Subject: Basement Utility Room Fix Up – Use of Rigid Insulation
Region: Upstate NY (northeast). Cold climate.
Building Type: 1987 Wood frame construction with a Concrete block basement, below grade. One exterior wall has foil-faced isulation. The other, which is under the edge of the garage slab) is uninsulated. The basement floor is a floating slab.
Room Layout: The dimensions are about 16×8, and the room contains a gas hot water tank and furnace on one side and a washer and dryer on the other.
Room Atmosphere: Winter the room is dry and does not seem unusually cold or drafty. However, During the summer, the room is damp and there is a little moisture damage on a few items that have sat down there a couple years. Note: The room has no door and is open to the rest of the basement (already finished some years ago by a contractor) where there is a dehumidifier.
Background: I checked with a guy at Lowes (ok i admit it), and he said to put 4 mil plastic over the existing insulation and block walls, and then frame over that. He also advised using a pressure treated bottom plate where the wall meets the concrete floor. This seemed simple enough and fit with my desire to get this project done without undue expense or time.
After I tacked up the 4 mil plastic and started framing, I began to worry that I might be making the moisture problem even worse down there. Since moisture does come in during the summer, I wondered how it would get out in the winter through the 4 mil plastic. So….I found a recent FHB article on the use of polystyrene (styrofome) rigid insulation for use in basements as a ‘vapor diffuser’. The author confirmed my suspicions: vapor barriers are now OUT for this kind of application. But his approach requires 2′ of insulation on the walls (plus framing) and 1′ on the floor (plus 1′ of plywood).
Issues:
1. On the walls, can I nix the framing and just use insulation + furring strips + drywall? That would be about 3′ thick. If I follow the article and frame over 2″ of rigid insulation, my walls will be 6″ thick.
2. On the floor, which is relatively dry, wilI be ok if I just throw some I/O carpeting on some sections and call it a day? Putting 2″ of insulation in the floor–and then another 1′ of plywood– would be a nightmare. I’d have to cut around the furnace and pay a plumber to disconnect and re-connect the hot water heater. This seems like overkill just to fix up a laundry room in the basement.
Thanks for your suggestions, Guys.
Reed
Replies
I would start by calling your local building inspector or department and fond out what they require/accept and go from there. Basement finishes are one of those things that the jury is still out on as far as figuring out the best way to finish. I don't the any of the code councils have resolved the issue.
As for dehumidifiers. They often don't perform well during the wet spring period in basements that are not well heated because it is too cool in the room. And of course lack of ventilation compounds the problem. I would suggest you get a return air from your furnace into the room as well as heat. Often these rooms have a register cut into the plenem to supply heat, but no return. The return should come off the plenem above and pull air off the floor to be most effective.
You probably have more moisture coming off your slab then you realize. Lay a piece of poly on the floor for a few days and see if the slab becomes damp underneath. A 4' square piece should do it.
Ok, Woodroe, good idea. ill check with the building guy, I know him anyway.
reed
My understanding is that there should NOT be a return anywhere there is combustion going on. Which is why basements have supply, but no return.Also, even though the door is left open, I recommend putting a louvre in the door. Someone could come along and close the door, or a draft could close it, etc.
>>My understanding is that there should NOT be a return anywhere there is combustion going on. Which is why basements have supply, but no return.General rule is within 10' of combustion.>>Also, even though the door is left open, I recommend putting a louvre in the door. Someone could come along and close the door, or a draft could close it, etc.Good point
Fighting Ignorance since 1967
It's taking way longer than we thought
"I would start by calling your local building inspector or department and fond out what they require/accept and go from there."..."I would never use a vapor barrier in a basement (4mil plastic)."...hence the problem with 'checking with the inspectors' as I've found--at least with basements--code typically goes against what you want to do in terms of 'best solution'.
Yeah, it takes codes decades sometimes to catch up with science.
Now, if I were cynical, I'd suggest that's because many of the folks who sit on the code writing boards are employed by large building materials manufacturers who are heavily invested in current technologies. But of course, I'm not a cynic.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I'm forced by local code and inspectors to put a vapor barrier on the inside of basement framing or firring...even when the reason I'm there is to tear out and re-do the moldy, rotten stuff behind the last vapor barrier installed.I get my VB inspected, then tear it off as soon as the inspector leaves.
A man after my own heart.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I've got a defiant renegade hidden beneath my calm, cool exterior. 8>{
You mean you're an anarchist?Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I'm not the antichrist...least I hope not.
