A cure for thermal bridging

We have utilized a number of strategies to combat thermal bridging, the heat loss/transfer that occurs through the connection between conditioned and un-conditioned space by framing lumber.
A relatively new product that we have recently utilized is the ZIP R-Sheathing from Huber Wood the maker of Advantech floor/wall/roof sheathing.
ZIP R-Sheathing combines the popular ZIP System sheathing and continuous foam insulation available in 1" which includes 1/2" R-3.3 foam, and 1-1/2" which includes 1" R-6.6 foam.
Some advantages of the ZIP R-Sheathing is a one step installation of wall sheathing and foam envelope insulation, tight to weather walls as soon as the proprietary "ZIP" tape has been installed on the seams, and a reasonable balance of cost to build and energy efficiency.
We will definitely use the ZIP R-Sheathing again on upcoming projects and recommend it as a consideration for your future new home construction project.

 

 

 

 

Another new product that we have recently utilized for the fist time is "ZIP system Liquid Flash". Liquid flash as the name implies is a liquid flashing material for sealing sheathing seams and preparing window and door openings. It is applied with a caulk gun and plastic spreader. The applied product is very tough and durable and looks to be an improvement to some previously widely used weather management techniques. Wear rubber gloves when applying liquid flash!

 

 

 

Blower Door Test Update #2

A second blower door test was recently conducted on our current new home construction project. This test was done after the completion of insulation installation to ensure that we had sealed the shell adequately.

Our initial test result was 1.89 ACH/50 prior to air sealing and insulation completion. The second test result was 1.62ACH/50.

My first reaction was of disappointment having utilized hundreds of dollars of spray foam and a bit of my time sealing every inside sheathing seam, panel edge and penetration. This was in addition to the insulation contractors efforts which were substantial.

A smoke generator utilized during the test showed that the weak links in the air tightness of this structure are the double hung windows, doors, and zero clearance fireplace flue and combustion air supply.
There is nothing that can be done about the windows (other than utilizing much more expensive euro windows and avoiding double hung windows (we have utilized Marvin windows which are very good windows). The doors should get better with the permanent hardware and corner pads installed which will be done after we paint. There is nothing that can be done to further seal the fireplace.

A final blower test will be done after drywall installation and the permanent door hardware and corner pads have been installed.

My expectations are for some additional but modest improvement on the final test result and as I think about things I have made the following conclusions:

• The ZIP sheathing with ZIP taped seams do a pretty good job at sealing the shell and probably do not require further air sealing on the interior side
• The 1" DOW foam that is applied to the exterior with seams taped helps air tightness as well
• The Protecto Triple Guard sill seal is more effective than traditional sill seal products to seal the foundation wall/sill plate joint
• The cost to upgrade windows and decision to forgo the fireplace in an attempt to achieve a test result of less than 1.0ACH/50 is probably something that many homeowners are not willing to do given the significant added cost of the windows and lifestyle choice of having a fireplace 
• Our test result of 1.62ACH/50 (and maybe a bit better after our upcoming final test) represents a very well air sealed home which will be very efficient to heat for its occupants.

Update on Blower Door Testing

I had previously written about Blower Door Testing to measure how well a completed home is air sealed (which is now a requirement in some of the communities that we build new homes in as a condition to receiving a certificate of occupancy).
Recently, we performed a blower door test on a new house that we are building as soon as the house was tight to weather (but prior to the insulation being installed) to help us determine how we could better air seal the building shell while it is still accessible.
This particular home includes the popular "ZIP" wall and roof sheathing and has all seams properly taped. It also has 1" DOW Tuff -R polyiso foam board applied to the outside of the sheathing with all seams taped as well.
The windows and door perimeters were foam sealed, but no other wall sealing efforts had been completed prior to the testing.

Our test results were 1.89 ACH at 50 Pascals. Not too bad, but, we have a pretty strict final target established of 1.0 ACH/50 that we would like to achieve.
The test results have determined the need to air seal 38 square inches of leakage to achieve our target goals.
As the test was being conducted we utilized an inferred camera to identify temperature changes in the building shell which could be caused by air movement. When we found these areas, we used a smoke generating device to check if it was indeed air movement causing the differential, and if so, made a paint mark to identify the need to air seal that area.
We will conduct another blower door test after completing air sealing and insulation installation to see how we did.
So far we have sealed all identified areas as indicated by our test, and went ahead and sealed the inside sheathing seams, top and bottom plates, gable rafters, and around window and door headers and studs which had not indicate leakage, but are areas that we would typically seal anyway.

I will follow up with the results of the next blower door test after it has been completed.