Using Low-E Reflective Insulation as a Capilliary Break
Friday, January 15th, 2010The job site was very busy today. We were framing the interior walls in the lower level, measuring the openings for the windows and sliding doors, and signing a Canadian passport application.
Providing a Capillary Break Under the Pressure Treated Bottom Plates
Moisture inside a house is bad because it creates an environment where mold can flourish. In houses that are very ‘leaky’, the moisture problem is somewhat reduced. On the other hand, it is exacerbated in a ‘tight’ house. There is an excellent presentation on GreenBuildingAdvisor.com entitled, ‘Got Mold? Energy Efficiency and Moisture Management‘ that was presented by Mike Guertin and Peter Yost on December 18, 2009. It is 63 minutes long and well worth watching.
Under our Durability Planning, our integrated project team completed a Durability Risk Evaluation Form that identified all moderate- and high-risk durability issues for the building enclosure. Then, we developed specific measures to address those issues. In addition, we identifed and incorprated indoor moisture control measures with our plans.
Given we have an immense amount of concrete in our house, we will have a huge potential pool of moisture in that concrete. Water can move through concrete into wood, hence building codes require pressure-treated wood wherever wood is in direct contact with concrete.
Water, however, can move through capilliary action through wood and other materails. Thus, having a pressure treated bottom plate that is resting on concrete will prevent the moisture in the concrete from rotting the bottom plate. The pressure treated bottom plate may allow the moisture to migrate through it to the stud walls, which may cause mold and rot.
Having a capilliary break between the bottom plate and the concrete prevents water from gaining access to the bottom plate. We are using a product called ‘Low-E Reflective Insulation‘, which is a reflective insulation and is made of two layers of aluminum foil with a closed cell foam in between (sometimes known as ‘foil-bubble-foil’). Bryan met Charlie Snow at West Coast Green in San Francisco on October 12, 2009, when they first discussed this project and how Low-E Reflective Insulation would provide significant benefits to increasing the energy performance of the house.
We are using Low-E Reflective Insulation in every instance where wood touches concrete. An additional benefit in our exterior walls will be to use the Low-E Reflective Insulation between the mud sill and the foundation. Low-E Reflective Insulation will provide a capilliary break for moisture and provide a tight seal so air cannot go through the wood and the concrete. This will make our house tighter and more energy efficient. Although we will have separate termite shields in place, the Low-E Reflective Insulation will provide another defensive barrier for termites.
The Low-E Reflective Reflective Insulation comes in rolls that are 48 inches wide and 125 feet long. Our framing team cut the Low-E Reflective Insulation into strips 5-1/2 and 3-1/2 inches wide so it could go under 2×6 and 2×4 plates.
Establishing the Window and Sliding Door Opening Dimensions
As we’re framing the lower level we are zeroing in on establishing the exact dimensions for our windows and sliding glass doors. Annie Rouse (Murray Window and Door) and Dave Edwards (Earth Bound Homes) walked through the house and reviewed the dimensions for each window and sliding glass door.
This task required an immense amount of attention to detail. Making an error with an aluminum frame and double pane glass will be expensive and look bad. Also, we pulled in Francisco, who is doing the actual framing on site, on several occasions so we’re all on the same page with how the windows and sliding doors will fit.
Signing a Canadian Passport Application (Guarantor)
Our friend, Mats Menhardt, is a Canadian citizen and requires a new passport (Canadian passports are only valid for five years). His mother, Trixi, brought his completed passport application to the job site for Bryan to review and sign.
That was easy.
Roll of Low-E Reflective Insulation (48 inches wide by 125 feet long).
Close up of the packaging.
Trimming the Low-E Insulation so it will go under the 2x6 plate. Trimming the insulation was easy and fast.
The Low-E Insulation is under the 2x6 pressure treated plate and it will provide a capilliary break and prevent moisture from moving from the concrete to the wood.
Without the capilliary break, water could move through the pressure treated bottom plate and cause mold and rot in the 2x6 studs.
Dave Edwards (left) with Annie Rouse (back) and Francisco (measuring). Trixi (right) is getting the passport application out for Bryan to sign.
Trixi, holding Mats' completed and signed Canadian passport application.