Andy, I remember the article but forget a few of the details. How do you run wires with all that solid foam on the walls?Al Mollitor, Sharon MAhttp://moosehilljournal.blogspot.com/
Sorry Al, it's an Amish-only detail.
Simple - you build a stud wall in front of the foam. Or if you use furring strips, drop the wires down from above in conduit, and foam around it. I think the conduit is neccessary because it would be really difficult to ensure that wires remained the code required 1 1/4 in. from the back of the drywall otherwise.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Andy,
I'm definately a cynic. BUT, as luck would have it, our local building code is not only up to date, it actually makes some sense (miracles will never cease).
Apparently, there is a fire risk with the polystyrene. It is highly flamable. It also gives off toxic fumes when ignited.
Accordingly, the code allows polystyrene insulation against a basement wall but requires covering material with at least a 15 minute burn time (1/2 inch drywall, acording to the inspector). Thicker 5/8 inch drywall has a 40 minute burn time and is better.
The required covering material may be applied via a stud wall or furring strips against the polystyrene (similar to the FHB article).
I appreciate your help on this topic. This is a rapidly developing area of building science and, of course, FHB was right on top of it.
Reed
The problem with building codes not being up to date is that often inspectors aren't either. If you get one who is a stickler for adherence to the code, you may not have much choice but to follow the code. Fortunately, I haven't run in to one of those for years.
I would never use a vapor barrier in a basement (4mil plastic). I usually install 2" rigid then frame in front of that. There was an interesting article about this in FHB about a year ago (I think it was Andy Engel?). He installed rigid on the floors and the walls kind of incapsulating the concrete. It worked out well for him but he had the headroom to lose some floor and he had to rebuild the stairs.
Thanks MSA. Yeah that was the article I was referring to. It looked good and his approach seems logical given what I found out about vapor transfer in the Building Science Corporation site listed in the article.
But as you said, all that styrofoam takes up a sh**load of space.
Also in the Building Science website is a 'model home'. It shows the basment as having 2" rigid in the walls with furing strips and drywall over it...no wood frame.
So I was wondering if that would work.
Reed
Yes, you can use furing strips and then DW.In fact some one makes foam with channels in it for the furing strips. Forgot what the brand name is.I did one and used 1 5/8" metall stud wall in front of the foam. But I did that because the foundation wall leaned about 8".
Bill,I think I use the stuff you are referring to: Owens Corning Insulpink XPS--comes in 2'x8' sheets with recesses for 1x3 firring strips. You only loose 1.5" to insulation + 1/2" for sheetrock.I make my own 1x3 rips of plywood (1x3 pine is usually junk).Attached the same pic twice, oops!
Thanks, Basswood. Nice picture. I like the idea of loosing only 1.5" to the insulation and having the furring strips incorporated in the rigid so the total thickness (with DW) is only 2". That works.
Hopefully, the Lowes near me will have the INSULPINK in stock.
Reed
Let me know if you go with the InsulPink...I can offer a few tips on installing it.
"Let me know if you go with the InsulPink...I can offer a few tips on installing it."I'll take those tips, if you're still offering ....
On our Insulpink projects, the firring strips we used were 1x3's ripped out of 3/4" BC plywood. The firring strips were glued and screwed (with PL300 and tapcons). We apply the PL300 generously to the masonry in dabs, put a 2" rip of 3/4" XPS pressed into a bead of PL300 on floor at the base of the wall (this allows for a full 1x3 and an air gap below the firring at the floor--keeps wood and drywall up off the floor and provides a better nailer for base than a 1x2 at the bottom of the first course).Then run another bead of PL300 on top of the rip and press the first full 2x8' panel into the glue on top of the rip. Keep adding full panels & 1x3's on up the wall (more about the top panel later if you want the details). That is how we insulate a standard masonry wall. Plenty of PL300 and tapcons every 16" on the firring (I prefer the hex head tapcons--for the head I make a shallow countersink with a 1/2" spade bit). Also we use PL300 liberally when installing drywall to the XPS and firring.
Edited 9/6/2006 6:43 pm ET by basswood
Any suggestions on a granite block foundation? Its a very uneven surface. I'm leaning toward using 2x4 wall and spray foam insulation. Not sure whether the open cell or closed cell would be better. I know the cost of having a special insulation contractor is going to be a lot more than doing rigid foam myself, but I think the R-value will be significantly better.
2x4 wall will work well in your case. Your climate and the intended use of the basement can make a difference in deciding whether the extra R-value & cost of the Icynene, etc. are justified.If you want to frame and foamboard it yourself, here is an interesting approach for an 3" R-15 wall with thermal breaks: Use 2x2's for the frame with 1-1/2 XPS in the vertical stud spaces...Then run InsulPink horizonally with furring over the 2x2 frame. I have also done Insulpink over a 2x4 wall with R-13 fiberglass for a total wall R-value of 20.5.
