat on the wall covered in drywall. I used 5" tapcons. Couldn't find a long enough hammer bit though, but I found a SDS bit that was long enough. The problem is it kept slipping in my 3 jaw chuck in my PC hammer drill. Then my wonderful wife on our 19th Anniversary while touring my toy store Menards, I saw a 7/8" Bosch SDS rotary on clearance. She told me to buy it :D, best move I made, night and day difference from the Hammer drill. So with a 10" SDS bit I can go through the stud and the foam and block. I saw flat studs in the FWW tools and shops addition from last year. This works if you are going to surface mount your electric boxes. I also did a 2 2X6 rails to the wall around the top part to hang cabinets and shelves. I’ll post a couple of pictures later after I take them. I will say, I started with fiberglass and when I pulled it out to do some work, I found the wall wet from condensation. It also didn’t seal. This was shown when I had an energy audit done it showed the leaking. Couldn't afford the spray foam for the rim joist. So I'm doing this by cutting the foam gluing and foaming around the edges. Best tool for the 2" foam has been a Menards Tool Shop insulation cutter:http://www.menards.com/main/tools-hardware/hand-tools/cutting-tools/insulation-cutter/p-1465876-c-9123.htm.

[phil harold]

Dow make a s product 1.5" thick routed out to take 1x3 furring strips
nice easy system, used it a few times
http://building.dow.com/na/en/products/insulation/wallmate.htm

[Michael W. Clark]

All, please don't take this the wrong way, and I mean it with all due respect.

This is just my way of thinking and I am sure there are things you could do to compensate, but I would not put my studs flat (long side parallel) to the wall. Its difficult, if not impossible, to run wiring behind the wall covering, and you don't have as much wood to go into when hanging heavy items. If you are worried about vapor barrier, you can't go through into concrete or you will comprimise the barrier.

If you did put the studs flat to the wall, I would seriously consider renting a Hilti gun and attaching with these fasteners versus all the tapcons. The tapcons will be expensive and it will take much longer. You'll definitely want the SDS if you do the tapcons. I bought a 1/2" hammer drill for tapcons to attach the bottom plates to the floor. It was a major pain. The bit would wear and the tapcons were nearly impossible to drive, they would break off or the head would strip (I had the hex head vs. the phillips head). I ended up using concrete nails and swinging a hammer with a vengence. I used to frame houses and the cut nails were standard for slab houses. If you can swing a hammer, you'll get a work-out and get finished quicker. If you rent the Hilti, you can use it for the bottom plates as well.

Mike

[Thomas Bank]

My concrete walls are bare, untreated, dry and uninsulated. I am starting from scratch.
The basement used to be VERY WET with a high water table the water came up through the lolly columns like a stream.... The basement now is bone dry due to a new trenched waterproofing system. I am going to use a dehumidifier in the humid summer months.

Simple fact is that concrete absorbs moisture - the reason that pressure treated lumber is required by code for sill plates. Without a moisture barrer between concrete and insulation - or an insulation that won't absorb moisture, such as closed cell foam - you're going to get moisture transferred to the insulation and subsequently get mold. It may not transfer through the drywall, but it will be there and may end up being a problem at a later date.

[Michael Ginsberg]

Thomas, Here is the plan...
I have put up a plastic vapor barrier sealed with caulk. I put up 2 inch blue foam insulation in between each stud. I plan on using moisture resistant sheetrock. The floor is bone dry and has been painted with UGL one part epoxy paint. I also have a dehumidifier as well. I think I should be good!!




Simple fact is that concrete absorbs moisture - the reason that pressure treated lumber is required by code for sill plates. Without a moisture barrer between concrete and insulation - or an insulation that won't absorb moisture, such as closed cell foam - you're going to get moisture transferred to the insulation and subsequently get mold. It may not transfer through the drywall, but it will be there and may end up being a problem at a later date.

[Thomas Bank]

I'm sorry - I actually got the Michaels mixed up there. I had originally been referring to Michael Clark's suggestion not to use a vapor barrier when I was saying about concrete absorbing moisture, but then ended up quoting your post. Sorry for any confusion.

[phil harold]

more building science articles to help you understand
http://www.buildingscience.com/documents/reports/rr-0309-renovating-your-basment
http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems
http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements/files/bsd-103_understanding-basements.pdf