The
Optimum Basement Wall
Solutions to the Wet Blanket
Basement Problem
We’ve made significant advances in water management.
Customers no longer accept that musty old basement smell.
Adapting to Change!
The Optimum Basement Wall
Today’s New Home Buyer:
•Expect their basements to be warm, comfortable and dry. •Do not accept mildew, mould and other odors.
•Want to finish their basements on their timeline.
The Optimum Basement Wall
Basements Built to the Current OBC:
•Builders are frustrated as homes built to the current OBC are very susceptible to mould and moisture issues.
• It is a real challenge to explain this to customers.
•Building Officials are frustrated because the builder has followed the OBC.
• But their phone keeps ringing.
•TARION faces a warranty challenge:
• How to deal with customer complaints for an item they can’t warrant.
•Builders and Industry Stakeholders are looking for a solution.
• Builders frequently tell customers to wait before finishing their basement.
The Optimum Basement Wall
The Definition of Insanity:
Continuing to do something over and over again and expecting a different result!
• As an industry we know basements are not working. The OBC does not address moisture migration within the concrete wall. • Over the years I have ripped open many insulated basement
walls and found that the majority of them had mould. • So we decided to build a better basement wall.
• I asked my CBO Leon Bach to work directly with me to ensure that my new wall system would be accepted.
The Optimum Basement Wall
The 4 Principles of the Optimum Basement Wall!
Limit the ability for water to enter the wall.
Use of materials that won’t trap moisture.
Change the location of the Air Barrier.
STEP 1:
Limit the ability for water to enter the wall.
Inward Bound Vapour diffusion.
• Moisture moves from wet to dry and from warm to cold.
• During the summer months, moisture in the concrete wall will try to flow from the outside of the concrete wall into your drier, conditioned basement.
• The 6ml poly traps the vapour which condenses on the
surface of the poly as there is no place for the vapour to go. So customers see moisture on the poly... And your (our) phone starts to ring.
• Our first step was limiting the opportunity for moisture to enter the foundation wall.
Limit the ability for water to
enter the foundation wall.
1. Damp proofing (Tar) applied to exterior of wall. (Limits wicking from surrounding soil).
2. DELTA®-MS Membrane applied to exterior of the wall. (Keeps bulk water away from foundation wall).
3. Cold joint between foundation and footing is caulked. (Keeps bulk water from slipping under foundation wall).
4. Footing Drainage. (Big ‘O’ connects to sump pit system to limit excessive water accumulation under basement floor).
5. DELTA®-FOOTING BARRIER is applied to the top of footing. (Limits wicking from wet footing).
The Optimum Basement Wall
DELTA®-FOOTING BARRIER:
• Capillary break between the footing and the foundation wall. • Significantly reduces wicking
from footing into foundation wall.
• Less wicking = dryer foundation wall.
• Permeance 0.8 Perms
• ASTM E96-05, Proc. A Test
Delta Membrane And Damp Proofing (Tar):
• Tar provides a capillary break between the footing and the surrounding soil.
• Significantly reduces wicking into foundation wall.
• Bulk water is managed away from the foundation by the Delta membrane.
The Optimum Basement Wall
NOTE:
• Tar application behind the Delta Membrane is not required by the Manufacturer. • Optimum Basement Wall recommends the tar application as an additional layer of
STEP 2:
Use of materials that won’t trap moisture.
Outward Bound Vapour Diffusion.
• During the winter months, humid air in the home is migrating
toward the exterior concrete walls where it will cool and condense. • If it is cold enough the migrating vapour will freeze on the
house-wrap and you don’t know it until the customer calls about water on their basement floor.
• We decided to work with ROXUL® to develop an insulation
product (COMFORTBOARD™ IS) and the Better Basement Wall
System that would not hold on to the migrating vapour and had mould resistant properties.
• Once we understood the COMFORTBOARD™ IS properties, we
decided to see if we would be able to eliminate the house-wrap against the foundation wall.
Use of Materials that won’t trap moisture.
1. Header wrap is extended over the basement wall top plate.
2. House wrap installed next to the foundation. R6 ROXUL® COMFORTBOARD™ IS installed over the house wrap.
3. Stud wall is built against the
COMFORTBOARD™ IS with a slight gap for straightening of wall. (Note that a PT bottom plate is used). R14 ROXUL® COMFORTBATT® installed in the stud wall.
4. 6ml Poly Vapour Barrier applied as per OBC. 5. 6ml Poly under bottom plate is lapped over top
of the vapour barrier.
6. Compacted Granular Sub Base limits moisture wicking into the concrete basement floor.
The Optimum Basement Wall
1. HEADER WRAP
2. MOISTURE BARRIER / ROXUL® COMFORTBOARD™ IS
3. ROXUL®COMFORTBATT®
4. 6ml POLY VAPOUR BARRIER
5. 6ml POLY UNDER BOTTOM PLATE
R6 ROXUL COMFORTBOARD™ IS installation.
The Optimum Basement Wall
15
NOTE: Installation can be done before the basement slab is poured and before framing.
Are there concerns with installing ROXUL®
COMFORTBOARD™ IS to top of footing?
When we used ROXUL® on the exterior of the foundation it was often soaked with water. Will the same issue happen on the inside?
It should not because it’s exposure to water will be very different.
1. ROXUL® can be used as a moisture barrier because it won’t hold water against the studs.
2. ROXUL® will not wick up from the footing.
• The loose cellular structure of ROXUL® COMFORTBOARD™ IS limits wicking action (unlike concrete which acts like a sponge), so it does not pull water
upwards against gravity.
