In an effort to keep an article about thermal detailing at overhead doors exciting (which may prove to be an impossible task) let’s start off with 2 main points:
1. Unless you are completely familiar with ASHRAE 90.1 your overhead doors may not be in compliance with energy requirements.
2. Most (if not all) insulation detailing around overhead doors consists of a thermal bridge which defeats the point of having an insulated door in the first place.
If I haven’t piqued your interest at this point, stop reading. I can assure you that this article is only going to get more technical and boring from here. However if you are concerned with best practices and being ASHRAE compliant, you may want to keep reading.
Let’s start with item #1, why your overhead doors may not be in compliance with energy requirements. You may believe that adhering to ASHRAE requirements is only a matter of using an insulated overhead door when in fact the standard is based on air leakage.
Here is an excerpt from an article that can explain it better than I can: ASHRAE 90.1-2013 requires that air leakage for rolling doors shall be determined in accordance with the National Fenestration Rating Council NFRC 400 guidelines. Doors must be labeled and independently tested to meet a maximum air leakage rate of 0.4 cfm/ft2., which is even more stringent than IECC. Requirements in ASHRAE 90.1-2010 and 2013 are similar. (source: https://continuingeducation.bnpmedia.com/course.php?L=510&C=1539)
As contractors and designers that are building “ASHRAE compliant” buildings, the responsibility is placed on us to confirm that the overhead doors we are using on our projects have the documentation to prove that they meet the air leakage requirements and have the thermal resistance required based on the chosen compliance path. Note that air leakage requirements vary depending on whether your doors are glazed or not. For clarification please refer to your project architect or energy modeling consultant.
Moving on to item #2, chances are if you have designed or built an insulated concrete building the detailing around the overhead door has looked something like this:
Let’s reason on this for a moment. Per point #1 we need to ensure that the thermal resistance and air leakage rates are checked for maximum thermal efficiency. However the detailing around an insulated overhead door is incomplete meaning that even with those measures in place a huge thermal bridge is left.
How do we eliminate the thermal bridge? We would need to somehow return the insulation to the interior of the building and mount our thermally rated and non-air leaking overhead door on it. The detail would look something like this:
We call it OHLoc (OH for overhead); it’s the first of its kind thermal break specifically designed to maximize energy efficiency at overhead doors. The fact is that if you are not using OHLoc as part of your insulated concrete assembly you are leaving a large thermal gap in your insulated overhead doors. Keep in mind that cast in place OHLoc comes in 3 pieces, 2 for the jambs and 1 for the header.
Some might question why bother with this detail, why not leave it as it is? If you are going to leave this thermal bridge, it kind of defeats the purpose of having an insulated door. Also, for someone who is designing, building or investing in an insulated concrete building; do you really want your insulated system to be incomplete?
To find out how we can improve energy efficiency with your insulated concrete project, please get in touch. We are passionate about helping to maximize energy efficiency with insulated concrete buildings.