Should I use Tyvek or tar paper on basement walls?

Question

We are going to be redoing our basement which was done in the 60's and very cold. We have been told to apply Tyvek or tar paper to the walls, stud, then vapour barrier and drywall. We plan on using fiberglass batt insulation because of costs (we are retired and limited income). We would love to do the spray foam and not have to worry about all the vapour barrier and such but we are out of budget - Styrofoams seems like a lot of work by the time you have to cut each piece.

We are going to get some prices by contractors but want to do some work ourselves to keep costs down so of course the behind the scene work is what we want to do - i.e. studding (16 inch on centre and insulating and maybe installing the drywall but not taping and finishing). If we use tar paper, do we just overlap it or do we tape it much like you do the seams of Tyvek? Do we go right to the floor with the paper or, like with the insulation, do we keep it a foot off the ground? Any help, suggestions are greatly appreciated.

Answer 1

"Should I use Tyvek or tar paper on basement walls?"

Neither. No building paper or wrap against the foundation. Just use foam it is not really all that difficult to cut.

The best practice really is to use rigid foam against the foundation wall, then a framed (possibly insulated) wall with drywall and no vapour barrier.

Batt insulation in the framed wall is debatable. Green Building Advisor has articles that say it's not a good idea because it can absorb moisture, but others sources have no problems with it. If you do use it (I would if you are in a cold climate and don't have existing moisture problems in your basement), I personally prefer mineral wool over fiberglass.

Don't forget about the cavity above the wall in the joist spaces.

Trusted Sources (read them!)

• Built Wrong From the Start (Fine Homebuilding) [PDF]
• Basement Insulation for all climates (Building Science Corporation) [PDF]
• How To Insulate a Basement Wall (Green Building Advisor)

Good Luck!

Answer 2

The main concern with vapor barriers and fiberglass insulation is preventing condensation and trapped moisture in the insulation that could result in mold and mildew. The vapor barrier on the conditioned (heated) side of the wall is there to prevent warm moist air from passing into the insulation and condensing on the cooler side. If you install a vapor barrier on both sides, moisture can become trapped inside the insulation and result in mold/mildew.

Tar paper is water proof and could easily act like a second vapor barrier. When used on a roof, there are typically soffit and ridge vents to keep the underside of the roof dry, rather than trapping moisture in the attic. However, on your basement wall, there doesn't appear to be anything that would allow trapped moisture to escape.

Tyvek and other house wraps are different in that they block liquid water, but not water vapor in the air, from passing through. This allows the walls to breath and prevents trapped moisture.

Therefore, in your situation, a house wrap product is probably best to prevent damage from any moisture in the walls from getting absorbed by the insulation and wood framing. Where the framing meets the floor, I'd be tempted to use either a vapor barrier, a foam weather stripping (it comes in a roll and is the width of the framing), and/or pressure treated lumber with nails designed for pressure treated framing.

Answer 3

I've spent HOURS and HOURS on the Internet (actually days and days) investigating basement insulation techniques. If you don't agree with my method below, please take the following advice: DO NOT USE A VAPOR BARRIER on EITHER SIDE OF THE basement wall. I don't care what anyone advises. I've had builders recommend vapor barriers -----------------and I'm sorry to say, they may build a great house above the ground, they don't know what they are talking about when it comes to basements!!!!

I wouldn't insulate my NEXT basement this way, but this is what I did in 2006, one year after my NEW house was built. Seven years later my basement is dry and the walls are dry. (I use a dehumidifier in the warmer months as a precaution.)

1. 1/2 inch blue extruded polystyrene styrofoam (R-5) glued top to bottom of basement wall vertically and directly to walls with FOAMBOARD adhesive. Why 1/2 inch? It was on sale for a great price-----$8 per sheet in 2006.
2. Sealed joints with housewrap tape.
3. Overlapped 1/2 polystyrene with 2 inch WHITE expanded styrofoam (R-8) HORIZONTALLY with FOAMBOARD adhesive on the TOP half of the wall only. Why 2"? It was on sale for a better "great" price--about $9 a sheet in 2006.
4. Sealed joints with housewrap tape.
5. Installed 2" by 4" stud walls against the white styrofoam.
6. Installed 3 1/2 inches of Kraft paper backed fiberglass insulation (R-13) between studs and slashed the Kraft paper with a razorblade to allow any moisture trapped in wall to escape. (Do NOT use a vapor barrier on basement walls.)
7. Installed housewrap over the now fiberglass-insulated wall. The house wrap allows moisture through--------------but prevents relatively warmer basement air from contacting relatively colder wall.
8. Applied regular 1/2 inch drywall over the housewrapped wall.
9. Painted wall with an eggshell paint. (not semigloss---------remember, you don't want to trap any moisture behind the wall.)

What would I do differently today? At my house-----------high on a hill and NO threat of standing water against the foundation--------------I'd still install the additional fiberglass insulation in a 2 by 4 basement wall. But, my first option would be to use spray foam between the studs------depending on the cost of the spray foam. If costs were prohibitive, I'd

1. attach 2 inch blue styrofoam directly to wall top to bottom with FOAMBOARD adhesive
2. seal joints with housewrap tape
3. install 2" by 4" stud wall.
4. install 3 1/2 inches of batt insulation MINUS the Kraft paper
5. still install housewrap over the stud wall
6. use MOISTURE RESISTANT drywall.
7. still use paint with an EGGSHELL finish.

I live in the THUMB part of Michigan (Michigan is shaped like a glove?) and the winters are pretty active. I use propane to heat my house (2 by 6 inch exterior walls with R-21 fiberglass insulation and I have about 22" of blown-in insulation in the attic). For people who use propane in the northern states, you know that heating an 1800 square foot house would cost a pretty penny to insulate.

I have yet to spend more than $950 per year to heat my 1800 square foot house with propane. (I have a set-back thermostat, double pane windows, insulated window treatments, and most of my windows face south.) The $950 also includes heating my water with a propane hot water heater. Insulating the basement reduced my heating bill a shade over 10% or about $100 per year. Today, I'm saving even more because I paid $1.29/gallon for propane in 2006 and today --2013) I'm paying about $1.79/gallon.

EXPENSES FOR INSULATION

$360 on 1/2" foamboard $198 on 2" foamboard $20 on housewrap tape
$40 on housewrap $40 on FOAMBOARD adhesive

$658 not including 2 by 4's and drywall.

I've been saving about $100+ per year on my heating bills since insulating the basement. You can do the rest of the math.