• In addition we’ve designed a relatively “Dry” wall, with controls to limit inward and outward bound vapour diffusion, so there will be less moisture entering
COMFORTBATT®
R14 @ 24” O.C.
• CAN/ULC-S702-97
R-20 Basement Solution Next steps:
Look at the removal of the house-wrap.
A problem area is penetrations of the rim joist
• The headers have a skim coat of foam applied after all mechanical penetrations are completed.
• This acts as an air sealant and improves the warmth of the inside surface temp.
• DOW Froth-Pak™ is code compliant as a sealant.
• CCMC 13447-L
• R22 ROXUL® COMFORTBATT®
installed in front of foam provides a
Bodycote Report on Protection of Foam Plastics:
ROXUL
®is an acceptable option (Classification B Rating)
COMMENTS AND CONCLUSIONS
Dow Chemical Canada Inc. submitted the mineral fibre batt/polyurethane foam plastic system for testing to determine if it would meet the requirements of Clause
9.10.16.10.(1)(c) and Clause 3.1.5.11.(2)(e) of the 1997 Ontario Building Code and Clauses 9.10.17.10.(1)(c) and 3.1.5.12.(2)(e) of the 2005 National Building Code of Canada, Division B. The requirement is that the protective cover/thermal barrier must meet the requirements of Classification B when tested in accordance with CAN4-S124. (OBC harmonized with the National Building Code on these references in the 2012 OBC).
The 5.5 inch thick mineral fibre batt insulation identified as Roxul Flexibatt R21.5 (Now
rebranded as COMFORTBATT®R22), used as a protective covering for the Froth-Pak™
spray-in-place polyurethane sealant, qualifies for a Classification A rating based on an average temperature rise of less than 140 C° and individual temperature rise less than 180 C° at the 15 minute mark of the test. The 5.5" thick mineral fibre batt insulation would therefore also meet the requirements of Classifications B, C and D.
The Trouble with Poly
• The vapour barrier was not air sealed and did not prevent moisture migrating into the basement wall.
• PROBLEM: You don’t know there is an issue until you have water on the
basement floor and the client is calling to complain.
• We decided to limit the opportunity for moisture to enter the insulated wall. • We had already determined to use
products that would not hold moisture.
STEP 3:
Change the location of the Air Barrier!
Continuous Air Barrier
• The OBC now requires a Continuous Air Barrier.
• Many builders are putting a house wrap against the concrete then installing the insulation.
2013 wall revision from meeting with Dr. John Straube
NOTES:
• House wrap against concrete wall is removed.
• Air Barrier moves to the warm side of the insulation.
• COMFORTBOARD™ IS extends to top of the footing. • Poly to be completely air
sealed using applicable tape. • Acoustical Sealant under the
bottom plate, or Acrylic Sealant between slab and bottom plate is critical.
• Header Wrap goes over the front of the insulated wall.
• Air / Vapour barrier is then installed over top of the insulation.
• The ROXUL® does not hold water against the studs, but the 6ml poly
does.
• There is no place for the vapour to escape. • Client thinks their basement is leaking.
The Optimum Basement Wall
25
• Here you can see the mould on the face of the stud. • The customer is not happy because they see the mould.
The Optimum Basement Wall
• Summer time humidity and a hot sun “cooks” the concrete, forcing moisture through the wall where it hits the cooler poly and condenses. • The vapour barrier traps water in the insulation and limits the ability for
the wall to dry.
• Excess moisture in the wall will lead to mould.
The Optimum Basement Wall
STEP 4:
Allow drying paths for moisture migration.
What if we change the function of the Air Barrier?
The Optimum Basement Wall
Smart MemBrain™ replaces 6ml poly on the top 1/3 to ½ of the
The Optimum Basement Wall
MemBrain™ complies with:
• CCMC’s Technical Guide for Vapour Barrier 07264
• CCMC’s Technical Guide for Air Barrier Systems for Exterior Walls of Low-Rise Buildings 07272
MemBrain™ can serve as an alternative solution that will achieve at least the minimum level of performance for vapour barriers and air barrier systems with respect to condensation control required in:
The limitations in the use of MemBrain™ as the
designated vapour barrier:
The Optimum Basement Wall
• The MemBrain™ film shall be protected from direct ultraviolet (UV) exposure and covered with interior gypsum wallboard within seven days;
• Detailing around window should limit the exposure of the MemBrain™ to
sunlight, either by covering it, or using poly in the
Using the Optimum basement wall you can go from this
This is a retrofit of an existing home.
The Optimum Basement Wall
To this: A wall that dries to the inside during summer
time humidity events.
Detailing around
Window
The Optimum Basement Wall
• Easiest method is to go right over opening.
• Then use the smart poly to tie back in to the
window.
• Less cost and uses existing materials
already being used for the Optimum Basement Wall.
This design has been approved as an Alternative
Compliance under the OBC for use in St. Thomas, Central
The Optimum Basement Wall
• The Optimum Basement Wall is being studied in our Discovery Home for the next year by George Brown College.
• Our goal is to change the Ontario Building Code to recognize the need to control vapour migration.
The Optimum Basement Wall
The Optimum Basement Wall
CONCLUSION
Following the 4 basic principals of the Optimum Basement Wall,
we can construct walls that work.
Limit the ability for water to enter the wall.
Use of materials that won’t trap moisture.
Change the location of the Air Barrier.