Thanks for the info. Never thought of combining the two.
Ok, Bill. Thank you. You're the only one that has answered my question directly. Another poster suggested a beer fridge...hard to argue with that!
Ill look in the stores for the 'slotted' rigid foam and get started. I probably will not cover the floor unless I still have substantial moisture problems after doing the walls.
I may use flat 2x4's for the furring strips with a top and bottom plate, so I have something solid to nail into for shelves, etc.
If i'm way off on any of this, let me know. If not, thanks for the help.
Reed
Wow. That is the most organized post I've ever seen. Kudos my friend!
Justin Fink - FHB Editorial
Your Friendly Neighborhood Moderator
Thank you, Justin. High praise from an editor of FHB. Good magazine. I quoted it in my initial post, which was a bit long. I apologize.
I could have just asked, "in a below-grade basement in the northeast can I get away with 2" rigid + furring strips + drywall over a block-wall foundation"? But I rambled a little.
Anyway, the article I referred to my initial post was from FHB. I looked up the Building Science Corporation site quoted in the article.....there it was...NO VAPOR BARRIER. The BSC site also had a cold climate model home...it displayed a below-grade basement with no frame wall. Only 2" rigid, furring strips and drywall.
If this is ok, what should I use for the furring strips for strength, flat 2x4's? Plywood strips? Pine 1x3's?
And if I don't cover the floor, am I asking for trouble?
Reed
Let me refer to our resident basement expert, Andy Engel. Take it away Andy... (I sent him an email, stay tuned)...Justin Fink - FHB Editorial
Your Friendly Neighborhood Moderator
Just use a dehumidifier in the summer (Or keep your beer fridge down there!)
BTW, that's a very small room for a furnace, water heater and dryer.
If closed off from the rest of the hosue, the room isn';t big enough to safely run a typical water heater in, much less a furnace and dryer.
Be sure you're providing adequate combustion air (50 cu ft per 1,000 btu combined, or, if an opening is provided to the rest of the house 1 cu in free vent space per 1000 btu. (Free vent space = after subtracting for grill covers)
Fighting Ignorance since 1967
It's taking way longer than we thought
thx, rjw. the 'beer fridge' is a great idea. why didn't I think of that. lol
your point about the air exchanges is a good one. actually there is a door to the rest of the basement and it is always left open. so I think its ok.
as far as the drywall over the rigid foam and furring strips, I still havnt gotten an opinion. but i did check the building science corporation site on the net and they had a model home on there with a below-grade basement using 2" rigid + furring strips + drywall. so hopefull that'll be ok.
reed
1. On the walls, can I nix the framing and just use insulation + furring strips + drywall? That would be about 3' thick. If I follow the article and frame over 2" of rigid insulation, my walls will be 6" thick.
Have at it. Should be fine.
2. On the floor, which is relatively dry, wilI be ok if I just throw some I/O carpeting on some sections and call it a day? Putting 2" of insulation in the floor--and then another 1' of plywood-- would be a nightmare. I'd have to cut around the furnace and pay a plumber to disconnect and re-connect the hot water heater. This seems like overkill just to fix up a laundry room in the basement.
Here, you're making me nervous. Use 1 in. foam. Or use the dimpled plastic osb combo whose name escapes me now. Please don't lay carpet right down on the concrete. Cool concrete brings condensation to carpets which fosters dust mites which make me sneeze. A lot. Do that and I'll never visit your laundry room.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
" Or use the dimpled plastic osb combo whose name escapes me now."Dricore and Subflor.Also you can get the dimpled plastic from several sources. Delta-FL is one. BTW the local Lowes is now stocking Delta-FL.And HD has the Dricore.
Thanks, Bill. Which would you recommend, the Delta-Fl or the Dricore?
Reed
I have never used either one and have not had the need to look into the details of either.
"Here, you're making me nervous. Use 1 in. foam. Or use the dimpled plastic osb combo whose name escapes me now. Please don't lay carpet right down on the concrete. Cool concrete brings condensation to carpets which fosters dust mites which make me sneeze. A lot. Do that and I'll never visit your laundry room."
Ok, Andy. OSB/combo it is. My nose doesn't like dust mites either. Its a good compromise, and Ill just cut around the furnace and hot water heater to avoid all the associated plumbing costs.
Many thanks, guys, for the tips.
Reed